Reductive quenching-initiated catalyst-controlled divergent alkylation of α-CF3-olefins

Abstract

Gem-difluoroalkenes and trifluoromethyl alkanes are pervasive in biologically active molecules. Photo-catalyzed alkylation of α-CF3-olefins provides a straightforward approach to access these scaffolds; however, such a strategy is often hampered, and gem-difluoroalkenes are usually formed instead of trifluoromethyl alkanes under reductive quenching-initiated photoredox conditions. It is both mechanistically and synthetically appealing if a simple change of the catalyst can chemo-selectively lead to either type of the products. Here, we show a visible-light-induced photo-catalyst strategy for preparing both gem-difluoroalkenes and trifluoromethyl alkanes from α-CF3-olefins. The chemo-selectivity of the reactions arises from a judicious choice of the catalyst rather than the modification of the substrate structures. A wide variety of substrates bearing an assortment of functional groups (62 examples) are compatible with this strategy. The use of HFIP as the additive promotes the formation of trifluoromethyl alkanes probably via the facilitation of hydrogen atom transfer step with O-H but not α-C-H bond.