反应详情

Methyl (S)-(+)-mandelate (332 mg, 2 mmol) is dissolved in anhydrous N,N-dimethylforamide (8 mL), and powdered cesium carbonate (1.95 g, 6 mmol, 3 eq) is added. The suspension is then stirred at room temperature while passing carbon dioxide gas for 1 hour before 4-methoxybenzyl chloride (0.81 mL, 6 mmol, 3 eq) is added to the solution. Carbon dioxide gas is continuously bubbled through the solution for another 2˜3 hours until the starting material is consumed. The reaction is quenched with water (20 mL) and extracted with EtOAc (3×20 mL). The resulting organic layer is washed consecutively with water (3×20 mL), brine (20 mL), and dried over anhydrous sodium sulfate. Filtration and concentration in vacuo provides an oil, which is purified by column chromatography (9:1 Hexanes-EtOAc) to yield 607 mg of the desired methyl mandelate benzyl carbonate (92%): IR (thin film) 3036, 2957, 2838, 1748, 1614, 1517, 1456, 1383, 1246, 1175, 1028, 928, 824 cm−1; 1H NMR (360 MHz, CDCl3) d 3.73 (s, 3H), 3.79 (s, 3H), 5.16 (s, 2 H), 5.88 (s, 1H), 6.88-7.48 (m, 9 H); 13C NMR (90 MHz, CDCl3) d 52.57, 55.11, 70.04, 113.81, 127.47, 128.67, 129.30, 130.26, 133.10, 154.27, 159.83, 168.90. EM Anal. Calcd. C18H18O6: C, 65.45; H, 5.49. Found: C, 65.51; H, 5.55.

1. customfor 1 hour
2. additionis added to the solution
3. customCarbon dioxide gas is continuously bubbled through the solution for another 2˜3 hours until the starting material
4. customis consumed
5. customThe reaction is quenched with water (20 mL)
6. extractionextracted with EtOAc (3×20 mL)
7. washThe resulting organic layer is washed consecutively with water (3×20 mL), brine (20 mL)
8. dry with materialdried over anhydrous sodium sulfate
9. filtrationFiltration and concentration in vacuo
10. customprovides an oil, which
11. customis purified by column chromatography (9:1 Hexanes-EtOAc)