A novel and efficient synthesis of imidazo[1,5-a]Pyridines

Richard J. Mason Jr., Clark Atlanta University

Abstract

A one-pot and straightforward synthesis, which results in the formation of imidazo[l,5-a]pyridines, has been intensely investigated. This methodology has been applied to 2,2'-pyridil, a- pyridoin and 2-benzoylpyridne ketone systems respectively.Treatment of 2,2'-pyridiI, a -pyridoin or 2-benzoylpyridine with aromatic aldehydes, and ammonium acetate in the presence of hot acetic acid has been shown to give l-(2-Pyridoyl)-3-phenylimidazolesand l,3-di-phenylimidazo[l,5-a]pyridines in good to excellent yields. These reactions were carried out without the use of metal catalysts, which is a commonly used methodology for imidazo[l,5-a]pyridine synthesis.

A new and efficient synthesis of l,3-diaryl-[l,5-a]imidazopyridines has also been developed based on the reaction of 2-benzoylpyiridne with aldehydes in the presence of ammonium acetate and hot acetic acid Aldehydes applicable to this reaction include aryl aldehydes, heteroaromatic aldehydes, salicylaldehydes.