To a solution of 4-[5-bromo-3-(5-chloro-2-thienyl)-1H-pyrazol-4-yl]pyridine (14.7 mmol) in 80 mL of N,N-dimethylformamide was added slowly at 0° C. sodium hydride (16.1 mmol). The mixture was stirred 30 min at room temperature prior to dropwise addition of 4-methoxybenzyl chloride (16.1 mmol). The mixture was then stirred for further 5 hours. The mixture was then poured on water and ethyl acetate was added. The aqueous layer was extracted with ethyl acetate and the combined organic extracts were washed with brine, dried over MgSO4, filtered and concentrated. The residue was purified by chromatography on silica gel (heptane/ethyl acetate 4:1 to 1:1) to afford 5.7 g of 4-[5-bromo-3-(5-chloro-2-thienyl)-1-(4-methoxybenzyl)-1H-pyrazol-4-yl]pyridine and 4-[3-bromo-5-(5-chloro-2-thienyl)-1-(4-methoxybenzyl)-1H-pyrazol-4-yl]pyridine (80% yield) as a mixture 2:1 which was used as such in the following step.
