Reaction of dichloroketene and sulfene with N,N‐disubstituted 6‐amino‐methylene‐b,7,8,9 ‐tetrahydro‐5H‐benzocyclohepten‐5‐ones. Synthesis of 6‐(2,2‐Dichloroethylidene)‐b,7,8,9‐tetrahydro‐5H‐benzocyclohepten‐5‐one and of 5H‐benzo[3,4]cyclohepta[2,l‐b]pyran and 5H‐Benzo[3,4]cyclo‐hepta[1,2‐e]‐1,2‐oxat

The 1,4-cycloaddition of dichloroketene to N,N-disubstituted 6-aminomethylene-b,7,8,9-tetra-hydro-5H-benzocyclohepten-5-ones afforded N,N-disubstituted 4-amino-3,3-dichloro-3,4,6,7-tetrahydro-5H-benzo[3,4]cyclohepta[2,l-b]pyran-2-ones only in the case of aromatic or strong hindering aliphatic N-substitution. The adducts gave N,N-disubstituted 4-amino-3-chloro-b,7-dihydro-5H-benzo[3,4]cyclohepta[2,l-b]pyran-2-ones by dehydrochlorination with collidine. Upon chromatography on neutral alumina, two products were instead isolated in the case of usual aliphatic N-substitution (diethylamine, piperidine), namely 6-(2,2-dichloroethylidene)-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-one and the dehydrochlorinated 2-pyrone; this latter was the sole product in the case of pyrrolidine substitution. The 1,4-cycloaddition of sulfene occurred readily to give N,N-disubstituted 4-amino-3,4,6,7-tetrahydro-5H-benzo[3,4]cyclohepta-[1,2-e]-1,2-oxathiin 2,2-dioxidesin the case of both aliphatic and partially aromatic N-substitution.