Sommelet synthesis

from Wikipedia, the free encyclopedia

The Sommelet synthesis is a name reaction in organic chemistry and named after Marcel Sommelet , who first described the reaction in 1913. Sommelet synthesis is the conversion of alkyl halides, especially benzyl halides, with hexamethylenetetramine (urotropine) to form aldehydes . The reaction is also known under the names: Sommelet reaction, Sommelet oxidation or Sommelet aldehyde synthesis.

Overview of the Sommelet reaction

Reaction mechanism

The mechanism of the Sommelet reaction has been studied more often over the years. The reaction of benzyl halide with hexamethylenetetramine was usually considered as an example . For a long time it was assumed that a benzylamine and a primary imine of formaldehyde are formed, which are then subject to intermolecular hydrogen transfer. The primary imine of benzaldehyde should then be formed, which is then hydrolyzed to benzaldehyde . However, certain formamides as byproducts speak against this assumption.

Alternatively, the mechanism is described using the reaction of benzyl chloride with hexamethylenetetramine as follows: In the first step, benzyl chloride 1 is reacted with hexamethylenetetramine 2 by a nucleophilic attack of the nitrogen on the neighboring, positively polarized carbon atom to the chlorine. A quaternary hexaminium salt 3 is formed . The split off chloride ion ensures deprotonation of the hexaminium salt in the next step . Then the resulting iminium ion 4 is hydrolyzed, so that benzaldehyde 7 is obtained.

Mechanism of the Sommelet Reaction

Individual evidence

  1. ↑ a b M. Sommelet: In: Compt. Rend. 157, 1913, p. 852.
  2. ^ V. Franzen: On the mechanism of the Sommelet reaction . In: European Journal of Organic Chemistry . tape 600 , no. 2 , 1956, p. 109-114 , doi : 10.1002 / jlac.19566000205 .
  3. ^ A b Z. Wang: Comprehensive Organic Name Reactions and Reagents. 3 volumes. John Wiley & Sons, Hoboken, New Jersey 2009, ISBN 978-0-471-70450-8 , p. 2615.
  4. ↑ JD Hayler, SLB Howie, RG Giles, A. Negus, PW Oxley, TC Walsgrove, M. Whiter: Development of Large-Scale Syntheses of Ropinirole in the Pursuit of a Manufacturing Process . In: Org. Process Res. Dev. Band 2 , no. 1 , 1998, p. 3-9 , doi : 10.1021 / op970037c .