Boron functional groups are often introduced in place of aromatic carbon–hydrogen bonds to expedite small-molecule diversification through coupling of molecular fragments^1,2,3. Current approaches based on transition-metal-catalysed activation of carbon–hydrogen bonds are effective for the borylation of many (hetero)aromatic derivatives^4,5 but show narrow applicability to azines (nitrogen-containing aromatic heterocycles), which are key components of many pharmaceutical and agrochemical products⁶. Here we report an azine borylation strategy using stable and inexpensive amine-borane⁷ reagents. Photocatalysis converts these low-molecular-weight materials into highly reactive boryl radicals⁸ that undergo efficient addition to azine building blocks. This reactivity provides a mechanistically alternative tactic for sp² carbon–boron bond assembly, where the elementary steps of transition-metal-mediated carbon–hydrogen bond activation and reductive elimination from azine-organometallic intermediates are replaced by a direct, Minisci⁹-style, radical addition. The strongly nucleophilic character of the amine-boryl radicals enables predictable and site-selective carbon–boron bond formation by targeting the azine’s most activated position, including the challenging sites adjacent to the basic nitrogen atom. This approach enables access to aromatic sites that elude current strategies based on carbon–hydrogen bond activation, and has led to borylated materials that would otherwise be difficult to prepare. We have applied this process to the introduction of amine-borane functionalities to complex and industrially relevant products. The diversification of the borylated azine products by mainstream cross-coupling technologies establishes aromatic amino-boranes as a powerful class of building blocks for chemical synthesis.

通常引入硼官能团来代替芳族碳氢键，以通过分子片段的偶联^1,2,3加快小分子的多样化。当前基于过渡金属催化的碳氢键活化的方法对许多（杂）芳族衍生物的硼化反应有效^4,5但对吖嗪（含氮芳族杂环化合物）的适用范围有限，后者是许多化合物的关键组分医药及农化产品⁶．^{在这里，我们报告了一种使用稳定且廉价的胺-硼烷7}试剂的吖嗪硼酸化策略。光催化将这些低分子量材料转化为高反应性硼自由基⁸对吖嗪结构单元进行有效添加。这种反应性为sp ²碳-硼键组装提供了一种机械替代策略，其中过渡金属介导的碳-氢键活化和吖嗪-有机金属中间体的还原消除的基本步骤被直接的 Minisci ^9取代式，激进加法。胺-硼基的强亲核特性通过靶向吖嗪最活跃的位置，包括与碱性氮原子相邻的具有挑战性的位点，实现了可预测和位点选择性的碳-硼键形成。这种方法可以访问避开当前基于碳氢键激活的策略的芳香位点，并导致难以制备的硼化材料。我们已将此过程应用于将胺-硼烷功能引入到复杂的工业相关产品中。通过主流交叉偶联技术使硼化吖嗪产品多样化，使芳香族氨基硼烷成为化学合成的一类强大的构建单元。