反应详情

温度

175 °C

A 1-L, 4-neck, round-bottom flask, fitted with a thermometer, mechanical stirrer, nitrogen inlet tube and Liebig condenser/receiving flask, was charged with 258.3 g (3.00 mol, 1.00 equiv) of cyclopropanecarboxylic acid, 366.5 g (3.00 mol, 1.00 equiv) of 2-phenylethanol, and 1.14 g (0.2 wt. %) of tin oxalate (Fascat® 2001). The air was removed with three cycles of evacuation/nitrogen-fill using a mechanical vacuum pump (50-100 torr). The rate of stirring was set at ca. 200 rpm, the nitrogen sparge was set at 0.05 scfh, and the reaction mixture was heated to 175° C. After a 2-h hold, 78.0 g of distillate had been collected. The temperature was increased to 180° C. and held for 1 h; an additional 9.6 g of distillate was collected. Finally, the temperature was increased to 190° C. and held for 2 h, and an additional 8.6 g of distillate was collected. The acid number was 5.30 mg KOH/g (98.3% conversion). The excess 2-phenylethanol (12.4% by GLC) and cyclopropanecarboxylic acid (0.82% by GLC) were removed by vacuum distillation through a 15-cm Vigreux column at 95-135° C. (10 torr) in a 101-g forecut. The crude product was distilled at 136-139° C. (10 torr) through a 15-cm Vigreux column to afford 410 g (72%) of 2-phenylethyl cyclopropanecarboxylate (99.1% pure by GLC): residual alcohol, 0.6% (GLC); APHA color, 4.0; acid number, 0.14 mg KOH/g; saponification number, 291 mg KOH/g (theor. 295 mg KOH/g). The cyclopropanecarboxylic acid distilled out of the reaction mixture with the water of reaction can be recycled to improve the yield.

1. customThe air was removed with three cycles of evacuation/nitrogen-fill
2. customthe nitrogen sparge
3. distillationAfter a 2-h hold, 78.0 g of distillate had been collected
4. temperatureThe temperature was increased to 180° C.
5. distillationan additional 9.6 g of distillate was collected
6. temperatureFinally, the temperature was increased to 190° C.
7. waitheld for 2 h
8. distillationan additional 8.6 g of distillate was collected
9. customThe excess 2-phenylethanol (12.4% by GLC) and cyclopropanecarboxylic acid (0.82% by GLC) were removed by vacuum distillation through a 15-cm Vigreux column at 95-135° C. (10 torr) in a 101-g forecut
10. distillationThe crude product was distilled at 136-139° C. (10 torr) through a 15-cm Vigreux column