[C:1]([C:3]1[C:8]2[CH2:9][C:10](=NN)[C:11]3[CH:17]=[C:16]([O:18][CH3:19])[CH:15]=[CH:14][C:12]=3[S:13][C:7]=2[CH:6]=[CH:5][CH:4]=1)#N.[OH-:22].[Na+].C(O)C[O:26]CCO>O>[C:1]([C:3]1[C:8]2[CH2:9][CH2:10][C:11]3[CH:17]=[C:16]([O:18][CH3:19])[CH:15]=[CH:14][C:12]=3[S:13][C:7]=2[CH:6]=[CH:5][CH:4]=1)([OH:26])=[O:22]600 mg of 9-cyano-2-methoxy-10,11-dihydro-11-oxo-dibenzo[b,f]thiepin hydrazone and 600 mg of sodium hydroxide were added to 10 ml of diethylene glycol and the resulting mixture was heated with stirring at 190°-200° C. for 5 hours. After cooling, water was added to the mixture, which was extracted with benzene. The aqueous layer was acidified with hydrochloric acid and extracted with benzene. The benzene extract was washed with water and dried over anhydrous sodium sulfate. The solvent was evaporated to obtain the residue, which was chromatographed over silica gel and eluted with chloroform-ether (10:1). There was obtained 9-carboxy-2-methoxy-10,11-dihydrodibenzo[b,f]thiepin. Recrystallization from benzene afforded 140 mg of the desired product as colorless needles having a melting point of 185°-187° C.
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