Formation of 2,6-dimethoxy-1,4-benzoquinone by the action of nitrous acid of 1,2,3-trimethoxybenzene

Abstract

Reduction of 1,2,3-trimethoxy-5-nitrobenzene (VI) with zinc and calcium chloride or with zinc and ammonium chloride yielded 3,3′,4,4′,5,5′-hexamethoxyazoxybenzene. In zinc, ammonium chloride, and a controlled amount of nitrous acid, (VI) yielded a compound C₁₈H₂₂N₄O₁₂Zn (IX), which appeared to be a stable complex of the dimer of 1,2,3-trimethoxy-5-nitrosobenzene and zinc nitrite. When treated with nitrous acid, (IX) yielded 2,5-dimethoxy-1,4-benzoquinone (V), but with hydrochloride acid gave a mixture of (V) and 4-hydroxyimino-2,6-dimethoxycyclohexa-2,5-dienone (IV). Since (V) is a product of the reaction of 1,2,3-trimethoxybenzene (I) with nitrous acid, it is proposed that 5-nitroso-1,2,3-trimethoxybenzene (II) and (IV) are intermediates in the latter reaction and that they are formed, in turn, by nitrodeprotonation and acid hydrolytic demethoxylation, respectively.