Decarboxylative Radical Sulfilimination via Photoredox, Copper, and Brønsted Base Catalysis

Abstract Sulfilimines, the aza‐variants of sulfoxides, are key structural motifs in natural products, pharmaceuticals, and agrochemicals; and sulfilimine synthesis is therefore important in organic chemistry. However, methods for radical sulfilimination remain elusive, and as a result, the structural diversity of currently available sulfilimines is limited. Herein, we report the first protocol for decarboxylative radical sulfilimination reactions between sulfenamides and N ‐hydroxyphthalimide esters of primary, secondary, and tertiary alkyl carboxylic acids, which were achieved via a combination of photoredox, copper, and Brønsted base catalysis. This novel protocol provided a wide variety of sulfilimines, in addition to serving as an efficient route for the synthesis of S ‐alkyl/ S‐ aryl homocysteine sulfilimines and S ‐(4‐methylphenyl) homocysteine sulfoximine. Moreover, it could be used for late‐stage introduction of a sulfilimine group into structurally complex molecules, thereby avoiding the need to preserve labile organosulfur moieties through multistep synthetic sequences. A mechanism involving photocatalytic substrate transformation and copper‐mediated C(sp 3 )−S bond formation is proposed.