Boron‐Copper 1,3‐Rearrangement: the New Concept Behind the Boryl Migration from C(sp2) in Alkenyl Boranes to C(sp3)

Abstract

AbstractRegioselective borylcupration of borylated skipped (Z)‐dienes generates diborylated alkylcopper species that are involved in an intramolecular stereospecific B/Cu 1,3‐rearrangement by migration of Bpin moiety from C(sp2) to C(sp3). DFT mechanistic studies showed that boryl migration occurs through the formation of 4‐membered boracycle intermediate with a moderate free‐energy barrier. Moreover, the use of KOMe forms stable Lewis base adducts with Bpin moieties that blocks the reaction. Subsequently to the 1,3‐boron shift, the in situ electrophilic trapping allows selective C−H, C−C and C−X bonds, followed by intramolecular cross coupling giving access to cyclic functionalized alkylidenecyclohexanes or alkylidenecyclobutanes.