[C:1]([C:5]1[CH:10]=[CH:9][C:8]([C:11]2[S:15][C:14](/[CH:16]=[CH:17]/[C:18]([O:20]C)=[O:19])=[CH:13][CH:12]=2)=[CH:7][CH:6]=1)([CH3:4])([CH3:3])[CH3:2].[OH-].[Na+].Cl>C1COCC1.C(O)C>[C:1]([C:5]1[CH:6]=[CH:7][C:8]([C:11]2[S:15][C:14](/[CH:16]=[CH:17]/[C:18]([OH:20])=[O:19])=[CH:13][CH:12]=2)=[CH:9][CH:10]=1)([CH3:4])([CH3:2])[CH3:3]To a solution of methyl (E)-3-[5-(4-tert-butyl-phenyl)-thiophen-2-yl]acrylate (190 mg) of THF/ethanol (15/15 ml) was added at room temperature 2N sodium hydroxide solution (2.0 ml), and the mixture was stirred 18 hours. To the mixture was added 1N hydrochloric acid (5 ml), and the mixture was extracted with ethyl acetate. The organic layer was washed with saturated brine and dried with magnesium sulfate. Under reduced pressure, the mixture was concentrated, and the precipitated crystals were collected by filtration, which were washed with hexane to give yellow crystals of (E)-3-[5-(4-tert-butylphenyl)thiophen-2-yl]acrylic acid (149.7 mg). This compound was used for the following reaction, without subjecting further purification.
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