| abstract |
A 1-alkyl-5-phenyl-7-chloro-1,3-dihydro-2H-1,4-benzodiazepine-2one derivative, which is useful as a tranquilizer, a muscle relaxant or a spasmolytic, is purified by dissolving a crude benzodiazepine derivative in hydrochloric acid, partially neutralizing by adding an aqueous alkali solution to deposit impurities such as 2-methylamino-5-chlorobenzophenone, removing the deposited impurities from the solution by filtration, further adding the aqueous alkali solution to the filtrate and separating the purified benzodiazepine derivative from the filtrate by solvent extraction. |