Triethylamine → 5-Amino-1-(5-carboxy-2-methyl-phenyl)-3-methyl-1H-pyrazole-4-carboxylic acid ethyl ester

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To a stirred solution of 3-hydrazino-4-methylbenzoic acid hydrochloride (Example 3A, 353 mg, 1.74 mmol, 1.0 eq) in 15 mL of ethanol were added 2-cyano-3-ethoxy-but-2-enoic acid ethyl ester (prepared as described by Xia et al., J. Med. Chem., 1997, 40, 4372) (319 mg, 1.746 mmol, 1.0 eq) and triethylamine (242 μL, 1.74 mmol, 1.0 eq) and the mixture was heated at 65° C. overnight. The mixture was cooled to room temperature and concentrated. The crude residue was purified by flash chromatography on silica gel (loaded with CH2Cl2, and packed and eluted with gradient from 6/4 hexanes/EtOAc to elute byproducts followed by 8/2 EtOAc/hexanes and 8/2 EtOAc/MeOH to elute product) to provide the product as a brown solid (464 mg, 68%). HPLC (4 minute 10-95 gradient) tR 1.97 min; MS m/z 304.1 [M+H]+

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