fan qi a0048267x gs5002 journal club. history mechanism catalysts applications yves...
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Olefin Metathesis Catalysis
Fan Qi A0048267XGS5002 Journal Club
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Outline History Mechanism Catalysts Applications
Yves Chauvin Robert H. Grubbs Richard R. Schrock
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Overview on Olefin Metathesis This reaction can be thought of as a reaction
where all the C=C bonds are cleaved and then rearranged in a statistical fashion.
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History 1956 H.S. Eleuterio – DuPont: Ring Opening Reaction
observed
1964 Banks and Bailey – Phillips Petroleum
1967 Chalderon coined the term “olefin metathesis” One carbon of a double bond and all its substituents exchanges
places with a carbon of another double bond with all of its substituentsR.H. Grubbs, Nobel Lecture, 2005. M. A. Rouhi, C&EN.
2002, 80(51), 34.
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Mechanism – Initial Work Calderon’s Pairwise (conventional) Mechanism
Chauvin’s Metallacyclobutane• Suggested the metal-carbene intermediate exists
J. Am. Chem. Soc., 90, 4133 (1968)
Y. Chauvin, Nobel Lecture, 2005
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Mechanism – Initial Work Grubbs – Deuterium Labeling
• Examined ring closing metathesis (RCM)
Pair-wise Chauvin
1 1
0 2
1 1
Predicted Ratio
ObservedThe experiment supports Chauvin’s Mechanism
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Mechanism – Chauvin’s Direct [2+2] cycloaddition of two alkenes is symmetric
forbidden. 1970’s Chauvin proposed the widely accepted Mechanism
reactant 1
reactant 2
Intermediate
Metallocycle
Y. Chauvin, Nobel Lecture, 2005
product 1
product 2
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Mechanism – Chauvin’s
Makromol. Chem., 141, 161 (1971)
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Ideal Catalyst Produces an infinite amount of product from a
single catalyst molecule 100% conversion rate Show high stability to moisture, air, temperature
etc. 0 by-products Soluble in organic media Cheap for industrial use
C.W. Bielawski, R.H. Grubbs Prog. Polym. Sci. 32 (2007) 1.
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Catalyst 1976 – Katz “First” well-defined catalyst
Katz suggested that the presence of a carbene on the catalyst would facilitate reactivity
J. Am. Chem. Soc., 97, 1592 (1975)
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Catalyst 1986 – Grubbs group using Tebbe Reagent
• The core metal is Titanium• Isolable metallocyclobutane• catalyzes ROMP of norbornene with good MW control, PDI ~ 1.2• reactive with heteroatoms
L. R. Gilliom and R. H. Grubbs, J. Am. Chem. Soc. 1986, 108, 733.
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Catalyst Tungsten Based Catalyst
• 1988, Schrock’s Imido-alkoxy Alkoxides varied to modulate activity Limited functional group tolerance
• 1995, Basset’s Catalyst Bulky alkoxide ligands show stereoselectivity Better function group tolerance (acetates, nitriles, anhydrides) High activity
R. R. Shrock and Amir H. Hoveyda, ACIE, 2003, 42-38, 4592
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Commercialized Catalysts 1990 - Schrock’s Catalyst
• Molybdenum alkylidenes• Highly active• Good functional group tolerance• Strict inert conditions, no water• Sterochemical control through chiral alkoxy ligands
R.R. Schrock, Nobel Lecture, 2005
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Commercialized Catalysts 1992 – 2002 Grubb’s Catalysts
• Highly stable• Minimal side reactions• Electron donating lingands• Readily initiated benzylidyne moiety• Increased functional group tolerance (Schrock tolerance
+ water alcohols, acids)
R.R. Schrock, Nobel Lecture, 2005
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Catalyst SummarySCHROCK’S CATALYST
Most reactive Least stable Least tolerant Most expensive
Lest reactive Moderately
stable Very tolerant Least expensive
Grubb’s 1st Generation
Highly reactive Very stable Very tolerant Less expensive
Grubb’s 2nd Generation
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Olefin Metathesis Applications Wide range of applications
• From baseball bat to pharmaceutical agents Example 1:
• Drugs of treating hepatitis C
Example 2:• Polymerization of DCPD
R.R. Schrock, Nobel Lecture, 2005
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Thank youQ & A