C([O:3][C:4](=[O:18])[CH:5]=[CH:6][CH:7]=[CH:8][C:9]1[CH:14]=[CH:13][C:12]([O:15][CH3:16])=[CH:11][C:10]=1[Cl:17])C.C1COCC1.[OH-].[K+]>CO.O>[Cl:17][C:10]1[CH:11]=[C:12]([O:15][CH3:16])[CH:13]=[CH:14][C:9]=1[CH:8]=[CH:7][CH:6]=[CH:5][C:4]([OH:18])=[O:3]The crude ester product was taken up in 200 mL each of methanol and THF and then cooled to 0° C. To this mixture was added a solution of KOH (19 g, 0.338 mol, 3 eq.) in 200 mL H2O. The mixture was stirred at room temperature for 1.5 hr and the organic solvent was evaporated. The aqueous layer was diluted with 300 mL H2O and washed with ether to remove the mineral oil. It was then cooled in an ice-bath and acidified with concentrated HCl to ˜pH 2. The thick precipitate was filtered and rinsed with water, then dried in a vacuum oven at 75° C. to provide 26.2 g of 5-(2-chloro-4-methoxy-phenyl)-penta-2,4-dienoic acid.
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