Phosphorus tribromide → Ethyl 5-bromo-4-(bromomethyl)-1-phenyl-1H-pyrazole-3-carboxylate

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Reaction Steps

To a solution of ethyl-5-bromo-4-(hydroxymethyl)-1-phenyl-1H-pyrazole-3-carboxylate (2.91 g, 8.98 mmol, 1 eq) in Et2O cooled at −10° C. is added phosphorus tribromide (1.02 mL, 10.77 mmol, 1.2 eq) and the reaction mixture is stirred at Rt for 1 h. The reaction mixture is poured over ice and extracted with MTBE. The organic layer is washed with brine, dried over Na2SO4 and concentrated to afford 2.1 g (60%) of the title compound. 1H NMR (DMSO-d6, 400 MHz): δ 7.65-7.57 (m, 5H), 4.77 (s, 2H), 4.35 (q, J=6.0 Hz, 2H), 1.32 (t, J=6.6 Hz, 3H). HPLC (max plot) 83.30%; Rt 5.33 min.

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