o-Quinonoid compounds. Part V. Derivatives of 2,3-naphthoquinone dimethide

Abstract

The synthesis of (3-benzoyl-2-naphthyl)phenylacetic acid (7; R = H) incorporating an improved synthesis of 2,2-dihydroxybenz[f]indene-1,3-dione is described. In boiling acetic anhydride the acid (7; R = H) is partly dehydrated to 1,4-diphenylnaphtho[2,3-c]pyran-3-one (5), which can be trapped with dimethyl maleate, dimethyl fumarate, or N-phenylmaleimide, with dimethyl maleate the exo-adduct is formed preferentially. 1,4-Diphenyl-benz[g]isoquinolin-3-ol is formed by reaction of the ester (7; R = Me) with liquid ammonia. It exists predominantly as the lactim tautomer in ethanol.