Green and Practical Synthesis of Thioenamines and Chromones via Iodine-Catalyzed Cross-Dehydrogenation Coupling Reaction

An iodine-catalyzed one-pot synthesis of thioenamines and chromones is reported. By using easily available phenyl isothiocyanate, alcohols, and enamines as starting materials, a tandem reaction (nucleophilic addition and the subsequent cross-dehydrogenation coupling) proceeded smoothly to give the desired thioenamines in good to excellent yields. This protocol features simple operation, mild conditions, a broad substrate scope, good atomic economics, and no need to add extra reaction solvents, providing a practical and green route for the synthesis of thioenamines. In addition, this method can also prepare some representative chromones in moderate yields.