Bischler-napieralski Ring Closing Reaction, Oxidation Reaction

Bischler-Napieralski reaction is the dehydration cyclization of aromatic ring with the condensed. product ofβ-phenylethylamine with carboxylic acid or carboxylic acid derivatives to form 3,4-Dihydro-isoquinoline derivatives. The tricyclic benzodiazepine compounds and isoquinoline compounds t have important medical applications.Oxidation is one of the most common reaction in chemical industry, but the introduction of carbonyl group to one carbon atom has been a problem in the field of organic synthesis. It generally requires an sever oxidation condition—high temperature, high pressure, strong acid, etc., or employing strong oxidizing agents. However, the preliminary work of our research group has found that, in some case, when a carboxylic acid reacted with a methyleneα_in Bischler-Napieralski reaction, self-oxidation of the product were observed in air to generate a tricyclic benzodiazepine compounds withα_ketone carbonyl structure.In this paper, N2-methyl-N2-phenyl-pyridine-2,3-diamine was synthesized in two reaction steps including substitution and reduction with 2-chloro-3-nitro-pyridine as the starting material. Pyridine Benzodiazepine was obtained by the cyclization reaction of compound with n-Propionic acid, n-butyrate or phenylacetic acid. It is oxidized to form a Pyridine Benzodiazepine with carbonyl group in methylene chloride solution by air at room temperature, The yield is 33-95.5%. HPLC-MS, NMR analysis and single crystal X-ray diffraction confirmed the structure of the target compounds.The method proposed in this paper that preperation of tricyclic benzodiazepine compounds withα_ketone carbonyl structure by the direct oxidation of in Bischler-Napieralski reaction product is economic, efficient and no pollution.at the same time, this method can bo used to synthesize a diverse of potentially pharmacologically active compounds, It shows potential value in new drug discovery.