Site-selective functionalization of the heterobenzylic C(sp³)–H bonds of pyridines and related heteroaromatic compounds presents challenges associated with the basic nitrogen atom and the variable reactivity among different positions on the heteroaromatic ring. Methods for functionalization of 2- and 4-alkylpyridines are increasingly available through polar pathways that leverage resonance stabilization of charge buildup at these positions. In contrast, functionalization of 3-alkylpyridines is largely inaccessible. Here, we report a photochemically promoted method for chlorination of non-resonant heterobenzylic C(sp³)-H sites in 3-alkylpyridines and related alkylheteroaromatics. Density functional theory calculations show that the optimal reactivity reflects a balance between the energetics of the two radical-chain propagation steps, with the preferred reagent consisting of an N-chlorosulfonamide. The operationally simple chlorination protocol enables access to heterobenzylic chlorides, which serve as versatile intermediates in C–H cross-coupling reactions between heteroaromatic building blocks and diverse oxidatively sensitive nucleophiles using high-throughput experimentation.

^{吡啶和相关杂芳族化合物的杂苄基 C(sp 3} )–H 键的位点选择性官能化提出了与碱性氮原子和杂芳环上不同位置之间的可变反应性相关的挑战。 2-和4-烷基吡啶的功能化方法越来越多地通过利用这些位置上电荷积累的共振稳定性的极性途径获得。相比之下，3-烷基吡啶的官能化基本上是难以实现的。在这里，我们报道了一种光化学促进的方法，用于 3-烷基吡啶和相关烷基杂芳烃中非共振杂苄基 C(sp ³ )-H 位点的氯化。密度泛函理论计算表明，最佳反应性反映了两个自由基链增长步骤的能量之间的平衡，优选试剂由 N-氯磺酰胺组成。操作简单的氯化方案能够获得杂苄基氯化物，它可作为杂芳族结构单元和各种氧化敏感亲核试剂之间的 C-H 交叉偶联反应的多功能中间体，通过高通量实验进行。