Quantum chemical studies of pyrimidin-4-ones

Abstract

Quantum chemical calculations of energies, electronic structures, and molecular geome tries of 3,5,6 trimethylthieno[2,3 d]pyrimidin 4 one (1), tricyclic 2,3 tri , 2,3 tetra , and 2,3 pentamethylene substituted 5,6 dimethylthieno[2,3 d]pyrimidin 4 ones (2-4), carboxy lic acids 5-8 resulting from oxidation of compounds 1-4 at the methyl group in position 5 of thienopyrimidine, methyl esters of these acids (9-12), and products of ipso nitration of esters (13-16) were performed in terms of the HF and DFT (B3LYP) approximations with the 3 21G basis set. Also, calculations for mixed anhydrides of nitric acid and carboxylic acids 17-20 were carried out. The possible causes of differences in the behaviors of 3 unsubstituted and 3 substituted thieno[2,3 d]pyrimidin 4 ones were discussed.Key words: thieno[2,3 d]pyrimidin 4 ones, nitric acid oxidation, ipso substitution, quan tum chemical calculations, Hartree-Fock method (HF), DFT/B3LYP 3 21G method.

Recent advances in ipso-nitration reactions

“…[23][24][25][26] This research also revealed that, in the absence of a substituent in position 3, the electrophilic ipsosubstitution of the methyl group by a nitro group with the formation of a 5-nitro derivative would take place. Thus, we found that, when the interaction of the compounds with electron-donating groups at N-3 position of the thienopyrimidine molecule was conducted with a nitrating mixture (HNO3/H2SO4 at 0-5 o C), instead of the ipso-nitration of methyl groups at C-5 the reaction proceeded in an unexpected direction, i.e., there was oxidation of the methyl groups.…”