Cobalt-Catalyzed Selective Unsymmetrical Dioxidation of gem-Difluoroalkenes

Abstract

gem-Difluoroalkenes represent valuable synthetic handles for organofluorine chemistry; however, most reactions of this substructure proceed through reactive intermediates prone to eliminate a fluorine atom and generate monofluorinated products. Taking advantage of the distinct reactivity of gem-difluoroalkenes, we present a cobalt-catalyzed regioselective unsymmetrical dioxygenation of gem-difluoroalkenes using phenols and molecular oxygen which retains both fluorine atoms and provides α-phenoxy-α,α-difluorobenzyl alcohols. Mechanistic studies suggest that the reaction operates through a radical chain process initiated by Co(II)/O₂/phenol and quenched by the cobalt-based catalyst. This mechanism enables the retention of both fluorine atoms, which contrasts most transition metal-catalyzed reactions of gem-difluoroalkenes that typically involve defluorination.