反应详情

A mixture of 23.5 g. of 1-ethyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (0.1 mol.) and 150 ml. of phosphorus oxychloride is refluxed for 4 hours. Subsequently, the excess phosphorus oxychloride is removed by means of vacuum distillation. As soon as the phosphorus oxychloride has been removed, the oily residue solidifies on cooling. It is treated with water and filtered under suction (24.5 g.), m.p. 55°-60°. The 4-chloro-1-ethyl-1H-pyrazolo[3,4-b]-pyridine-5-carboxylic acid ethyl ester is recrystallized from N-hexane (22.5 g. = 87%), m.p. 62°.

1. additionA mixture of 23.5 g
2. customSubsequently, the excess phosphorus oxychloride is removed by means of vacuum distillation
3. customAs soon as the phosphorus oxychloride has been removed
4. temperatureon cooling
5. additionIt is treated with water
6. filtrationfiltered under suction (24.5 g.), m.p. 55°-60°
7. customThe 4-chloro-1-ethyl-1H-pyrazolo[3,4-b]-pyridine-5-carboxylic acid ethyl ester is recrystallized from N-hexane (22.5 g. = 87%), m.p. 62°