Photoinduced Reductive Elimination from Sulfur Enables a Unique Synthetic Valorization of Sulfonamides

A photochemical desulfonylation of sulfonamides has been discovered. Sulfonamides are abundant in medicinal-chemistry libraries. Strategies for their synthetic valorization remain relatively sparse, however, and their known reactions overwhelmingly retain the sulfonyl group, limiting the chemical space accessible from sulfonamides. Using this new method, an extensive array of aromatic sulfonamides bearing a selection of N-heteroaryl substituents was converted into the corresponding N-heteroaryl anilines, which are also medicinally important substructures. This reaction involves a unique photoinduced C-N reductive elimination from sulfur, which is proposed mainly to involve an excited-state, desulfonylative S-to-N aryl migration. An analogous polar aryl migration from a higher-energy, photogenerated sulfonamide tautomer was also identified, which likely serves as a minor pathway.