反应详情

Dimethyl sulfoxide (3.54 mL, 49.8 mmol) was added dropwise over 10 min to a vigorously stirred mixture of a 2 M dichloromethane solution of oxalyl chloride (12.46 mL, 24.91 mmol) and dichloromethane (40 mL) at −78° C. After another 15 min at −78° C., a solution of benzyl trans-4-hydroxytetrahydrofuran-3-ylcarbamate (3.94 g, 16.61 mmol, from Step 2) in dichloromethane (20 mL) was added dropwise over 15 min. After 30 min at −78° C., the mixture was diluted with dichloromethane (20 mL). Triethylamine (9.26 mL, 66.4 mmol) was added. The mixture became a thick slurry (a large stir bar was necessary for efficient stirring). The mixture was stirred at −78° C. for 30 min, at ambient temperature for 40 min, quenched with water (150 mL) and extracted with dichloromethane (3×100 mL). The combined extracts were dried (MgSO4) and concentrated. Silica gel chromatography, eluting with 20-50% ethyl acetate in hexanes, gave benzyl 4-oxotetrahydrofuran-3-ylcarbamate as tan solid (3.579 g, 92% yield). 1H NMR (400 MHz, chloroform-d) δ ppm 7.28-7.47 (5 H, m), 5.21 (1H, br. s.), 5.01-5.16 (2 H, m), 4.69 (1 H, t, J=8.58 Hz), 4.15-4.31 (2 H, m), 3.92 (1 H, d, J=17.61 Hz), 3.79 (1 H, t, J=9.57 Hz).

1. waitAfter 30 min at −78° C.
2. stirringThe mixture was stirred at −78° C. for 30 min, at ambient temperature for 40 min
3. customquenched with water (150 mL)
4. extractionextracted with dichloromethane (3×100 mL)
5. dry with materialThe combined extracts were dried (MgSO4)
6. concentrationconcentrated
7. washSilica gel chromatography, eluting with 20-50% ethyl acetate in hexanes