Illuminating Synergistic Catalysis: SET-HAT Unlocks Proximal C–H Arylation of Aromatic Amines

The regioselective arylation of a free aromatic amine moiety is a challenging synthetic process, yet it is an essential one in the development of many value-added compounds. Here, we present an alternate strategy for the photoinduced <i>ortho</i> C-H arylation of anilines and alpha-arylation of pyrrole with aryl halides through the synergistic catalysis with the assistance of SET-HAT by the formation of noncovalent adducts. This synergistic strategy involving the thiol and the formate salt has been exploited to perform transition metal-free organophotocatalytic arylations. A diverse array of aryl halides and aromatic amine moieties have been coupled to remarkable regioselectivity. The plausible reaction pathways were further defined by spectroscopic investigation and computational studies. This proximal C-H arylation strategy has been utilized for late-stage functionalization as well as in the synthesis of bioactive phenanthridine and phenanthridinone via the domino annulation reaction.