1-H-pyrazole-4-carboxylic acid,3-broMo,ethyl ester synthesis

Yield:1353100-91-0 100%

Reaction Conditions:

with copper(ll) bromide;isopentyl nitrite in acetonitrile at 50;

Steps:

5.1
To a 0° C. solution of ethyl 3-amino-1H-pyrazole-4-carboxylate (5.0 g, 32 mmol) and copper (II) bromide (7.2 g, 32 mmol) in acetonitrile (65 mL) was slowly added isoamyl nitrite (12 mL, 86 mmol). The reaction was heated to 50° C. and stirred overnight. The reaction was cooled to room temperature and quenched with 1 N aqueous hydrochloric acid (150 mL). The mixture was extracted with ethyl acetate (3×100 mL). The combined organics were washed with water, dried over sodium sulfate, filtered, and concentrated to give the title compound as a brown oil that partially solidified under vacuum overnight (7.1 g, 100%). ¹H NMR (400 MHz, CDCl₃, δ): 9.78 (br. s., 1H), 8.10 (br. s., 1H), 4.33 (q, J=7.22 Hz, 2H), 1.36 (m, 3H).

References:

Pfizer Inc US2012/108619, 2012, A1 Location in patent:Page/Page column 26

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