Photoredox Autocatalysis: Towards a Library of Generally Applicable Reductive Photocatalysts

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 itself, 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.