Pyridine → Ethyl 1-cyclopropyl-3-(trifluoromethyl)-1H-pyrazole-4-carboxylate

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Cyclopropyl boronic acid (11 g, 127 mmol), Copper acetate (17.4 g, 95.7 mmol), Pyridine (17.7 g, 223 mmol) and triethylamine (22.4 mL, 160 mmol) were added successively to a solution of ethyl 5-(trifluoromethyl)-1H-pyrazole-4-carboxylate (Preparation 100, 6.63 g, 31.9 mmol) in THF (70 mL) and the resulting mixture was allowed to stir at 60° C. for 36 hours. The reaction mixture was filtered over a celite bed and filtrate was concentrated in vacuo and diluted with EtOAc (200 mL). The organic layer was washed with 1N HCl (1×25 mL), brine (1×25 mL) and dried (Na2SO4) and evaporated in vacuo. The crude material was purified by silica gel column chromatography eluting with Hexane:EtOAc 85:15 to afford the title compound as brown solid (29%, 2.3 g).

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