Sunlight Induced and Alternative Sc(OTf)3 Catalyzed Remote C−H Halogenation of Indoles

A mild and catalyst-free sunlight induced protocol for the remote meta bromination of electron-deficient indoles is described for the first time. Herein, N-bromosaccharin is activated by sunlight irradiation. Alternately, a synergistic activation model (Sc(OTf)3 /HFIP) has also been developed for the activation of haloniums, complementary to the light induced strategy. In addition, the cascade C6-H bromination and benzylic C-H oxidation under photocatalytic conditions was also discussed. High regio-and chem-selectivity, mild reaction conditions, and scalability demonstrate great potential of the developed methods in practical applications and further functionalization.