A convenient synthesis of 3‐alkyl‐2,3‐dihydro‐2,4‐dioxo‐6‐phenyl‐, 3‐alkyl‐2,3‐dihydro‐4‐oxo‐6‐phenyl‐2‐thioxo‐, and 3‐alkyl‐2‐arylimino‐2,3‐dihydro‐4‐oxo‐6‐phenyl‐4 H ‐1,3‐thiazines

The reactions of 1‐alkylamino‐1‐alkylthio‐3‐phenylpropene‐3‐thiones 3 with thiophosgene and phosgene in toluene, followed by treatment of the reaction mixture with triethylamine gave 3‐alkyl‐2,3‐dihydro‐4‐oxo‐6‐phenyl‐2‐thioxo‐ 4 , 3‐alkyl‐2,3‐dihydro‐2,4‐dioxo‐6‐phenyl‐4 H ‐1,3‐thiazines 5 , respectively in good to excellent yields. Similarly treatment of compounds 3 with N ‐arylimidoyl dichloride in benzene at room temperature gave 3‐alkyl‐2‐arylimino‐2,3‐dihydro‐4‐oxo‐6‐phenyl‐4 H ‐1,3‐thiazines 6 in excellent yields. The reactions of compounds 3 with oxalyl chloride in toluene gave also 5 in good yields.