Organic syntheses using microwave irradiation reduction reactions

Although the first publications concerned with the possibilities of use of microwave irradiation in organic synthesis appeared in 1980 s [12,13] and in polymer chemistry even earlier at the end of 1960 s [14], the sudden growth of interest in the application of microwave irradiation in almost all fields of chemistry took place at the end of 1980 s. Nowadays, there is hardly find any reaction that has not been attempted under microwave conditions. The application of microwaves in chemistry is therefore so attractive that from the very beginning it was realized that a number of chemical processes can be carried out with a substantial reduction in the reaction time in comparison to conventional processes. Reactions that usually take many hours or days, under influence of microwave irradiation can be run in considerably shorter time of several minutes or even seconds [15]. These phenomena are not fully understood yet however, there are two groups of theories that are proposed to explain the reduction of the reaction time under microwave conditions in comparison with processes under conventional conditions. 

The 2-pyridone core structure is present in a wide range of compounds with antibacterial, antifungal, and antitumor activity members of this family also play an important role in Alzheimer s disease. By employing microwave-assisted organic synthesis, efficient conditions have been established for introduction of ami-nomethylene substituents in highly substituted bicyclic 2-pyridones. To incorporate tertiary aminomethylene substituents in the 2-pyridone framework, a microwave-assisted Mannich reaction using preformed imminium salts proved to be effective. Primary amino methylene substituents were introduced via cyanodehalogenation then borane dimethyl sulfide reduction of the afforded nitrile (Scheme 10.36) [78]. Microwave irradiation proved superior to traditional conditions for these transformations. 

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