[Cl:1][C:2]1[CH:13]=[CH:12][CH:11]=[C:10]([Cl:14])[C:3]=1[NH:4][C:5]1[CH:9]=[CH:8][S:7][CH:6]=1.C(N(CC)CC)C.[CH2:22]([O:24][C:25](=[O:29])[C:26](Cl)=[O:27])[CH3:23].O>O1CCCC1.C(OCC)(=O)C>[CH2:22]([O:24][C:25](=[O:29])[C:26]([C:6]1[S:7][CH:8]=[CH:9][C:5]=1[NH:4][C:3]1[C:10]([Cl:14])=[CH:11][CH:12]=[CH:13][C:2]=1[Cl:1])=[O:27])[CH3:23]2.44 g (10 mmoles) of 3-(2,6-dichloroanilino)thiophen, 1.01 g of triethylamine and 1.37 g (10 mmoles) of chlorooxalic acid ethyl ester are stirred in 20 ml of tetrahydrofuran at room temperature for 10 hours. 100 ml each of water and ethyl acetate are added, and the organic phase is dried and concentrated. Recrystallization of the residue from ethanol gives 3-(2,6-dichloroanilino)-2-thiophenglyoxylic acid ethyl ester.
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