Bredereck synthesis

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The Bredereck synthesis , also Bredereck imidazole synthesis , is a name reaction in organic chemistry. It was first described in 1953 by the German chemist Hellmut Bredereck (1904–1981). It is used for the synthesis of 4,5-disubstituted imidazoles .

Overview reaction

This reaction makes it possible, starting from an α- hydroxyketone ( acyloin ) (R 1 , R 2 = alkyl), to synthesize 4,5-disubstituted imidazole .

Overview reaction of the Bredereck synthesis

Reaction mechanism

Bredereck synthesis - reaction mechanism

In the proposed reaction mechanism, the α-hydroxy ketone reacts at temperatures between 150 ° C and 180 ° C 1 with formamide to 2 . With elimination of water , the keto-enol equilibrium is formed . The keto form reacts with formamide to form 3 . After splitting off water, the carboxamide 4 is formed . By splitting off formic acid , the 4,5-disubstituted imidazole 5 is formed .

variants

Analogous to the above mechanism, an α- haloketone can also be reacted with formamide to form an imidazole. This reaction is similar to the imidazole synthesis according to R. Weidenhagen. Here, in the presence of copper (II) salts, the α-hydroxy ketone is reacted with ammonia and formaldehyde .

See also

Individual evidence

  1. ↑ Hellmut Bredereck, Gerhard Theiling: Imidazole syntheses with formamide (formamide reactions, I. Mitteil.). In: Chemischeberichte, 1953, Vol. 86, No. 1, pp. 88–96, https://doi.org/10.1002/cber.19530860117 .
  2. ↑ a b 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, p. 660, ISBN 978-3-13- 541507-9 .
  3. ↑ Entry on Bredereck imidazole synthesis. In: Römpp Online . Georg Thieme Verlag, accessed on April 13, 2020.
  4. ↑ a b H. Bredereck, R. Gompper, HGV Schuh, G. Theilig: Newer methods of preparative organic chemistry II. 16. Syntheses with acid amides, especially with formamide . In: Angewandte Chemie, Vol. 71, No. 24, pp. 753–776, https://doi.org/10.1002/ange.19590712402 .
  5. ↑ Rudolf Weidenhagen, Roland Herrmann: A new synthesis of imidazole derivatives . In: Reports of the German Chemical Society, 1935, Vol. 68, No. 10, pp. 1953–1961, https://doi.org/10.1002/cber.19350681012 .
  6. ↑ Helmut Krauch, Werner Kunz: Reactions of organic chemistry . John Wiley & Sons., 2009, Vol. 6, ISBN 9783527625123 , p. 405.