Phosphorus oxychloride → Ethyl 4-chloro-1-ethyl-6-methyl-1H-pyrazolo[3,4-b]pyridine-5-carboxylate

Participants

Reaction Steps

A mixture of 49.1 g of 1-ethyl-6-methyl-4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (0.197 mole) and 250 ml of phosphorus oxychloride is refluxed for 4 hours. Then the excess phosphorus oxychloride is removed by vacuum distillation and the residue is treated with water. The 4-chloro compound (42 g) is filtered under suction and recrystallized from n-hexane, mp 54°-56° C.

Provenance & Evidence