Reactivity of 2-amino[1,2,4]triazolo[1,5-D°]-pyrimidines with various saturation of the pyrimidine ring towards electrophiles

The effect of pyrimidine ring saturation in 2-amino[1,2,4]triazolo[1,5-D degrees]pyrimidines on their reactivity as polyfunctional N-nucleophiles was studied by computational methods (reactivity indices and transition state energy values for the model reaction of S (N)2 alkylation with chloromethane, DFT B3LYP/6-311++G(2d,2p)), as well as experimentally (alkylation with benzyl bromide). The global nucleophilicity of partially hydrogenated aminotriazolopyrimidines was shown to be substantially higher than for aromatic analogs. The most likely sites for electrophilic attack in partially hydrogenated aminotriazolopyrimidines were the N-1 and N-3 atoms, as well as the amino group, and the probability of attack at the N-3 atom increased with harder electrophiles. The nucleophilicity of amino group and the N-1 atom was substantially decreased in aromatic aminotriazolopyrimidines, where the most likely sites of attack by hard electrophiles were the N-3 and N-4 atoms.