Synthesis of 6H-Dibenzopyran-6-ones via Dienone-Phenol Rearrangements of Spiro-3'-ones

Article abstract of DOI:10.1016/S0040-4020(01)80487-7

A series of spiro<2,5-cyclohexadiene-1,1'-(3'H)-isobenzofuran>-3'-ones were prepared from metallated benzamides and 4,4-dimethoxycyclohexadienone.Rearrangement of these spirodienones under a variety of conditions gave substituted 6H-dibenzopyran-6-ones.Rearrangements in aqueous sulfuric acid gave products of formal O-migration while rearrangements in trifluoroacetic anhydride-trifluoroacetic acid-sulfuric acid usually gave C-migration products.Key Words: dienone-phenol rearrangement; 6H-dibenzopyran-6-one, spiro<2,5-cyclohexadiene-1,1'(3'H)-isobenzofuran>-3'-one