Applications of the spiroannulation of tetralins with alkynes; towardsnew anti-estrogenic compounds

Thermal reaction of the benzocyclobutene 17 with 4-methoxystyrene leads to 1-cyano-2-(4-methoxyphenyl)-6-methoxytetralin† 19 through an electrocyclic ring opening Diels–Alder sequence: the derived acid chloride 20, and its analogue 10, then undergoes an unusual addition–cyclisation reaction with alkynes catalysed by aluminium chloride, to yield the tricyclospirodienones 21a–c and 11a,b; the former set show moderate aromatase inhibitory activity.