Tetrahydrofuran → 5-(2-Bromoacetyl)pyrazole-3-carboxylic acid ethyl ester

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Reaction Steps

A 100ml flask was charged with 27.8 g of 5-acetylpyrazole-3-carboxylic acid ethyl ester and 40 ml of tetrahydrofuran. To this mixture, 56.4 g of phenyltrimethylammonium tribromide were added. The resulting red mixture was stirred at room temperature for 1 hour and poured into 600 ml of water. The resulting mixture was filtered and the solids were washed with more water. The solids were collected, air-dried and recrystallized from 1:1 mixture of disopropyl ether and hexanes (300ml) to afford 33.1 g of 5-(2-bromoacetyl)pyrazole-3-carboxylic acid ethyl ester as white solids, mp 174°-176° C. NMR: 1.42 (t, 3H), 4.44 (q, 2H), 4.57 (s, 2H), 7.4 (s, 1H).

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