Synthesis Of Imidazole Derivatives

The synthesis of 2-phenylimidazoline from benzaldehyde and ethylenediamine has been studied in this paper. The effect of the different oxidation systems, synthesis method, reaction temperature, solvent, the kinds and the mount of water absorbent were systematically studied. The results showed that sodium iodide could be recycled as a catalyst in this green hydrogen peroxide oxidation system. The yield of 2-phenylimidazoline is 93.7 % when the ratio of ethylenediamine/ benzaldehyde/ sodium iodide is 1.1: 1.0: 0.4 and the amount of anhydrous magnesium sulfate is 0.5 g. Moreover, a series of substituted aldehydes were examined with ethylenediamine in the presence of hydrogen peroxide/sodium iodide/anhydrous magnesium sulfate under the same conditions to provide the corresponding 2-imidazolines and the structures of the 2-imidazolines were confirmed by IR, NMR, and HRMS. The effect of electronic and steric factor was also discussed in the reaction. The o-substituted aldehydes gave rather lower yields than the m- and p-substituted aldehydes, suggesting that the steric effects seem to be prominent factor in this reaction. Then, a preliminary research for the synthesis of 2-imidazole from the oxidation of 2-imidazoline was also studied.Furthermore, the synthesis of 2-imidazolidone using ethylenediamine and urea as the raw material was studied in this paper. The effect of solvents on the reaction was investigated in detail. Firstly, the effect of ethylene glycol and water as solvent was examined. The recycle of the solvent was also studied. The yield was 59.1 % when using ethylene glycol as solvent solely, and the yield increased greatly up to 90 % when recycling the solvent. But the depuration was difficult and expensive. Furthermore, when using water as solvent, the course of reaction was violent. Finally the mixture of ethylene glycol and water was used as co-solvents investigated with different volume ratio. Excitingly, when the mixture of ethylene glycol and water was used as co-solvents with the volume ratio of 0.5:1, the optimal yield of 2-imidazolidone was 82.7 %.