Trimethylaluminium (2M in toluene, 1.51 mL, 3.02 mmol) was added dropwise to 5-[2-(3,5-dimethoxyphenyl)ethyl]-2H-pyrazol-3-amine (299 mg, 1.21 mmol) and methyl 4-(4-ethylpiperazin-1-yl)benzoate (300 mg, 1.21 mmol) in toluene (6.0 mL) at 25° C. The resulting suspension was stirred at 60° C. for 24 h under nitrogen. The reaction mixture was added to methanol (100 mL) and was treated with HCl (2N aqueous solution, until the pH was 7 or lower). The crude product was purified by ion exchange chromatography, using a SCX column. The desired product was eluted from the column using 7M NH3/MeOH and fractions were evaporated to dryness to afford impure product. The crude product was purified by silica column chromatography, eluting with a gradient of 0 to 5% 7M NH3/MeOH in DCM. Pure fractions were evaporated to dryness to afford the title compound (288 mg, 51%) as a cream solid.
