Preparation of chiral secondary boronic esters via copper-catalyzed enantioselective conjugate reduction of β-boronyl-β-alkyl α,β-unsaturated esters

A new methodology involving the copper(I)-catalyzed enantioselective conjugate reduction of β-boronyl-β-alkyl enoates was developed. Various chiral secondary boronate derivatives can be accessed in excellent yields and good to high levels of enantioselectivity through this efficient copper-catalyzed process using polymethylhydrosiloxane (PMHS) as hydride source.