[NH2:1][C:2]1[S:3][C:4]([CH2:11][CH3:12])=[CH:5][C:6]=1[C:7]([O:9]C)=O.[N:13]([CH2:16][C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1)=[C:14]=[O:15].[H-].[Na+].Cl>O.O1CCCC1>[CH2:16]([N:13]1[C:7](=[O:9])[C:6]2[CH:5]=[C:4]([CH2:11][CH3:12])[S:3][C:2]=2[NH:1][C:14]1=[O:15])[C:17]1[CH:22]=[CH:21][CH:20]=[CH:19][CH:18]=1To a mixture of methyl 2-amino-5-ethylthiophene-3-carboxylate (5 g), (isocyanatomethyl)benzene (3.33 mL) and tetrahydrofuran (50 mL) was added sodium hydride (1.18 g), and the mixture was stirred at 60° C. for 5 hr. The reaction mixture was diluted with water, and the mixture was adjusted to pH 4 with 1N hydrochloric acid, and extracted with ethyl acetate. The obtained ethyl acetate layer was washed with saturated brine, and dried over anhydrous magnesium sulfate. The solvent was evaporated under reduced pressure. The obtained residue was recrystallized from ethyl acetate to give the title compound as colorless crystals (2.1 g, 25%).
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