A simple and green protocol was developed for the reductive cyclization of o-phenylenediamine with CO₂ and BH₃NH₃ to yield 1H-benzimidazole. The desired 1H-benzimidazole derivatives were produced under mild conditions. Mechanism investigation indicated that the coordination of o-phenylenediamine with the boron atom of BH₃NH₃ promoted the transfer of the formyl group to form a stable intermediate, which facilitated the intramolecular nucleophilic addition-elimination for the formation of target product. In this process, BH₃NH₃ served multifunctional roles, acting as a reducing agent and a formylation catalyst.

中文翻译：

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邻苯二胺与CO2和BH3NH3还原环化合成1H-苯并咪唑衍生物

为邻苯二胺与 CO ₂和 BH ₃ NH ₃的还原环化反应生成1 H-苯并咪唑，开发了一种简单且绿色的方案。所需的 1 H-苯并咪唑衍生物在温和条件下制备。机理研究表明邻苯二胺与BH ₃ NH ₃的硼原子的配位促进了甲酰基转移形成稳定的中间体，从而促进了分子内亲核加成消除形成目标产物。在这个过程中，BH ₃ NH ₃ 充当多功能角色，充当还原剂和甲酰化催化剂。