The regioselective, direct alkylation of electron-deficient N-heteroarenes is, in principle, a powerful and efficient way of accessing alkylated N-heteroarenes that are important core structures of many biologically active compounds and pharmaceutical agents. Herein, we report a ZnMe2-promoted, direct C2- or C4-selective primary and secondary alkylation of pyridines and quinolines using 1,1-diborylalkanes as alkylation sources. While substituted pyridines and quinolines exclusively afford C2-alkylated products, simple pyridine delivers C4-alkylated pyridine with excellent regioselectivity. The reaction scope is remarkably broad, and a range of C2- or C4-alkylated electron-deficient N-heteroarenes are obtained in good yields. Experimental and computational mechanistic studies implicate that ZnMe2 serves not only as an activator of 1,1-diborylalkanes to generate (α-borylalkyl)methylalkoxy zincate, which acts as a Lewis acid to bind to the nitrogen atom of the heterocycles and controls the regioselectivity, but also as an oxidant for rearomatizing the dihydro-N-heteroarene intermediates to release the product.

中文翻译：

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ZnMe2 介导的缺电子 N-杂芳烃与 1,1-二硼烷烃的直接烷基化：范围和机制

缺电子 N-杂芳烃的区域选择性直接烷基化原则上是获取烷基化 N-杂芳烃的一种强大而有效的方法，烷基化 N-杂芳烃是许多生物活性化合物和药物的重要核心结构。在此，我们报告了使用 1,1-二硼烷烃作为烷基化源的 ZnMe2 促进的直接 C2 或 C4 选择性初级和二级烷基化吡啶和喹啉。虽然取代的吡啶和喹啉仅提供 C2 烷基化产物，但简单的吡啶提供具有出色区域选择性的 C4 烷基化吡啶。反应范围非常广泛，以良好的收率获得了一系列C2-或C4-烷基化缺电子N-杂芳烃。实验和计算机制研究表明 ZnMe2 不仅可以作为 1 的活化剂，