Benzocyclobutene has been prepared by a three-step route involving first the Diels-Alder addition of butadiene to dimethyl cyclobutene-1, 2-dicarboxylate. The resulting diester adduct may be hydrolyzed to the corresponding dicarboxylic acid which upon treatment with 2 equiv of lead tetraacetate undergoes bisdecarboxylation and aromatization of the six- membered ring. By substituting different dienes into this scheme, a series of his-annelated ...