Acid-catalysed rearrangement of 2,3,4,5-tetrahydrobenz[b]oxepin-2-spirocyclohexa-2′,5′-dien-4′-one and 3′,5′,7,9-tetra-t-butyl-2,3,4,5-tetrahydrobenz[b]oxepin-2-spirocyclohexa-2′,5′-dien-4′-one. Evidence for a quinone methide intermediate

Abstract

The title compounds have been obtained in 29 and 43% yield, respectively, by ferricyanide oxidation of the appropriate diphenols. Acid hydrolysis of the unsubstituted dienone leads to dienone–phenol rearrangement or ring opening depending on the concentration of the acid used in the hydrolysis. Under similar conditions the t-butylated dienone rearranges to a chroman which provides strong evidence for a quinone methide intermediate in this reaction.