Synthesis of Ethers by GaBr3-Catalyzed Reduction of Carboxylic Acid Esters and Lactones by Siloxanes

• Published in: ChemSusChem 2014-02, Vol.7 (2), p.644-649
• Main Authors: Biermann, Ursula, Metzger, Jürgen O.
• Format: Article
• Language: English
• Subjects: Bromides - chemistry; Carboxylic Acids - chemistry; Catalysis; Chemistry Techniques, Synthetic; Esters; ethers; Ethers - chemical synthesis; gallium; Gallium - chemistry; lactones; Lactones - chemistry; Oxidation-Reduction; reduction; renewable resources; Siloxanes - chemistry
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201300627

Ethers were synthesized by reduction of the respective esters catalyzed by gallium bromide (GaBr3) and using siloxanes, preferentially 1,1,3,3‐tetramethyldisiloxane, as reductant. Methyl oleate, triglycerides, that is, tributyrine and glyceryl triundec‐10‐enoate as well as γ‐ and δ‐lactones were converted into the respective ethers in high to moderate yields. γ‐Lactones were reduced with high selectivity in the presence of a methyl ester functionality. The reduction has been carried out at room temperature or moderately elevated temperature of up to 60 °C using stoichiometric amounts of the reductant and 0.005–0.01 equiv of GaBr3 as catalyst per ester functionality without any solvent added. After a reaction time of 1–4 h the conversion of the substrate was 100 %. The product was separated from polymeric siloxanes formed as coupled product by simple distillation. The gift of the GaBr3: Ethers are synthesized by reduction of the respective esters catalyzed by gallium bromide (GaBr3) and using preferentially 1,1,3,3‐tetramethyldisiloxane as reductant. Methyl oleate and triglycerides as well as γ‐ and δ‐lactones are converted into the respective ethers in high to moderate yields. The products can be separated from the polymeric siloxanes formed as coupled product by simple distillation.