To a mixture of sodium hydrogen carbonate (2.0 mmol) and PdCl2dppf:CH2Cl2 1:1 (0.03 mmol) under argon, was added a degassed solution 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 (mixture of isomers 2:1, 0.65 mmol) in 10.5 mL dimethoxyethane and 3 mL of water. Trimethylboroxin (50% solution in THF, 1.3 mmol) was then added and the mixture was stirred at 90° C. for 3 h. After cooling to room temperature, water and ethyl acetate were 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 dissolved in 3 mL of trifluoroacetic acid and stirred at 65° C. for 2 h. Water and ethyl acetate were added. And the aqueous layer was extracted with ethyl acetate. The combined organic extracts were washed with a saturated solution of sodium hydrogen carbonate, dried over MgSO4, filtered and concentrated. The residue was purified by chromatography on silica gel (dichloromethane/methanol 20:1 to 10:1) to afford 57 mg of 4-[5-(5-chloro-2-thienyl)-3-methyl-1H-pyrazol-4-yl]pyridine (30% yield).
