To a solution of (3,5-dimethyl-1H-pyrazol-4-yl)-acetic acid methyl ester (10 g, 48.9 mmol) and 2-fluoro-4-nitrobenzyl bromide (11.5 g, 49.1 mmol) in acetonitrile (150 mL) is added K2CO3 (10.1 g, 73.3 mmol) and the mixture is stirred for 48 hours at 60° C. The solvent is removed by evaporation and the residue is dissolved in dichloromethane/water. After extraction with dichloromethane the organic layer is dried over Na2SO4 and evaporated under reduced pressure. The residue is purified by MPLC (cyclohexane/diethyl ether 7:3) to yield 13 g of [3,5-dimethyl-1-(2-fluoro-4-nitrobenzyl)-1H-pyrazol-4-yl]acetic acid methyl ester (ESI mass spectrum: [M+H]+=322; Retention time (HPLC): 0.85 min (method C)). b) To a solution of [3,5-dimethyl-1-(2-fluoro-4-nitro-benzyl)-1H-pyrazol-4-yl]acetic acid methyl ester (13 g, 40.4 mmol) in methanol (250 mL) is added Raney nickel (6 g) and the mixture is hydrogenated at 50 psi and 50° C. The catalyst is filtered off and the filtrate is concentrated under reduced pressure. The mixture is purified by crystallization in diisopropyl ether to yield 12.8 g of the title compound (ESI mass spectrum: [M+H]+=292; Retention time HPLC: 0.61 min (method C)).
