Enantio‐ and Diastereoselective Copper‐Catalyzed Allylboration of Alkynes with Allylic gem‐Dichlorides

Allylic gem‐dichlorides are shown to be efficient substrates for catalytic asymmetric allylboration of alkynes. The method employs a chiral NHC−Cu catalyst capable of generating in a single step chiral skipped dienes bearing a Z‐alkenyl chloride, a trisubstituted E‐alkenyl boronate and a bis‐allylic stereocenter with excellent levels of chemo‐, regio‐ enantio‐ and diastereoselectivity. This high degree of functionalization makes these products versatile building blocks as illustrated with the synthesis of several optically active compounds. DFT calculations support the key presence of a metal cation bridge ligand–substrate interaction and account for the stereoselectivity outcome. A highly chemo‐, regio‐, enantio‐ and diastereoselective coupling of terminal alkynes, bis(pinacolato)diboron and allylic gem‐dichlorides is reported. The method uses a chiral NHC−Cu catalyst which generates, in a single step, synthetically versatile chiral skipped dienes bearing a Z‐alkenyl chloride, a trisubstituted E‐alkenyl boronate and a bis‐allylic stereocenter.