A phenyl-group participation in the antisymmetric orbital interaction for [8 + 2] cycloaddition of tropothione with diphenylketene

Article abstract of DOI:10.1016/S0040-4039(00)97572-5

Reaction of tropothione (1) with diphenylketene (2) gives regiospecifically an [8 + 2] cycloadduct (3) in high yield. Twisted phenyl groups in 2 intermix two vacant FMOs of the ketene moiety. This mixing brings about an appropriate site for the antisymmetric orbital interaction against the HOMO of 1. A phenyl carbon is found to assist this interaction.