Synthesis of 4-dialkylaminopyridine derivatives through ring-rearrangement of 3-nitro-2H-pyran-2-one acetamidines

A new synthesis of substituted 4-dialkylaminopyridines was developed, starting from 3-nitropyran-2-one N-functionalized amidines. Secondary amines were reacted with the amidines in a sealed tube and in ethanol as the solvent yielding exclusively 4-dialkylaminopyridine derivatives or a mixture with 4-methylpyridine derivative, depending on the C-α-linked substituents of the starting amidine. Structural elucidation of the 4-dialkylaminopyridines revealed their existence as two tautomeric forms, depending on the solvent.