Iodine-Catalyzed Coupling of α-Bromoketone-Derived Bunte Salts with β-Enaminonitriles: Access to Thiazole-5-carbonitriles via In Situ Thiazine Formation and Skeletal Editing

An iodine-catalyzed coupling of α-bromoketone-derived Bunte salts and β-enaminonitriles is described for the synthesis of 2,4-diarylthiazole-5-carbonitriles. The transformation was identified during attempts to access functionalized 1,4-thiazines and afforded a range of cyano-substituted thiazoles from readily available starting materials. Single-crystal X-ray diffraction analysis established the structure of a representative product as 2,4-diarylthiazole-5-carbonitrile. On the basis of the experimental observations and literature precedents, a plausible reaction pathway involving sulfur incorporation, cyclization, and skeletal editing through one-carbon deletion is proposed.