Enantioenriched γ-butenolides are valuable structural cores in many pharmaceuticals and natural products, but their direct and catalytically asymmetric assembly remains rare. Here, we report an efficient, atom-economic synthetic strategy for enantioenriched γ-butenolides via a unique enantioselective reaction of cyclopropene carboxylic acids with imines under the synergistic catalysis of Rh2(esp)2/chiral Br?nsted acid system. The reaction involved trapping of carboxylic oxonium ylides, generated from cyclopropene carboxylic acids, which presented as the first asymmetric trapping reactive intermediate in the process. Subsequently, enantioenriched γ-butenolide derivatives were obtained in good-to-high yields (55–94%) with excellent stereoselectivities (up to >95∶5 dr and up to 98∶2 er) under mild conditions.

中文翻译：

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含亚胺的胺类羧酸对映体的高对映选择性捕集，可直接组装对映体富集的γ-丁烯内酯

富含对映体的γ-丁烯内酯是许多药物和天然产品中有价值的结构核心，但它们的直接和催化不对称组装仍然很少见。在这里，我们报道了在Rh2（esp）2 /手性布朗斯台德酸体系的协同催化下，环丙烯羧酸与亚胺的独特对映选择性反应，对映体富集的γ-丁烯内酯的有效，原子经济合成策略。该反应涉及捕集由环丙烯羧酸生成的羧酸氧鎓叶立德，其是该方法中的第一个不对称捕集反应性中间体。随后，在温和条件下，以良好到高的收率（55-94％）获得了对映体富集的γ-丁烯内酯衍生物，具有极好的立体选择性（高达> 95∶5 dr和高达98∶2 er）。