Ligand Controlled Highly Selective Copper-Catalyzed Borylcuprations of Allenes with Bis(pinacolato)diboron

Abstract Copper‐catalyzed highly selective borylcuprations of allenes with bis(pinacolato)diboron produce two different types of alkenylboranes by applying a ligand effect. In the presence of tris( para ‐methoxyphenyl)phosphine [P(C 6 H 4 OMe‐ p ) 3 ], the reaction of aryl‐1,2‐dienes affords 2‐alken‐2‐yl boronates as the only product with exclusive Z ‐geometry; the regioselectivity is switched to afford the 1‐alken‐2‐yl boronates as the major products when the bidentate phosphine 2,2′‐bis(diphenylphosphino)biphenyl is used as the ligand.