Selected monosubstituted pyridines, pyrazines, pyrimidines, and their N-oxides, having an electron-donating substituent, were successfully brominated under very mild conditions. The N-oxide function itself is not sufficient to cause these? r-deficient systems to undergo electrophilic aromatic halogenation. Only strongly electron-donating substituents (amino groups) activate the heterocyclic nucleus toward bromination. These substituents direct ...
