Copper-catalyzed boration of activated alkynes. Chiral boranes via a one-pot copper-catalyzed boration and reduction protocol

Phosphine–copper(I) complexes efficiently catalyzed the mono-boration of electron-deficient alkynes in the presence of MeOH and also catalyzed conjugate reductions of alkenylboronates bearing an electron-withdrawing group. The mono-addition of bis(pinacolato)diboron to alkynes catalyzed by a copper–Xantphos complex produced vinylboronates with high regio and stereoselectivity and asymmetric reduction of the vinylboronates by a chiral copper–bisphosphine catalyst allowed the synthesis of valuable chiral boranes with high enantioselectivity. One-pot boration/asymmetric reduction of α,β-unsaturated alkynoates could be conducted with a single copper–phosphine catalyst.