[C:1]([C:9]1[S:13][C:12]([C:14]([OH:16])=[O:15])=[CH:11][CH:10]=1)(=O)[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.[OH-].[K+].NN>C(O)CO>[CH2:1]([C:9]1[S:13][C:12]([C:14]([OH:16])=[O:15])=[CH:11][CH:10]=1)[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=15-Benzoylthiophene-2-carboxylic acid (1.2 g.) was combined with potassium hydroxide (4 g.), hydrazine (3 ml.) and ethylene glycol (8 ml.) and heated in a 140° C. oil bath. A thick, foamy slurry formed which was diluted with 10 ml. additional ethylene glycol. The bath temperature was increased to 180° C., and the reaction held at this temperature for 45 minutes. The reaction was cooled, filtered and the filtrate diluted with 75 ml. of water. The mixture was cooled in an ice bath, acidified with conc. hydrochloric acid, and product (658 mg.) recovered by filtration. Recrystallization from methanol/water gave purified 5-benzylthiophene-2-carboxylic acid (480 mg., 123°-125° C., m/e 218).
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