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Please login to access the full content or check if you have access via Method 2: Condensation of Nitrosoarenes with Arylamines in the Presence of a Base

DOI: 10.1055/sos-SD-031-01625

Rück-Braun, K.; Dietrich, S.; Kempa, S.; Priewisch, B.Science of Synthesis, (2007311459.

The condensation of nitrosoarenes with pyridin-2-amine to yield the corresponding hetaryldiazenes fails in pure glacial acetic acid, probably due to protonation of the nitrogen atom in the aromatic ring.[‌225‌] On the other hand, condensation of aryl and hetaryl nitroso compounds with pyridinamines and a series of other hetarylamines in aqueous sodium hydroxide furnishes the corresponding nitrogen-containing hetaryldiazenes 117, often in good yields (Scheme 52).[‌225‌‌229‌] In the absence of an arylamine, nitrosoarenes form diaryldiazene oxides under oxygen-free conditions, or nitroarenes in the presence of oxygen in an alkaline medium.[‌230‌] Therefore, the reaction is often carried out by gradually adding the nitroso compound to a solution of the arylamine in 50% aqueous sodium hydroxide over a period of 1030 minutes at a temperature between 60°C and reflux. In contrast to the condensation reaction in acetic acid, in an alkaline medium the reaction rate is enhanced by electron-withdrawing groups in the arylamine, while electron-releasing groups decrease it. In the nitroso compound, this effect of substituents on the reaction rate is reversed.[‌231‌] A drawback of the method is that toxic benzene is used as a cosolvent in many cases.

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