O-Tosyl Amidoximes及1,2,4-Oxadiazolones與3-Dimethylaminopropenones進行[3+2]環化反應研究

Abstract

本研究首先探討O-tosyl amidoxime與3-dimethylaminopropenone在路易士酸FeCl3的催化下，進行[3+2]環加成反應得到4-acyl-2-substituted imidazole。但是 O-tosyl amidoxime具有只能合成烷基和拉電子性芳香環的限制，因而改為合成1,2,4-oxadiazol-5-one，與3-dimethylaminopropenone進行[3+2]環加成反應得到C2位為推電子性芳香環的4-acyl-2-substituted imidazole。 綜合兩種以O-tosyl amidoxime和1,2,4-oxadiazol-5-one合成的方法，與3-dimethylaminopropenone進行[3+2]環加成反應，成功合成各種不同官能基取代的4-acyl-2-alkyl/arylimidazole衍生物。A [3+2] cycloaddition reaction of O-tosyl amidoxime and 3-dimethylamino-1-propenone derivatives under the catalysis of FeCl3 as Lewis acid to afford 4-acyl-2-alkylimidazoles has been studied. But O-tosyl amidoximes were limited to only alkyl and electron-withdrawing aryl substituents. Therefore, we developed another [3+2] cycloaddition reaction which used 1,2,4-oxadiazol-5-one derivatives as starting materials to react with 3-dimethylaminopropenone to obtain 4-acyl-2-substituted imidazoles with C2 electron-withdrawing aryl group. Combine with the reactions of either O-tosyl amidoxime or 1,2,4-oxadiazol-5-one as the starting material, the [3+2] cycloaddition reaction with 3-dimethylamino-1-propenone can afford the corresponding 4-acyl-2-substituted imidazoles in good yields. We have succeeded to synthesize a variety of 4-acyl-2-alkyl/arylimidazole derivatives with different functional groups by this methodology.