Facile formation of acenaphtho[1,2-a]pyrene structures by thermal isomerization of bis(8-ethynyl-1-naphthyl)ethynes

The title 1,8-naphthylene–ethynylene compounds underwent thermal isomerization into acenaphtho[1,2-a]pyrene derivatives, and the structure of the new polycyclic aromatic system was established by X-ray analysis. The mechanism of the isomerization is explained in terms of sequential cyclization reactions via biradical intermediates followed by hydrogen migration.