Enantioselective Conjugate Addition of Aldehydes to Vinyl Phosphonates

Significance

The first organocatalytic enantio­selective conjugate addition of aldehydes to vinyl phosphonates is reported. The corresponding γ-gem-phosphonate aldehydes were obtained in good yields and with high stereoselectivities (85% yield, er = 82.5:17.5 - 98.5:1.5) by using a Hayashi-Jørgensen-type catalyst. The general scope of this reaction is illustrated by employing branched as well as linear aldehydes. The addition products were converted into β-substituted vinyl phosphonates without loss of enantioselectivity. A transition-state model is proposed to rationalize the observed ­stereoselectivity.