Regioselective Hydroboration of Unsymmetrical Internal Alkynes Catalyzed by a Cobalt Pincer-NHC Complex.

Highly regioselective hydroboration of unsymmetrical internal alkynes remains a significant challenge for synthesizing valuable alkenylboronate esters. Herein, we describe an easily synthesizable pincer NHC-based Co complex as a catalyst for the -α selective hydroboration of unactivated internal alkynes and the -β selective hydroboration of activated internal alkynes with pinacolborane. The reaction showcases high chemo-, regio-, and stereoselectivity, and the catalyst displays high efficiency and very low loading under base-free reaction conditions.