Rhodium-Catalyzed Methylenation of Aldehydes

Hélène Lebel* and Valérie Paquet
Contribution from the Dpartement de Chimie, Universit de Montral, C. P. 6128, Succursale Centre-Ville, Montral, Qubec, Canada H3C 3J7
J. Am. Chem. Soc., 2004, 126 (1), pp 320–328
DOI: 10.1021/ja038112o
Publication Date (Web): December 16, 2003
Copyright © 2004 American Chemical Society
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, lebelhe@chimie.umontreal.ca

Abstract

Abstract Image

The rhodium-catalyzed methylenation of aldehydes using trimethylsilyldiazomethane and triphenylphosphine produces a variety of terminal alkenes in excellent yields. These mild and nonbasic reaction conditions allow the conversion of enolizable substrates (keto aldehydes and nonracemic α-substituted aldehydes) to terminal alkenes without epimerization. Optimization of the reaction conditions led to the conclusion that a variety of rhodium(I) sources can be used as catalysts. The effect of the solvent on the reaction has also been studied, and it indicates that although the THF is the best solvent, other solvents may be used. The reactivity of the system is very much dependent on the nature of the phosphine reagent. The use of an easily removable phosphine is also described. Spectroscopic studies indicate that the reaction proceeds via an unusual mechanism which leads to the in situ formation of the salt-free phosphorus ylide, methylenetriphenylphosphorane.

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History

  • Published In Issue January 14, 2004
  • Received August 25, 2003

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