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.

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 [de].^[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]