A highly efficient multicomponent synthesis of pyridones and pyrimidones by a [2+2+2] strategy

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The reaction of N-silylated iminoethers with 2-substituted acetyl chlorides yields activated 2-azadienes. These were shown to react with electron-deficient acetylenic dienophiles to yield pyridones. They also react with quinones to give the corresponding aromatized cycloadducts in good yields. The reaction of 2-azadienes with activated nitriles provided a very practical route towards polysubstituted pyrimidones. A multicomponent protocol is reported which combines a N-t-butyldimethylsilyl iminoether, an acetyl chloride derivative and a dienophile in the presence of triethylamine without isolation of any intermediate. This provides an extremely practical and versatile route to various mono- and polycyclic azaaromatics with a predictable substitution pattern. Yields ranged from 43 % to 94 % for the complete sequence.