Example 2: Ethylene oxide (EO, 25.0 g, 1.4 eq.) was slowly added to a methanol (MeOH, 144.0 g) solution of methyl acetoacetate (MAA, 46.9 g, 0.40 mol) followed by triethylamine (TEA, 40.7 g, 1.0 eq.) at 5°C. The reaction mixture was warmed up to 60 °C within 0.5 h and maintained at this temperature for 2.5 h. The reaction mixture was then heated up to 60 °C within 0.5 h and maintained at this temperature for 2.5 h. Quantitative GC analysis showed 50.8% conversion of MAA and 72.9% selectivity of α-acetyl-γ-butyrolactone (ABL).
Example 4: Ethylene oxide (EO, 35.3 g, 2.0 eq.) was slowly added to a methanol (MeOH, 144 g) solution of methyl acetoacetate (MAA, 47.0 g, 0.40 mol) at 5 °C, followed by triethylamine (TEA, 42.4 g, 1.0 eq.). The reaction mixture was warmed up to 60 °C within 0.5 h and maintained at this temperature for 4.5 h. The reaction mixture was then heated up to 60 °C within 0.5 h and maintained at this temperature for 4.5 h. Quantitative GC analysis showed 67.7% conversion of MAA and 75.0% selectivity of α-acetyl-γ-butyrolactone (ABL).
Examples 7-27: The reaction was carried out according to the method of Example 1 by adjusting the amount of ethylene oxide (EO), the optional addition of the catalysts and additives specified in Table 1, and the reaction times specified in Table 1. Table 1 details the reaction conditions, conversion and selectivity data for Examples 7-27. All reactions of Examples 7-26 were carried out at 60°C using 11 equivalents of methanol as solvent and 0.40 equivalents of MAA. Examples 27 and 28, on the other hand, used 0.10 eq. of MAA and 1 eq. of EO at 60 °C, using 11 eq. of methanol as solvent.
Example of Example 28: Example of optimal reaction conditions using triethylamine (TEA) as a catalyst: 37 g of methanol was added to a 250 mL autoclave, pressurized with 2-3 bar nitrogen and heated to 65 °C. Subsequently, a solution of MAA (39.9 g, 0.34 mol, 1 eq.) and triethylamine (TEA, 34.4 g, 0.34 mol, 1 eq.) in methanol (27 g) with ethylene oxide (EO, 30.1 g, 0.68 mol, 2 eq.) was added simultaneously via two pumps over 11 min. After 2 h of reaction, analysis by GC showed a selectivity of 77% for ABL and a yield of 52.3% based on the added MAA. The conditions for this series of reactions ranged from 65 to 95 °C, addition times from 9 to 13 min, concentrations of MAA in the solvent from 1.3 to 2.1 mol/L, TEA/MAA molar ratios from 0.7 to 1.3, and EO/MAA molar ratios from 1.7 to 2.2.The results of this series of reactions showed MAA conversions ranging from 65.6 to 85.0%, ABL selectivities of 47.5-77.4% and the yield of ABL based on MAA was 40.4-52.3%.
