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[摘要]：An unprecedented version of the Ugi three-component coupling reaction is reported in which isocyanides react with unprotected aldoses as biorenewable aldehyde components and acyclic amidines as amine components. The reaction proceeds through [4 + 1] cycloaddition of a conjugated imine intermediate with the isocyanide followed by dehydrative ring transformation of the resulting 4-amino-5-(polyhydroxyalkyl)imidazole to afford imino sugar-annulated imidazoles in excellent yields (86-95%). The procedure is performed in one pot in the presence of a nanoclay (K-10) catalyst, and can be expeditiously effected under solvent-free microwave-irradiation conditions. |
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