Debus–Radziszewski imidazole synthesis

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.

This reaction is named after Heinrich Debus and Bronisław Leonard Radziszewski.

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

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