Chemo-, Regio-, and Stereoselective cis -Hydroboration of 1,3-Enynes: Copper-Catalyzed Access to ( Z,Z )- and ( Z,E )-2-Boryl-1,3-dienes.

A copper-catalyzed alkyne-selective hydroboration of 1,3-enynes is disclosed, providing access to the previously elusive 2-boryl-1,3-dienes. Using CuOAc, Xantphos, and HBpin, Bpin was installed on the internal carbon of a series of symmetric and nonsymmetric 1,3-enynes, affording products with excellent Z : E selectivity. The utility of the 2-boryl-1,3-diene products was demonstrated by transformation to useful functional groups.