Catalytic Asymmetric Michael Additions of α-Cyanoacetates

Abstract

Enantiopure Michael addition products of α-cyanoacetates constitute attractive precursors for functionalised quaternary amino acids and other biologically interesting compounds. Since the pioneering work by Ito et al. in 1992 using rhodium(I) in combination with a trans-chelating planar chiral diphosphine, various complementary approaches have been reported; these are critically discussed and compared in this review. The most efficient recent methodologies utilise a bifunctional activation mode; for example, by dinuclear Lewis acid catalysis or by a well-defined hydrogen-bonding network. This strategy can overcome the difficulty that α-cyanoacetates are incapable of two-point binding to a Lewis acid thus hampering the differentiation of prochiral enol(ate) faces.

1 Introduction

2 Rhodium, Iridium and Ruthenium Catalysts

3 Palladium and Platinum Catalysts

4 Aluminium Catalysts

5 Organocatalysis

5.1 Cinchona Alkaloids

5.2 Thiourea-Derived Catalysts

5.3 Cinchona Alkaloid-(Thio)Urea Hybrids

5.4 Iminium Catalysis

6 Phase-Transfer Catalysis

7 Conclusions

Key words

amino acids - asymmetric catalysis - α-cyanoacetate - quaternary stereocentre - Michael addition

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15

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24

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