Benzidine rearrangement

from Wikipedia, the free encyclopedia

The benzidine rearrangement , also known as zinine reduction or sinine reduction , is a name reaction in organic chemistry. It was discovered in 1844 by the Russian chemist Nikolai Nikolajewitsch Sinin (1812-1880) in the reduction of nitrobenzene to aniline .

Overview reaction

In this reaction arises from hydrazobenzene (a N , N ' -Diarylhydrazin) in an intramolecular rearrangement in strongly acidic medium, benzidine (4,4'-diaminobiphenyl).

Overview reaction of the zinin reduction

Reaction mechanism

In the proposed reaction mechanism, the desired benzidine 4 is formed :

Zinin Reduction - Reaction Mechanism

It is assumed that hydrazobenzene 1 is initially doubly protonated under acidic catalysis, resulting in dication 2 . When this –N – N bond is cleaved in 2 , a π-complex-like transition state is formed in which the phenyl rings form a σ bond with one another in para to the amino groups , forming 3 . So there is an intramolecular rearrangement with the formation of the dication 3 . A double deprotonation of 3 with subsequent rearomatization leads to benzidine 4 .

Byproducts

The following by-products are produced in this reaction:

  • 2,2'-diamino-biphenyl

  • 2,4'-diamino-biphenyl

  • para- semidine

  • ortho- semidine

See also

Individual evidence

  1. ^ Georg Schwedt: Liebig and his students . Springer-Verlag, 2002, ISBN 3540432051 , p. 197 ( Google Books ).
  2. ↑ a b c Eberhard Breitmaier, Günther Jung: Organic Chemistry: Basics, Compound Classes, Reactions, Concepts, Molecular Structure, Natural Products, Synthesis Planning, Sustainability Vol. 7. Georg Thieme Verlag, Stuttgart, 2012, ISBN 978-3-13-541507-9 , Pp. 379-380; 453.
  3. ^ Otto-Albrecht Neumüller (editor): Römpps Chemie Lexikon 8th edition, Frank'sche Verlagshandlung, Stuttgart, 1983, ISBN 3-440-04513-7 , p. 4704.
  4. ↑ Bradford P. Mundy, Michael G. Ellerd, Frank G. Favaloro Jr .: Name Reactions and Reagents in Organic Synthesus, Second Edition . John Wiley & Sons, Inc., Hoboken, New Jersey, 2005, ISBN 9780471739876 , pp. 84-85, doi: 10.1002 / 9780471739876 .
  5. ↑ T. Laue, A. Plagens: Name and keyword reactions 4th edition, Teubner, Wiesbaden, 2004, ISBN 3-519-33526-3 , pp. 40-42.
  6. ↑ A.Hassner, I. Namboothiri: Organic Synthesis Based on Name Reactions A practical guide to 750 transformations, Elsevier Ltd, Amsterdam, 2012, ISBN 978-0-08-096630-4 , page 543rd