The acid-catalysed rearrangement of 2,3-dihydrobenzo[b]furan-2-spiro-1′-cyclohexa-2′,5′-dien-4′-one and 3,4-dihydro-2H-benzo[b]pyran-2-spiro-1′-cyclohexa-2′,5′-dien-4′-one

Abstract

The title compounds have been synthesised in low yields by intramolecular oxidative coupling of appropriate diphenols. They rearrange in acetic anhydride containing a trace of sulphuric acid to give high yields of 2-acetoxyxanthen and 2-acetoxydibenz[b,f]oxepin respectively. These rearrangements, which are related to those giving rise to many aporphine alkaloids, involve migration of aralkyl rather than of aryloxy-groups. Syntheses of 2- and 3-acetoxyxanthen and of 2-acetoxydibenz[b,f]oxepin are described.