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General Characteristics
Under acidic conditions, 1,2-diphenylhydrazines are known to rearrange into 4,4’-diaminobiphenyls (benzidines).
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General References
- Hofmann, A. W. Proc. Roy. Soc. London 1863, 12, 576.
- Jacobson, P. et al. Ber.1893, 26, 688.
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Reaction Mechanism
The rearrangement is thought to proceed via concerted [5,5]-sigmatropic rearrangement. (Ref: J. Am. Chem. Soc. 1981, 103, 955; J. Am. Chem. Soc. 1982, 104, 2501; J. Am. Chem. Soc. 1984, 106, 7077.) 
When the para position is substituted, rearrangement occurs at the ortho position ([3,3]-sigmatropic rearrangement, the diaza-Cope rearrangement).
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Examples
In 2013, List and Kürti independently reported asymmetric benzidine rearrangement catalyzed by chiral phosphoric acids, demonstrating the synthesis of 1,1’-binaphthyl-2,2’-diamine (BINAM) in impressively high yields and enantioselectivities.[1]
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Experimental Procedure
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Experimental Tips
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References
[1] (a) Kanta, C.; Fabio, D.; Pesciaioli, F.;List, B. Angew. Chem. Int. Ed. 2013, 52, 9293. DOI: 10.1002/anie.201304039 (b) Li, G-Q.; Gao, H.; Keene, C.; Devonas M.; Ess, D.H.; Kürti, L. J. Am. Chem. Soc.. 2013, 135, 7414 DOI: 10.1021/ja401709k
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Related Reactions
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Related Books
[amazonjs asin=”0080966306″ locale=”US” title=”Organic Syntheses Based on Name Reactions, Third Edition: a practical guide to 750 transformations”]
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External Links