In a round-bottomed flask equipped with an effective condenser and a magnetic stirrer, γ-butyrolactone (R3, molecular weight: 86.06; 1 eq.; density = 1.12 g/mL), trimethyl orthoformate (F4, molecular weight: 106.12; 1.9 eq.; density = 0.97 g/mL), and concentrated sulfuric acid (1 mL/10 mL of γ-butyrolactone R3) were mixed in methanol (4 mL/g γ-butyrolactone). lactone R3) were mixed. The mixture was heated at 60 °C for 26 h with stirring. The progress of the reaction was monitored by thin layer chromatography (TLC, unfolding reagent: ethyl acetate/hexane = 1:1) using Pancaldi's solution (prepared from 25 g ammonium molybdate and 5 g cerium sulphate dissolved in 450 mL of water and 50 mL of concentrated sulphuric acid) as a color developer. After completion of the reaction, the solvent was removed by evaporation under reduced pressure. The residue was dissolved in ethyl acetate and washed with saturated sodium bicarbonate solution to pH=8. The crude product was a light yellow oil, which was purified by distillation under reduced pressure (boiling point: 163-164 °C, pressure: 760 Torr) to give the target product, methyl 4-methoxybutyrate (P, molecular weight: 132.16) as a colorless oil in 80% yield.
