2-Substituted 4,5,6-triaminopyrimidines, reaction with

An interesting variation of this procedure relies upon the formation of malondialdehyde precursors in sita.44-463 Vinylogs of Vilsmeier-Haack intermediates (60),47 formed from dimethylaminoacroleins (59) and phosgene, undergo reaction with 2,4,6-triaminopyrimidine to yield 6-alkyl- and 6-aryl-substituted 2,4-diaminopyrido[2,3-d]-pyrimidines (61). Dimethylaminoacroleins were found to be unsatisfactory.44... 

The reaction involves an electrophilic attack into the 5-position of the pyrimidine ring and thus only those pyrimidines that are activated toward electrophilic substitution by the presence of electron-donating substituents at the 2- and 4-positions undergo cyclization. 2,4,6-Triaminopyrimidine, 6-aminouracil, 6-amino-2-thiouracil, 4-amino-2,4 dimercaptopyrimidine, 2,4-diaminopyrimidin-6(l/I)-one, and various 4-amino-vV-alkyl and aryl pyriinidones have all been converted into pyrido[2,3-[Pg.160]

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