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 benzyl bromide (0.71 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 390 mg of the desired methyl mandelate benzyl carbonate (65%): IR (thin film) 3004, 2956, 2839, 1748, 1613, 1516, 1455, 1383, 1246, 1175, 1115, 1027, 953, 824,789 cm−1; 1H NMR (360 MHz, CDCl3) d 3.72 (s, 3 H), 5.20 (s, 2 H), 5.86 (s, 1 H), 7.3˜7.5 (m, 10 H); 13C NMR (90 MHz, CDCl3) d 52.65, 71.17, 127.53, 128.31, 128.51, 128.56, 128.73, 129.38, 133.07, 134.69, 154.31, 168.91.

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)