Visible-light-driven selective difluoroalkylation of α-CF3 alkenes to access CF2-containing gem-difluoroalkenes and trifluoromethylalkanes

An efficient visible-light-promoted selective difluoroalkylation of α-trifluoromethyl alkenes with difluoroalkylating reagents has been achieved via intermolecular difluoroalkyl radical addition mediated by photoredox catalysis under metal-free conditions. This transformation proceeded smoothly in the presence of the organic dye 4CzIPN, affording a series of gem-difluoroalkene difluoroacetates and trifluoromethylated difluoroacetamides in moderate to excellent yields. The chemoselectivity of the process (β-F elimination or protonation) is controlled by adjusting the bromodifluoro substrates. This protocol is distinguished by its mild conditions, wide scope, and exquisite chemoselectivity. Moreover, theoretical calculations revealed the important role of the N–H bond of bromodifluoroacetates in the control of the selectivity.