History Mechanism Catalysts Applications Yves ChauvinRobert H. GrubbsRichard R. Schrock
This reaction can be thought of as a reaction where all the C=C bonds are cleaved and then rearranged in a statistical fashion.
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 substituents R.H. Grubbs, Nobel Lecture, 2005. M. A. Rouhi, C&EN. 2002, 80(51), 34.
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
Grubbs – Deuterium Labeling Examined ring closing metathesis (RCM) Pair-wiseChauvin 11 02 11 Predicted Ratio Observed The experiment supports Chauvin’s Mechanism
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
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.
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)
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.
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
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
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
SCHROCK’S CATALYST Most reactive Least stable Least tolerant Most expensive Lest reactive Moderately stable Very tolerant Least expensive Grubb’s 1 st Generation Highly reactive Very stable Very tolerant Less expensive Grubb’s 2 nd Generation
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