A theoretical study of annular tautomerism of pyrrolotetrazoles in the gas phase

Abstract

The structure and tautomerism of pyrrolotetrazoles have been studied with quantum-chemical methods (HF/6-31G** and DFT B3LYP/ANO-S) in the gas phase. According to the calculations of the total energies of various prototropic forms of these heterocyclic systems (1 Н -, 3 Н -, 5 Н - and 7 Н -tautomers), it was shown that for unsubstituted pyrrolotetrazole and its derivatives containing methyl substituents at the carbon atom(s), the most stable form is the 5 Н -tautomer where aromaticity of the tetrazole fragment is maintained. With electron-withdrawing substituents (CN or Cl) the most stable form is the 1 Н -tautomer where, on the contrary, the pyrrole fragment is aromatic. This effect may be determined by the differences of the relative electronegativity of the heterocyclic half-rings. How to Cite Zubarev, V. Yu.; Trifonov, R. E.; Ostrovskii, V. A.; Moderhack, D. Chem. Heterocycl. Compd. 201 5 , 51 , 246. [ Khim. Geterotsikl. Soedin. 2015 , 51 , 246.] For this article in the English edition see DOI 10.1007/s10593-015-1692-7