The selective halogenation of complex (hetero)aromatic systems is a critical yet challenging transformation that is relevant to medicinal chemistry, agriculture, and biomedical imaging. However, current methods are limited by toxic reagents, expensive homogeneous second- and third-row transition metal catalysts, or poor substrate tolerance. Herein, we demonstrate that porous metal–organic frameworks (MOFs) containing terminal Co(III) halide sites represent a rare and general class of heterogeneous catalysts for the controlled installation of chlorine and fluorine centers into electron-deficient (hetero)aryl bromides using simple metal halide salts. Mechanistic studies support that these halogen exchange (halex) reactions proceed via redox-neutral nucleophilic aromatic substitution (S_NAr) at the Co(III) sites. The MOF-based halex catalysts are recyclable, enable green halogenation with minimal waste generation, and facilitate halex in a continuous flow. Our findings represent the first example of S_NAr catalysis using MOFs, expanding the lexicon of synthetic transformations enabled by these materials.

中文翻译：

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钴（III）卤化物金属-有机框架驱动催化卤素交换

复杂（杂）芳香族系统的选择性卤化是与药物化学、农业和生物医学成像相关的关键但具有挑战性的转变。然而，目前的方法受到有毒试剂、昂贵的均相第二和第三行过渡金属催化剂或底物耐受性差的限制。在此，我们证明含有末端Co（III）卤化物位点的多孔金属有机框架（MOF）代表了一类罕见且通用的多相催化剂，用于使用简单的方法将氯和氟中心受控安装到缺电子（杂）芳基溴中。金属卤化物盐。机理研究支持这些卤素交换 (halex) 反应通过Co(III) 位点上的氧化还原中性亲核芳族取代 (S _N Ar) 进行。基于 MOF 的 halex 催化剂是可回收的，能够以最少的废物产生实现绿色卤化，并促进 halex 的连续流动。我们的研究结果代表了使用 MOF 进行 S _N Ar 催化的第一个例子，扩展了这些材料实现的合成转化的词汇。