C([O:3][C:4]([C:6]([CH:14]([CH2:23][C:24]#[CH:25])[C:15]1[CH:20]=[CH:19][C:18]([Cl:21])=[CH:17][C:16]=1[Cl:22])([C:8]1[CH:9]=[N:10][CH:11]=[CH:12][CH:13]=1)[OH:7])=[CH2:5])C.Cl>CO>[Cl:22][C:16]1[CH:17]=[C:18]([Cl:21])[CH:19]=[CH:20][C:15]=1[CH:14]([CH2:23][C:24]#[CH:25])[C:6]([OH:7])([C:8]1[CH:9]=[N:10][CH:11]=[CH:12][CH:13]=1)[C:4](=[O:3])[CH3:5]A mixture of 2.0 g of α-(1-ethoxyvinyl)-α-[2,4-dichloro-α-(2-propynyl)-benzyl]-3-pyridinemethanol (see Example 3, 1st end product), 1 ml of concentrated hydrochloric acid and 15 ml of methanol as a clear yellow solution is held at room temperature for 1 hour. Thereafter, the mixture is evaporated under reduced pressure in order to remove methanol and the residue is neutralized with saturated aqueous sodium bicarbonate solution. The aqueous mixture is extracted with ethyl acetate and the organic phase is washed with saturated aqueous sodium chloride solution and evaporated. Finally, the residue is recrystallized from methylene chloride/n-hexane. There are obtained 1.8 g of 4-(2,4-dichlorophenyl)-3-hydroxy-3-(3-pyridyl)-6-heptyn-2-one, m.p. 132° C.
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