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<p>Pyridine derivatives are one of the most common heterocycles in chemistry. The 3-halopyridines are generally synthesized by indirect methods, including functional group conversion or a temporary dearomatization–rearomatization process. Although the direct electrophilic halogenation of pyridines provides straightforward access to 3-halopyridines, it has been rarely reported owing to the poor π nucleophilicity of pyridines. Here we describe a general direct regioselective C-3 halogenation of pyridines promoted by an ether solvation effect. This radical process enables the regioselective reaction to occur at the C-3 position of pyridines, rather than other aromatic C–H bonds, and can be applied to the late-stage halogenation of complex molecules. The mechanistic studies show that the interaction between the pyridine substrate, ether solvent and haleniums plays a dominant role in the reactivity and regioselectivity.</p><p></p>

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Direct regioselective C-3 halogenation of pyridines

  • 期刊论文

  • 发表日期：

    2025年11月5日

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  • Chao Li,
  • Xinyao Li,
  • Jiaxing Li,
  • Zhixing Wang,
  • Dunhuang Ouyang,
  • Ning Jiao,
  • Song Song

摘要

Pyridine derivatives are one of the most common heterocycles in chemistry. The 3-halopyridines are generally synthesized by indirect methods, including functional group conversion or a temporary dearomatization–rearomatization process. Although the direct electrophilic halogenation of pyridines provides straightforward access to 3-halopyridines, it has been rarely reported owing to the poor π nucleophilicity of pyridines. Here we describe a general direct regioselective C-3 halogenation of pyridines promoted by an ether solvation effect. This radical process enables the regioselective reaction to occur at the C-3 position of pyridines, rather than other aromatic C–H bonds, and can be applied to the late-stage halogenation of complex molecules. The mechanistic studies show that the interaction between the pyridine substrate, ether solvent and haleniums plays a dominant role in the reactivity and regioselectivity.