Asymmetric Organocatalytic Reductive Coupling Reactions between Benzylidene Pyruvates and Aldehydes

An organocatalytic three-component reductive coupling reaction between dimethyl phosphite, benzylidene pyruvates, and aldehydes is reported. A chiral triaryliminophosphorane catalyst promotes Pudovik addition, which is followed by phospha-Brook rearrangement to transiently generate enolates that are trapped stereoselectively by aldehydes. This reductive coupling provides vicinal polyfunctionalized stereocenters from readily available prochiral starting materials with excellent diastereoselectivity, enantioselectivity, and yield.

Enantioselective reductive multicomponent coupling reactions between isatins and aldehydes

A metal-free stereoselective reductive coupling reaction between isatins and aldehydes is reported. The reaction relies on commercial diethyl phosphite (∼€70 kg-1) as the stoichiometric reductant. Base-catalyzed Pudovik addition and phosphonate/phosphate rearrangement achieved polarity inversion on the isatin, and the derived carbanions were trapped by aldehydes with subsequent dialkoxyphosphinyl migration. Chiral iminophosphoranes were used as basic catalysts to achieve high diastereo- and enantioselectivities with excellent yields.