Iodine-Mediated Reaction of 2-Mercaptobenzimidazoles with Carbonyl Compounds via Sulfenamide Intermediates: Divergent Access to Imidazo[2,1-b]thiazoles and Thioenamines

An iodine-mediated reaction of 2-mercaptobenzimidazoles with carbonyl compounds in the presence of an amine additive has been developed. Proceeding through key sulfenamide intermediates, the transformation exhibits substrate-dependent reactivity. Aliphatic carbonyl compounds undergo α-sulfenylation, followed by intramolecular cyclization to furnish fused imidazo[2,1-b]thiazole derivatives. In contrast, reactions with aromatic methyl ketones or 1,3-dicarbonyl compounds selectively afford α-sulfenylated thioenamine products. This metal-free and operationally simple protocol highlights the crucial role of sulfenamide intermediates, enabling the divergent synthesis of structurally diverse sulfur-containing products from readily available starting materials with broad substrate scope and practical synthetic utility.