New synthesis of benzocyclobutene and annelated benzocyclobutenes

Benzocyclobutene (5) and a bis-annelated derivative (8) have been synthesized by the Diels-Alder addition of dimethyl cyclobut-1-ene-1,2-dicarboxylate (1) to an appropriate diene and subsequent aromatization of the resulting six-membered ring.