C[O:2][C:3]([C:5]1[S:9][C:8]2[CH:10]=[CH:11][C:12]([Cl:14])=[CH:13][C:7]=2[CH:6]=1)=O.O.[NH2:16][NH2:17]>C(O)C>[Cl:14][C:12]1[CH:11]=[CH:10][C:8]2[S:9][C:5]([C:3]([NH:16][NH2:17])=[O:2])=[CH:6][C:7]=2[CH:13]=18.00 g (35.3 mmols) of 5-chloro-2-benzo[b]thiophenecarboxylic acid methyl ester and 10 ml of hydrazine hydrate in 100 ml of absolute ethanol are boiled under reflux for 45 minutes. The cooled suspension is diluted with 100 ml of ice water and the product is filtered off. It is washed with two 40 ml portions of methanol and dried in vacuo. 5-Chloro-2-benzo[b]thiophene-carboxylic acid hydrazide with a melting point of 254°-255° is obtained.
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