Microwave-assisted synthesis of highly substituted aminomethylated 2-pyridones

By employing microwave-assisted organic synthesis (MAOS) efficient conditions to introduce aminomethylene substituents in highly substituted bicyclic 2-pyridones have been established. Primary amino methylene substituents were introduced via a cyanodehalogenation followed by a borane dimethyl sulfide reduction of the afforded nitrile. In both of these transformations, microwave irradiation proved to be superior to traditional conditions and the primary amines were obtained in good overall yields (55-58% over three steps). To incorporate tertiary aminomethylene substituents in the 2-pyridone framework, a microwave-assisted Mannich reaction using preformed iminium salts proved to be effective. Thus highly substituted 2-pyridones were obtained in 48-93% yields.