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

摘要

By developing gem-difluoromethylene allenes as viable partners,regiocontrolled Rh(Ⅲ)-catalyzed redoxneutral C-C coupling/C-N 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.