visible-light-mediated organic photoredox catalysis in...

X

YPSX Y +

Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of Alkenes

Reporter: Leifeng Wang Prof. Huang Group Meeting

August 22th 2016

Literature Report

Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes i) C-C bond formation ii) C-N bond formation iii) C-S bond formation iv) C-O bond formation

III: Summary

CN

CN

CN

CN

O

DCB

DCA

BP

CN

CN

DCN

= 291 nm

= 325 nm

= 422 nm

Cyanoarenes Benzophenones

= 335 nmO

Me2N NMe2MK

= 365 nmO

FLN= 377 nmO

XXO: X=O

= 340 nm

TXO: X=S= 360 nm

Quinones

O

OAQ= 326 nm

CN

CN

Cl

Cl

O

O

DDQ

∼377 nm

Cl

Cl

Cl

Cl

O

O

TCBQ

= 450nm

Organo-photocatalyst : What is?

R

NMe

Acr-Me+

Ph-Acr-Me+: = 424nm

Mes-Acr-Me+: = 425nm

NR′

NR

RN

R

R

AOH+: = 495nm R= Me, R'=H

AcrF+: = 470nm R= H, R'=Me

= 470nm R= H, R'=HPFH+:

NN

O

O

O

O

RR

PDI: R=H

PDI-a: R=2,6-diisopropylphenyl

PDI-b: R=2,5-di-tert-butylphenyl

S

NPh

PTh:= 315 nm

S

N

N N

MB+: = 650nm

NN MeMe

DAP2+

O

CO2HY

HOX X

O

Y

ZZ

Z

Z

Fluorescein: = 491nm X,Y,Z=H

Eosin Y: = 533nm X,Y=Br, Z=H

Rose Bengal: = 549nm X,Y=I, Z=Cl

O

CO2R''Y

N N

Y

R

R'

Rhodamine B: = 550nm

Rhodomine 6G: = 550nm

R'=H,Y=Me, R,R''=Et

R'',Y=I, R,R'=Et

N

R

Me

NMQ+:< 300 nm

= 329 nmQuCN+:

X

R

R R

X=O or S, R=H or OMe

Acridiniums

Thiazines

Xanthenes

Pyryliums

Quinoloniums

Organo-photocatalyst : What is?


III: Summary

+hv

S0

S1

or -hv

or -hv

v0

vn

T1

ISCIdeal features

for S1:high φflong τf

Ideal featuresfor T1:

high φISClong τT

non-radiativeradiative

S0: ground state singlet S1: excited state singlet ISC: intersystem crossing

τf: lifetime of fluorescence

φf: quantum yield of fluorescence

T1→S0:spin forbidden

T1 states tend to be the

longest-lived

Photophysical Processes

750 nm red

380 nm/violet

Oxidative and Reductive Quenching Cycles of a Photoredox Catalyst

PS∗

oxidative quenching

sub or [Red] sub or [Ox]

reductive quenching

sub or [Red]

PS

PS

sub or [Ox]sub or [Red]

PS

sub or [Red]sub or [Ox]

sub or [Ox]

turnover

turnover

PS is an excited state reductant

PS is an excited state oxidant

HOMO

LUMO +

HOMO

LUMO

ET

HOMO

LUMO

HOMO

LUMO

1PS∗ sub

subPS

HOMO

LUMO +

HOMO

LUMO

cage escape

1

HOMO

LUMO +

HOMO

LUMO

ET

HOMO

LUMO

HOMO

LUMO

3PS∗ sub

subPS

HOMO

LUMO +

HOMO

LUMO

3

BETcage escapeBET

free ions ground state reactants

subPS PS sub

Singlet or Triplet Excited States: Does It Matter?


III: Summary

PS∗

PS

PS

H X

PS

PS

PS∗

Ox.Quench.

Red.Quench.

[-e-]

[Ox]

[Ox]

[Ox]

[Ox]

PS∗

PS

PS

X H

PS

PS

PS∗ Ox.Quench.

Red.Quench.

[+e-]

[Red]

[Red]

hv

hv

hv

hv

[Red]

[Red]

Net Oxidative Net Reductive

+ X Y

PS PS

PS

PS

[±-e

- ]Ox.Quench.

Red.Quench.PS∗

hv hvPS∗

XY

Net Redox-Neutral

Net Redox Outcomes for Photoredox Transformations


III: Summary

DCA (20 mol %)λ = 405 nm

PPh3(0.6 eq.)DMF/i-PrOH/H2O

CN

CN

DCA= 422 nm

68% 73% 61%

YMe

O

n

MeO

Y

n

Me

O

CO2Me Me

ONC

Me

O

CN

CO2EtMe

O DCA (20 mol %)λ = 405 nm

condition

MeO

EtO2C

H

H

O

Me

H

+

O

Y

DCA (20 mol %)λ = 405 nm

PPh3(0.6 eq.)DMF/i-PrOH/H2O

O

H H

Y Y = CO2Et: 84%Y = CN: 72%

condition A: PPh3(0.6 eq.), DMF/i-PrOH/H2Ocondition B: 1,5-dimethoxynaphatene(15 mol%), ascorbic acid(2.6 equiv),DMF/i-PrOH/H2O

76%

<20%

14%1.6:1 cis:trans

70%1.6:1 cis:trans

Selected Products

A:

B:

C:

Reductive Cyclizations of Unsaturated Enones

Ghorai, M. : Tetrahedron Lett. 1994, 35, 7837

CO2EtMe

O

CO2EtMe

OH

Me

OEtO2C

DCA*

DCADCA

H2O

PPh3

PPh3

H2O

-e-O=PPh3hv

+e-+H+

Me

OEtO2C

Mechanism:condition A

CO2EtMe

O

CO2EtMe

OH

Me

OEtO2C

DCA*

DCADCA

H2O

DMN

DMNhv

+e-+H+

Me

OEtO2C

Mechanism:condition B

2 HA-

A + HA- + H+

Reductive Cyclizations of Unsaturated Enones

X

R1

R2Me3SiO DCA (20 mol %)

λ = 419 nm

MeCN/i-PrOHor MeCN X

R1

R2O H

H

CN

CN

DCA= 422 nm

O H

H

O H

H

O H

H

Me

H

H

O

O H

H

H

H

25% 19%1:1 dr

51%1.1:1 dr

20%2.3:1 dr

Me3SiO

O H

H

Me3SiO

OH

HH

O H

H

DCA*DCA

DCA

hv

Mechanism -SiMe3-

6-endo-trig

selected products:

Oxidative Cyclization of Unsaturated Silyl Enol Ethers

Fu, W.-F.: Eur. J. Org. Chem. 1998, 1998, 1583.

OHR1 R2

O+ BPSS(20-30 mol%)

i-PrOH/H2O, solarH

R

R1 R2

OOHR

O

NaO3S SO3NaBPSS

(mixture of 3,3' and 4,4' isomers)

O

OH

MeMe n-Pr

O

O

MeMe CO2H O

OO

Hn-Pr

66% 83% 40%

OHH

R

OHR R1 R2

O

R1 R2

OOHR

BPSS* BPSSH

BPSS

R1 R2

OOHR

Mechamism

Selected Products

solar

Radical Conjugate Addition Reactions in Flowwith Solar Irradiation

Fagnoni, M.: Green Chem.

2009, 11, 1653

R + SONaF3C

O

Mes-Acr-Me+ (5 mol%), MTS (20 mol%)

CHCl3/TFE (9:1), 455 nm blue LEDsCF3

R

H

SH

CO2MeMTS

HOH

CF3 BzO CF3 PhthN CF3

PhCF3

OH

H Me H MeCF3

Me

Me

Ph2t-BuSiO

CF3

OH4-OMe-Ph Me

CF3

4-OMe-PhMe

CF3

4-Cl-Ph50% 69% 66% 69%

51% 67% 64% 56%

(1-3 equiv.) 25-74% yieldsslected products

SOF3C

OS

OF3C

OCF3

R

RCF3

RCF3

H

Mes-Acr-Me+ Mes-Acr-Me

Mes-Acr-Me+

∗CO2Me

S

CO2Me

S

CO2Me

SH

OH

CF3

TFEhv

+H+Mechanism

-SO2

HAT

Hydrotrifluoromethylation of Alkenes Using the Langlois Reagent

Nicewicz: Chem. Sci. 2013, 4, 3160

R +I

O

CF3

MB-Cl (2 mol%), DBU (2 equiv)

λ = White LEDs

RCF3

Me CF3 CF3HO CF3BzOO

Me

CF3MeH

H

67% 48% 83% 40%

9

S

N

N N

Cl

MB-Cl

Selected Products:

O

IO

CF3

O

IO

CF3

O

CF3R

RCF3

RCF3

MB+

MB+

MB

∗

IO

O

DBU

DBU

DBU

N

N-H+

Mechanism

Olefin Hydrotrifluoromethylation

Scaiano, J. C: ACS Catal. 2014, 4, 2530

R1

R2

R1

R2

+ p-MeO-TPT (3 mol%), 0.5 eq. ER

MeCN, λ = 450 nmR2

R1 R1

R2

O

PMP

PMP PMP

BF4-

= 470nmp-MeO-TPT

Me Me

MeO OMeMeO OMe

MeO OMeMe Me

MeO OMe

MeO

OMe MeO

OMe

N NCBz CBz

H

H

H

H

50%(±)-magnosalin

73%83%54%

O

PMP

PMP PMP

BF4-

Ar

R

Ar

R

Ar

R+

Ar

R R

Ar Ar

R R

Ar

ERER

*

O

PMP

PMP PMP O

PMP

PMP PMP

BF4-

λ = 450 nm

Mechanism

selected products:

Nicewicz：J. Am. Chem. Soc. 2015, 137, 7580

Styrene Cyclodimerization

RBF3

K

+

R1

R2

EWG Mes-Acr-MeClO4 (2 mol%)Acetone/MeOH (1:1)

λ = 425 nm (blue LEDs) R1

R2

EWGR

MeCO2Et

CO2EtAd

Cyc Me

CO2BnO

Cyc

MeCO2Et

CO2Etn-Bu

94% 88% 61% 38%

Selected Products:

RCO2H +

CO2EtEtO2C

Me

Mes-Acr-MeClO4 (2 mol%)Na2CO3 (0.1 equiv.)

MeOHλ = 425 nm (blue LEDs)

MeCO2Et

CO2EtR

1.2 equiv

MeCO2Et

CO2EttBu

MeCO2Et

CO2EtAd

MeCO2Et

CO2EtCy

81% 86% 40%

1.2 equiv

Selected Products:

Deborylative and Decarboxylative Radical Conjugate Addition Reactions

Akita, M.: RSC Adv. 2015, 5, 21297


III: Summary

CbzNHOH

R

R1R2

R3H

+

RB-Na2 (3 mol%)pyridine (10 mol%)

MeCN, Airλ ~ 11 w fluorescent

N

R3

R2Cbz

OH

R R1

NPhCbz

OH

NCbz

OHn-Pent

NCbz

OH

Me

O NH2

NCbz

OHn-Pr

n-Pr

78% 44% (4:1 E/Z)

70% (4:1 E/Z)

81%

Selected Products:

CbzNHOH

CbzNHOH

CbzNHO

CbzNO

Ph

H

NPhCbz

OH

RB2-

RB2-

RB•3-∗

O2

O2HO2 H2O2 Nitroso-Ene

Mechanism

O

CO2NaI

NaOI I

O

I

ClCl

Cl

Cl

RB-Na2

Nitroso-Ene Reaction Enabled by PET

Tan C.H.: ChemCatChem 2013, 5, 235

R

Cat. (5 mol%), TEMPO (20 mol%)

amine (1,25-2 equiv), DCE, 1 atm O2λ = 455 nm (blue LEDs)

R

NR R

N

Mes

Ph

tBu tBu

Cat. = Mes-(tBu)2Acr-PhBF4

OMe

NN

NN

N

Me

N

Me

NN

Me Me

OMe

NNN

OMe

NH2

OMe

NH2

ClN

N

NH2

Me

88% 7:1 p:o

43% 82% 71% 3.5:1 p:o

using 4 equiv. amine = NH2CO2NH4

59% 1.6:1 p:o

33% 61%

selected products:

R R

catalyst+* catalyst

catalyst+

HN

N

HNN

RNN

R

NN

HH

OO

TEMPO

TEMPO-H

O2

O2

HOO--HOO

path A

path B

Mechanism

Aryl C−H Amination

Nicewicz： Science

2015, 349, 1326


III: Summary

SAr

O ONa+

RAr1

R1

RAr1

R1

SAr

O OEY-Na2 (10 mol%)PhNO2 (1 equiv)

DMF/H2O (3:1), 40 °Cλ = Green LED11-99% yields

S

F

O O

N

SPh

EtO

OEtO

O OS

R

O O

R = H, 99%, R = Me, 79%R = OMe, 51%, R = F, 79%54% 11%

Selected Products:

(3 equiv)

EY2-

EY2-

EY•3-∗

SAr

O O SAr

O OR Ar1

R1

RAr1

R1

SAr

O O

PhNO2

PhNO2

RAr1

R1

SAr

O OPhNH2Mechanism

hv

O

CO2NaBr

NaOBr Br

O

Br

EY-Na2

Vinyl C−H Sulfonylation via PET-Generated Sulfinyl Radicals

Burkhard K.：Adv. Synth. Catal. 2015, 357, 2050

ArEYH2, NH4SCN (1 equiv.), MeCN, Air

λ (Green LED)74-96% yields

OS

Ar

NH

O

S

NH O

S

NH

MeOO

S

NH

O2N

92% 96% 74%

Selected Products:

ArAr

SCN

Ar

SCNOO

Ar

SCNO

Eosin Y Eosin Y

Eosin Y

NCS NCS

O2

O2

+ NH4

Ar

SOH

N

O

SAr

NH

O2

NH3 + O2∗

Mechanism

hv

O

CO2HBr

HOBr Br

O

Br

Eosin Y

2-Imino-1,3-Oxathiolanes by Difunctionalization of Styrenes

Yadav, S.： Green Chem. 2015, 17, 3515


III: Summary

R

RR

R

Mes-Acr-MeClO4 (20 mol%)

CD3CN, 1 atm O2λ > 430 nm

O OR RR R R R

O

Me

MeMe

Me

Ph

PhPh

Ph

O OMe MeMe Me

O OPh PhPh Ph

Me Me

O

Ph Ph

O

+

~30%

~20%

~10%

~70%

reactants products

R

RR

R

O2

Proposed Key Step

R

R

Mes-Acr-MeClO4, O2, hv

R

R

+

O

O

OO

Tetrasubstituted Alkene Oxygenation

Fukuzumi, S：J. Am. Chem. Soc. 2004, 126, 15999

RDDQ, t-BuNO(5 mol%), H2O(17 eq.), MeCN, O2

λ > 390 nm

R

OH

CN

CN

Cl

Cl

O

ODDQ∼377 nm

OH

93%

OHF

34%p-:o-:i- = 4.2:1:2.5

OHCl

34%p-:o- = 4.6:1

OHBr

14%p-:o- = 3.9:1

HO HOH

DDQ*

O

O

CN

CN

Cl

Cl

OH

O

CN

CN

Cl

Cl

OH

OH

CN

CN

Cl

ClDDQ

t-BuNOO2

λ> 390 nmDDQ DDQH DDQH2

Mechanism

Selected Products:

C−H Hydroxylation of Benzene and Halobenzenes

Fuzukimi, S: J. Am. Chem. Soc. 2013, 135, 5368.

Contents I: Background Organo-photocatalyst : What is? Organo-photocatalyst : Photophysical Processes II: Visible-Light-Mediated Organic Photoredox Catalysis in Functionlization of alkenes C-N bond formation C-C bond formation C-S bond formation C-O bond formation III: Summary

PRCC Reactions

R

R

Nuc

via:

O

O

R

NRH

BnO

N PG

OH

R

R

O

OH

R

R

O

H

R

R

R

H

O R

R

H

O R

O

R

H HN

SR

O

O

R

HN X

X

R

HF

R

HCl

R

H

O PO

OO

R

H

O SO

OO

Anti-Markovnikov Alkene Hydrofunctionalization and PRCC Reactions

Nicewicz Group

Me

Ph+

OHNPG

Ph

DCM, 455 nm LEDs NO

BnPh

MePG

ON

BnPh

Me

PG+

PG = Ms, Ts, Ns, Tf

R

R

R1NH

R2

O R3

Mes-Acr-MeBF4 (2.5 mol%), (PhS)2 (10 mol%)

DCE, 455 nm LEDs ON

R3

R2R

R

H

R1

53-95% up to 2:1 dr

OMe

Me n Cl

OHO

1) Mes-Acr-Me+ (2.5 mol%), (PhS)2 (10 mol%)

2) RuO4/NaIO43) K2CO3, NEt3, i-PrOH

OO

HO2C

Me nn = 3, (±) methylenolactocin 16%

n = 11, (±) protolichesterinic acid 37%

RR1

NH

R2

S R3

Mes-Acr-MeBF4 (2.5 mol%), (PhS)2 (10 mol%)4-MeO-PhSH (20 mol%)

DCE, 455 nm LEDs SN

R3

R2

RR1

60-80% up to 4:1 dr

H

Mes-Acr-Ph+ (5 mol%), 4-MeO-PhSH (30 mol%)2,6-lutidine (20 mol%)

Highlights of Anti-Markovnikov Alkene Hydrofunctionalization and PRCC Reactions

from Nicewicz Group

Org. Lett. 2015, 17, 1316 Chem. Sci. 2015, 6, 270 Org. Lett. 2014, 16, 4810

R RR

XR'

RX

R'

H

Mes-Acr+*

Mes-Acr+

Mes-Acr PhS

PhS

PhS-H

PhSSPh

R'-X-H-H+

hv hv

X H -H+

RX

RX

R

HHAT

PRCC

HATcycle

PETcycle

NMe

Me

Me

Me

X

NMe

Me

Me

Me

X

Bulky Mes-group blocksaddition at 9-position

Mes-Acr-Me+

Mes-Acr

tBu OH

O+

NMe

NaOH, MeCN/H2O, O2

λ = 358 nm N

tBu

Me

Proposed Mechanism for Anti-Markovnikov Alkene Hydrofunctionalization and PRCC Reactions


III: Summary

R

Cyclo-additions

AtomTransfer

Cyclizations

C-HFunctionalizations

Hydro-functionalizations

BondCleavageReactions

C-C

C-N C-O

C-S

Summary

1) Site specificity and functionalization of stronger C−H bonds present new challenges 2) Methods for controlling enantioselectivity are scarce 3) Applications of organic photoredox catalysis to natural product synthesis are just

starting to occur 4) Highly reducing catalysts and more robust chromophores are always in demand

Challenges Remain:

Thank You for Your Kind Attention!

What Can We Do

Intramolecular

X

R1

R2Me3SiO DCA (20 mol %)

λ = 419 nm

MeCN/i-PrOHor MeCN X

R1

R2O H

H

CN

CN

DCA= 422 nm

> 650 nm

PSOSiMe3

R+

PS (x mol %)blue/green LEDs

solvent/rt

O

n n

R

Intermolecular

R

R

Nuc

via:

O

O

R

NRH

BnO

N PG

OH

R

R

O

OH

R

R

O

H

R

R

R

H

O R

R

H

O R

O

R

H HN

SR

O

O

R

HN X

X

R

HF

R

HCl

R

H

O PO

OO

R

H

O SO

OO

Anti-Markovnikov Alkene Hydrofunctionalization and PRCC Reactions

Nuc = Carbon & Organic Photoredox Catalysis/Transition Metal Catalysis

R1

OH R3

+

PS (x mol %)/additiveblue/green LEDs

solvent/rt R1

OR3

> 650 nm

PS

R2 R2

X+

R

PS (x mol %)/TMblue/green LEDs R

Nuc = Carbon

Anti-Markovnikov Alkene Hydrofunctionalization Reactions

> 650 nm

PS

R Nuc

RadicalAcceptor RA

RNuc

RA

RA = O2

RA = Togni ReagentRA = AlkeneRA = Aryl ......

Difuctionalization of Alkenes

R+

PS (x mol %)/O2blue/green LEDs

solvent/rtCN-

R

OCN

Organic Photoredox Catalysis/Transition Metal Catalysis

R

Nuc RNuc

Ni(0)

RNuc

Ni(I)

Ar X

RNuc

Ni(III)Ar X

RNuc

Ar

Ni(I) X

Ni(0)

visible-light-mediated organic photoredox catalysis in...

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