Regiocontrolled Rh(III)-catalyzed C C coupling/C N cyclization mediated by distinctive 1,2-migratory insertion of gem‑difluoromethylene allenes: Reaction development and mechanistic insight

By developing gem‑difluoromethylene allenes as viable partners, regiocontrolled Rh(III)-catalyzed redox-neutral CC coupling/CN cyclization has been realized to build the pyridin-2(1H)-one motifs with the embedment of a Z-configured monofluoroalkene functionality, in which either (hetero)aromatic or vinylic amides were found to be compatible. Integrated experimental and computational mechanistic studies revealed that a tandem regioselective allene 1,2-insertion/β-H elimination/hydrogen transfer/oxidative addition/cyclization/cis-β-F elimination involving an unconventional Rh(III)-Rh(I)-Rh(III) catalytic cycle accounts for the established transformation. Through further FMO analysis and IGMH maps, a non-covalent weak interaction network between the gem‑difluoromethylene part and the OPiv moiety was rationally defined for the unconventional and specific regioselectivity control.