C([O-])(=[O:3])C.[NH4+].[CH2:6]([O:8][C:9]([C:11]1[C:12]([Cl:21])=[C:13]2[S:20][CH:19]=[CH:18][C:14]2=[N:15][C:16]=1Cl)=[O:10])[CH3:7]>C(O)(=O)C>[CH2:6]([O:8][C:9]([C:11]1[C:16](=[O:3])[NH:15][C:14]2[CH:18]=[CH:19][S:20][C:13]=2[C:12]=1[Cl:21])=[O:10])[CH3:7]Ammonium acetate (161 mg, 2.1 mmol) was added to a stirred solution of 5,7-dichloro-thieno[3,2-b]pyridine-6-carboxylic acid ethyl ester (3) (530 mg, 1.9 mmol) in glacial acetic acid at room temperature. The solution was heated at 140° C. for 48 h. The hot solution was poured into ice water. The solids formed were filtered, washed by water, and dried. The crude product was recrystallized by CH2Cl2 to yield 273 mg (60%) of 7-chloro-5-oxo-4,5-dihydro-thieno[3,2-b]pyridine-6-carboxylic acid ethyl ester as white solids. MP 206° C.; 1H NMR (400 MHz, DMSO-d6) δ 1.28 (t, J=7.2 Hz, 3H), 4.29 (q, J=7.2 Hz, 2H), 7.10 (d, J=5.2 Hz, 1H), 8.13 (d, J=5.2 Hz, 1H) ppm; MS m/z=240 amu (M++1).
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