Addition Reactions of Heterocumulenes. IV. Reactions of Diketene and Diphenylketene with N-Aryl-S, S-dimethylsulfilimines

The reactions of diketene with S, S-dimethyl-N-2-pyridinylsulfilimine (IVa) and N-2-benzothiazolyl-S, S-dimethylsulfilimine (IVb) gave 2-(2-dimethylsulfuranylideneaceto-acetamido) pyridine (VIa) and 2-(2-dimethylsulfuranylideneacetoacetamido) benzothiazole (VIb), respectively. However, the reaction of diketene with S, S-dimethyl-N-(4-nitrophenyl) sulfilimine (IVc) and N-2-benzoxazolyl-S, S-dimethylsulfilimine (IVd) gave 3-acetyl-4-hydroxy-6-methyl-1-(4-nitrophenyl)-2-pyridone (VIIc) and 3-acetyl-1-(2-benzoxazolyl)-4-hydroxy-6-methyl-2-pyridone (VIId), respectively. On the other hand, the reaction of diphenylketene with sulfilimines (IVa, IVb, and IVd) gave the corresponding 1, 3-cyclization products (VIII, IX, and X).