The preparation of substituted 3,4-dihydro-1(2H)-naphthalenones from benzocyclobutenones via sequential thermal electrocyclic reactions

1-Alkenylbenzocyclobutenols, prepared from benzocyclobutenones via the addition of alkenyl Grignard reagents or the addition of alkynyllithium reagents followed by (E)-selective reduction, undergo successive thermal 4 pi and 6 pi electrocyclisations to give substituted 3,4-dihydro-1(2H)-naphthalenones. An analogous sequence gave 3,4-dihydro-1(2H)-anthracenone from naphtho[b]cyclobuten-1(2H)-one.