Reactions of quinones with aromatic ethers. Part I. Polyalkoxydibenzo[fg,op]naphthacene-1,8-quinones from chloranil and 3,3′,4,4′-tetra-alkoxybiphenyls

Abstract

Chloranil oxidises 3,3′,4,4′-tetramethoxybiphenyl efficiently in 70%(v/v) aqueous sulphuric acid to 2,5,6,9,12,13-hexamethoxydibenzo[fg,op]naphthacene-1,8-quinone (2; R¹= R²= R³= Me) from which are prepared the corresponding leucoacetate, the leucomethyl ether, and 1,2,5,6,8,9,12,13-octa-acetoxydibenzo[fg,op]naphthacene (3; R¹= R²= R³= Ac, X = OAc). Volatilisation of the quinone in the mass spectrometer is accompanied by abstraction of hydrogen and methyl groups. The oxidation of 3,3′-bistrideuteriomethoxy-4,4′-dimethoxybiphenyl (1; R¹= Me, R²= CD₃) gives a mixture of the expected [²H₁₂] quinone and a [²H₉]quinone(2; R¹= R³= Me, R²= CD₃) formed by intramolecular trans-etherification. 3,3′,4,4′-Tetraethoxybiphenyl is oxidised to 2,5,6,9,12,13-hexaethoxydibenzo[fg,op]naphthacenequinone (2; R¹= R²= R³= Et).