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W(OTf) 6 ‐Catalyzed Synthesis of γ‐Lactones by Ring Contraction of Macrolides or Ring Closing of Terminal Hydroxyfatty Acids in Ionic Liquid
Author(s) -
Xie ZhongYu,
Deng Jin,
Fu Yao
Publication year - 2018
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201800587
Subject(s) - chemistry , depolymerization , catalysis , yield (engineering) , ionic liquid , ring (chemistry) , nuclear magnetic resonance spectroscopy , solvent , stereochemistry , organic chemistry , materials science , metallurgy
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 1 H 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 H 2 O 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.