Construction of dibenzo-fused seven- to nine-membered carbocycles via Brønsted acid-promoted intramolecular Friedel–Crafts-type alkenylation

Abstract

Brønsted acid-promoted intramolecular hydroarylation of alkynylbenzenes carrying an arylalkyl group at the ortho-position leads to alkylidenedibenzo[a,d]cycloheptenes, -octenes and -nonenes in up to quantitative yield with complete regioselectivity. The scope and limitation of this reaction and application to the synthesis of tricyclic antidepressants are described.