The
incorporation of gem-difluoromethylene units into organic molecules
remains a formidable challenge. Conventional methodologies for constructing
aryldifluoromethyl derivatives relied on the use of high-functional
fluorinating regents under harsh conditions. Herein, we report general
and efficient photoredox catalytic systems for defluoroalkylation
of readily available trifluoromethylarenes through selective C–F
cleavage to deliver gem-difluoromethyl radicals which proceed through
reductive addition to both electron-donating and withdrawing alkenes
under transition-metal free conditions. Mechanistic studies reveal
that thiol serves as both photocatalyst and HAT reagent under visible
light irradiation. This synergistic photocatalysis and HAT catalysis
protocol exhibits ample and salient features such as high chemo- and
regioselectivity, broad substrate scope, amenable gram-scale synthesis
and late-stage modification of bioactive molecules.