Urech hydantoin synthesis

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The urech hydantoin synthesis is a name reaction in organic chemistry . It was named after Friedrich Urech , who published the reaction in 1873. With this reaction hydantoins can be produced from α- amino acids .

Overview reaction

In an acidic reaction medium, α-amino acids react with potassium cyanate ( blue ) to form 5-substituted hydantoins:

R = organic residue or hydrogen

If amino acids with a substituted amino group ( green ) are used in the reaction , 1- N -substituted hydantoins are formed.

mechanism

This name reaction is a two-step reaction in which hydantoic acid 8 can be isolated. This can then be reacted with hydrochloric acid and hydanoins 11 can also be produced in this way.

R = organic residue or hydrogen

First, the amino group deprotonates the carboxy group of amino acid 1 and forms the zwitterion 2 . The ammonium group 2 is deprotonated to a carboxylate 3 by the cyanate ion . Its amino group then nucleophilically attacks the carbon atom of the cyanic acid ( 4 ). This is followed by a 1,3 proton transfer from the nitrogen atom to the negatively charged nitrogen atom of the former cyanate 5 and thus the formation of an imine 6 . The amide 7 is formed by a renewed transfer of protons . The protonation of the carboxylate group on amide 7 leads to the intermediate hydantoic acid 8 . This is followed by an intramolecular attack by the amino group 8 on the carbonyl group, which leads to the closure of a heterocyclic five-membered ring 9 . When a diol 10 is formed by proton transfer, hydantoin 11 is formed after water is split off .

Even today, the reaction is still an important variant for the production of hydantoins.

See also

Individual evidence

  1. ↑ a b c d e f Z. Wang: Comprehensive Organic Name Reactions and Reagents, 3 Volume Set . John Wiley & Sons, Hoboken, New Jersey 2009, ISBN 978-0-471-70450-8 , pp. 2856 f.
  2. ↑ F. Urech: XXI. About lacturamic acid and lactylurea . In: Justus Liebig's Annals of Chemistry . tape 165 , no. 1 , 1873, p. 99-103 , doi : 10.1002 / jlac.18731650110 .
  3. ^ E. Ware: The Chemistry of the Hydantoins . In: Chem. Rev. Band 46 , no. 3 , 1950, p. 403-470 , doi : 10.1021 / cr60145a001 .
  4. ↑ C. Harries, M. Weiss: About a way of representing the Hydantoin . In: Reports of the German Chemical Society . tape 33 , no. 3 , 1900, p. 3418-3420 , doi : 10.1002 / cber.190003303122 .
  5. ↑ A. Mouneyrat: transformation of the α-amino acids in Phenylhydantoïne . In: Reports of the German Chemical Society . tape 33 , no. 2 , 1900, p. 2393-2396 , doi : 10.1002 / cber.190003302166 .