Potassium Carbonate → [3,5-dimethyl-1-(2-chloro-4-nitrobenzyl)-1H-pyrazol-4-yl]acetic acid ethyl ester

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Reaction Steps

To a solution of (3,5-dimethyl-1H-pyrazol-4-yl)acetic acid ethyl ester (1.40 g, 7.7 mmol) and 2-chloro-4-nitrobenzyl bromide (4.60 g, 20.7 mmol) in 20 mL acetonitrile is added K2CO3 (1.59 g, 11.5 mmol) and the mixture is stirred for 48 hours at room temperature. 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 to yield 2.79 g of [3,5-dimethyl-1-(2-chloro-4-nitro-benzyl)-1H-pyrazol-4-yl]-acetic acid ethyl ester (ESI mass spectrum: [M+H]+=352; Retention time: 1.95 min (method A). b) To a solution [3,5-dimethyl-1-(2-chloro-4-nitrobenzyl)-1H-pyrazol-4-yl]acetic acid ethyl ester (2.39 g, 6.8 mmol) in methanol (40 mL) is added Raney nickel (250 mg) and the mixture is hydrogenated. The catalyst is filtered off and the filtrate is concentrated under reduced pressure to yield 1.18 g of the title compound (ESI mass spectrum: [M+H]+=322; Retention time HPLC: 1.76 min (method A)).

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