摘要:
2,3-Diaminopyridine reacts with cyclohexanone to form dihydro-4-azabenzimidazole-2-spirocyclohexane. Reaction of this intermediate with a variety of nucleophiles (e.g., water, phenylmercaptan, ethanol, dimethylamine, and diethylmalonate) in the presence of MnO2 results in addition to the 5-position. Subsequent acidic hydrogenation affords 6-substituted-2,3-diaminopyridines, key synthons for the synthesis of bicyclic heterocycles.