In a 1000 mL three-necked flask, 300 g of tetrahydrofuran and 26 g of sodium hydride were added. While stirring and cooling to 0–5 °C, 120 g of natural ethyl lactate was added dropwise. After reacting for 30 minutes, the reaction solution was heated to 60 °C, and 74 g of natural crotonitrile was added dropwise. After the addition was completed over two hours, the mixture was refluxed to obtain nitrile furanone with a yield of 96%. The nitrile furanone was then oxidized with potassium persulfate, and refluxed with water as the solvent. The mixture was then subjected to pyrolysis of the nitrile using a strong-base anion exchange resin, Dowex 2, to obtain furanone with a yield of 28%.
Take 60 g of the natural equivalent furanone obtained by the above method, 480 g of natural methanol, and 3 g of p-toluenesulfonic acid, add them to a 1000 mL three-necked flask, and reflux for 8 hours. Cool the reaction solution to room temperature, add 90 g of sodium bicarbonate, stir for 30 minutes, and then filter off the sodium bicarbonate. Distill methanol under normal pressure until no more distillate is obtained, then distill 4-Methoxy-2,5-dimethyl-3(2H)-furanone under reduced pressure, yielding a purity of 97% and a molar yield of 65%.
