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Synthesis 2005(2): 233-239  
DOI: 10.1055/s-2004-834933
PAPER
© Georg Thieme Verlag Stuttgart · New York

Michael Addition of Ketone Enolates to α,β-Unsaturated Esters or Amides in a One-Pot Procedure: Highly Efficient Effect of Lithium Salt Generated in situ on Organotin Enolate

Makoto Yasuda, Yusuke Shigeyoshi, Ikuya Shibata, Akio Baba*
Department of Molecular Chemistry and Handai Frontier Research Center, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
Fax: +81(6)68797387; e-Mail: baba@chem.eng.osaka-u.ac.jp;
Further Information

Publication History

Received 31 August 2004
Publication Date:
24 November 2004 (online)

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Abstract

Michael addition of a metal ketone enolate to an α,β-unsaturated ester is thermodynamically disfavored, and thus, isolated metal enolates with an equimolar amount of Lewis acids or additives are usually required. This work describes the methodology of one-pot Michael addition from the parent ketones and unsaturated esters to the products directly. The treatment of a parent ketone with sec-butyllithium and Bu3SnBr gives a highly coordinated tin enolate that is complexed with LiBr generated in situ. The species is reactive and affords the Michael adducts, δ-keto esters and amides, in the reaction with α,β-unsaturated esters and amides, respectively.

Key words

tin enolates - ligand - Michael addition - unsaturated ester - high coordination

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6

A similar result was also observed when LDA was used instead of s-BuLi.

9

LiCl generated in situ as a side product would not be a strong enough Lewis acid for type D reaction.