Recyclization of 2,2-disubstituted 4(3H)-oxo- and 4-chloro-1,2-dihydropyrimidines to 4-aminopyridine derivatives

The intramolecular cationotropic rearrangement of salts of two-ring 2,2-disubstituted 4-chloro-1,2-dihydropyrimidines to 4-aminopyridine derivatives was observed. Recyclization to 4-aminopyridines can take place in the reaction of two-ring 2,2-disubstituted 4(3H)-oxo-1,2-dihydropyrimidines with phosphorus oxychloride without isolation of the intermediate chloro derivatives. A probable mechanism that makes it possible to assert that the observed recyclization is a variant of the intramolecular cationotropic rearrangement that is characteristic for 2,2-dialkyl-substituted 1,2-dihydropyrimidines with functional substituents (for example, oxo or chloro) in the 4 position of the ring is discussed.