The Debus-Radziszewski imidazole synthesis is an organic reaction used for the synthesis of imidazoles from a dicarbonyl, an aldehyde, and ammonia. The dicarbonyl component is commonly glyoxal, but can also include various 1,2-diketones and ketoaldehydes. The method is used commercially to produce several imidazoles. 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 ammonia condense to give an diimine (shown with unusual orientation of N-H groups):
In the second stage, this diimine condenses with the aldehyde:
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.