[CH3:1][O:2][C:3]([CH2:5]P(OC)(OC)=O)=[O:4].[H-].[Na+].[C:14]1([C:20]2[C:28]([CH:29]=O)=[C:23]3[CH:24]=[CH:25][CH:26]=[CH:27][N:22]3[N:21]=2)[CH:19]=[CH:18][CH:17]=[CH:16][CH:15]=1.C(=O)(O)[O-].[Na+]>C1(C)C=CC=CC=1>[C:14]1([C:20]2[C:28]([CH:29]=[CH:5][C:3]([O:2][CH3:1])=[O:4])=[C:23]3[CH:24]=[CH:25][CH:26]=[CH:27][N:22]3[N:21]=2)[CH:15]=[CH:16][CH:17]=[CH:18][CH:19]=1
A solution of trimethyl phosphonoacetate (4.0 g) in toluene (10 ml) was added to a mixture of sodium hydride (63%, 880 mg) in toluene (45 ml) with stirring and cooling and then heated at 60° C. for 20 minutes. To the mixture 2-phenylpyrazolo[1,5-a]pyridine-3-carbaldehyde (2.0 g) was added and heated at 60° C. for 8 hours. A saturated sodium bicarbonate solution (30 ml) was added to the reaction mixture and extracted with ethyl acetate (30 ml, 2 times). The extract was washed with brine (30 ml), dried over magnesium sulfate and evaporated in vacuo. The residue was recyrstallized from a mixture of ethyl acetate and isopropyl alcohol to give crystals of methyl 3-(2-phenylpyrazolo[1,5-a]pyridin-3-yl)acrylate (trans isomer) (1.34 g).
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