[F:1][C:2]1[CH:7]=[CH:6][C:5]([C:8]2[N:9]=[N:10][S:11][C:12]=2[CH:13]=O)=[CH:4][CH:3]=1.C(OP([CH2:23][C:24]([O:26]CC)=[O:25])(OCC)=O)C.[H-].[Na+].Cl>CN(C)C=O>[F:1][C:2]1[CH:3]=[CH:4][C:5]([C:8]2[N:9]=[N:10][S:11][C:12]=2/[CH:13]=[CH:23]/[C:24]([OH:26])=[O:25])=[CH:6][CH:7]=1A mixture of 4-(4-fluorophenyl)-1,2,3-thiadiazole-5-carbaldehyde (180 mg), ethyl diethylphosphonoacetate (450 mg), sodium hydride (60% in oil, 40 mg) and N,N-dimethylformamide (3 ml) was stirred at room temperature for 2 hrs. The reaction mixture was poured into a 1N aqueous hydrochloric acid solution and the mixture was extracted with ethyl acetate. The ethyl acetate layer was concentrated, and a 6N aqueous hydrochloric acid solution (3 ml) and acetic acid (3 ml) were added to the residue. The mixture was stirred for 3 hrs. with heating under reflux. The reaction mixture was concentrated and poured into water. The precipitated solids were collected by filtration, washed with water and dried to give (2E)-3-[4-(4-fluorophenyl)-1,2,3-thiadiazol-5-yl]acrylic acid (130 mg, yield 60%) as a pale-yellow solid.
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