Nitro and aminobenzimidazoles

A summary of the preparation methods of 2 tautomeric and 4 N-methylated benzimidazoles with a nitro group on the benzene ring (1–6) and with an amino group in the same positions (7–12) were summarized. Annular tautomerism of the title compounds 1–12 has been studied using ¹H, ¹³C and ¹⁵N NMR spectra in liquid and solid state (CPMAS), UV spectra and quantum chemical calculations.