反应详情

温度

160 °C

With stirring, a mixture of 0.643 g of methyl 3-(4-methoxypyridin-2-yl)propionate (starting material A2), 0.359 g of 2,3-diaminopyridine and 10 g of polyphosphoric acid (PPA) is heated at 160° C. for 1 h. After cooling, the mixture is poured into about 50 ml of ice-water and then neutralized (pH 7–8) using 6N aqueous sodium hydroxide solution. The mixture is extracted three times with dichloromethane/methanol 9:1, the combined organic phases are evaporated to dryness and the residue is chromatographed on a silica gel column (dichloromethane/methanol 15:1). Concentration of the chromatographically pure fractions gives 0.36 g of an oil, which crystallizes on standing. The product is recrystallized from ethyl acetate/petroleum ether, giving 0.278 g of the title compound as a light-beige powder of m.p. 116–117° C.; the mass spectrum shows the molecular peaks MH+ and 2MNa+ at 255.3 and 530.9 Da.

1. temperatureAfter cooling
2. extractionThe mixture is extracted three times with dichloromethane/methanol 9:1
3. customthe combined organic phases are evaporated to dryness
4. customthe residue is chromatographed on a silica gel column (dichloromethane/methanol 15:1)