A theoretical study of annular tautomerism of pyrrolotetrazoles in the gas phase
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- Zubarev, V.Y., Trifonov, R.E., Ostrovskii, V.A. et al. Chem Heterocycl Comp (2015) 51: 246. doi:10.1007/s10593-015-1692-7
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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 (1Н-, 3Н-, 5Н- and 7Н-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 5Н-tautomer where aromaticity of the tetrazole fragment is maintained. On the contrary, for pyrrolotetrazoles with electron-withdrawing substituents (CN or Cl), the most stable form is the 1Н-tautomer, where the pyrrole fragment is aromatic. This effect may be determined by the differences of the relative electron accepting of the heterocyclic half-rings.