Photoinduced transition-metal and external photosensitizer free phosphonation of unactivated C(sp2)–F bond via SET process under mild conditions

Abstract

Transition-metal catalyzed cross-couplings of aryl halides (ArI, ArBr and ArCl) with a broad range of nucleophiles have been developed as powerful methods for carbon–carbon and carbon–heteroatom bonds formation. However, due to the high bond dissociation energy of unactivated C(sp2)–F, cross-couplings of mono-fluoroarenes are the most challenging, especially without using transition-metal catalysts. Herein, a photo-induced transition-metal and external photosensitizer free defluorophosphonation of monofluoroarenes via unactivated C(sp2)–F bond cleavage is reported. Different mono-fluoroarenes have been successfully cross-coupled with dialkyl phosphites in moderate to excellent yields under mild conditions. Mechanistic studies have revealed the possible involvement of a photo-induced SET process and aryl free radical intermediates.