Nitration of 4-Methoxyazoxybenzenes.

When 4-methoxy-NNO-azoxybenzene [1 a] was kept in 20% nitric acid (HNO3-AcOH-H2O)at 40°C, 4-methoxy-ONN-4'-nitroazoxybenzene (6β) was obtained as a nitration product but the isomerization of 1α to 4-methoxy-ONN-azoxybenzene [1β] did not take place at all. In this reaction, 4-methoxy-NNO-4'-nitroazoxybenzene [6α] formed by para-nitration of 1α seems to isomerize to 6β immediately. However, neither nitration nor isomerization took place in the reaction of 1β with 20% nitric acid (HNO3-AcOH-H2O) under the similar reaction conditions. It is co nvenient method to obtain pure 1β that is the nitration of a mixtare 1α and 1β with dilute nitric acid under the mild conditions.