Tandem [4+2] Cycloaddition/Aromatization Sequence of Allenyl 2-Bromo-3-vinylcyclohex-2-enyl Thioether to Naphtho[1,8-bc]thiophene

A concise synthetic route of tetrahydro-3H-naphtho[1,8-bc]thiophene was developed. Allenyl 2-bromo-3-vinylcyclohex-2-enyl thioether underwent a tandem [4+2] cycloaddition/aromatization sequence to produce the naphthothiophene with high yield. A density functional study for the transition and reaction enthalpies was performed to elucidate the details of the reaction.