Tebbe Reagent

02 November, 2014 / by SK / in Reactions

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General Characteristics

The titanium-based Tebbe reagent is a valuable tool when converting carbonyl groups into exo-olefins.

The reagent can be used for the methylenation of not only aldehydes and ketones, but also esters, lactones, amides, and thioesters, which cannot be achieved by the Wittig reagent.

The high Lewis acidity of the reagent allows it to react with sterically hindered substrates. It is also only weakly basic, thus can react with enolizable substrates with a minimal risk of racemization.

The Tebbe methylenation can be followed by ring closing olefin metathesis when the substrate (the product) contains another olefin in an appropriate position.

General References

・ Tebbe, F. N.; Parshall, G. W.; Reddy, G. S. J. Am. Chem. Soc. 1978, 100, 3611. doi:10.1021/ja00479a061
・ Pine, S. H.; Zahler, R.; Evans, D. A.; Grubbs, R. H. J. Am. Chem. Soc. 1980, 102, 3270. DOI: 10.1021/ja00529a076
・ Brown-Wensley, K. A.; Buchwald, S. L.; Cannizzo, L.; Clawson, L.; Ho, S.; Meinhardt, D.; Stille, J. R.; Straus, D.; Grubbs, R. H. Pure Appl. Chem. 1983, 55, 1733. doi:10.1351/pac198355111733
・ Pine, S. H. et al. J. Org. Chem. 1985, 50, 1212. DOI: 10.1021/jo00208a013
・ Pine, S. H. et al. Org. Synth. 1990, 65, 72.
・ Kelly, S. E. Comp. Org. Syn. 1991, 1, 743.
・ Pine, S. H.; Shen, G. S.; Hoang, H. Synthesis 1991, 165. DOI: 10.1055/s-1991-26406
・ Pine, S. H. Org. React. 1993, 43, 1.
・ Beadham, I.; Micklefield, J. Curr. Org. Syn. 2005, 2, 231.

Reaction Mechanism

The active species is believed to be the titanocene Schrock carbene (CP₂Ti=CH₂), which undergoes metathesis with carbonyls to form carbon-carbon double bonds. The formation of particularly strong titanium-oxygen bond is the driving force of the reaction.