Phosphorus oxychloride → Ethyl 4-chloropyrazolo[1,5-A]quinoxaline-3-carboxylate

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Reaction Steps

50 g. of the product of Example 1, part b in 200 ml. of phosphorus oxychloride are refluxed for 3 hours. After distilling off the excess phosphorus oxychloride, 4-chloropyrazolo[1,5-a]quinoxaline-3-carboxylic acid, ethyl ester crystallizes. The distillation residue is stirred shortly with ice water and then the crude product is filtered off. The crude product is dried briefly over potassium hydroxide and recrystallized from acetone. The pure product is obtained as white needles; yield 39.5 g., m.p. 105°-106°.

Provenance & Evidence