[OH-].[K+].[I-].[NH2:4][N+:5]1[CH:10]=[CH:9][CH:8]=[CH:7][CH:6]=1.[F:11][C:12]([F:21])([F:20])[C:13]#[C:14][C:15]([O:17][CH2:18][CH3:19])=[O:16]>O.ClCCl>[F:11][C:12]([F:20])([F:21])[C:13]1[C:14]([C:15]([O:17][CH2:18][CH3:19])=[O:16])=[C:6]2[CH:7]=[CH:8][CH:9]=[CH:10][N:5]2[N:4]=1
A mixture of 2.1 g (37.6 mmol) of potassium hydroxide and 6.7 g (30.1 mmol) of aminopyridinium iodide in 20 ml of water is added to a solution of 2.5 g (15.1 mmol) of ethyl 4,4,4-trifluorobut-2-ynoate in 25 ml of dichloromethane. After stirring for 5 h at ambient temperature, water is added and the mixture is extracted with dichloromethane. The organic phase is washed with water, dried over magnesium sulphate, filtered and concentrated to dryness. The crude product is purified by chromatography over silica gel eluted with an 80/20 heptane/ethyl acetate mixture. 2.8 g (73%) of ethyl 2-trifluoromethylpyrazolo[1,5-a]pyridine-3-carboxylate are obtained in the form of a yellow solid.
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