Synthesis
(i) Synthesis of trimethyl citrate
Citric acid (9.00 g, 46.8 mmol) was dissolved in anhydrous methanol and thionyl chloride (20.50 mL, 0.28 mol) was added slowly and dropwise at 0 °C and under nitrogen protection. The reaction mixture was stirred at 0 °C for 1 h, then warmed to room temperature and continued stirring overnight. Upon completion of the reaction, the volatile components were removed by distillation under reduced pressure. The resulting solid residue was recrystallized using a hexane/ethyl acetate solvent mixture to give 10.80 g of white crystalline trimethyl citrate in 98% yield.
1H NMR (acetone-d6, 200 MHz): δ 2.85 (dd, 4H, J1 = 15.4 Hz, J2 = 27.2 Hz); 3.60 (s, 6H); 3.72 (s, 3H); 4.50 (br.s, 1H).
13C NMR (acetone-d6): calculated value: M+ = 234.21.
References
[1] Molecules, 2006, vol. 11, # 4, p. 263 - 271
[2] Patent: WO2007/14471, 2007, A1. Location in patent: Page/Page column 30
[3] Patent: US2013/89611, 2013, A1. Location in patent: Paragraph 0133-0135
[4] Molecules, 2018, vol. 23, # 9,
[5] RSC Advances, 2014, vol. 4, # 100, p. 57297 - 57307
