Presentation is loading. Please wait.

Presentation is loading. Please wait.

Fan Qi A0048267X GS5002 Journal Club.  History  Mechanism  Catalysts  Applications Yves ChauvinRobert H. GrubbsRichard R. Schrock.

Similar presentations


Presentation on theme: "Fan Qi A0048267X GS5002 Journal Club.  History  Mechanism  Catalysts  Applications Yves ChauvinRobert H. GrubbsRichard R. Schrock."— Presentation transcript:

1 Fan Qi A X GS5002 Journal Club

2  History  Mechanism  Catalysts  Applications Yves ChauvinRobert H. GrubbsRichard R. Schrock

3  This reaction can be thought of as a reaction where all the C=C bonds are cleaved and then rearranged in a statistical fashion.

4  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, M. A. Rouhi, C&EN. 2002, 80(51), 34.

5  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

6  Grubbs – Deuterium Labeling Examined ring closing metathesis (RCM) Pair-wiseChauvin Predicted Ratio Observed The experiment supports Chauvin’s Mechanism

7  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

8 Makromol. Chem., 141, 161 (1971)

9  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.

10  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)

11  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.

12  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

13  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

14  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

15 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

16  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

17


Download ppt "Fan Qi A0048267X GS5002 Journal Club.  History  Mechanism  Catalysts  Applications Yves ChauvinRobert H. GrubbsRichard R. Schrock."

Similar presentations


Ads by Google