Regioselective Radical Borylation of α,β-Unsaturated Esters and Related Compounds by Visible Light Irradiation with an Organic Photocatalyst.

Radical hydroboration reactions have only recently been reported and are still rare. Here we describe a photoredox radical hydroboration of α,β-unsaturated esters, amides, ketones, and nitriles with NHC-boranes that uses only an organocatalyst and visible light. The conditions are mild, the substrate scope is broad, and the α/β regioselectivity is high. The reaction requires only the organocatalyst; there is no costly metal, and there are no other additives (base, cocatalyst, initiator).