Sulfuric Acid → Ethyl 3-Bromo-1-(3-chloro-2-pyridinyl)-1H-pyrazole-5-carboxylate

Participants

Reaction Steps

To a 500 mL flask, ethyl 3-bromo-1-(3-chloro-2-pyridinyl)-4,5-dihydro-1H-pyrazole-5-carboxylate (22.22 g, 90%, 60 mmol), potassium persulfate (25.92 g, 96 mmol) and acetonitrile (180 mL) were added. The reaction mixture was stirred at room temperature. The concentrated sulfuric acid (12 g) was added dropwise. After added completely, the reaction mixture was heated to reflux for 2 hours. The mixture was concentrated by rotary evaporator to remove most acetonitrile. Water (100 mL) was added and then the mixture was extracted with ethyl acetate (3×150 mL). The combined organic layers were washed with saturated sodium bicarbonate solution (100 mL) and saturated brine (100 mL), dried over anhydrous magnesium sulfate and concentrated by rotary evaporator to give the product (21.50 g) as a yellow solid in 90% yield. HPLC area normalization method content is 83%.

Provenance & Evidence