Base-Mediated Four-Component Intramolecular Cyclization Reaction: One-Pot Access to Imidazole-4-(2H)-Ones

A base-mediated one-pot, two-step, four-component reaction has been developed to synthesize imidazole-4(2H)-ones, utilizing commercially available amino acid esters, aldehydes, alkynes, and amino alcohols. Control experiments and isolation of the intermediate revealed the mechanistic details. This four-component reaction proceeds via imine formation, followed by the nucleophilic addition of alkyne to form a propargylamine precursor. Subsequently, the propargylamine precursor under undergoes base-mediated conversion into 1-azadiene, followed by in situ ketene formation to generate (allylideneamino)prop-1-en-1-one. The nucleophilic addition of amino alcohol and subsequent intramolecular cyclization provides imidazole-4 (2H)-ones exclusively.