Europium(III)triflate has been proved to be an effective catalyst for intramolecular cyclization of aryl-substituted carboxylic acid to afford arylated γ-butyrolactone. Various attractive features, such as broad substrate scope, a wide range of functional group tolerance, operational simplicity, complete atom economy, and good-to-excellent yields have made this new protocol more appealing. Moreover, this method provides a practical alternative to the existing catalysts.

中文翻译：

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铕催化的羧酸与未活化烯烃的分子内加成：制备芳基取代的 γ-丁内酯的有效途径

三氟甲磺酸铕 (III) 已被证明是芳基取代羧酸分子内环化生成芳基化 γ-丁内酯的有效催化剂。各种吸引人的特点，如广泛的底物范围、广泛的官能团耐受性、操作简单、完整的原子经济性和良好的产量，使这个新协议更具吸引力。此外，该方法为现有催化剂提供了实用的替代方案。