反应详情

A solution of 3-hydrazino-4-methyl benzoic acid (1.0 g, 4.93 mmol), malonaldehyde(bismethylacetate) (0.82 mL, 4.93 mmol), and concentrated HCl (1 mL) in EtOH (20 mL) was heated to reflux for 4 h. After cooling to room temperature, the reaction was poured into ice water, neutralized with 2N NaOH, and extracted with CH2Cl2 (3×). The organic layers were dried over Na2SO4, filtered and concentrated to afford 4-methyl-3-pyrazol-1-yl-benzoic acid ethyl ester (536 mg, 47%) as a yellow oil. A solution of the pyrazole (536 mg, 2.33 mmol) and bromine (0.167 mL, 3.26 mmol) in CHCl3 (15 mL) was refluxed for 4.5 h then cooled to room temperature. The solvent was evaporated to an orange oil. Purification using chromatography on silica gel (1:1 EtOAc/hexanes) yielded 3-(4-bromo-pyrazol-1-yl)-4-methyl-benzoic acid ethyl ester (0.739 g, 99%) as a yellow solid.

1. temperatureto reflux for 4 h
2. extractionextracted with CH2Cl2 (3×)
3. dry with materialThe organic layers were dried over Na2SO4
4. filtrationfiltered
5. concentrationconcentrated