[F:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2[N:12]([CH3:13])[N:11]=[CH:10][C:9]=2[CH:14]=O)=[CH:4][CH:3]=1.[H-].[Na+].C(OP([CH2:26][C:27]([O:29]CC)=[O:28])(OCC)=O)C.CN(C)C=O>O>[F:1][C:2]1[CH:3]=[CH:4][C:5]([C:8]2[N:12]([CH3:13])[N:11]=[CH:10][C:9]=2/[CH:14]=[CH:26]/[C:27]([OH:29])=[O:28])=[CH:6][CH:7]=1A mixture of 5-(4-fluorophenyl)-1-methyl-1H-pyrazole-4-carbaldehyde (350 mg), sodium hydride (60% in oil, 120 mg), ethyl diethylphosphonoacetate (673 mg) and N,N-dimethylformamide (10 ml) was stirred at room temperature for 1 hr. The reaction mixture was poured into water, and the precipitated solids were collected by filtration. After drying with airflow, the solids were dissolved in a mixed solvent of tetrahydrofuran (10 ml) and ethanol (10 ml). A 1N aqueous sodium hydroxide solution (5 ml) was added and the mixture was stirred at room temperature for 2 hrs. The reaction mixture was poured into a 10% aqueous citric acid solution and the precipitated solids were collected by filtration, washed with water and dried with airflow to give (2E)-3-[5-(4-fluorophenyl)-1-methyl-1H-pyrazol-4-yl]acrylic acid (354 mg, 84%) as crystals. Recrystallization thereof from methanol-isopropyl ether gave colorless prism crystals. melting point: 212-213° C.
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