CONDENSED CYCLOBUTANE AROMATIC COMPOUNDS .30. SYNTHESIS OF SOME UNUSUAL 2,3-NAPHTHOQUINONOID HETEROCYCLES . A SYNTHETIC ROUTE TO DERIVATIVES OF NAPHTHO[2,3-B]BIPHENYLENE AND ANTHRA[B]CYCLOBUTENE

The isolable, but highly reactive, 1,3-diphenylnaphtho[2,3-c]furan (9) has been prepared by a simple reaction sequence starting with 2,3-dimethylnaphthalene. Compound 9, which represents the first known stable 2,3-naphthoquinonoid substance, is an extremely reactive diene component in the Diels-Alder reaction: its reactivity exceeds that of its much studied lower benzolog, 1,3-diphenylbenzo[c]furan (7). A number of Diels-Alder adducts of 9 have been prepared, some of which have been aromatized; in this way, the synthesis of derivatives (36 and 47) of the naphtho[2,3-6]biphenylene and anthra[6]cyclobutene systems has been achieved. Reaction of 9 with phosphorus pentasulfide gives 1,3-diphenylnaphtho[2,3-c]thiophene (10), the first derivative of a new aromatic heterocyclic system. Thiophene 10 is a much less reactive diene in Diels-Alder additions than is furan 9, suggesting considerable resonance stabilization for the naphtho[2,3-c]thiophene system. © 1969, American Chemical Society. All rights reserved.