反应详情

A solution of 5-methyl-2-tetrahydrofuroic acid (1.80 g, 13.85 mmol) in dichloromethane (25 ml) was treated with oxalyl chloride (2.4 ml, 27.51 mmol) in the presence of dimethylformamide (3 drops). After stirring for 1.25 h, the solvent was evaporated in vacuo. The residue was redissolved in dichloromethane and concentrated again. Excess diazomethane was then bubbled through a solution of the resulting acid chloride in dichloromethane (30 ml) at 0° C. When the addition was complete, the mixture was stirred for 10 min. at 0° C. and then treated with 48% aqueous hydrogen bromide (2.6 ml, 15.41 mmol). The mixture was stirred for 15 min. at room temperature, washed with water (×2), dried and concentrated in vacuo to yield the crude title compound as a brown oil (1.67 g, 58%); νmax (CH2Cl2) 1735, 1387 and 1086 cm-1 ; δH (CDCl3, 90 MHz) 1.33 (3H, d, J 6.0 Hz), 1.48 (1H, m), 1.90-2.35 (3H, m), 4.10 (1H, m), 4.25 (2H, s) and 4.48 (1H, m).

1. customthe solvent was evaporated in vacuo
2. dissolutionThe residue was redissolved in dichloromethane
3. concentrationconcentrated again
4. customExcess diazomethane was then bubbled through a solution of the resulting acid chloride in dichloromethane (30 ml) at 0° C
5. additionWhen the addition
6. stirringthe mixture was stirred for 10 min. at 0° C.
7. stirringThe mixture was stirred for 15 min. at room temperature
8. washwashed with water (×2)
9. customdried
10. concentrationconcentrated in vacuo