Regioselective Syntheses of Bis(indazolyl)methane Isomers: Controlling Kinetics and Thermodynamics via Tunable Non-Innocent Amines

The selective synthesis of regioisomers from ambident N-heterocycles remains a challenge in organic chemistry. We report a general and modular method for the regioselective syntheses of bis(indazolyl)methane isomers, in which the outcome is controlled by the nature of the base. Specifically, we employed structurally diverse amines as noninnocent bases, whose steric and electronic propertiesparticularly their pKaH and ability to act as methylene carriers or activatorsplay a decisive role in directing product distribution. By fine-tuning the amine structure, we achieved selective access to symmetrical and unsymmetrical isomers under mild, one-step conditions, without intermediate isolation. The use of amines over conventional inorganic bases was essential to enable both chemo- and regioselective control, while minimizing overactivation or competing pathways. Experimental findings were supported by DFT calculations that rationalize the observed selectivity through differential activation energies and intermediate stabilities. The methodology accommodates both classical methylenating agents (e.g., CH2Br2) and in situ generated ammonium-based donors. All compounds were fully characterized, and key products were confirmed by single-crystal X-ray diffraction (SCXRD). This strategy highlights the utility of noninnocent amines as tunable reagents for regioselective transformations of ambident nucleophiles, with broad potential applications in ligand design, supramolecular chemistry, and heterocyclic synthesis.由两可亲核氮杂环（ambident N-heterocycles）制备区域异构体的选择性合成方法，始终是有机化学领域的核心挑战之一。本研究报道了一种通用且模块化的双(吲唑基)甲烷（bis(indazolyl)methane）区域异构体区域选择性合成策略，产物的分布由所使用碱的性质精准调控。具体而言，本研究采用结构多样的胺类作为非惰性碱（noninnocent bases），这类碱的空间位阻与电子效应——尤其是其pKaH值、作为亚甲基载体或活化剂的能力——对产物分布的定向调控起到决定性作用。通过对胺类结构进行精细微调，我们可在温和的一步法反应条件下选择性获得对称与非对称的区域异构体，无需分离中间体。相较于传统无机碱，使用胺类碱对于实现化学选择性与区域选择性的双重调控至关重要，同时可最大限度抑制过度活化及副反应路径的发生。实验结果得到了密度泛函理论（DFT）计算的佐证，该计算通过对比不同反应路径的活化能与中间体稳定性，合理阐释了所观测到的选择性现象。该合成策略可兼容经典亚甲基化试剂（如二溴甲烷CH₂Br₂）以及原位生成的铵基供体。所有化合物均得到了充分表征，关键产物通过单晶X射线衍射（SCXRD）完成了结构确认。该策略凸显了非惰性胺类作为可调谐试剂，在两可亲核试剂区域选择性转化中的应用价值，其在配体设计、超分子化学以及杂环合成领域均具备广阔的应用前景。