Polonovski reaction

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The Polonovski reaction is a rearrangement reaction of the amine oxides with acetic anhydride or, as in this example, with acetyl bromide (R 4 = CH 3 ). In this reaction, amides are obtained as a product from the amine oxides . An alkyl-nitrogen bond is split in the process. It is named after the Russian-French chemist Max Polonovski (1861 - 1939).

Gross equation of the Polonovski reaction

mechanism

It is assumed that initially the strongly negatively charged amine oxide oxygen atom is attacked electrophilically by the acetyl bromide and an ester-like positively charged compound is formed. An alkyl group is now deprotonated by a bromide ion and an iminium cation is formed with the elimination of an acetate ion. The attack of a molecule of acetyl bromide (R 4 = CH 3 ) then leads to a hemiaminal . Now the nitrogen atom is attacked again by a molecule of acetyl bromide and the hemiaminal breaks down to an amide and an aldehyde , and acetyl bromide (R 4 = CH 3 ) is split off again.

Mechanism of the Polonovski reaction

variants

If the reaction is carried out with trifluoroacetic anhydride , the reaction remains at the level of the iminium ion and is therefore available for other chemical reactions. This reaction is also known as the Potier-Polonovski reaction .

literature

  • László Kürti and Barbara Czakó: Strategic Applications of Named Reactions in Organic Synthesis: Background and Detailed Mechanisms , Elsevier Academic Press, 2005, ISBN 978-0-12-429785-2 .

Individual evidence

  1. ↑ AR Katritzky, JN Lagowski: In Chemistry of Heterocyclic N-oxide, Academic Press, New York, 1971 , 362 279th
  2. ↑ a b D. Grierson: In Org. React. 1990 , 39 , 85-295.
  3. ↑ DS Grierson, H.-P. Husson: In Comp. Org. Syn. 1991 , 6 , 909-924.
  4. ^ Rolf Huisgen , Friedrich Bayerlein, Wolfgang Heydkamp: In The Acylation of N, N-Dimethyl-arylamine-oxyde; the mechanism of the Polonovski reaction Chem. Ber. 1959 , 92 , 3 223-3241.
  5. ↑ Heinrich Volz, Liselotte Ruchti: In A Contribution to the Mechanism of the Polonovski Reaction Liebigs Ann. Chem. 1972 , 763 , 184-197.
  6. ^ A. Cave et al .: In Tetrahedron 1967 , 23 , 4681.
  7. ↑ T. Tamminen et al. : In Tetrahedron 1989 , 45 , 2683.
  8. ↑ RJ Sundberg, et al .: In Tetrahedron 1992 , 48 , 277.