无金属参与的二乙酸碘苯促进吲哚C3—H乙酸化反应

研究了无金属参与的二乙酸碘苯和吲哚的C3—H乙酸化反应, 通过对取代基效应、 温度以及二乙酸碘苯用量等因素的考察, 建立了反应的最佳条件: 反应温度60 ℃, 乙酸(HOAc)为溶剂. 在无需任何添加剂条件下, 以中等到良好的收率获得一系列C3位乙酸化的吲哚衍生物. 采用红外光谱、 核磁共振波谱、 高分辨质谱及X射线单晶衍射分析对目标化合物进行了结构表征, 并推测了可能的反应机理. 该催化体系对于克量级规模反应均能获得很好的结果.

Metal-free C3—H Acetoxylation of Indoles Promoted by PhI(OAc)2†

3-Substituted indoles are common structural motifs in a series of natural products, pharmaceuticals and biologically active compounds. Metal-free reaction was emerged as one of the most powerful tools for functionalization of indoles due to its environment friendly features. In this work, the metal-free C3—H acetoxylation of indoles and PhI(OAc)₂ was developed. The optimized reaction conditions were established by examination of the substituent, temperature and amounts of PhI(OAc)₂. A series of 3-acetoxyindoles could be obtained in HOAc at 60 ℃ without additives. The yield of product ranged from 45% to 86%. The structures were characterized by infrared(IR), nuclear magnetion resonance(NMR), high resolution mass spectra(HRMS) and X-ray diffraction techniques and a possible reaction mechanism was then proposed. Moreover, this reaction system was also feasible in a gram-scale reaction without significant decrease in the product yields.