B.[CH2:2]([O:4][C:5]([C:7]1[CH:8]=[N:9][N:10]([C:13]2[CH:21]=[CH:20][C:16]([C:17](O)=[O:18])=[CH:15][CH:14]=2)[C:11]=1[CH3:12])=[O:6])[CH3:3].C(=O)(O)[O-].[Na+]>O1CCCC1>[CH2:2]([O:4][C:5]([C:7]1[CH:8]=[N:9][N:10]([C:13]2[CH:14]=[CH:15][C:16]([CH2:17][OH:18])=[CH:20][CH:21]=2)[C:11]=1[CH3:12])=[O:6])[CH3:3]0.93M Tetrahydrofuran solution of borane (18 ml) was added dropwise to a solution of 4-[4-(ethoxycarbonyl)-5-methyl-1H-pyrazol-1-yl]benzoic acid (3.0 g) in tetrahydrofuran (50 ml) at 0° C. and stirred at room temperature for three hours. After completion of the reaction, a saturated aqueous solution of sodium bicarbonate was added therein and extracted with ethyl acetate three times. The organic layer was washed with saturated brine, dried oner anhydrous sodium sulfate and concentrated in vacuo. The resulting residue was purified with NH silica gel column chromatography (n-hexene/ethyl acetate) to give 1-[4-(hydroxymethyl)phenyl]-5-methyl-1H-pyrazole-4-carboxylic acid ethyl ester (1.93 g) as a white solid.
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