One-step synthesis of alkyl 2-chloropyrimido[1,2-a]benzimidazole-3-carboxylates under catalyst-free: combined experimental and computational studies
2015
Liu, Yang | Xia, Guoming | Luo, Chao | Sun, Jianqi | Ye, Benfei | Yuan, Yanli | Wang, Hongming
An efficient method for the preparation of pyrimido[1,2-a]benzimidazole derivatives utilizing squaric acid dichloride has been developed at room temperature without catalyst. This method provided a rapid synthesis of pyrimido[1,2-a]benzimidazole system. The result indicates that those expeditious reactions could be carried out only in the presence of alcohols, affording the corresponding alkyl 2-chloropyrimido[1,2-a]benzimidazole-3-carboxylates. Furthermore, the yield of products seems to be closely relevant to the steric hindrance of the added alcohols. On the basis of experimental and theoretical analyses, a plausible mechanism has been proposed and corroborated through DFT calculations for exploring a practical way to efficiently synthesize those highly versatile substituted homologs.
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