A mixture of 3.19 g. (0.01 mole) of 7-chloro-5-(o-chlorophenyl)-2-hydrazino-3H-1,4-benzodiazepine and 100 ml. of tetrahydrofuran, under nitrogen, was cooled to 0° C. and 1 ml. of chloropropanone was slowly added with stirring. The mixture was allowed to warm to room temperature; after one-half hour all the solid had dissolved. After stirring for a total of 2 hours, thin layer chromatography (SiO2, 20% methanol/benzene) showed essentially one spot. Evaporation at room temperature in vacuo gave a light brown gum which was dissolved in absolute ether and filtered. The solution was concentrated by a stream of N2 on a steam bath to a small volume and pentane was added. After cooling in the refrigerator, the resulting crystals were collected, washed with ether and pentane and dried, yielding 3.82 g. (97%) of 7-chloro-2-[(2-chloro-1-methylethylidene)hydrazinoe]-5-(o-chlorophenyl)-3H-1,4-benzodiazepine.
