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

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

References

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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.