C–H annulations at N- and C2-aryls of an imidazole have been researched well, while the annulation on C4(5)-aryls especially the reactivity and site-selectivity among these aryls remains unknown. Herein, a molecular engineering strategy involving six reaction modes based on the rhodium-catalyzed C4(5)_aryl–H activation/annulation of imidazoles with alkynes has been developed, giving diverse neutral/cationic N-heterocycles with broad scope (>60 examples) and high selectivity. More importantly, through a series of intramolecular competition experiments and DFT calculations, the reactivity of the peripheral C–H bonds has been studied and ranked for the first time: C2_aryl–H > C4(5)_aryl–H > C4(5)_styryl–H/C2_styryl–H > residual C4(5)_aryl–H/C4(5)_styryl–H. Furthermore, the remote bulky C2-subsituent is found to have a big influence on the regioselectivity of C4(5)_aryl–H activation.

中文翻译：

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铑催化的 C4(5) 芳基-H 活化/咪唑与炔烃环化的实验和计算研究：六种 N-杂环的简便合成

咪唑的 N- 和 C2-芳基上的 C–H 环化已得到很好的研究，而 C4(5)-芳基上的环​​化，尤其是这些芳基之间的反应性和位点选择性仍然未知。在此，基于铑催化的 C4(5)_芳基-H 活化/咪唑与炔烃的环化，开发了一种涉及六种反应模式的分子工程策略，提供了多种具有广泛范围的中性/阳离子 N-杂环化合物（> 60 个例子）和高选择性。更重要的是，通过一系列分子内竞争实验和DFT计算，首次研究了外围C-H键的反应性，并排序为：C2 _aryl –H > C4(5) _aryl –H > C4(5)_苯乙烯基–H/C2_苯乙烯基–H > 残留的 C4(5)_芳基–H/C4(5)_苯乙烯基–H。此外，发现远程庞大的 C2-取代基对 C4(5)_芳基-H 活化的区域选择性有很大影响。