Benzimidazoles are common in nature, medicines, and materials. Numerous strategies for preparing 2-arylbenzimidazoles exist. In this work, 1,2-disubstituted benzimidazoles were prepared from various mono- and disubstituted ortho-phenylenediamines (OPD) by iron-catalyzed oxidative coupling. Specifically, O2 and FeCl3·6H2O catalyzed the cross-dehydrogenative coupling and aromatization of diarylmethyl and dialkyl benzimidazole precursors. N,N'-Disubstituted-OPD substrates were significantly more reactive than their N,N-disubstituted isomers, which appears to be relative to their propensity for complexation and charge transfer with Fe3+. The reaction also converted N-monosubstituted OPD substrates to 2-substituted benzimidazoles; however, electron-poor substrates produce 1,2-disubstituted benzimidazoles by intermolecular imino-transfer. Kinetic, reagent, and spectroscopic (UV-vis and EPR) studies suggest a mechanism involving metal-substrate complexation, charge transfer, and aerobic turnover, involving high-valent Fe(IV) intermediates. Overall, comparative strategies for the relatively sustainable and efficient synthesis of 1,2-disubstituted benzimidazoles are demonstrated.

中文翻译：

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铁的异构异构邻苯二胺底物的铁催化交叉脱氢偶联反应制备1,2-二取代苯并咪唑。

苯并咪唑在自然界，药物和材料中很常见。存在制备2-芳基苯并咪唑的许多策略。在这项工作中，通过铁催化的氧化偶联，由各种单取代和二取代的邻苯二胺（OPD）制备1,2-二取代的苯并咪唑。具体而言，O 2和FeCl 3·6H 2 O催化二芳基甲基和二烷基苯并咪唑前体的交叉脱氢偶联和芳构化。N，N′-二取代-OPD底物比其N，N-二取代的异构体具有更高的反应活性，这似乎与其相对于与Fe3 +络合和电荷转移的倾向有关。该反应还将N-单取代的OPD底物转化为2-取代的苯并咪唑。然而，贫电子底物通过分子间亚氨基转移产生1,2-二取代的苯并咪唑。动能 试剂和光谱学（紫外可见和EPR）研究表明，这种机制涉及金属-底物的络合，电荷转移和有氧转化，涉及高价Fe（IV）中间体。总的来说，证明了比较可持续和有效合成1,2-二取代苯并咪唑的比较策略。