Abstract For the first time, the tetrazole ring-opening has been observed for tetrazoloisoindoles as an example of azido-tetrazole isomerism. This process was studied in details by HPLC; conditions were found which are optimal for the azido-tetrazole equilibrium. It is shown that the tetrazole ring-opening proceeded with formation of unstable azide intermediate and subsequent extrusion of N2 molecule. Molecular geometry of the tetrazole form and possible unstable azide forms were calculated using M06–2X/cc-pVTZ method in vacuo and taking into account the effect of polarizing environment, and for azide forms – also taking into account specific intermolecular interactions with solvent. Electron density distribution within the tetrazole form was analyzed using Bader’s AIM theory. Resonance structures for azide forms were studied using NBO method. Calculated UV spectra were obtained using CAM-B3LYP/cc-pVTZ methods for all studied molecules.

中文翻译：

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2,2-二甲基-1-(1-甲基-1H-四唑并[5,1-a]异吲哚-5-基)丙烷-1-酮中的叠氮四唑异构现象

摘要 作为叠氮四唑异构现象的一个例子，首次观察到四唑并异吲哚的四唑开环。通过HPLC对这一过程进行了详细研究；找到了最适合叠氮-四唑平衡的条件。结果表明，四唑开环过程伴随着不稳定叠氮化物中间体的形成和N2分子的挤出而进行。四唑形式和可能的不稳定叠氮化物形式的分子几何形状在真空中使用 M06-2X/cc-pVTZ 方法计算，并考虑到极化环境的影响，对于叠氮化物形式 - 还考虑了与溶剂的特定分子间相互作用。使用Bader的AIM理论分析四唑形式内的电子密度分布。使用 NBO 方法研究叠氮化物形式的共振结构。