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

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To a stirred solution of 3-hydrazino-4-methylbenzoic acid hydrochloride (Example 3A, 478 mg, 2.36 mmol, 1.0 eq) in 20 mL of ethanol were added ethyl(ethoxymethylene)cyanoacrylate (399 mg, 2.36 mmol, 1.0 eq) and triethylamine (329 μL, 2.36 mmol, 1.0 eq) and the mixture was heated at 65° C. for 5 hrs. After standing at room temperature overnight, additional 3-hydrazino-4-methylbenzoic acid hydrochloride (159 mg, 0.78 mmol, 0.3 eq) and triethylamine (110 μL, 0.78 mmol, 0.3 eq) and heated for 2.5. The mixture was cooled to room temperature and concentrated. The crude residue was purified by flash chromatography on silica gel (gradient elution from 7/3 hexanes/EtOAc to 1/1 to elute byproducts followed by EtOAc and 9/1 EtOAc/MeOH to elute product) to provide the product as a brown solid (464 mg, 68%). HPLC (4 minute 10-95 gradient) tR 1.87 min; MS m/z 290.1 [M+H]+; 1H NMR (CD3OD), δ 8.08 (d, J=7.0 Hz, 1 H), 7.93 (s, 1 H), 7.76 (s, 1 H), 7.54 (d, J=8.0 Hz, 1 H), 4.29 (q, J=7.1 Hz, 2 H), 2.19 (s, 3 H), 1.35 (d, J=7.1 Hz, 3 H), ppm; 13C NMR (CD3OD), δ 166.5, 163.8, 150.4, 141.7, 139.9, 135.3, 130.8, 129.5, 128.6, 93.8, 58.8, 15.8, 12.9 ppm.

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