Science of Synthesis

Purchase, R.; Sainsbury, M., Science of Synthesis, (2009) 40, 391.

The reaction known as the Bamberger rearrangement involves the conversion of an N-phenylhydroxylamine into the corresponding 4-aminophenol through treatment with an aqueous mineral acid such as sulfuric acid.[‌145‌,‌146‌] A recent recommendation highlights phosphinic acid as a bifunctional reagent for a catalytic version of this rearrangement.[‌147‌] Prior to the commencement of the Bamberger rearrangement, N-protonation of the nitrogen atom of the hydroxylamine is favored, but as this is unproductive, less favored O-protonation is needed to facilitate a subsequent loss of water and the formation of a nitrenium ion. This last species then reacts with water to form the rearrangement product 4-aminophenol {‌Scheme 39‌; for an experimental procedure, see Science of Synthesis, Vol. 31b [Arene—X (X = N, P) (Section ‌31.28.1.33.7‌)]}.[‌148‌–‌150‌] Besides N-phenylhydroxylamine the rearrangement has been studied for a range of methylated derivatives as well as N-(2-chlorophenyl)hydroxylamine and, where appropriate, only the para-substituted aminophenol is detected. However, the addition of sodium halides (NaCl or NaBr) gives reduced yields and leads to the incorporation of a halogen rather than a hydroxy group. When sodium bromide is present the parent aniline may be obtained.[‌151‌] The Bamberger rearrangement of N,S-diarylsulfenamides to give 4-sulfanylanilines is discussed in Science of Synthesis, Vol. 31b [Arene—X (X = N, P) (Section ‌31.28.1.33.1‌31.28.1.33.1)].

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References

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• 8.Meeeee-Meee, (8888) 88/8, 888.
• 8.Meeeee-Meee, (8888) M 88e8, 8888.