Computational Study of 2-Aminopyrimidine, 2-Amino-5-nitropyrimidine, and the Corresponding S,S-Dimethyl-N-sulfilimines

Article abstract of DOI:10.1021/j100317a015

In order to better understand why the formation of sulfilimine intermediates facilitates the oxidation of some aminoazines, we have carried out a computational analysis of 2-aminopyrimidine (II) and S,S-dimethyl-N-(2-pyrimidinyl)sulfilimine (III).We also investigated a system for which the procedure fails: 2-amino-5-nitropyrimidine (VI) and the corresponding sulfilimine (VII).An ab initio SCF approach (GAUSSIAN 82) was used to compute the optimized structures and electrostatic potentials of these molecules.We found that the most negative regions in the sulfilimine intermediates as well as in the original aminoazines are associated with one or both of the ring nitrogens rather than the exocyclic one that is to be oxidized.An important new feature in the case of III is the development of extensive negative potentials above and below the ring plane, which make the exocyclic nitrogen much more accessible to electrophiles than it is in II.Thus the possibility of oxidation occuring at this site is significantly greater in III than in II.The presence of the electron-withdrawing -NO2 in VI prevents the development of extensive, relatively strong negative regions above and below the ring; accordingly there does not occur, in VII, an analogous increase in electrophilic accessibility to the exocyclic nitrogen.