2-Methylimidazole can be viewed as a tridentate nucleophile that can give three consecutive tandem nucleophilic attacks on electrophiles. A highly functionalized imidazo pyranone ring system (1) was obtained as the major product when 2-methylimidazole was reacted with excess 1,3-dimethyl diacid chloride in presence of a base under mild conditions. Imidazo pyridine dione was the other product. The imidazo pyranone ring system has a 10-membered ring fused to both an imidazole ring and a six-membered ester ring.  It has a diene unit cross conjugated with the imidazole ring. Compounds with a similar core structure were previously reported to have anticholinergic properties. Further, reactions of other substituted imidazoles were also explored. Another type of imidazo pyranone was obtained when 2-methylimidazole and cyclobutane-1,1-dicarbonyl dichloride were reacted under similar conditions. These reactions are proposed to proceed through a cyclic ketene acetal intermediate.                                           

Synthesis of substituted imidazo pyranones using in situ generated cyclic ketene N,N'-acetals

243rd National Meeting (2012)

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