Photoredox Autocatalysis: Towards a Library of Generally Applicable Sulfonamide Reductive Photocatalysts

Abstract Dichotomous thinking dominates the field of synthetic photochemistry—either a reaction needs a photocatalyst or not. Herein, we report the identification of a photoredox autocatalytic pathway ‐ an alternative to the existing mechanistic paradigms ‐ to access cyclic biaryl sulfonamides (BASNs). This reaction does not require exogenous catalyst as the visible light absorbing deprotonated product ‐ with potent excited state reductive power ‐ acts as the photocatalyst for its own synthesis. This finding implicated BASN as a novel organophotocatalyst architecture and allowed a rapid, modular, and low‐cost combinatorial synthesis of a BASN library that expedited optimal photocatalyst screening. Furthermore, BASN was revealed as a widely applicable organophotocatalyst for diverse transition metal‐free transformations such as: intramolecular (spiro)‐cyclizations, defunctionalizations, and C−C / C‐heteroatom couplings.