The first sequential reaction promoted by manganese: complete stereoselective synthesis of (E)-alpha,beta-unsaturated esters from 2,2-dichloroesters and aldehydes.

Alpha,beta-unsaturated esters were obtained with complete control of stereoselectivity utilizing a sequential reaction of dichloroesters with a variety of aldehydes, promoted by active manganese. This methodology is generally applicable, and the C-C double bond can be di- or trisubstituted. A mechanism based on a successive aldol-type reaction/beta-elimination is proposed to explain these results.