Autoxidation of naphthols: a new entry to the perylene system

Abstract

Naphthols undergo autoxidation when adsorbed on silica gel and exposed to air, the main products being quinones. 2-Naphthol yields 4-(2-hydroxy-1-naphthyl)-1,2-naphthoquinone, and 4-methoxy-1-naphthol gives 4,4′-dimethoxy-2,2′-binaphthyl-1,1′quinone. 1,1′-Binaphthyl-2,2′,7,7′-tetrol turns blue on silica gel with formation of the anion of the tautomeric 6,7-dihydroxyperylene-1,12-quinone which is obtained more easily by autoxidation in aqueous solution. The same quinone can also be derived from naphthalene-2,7-diol in aqueous solution but on silica gel it forms the blue anion of 6,7-dihydroxy-3-(2,7-dihydroxy-1-naphthyl)perylene-1,1 2-quinone.