Science of Synthesis

Rück-Braun, K.; Priewisch, B., Science of Synthesis, (2007) 31, 1348.

N-Arylhydroxylamines rather than the intermediate nitrosoarenes are usually obtained from the cathodic reduction of nitrobenzenes (see Section ‌31.22.1.2.4‌); however, if a batch process is conducted at −30°C in the presence of 6 equivalents of benzoic acid, nitrosobenzene can be obtained from nitrobenzene in 90% isolated yield.[‌120‌] On the other hand, anodic oxidations of N-arylhydroxylamines run in a similar manner often lead to the formation of diaryldiazene oxides through condensation reactions (see Section ‌31.24‌). In another more general approach a special redox flow cell consisting of a porous cathode and a porous anode, separated by a porous insulator, ensures short contact times and thereby provides good to excellent yields of nitrosoarenes. In such a cell nitro compounds are reduced to N-arylhydroxylamines at the cathode and then immediately oxidized to the corresponding nitrosoarenes at the anode.[‌121‌,‌122‌]

References

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