Reaction of dichloroketene and sulfene with N,N ‐disubstituted α‐aminomethyleneketones. Synthesis of pyrano[2,3‐ e ]indazole and 1,2‐oxathiino[6,5‐ e ]indazole derivatives

The polar 1,4‐cycloaddition of dichloroketene to N,N ‐disubstituted ( E )‐5‐aminomethylene‐1,5,6,7‐tetrahydro‐(1‐methyl)(1‐phenyl)‐4 H ‐indazol‐4‐ones V, prepared from 1,5,6,7‐tetrahydro‐(1‐methyl)(1‐phenyl)‐4 H ‐indazol‐4‐ones via the 5‐hydroxymethylene derivatives, gave in good yield N,N ‐disubstituted 4‐amino‐3,3‐dichloro‐4,5,6,7‐tetrahydro‐(7‐methyl)(7‐phenyl)pyrano[2,3‐ e ]indazol‐(3 H )ones VI, which are derivatives of the new heterocyclic system pyrano[2,3‐ e ]indazole. Dehydrochlorination of VI with DBN afforded N,N ‐disubstituted 4‐amino‐3‐chloro‐6,7‐dihydro(7‐methyl)(7‐phenyl)pyrano[2,3‐ e ]indazol‐2(5 H ]‐ones VII generally in satisfactory yield. Full aromatization with DDQ of VII was tried only in the case of dimethylamino derivatives, giving a moderate yield of 3‐chloro‐4‐dimethylamino(7‐methyl)(7‐phenyl)pyrano[2,3‐ e ]indazol‐2(7 H )‐ones. Cycloaddition of sulfene to V occurred only in the case of aliphatic N ‐substitution to give in moderate yield 4‐dialkylamino‐4,5,6,7‐tetrahydro‐(7‐methyl)(7‐phenyl)‐3 H ‐1,2‐oxathiino[6,5‐ e ]indazole 2,2‐dioxides, which are derivatives of the new heterocyclic system 1,2‐oxathiino[6,5‐ e ]indazole.