Divergent Synthesis of 1 H ‐Indazoles and 1 H ‐Pyrazoles from Hydrazones via Iodine‐Mediated Intramolecular Aryl and sp 3 C–H Amination

作者：Wei Wei, Zhen Wang, Xikang Yang, Wenquan Yu, Junbiao Chang · 发表于：Advanced Synthesis & Catalysis · 年份：2017 · DOI：10.1002/adsc.201700824 · 被引用次数：40 · 研究领域：Catalytic C–H Functionalization Methods、Synthesis and Catalytic Reactions、Synthesis and Biological Evaluation

Abstract A divergent intramolecular C–H amination of hydrazones has been developed employing molecular iodine (I 2 ) as the sole oxidant. The required hydrazone substrates were readily obtained by condensation of hydrazines with the corresponding ketones. In the presence of potassium iodide, I 2 ‐mediated oxidative cyclization of diaryl and tert ‐butyl aryl ketone hydrazones produced 1 H ‐indazoles via direct aryl C–H amination. Under similar reaction conditions, primary and secondary alkyl ketone hydrazones were transformed into 1 H ‐pyrazole products in a reaction involving sp 3 C–H amination. This synthetic methodology does not involve transition metals, and is operationally simple, providing a facile access to indazole and pyrazole derivatives in an efficient and scalable fashion. magnified image