Hydrochloric Acid → Ethyl 3-(4-fluoro-2-nitroanilino)-1-methylpyrazole-4-carboxylate

Participants

Reaction Conditions

Reaction Steps

A solution of ethyl 3-amino-1-methylpyrazole-4-carboxylate (Helv. Chim. Acta (1959) 42 349) (17 g) in dry tetrahydrofuran (250 ml) was stirred under nitrogen at -10° C. n-Butyl lithium (75 ml of 1.84 molar solution in hexane) was added at -10° to -15° C. The mixture was stirred at -15° C. for 10 minutes and a solution of 2,5-difluoronitrobenzene (16 g) in dry tetrahydrofuran (50 ml) was added at -15° to -10° C. The solution was warmed at room temperature and stirred for 1 hour. The ink-blue solution was poured into 500 ml of a 1:1 mixture of hydrochloric acid (2 M) and ice-brine, extracted with chloroform (3×250 ml), washed with water (2×250 ml), dried with magnesium sulphate and evaporated to dryness. The brick-red residue was crystallised from ethanol (800 ml) to give the title compound having a m.p. of 162° C.

Provenance & Evidence