Synthesis 2008(8): 1306-1315  
DOI: 10.1055/s-2008-1072516
FEATUREARTICLE
© Georg Thieme Verlag Stuttgart · New York

Protonation of Homoenolate Equivalents Generated by N-Heterocyclic Carbenes

Brooks E. Maki, Audrey Chan, Karl A. Scheidt*
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
Fax: +1(847)4672184; e-Mail: scheidt@northwestern.edu;
Further Information

Publication History

Received 22 February 2008
Publication Date:
18 March 2008 (online)

Abstract

Homoenolate equivalents are generated by Lewis basic N-heterocyclic carbene catalysts and then protonated to generate efficiently saturated esters from unsaturated aldehydes. This reactivity is extended to the generation of β-acylvinyl anions from alkynyl aldehydes. The asymmetric protonation of a homoenolate equivalent generated from a β,β-disubstituted aldehyde can be accomplished with a chiral N-heterocyclic carbene.

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Our preliminary studies of generating homoenolates using N-heterocyclic carbenes and the protonation of these unusual intermediates was first described in a lecture by K.A.S. at the 2004 Natural Products Gordon Research Conference (Tilton, NH) on Thursday, July 29, 2004.