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Diversity and Chemoselectivity in the Acid-Catalyzed Rearrangements of N,N’- Diarylhydrazines

[ Vol. 14 , Issue. 4 ]

Author(s):

Jiaxi Xu   Pages 511 - 530 ( 20 )

Abstract:


The diversity and chemoselectivity in rearrangements of N,N’-diarylhydrazines are reviewed and summarized. The symmetric N,N’-diarylhydrazines without any para-substituents generally favor para-benzidine rearrangement accompanying diphenyline rearrangement, even semidine rearrangement in some cases, while those with single or double N-naphthyl(s) or double para-substituent phenyls undergo ortho-benzidine rearrangement accompanying ortho-semidine rearrangements occasionally because double and single nitrogen atom(s) are/is protonated. Some symmetric N,N’-diarylhydrazines with electron-withdrawing para-substituents take place predominately disproportionation reaction, resulting in the formation of the corresponding diaryldiazenes (azoarene compounds) and aromatic amines. However, unsymmetric N,N’-diarylhydrazines predominate semidine rearrangement(s) accompanied by the diphenyline rearrangement since electron-rich nitrogen atom is protonated favorably and non-protonated electron-poor nitrogen atom undergoes N[1,3] sigmatropic shift with inversion of the N atom configuration. Occurrence of ortho- and para-semidine rearrangements depends upon the substituted pattern of the unsymmetric N,N’-diarylhydrazines. Some N,N’-diarylhydrazines with strong electronwithdrawing substituents, especially para-substituents, are sensitive to air, favoring oxidation to generate azo product N,N’-diaryldiazenes.

Keywords:

Diarylhydrazines, rearrangement, chemoselectivity, benzidine, semidine, diphenyline.

Affiliation:

State Key Laboratory of Chemical Resource Engineering and Department of Organic Chemistry, Faculty of Science, Beijing University of Chemical Technology, Beijing 100029

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