反应详情

The reaction was carried out, under nitrogen, in a 2 L×4 neck flask equipped with a mechanical stirrer, water condenser (with gas inlet), and a thermocouple. The reactor was charged with 5-methylpyrazinecarboxylic acid (300.84 g), an acidic cation exchange resin (60.17 g), and ethanol (1004 g). The mixture was stirred at reflux for about 16 h after which the reaction was found to be complete by GC or GC/MS. The resin was removed by pressure filtration and rinsed with ethanol. The rinse was added to the alcohol solution of the ester. Evaporation of the solvent under reduced pressure gave 336.7 g (93%) of 5-methylpyrazinecarboxylic acid, ethyl ester that was suitable for use in the following examples. It was also possible to pass the material through a thin film evaporator at 125° C./3 mm. The material from this distillation was almost colorless and crystallizes at about 20° C.

1. customequipped with a mechanical stirrer, water condenser (with gas inlet)
2. temperatureat reflux for about 16 h after which the reaction
3. customThe resin was removed by pressure filtration
4. washrinsed with ethanol
5. additionThe rinse was added to the alcohol solution of the ester
6. customEvaporation of the solvent under reduced pressure