Synthesis and characterization of a series of new compounds: Pyridobenzodiazepines with carbonyl group at C6-position

N²-methyl-N²-phenyl-pyridine-2,3-diamine was synthesized in two reaction steps, substitution and reduction, using 2-chloro-3-nitro-pyridine as the starting material. Pyridobenzodiazepines were obtained by the cyclization reaction of N²-methyl-N²-phenyl-pyridine-2,3-diamine with n-Propionic acid, n-butyrate or phenylacetic acid, respectively, and then were oxidized to form pyridobenzodiazepines with carbonyl group in methylene chloride solution by oxygen gas at room temperature. The yields are 72-95%. HPLC-MS, NMR and X-ray diffraction analysis confirmed the structures of the target compounds.