Acyl Azolium–Photoredox-Enabled Synthesis of β-Keto Sulfides
Michael J. Rourke, Charles T. Wang, Cullen R. Schull, Karl A. Scheidt
Abstract
α-Heteroatom functionalization is a key strategy for C–C bond formation in organic synthesis, as exemplified by the addition of a nucleophile to electrophilic functional groups, such as iminium ions; oxocarbenium ions; and their sulfur analogues, sulfenium ions. We envisioned a photoredox-enabled radical Pummerer-type reaction realized through the single-electron oxidation of a sulfide. Following this oxidative event, α-deprotonation would afford α-thio radicals that participate in radical–radical coupling reactions with azolium-bound ketyl radicals, thereby accessing a commonly proposed mechanistic intermediate of the radical–radical coupling en route to functionalized additive Pummerer products. This system provides a complementary synthetic approach to highly functionalized sulfurous products, including modification of methionine residues in peptides, and beckons further exploration in C–C bond formations previously limited in the standard two-electron process.