www.sciencemag.org/cgi/content/full/332/6028/439/DC1
Supporting Online Material for
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers
Alexey G. Sergeev and John F. Hartwig*
*To whom correspondence should be addressed. E-mail: [email protected]
Published 22 April 2011, Science 332, 439 (2010)
DOI: 10.1126/science.1200437
This PDF file includes:
Materials and Methods
SOM Text
Figs. S1 to S3
Tables S1 to S6
References
Supporting Online Material
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers Alexey G. Sergeev and John F. Hartwig*
Department of Chemistry, University of Illinois, 600 South Matthews Avenue, Urbana, Illinois 61801
Table of Contents:
1. Full References from the Main Text 3
2. General Experimental Details 3
3. Preparation of Aryl and Benzyl Ethers 5
4. Stability of the Ni(COD)2/PCy3 Catalyst Under the Conditions of Reductive
Cleavage of Aromatic C-O bonds 15
Figure S1. Attempted Hydrogenolysis of Diphenyl Ether Catalyzed
by Ni(COD)2/PCy3 15
Figure S2. Attempted Reductive Cleavage of Anisole with Triethylsilane
Catalyzed by Ni(COD)2/PCy3 16
5. Nickel-NHC Catalyzed Reductive Cleavage of Aryl and Benzyl Ethers with
Hydride Donors 18
Discussion 19
Table S1. Selected Results on the Effect of Ligand, Nickel and Hydride
Source and Base Amount on the Reductive Cleavage of Diphenyl Ether 21
Figure S3. Carbene Ligands Used in the Study 21
Table S2. Reductive Cleavage of Aryl and Benzyl Ethers with Hydride Donors 22
6. Nickel-NHC Catalyzed Selective Hydrogenolysis of Aryl and Benzyl Ethers 29
Competition Experiments 43
*To whom correspondence should be addressed. E-mail: [email protected]
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
2
Mercury Poisioning Experiments 45
Table S3. Selected Results on Effect of Ligand, Temperature and
Amount of Base on Hydrogenolysis of Diphenyl Ether 47
Table S4. Effect of Ligand, Nickel Source, Temperature, Amount of Base and
AlMe3 on Hydrogenolysis of 2-Methoxynaphthalene 47
Table S5. Control Experiments for Hydrogenolyisis of 2-Methoxynaphthalene 48
Table S6. Catalyst Stability Estimation in Hydrogenolysis of Methyl Aryl Ethers 48
7. NMR spectra 49
8. References 67
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
3
1. Full References from the Main Text
Ref. 20: B. T. Guan, S. K. Xiang, T. Wu, Z. P. Sun, B. Q. Wang, K. Q. Zhao, Z. J. Shi,
Chem. Comm., 1437 (2008).
Ref. 35: B. A. Ellsworth, W. Meng, M. Patel, R. N. Girotra, G. Wu, P. M. Sher, D. L.
Hagan, M. T. Obermeier, W. G. Humphreys, J. G. Robertson, A.Wang, S. Han, T.
L.Waldron, N. N. Morgan, J. M. Whaley, W. N. Washburn, Bioorg. Med. Chem. Lett. 18,
4770 (2008).
2. General Experimental Details
Equipment and methods
All air-sensitive manipulations were conducted under an inert atmosphere in a nitrogen-
filled Innovative Technology glovebox or by standard Schlenk technique under argon.
All glassware was heated in an oven and cooled in an inert atmosphere prior to use.
GC analyses were obtained on an Agilent 6890 Gas Chromatograph equipped with an HP-
5 25 m x 0.20 mm ID x 0.33 µm capillary column (Agilent) and an FID detector.
The following GC oven temperature programs were used: A) 100 °C hold for 3 min,
ramp 40 °C/min to a final temperature of 300 °C, and hold for 2.5 min; B) 80 °C, ramp
110 °C/min to a final temperature of 300 °C, and hold for 3.2 min; C) 35 °C hold for 2
min, ramp 45 °C/min to a final temperature of 300 °C, and hold for 2 min. Helium was
used as a carrier gas, with a constant column flow of 5.6 ml/min (program A and B) or
6.6 ml/min (program C). The injector temperature was held at 250 °C (program A) or 300
°C (program B and C).
GC-MS analyses were obtained on an Agilent 6890-N Gas Chromatograph equipped with
an HP-5 30 m × 0.25 mm × 0.25 µm capillary column (Agilent). The GC was directly
interfaced to an Agilent 5973 mass selective detector (EI, 70 eV). The following GC oven
temperature programs were used: A) 50 °C hold for 2 min, ramp 40 °C/min to a final
temperature of 300 °C, and hold for 2 min; B) 100 °C hold for 3 min, ramp 40 °C/min to
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
4
a final temperature of 300 °C, and hold for 2.5 min. Helium was used as a carrier gas,
with a constant column flow of 1 ml/min. The injector temperature was held constant at
250 °C.
NMR spectra were acquired on a 400 MHz Varian Unity instrument or on 500 MHz
Varian Unity or Inova instruments at the University of Illinois VOICE NMR facility.
Chemical shifts are reported in ppm relative to a peak of a residual protiated solvent
(CDCl3, δ 7.26 ppm for 1H and 77 ppm for 13C).
Flash column chromatography was performed on a Teledyne Isco CombiFlash Rf
automated chromatography system with RediSep Rf Gold normal-phase silica columns (40
and 80 g).
Analytical thin-layer chromatography (TLC) was performed using glass plates pre-coated
with silica gel (0.25 mm, 60 Å pore size) impregnated with a fluorescent indicator (254
nm). TLC plates were visualized by exposure to ultraviolet light (UV) and/or submersion
in aqueous potassium permanganate solution (KMnO4), followed by brief heating.
Elemental analyses were performed by the University of Illinois at Urbana-Champaign
Microanalysis Laboratory and by Robertson Microlit Laboratories, Inc. (Madison, NJ).
Solvents and reagents
Benzene, toluene, and tetrahydrofuran (THF) were degassed by purging with nitrogen for
45 min and purified using an Innovative Technology Pure Solv PS-400-6 solvent
purification system equipped with 1 m column with activated alumina. Anhydrous
dioxane, m-xylene and dimethylsulfoxide (DMSO) where purchased from Aldrich and
used as received. All the solvents were stored under nitrogen atmosphere in glovebox.
Methylene chloride, diethyl ether, acetone, ethyl acetate and hexanes were purchased
from Fisher Scientific and used as received. Nickel acetylacetonate (Ni(acac)2) and nickel
cyclooctadiene (Ni(COD)2) were purchased from Aldrich or Aldrich and Strem
respectively. Tricyclohexylphosphine was purchased from Strem. 1,3-Bis(2,6-di-iso-
propylphenyl)imidazolinium tetrafluoroborate (SIPr·HBF4) was purchased from Aldrich,
1,3-Bis(2,6-di-isopropylphenyl)imidazolinium chloride (SIPr·HCl) (S1) and 4,5-dimethyl-
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
5
1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPrMe·HCl) (S2) were prepared
according to the literature procedures. m-Bis(m-phenoxyphenyl)benzene (Santovac© 5P
Ultra) was purchased from Scientific Instrument Services, Inc. 4-methoxybiphenyl, and
phenyl 4-trifluoromethylphenyl ether were purchased from Alfa-Aesar. Diphenyl ether,
di-4-methylphenyl ether, 4-tert-butylanisole, anisole, dibenzofuran, 1- and 2-
methoxynaphthalene, sodium tert-butoxide were purchased from Aldrich and used as
received. Triethylsilane, diisobutylaluminum hydride (1M solution in hexanes),
trimethylaluminum (2M solution in toluene) were purchased from Aldrich. N-methy-N-
(trimethylsilyl) trifluoroacetamide (MSTFA) was ordered from Acros. Anhydrous copper
iodide, pyridine-2-carboxylic acid (picolinic acid), anhydrous K3PO4, phenols and aryl
iodides (if not otherwise mentioned) were purchased from Aldrich. Other solvents and
reagents were ordered from Aldrich and used as received. Hydrogen (>99%) was
purchased from Linde Gas North America LLC and used as received.
3. Preparation of Diaryl and Benzyl Ethers General procedure for the preparation of diarylethers (modified literature
procedure) (S3)
O
R1 R2
HO
R1 R2
+I
K3PO4, DMSO,100 oC, 20h
10 mol% CuI,20 mol% L
N CO2HL =
In a glovebox, a 50 ml round bottom flask was charged with copper (I) iodide (152 mg,
0.798 mmol), picolinic acid (pyridine-2-carboxylic acid, 197 mg, 1.60 mmol), aryl iodide
(8.00 mmol), phenol (9.60 mmol), potassium phosphate (16.0 mmol, 3.40 g), a magnetic
stir bar and DMSO (16 ml). The reaction flask was sealed with a septum, removed from
the box, and the reaction mixture was stirred at 100 °C for 20 h. The reaction mixture was
cooled and diluted with a 1:1 mixture of saturated aqueous solution of ammonium
chloride (100 ml) and water (100 ml). The crude product was extracted with methylene
chloride (3×100 ml). The combined organic extracts were successively washed with a 5%
aqueous solution of potassium hydroxide (100 ml), brine (100 ml) and dried over
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
6
anhydrous sodium sulfate. The crude product was preadsorbed on silicagel (3-4 g) and
purified by flash column chromatography.
Di-2-methoxyphenyl ether (a model of the 5-O-5 lignin ether linkage) (S4)
Prepared according to the general procedure using 2-iodoanisole (0.963 g,
4.11 mmol), guaiacol (2-methoxyphenol, 0.597 g, 4.81 mmol), potassium
phosphate (1.89 g, 8.90 mmol), copper (I) iodide (78 mg, 0.41 mmol), pyridine-2-
carboxylic acid (100 mg, 0.812 mmol) and DMSO (8 ml). The crude product was
purified by flash column chromatography (eluent: hexanes to hexanes-ethyl acetate, 10:1)
to give di-2-methoxyphenyl ether as a white solid (0.425 g, 1.84 mmol) in 45% yield. 1H
NMR (400 MHz, CDCl3) δ 7.04-7.10 (m, 2H), 6.98 (dd, J = 1.5, 8.0 Hz, 2H), 6.80-6.90
(m, 4H), 3.86 (s, 6H). 13C {1H} NMR (100 MHz, CDCl3) δ 150.5 (C), 146.0 (C), 123.7
(CH), 120.8 (CH), 118.8 (CH), 112.6 (CH), 55.9 (CH3).
2-Methoxyphenyl phenyl ether (a model of the 5-O-5 lignin ether linkage) (S5)
Prepared according to the general procedure using iodobenzene (0.760 g,
3.16 mmol), guaiacol (2-methoxyphenol, 0.654 g, 5.26 mmol), potassium
phosphate (1.78 g, 8.34 mmol), copper (I) iodide (80 mg, 0.42 mmol),
pyridine-2-carboxylic acid (103 mg, 0.836 mmol) and DMSO (8 ml). The crude product
was purified by flash column chromatography (eluent: hexanes to hexanes-ethyl acetate,
10:1) to give 2-methoxyphenyl phenyl ether as a white solid (0.455 g, 2.27 mmol) in 72%
yield. 1H NMR (400 MHz, CDCl3) δ 7.27-7.34 (m, 2H), 7.10-7.17 (m, 1H), 6.89-7.08 (m,
6H), 3.85 (s, 3H).
Di-3-methoxyphenyl ether (S5, S6)
Prepared according to the general procedure using 3-iodoanisole
(0.717 g, 3.06 mmol), 3-methoxyphenol (0.469 g, 3.77 mmol),
potassium phosphate (1.66 g, 7.82 mmol), copper (I) iodide (60 mg, 0.32 mmol),
pyridine-2-carboxylic acid (83 mg, 0.67 mmol) and DMSO (6 ml). The crude product
was purified by flash column chromatography (eluent: hexanes-ethyl acetate, from 20:1
to 10:1) to give di-3-methoxyphenyl ether as a colorless oil (0.486 g, 2.11 mmol) in 69%
yield. 1H NMR (400 MHz, CDCl3) δ 7.23 (apparent t, J = 8.0 Hz, 2H), 6.64-6.69 (m, 2H),
OOMe OMe
OOMe
OMeO OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
7
6.58-6.63 (m, 4H), 3.78 (s, 6H). 13C {1H} NMR (100 MHz, CDCl3) δ 160.9 (C), 158.2
(C), 130.0 (CH), 111.1 (CH), 109.0 (CH), 105.0 (CH), 55.3 (CH3O).
Di-4-tert-butylphenyl ether (S4, S7)
Prepared according to the general procedure using 4-iodo-tert-
butylbenzene (1.18 g, 4.54 mmol), 4-tert-butylphenol (0.817 g, 5.43
mmol), potassium phosphate (1.63 g, 7.67 mmol), copper (I) iodide (74 mg, 0.39 mmol),
pyridine-2-carboxylic acid (103 mg, 0.852 mmol) and DMSO (10 ml). The crude product
was purified by flash column chromatography (eluent: hexanes) to give di-4-tert-
butylphenyl ether as a white solid (1.01 g, 3.58 mmol) in 78% yield. 1H NMR (400 MHz,
CDCl3) δ 7.36 (apparent d, J = 9 Hz), 6.97 (apparent d, J = 9 Hz), 1.35 (s, 18H). 13C {1H}
NMR (125 MHz, CDCl3) δ 155.1 (C), 145.8 (C), 126.4 (CH), 118.2 (CH), 34.3 (C), 31.5
(CH3).
Di-3-methylphenyl ether (S8, S9)
Prepared according to the general procedure using 3-iodotoluene
(0.889 g, 4.03 mmol), 3-methylphenol (0.535 g, 4.95 mmol),
potassium phosphate (1.69 g, 7.96 mmol), copper (I) iodide (77 mg, 0.40 mmol),
pyridine-2-carboxylic acid (100 mg, 0.812 mmol) and DMSO (8 ml). The crude product
was purified by flash column chromatography (eluent: hexanes) to give di-3-
methylphenyl ether as an colorless oil (0.655 g, 3.30 mmol) in 82% yield. 1H NMR (400
MHz, CDCl3) δ 7.23 (t, J = 8 Hz, 2H), 6.93 (apparent d, J = 7.5 Hz, 2H), 6.84-6.86
(apparent br s, 2H), 6.81-6.84 (m, J = 8.0, 2 Hz, 2H), 2.35 (s, 6H).13C {1H} NMR (125
MHz, CDCl3) δ 157.3 (C), 139.8 (C), 129.4 (CH), 119.5 (CH), 115.9 (CH), 21.4 (CH3).
4-Methoxyphenyl 4-trifluoromethylphenyl ether (S10)
Prepared according to the general procedure using 4-iodo-
trifluoromethylbenzene (0.853 g, 3.14 mmol), 4-methoxyphenol
(0.474 g, 3.82 mmol), potassium phosphate (1.97 g, 9.28 mmol), copper (I) iodide (58
mg, 0.30 mmol), pyridine-2-carboxylic acid (75 mg, 0.61 mmol) and DMSO (6 ml). The
crude product was purified by flash column chromatography (eluent: hexanes to hexanes-
O
tButBu
OMe Me
O
F3C OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
8
ethyl acetate, 40:1) to give 4-methoxyphenyl 4-trifluoromethylphenyl ether as a white
solid (0.706 g, 2.63 mmol) in 84% yield. 1H NMR (400 MHz, CDCl3) δ 7.54 (d, J = 9 Hz,
2H), 7.01 (apparent d, J = 9 Hz, 2H), 6.98 (d, J = 8.5 Hz, 2H), 6.93 (apparent d, J = 9 Hz,
2H), 3.83 (s, 3H). 19F {1H} NMR (470 MHz, CDCl3) δ -62.1. 13C {1H} NMR (470 MHz,
CDCl3). 13C {1H} NMR (125 MHz, CDCl3) δ 161.5 (C), 156.7 (C), 148.8 (C), 127.0 (q,
JCF = 3.5 Hz, CH), 124.2 (q, JCF = 272 Hz, CF3), 124.3 (q, JCF = 32 Hz, C), 121.5 (CH),
116.9 (CH), 115.2 (CH), 55.7 (CH3).
4-Methoxyphenyl phenyl ether (S11)
Prepared according to the general procedure using iodobenzene (0.836
g, 4.09 mmol), 4-methoxyphenol (0.654 g, 5.26 mmol), potassium
phosphate (1.73 g, 8.14 mmol), copper (I) iodide (79 mg, 0.42 mmol), pyridine-2-
carboxylic acid (119 mg, 0.967 mmol) and DMSO (8 ml). The crude product was
purified by flash column chromatography (eluent: hexanes to hexanes-ethyl acetate, 20:1)
to give 4-methoxyphenyl phenyl ether as a colorless oil (0.651 g, 3.24 mmol) in 79%
yield. 1H NMR (400 MHz, CDCl3) δ 7.35 (apparent t, J = 8 Hz, 2H), 7.09 (apparent t, J =
7.5 Hz, 1H), 7.04 (apparent d, J = 9.0 Hz, 2H), 7.01 (apparent t, J = 8 Hz, 2H), 6.93
(apparent d, J = 9.0 Hz, 2H), 3.84 (s, 3H).13C {1H} NMR (100 MHz, CDCl3) δ 158.5 (C),
155.8 (C), 150.0 (C), 129.5 (CH), 122.3 (CH), 120.7 (CH), 117.5 (CH), 114.8 (CH), 55.5
(CH3).
Di-2-methylphenyl ether (S11)
Prepared according to the general procedure using 2-iodomethylbenzene
(0.899 g, 4.12 mmol), 2-methylphenol (0.492 g, 4.54 mmol), potassium
phosphate (1.84 g, 8.67 mmol), copper (I) iodide (81 mg, 0.43 mmol),
pyridine-2-carboxylic acid (99 mg, 0.80 mmol) and DMSO (8 ml). The crude product
was purified by flash column chromatography (eluent: hexanes) to give di-2-
methylphenyl ether as a colorless oil (0.692 g, 3.49 mmol) in 85% yield. 1H NMR (400
MHz, CDCl3) δ 7.32 (d, J = 7.5 Hz, 2H), 7.19 (apparent t, J = 8 Hz, 2H), 7.08 (apparent t,
J = 7.5 Hz, 2H), 6.81 (d, J = 8 Hz, 2H), 2.37 (s, 6H). 13C {1H} NMR (100 MHz, CDCl3) δ
155.2 (C), 131.3 (CH), 128.8 (C), 127.0 (CH), 123.0 (CH), 117.6 (CH), 16.1 (CH3).
O
OMe
OMe Me
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
9
2-(Hexyloxy)naphthalene (S12).
A 25 ml Schlenk flask equipped with a Teflon stopcock and
a magnetic stir bar was charged with anhydrous potassium
carbonate (1.05 g, 7.60 mmol), evacuated and filled with argon. 2-Naphthol (0.721 g,
5.00 mmol), acetone (7.5 ml) and 1-iodohexane (1.64 g, 7.73 mmol) were added. The
flask was sealed and the reaction mixture was stirred at 70 °C for 14 h. The mixture was
cooled to room temperature, evaporated and the residue was partitioned between ether
(150 ml) and water (50 ml). Organic layer was separated, washed with 5% aqueous
potassium hydroxide solution (50 ml), brine (50 ml), and dried over anhydrous sodium
sulfate. The solution was evaporated on silica gel (3.2 g) and the crude product was
purified by flash column chromatography (eluent: hexanes) to give 2-
(hexyloxy)naphthalene as a colorless oil (1.05 g, 4.60 mmol) in 92% yield. 1H NMR (400
MHz, CDCl3) δ 7.77-7.78 (m, 3H), 7.47-7.54 (m, 1H), 7.37-7.43 (m, 1H), 7.17-7.27 (m,
2H), 7.32 (t, J = 6.5 Hz, 2H), 1.86-1.97 (2H), 1.52-1.63 (m, 2H), 1.38-1.51 (m, 4H), 0.97-
1.07 (m, 3H). 13C {1H} NMR (100 MHz, CDCl3) δ 157.1 (C), 134.6 (C), 129.24 (CH),
128.8 (C), 127.6 (CH), 126.6 (CH), 126.2 (CH), 123.4(CH), 119.0 (CH), 106.5 (CH),
67.9 (CH2), 31.6 (CH2), 29.2 (CH2), 25.8 (CH2), 22.6 (CH2), 14.0 (CH3).
4-(Hexyloxy)biphenyl (S13)
Prepared in a similar manner to 2-(hexyloxy)naphthalene using
4-hydroxybiphenyl (0.853 g, 5.01 mmol), 1-iodohexane (1.65 g,
7.78 mmol), potassium carbonate (1.05 g, 7.60 mmol) and
acetone (7.5 ml). The crude product was purified by flash column chromatography
(eluent: hexanes) to give 4-(hexyloxy)biphenyl as white crystals (0.977 mg, 3.84 mmol)
in 76% yield. The product was further purified via recrystallization from methanol. 1H
NMR (400 MHz, CDCl3) δ 7.60 (apparent d, J = 7.5 Hz, 2H), 7.56 (apparent d, J = 8.5
Hz, 2H), 7.46 (apparent t, J = 7.5 Hz, 2H), 7.34 (apparent t, J = 8.5 Hz, 1H), 7.01
(apparent d, J = 7.5 Hz, 2H), 4.03 (t, J = 6.5 Hz, 2H), 1.85 (m, 2H), 1.47-1.59 (m, 2H),
1.34-1.59 (m, 4H), 0.91-1.04 (m, 3H). 13C {1H} NMR (100 MHz, CDCl3) δ 158.7 (C),
O
O
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
10
140.8 (C), 133.5 (C), 128.7 (CH), 128.0 (CH), 126.7 (CH), 126.5 (CH), 114.7 (CH), 68.0
(CH2), 31.6 (CH2), 29.3 (CH2), 25.7 (CH2), 22.6 (CH2), 14.0 (CH3). General procedure for preparation of benzyl aryl ethers
R1
R2HO
R1 R2
+K2CO3, acetone,
reflux, 3 h
Br O
A 100 ml flask equipped with a reflux condenser, argon inlet and magnetic stir bar, was
charged with anhydrous potassium carbonate (1.66 g, 12 mmol), evacuated and filled
with argon. A phenol (12 mmol), acetone (24 ml), and a benzyl bromide (10 mmol) were
then added and the reaction mixture was refluxed for 3 h. The mixture was cooled down,
and filtered. The filtrate was evaporated and dissolved in methylene chloride (100 ml).
The resulting solution was washed with 5% aqueous solution of potassium hydroxide (50
ml), brine (50 ml) and dried over anhydrous sodium sulfate. The solution was evaporated
and the crude product was either purified by flash column chromatography (liquids) or by
recrystallization (solids).
4-tert-Butylbenzyl phenyl ether.
Prepared according to the general procedure using 4-tert-butylbenzyl
bromide (2.47 g, 10.9 mmol), phenol (1.20 g, 12.8 mmol), potassium
carbonate (2.12 g, 15.3 mmol), and acetone (25 ml). The crude
product was recrystallyzed from hexanes (10 ml) to give 4-tert-butylbenzyl phenyl ether
as white crystals (2.23 g, 9.28 mmol) in 85% yield. 1H NMR (400 MHz, CDCl3) δ 7.47
(apparent d, J = 8.5 Hz, 2H), 7.42 (apparent d, J = 8.5 Hz, 2H), 7.34 (apparent t, J = 8.0
Hz, 2H), 6.98-7.07 (m, 3H), 1.39 (s, 9H). 13C {1H} NMR (100 MHz, CDCl3) δ 158.9 (C),
151.0 (C), 134.0 (C), 129.4 (CH), 127.4 (CH), 125.5 (CH), 120.8 (CH), 114.8 (CH), 69.8
(CH2), 34.6 (C), 31.4 (CH3). Anal. Calcd for C17H20O: C, 84.96; H, 8.39; Found: C, 85.05; H, 8.55.
OtBu
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
11
3,4-Dimethoxybenzyl 2-methoxyphenyl ether (a model of the α-O-4 lignin ether
linkage) (S14)
Prepared according to the general procedure using 3,4-
dimethoxybenzyl bromide (6.49 g, 28.1 mmol) (15), 2-
methoxyphenol (4.85 g, 39.1 mmol), potassium carbonate (4.82 g,
34.9 mmol), and acetone (60 ml). The crude product was
recrystallized from hexanes (ca 300 ml) to give 3,4-dimethoxybenzyl 2-methoxyphenyl
ether as white crystals (6.05 g, 22.1 mmol) in 78% yield. 1H NMR (500 MHz, CDCl3) δ
6.81-7.03 (m, 7H), 5.08 (s, 2H), 3.88 (s, 6H), 3.87 (s, 3H). 13C {1H} NMR (125 MHz,
CDCl3) δ 149.8 (C), 149.1 (C), 148.7 (C), 129.8 (C), 148.2 (C), 121.5 (CH), 120.7 (CH),
120.0 (CH), 111.9 (CH), 111.0 (CH), 110.8 (CH), 71.2 (CH2), 55.9 (CH3O), 55.8
(CH3O).
1-Methoxy-1-phenylpropane (S16)
A 100 ml two neck flask equipped with reflux condenser and argon inlet and
magnetic stir bar was evacuated, filled with argon and charged with NaH
(60% suspension in mineral oil, 1.40 g, 57.5 mmol) and THF (20 ml). 1-Phenyl-1-
propanol (3.97 g, 29.2 mmol) was added by a syringe and the reaction mixture was stirred
at room temperature for 5 min. Methyl iodide (8.17 g, 57.6 mmol) was added by a
syringe over 2 min and the reaction mixture was refluxed for 2 h, then cooled to room
temperature and carefully quenched with water (40 ml) to give a two-layer mixture. THF
was evaporated, and the crude product was extracted from the resulting aqueous mixture
with dichloromethane (3×25 ml). The combined organic layers were dried over
anhydrous magnesium sulfate and evaporated. The oily residue was distilled in vacuum
(bp. 75-77 °C/18-20 mm) to give 1-methoxy-1-phenylpropane (3.04 g, 20.2 mmol) as a
colorless oil in 69% yield. 1H NMR (400 MHz, CDCl3) δ 7.30-7.37 (m, 2H), 7.27
(apparent d, J = 7.0 Hz, 3H), 4.01 (t, J = 6.5 Hz, 1H), 3.21 (s, 3H), 1.75-1.89 (m, 1H),
1.59-1.73 (m, 1H), 0.87 (t, J = 7.5 Hz, 3H). 13C {1H} NMR (100 MHz, CDCl3) δ 142.2
(C), 128.2 (CH), 127.4 (CH), 126.7 (CH), 85.5 (CH), 56.6 (OCH3), 30.9 (CH2), 10.1
(CH3).
O
MeOOMe
MeO
OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
12
Methyl 4-tert-butylbenzyl ether (S17)
Under argon, a 100 ml Schlenk flask was charged with sodium
methoxide (0.680 g, 12.6 mmol), methanol (20 ml), magnetic stir bar
and sealed with a septum. To the resulting solution 4-tert-butylbenzyl bromide (2.37 g,
10.4 mmol) was added by a syringe at room temperature for 2 min. The reaction mixture
was stirred for 48 h, then solvent was evaporated and the residue was treated with water
(100 ml). The crude product was extracted with ether (3×50 ml), the combined organic
extracts were washed with brine (50 ml), and dried over anhydrous sodium sulfate. The
product was purified by flash column chromatography (eluent: ethyl acetate-hexanes
1:40) to give methyl 4-tert-butylbenzyl ether as a colorless oil (1.21 g, 6.79 mmol) in
65% yield. 1H NMR (500 MHz, CDCl3) δ 7.43 (apparent d, J = 8.4 Hz, 2H), 7.33
(apparent d, J = 8.4 Hz, 2H), 4.48 (s, 2H), 3.43 (s, 3H), 1.38 (s, 9H). 13C {1H} NMR (125
MHz, CDCl3) δ 150.9 (C), 133.5 (C), 127.9 (CH), 125.5 (CH), 74.8 (CH3), 58.3 (CH2),
34.8 (C), 31.6 (CH3).
Preparation of 1-(3,4-Dimethoxyphenyl)-2-(2-methoxyphenoxy)-l,3-propanediol
(S18- S20) (a model of the β-O-4 lignin ether linkage; modified literature procedure
for an analogous compound) (S21-S23)
A. Methyl 2-(2-methoxyphenoxy)acetate (S24)
A 250 ml two-neck flask equipped with a reflux condenser, argon inlet, and magnetic stir
bar was charged with potassium carbonate (10.40 g, 75.24 mmol), evacuated, and filled
with argon. Acetone (80 ml), methyl bromoacetate (11.59 g, 75.76 mmol), and guaiacol
(6.20 g, 49.9 mmol) were added to the flask via syringe and the reaction mixture was
OOMe OH
OMe
OMe
HO
OH
OMeBr
O
OMe+O
OMe
OMe
O
K2CO3, acetone,reflux, 2.5 h
OMetBu
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
13
refluxed for 2.5 h, then cooled to room temperature and filtered. The filtrate was
evaporated, to give a pale yellow oil, which was dissolved in methanol and placed in a
fridge (ca -5 °C) overnight. The resulting colorless crystals were filtered, and washed
with cold methanol to give methyl 2-(2-methoxyphenoxy)acetate (8.40 g, 42.8 mmol) in
85% yield. 1H NMR (400 MHz, CDCl3) δ 6.94-7.00 (m, 1H), 6.80-6.92 (m, 3H), 4.68 (s,
2H), 3.86 (s, 3H), 3.77 (s, 3H). 13C {1H} NMR (125 MHz, CDCl3) δ 169.4 (C), 150.0
(C), 147.2 (C), 122.6 (CH), 120.7 (CH), 114.6 (CH), 112.2 (CH), 66.5 (CH2), 55.8 (CH3),
55.0 (CH3).
B. Methyl 3-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-methoxyphenoxy)propanoate
O
OMe
OMe
O
THF 0 oC,LDA
30 min
O CO2MeLi+
MeOOMe
CHO
OMeO
OMe OH
MeO O OMe
OMe
THF, -78 oC,2 h
A 250 ml Schlenk flask equipped with a magnetic stir bar and septum cap, was evacuated
and filled with argon. THF (30 ml) and diisopropylamine (3.1 ml, 22 mmol) were added
by a syringe. The resulting solution was cooled to 0 °C and a 1.6 M solution of n-
butyllithium in hexanes (13.75 ml, 22.00 mmol) was added by a syringe for 3 min. The
reaction mixture was stirred for 30 min, then cooled to -78 °C and a solution of methyl 2-
(2-methoxyphenoxy)acetate (3.92 g, 20.0 mmol) in THF (40 ml) was added dropwise for
15 min to give a pale yellow solution. The solution was stirred for 15 min and a solution
of 3,4-dimethoxybenzaldehyde (3.32 g, 20.0 mmol) in THF (20 ml) was added dropwise
for 5 min. The reaction mixture was stirred for 2 h, then quenched at -78 °C with a
saturated solution of ammonium chloride (75 ml), and warmed up to room temperature to
give a two-layer mixture. The organic layer was separated, and the aqueous layer was
extracted with ethyl acetate (3×50 ml). The combined organic layers were washed with
brine (50 ml), and dried over anhydrous sodium sulfate. The crude product was purified
by flash column chromatography (eluent: ethyl acetate-hexanes from 1:2 to 1:1) to give
methyl 3-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-methoxyphenoxy)propanoate (3.59 g,
9.91 mmol) as a white solid in 49% yield. 1H NMR (500 MHz, CDCl3), major isomer δ
6.78-7.06 (m, 7H), 5.13 (t, J = 5.5 Hz, 1H), 4.73 (d, J = 5.0 Hz, 1H), 3.87 (s, 3H), 3.86 (s,
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
14
3H), 3.84 (s, 3H), 3.71 (d, J = 6.0 Hz, 1H), 3.68 (s, 3H); minor isomer δ 6.78-7.06 (m,
7H), 5.07 (dd, J = 7.0, 3.5 Hz, 1H), 4.50 (d, J = 7.0 Hz, 1H), 3.87 (s, 3H), 3.86 (s, 3H),
3.85 (s, 3H), 3.60 (s, 3H). 13C {1H} NMR (125 MHz, CDCl3) major + minor δ 169.9,
169.8, 150.5, 150.3, 149.0, 148.9, 148.8, 148.7, 147.2, 147.1, 131.7, 130.6, 123.9, 121.1,
121.0, 119.4, 119.2, 118.8, 118.1, 112.3, 110.7, 110.0, 109.8, 85.3, 83.9, 74.7, 73.8, 55.8,
55.7, 52.1, 52.0. Ratio of diastereomers (major to minor): 4.5. Anal. Calcd for C19H22O7: C, 62.97; H, 6.12; Found: C, 62.68; H, 6.07.
C. 1-(3,4-Dimethoxyphenyl)-2-(2-methoxyphenoxy)-l,3-propanediol (S18)
OOMe OH
OMe
OMe
HO
OOMe OH
MeO O OMe
OMe NaBH4THF/water (3:1),
rt, 22 h A 250 ml Schlenk flask was charged with methyl 3-(3,4-dimethoxyphenyl)-3-hydroxy-2-
(2-methoxyphenoxy)propanoate (3.15 g, 8.69 mmol), a magnetic stir bar and sealed with
a septum. The flask was evacuated, filled with argon and a 3:1 mixture of THF/water (80
ml) was added. Sodium borohydride (43.6 mmol) was added to the solution in two
portions (2×0.825 g) over about 1 h, and the stirring was continued for 22 h. The
resulting mixture was evaporated to ca. 20 ml, diluted with 80 ml of water and the crude
product was extracted with ethyl acetate (3×60 ml). The combined extracts were washed
with brine (50 ml) and dried over anhydrous sodium sulfate. The product was purified by
flash column chromatography (eluent: ethyl acetate-hexanes from 1:1 to 3:1) to give 1-
(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-l,3-propanediol (2.32 g, 6.94 mmol) as a
white solid in 80% yield. 1H NMR (500 MHz, CDCl3), major + minor diastereoisomers δ
6.80-7.14 (m, 7H), 4.95-5.01 (m, 1H), 4.13-4.19 (m, 0.77 H, major diastereoisomer), 3.99
(m, 0.35 H, minor isomer), 3.82-3.95 (m, 10H), 3.44-3.74 (m, 2H), 2.69-2.82 (1H), 1.71-
1.83 (m, 0.3H). 13C {1H} NMR (125 MHz, CDCl3) major + minor diastereomers δ 151.6,
151.3, 149.1, 149.0, 148.9, 148.5, 147.6, 146.9, 132.5, 132.1, 124.2 (2C), 121.6 (2C),
121.0, 120.9, 119.6, 118.4, 112.2, 111.0, 109.9, 109.2, 89.4, 87.4, 73.9, 72.7, 61.0, 60.7,
55.9 (C). Ratio of diastereomers (major to minor): 2.2. MS (ESI+) m/z: 357.3 [M+Na]+.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
15
4. Stability of the Ni(COD)2/PCy3 under the Conditions of Reductive Cleavage of
Aromatic C-O bonds
Figure S1. Attempted hydrogenolysis of diphenyl ether catalyzed by Ni(COD)2/PCy3.
+ H2 m-xylene,120 oC, 16 h
O
HO+X
+
(0.2 equiv.)
+
+
conversion: ca 1%
(1 bar)Ni(COD)2
44% 7%products of the C-P bond
cleavage in PCy3
(0.4 equiv.)(1 equiv.)
The yields were based on theamount of PCy3, assuming thatonly one cyclohexyl group of thephosphine ligand is converted to the hydrocarbons.
(traces, ~1%)P 3
Procedure:
The reaction was conducted according to General Procedure A (p. 29) with Ni(COD)2
(8.4 mg, 3.1⋅10-2 mmol), PCy3 (16.7 mg, 5.95⋅10-2 mmol), diphenyl ether (25.4 mg, 0.155
mmol), dodecane (internal standard for GC, 25.8 mg) and m-xylene (0.8 ml) at 120 °C for
16 h. After saturation of the reaction mixture with hydrogen at room temperature, the
yellow color changed to dark red within 15 min; the final color of the reaction mixture
after heating for 16 h was dark brown. GC and GC/MS analyses of the reaction mixture
showed low conversion of diphenyl ether (~1%). Benzene was detected in only trace
amounts (1%). Cyclohexane (m/z 84) and cyclohexene (m/z 82) from cleavage of the C-P
bond in PCy3 were observed in 44% and 7% yields, respectively. The yields were based
on the amount of PCy3, assuming that only one cyclohexyl group of the phosphine ligand
is converted to the hydrocarbons. Cyclooctane (m/z 112) from hydrogenation of COD
was also detected.
Decomposition of PCy3 under the Conditions of Hydrogenolysis
H2 m-xylene,120 oC, 16 h
+
(1 equiv.)
+ +(1 bar)
Ni(COD)2
55% 7%(2 equiv.)
P 3
The reaction was conducted according to General Procedure A (p. 29) with Ni(COD)2
(8.4 mg, 3.1⋅10-2 mmol), PCy3 (18.0 mg, 6.42⋅10-2 mmol), dodecane (internal standard for
GC, 24.4 mg) and m-xylene (0.8 ml) at 120 °C for 16 h. The color changes were similar
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
16
to those observed for the above procedure of the reaction with diphenyl ether. GC and
GC/MS analyses of the reaction mixture showed the formation of cyclohexane (m/z 84)
and cyclohexene (m/z 82) in 55% and 7% yields, respectively. The yields were based on
the amount of PCy3, assuming that only one cyclohexyl group of the phosphine ligand is
converted to the hydrocarbons. Cyclooctane (m/z 112) from hydrogenation of COD was
also detected.
Figure S2. Attempted Reductive Cleavage of Anisole with Triethylsilane Catalyzed
by the Combination of Ni(COD)2/PCy3.
+ Et3SiH toluene,140 oC, 16 h
OMeX
+
(0.2 equiv.)
+
+
conversion ca 1%(25 equiv.)
Ni(COD)2
18% 41%products of the C-P bond
cleavage in PCy3
(0.4 equiv.)(1 equiv.)
The yields were based on theamount of PCy3, assuming thatonly one cyclohexyl group of thephosphine ligand is converted to the hydrocarbons.
(traces, ~1%)P 3
The reaction was conducted according to the General Procedure (p. 18) with Ni(COD)2
(8.3 mg, 3.0⋅10-2 mmol), PCy3 (16.7 mg, 5.95⋅10-2 mmol), anisole (16.0 mg, 0.148
mmol), triethylsilane (600 µl, 3.76 mmol), dodecane (internal standard for GC, 23.2 mg)
and toluene (0.3 ml) at 140 °C for 16 h. The starting reaction mixture was yellow; after
heating at 140 °C for 5 min, the color changed to dark red; the color after heating at 140
°C for 16 h was dark brown, and nickel black was observed. GC and GC/MS analyses of
the reaction mixture showed low conversion of anisole (ca 1%). Cyclohexane (m/z 84)
and cyclohexene (m/z 82) from cleavage of the C-P bond in PCy3 were observed in 18%
and 41% yields, respectively. These yields were based on the amount of PCy3, assuming
that only one cyclohexyl group of the phosphine ligand is converted to the hydrocarbons.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
17
Decomposition of PCy3 under the Conditions of Reductive Cleavage with
Triethylsilane
Et3SiH toluene,140 oC, 16 h
+
(1 equiv.)
+ +
(125 equiv.)
Ni(COD)2
8% 36%(2 equiv.)
P 3
The reaction was conducted according to General Procedure (p. 18) with Ni(COD)2 (8.5
mg, 3.1⋅10-2 mmol), PCy3 (16.7 mg, 6.42⋅10-2 mmol), dodecane (internal standard for GC,
19.2 mg) and toluene (0.3 ml) at 140 °C for 16 h. The color changes were similar to those
for the above procedure containing anisole. GC and GC/MS analyses of the reaction
mixture showed the formation of cyclohexane (m/z 84) and cyclohexene (m/z 82) in 8%
and 36% yields, respectively. The yields were based on the amount of PCy3, assuming
that only one cyclohexyl group of the phosphine ligand is converted to the hydrocarbons.
Cyclooctane (m/z 112) from hydrogenation of COD was also detected.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
18
5. Nickel-NHC Catalyzed Reductive Cleavage of Aryl and Benzyl Ethers with
Hydride Donors
Reactions were conducted in 4 ml screw thread vials (15 mm×45 mm; supplied by
Kimble Chase) equipped with Teflon-lined screw caps (13 mm diameter, 425 GPI thread;
supplied by Qorpak) and Teflon-coated magnetic stir bars (3 mm×10 mm; supplied by
Fisher Scientific). The vials were heated in an aluminum heating block; the reaction
temperature was measured by a thermocouple immersed into a silicone oil in a separate 4
ml vial, placed in the same heating block.
General procedure
In a glovebox, a 4 ml vial was charged with Ni(COD)2 (0.75⋅10-2-3.0⋅10-2 mmol, 5-20
mol%), a carbene ligand salt (1.5⋅10-2-6.0⋅10-2 mmol, 10-40 mol%), NaOtBu (0.375
mmol) and a magnetic stir bar. After 0.3 ml of 0.5 M solution of aryl or benzyl ether
(0.15 mmol) in toluene and dodecane (internal standard for GC) were added, the mixture
was stirred for 3 min and DIBAL (0.375 mmol, 1M solution in hexanes) or triethylsilane
(0.375-1.50 mmol) was added by a syringe. Note, for reductions with Li(Al(OtBu)3H, the
reductant was added in the beginning together with other solid reagents and the reaction
mixture was diluted with additional 0.5 ml of toluene. The resulting dark brown mixture
was stirred for 1 min. The reaction vial was sealed with a screw cap, removed from the
glovebox and heated at 60-140 °C for 16-96 h (see Table S2). After cooling to room
temperature, dark brown to black reaction mixture was diluted with ether (1 ml) and
carefully quenched at 0 °C with 1 ml of 1.5 M aqueous HCl. The resulting mixture was
stirred for 10 min for reactions with triethylsilane or 40 min when DIBAL or
Li(Al(OtBu)3H were used. The organic layer was separated, the aqueous layer was
extracted with ether (1 ml), and the combined organic layers were passed through a short
pad of Celite and subjected to GC and GC/MS analyses. The products were all known
compounds and were identified using GC/MS and GC by comparison of the mass spectra
and retention times of the products with those of authentic compounds.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
19
Discussion
We initially tested nickel-NHC catalysts for the reduction of the C-O bond of
diphenyl ether in the presence of the hydride donors, DIBALH (diisobutylaluminum
hydride), LiAl(OtBu)3H, and Et3SiH in place of H2, because of the convenience of
evaluating catalysts for reactions with liquid and solid reagents. These reactions were
conducted with the combination of a nickel(0) precursor, Ni(COD)2 or Ni(acac)2 (acac,
acetylacetonate), and an NHC ligand formed in situ by deprotonation of the
corresponding salt NHC⋅HX with a base (NaOtBu) (Table S1). We found that the highest
yields of the products from aromatic C-O bond cleavage were obtained with Ni(COD)2 as
the source of nickel, with SIPr⋅HCl (shown in Fig. S3) as ligand precursor, and the
aluminium hydride donors DIBALH and LiAl(OtBu)3H (2.5 equiv.) in the presence of
NaOtBu (2.5 equiv.) as a base in toluene (Table S1 and S2). Although the base was added
initially to generate the free carbene from the salt form, the highest yields of the products
were obtained with an excess of base (Table S1). Under these conditions, cleavage of
diphenyl ether with DIBALH proceeded, even at 60 °C, to give benzene and phenol in
nearly quantitative yields in the presence of 20 mol% Ni(COD)2 and 40 mol% of
SIPr⋅HCl (Table S2, Entry 1). Reaction with LiAl(OtBu)3H occurred with 10 mol% of the
catalyst at 100 °C to give the arene and phenol in 82% and 86% yields (Table S2, Entry
2). Cleavage with the milder reagent Et3SiH (10 equiv.) occurred with less catalyst (5%)
but gave moderate yields of the products (Table S2, Entry 3).
This class of catalyst, in tandem with either aluminum hydrides or silane reducing
agents, was then tested for the reductive cleavage of a series of unactivated aryl and
benzyl ethers. In addition to the cleavage of diphenyl ether, reduction of a cyclic diaryl
ether, dibenzofuran, gave 2-hydroxybiphenyl in nearly quantitative yield (99%) with
triethylsilane as hydride source at 120 °C for 48 h (Table S2, Entry 4). 4-
Methoxybiphenyl was cleaved with triethylsilane, DIBALH and LiAl(OtBu)3H to form
excellent yields of biphenyl (89%-99%) in the presence of the Ni-SIPr catalyst (Table S2,
Entries 5-7). The same system catalyzed reduction of the fully unactivated alkyl ether
anisole with DIBALH and LiAl(OtBu)3H to give benzene in 87% and 62% yields,
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
20
respectively, at 120 °C (Table S2, Entries 8-9). Cleavage of the aromatic C-O bond in
anisole with the milder reductant triethylsilane was induced by Ni(COD)2 in combination
with the bulkier carbene ligand IPrMe (shown in Fig. S3) to give benzene in 77% yield at
140 °C for 96 h (Table S2, Entry 10). Under the same conditions the reaction catalyzed
by Ni(COD)2 and PCy3 failed to form products from cleavage of anisole, instead forming
cyclohexane and cyclohexene from the phosphine ligand (Fig. S2).
The Ni-SIPr system also catalyzed the reduction of unactivated benzyl ethers (Table S2,
Entries 11-14). In this case, cleavage occurred at the benzylic C-O bond. Reduction of
this C-O bond in an alkyl benzyl ether proceeded much more slowly than reduction of
aryl benzyl ethers and required similar conditions to those for the cleavage of alkyl aryl
ethers. Thus, reduction of α-ethylbenzyl methyl ether with aluminum hydrides occurred
at 120 °C for 16 h (Table S2, Entries 11, 12), whereas reduction of phenyl tert-
butylbenzyl ether was complete at 80 °C in 16 h (Table S2, Entries 13, 14).
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
21
Table S1. Selected Results on the Effect of Ligand, Nickel and Hydride Source and Base
Amount on the Reductive Cleavage of Diphenyl Ether. See General Procedure (p. 18). O
+ 10-40% SIPr·HCl"H-" NaOtBu, toluene,
temp, 16 h+HO5-10% Ni(COD)2,
Entry Ligand “Ni” Ni, mol% “H-” “H-”, equiv.
Base, equiv. T, °C Conversion, % Yield of
benzene, % Yield of
phenol, % 1 SImBu⋅HBF4 Ni(COD)2 10 Et3SiH 2.5 2.5 100 20 20 16 2 SIMes⋅HBF4 Ni(COD)2 10 Et3SiH 2.5 2.5 100 46 44 44 3 IMes⋅HCl Ni(COD)2 10 Et3SiH 2.5 2.5 100 52 48 52 4 IPr⋅HCl Ni(COD)2 10 Et3SiH 2.5 2.5 100 58 38 54 5 SIPr⋅HCl Ni(COD)2 10 Et3SiH 2.5 2.5 100 65 42 65 6 SIPr⋅HCl Ni(COD)2 10 Et3SiH 2.5 0.5 100 29 9 21
7 SIPr⋅HCl Ni(COD)2 5 Et3SiH 10 2.5 100 70 56 70 8 IPr⋅HCl Ni(COD)2 5 Et3SiH 10 2.5 100 50 47 50 9 IPr⋅HCl Ni(COD)2 10 DIBALH 2.5 2.5 100 2 0 0 10 SIPr⋅HCl Ni(COD)2 10 DIBALH 2.5 2.5 100 41 41 37 11 IPr⋅HCl Ni(COD)2 10 LiAl(OtBu)3H 2.5 2.5 100 83 75 75 12 SIPr⋅HCl Ni(COD)2 10 LiAl(OtBu)3H 2.5 2.5 100 90 82 86 13 SIPr⋅HCl Ni(COD)2 20 DIBALH 2.5 2.5 60 100 99 99 14 SIPr⋅HCl Ni(COD)2 20 DIBALH 2.5 0.44 60 0 0 0 15 SIPr⋅HCl Ni(acac)2 20 DIBALH 2.5 2.5 60 35 37 10 16 IPr⋅HCl Ni(COD)2 20 DIBALH 2.5 2.5 60 87 87 60 17 - Ni(COD)2 20 DIBALH 2.5 2.5 60 11 11 7 18 IPr⋅HCl Ni(COD)2 20 LiAl(OtBu)3H 2.5 2.5 60 1 0 0 19 SIPr⋅HCl Ni(COD)2 20 LiAl(OtBu)3H 2.5 2.5 60 0 0 0
Figure S3. Carbene Ligands Used in the Study
N N
Cl
IMes HCl
N N
SIMes HBF4
BF4
N N
BF4
SImBu HBF4
N N
IPr HCl
N N
SIPr HCl
Cl Cl
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
22
Table S2. Reductive Cleavage of Aryl and Benzyl Ethers with Hydride Donors. See
General Procedure (p. 18).
R1 OR2 + "H-" 10-40% SIPr·HClNaOtBu (2.5 equiv),
5-20% Ni(COD)2,
R1 = Aryl, Benzyl; R2 = Aryl, Methyl
R1 H
"H-" = DIBALH, LiAl(OtBu)3H, Et3SiH
+
Entry Aryl/Benzyl ether Ni, mol%Hydride donor T, °C Time, h R1H, % R2OH, %
23
LiAl(OtBu)3HEt3SiH*
105
100100
1616
8256†
8670
O
4 Et3SiH 20 120 48 99
OMe
OMe
7 Et3SiH§ 20 120 56 89 nd6 LiAl(OtBu)3H 20 120 32 90 nd
Ph
OMe
Et
12 LiAl(OtBu)3H 20 120 56 91 nd
14 LiAl(OtBu)3H 20 80 16 82 99OPh
tBu
*10 equiv. of Et3SiH. †Phenyltriethylsilane as a side product. ‡Not determined. §25 equiv. of Et3SiH. IIIPrMe·HCl as a ligand. ¶Benzene (15%) as a side product. #4-tert-butylbenzyl alcohol (16%) as a side product.
R2OH(2.5 equiv) toluene
10 Et3SiH§,II 20 140 96 77 nd9 LiAl(OtBu)3H 20 120 36 62 nd
1 DIBAL 20 100 16 99 99O
8 DIBALH 20 120 40 87 nd
5 DIBALH 20 120 16 99 nd‡
11 DIBALH 20 120 16 94 nd
13 DIBALH 20 80 16 79¶ 55#
Conv, %
9070
100
9191
92
100
8485
100
94
100
100
100
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
23
Reductive cleavage of diphenyl ether with DIBALH (Table S2, Entry 1) O
+ 40% SIPr·HClDIBALH NaOtBu, toluene,
60 °C, 16 h+
HO20% Ni(COD)2,
99% 99%
The reaction was conducted according to the general procedure with Ni(COD)2 (8.2 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (25.4 mg, 5.95⋅10-2 mmol), tBuONa (40.2 mg, 0.418 mmol),
diphenyl ether (25.8 mg, 0.152 mmol), DIBALH (0.375 ml of 1M solution in hexanes,
0.375 mmol), dodecane (internal standard for GC, 6.3 mg) and toluene (0.3 ml) at 60 °C
for 16 h. GC and GC/MS analyses of the reaction mixture showed complete conversion
of diphenyl ether and formation of benzene (78 m/z) and phenol (94 m/z) in 99% yields.
Reductive cleavage of diphenyl ether with LiAl(OtBu)3H (Table S2, Entry 2) O
+ 20% SIPr·HClLiAl(OtBu)3H NaOtBu, toluene,
100 °C, 16 h+
HO10% Ni(COD)2,
82% 86%
The reaction was conducted according to the general procedure with Ni(COD)2 (4.1 mg,
1.5⋅10-2 mmol), SIPr⋅HCl (14.0 mg, 3.28⋅10-2 mmol), NaOtBu (38.4 mg, 0.400 mmol),
diphenyl ether (26.4 mg, 0.155 mmol), LiAl(OtBu)3H (96.4 mg, 0.379 mmol), dodecane
(internal standard for GC, 6.4 mg) and toluene (0.8 ml) at 100 °C for 16 h. GC and
GC/MS analyses of the reaction mixture showed formation of benzene (78 m/z) and
phenol (94 m/z) in 82% and 86% yields respectively at 90% conversion of diphenyl
ether.
Reductive cleavage of diphenyl ether with Et3SiH (Table S2, Entry 3) O
+ 10% SIPr·HClEt3SiH NaOtBu, toluene,100 °C, 16 h
+HO5% Ni(COD)2,
56% 70%
+SiEt3
The reaction was conducted according to the general procedure with Ni(COD)2 (2.3 mg,
8.0⋅10-3 mmol), SIPr⋅HCl (7.0 mg, 1.6⋅10-2 mmol), NaOtBu (37.3 mg, 0.388 mmol),
diphenyl ether (25.8 mg, 0.152 mmol), Et3SiH (240 µl, 174 mg, 1.50 mmol), dodecane
(internal standard for GC, 6.3 mg) and toluene (0.3 ml) at 100 °C for 16 h. GC and
GC/MS analyses of the reaction mixture showed formation of benzene (m/z 78) and
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
24
phenol (m/z 94) in 56% and 70% yields respectively at 70% conversion of diphenyl
ether. Triethylphenylsilane (m/z 163, [M-Et]+) was detected as a main side product.
Et3SiOtBu (m/z 173 [M-Et]+) was the major silicon product.
Reductive cleavage of dibenzofuran with Et3SiH (Table S2, Entry 4)
+ 40% SIPr·HClEt3SiH NaOtBu, toluene,
120 °C, 48 h
20% Ni(COD)2,
O
HO
99% The reaction was conducted according to the general procedure with Ni(COD)2 (8.3 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (28.6 mg, 6.69⋅10-2 mmol), NaOtBu (41.8 mg, 0.435 mmol),
dibenzofuran (25.2 mg, 0.150 mmol), Et3SiH (60 µl, 43.7 mg, 0.376 mmol), dodecane
(internal standard for GC, 9.4 mg) and toluene (0.3 ml) at 120 °C for 48 h. GC and
GC/MS analyses of the reaction mixture showed formation of 2-hydroxybiphenyl (m/z
170) in 99% yield. Et3SiOtBu (m/z 173 [M-Et]+) was the major silicon product.
Reductive cleavage of 4-methoxybiphenyl with DIBALH (Table S2, Entry 5)
OMe+
40% SIPr·HClDIBALH NaOtBu, toluene,
120 °C, 16 h
20% Ni(COD)2,
99%Ph Ph
The reaction was conducted according to the general procedure with Ni(COD)2 (8.7 mg,
3.2⋅10-2 mmol), SIPr⋅HCl (29.9 mg, 7.00⋅10-2 mmol), tBuONa (43.4 mg, 0.452 mmol), 4-
methoxybiphenyl (28.1 mg, 0.151 mmol), DIBALH (0.375 ml of 1M solution in
hexanes, 0.375 mmol), dodecane (internal standard for GC, 14 mg) and toluene (0.3 ml)
at 120 °C for 16 h. GC and GC/MS analyses of the reaction mixture showed complete
consumption of 4-methoxybiphenyl and formation of biphenyl (m/z 154) in 99% yield.
Reductive cleavage of 4-methoxybiphenyl with LiAl(OtBu)3H (Table S2, Entry 6)
OMe+
40% SIPr·HClLiAl(OtBu)3H NaOtBu, toluene,120 °C, 32 h
20% Ni(COD)2,
90%Ph Ph
The reaction was conducted according to the general procedure with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (25.8 mg, 6.04⋅10-2 mmol), NaOtBu (36.6 mg, 0.381 mmol), 4-
methoxybiphenyl (25.5 mg, 0.149 mmol), LiAl(OtBu)3H (95.3 mg, 0.371 mmol),
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
25
dodecane (internal standard for GC, 20 mg) and toluene (0.8 ml) at 120 °C for 32 h. GC
and GC/MS analyses of the reaction mixture showed formation of biphenyl (m/z 154) in
90% yield at 91% conversion of 4-methoxybiphenyl.
Reductive cleavage of 4-methoxybiphenyl with Et3SiH (Table S2, Entry 7)
OMe+
40% SIPr·HClEt3SiH NaOtBu, toluene,
140 °C, 56 h
20% Ni(COD)2,
89%Ph Ph
The reaction was conducted according to the general procedure with Ni(COD)2 (8.1 mg,
2.9⋅10-2 mmol), SIPr⋅HCl (27.2 mg, 6.36⋅10-2 mmol), NaOtBu (36.9 mg, 0.384 mmol), 4-
methoxybiphenyl (27.6 mg, 0.150 mmol), Et3SiH (600 µl, 437 mg, 3.76 mmol), dodecane
(internal standard for GC, 12.8 mg) and toluene (0.3 ml) at 140 °C for 56 h. GC and
GC/MS analyses of the reaction mixture showed the formation of benzene (m/z 78) in
89% yield at 91% conversion of 4-methoxybiphenyl. Et3SiOtBu (m/z 173 [M-Et]+) was
the major silicon product.
Reductive cleavage of anisole with DIBALH (Table S2, Entry 8)
OMe+
40% SIPr·HBF4DIBALH NaOtBu, toluene,
120 °C, 40 h
20% Ni(COD)2,
87% The reaction was conducted according to the general procedure with Ni(COD)2 (8.4 mg,
3.1⋅10-2 mmol), SIPr⋅HBF4 (30.1 mg, 6.29⋅10-2 mmol), tBuONa (43.4 mg, 0.452 mmol),
anisole (16.4 mg, 0.15 mmol), DIBALH (0.375 ml of 1M solution in hexanes, 0.375
mmol), dodecane (internal standard for GC, 10.9 mg) and toluene (0.3 ml) at 120 °C for
40 h. GC and GC/MS analyses of the reaction mixture showed the formation of benzene
(m/z 78) in 87% yield at 94% conversion of anisole.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
26
Reductive cleavage of anisole with LiAl(OtBu)3H (Table S2, Entry 9)
OMe+
40% SIPr·HClLiAl(OtBu)3H NaOtBu, toluene,120 °C, 32 h
20% Ni(COD)2,
62% The reaction was conducted according to the general procedure with Ni(COD)2 (8.4 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (26.8 mg, 5.60⋅10-2 mmol), NaOtBu (39.0 mg, 0.406 mmol),
anisole (16.4 mg, 0.151 mmol), LiAl(OtBu)3H (91.8 mg, 0.375 mmol), dodecane (internal
standard for GC, 11.9 mg) and toluene (0.8 ml) at 120 °C for 40 h. GC and GC/MS
analyses of the reaction mixture showed the formation of benzene (m/z 78) in 62% yield
at 85% conversion of anisole.
Reductive cleavage of anisole with Et3SiH (Table S2, Entry 10)
OMe+
40% IPrMe·HClEt3SiH NaOtBu, toluene,
140 °C, 96 h
20% Ni(COD)2,
77% The reaction was conducted according to the general procedure with Ni(COD)2 (8.0 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (27.2 mg, 6.36⋅10-2 mmol), NaOtBu (46.0 mg, 0.479 mmol),
anisole (17.8 mg, 0.165 mmol), Et3SiH (600 µl, 437 mg, 3.76 mmol), dodecane (internal
standard for GC, 12.8 mg) and toluene (0.3 ml) at 140 °C for 96 h. GC and GC/MS
analyses of the reaction mixture showed the formation of benzene (m/z 78) in 77% yield
at 84% conversion of anisole. Et3SiOtBu (m/z 173 [M-Et]+) was the major silicon
product.
Reductive cleavage of 1-methoxy-1-phenylpropane with DIBALH (Table S2,
Entry 11)
+ 40% SIPr·HClDIBALH NaOtBu, toluene,
120 °C, 16 h
20% Ni(COD)2,
94%
OMe
The reaction was conducted according to the general procedure with Ni(COD)2 (8.4 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (27.8 mg, 6.51⋅10-2 mmol), NaOtBu (38.3 mg, 0.499 mmol), 1-
methoxy-1-phenylpropane (23.3 mg, 0.155 mmol), DIBALH (0.240 ml of 1M solution
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
27
in hexanes, 0.240 mmol), dodecane (internal standard for GC, 11.5 mg) and toluene (0.3
ml) at 120 °C for 16 h. GC and GC/MS analyses of the reaction mixture showed
complete consumption of 1-methoxy-1-phenylpropane and formation of 1-phenylpropane
(m/z 120) in 94% yield.
Reductive cleavage of 1-methoxy-1-phenylpropane with LiAl(OtBu)3H (Table S2,
Entry 12)
+ 40% SIPr·HClLiAl(OtBu)3H NaOtBu, toluene,
120 °C, 56 h
20% Ni(COD)2,
91%
OMe
The reaction was conducted according to the general procedure with Ni(COD)2 (8.1 mg,
2.9⋅10-2 mmol), SIPr⋅HCl (26.0 mg, 6.09⋅10-2 mmol), NaOtBu (36.3 mg, 0.378 mmol), 1-
methoxy-1-phenylpropane (22.0 mg, 0.146 mmol), LiAl(OtBu)3H (95.7 mg, 0.376
mmol), dodecane (internal standard for GC, 8.8 mg) and toluene (0.8 ml) at 120 °C for 56
h. GC and GC/MS analyses of the reaction mixture showed the formation of 1-
phenylpropane (m/z 120) in 91% yield at 92% conversion of 1-methoxy-1-
phenylpropane.
Reductive cleavage of 4-tert-butylbenzyl phenyl ether with DIBALH (Table S2,
Entry 13)
+ 20% SIPr·HClDIBALH NaOtBu, toluene,
80 °C, 16 h
O +10% Ni(COD)2,
79% 15%tBu tBu
Me+ +tBu
OHHO
55%16% The reaction was conducted according to the general procedure with Ni(COD)2 (8.3 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (27.2 mg, 6.37⋅10-2 mmol), NaOtBu (39.0 mg, 0.406 mmol), 4-
tert-butylbenzyl phenyl ether (36.1 mg, 0.150 mmol), DIBALH (0.210 ml of 1M
solution in hexanes, 0.210 mmol), dodecane (internal standard for GC, 12.6 mg) and
toluene (0.3 ml) at 80 °C for 16 h. GC and GC/MS analyses of the reaction mixture
showed complete consumption of 4-tert-butylbenzyl phenyl ether and formation of 4-
tert-butyltoluene (m/z 148), benzene (m/z 78), phenol (m/z 94), and 4-tert-butylbenzyl
alcohol (m/z 164) in 79%, 15%, 16% and 55% yields respectively.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
28
Reductive cleavage of 4-tert-butylbenzyl phenyl ether with LiAl(OtBu)3H (Table S2,
Entry 14)
+ 20% SIPr·HClLiAl(OtBu)3H NaOtBu, toluene,
80 °C, 32 h
O +10% Ni(COD)2,
82% 99%tBu tBu
Me HO
The reaction was conducted according to the general procedure with Ni(COD)2 (8.4 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (26.9 mg, 6.29⋅10-2 mmol), NaOtBu (36.5 mg, 0.380 mmol), 4-
tert-butylbenzyl phenyl ether (36.1 mg, 0.150 mmol), LiAl(OtBu)3H (92.2 mg, 0.363
mmol), dodecane (internal standard for GC, 36.9 mg) and toluene (0.3 ml) at 80 °C for 32
h. GC and GC/MS analyses of the reaction mixture showed complete consumption of 4-
tert-butylbenzyl phenyl ether and formation of 4-tert-butyltoluene (m/z 148), and phenol
(m/z 94) in 82% and 99% yields respectively.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
29
6. Nickel-NHC Catalyzed Selective Hydrogenolysis of Aryl and Benzyl Ethers
Reactions were conducted in 15 ml Schlenk tubes (exact volume 14.8 ml, outer diameter
of the tube 16 mm) equipped with Teflon-stopcocks and Teflon-coated magnetic stir bars
(3 mm × 10 mm; supplied by Fisher Scientific). The reported pressure of hydrogen refers
to the readings from the gauge of the gas cylinder at room temperature. The reaction
tubes were heated in an oil bath; the reaction temperature refers to the temperature of the
oil bath.
General Procedure A
In a glovebox, a 15 ml Schlenk tube equipped with a Teflon-stopcock was charged with
Ni(COD)2 (0.75⋅10-2-3.0⋅10-2 mmol, 5-20 mol%), SIPr⋅HCl (1.5⋅10-2- 6.0⋅10-2 mmol, 10-
40 mol%), NaOtBu (0.375 mmol) and a magnetic stir bar. Then a solution of aryl or
benzyl ether (0.15 mmol) and dodecane internal standard for GC) in m-xylene (0.8 ml)
were added, and the mixture was stirred for 3 min. The Schlenk tube was sealed with the
Teflon stopcock and removed form the glovebox. The reaction mixture was degassed via
two cycles of freeze-pump-thaw and the tube was pressurized with 1 bar (15 psi) of
hydrogen at room temperature; saturation with hydrogen leads to slightly noticeable
change in color from dark brown to dark red brown. The tube was sealed with the Teflon
stopcock and heated in an oil bath at 80, 100 or 120 °C for 16-48 h. The resulting dark
brown to black mixture was cooled to room temperature, diluted with ether (1 ml) and
quenched with 1.5 M aqueous HCl (1 ml) followed by stirring for 15 min. The organic
layer was separated and the aqueous layer was extracted with 1 ml of ether. The
combined organic layers were passed through a short pad of Celite and subjected to GC
and GC/MS analyses. The products were all known compounds and were identified using
GC/MS and GC by comparison of the mass spectra and retention times of the products
with those of commercially available authentic compounds.
General Procedure B (Hydrogenolysis in the Presence of 1 equiv. of AlMe3)
The procedure is similar to General Procedure A, but includes addition of AlMe3 (2 M in
toluene, 75 µl, 0.15 mmol) after mixing of all reagents and stirring for 3 min.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
30
Hydrogenolysis of diphenyl ether (Table 1, Entry 1)
O+
40% SIPr·HClH2 NaOtBu, m-xylene,
120 °C, 16 h+
HO20% Ni(COD)2,
99% 99%(1 bar at rt)
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.3 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (27.8 mg, 6.51⋅10-2 mmol), NaOtBu (37.2 mg, 0.387 mmol),
diphenyl ether (26.4 mg, 0.155 mmol), dodecane (internal standard for GC, 8.8 mg) and
m-xylene (0.8 ml) at 120 °C for 16 h. GC and GC/MS analyses of the reaction mixture
showed the formation of benzene (78 m/z) and phenol (94 m/z) in 99% and 99% yields
respectively at full conversion of diphenyl ether. Hydrogenolysis with SIPr⋅HBF4 as a
ligand precursor led to the identical product yields.
Hydrogenolysis of diphenyl ether (Table 1, Entry 2) O
+ 20% SIPr·HClH2 NaOtBu, m-xylene,
120 °C, 32 h+
HO10% Ni(COD)2,
82% 87%(1 bar at rt)
The reaction was conducted according to General Procedure A with Ni(COD)2 (4.3 mg,
1.6⋅10-2 mmol), SIPr⋅HCl (13.3 mg, 3.11⋅10-2 mmol), NaOtBu (38.6 mg, 0.402 mmol),
diphenyl ether (26.0 mg, 0.152 mmol), dodecane (internal standard for GC, 10 mg) and
m-xylene (0.8 ml) at 120 °C for 32 h. GC analysis of the reaction mixture showed the
formation of benzene and phenol in 82% and 87% yields respectively at 87% conversion
of diphenyl ether.
Hydrogenolysis of diphenyl ether (Table 1, Entry 3) O
+ 10% SIPr·HClH2 NaOtBu, m-xylene,120 °C, 32 h
+HO5% Ni(COD)2,
59% 54%(1 bar at rt)
The reaction was conducted according to General Procedure A with Ni(COD)2 (2.2 mg,
0.8⋅10-2 mmol), SIPr⋅HCl (6.9 mg, 1.6⋅10-2 mmol), NaOtBu (43.0 mg, 0.447 mmol),
diphenyl ether (25.3 mg, 0.149 mmol), dodecane (internal standard for GC, 14.5 mg) and
m-xylene (0.8 ml) at 120 °C for 32 h. GC analysis of the reaction mixture showed the
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
31
formation of benzene and phenol in 59% and 54% yields respectively at 59% conversion
of diphenyl ether.
Hydrogenolysis of di-3-methylphenyl ether (Table 1, Entry 4) O
+ 40% SIPr·HClH2 NaOtBu, m-xylene,
120 °C, 16 h+
HO20% Ni(COD)2,
96% 99%(1 bar at rt) Me
Me Me Me
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (29.3 mg, 6.86⋅10-2 mmol), NaOtBu (39.1 mg, 0.407 mmol), di-
3-methylphenyl ether (30.6 mg, 0.154 mmol), dodecane (internal standard for GC, 35.6
mg) and m-xylene (0.8 ml) at 120 °C for 16 h. GC and GC/MS analyses of the reaction
mixture showed the formation of toluene (92 m/z) and 3-methylphenol (108 m/z) in 96%
and 99% yields respectively at full conversion of di-3-methylphenyl ether.
Hydrogenolysis of di-3-methoxyphenyl ether (Table 1, Entry 5) O
+ 40% SIPr·HClH2 NaOtBu, m-xylene,
120 °C, 16 h+HO20% Ni(COD)2,
65% 83%(1 bar at rt) MeO
MeO OMe OMe+
23%
+HO
3%
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (29.3 mg, 6.81⋅10-2 mmol), NaOtBu (39.1 mg, 0.407 mmol), di-
3-methoxyphenyl ether (36.3 mg, 0.158 mmol), dodecane (internal standard for GC, 45.3
mg) and m-xylene (0.8 ml) at 120 °C for 16 h. GC and GC/MS analyses of the reaction
mixture showed the formation of anisole (108 m/z), 3-methoxylphenol (124 m/z),
benzene (78 m/z) and phenol (94 m/z) in 65%, 83%, 23% and 3% yields respectively at
94% conversion of di-3-methoxyphenyl ether.
Hydrogenolysis of di-4-methylphenyl ether (Table 1, Entry 6) O
+ 40% SIPr·HClH2 NaOtBu, m-xylene,
120 °C, 48 h+
HO20% Ni(COD)2,
97% 99%(1 bar at rt) MeMeMe Me
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.6 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (26.7 mg, 6.25⋅10-2 mmol), NaOtBu (39.8 mg, 0.414 mmol), di-
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
32
4-methylphenyl ether (30.1 mg, 0.152 mmol), dodecane (internal standard for GC, 48.2
mg) and m-xylene (0.8 ml) at 120 °C for 48 h. GC and GC/MS analyses of the reaction
mixture showed the formation of toluene (92 m/z) and 4-methylphenol (108 m/z) in 97%
and 99% yields respectively at full conversion of di-4-methylphenyl ether.
Hydrogenolysis of di-4-tert-butylphenyl ether (Table 1, Entry 7) O
+ 40% SIPr·HClH2 NaOtBu, m-xylene,
120 °C, 48 h+
HO20% Ni(COD)2,
72% 73%(1 bar at rt) tButButBu tBu
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.3 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (25.5 mg, 5.97⋅10-2 mmol), NaOtBu (38.5 mg, 0.401 mmol), di-
4-tert-butylphenyl ether (43.3 mg, 0.153 mmol), dodecane (internal standard for GC) and
m-xylene (0.8 ml) at 120 °C for 48 h. GC and GC/MS analyses of the reaction mixture
showed the formation of tert-butylbenzene (134 m/z) and 4-tert-butylphenol (150 m/z) in
72% and 73% yields respectively at 74% conversion of di-4-tert-butylphenyl ether.
Hydrogenolysis of phenyl 4-trifluoromethylphenyl ether (Table 1, Entry 8) O
+ 20% SIPr·HClH2 NaOtBu, m-xylene,
100 °C, 16h+HO10% Ni(COD)2,
(1 bar at rt) 64% 99%
+
4%F3C F3C
23%H3C+
The reaction was conducted according to General Procedure A with Ni(COD)2 (4.3 mg,
1.6⋅10-2 mmol), SIPr⋅HCl 13.4 mg, 3.13⋅10-2 mmol), NaOtBu (40.0 mg, 0.416 mmol),
phenyl 4-trifluoromethylphenyl ether (35.8 mg, 0.150 mmol), dodecane (41 mg, internal
standard for GC) and m-xylene (0.8 ml) at 100 °C for 16 h. GC and GC/MS analyses of
the reaction mixture showed the formation of trifluoromethylbenzene (146 m/z), phenol
(94 m/z) and benzene (78 m/z) in 64%, 99% and 4% yields respectively at full conversion
of 4-trifluoromethylphenyl ether. Toluene (92 m/z) was observed as a side product
(23%).
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
33
Hydrogenolysis of 4-methoxyphenyl 4-trifluoromethylphenyl ether (Table 1,
Entry 9)
19%Me
+O
+ 20% SIPr·HClH2 NaOtBu, m-xylene,
100 °C, 16h+HO10% Ni(COD)2,
(1 bar at rt) 68% 92%F3C F3COMe OMe
The reaction was conducted according to General Procedure A with Ni(COD)2 (4.2 mg,
1.5⋅10-2 mmol), SIPr⋅HCl (12.8 mg, 3.00⋅10-2 mmol), NaOtBu (40.1 mg, 0.417 mmol), 4-
methoxyphenyl 4-trifluoromethylphenyl ether (40.0 mg, 0.149 mmol), dodecane (internal
standard for GC, 36.0 mg) and m-xylene (0.8 ml) at 100 °C for 16 h. GC and GC/MS
analyses of the reaction mixture showed the formation of trifluoromethylbenzene (146
m/z) and 4-methoxyphenol (124 m/z) in 68% and 92% yields respectively at full
conversion of 4-methoxyphenyl 4-trifluoromethylphenyl ether. Toluene (m/z 92) was
observed as a side product (19%).
Hydrogenolysis of 4-methoxyphenyl phenyl ether (Table 1, Entry 10)
4%OMe
+O
+ 40% SIPr·HClH2 NaOtBu, m-xylene,
120 °C, 16h+HO20% Ni(COD)2,
(1 bar at rt) 88% 80%OMe OMe
+OH
17% The reaction was conducted according to General Procedure A with Ni(COD)2 (8.6 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (26.4 mg, 6.18⋅10-2 mmol), NaOtBu (35.5 mg, 0.369 mmol), 4-
methoxyphenyl phenyl ether (30.4 mg, 0.152 mmol), dodecane (internal standard for GC,
44.6 mg) and m-xylene (0.8 ml) at 120 °C for 16 h. GC and GC/MS analyses of the
reaction mixture showed the formation of benzene (78 m/z), 4-methoxyphenol (124 m/z),
phenol (94 m/z) and anisole (108) in 88%, 80%, 17% and 4% yield respectively at full
conversion of 4-methoxyphenyl phenyl ether.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
34
Hydrogenolysis of di-2-methylphenyl ether (Table 1, Entry 11)
O+
40% SIPr·HClH2 NaOtBu, m-xylene,
120 °C, 32 h+
HO20% Ni(COD)2,
85% 85%(1 bar at rt)
Me MeMe Me
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.4 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (26.0 mg, 6.09⋅10-2 mmol), NaOtBu (37.9 mg, 0.394 mmol), di-
2-methylphenyl ether (29.6 mg, 0.149 mmol), dodecane (internal standard for GC, 29.
mg) and m-xylene (0.8 ml) at 120 °C for 32 h. GC and GC/MS analyses of the reaction
mixture showed the formation of toluene (92 m/z) and 2-methylphenol (108 m/z) in 85%
and 85% yields respectively at 85% conversion of di-2-methylphenyl ether.
Hydrogenolysis of 2-n-hexyloxynaphthalene (Table 2, Entry 1)
+20% Ni(COD)2, 40% SIPr·HClH2 NaOtBu, m-xylene,120 °C, 16h(1 bar at rt)
95%
O+ HO
98%
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (25.8 mg, 6.04⋅10-2 mmol), NaOtBu (37.4 mg, 0.389 mmol), 2-
n-hexyloxynaphthalene (33.9 mg, 0.148 mmol), dodecane (internal standard for GC, 36.7
mg) and m-xylene (0.8 ml) at 120 °C for 16 h. GC and GC/MS analyses of the reaction
mixture showed the formation of naphthalene (m/z 128) in 95% yield at full conversion
of 2-n-hexyloxynaphthalene. 1,2,3,4-Tetrahydronaphthalene (m/z 132) was detected as a
side product in trace amounts (1%). To quantify by GC and GC/MS the amount of 1-
hexanol formed in the reaction mixture, the alcohol was converted to (n-
hexyloxy)trimethylsilane using the following derivatization protocol. The reaction
mixture after work up was passed through a short plug of anhydrous sodium sulfate and
mixed with MSTFA (N-methy-N-(trimethylsilyl)trifluoroacetamide, 100 µl). The
solution was stirred at 60 °C for 1 h, cooled to room temperature, and analyzed by GC
and GC/MS. This method showed the formation of (n-hexyloxy)trimethylsilane (m/z 159,
[M-Et] +) in 98% yield based on the amount of starting 2-n-hexyloxynaphthalene.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
35
Hydrogenolysis of 2-methoxynaphthalene (Table 2, Entry 2)
+20% Ni(COD)2, 40% SIPr·HClH2 NaOtBu, m-xylene,120 °C, 16h(1 bar at rt)
89%
OMe+ MeOH
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (27.5 mg, 6.43⋅10-2 mmol), NaOtBu (37.5 mg, 0.390 mmol), 2-
methoxynaphthalene (23.5 mg, 0.149 mmol), dodecane (internal standard for GC, 8.9
mg) and m-xylene (0.8 ml) at 100 °C for 16 h. GC and GC/MS analyses of the reaction
mixture showed the formation of naphthalene (m/z 128) in 89% yield at 89% conversion
of 2-methoxynaphthalene. Methanol was detected by GC as a second product. A second
run gave naphthalene in 85% yield at 88% conversion.
Hydrogenolysis of 2-methoxynaphthalene in the presence of AlMe3 at 80 °C (Table
2, Entry 3)
+20% Ni(COD)2, 40% SIPr·HClH2 NaOtBu, AlMe3,m-xylene, 80 °C,(1 bar at rt)
98%16h
OMe
The reaction was conducted according to General Procedure B with Ni(COD)2 (8.3 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (25.9 mg, 6.07⋅10-2 mmol), NaOtBu (37.9 mg, 0.394 mmol), 2-
methoxynaphthalene (23.9 mg, 0.151 mmol), AlMe3 (2M solution in toluene, 75 µl,
0.150 mmol), dodecane (internal standard for GC, 25.8 mg) and m-xylene (0.8 ml) at 80
°C for 16 h. GC and GC/MS analyses of the reaction mixture showed the formation of
naphthalene (m/z 128) in 98% yield at full conversion of 2-methoxynaphthalene.
Hydrogenolysis of 2-methoxynaphthalene in the presence of AlMe3 at 100 °C
+20% Ni(COD)2, 40% SIPr·HClH2 NaOtBu, AlMe3,m-xylene, 100 °C,(1 bar at rt)
95%16h
OMe
The reaction was conducted according to General Procedure B with Ni(COD)2 (8.4 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (29.0 mg, 6.79⋅10-2 mmol), NaOtBu (38.8 mg, 0.404 mmol), 2-
methoxynaphthalene (23.9 mg, 0.151 mmol), AlMe3 (2M solution in toluene, 75 µl, 0.15
mmol), dodecane (internal standard for GC, 10.3 mg) and m-xylene (0.8 ml) at 100 °C for
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
36
16 h. GC and GC/MS analyses of the reaction mixture showed the formation of
naphthalene (m/z 128) in 95% yield at full conversion of 2-methoxynaphthalene. 2-
methylnaphthalene (m/z 142) was observed as a side product in 3% yield.
Hydrogenolysis of 1-methoxynaphthalene (Table 2, Entry 4)
+20% Ni(COD)2, 40% SIPr·HClH2 NaOtBu, m-xylene,120 °C, 16h(1 bar at rt)
OMe
72%
+ MeOH
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (26.8 mg, 6.28⋅10-2 mmol), NaOtBu (36.8 mg, 0.383 mmol), 1-
methoxynaphthalene (24.0 mg, 0.152 mmol), dodecane (internal standard for GC, 19.8
mg) and m-xylene (0.8 ml) at 100 °C for 16 h. Toluene was used as a solvent for work
up. GC and GC/MS analyses of the reaction mixture showed the formation of
naphthalene (m/z 128) in 72% yield at 72 % conversion of 1-methoxynaphthalene.
Methanol was detected by GC as a second product. A second run gave 72% of
naphthalene at 72% conversion.
Hydrogenolysis of 1-methoxynaphthalene in the presence of AlMe3 (Table 2, Entry
5)
+20% Ni(COD)2, 40% SIPr·HClH2 NaOtBu, AlMe3,m-xylene, 100 °C,(1 bar at rt)
OMe
99%16h The reaction was conducted according to General Procedure B with Ni(COD)2 (8.1 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (26.8 mg, 6.27⋅10-2 mmol), NaOtBu (39.3 mg, 0.409 mmol), 1-
methoxynaphthalene (22.9 mg, 0.145 mmol), AlMe3 (2M solution in toluene, 75 µl, 0.15
mmol), dodecane (internal standard for GC, 37.2 mg) and m-xylene (0.8 ml) at 100 °C for
16 h. GC and GC/MS analyses of the reaction mixture showed the formation of
naphthalene (m/z 128) in 99% yield at full conversion of 1-methoxynaphthalene.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
37
Hydrogenolysis of 4-methoxybiphenyl (Table 2, Entry 6)
+20% Ni(COD)2, 40% SIPr·HClH2 NaOtBu, m-xylene,120 °C, 32 h(1 bar at rt)
85%
O+ HO
85%Ph Ph
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (27.0 mg, 6.32⋅10-2 mmol), NaOtBu (36.5 mg, 0.380 mmol), 4-
n-hexyloxybiphenyl (38.3 mg, 0.151 mmol), dodecane (internal standard for GC, 43.0
mg) and m-xylene (0.8 ml) at 120 °C for 32 h. GC and GC/MS analyses of the reaction
mixture showed the formation of biphenyl (m/z 154) in 85% yield at 85% conversion of
4-n-hexyloxybiphenyl. The second product, n-hexanol (85%) was detected by GC and
GC/MS after conversion to (n-hexyloxy)trimethylsilane (m/z 159, [M-Et] +) by treatment
of the crude reaction mixture with N-methy-N-(trimethylsilyl)trifluoroacetamide
(MSTFA); see derivatization protocol described in the procedure for the hydrogenolysis
of 2-n-hexyloxynaphthalene on p. 34.
Hydrogenolysis of 4-methoxybiphenyl (Table 2, Entry 7)
+20% Ni(COD)2, 40% SIPr·HClH2 NaOtBu, m-xylene,120 °C, 32 h(1 bar at rt)
59%
OMe
PhPh+ MeOH
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.6 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (27.9 mg, 6.53⋅10-2 mmol), NaOtBu (39.5 mg, 0.411 mmol), 4-
methoxybiphenyl (27.9 mg, 0.152 mmol), dodecane (internal standard for GC, 23.4 mg)
and m-xylene (0.8 ml) at 120 °C for 16 h. Toluene was used as a solvent for work up. GC
and GC/MS analyses of the reaction mixture showed the formation of biphenyl (m/z 154)
in 59% yield at 60% conversion of 4-methoxybiphenyl. Methanol was detected as a
second product. A second run gave 57% of biphenyl at 57% conversion.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
38
Hydrogenolysis of 4-methoxybiphenyl in the presence of AlMe3 (Table 2, Entry 8) 20% Ni(COD)2, 40% SIPr·HClNaOtBu, AlMe3,m-xylene, 100 °C,
32 h
+ H2(1 bar at rt)
65%
OMe
PhPh
The reaction was conducted according to General Procedure B with Ni(COD)2 (8.4 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (25.9 mg, 6.06⋅10-2 mmol), NaOtBu (38.9 mg, 0.405 mmol), 4-
methoxybiphenyl (28.3 mg, 0.154 mmol), AlMe3 (2M solution in toluene, 75 µl, 0.15
mmol), dodecane (internal standard for GC, 37.1 mg) and m-xylene (0.8 ml) at 100 °C for
16 h. GC and GC/MS analyses of the reaction mixture showed the formation of biphenyl
(m/z 154) in 65% yield at 65% conversion of 4-methoxybiphenyl. A second run
conducted at 120 °C for 32 h gave 62% of biphenyl at 68% conversion.
Hydrogenolysis of 4-tert-butylbenzyl phenyl ether (Table 3, Entry 1)
H2
(1 bar at rt)+ NaOtBu, m-xylene,
120 °C, 16 h
20 mol% SIPr·HCl
99% 93%
10 mol% Ni(COD)2,O
tBu
Me
tBu+
HO
The reaction was conducted according to General Procedure A with Ni(COD)2 (4.4 mg,
1.6⋅10-2 mmol), SIPr⋅HCl (14.4 mg, 3.37⋅10-2 mmol), NaOtBu (37.2 mg, 0.387 mmol), 4-
tert-butylbenzyl phenyl ether (36.1 mg, 0.150 mmol), dodecane (internal standard for
GC, 20.4 mg) and m-xylene (0.8 ml) at 100 °C for 16 h. GC and GC/MS analyses of the
reaction mixture showed the formation of 4-tert-butyltoluene (m/z 148) and phenol (m/z
94) in 99% and 93% yields at full conversion of 4-tert-butylbenzyl phenyl ether.
Hydrogenolysis of 4-tert-butylbenzyl methyl ether (Table 3, Entry 2)
+ MeOHH2
(1 bar at rt)+
NaOtBu, m-xylene,120 °C, 16 h
40 mol% SIPr·HCl20 mol% Ni(COD)2,
OMetBu
Me
tBuX
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.3 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (27.5 mg, 6.43⋅10-2 mmol), NaOtBu (38.8 mg, 0.404 mmol), 4-
tert-butylbenzyl methyl ether (27.9 mg, 0.157 mmol), dodecane (internal standard for
GC, 25.4 mg) and m-xylene (0.8 ml) at 120 °C for 16 h. GC analysis of the reaction
mixture showed 1% conversion of 4-tert-butylbenzyl methyl ether.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
39
Hydrogenolysis of 4-tert-butylbenzyl methyl ether in the presence of AlMe3 (Table 3,
Entry 3)
H2
(1 bar at rt)+
40 mol% SIPr·HCl20 mol% Ni(COD)2,
OMetBu
Me
tBuNaOtBu, AlMe3,m-xylene, 120 °C,
32 h 99% The reaction was conducted according to General Procedure B with Ni(COD)2 (8.3 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (27.3 mg, 6.39⋅10-2 mmol), NaOtBu (36.4 mg, 0.378 mmol), 4-
tert-butylbenzyl methyl ether (27.2 mg, 0.153 mmol), AlMe3 (2M solution in toluene, 75
µl, 0.15 mmol), dodecane (internal standard for GC, 18.2 mg) and m-xylene (0.8 ml) at
120 °C for 32 h. GC analysis of the reaction mixture showed the formation of 4-tert-
butyltoluene (m/z 148) in 99% yield at full conversion of 4-tert-butylbenzyl methyl ether.
Hydrogenolysis of 4-tert-butylbenzyl methyl ether in the presence of AlMe3 and in
the absence of Ni(COD)2
H2
(1 bar at rt)+
40 mol% SIPr·HClOMetBu
Me
tBuNaOtBu, AlMe3,m-xylene, 120 °C,
32 h
X
The reaction was conducted according to General Procedure B with SIPr⋅HCl (26.9 mg,
6.23⋅10-2 mmol), NaOtBu (36.7 mg, 0.382 mmol), 4-tert-butylbenzyl methyl ether (26.3
mg, 0.148 mmol), AlMe3 (2M solution in toluene, 75 µl, 0.15 mmol), dodecane (internal
standard for GC, 33.6 mg) and m-xylene (0.8 ml) at 120 °C for 32 h. GC analysis of the
reaction mixture showed no conversion of 4-tert-butylbenzyl methyl ether.
Hydrogenolysis of 1-methoxy-1-phenylpropane (Table 3, Entry 4)
H2
(1 bar at rt)+
NaOtBu, m-xylene,120 °C, 16 h
40 mol% SIPr·HCl20 mol% Ni(COD)2,
XEt
OMe
Et
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (25.9 mg, 6.07⋅10-2 mmol), NaOtBu (36.5 mg, 0.380 mmol), 1-
methoxy-1-phenylpropane (22.8 mg, 0.152 mmol), dodecane (internal standard for GC,
22.8 mg) and m-xylene (0.8 ml) at 120 °C for 16 h. GC analysis of the reaction mixture
showed no conversion of 1-methoxy-1-phenylpropane.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
40
Hydrogenolysis of 1-methoxy-1-phenylpropane in the presence of AlMe3 (Table 3,
Entry 5)
20% Ni(COD)2, 40% SIPr·HClNaOtBu, AlMe3,m-xylene, 120 °C,
16h
H2
(1 bar at rt)+Et
OMe
Et
96% The reaction was conducted according to General Procedure B with Ni(COD)2 (8.6 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (29.4 mg, 6.88⋅10-2 mmol), NaOtBu (37.4 mg, 0.389 mmol), 1-
methoxy-1-phenylpropane (23.6 mg, 0.157 mmol), AlMe3 (2M solution in toluene, 75 µl,
0.15 mmol), dodecane (internal standard for GC, 34.1 mg) and m-xylene (0.8 ml) at 120
°C for 16 h. GC analysis of the reaction mixture showed the formation of 1-
propylbenzene (m/z 120) in 96% yield at full conversion of 1-methoxy-1-phenylpropane.
A second run gave 99% of 1-propylbenzene at full conversion of 1-methoxy-1-
phenylpropane.
Hydrogenolysis of bis(m-phenoxyphenyl)benzene (Fig. 3A) O O
+HO
+HO OH
1 equiv. 1.9 equiv. 1.7 equiv.0.3 equiv.
+ H2 NaOtBu, m-xylene,120 °C, 16 h
(1 bar at rt)
Ni(COD)2/SIPr·HCl +HO OPh
0.09 equiv.
O O
The reaction was conducted according to General Procedure A with Ni(COD)2 (11 mg,
4.0⋅10-2 mmol), SIPr⋅HCl (34.9 mg, 8.17⋅10-2 mmol), NaOtBu (49.6 mg, 0.516 mmol),
bis(m-phenoxyphenyl)benzene (24.7 mg, 5.53⋅10-2 mmol), dodecane (internal standard
for GC, 22.1 mg) and m-xylene (0.8 ml) at 120 °C for 16 h. TLC probe of the reaction
mixture showed full conversion of bis(m-phenoxyphenyl)benzene. GC and GC/MS
analyses of the reaction mixture showed the formation of benzene (1.9 equiv., m/z 78),
1,3-dimethoxybenzene (0.3 equiv., m/z 110), phenol (1.7 equiv., m/z 94) and 3-
phenoxyphenol (0.09 equiv., m/z 186).
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
41
Hydrogenolysis of Lignin Model Compounds
Hydrogenolysis of di-2-methoxyphenyl ether (Fig. 3B)
O+ H2 +
HO
(1 bar at rt)+
OMeOMe
47% 66% 15%
OMe OMe
40% SIPr·HClNaOtBu, toluene,
120 °C, 16 h
20% Ni(COD)2,
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.3 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (25.9 mg, 6.07⋅10-2 mmol), NaOtBu (37.5 mg, 0.390 mmol), di-
2-methoxyphenyl ether (36.0 mg, 0.156 mmol), dodecane (internal standard for GC, 36.1
mg) and m-xylene (0.8 ml) at 120 °C for 48 h. GC and GC/MS analyses of the reaction
mixture showed the formation of anisole (108 m/z), 2-methoxylphenol (124 m/z) and
benzene (78 m/z) in 47%, 66%, and 15% yields respectively at 75% conversion of di-2-
methoxyphenyl ether.
Hydrogenolysis of 2-methoxyphenyl phenyl ether (Fig. 3B)
O+ H2 +
HO
(1 bar at rt)+
OMeOMe
+OH
OMe
63% 68% 22% 19%
40% SIPr·HClNaOtBu, toluene,
120 °C, 16 h
20% Ni(COD)2,
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.3 mg,
3.2⋅10-2 mmol), SIPr⋅HCl (27.3 mg, 6.39⋅10-2 mmol), NaOtBu (42.7 mg, 0.444 mmol), 2-
methoxyphenyl phenyl ether (32 mg, 0.160 mmol), dodecane (internal standard for GC,
40.6 mg) and m-xylene (0.8 ml) at 120 °C for 16 h. GC and GC/MS analyses of the
reaction mixture showed the formation of benzene (78 m/z), 2-methoxylphenol (124
m/z), phenol (94 m/z) and anisole (108 m/z) in 63%, 68%, 22% and 19% yields
respectively at 98% conversion of 2-methoxyphenyl phenyl ether.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
42
Hydrogenolysis of 3,4-dimethoxybenzyl 2-methoxyphenyl ether (Fig. 3C)
MeO
O H2
(1 bar)
+HO
+MeO
MeO
MeMeO MeO
MeO
99% 99%
10% SIPr·HClNaOtBu, toluene,
80 °C, 16 h
5% Ni(COD)2,
The reaction was conducted according to General Procedure A with Ni(COD)2 (2.2 mg,
0.80⋅10-2 mmol), SIPr⋅HCl (6.5 mg, 1.5⋅10-2 mmol), NaOtBu (37.5 mg, 0.390 mmol), di-
3,4-dimethoxybenzyl 2-methoxyphenyl ether (41.9 mg, 0.153 mmol), dodecane (internal
standard for GC, 17.4 mg) and m-xylene (0.8 ml) at 80 °C for 16 h. GC and GC/MS
analyses of the reaction mixture showed the formation of 1,2-dimethoxy-4-
methylbenzene (152 m/z) and 2-methoxylphenol (124 m/z) in 99% yields for both
products at full conversion of 3,4-dimethoxybenzyl 2-methoxyphenyl ether.
Cleavage of 1-(3,4-Dimethoxyphenyl)-2-(2-methoxyphenoxy)-l,3-propanediol with
NaOtBu in the absence of the nickel catalyst (Fig. 3D)
OOMe OH
OMe
OMe
HONaOtBu, toluene,
100 °C, 2 h
OMeOH
89% A 4 ml screw cap vial was charged with NaOtBu (37.5 mg, 0.390 mmol), di-1-(3,4-
dimethoxyphenyl)-2-(2-methoxyphenoxy)-l,3-propanediol (51.7 mg, 0.154 mmol),
dodecane (internal standard for GC, 32.6 mg), toluene (0.8 ml) and a magnetic stir bar.
After stirring for 5 min at room temperature, the reaction mixture was heated to 100 °C
and stirred for 2 h. The resulting red-brown suspension was cooled to room temperature,
diluted with ether (1 ml) and stirred with 1.5 M aqueous HCl (1 ml). The organic layer
was separated and the aqueous layer was extracted with ether (1 ml). The combined
organic layers were subjected to GC and GC/MS analyses, which showed the formation
of 2-methoxylphenol (124 m/z) in 89% yield. LC-MS of the reaction mixture showed the
formation of numerous products in addition to 2-methoxylphenol. Formation of 2-
methoxylphenol was reported for alkaline hydrolysis of this lignin model
compound (25—27).
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
43
Competition experiments
Selective hydrogenolysis of diphenyl ether in the presence of 4-tert-butylbenzyl
methyl ether (16 h, Fig. 2B)
+ 40% SIPr HClNaOtBu, toluene,
120 °C, 16 h
O+ +
(1 equiv)(1 equiv) (1 bar at rt)
99%Conversions
100% 1%Yields
tBu
20% Ni(COD)2,
+HO
99%
OMe H2
0%
tBu
Me
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (28.1 mg, 6.58⋅10-2 mmol), NaOtBu (36.9 mg, 0.384 mmol),
diphenyl ether (25.2 mg, 0.148 mmol), 4-tert-butylbenzyl methyl ether (26.8 mg, 0.150
mmol), dodecane (internal standard for GC, 25.4 mg) and m-xylene (0.8 ml) at 120 °C for
16 h. GC analysis of the reaction mixture showed full conversion of diphenyl ether and
formation of benzene and phenol in quantitative yields (99%), whereas 4-tert-butylbenzyl
methyl ether remained unreacted (conversion 1%) and no 4-tert-butyltoluene was
detected.
Selective hydrogenolysis of 2-methoxynaphthalene in the presence 4-tert-butylbenzyl
methyl ether (Fig. 3C)
+ +
(1 equiv)(1 equiv) (1 bar at rt)
86%Conversions
87% 1%Yields
tBu+OMe H2
0%
tBu
MeOMe40% SIPr HCl
NaOtBu, m-xylene,120 °C, 16 h
20% Ni(COD)2,
The reaction was conducted according to General Procedure A with Ni(COD)2 (8.7 mg,
3.2⋅10-2 mmol), SIPr⋅HCl (28.4 mg, 6.65⋅10-2 mmol), NaOtBu (37.7 mg, 0.393 mmol), 2-
methoxynaphthalene (24.0 mg, 0.152 mmol), 4-tert-butylmethoxybenzene (27.2 mg,
0.153 mmol), dodecane (internal standard for GC, 17.1 mg) and m-xylene (0.8 ml) at 120
°C for 16 h. GC and GC/MS analyses of the reaction mixture showed 87% conversion of
2-methoxynaphthalene (m/z 158) and formation of naphthalene (mz 128) in 86% yield;
only 1% of 4-tert-butylbenzyl methyl ether (m/z 178) was consumed, and no tert-
butyltoluene was detected.
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
44
The same reaction at 100 °C for 16 h formed naphthalene in 58% yield at 58%
conversion of 2-methoxynaphtalene; no tert-butyltoluene was detected, and the
conversion of 4-tert-butylbenzyl methyl ether was about 1%.
Selective hydrogenolysis of 2-methoxynaphthalene in the presence 4-tert-butylbenzyl
methyl ether and 1 equiv of AlMe3 (Fig. 3C)
+ +
(1 equiv)(1 equiv) (1 bar at rt)Conversions Yields
tBu+OMe H2tBu
MeOMe
97%100% 1% 1%
40% SIPr HCl,
NaOtBu, m-xylene,80 °C, 16 h
20% Ni(COD)2,
AlMe3 (1 equiv.)
The reaction was conducted according to General Procedure B with Ni(COD)2 (8.3 mg,
3.0⋅10-2 mmol), SIPr⋅HCl (28.3 mg, 6.63⋅10-2 mmol), NaOtBu (38.8 mg, 0.403 mmol), 2-
methoxynaphthalene (24.9 mg, 0.157 mmol), 4-tert-butylmethoxybenzene (26.8 mg,
0.150 mmol), AlMe3 (2M solution in toluene, 75 µl, 0.15 mmol), dodecane (internal
standard for GC, 20.6 mg) and m-xylene (0.8 ml) at 80 °C for 16 h. GC and GC/MS
analyses of the reaction mixture showed full conversion of 2-methoxynaphthalene and
formation of naphthalene (m/z 128) in 97% yield; 1% of the starting 4-tert-butylbenzyl
methyl ether (m/z 178) was consumed to give tert-butyltoluene (m/z 148) in trace
amounts (1%).
Selective hydrogenolysis of diphenyl ether in the presence of 4-tert-
butylmethoxybenzene (6 h, Fig. 3D)
+ 40% SIPr HClNaOtBu, toluene,
120 °C, 6 h
OMeO+
(1 equiv)(1 equiv) (1 bar at rt)Conversions Yields
tBu
20% Ni(COD)2,
+HO
H2 +tBu
94%100% 5% 94% 2% The reaction was conducted according to General Procedure A with Ni(COD)2 (8.5 mg,
3.1⋅10-2 mmol), SIPr⋅HCl (25.7 mg, 6.02⋅10-2 mmol), NaOtBu (37.0 mg, 0.385 mmol),
diphenyl ether (25.9 mg, 0.152 mmol), 4-tert-butylmethoxybenzene (24.9 mg, 0.151
mmol), dodecane (internal standard for GC, 17.3 mg) and m-xylene (0.8 ml) at 120 °C for
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
45
6 h. GC analysis of the reaction mixture showed full conversion of diphenyl ether and
formation of benzene and phenol in 94% yields; only 5% of the starting 4-tert-
butylbenzyl methyl ether was consumed to give tert-butyltoluene in 2% yield.
Mercury poisoning experiments Hydrogenolysis of diphenyl ether in the presence of excess of mercury.
+O
+
(1 bar at rt)99%
HO
99%
H2
99% 99%no Hg320 equiv. Hg
40% SIPr HClNaOtBu,
120 °C, 16 h
20% Ni(COD)2,
m-xylene,
In a glovebox, a 15 ml Schlenk tube equipped with a Teflon-stopcock was charged with
Ni(COD)2 (8.4 mg, 3.1⋅10-2 mmol), SIPr⋅HCl (27.1 mg, 6.34⋅10-2 mmol), NaOtBu (39.9
mg, 0.415 mmol) and a magnetic stir bar. A solution of diphenyl ether (26.0 mg, 0.153
mmol) and dodecane (internal standard for GC, 21.0 mg) in m-xylene (0.8 ml) were
added. The mixture was stirred for 3 min at which time mercury (1.96 g, 9.77 mmol, 320
equiv. with respect to the catalyst) was added. The Schlenk tube was sealed with the
Teflon stopcock and removed from the glovebox. The reaction mixture was degassed via
two cycles of freeze-pump-thaw, and the tube was pressurized with 1 bar (15 psi) of
hydrogen at room temperature, sealed with the Teflon stopcock, and heated in an oil bath
at 120 °C for 16 h. The reaction mixture was then cooled to room temperature, diluted
with ether (1 ml) and quenched with 1.7M aqueous HCl (1 ml) followed by stirring for 10
min. The organic layer was separated, and the aqueous layer was extracted with 1 ml of
ether. The combined organic layers were passed through a short pad of Celite and
subjected to GC and GC/MS analyses, which showed the formation of benzene (m/z 78)
and phenol (m/z 94) in quantitative yields (99%) at full conversion of the starting
diphenyl ether; no decelerating effect of the added mercury was observed, as compared to
the hydrogenolysis in the absence of mercury (99% yields of benzene and phenol).
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
46
Hydrogenolysis of 2-methoxynaphthalene in the presence of excess of mercury. 40% SIPr HCl,
100 °C, 16 h
+
(1 bar at rt)
20% Ni(COD)2,
H2
OMe
95%95%
no Hg311 equiv. Hg
AlMe3NaOtBu,m-xylene,
In a glovebox, a 15 ml Schlenk tube equipped with a Teflon-stopcock was charged with
Ni(COD)2 (8.2 mg, 3.0⋅10-2 mmol), SIPr⋅HCl (26.1 mg, 6.11⋅10-2 mmol), NaOtBu (40.6
mg, 0.422 mmol) and a magnetic stir bar. A solution of 2-methoxynaphthalene (25 mg,
0.158 mmol) and dodecane (internal standard for GC, 17.9 mg) in m-xylene (0.8 ml) were
added, and the mixture was stirred for 3 min, followed by addition of AlMe3 (2M
solution in toluene, 75 µl, 0.15 mmol). After stirring for 1 min, mercury (1.86 g, 9.28
mmol, 311 equiv. with respect to the catalyst) was added, and the Schlenk tube was
sealed with the Teflon stopcock and removed form the glovebox. The reaction mixture
was degassed via two cycles of freeze-pump-thaw, and the tube was pressurized with 1
bar (15 psi) of hydrogen at room temperature, sealed with the Teflon stopcock, and
heated in an oil bath at 120 °C for 16-48 h. The reaction mixture was then cooled to room
temperature, diluted with ether (1 ml) and quenched with 1.7 M aqueous HCl (1 ml),
followed by stirring for 10 min. The organic layer was separated, and the aqueous layer
was extracted with 1 ml of ether. The combined organic layers were passed through a
short pad of Celite and subjected to GC and GC/MS analyses, which showed the
formation of naphthalene (m/z 128) in 95% yield at full conversion of the starting 2-
methoxynaphthalene; no decelerating effect of the added mercury was observed, as
compared to the experiment in the absence of mercury (95% yield of naphthalene).
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
47
Table S3. Selected Results on the Effect of Ligand, Temperature and Amount of Base
on Hydrogenolysis of Diphenyl Ether
+O
+
(1 bar at rt)
HOH2
40% LNaOtBu, m-xylene,
T °C, 16 h
20% Ni(COD)2,
Entry Ligand L NaOtBu, equiv. T, °C Conversion, % Yield of PhH, % Yield of PhOH,
% 1 - 0 120 0 0 0 2 PCy3 0 120 1 1 0 3 PCy3 2.5 120 4 0 0 4 SIPr·HCl 0.44 120 73 72 6 5 SIPr·HCl 2.5 120 100 99 99 6 SIPr·HCl 2.5 100 75 69 75
Conditions: see General Procedure A (p. 29).
Table S4. Effect of Ligand, Nickel Source, Temperature, Amount of Base and AlMe3 on
Hydrogenolysis of 2-Methoxynaphthalene
T °C, 16 h
+
(1 bar at rt)
"Ni", L,H2
OMeAlMe3
NaOtBu,m-xylene,
Entry “Ni” “Ni”, mol % Ligand L NaOtBu,
equiv. AlMe3, equiv. T, °C Conversion, % Yield of
naphthalene, % 1 Ni(COD)2 20 SIPr 0 0 100 24 15 2 Ni(COD)2 20 SIPr·HCl 0.44 0 100 33 29 3 Ni(COD)2 20 SIPr·HCl 2.5 0 100 58 57 4 Ni(COD)2 20 SIPr·HCl 2.5 0 120 89 89 5 Ni(COD)2 20 SIPr·HCl 2.5 1 100 100 95 6 Ni(COD)2 5 SIPr·HCl 2.5 1 100 10 7 7 Ni(COD)2 20 SIPr·HCl 2.5 1 80 100 98 8 Ni(COD)2 20 SIPr·HCl 0.44 1 100 34 17 9 Ni(COD)2 20 SIPr·HCl 2.5 0.2 100 66 66 10 Ni(acac)2 20 SIPr·HCl 2.5 1 100 57 57
Conditions: see General Procedure A and B (p. 29).
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
48
Table S5. Control Experiments for Hydrogenolyisis of 2-Methoxynaphthalene
OMe+ H2 m-xylene,
100 oC, 16 hNi(COD)2+ + SIPr.HCl + AlMe3+tBuONa
1 bar 0.2 equiv 0.4 equiv 2.5 equiv 1 equiv1 equiv
Entry H2 Ni(COD)2 SIPr.HCl NaOtBu AlMe3 Conversion, % Yield, % 1 + - - + - 3 0 2 + - + + - 5 0 3 + - - + + 5 0 4 + - - - - 4 0 5 + - + + + 4 0 6 + + - + - 2 0 7 - + + + + 2 8* 8 + + + + + 100 98 9 + + + + - 58 57
10 - + + + - 4 4 11 + + - + - 2 0
* 2-Methylnaphthalene was detected by GC/MS as a main product (41%). Procedure: see General Procedures A and B (p. 29).
Table S6. Catalyst Stability Estimation in Hydrogenolysis of Methyl Aryl Ethers.
OMe+
20% Ni(COD)2, 40% SIPr·HClH2
R R
tBuONa, m-xylene(1 bar)
+ MeOH
Entry Aryl Ether Temp, oC Time, h Conversion, % Yield of Arene, %
1 140 16 68 66 2 140 32 68 65
3 120 16 88 84 4
OMe
120 32 89 85
5 120 16 72 71
6
OMe
120 32 72 72
7 120 16 46 42
8 120 32 60 59
9 Ph
OMe
120 48 60 59
Conditions: see General Procedure A (p. 29).
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
49
7. NMR spectra. Di-2-methoxyphenyl ether. 1H NMR (400 MHz, CDCl3).
Di-2-methoxyphenyl ether. 13C {1H} NMR (100 MHz, CDCl3).
OOMe OMe
OOMe OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
50
2-Methoxyphenyl phenyl ether. 1H NMR (400 MHz, CDCl3).
2-Methoxyphenyl phenyl ether. 13C {1H} NMR (125 MHz, CDCl3).
OOMe
OOMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
51
Di-3-methoxyphenyl ether. 1H NMR (400 MHz, CDCl3).
Di-3-methoxyphenyl ether. 13C {1H} NMR (100 MHz, CDCl3).
OMeO OMe
OMeO OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
52
Di-4-tert-butylphenyl ether. 1H NMR (400 MHz, CDCl3).
Di-4-tert-butylphenyl ether. 13C {1H} NMR (125 MHz, CDCl3).
O
tButBu
O
tButBu
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
53
Di-3-methylphenyl ether. 1H NMR (400 MHz, CDCl3).
Di-3-methylphenyl ether. 13C {1H} NMR (100 MHz, CDCl3).
OMe Me
OMe Me
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
54
4-Methoxyphenyl 4-trifluoromethylphenyl ether. 1H NMR (500 MHz, CDCl3).
4-Methoxyphenyl 4-trifluoromethylphenyl ether. 19F {1H} NMR (470 MHz, CDCl3).
O
F3C OMe
O
F3C OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
55
4-Methoxyphenyl 4-trifluoromethylphenyl ether. 13C {1H} NMR (125 MHz, CDCl3).
O
F3C OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
56
Di-2-Methylphenyl ether. 1H NMR (400 MHz, CDCl3).
Di-2-Methylphenyl ether. 13C {1H} NMR (100 MHz, CDCl3).
OMe Me
OMe Me
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
57
4-Methylphenyl phenyl ether. 1H NMR (400 MHz, CDCl3).
4-Methylphenyl phenyl ether. 13C {1H} NMR (100 MHz, CDCl3).
O
OMe
O
OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
58
2-(Hexyloxy)naphthalene. 1H NMR (400 MHz, CDCl3).
2-(Hexyloxy)naphthalene. 13C {1H} NMR (100 MHz, CDCl3).
O
O
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
59
4-(Hexyloxy)biphenyl. 1H NMR (400 MHz, CDCl3).
4-(Hexyloxy)biphenyl. 13C {1H} NMR (100 MHz, CDCl3).
O
O
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
60
4-tert-Butylbenzyl phenyl ether. 1H NMR (400 MHz, CDCl3).
4-tert-Butylbenzyl phenyl ether. 13C {1H} NMR (100 MHz, CDCl3).
OtBu
OtBu
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
61
3,4-Dimethoxybenzyl 2-methoxyphenyl ether. 1H NMR (500 MHz, CDCl3).
3,4-Dimethoxybenzyl 2-methoxyphenyl ether. 13C {1H} NMR (125 MHz, CDCl3).
O
MeOOMe
MeO
O
MeOOMe
MeO
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
62
1-Methoxy-1-phenylpropane. 1H NMR (400 MHz, CDCl3).
1-Methoxy-1-phenylpropane. 13C {1H} NMR (100 MHz, CDCl3).
OMe
OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
63
Methyl 4-tert-butylbenzyl ether. 1H NMR (500 MHz, CDCl3).
Methyl 4-tert-butylbenzyl ether. 13C {1H} NMR (125 MHz, CDCl3).
OMetBu
OMetBu
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
64
Methyl 2-(2-methoxyphenoxy)acetate. 1H NMR (400 MHz, CDCl3).
Methyl 2-(2-methoxyphenoxy)acetate. 13C {1H} NMR (100 MHz, CDCl3).
O
OMe
OMe
O
O
OMe
OMe
O
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
65
Methyl 3-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-methoxyphenoxy)propanoate. 1H NMR (500 MHz, CDCl3).
Methyl 3-(3,4-dimethoxyphenyl)-3-hydroxy-2-(2-methoxyphenoxy)propanoate. 13C {1H} NMR (125 MHz, CDCl3).
OOMe OH
MeO O OMe
OMe
OOMe OH
MeO O OMe
OMe
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
66
1-(3,4-Dimethoxyphenyl)-2-(2-methoxyphenoxy)-l,3-propanediol. 1H NMR (500 MHz, CDCl3).
1-(3,4-Dimethoxyphenyl)-2-(2-methoxyphenoxy)-l,3-propanediol. 13C {1H} NMR (125 MHz, CDCl3).
OOMe OH
OMe
OMe
HO
OOMe OH
OMe
OMe
HO
Selective, Nickel-Catalyzed Hydrogenolysis of Aryl Ethers. Supporting Online Material.
67
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68
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