Cobalt‐Catalyzed Regio‐ and Stereoselective Hydroboration of Allenes

Abstract An efficient pincer‐ligand‐based cobalt‐complex‐catalyzed allene hydroboration affording Z ‐allylic boronates is described. The reaction demonstrates an excellent regio‐ as well as Z ‐stereoselectivity and a wide substrate scope that tolerates many functional groups. Based on solvent‐assisted electrospray ionization mass spectrometry (SAESI‐MS) studies, a rationale for the cobalt‐catalyzed hydroboration involving the highly selective insertion of an allene into the Co−H bond to form Z ‐allylic cobalt intermediates is proposed.