γ‐Lactones are an important class of fine chemical products and are widely used in perfumes, medicines, pesticides, dyes, and other fields. Herein, a new method for γ‐lactones preparation based on ring contraction was developed. Starting from macrolides, W(OTf)₆ was used to catalyze the ring‐opening polymerization then depolymerization. The depolymerization step was not a common ring‐closing process, and the carbon number of the ring was reduced one by one by rearrangement to form the most thermodynamically stable five‐membered ring compounds. γ‐Caprolactone (180 °C for 10 h) was obtained in a yield of 94 % when [EMIM]OTf was used as the solvent, and the yield of isolated product was up to 85 %. The interaction of various components and the reaction mechanism were studied by FTIR spectroscopy and ¹H NMR spectroscopy, respectively. Furthermore, γ‐lactones could be produced when the substrate was extended to terminal hydroxyfatty acids. Unexpectedly, the catalyst was poisoned by 1 equivalent of H₂O added during the process and thus the yield decreased greatly. The reaction is green and simple, and proceeds in one pot with high atom economy (100 % for macrolides and with water as the only byproduct for terminal hydroxyfatty acid), which provides a promising approach to synthesizing γ‐lactones.

中文翻译：

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W（OTf）6-催化大环内酯的环收缩或末端羟基脂肪酸在离子液体中的闭环合成γ-内酯

γ-内酯是一类重要的精细化工产品，广泛用于香水，药品，农药，染料和其他领域。本文提出了一种基于环收缩的γ-内酯制备新方法。从大环内酯类化合物开始，使用W（OTf）₆催化开环聚合然后解聚。解聚步骤不是通常的闭环过程，通过重新排列形成最热力学上稳定的五元环化合物，环的碳数被一一减少。当使用[EMIM] OTf作为溶剂时，可得到94％的γ-己内酯（180°C，10小时），分离产物的产率高达85％。用FTIR光谱研究了各种组分的相互作用和反应机理。¹ H NMR光谱分别。此外，当底物延伸至末端羟基脂肪酸时，可能会生成γ-内酯。出乎意料的是，在此过程中，催化剂会因加入1当量的H ₂ O而中毒，因此收率大大降低。该反应是绿色且简单的，并且在一个具有高原子经济性的锅中进行（大环内酯类化合物为100％，水为末端羟基脂肪酸的唯一副产物），这为合成γ-内酯提供了一种有前途的方法。