Reaction of sulfene and dichloroketene with N,N ‐disubstituted 5‐aminomethylene‐1,5,6,7‐tetrahydro‐2‐methyl‐1‐phenylindol‐4‐ones. Synthesis of 1,2‐oxathiino[6,5‐ E ] indole and of pyrano[2,3‐ e ] indole derivatives

The 1,4‐cycloaddition of sulfene to N,N ‐disubstituted 5‐aminomethylene‐1,5,6,7‐tetrahydro‐2‐methyl‐1‐phenylindol‐4‐ones afforded N,N ‐disubstituted 3,4,5,6‐tetrahydro‐8‐methyl‐7‐phenyl‐7 H ‐1,2‐oxathiino[6,5‐ e ]indol‐4‐amine 2,2‐dioxides only in the case of aliphatic N ‐substitution. The 1,4‐cycloaddition of dichloroketene occurred normally only in the case of 1,5,6,7‐tetrahydro‐2‐methyl‐1‐phenyl‐5‐piperidinomethyleneindol‐4‐one to give 3,3‐dichloro‐3,4,5,6‐tetrahydro‐8‐methyl‐7‐phenyl‐4‐piperidino‐7 H ‐pyrano[2,3‐ e ]indol‐4‐one. Attempted recrystallisation, dehydro‐chlorination or treatment with palladium on carbon of this adduct, as well as reaction of similar enaminoketones with dichloroketene, gave instead the same product, namely 3‐chloro‐8‐methyl‐7‐phenyl‐7 H ‐pyrano[2,3‐ e ]indol‐4‐one, as a result of dehydrochlorination, dehydrogenation and subsequent hydrogenolysis of the C‐NR 2 bond in the primary adduct.