2-Bromopropane → 4-Bromo-1-isopropyl-1H-pyrazole

To a solution of 4-bromo-1H-pyrazole (5 g, 34 mmol) in DMF (70 ml) were added K2CO3 (11.83 g, 85.6 mmol, 2.5 eq.) and 2-bromopropane (6.3 g, 51.36 mmol, 1.5 eq.) and the mixture was stirred at RT for 12 h. The mixture was quenched and extracted as in Intermediate Example 5(a). The solvent was distilled off and the crude residue was purified by column chromatography (60-120 silica gel, 20% ethyl acetate in hexane) to afford the product in 89% yield (5.8 g). 1H NMR (300 MHz, DMSO-d6): δ 8.01 (s, 1H), 7.50 (s, 1H), 4.49-4.43 (m, 1H), 1.38 (d, 6H).