Rearrangement of substituted 2,4,4,6-tetraaryl-4H-thiopyrans to triaryl-3aH-benzo[3,4]cyclopenta[1,2-b]thiophene

摘要

An intensive bromination of 2,6-diaryl-4,4-diphenyl-4H-thiopyrans can lead through 3,5-dibromo derivatives to unexpected 2,8-diaryl-3-bromo- and 2,8-diaryl-3,5-dibromo-3a- phenyl-3aH-benzo[3,4] cyclopenta[1,2-b] thiophene as demonstrated on examples where the respective aryl groups are phenyl or 4-fluorophenyl. On the other hand, analogous spiro[ fluorene-9,4'-thiopyran] s do not exhibit the rearrangement evidently due to a rigid conformation of the fluorene moiety. The reaction mechanism for the rearrangement is proposed.