Organocatalytic enantioselective formal conjugate addition of a hydroxymoyl anion to α,β-unsaturated aldehydes

Article abstract of DOI:10.1002/chem.201100605

The conjugate addition reaction is a fundamental transformation in organic chemistry. The wide variety of reagents amenable to participate as Michael donors or acceptors makes this reaction extremely versatile, allowing the preparation of many different classes of highly functionalized compounds in a very easy and reliable way. Moreover, the conjugate addition reaction also occurs very often with the concomitant generation of one or more stereocenters and, in this context, intense research has focused on the development of catalytic enantioselective approaches for carrying out this important reaction in a stereocontrolled way. Although most of the methodologies reported to date involve the use of transition-metal catalysts, several organocatalytic enantioselective variants of the conjugate addition reaction have been developed in the last few years; many of which have performed excellently with regard to chemical efficiency and stereocontrol. On the other hand, many research groups have also directed their attention to finding novel reactivity patterns applied to the conjugate addition reaction by using umpoled reagents, which have expanded the array of compounds which can be used as Michael donors or acceptors, to further increase the scope of this methodology. In particular, the enantioselective conjugate addition of acyl or formyl anions to a,b-unsaturated carbonyl compounds or related derivatives entails a particular interest because this transformation allows the preparation of 1,4-dicarbonyl compounds, which are classically much more difficult to access by standard C-C bond forming reactions than the corresponding 1,3- or 1,5-dicarbonyl compounds.[4] However, despite the enormous potential of the oxime moiety and the key role played by this functional group in plenty of organic reactions, the development of umpoled reagents that behave as hydroxymoyl anion equivalents remains unexploited