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‐7H‐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‐7H‐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‐7H‐pyrano[2,3‐e]indol‐4‐one, as a result of dehydrochlorination, dehydrogenation and subsequent hydrogenolysis of the C‐NR2 bond in the primary adduct. Copyright © 1979 Journal of Heterocyclic Chemistry