Cobalt-catalyzed controllable defluorinative alkylation of α -trifluoromethyl alkenes for the selective synthesis of gem -difluoroalkenes and monofluoroalkenes

Cobalt-catalyzed defluorinative alkylation of α -trifluoromethyl alkenes with alkyl bromides selectively affords gem -difluoroalkenes or ( E )-monofluoroalkenes by condition control, with broad scope and good tolerance.