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 undergoes base‐mediated conversion into 1‐azadiene, followed by in situ ketene formation to generate (allyl‐dene‐amino)prop‐1‐en‐1‐one. The nucleophilic addition of amino alcohol and subsequent intramolecular cyclization provides imidazole‐4 (2H)‐ones exclusively.