Studies in the Cycloproparene Series: Approaches to Cyclopropa[b]tetracenes

Abstract

Cyclopropa[b]naphthalene-3,6-dione (2) fails to add furan across the enedione olefinic bond in a Diels–Alder cycloaddition even at 14 × 10⁵ kPa. In contrast, isobenzofuran (4) adds efficiently at ambient temperature and pressure. The epoxytetracenedione (5) that is formed is air-sensitive and decomposes under conditions employed for dehydration. Aromatization of (5) to cyclopropatetracenedione (6) is not observed despite anthracene-1,4-dione (8) being obtained from its analogous tetrahydro precursor (7) under the same conditions.