Bamberger rearrangement

Short description: Chemical reaction

The Bamberger rearrangement is the chemical reaction of phenylhydroxylamines with strong aqueous acid, which will rearrange to give 4-aminophenols.[1] It is named for the German chemist Eugen Bamberger (1857–1932).[2][3]

The Bamberger rearrangement

The starting phenylhydroxylamines are typically synthesized by the transfer hydrogenation of nitrobenzenes using rhodium[4] or zinc[5] catalysts.

One application is in the synthesis of fenhexamid (fr).

## Reaction mechanism

The mechanism of the Bamberger rearrangement proceeds from the monoprotonation of N-phenylhydroxylamine 1. N-protonation 2 is favored, but unproductive. O-protonation 3 can form the nitrenium ion 4, which can react with nucleophiles (H2O) to form the desired 4-aminophenol 5.[6][7]

The mechanism of the Bamberger rearrangement

## See also

* Friedel–Crafts alkylation-like reactions:
* Hofmann–Martius rearrangement
* Fries rearrangement
* Fischer–Hepp rearrangement
* Wallach rearrangement
* Bamberger triazine synthesis — same inventor

## References

1. ↑ Harman, R. E. (1955). "Chloro-p-benzoquinone". Organic Syntheses 35: 22. http://www.orgsyn.org/Content/pdfs/procedures/CV4P0148.pdf. ;  Collective Volume, 4, pp. 148
2. ↑ Bamberger, E. (1894). "Ueber die Reduction der Nitroverbindungen". Chemische Berichte 27 (2): 1347–1350. doi:10.1002/cber.18940270229. http://gallica.bnf.fr/ark:/12148/bpt6k907342/f163.
3. ↑ Bamberger, E. (1894). "Ueber das Phenylhydroxylamin". Chemische Berichte 27 (2): 1548–1557. doi:10.1002/cber.18940270276. http://gallica.bnf.fr/ark:/12148/bpt6k907342/f376.table.
4. ↑ Oxley, P. W.; Adger, B. M.; Sasse, M. J.; Forth1, M. A. (1989). "N-Acetyl-N-Phenylhydroxylamine Via Catalytic Transfer Hydrogenation of Nitrobenzene Using Hydrazine and Rhodium on Carbon". Organic Syntheses 67: 187. doi:10.15227/orgsyn.067.0187.
5. ↑ Kamm, O. (1925). "β-Phenylhydroxylamine". Organic Syntheses 4: 57. http://www.orgsyn.org/orgsyn/prep.asp?prep=cv1p0445. ;  Collective Volume, 1, pp. 445 (download PDF)
6. ↑ Sone, T.; Hamamoto, K.; Seiji, Y.; Shinkai, S.; Manabe, O. (1981). "Kinetics and Mechanisms of the Bamberger Rearrangement. Part 4. Rearrangement of Sterically Hindered Phenylhydroxylamines to 4-Aminophenols in Aqueous Sulphuric Acid Solution". Journal of the Chemical Society, Perkin Transactions 2 1981 (2): 1596–1598. doi:10.1039/P29810000298.
7. ↑ Kohnstam, G.; Petch, W. A.; Williams, D. L. H. (1984). "Kinetic Substituent and Isotope Effects in the Acid-Catalysed Rearrangement of N-Phenylhydroxylamines. Are Nitrenium Ions Involved?". Journal of the Chemical Society, Perkin Transactions 2 1984 (3): 423–427. doi:10.1039/P29840000423.

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Topics in Organic Reactions

* Addition reaction
* Elimination reaction
* Polymerization
* Reagents
* Rearrangement reaction
* Redox reaction
* Regioselectivity
* Stereoselectivity
* Stereospecificity
* Substitution reaction

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