SYNTHESIS OF BROMONAPHTHOQUINONES FROM 1,5-DIMETHOXYNAPHTHALENE

New regiospecific syntheses of 2-bromo-5-methoxy-l, 4-naphthoquinone and 3-bromo-5-methoxy-l, 4-naphthoquinone have been developed via 4, 8-dimethoxy-l-naphthalenecarboxaldehyde, prepared by formylation of 1, 5-dimethoxynaphthalene. The naphthaldehyde, on oxidation with m-chloroperbenzoic acid and hydrolysis of the intermediate formate, gave 4, 8-dimethoxy-l-naphthol. Bromination followed by oxidation of the bromonaphthol gave 3-bromo-5-methoxy-l, 4-naphthoquinone in 58% overall yield from 1, 5-dimethoxynaphthalene. The naphthol may also be oxidized to 5-methoxy-l, 4-naphthoquinone (juglone methyl ether), which was then brominated to give 2-bromo-5-methoxy-1, 4-naphthoquinone in 49% overall yield from 1, 5-dimethoxynaphthalene. These syntheses offer the advantages of ease of manipulation, increased yields, and purity. © 1979, American Chemical Society. All rights reserved.