Stereoselective Preparation of β-Aryl-β-Boronyl Enoates and Their Copper-Catalyzed Enantioselective Conjugate Reduction

A new methodology has been developed for the stereoselective preparation of beta-aryl-beta-boronyl alpha,beta-unsaturated esters via Heck coupling, and their subsequent copper(I)-catalyzed enantioselective conjugate reduction. Various chiral secondary boronate derivatives can be accessed in excellent yields and good to high levels of enantioselectivity through the efficient copper-catalyzed process using polymethylhydrosiloxane (PMHS) as the hydride source.