Debus–Radziszewski imidazole synthesis

The Debus–Radziszewski imidazole synthesis is a multi-component reaction used for the synthesis of imidazoles from a 1,2-dicarbonyl, an aldehyde, and ammonia or a primary amine. The method is used commercially to produce several imidazoles.[1] The process is an example of a multicomponent reaction.

Debus–Radziszewski imidazole synthesis
Named after Heinrich Debus
Bronisław Leonard Radziszewski
Reaction type Ring forming reaction

The reaction can be viewed as occurring in two stages. In the first stage, the dicarbonyl and two ammonia molecules condense with the two carbonyl groups to give a diimine:

In the second stage, this diimine condenses with the aldehyde:

However, the actual reaction mechanism is not certain.[2][3]

This reaction is named after Heinrich Debus[4] and Bronisław Leonard Radziszewski.[5][6]

A modification of this general method, where one equivalent of ammonia is replaced by an amine, affords N-substituted imidazoles in good yields.[3]

This reaction has been applied to the synthesis of a range of 1,3-dialkylimidazolium ionic liquids by using various readily available alkylamines.[6]

References
  1. Ebel, K., Koehler, H., Gamer, A. O., & Jäckh, R. "Imidazole and Derivatives." In Ullmann’s Encyclopedia of Industrial Chemistry; 2002 Wiley-VCH, doi:10.1002/14356007.a13_661
  2. Crouch, R. David; Howard, Jessica L.; Zile, Jennifer L.; Barker, Kathryn H. (2006). "Microwave-Mediated Synthesis of Lophine: Developing a Mechanism To Explain a Product". J. Chem. Educ. 83 (11): 1658–1660. doi:10.1021/ed083p1658.
  3. Gelens, E.; De Kanter, F. J. J.; Schmitz, R. F.; Sliedregt, L. A. J. M.; Van Steen, B. J.; Kruse, Chris G.; Leurs, R.; Groen, M. B.; Orru, R. V. A. (2006). "Efficient library synthesis of imidazoles using a multicomponent reaction and microwave irradiation". Molecular Diversity. 10: 17–22. doi:10.1007/s11030-006-8695-3.
  4. Debus, Heinrich (1858). "Ueber die Einwirkung des Ammoniaks auf Glyoxal". Justus Liebigs Annalen der Chemie. 107 (2): 199–208. doi:10.1002/jlac.18581070209.
  5. Radzisewski, Br. (1882). "Ueber Glyoxalin und seine Homologe". Berichte der deutschen chemischen Gesellschaft. 15 (2): 2706–2708. doi:10.1002/cber.188201502245.
  6. Damilano, Giacomo; Kalebić, Demian; Binnemans, Koen; Dehaen, Wim (2020). "One-pot synthesis of symmetric imidazolium ionic liquids N,N-disubstituted with long alkyl chains". RSC Adv. 10: 21071–21081. doi:10.1039/D0RA03358H. PMC 9054310.
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