Application of silica gel-supported polyphosphoric acid (PPA/SiO2) as a reusable solid acid catalyst to the synthesis of 3-benzoylisoxazoles and isoxazolines
3-Benzoylisoxazoles were synthesized by the reaction of alkynes and benzoylnitromethane using silica gel-supported polyphosphoric acid (PPA/SiO2). This reaction provides a convenient, efficient, and reusable synthetic method of isoxazole derivatives. (C) 2011 Elsevier Ltd. All rights reserved.
Competitive Copper Catalysis in the Condensation of Primary Nitro Compounds with Terminal Alkynes: Synthesis of Isoxazoles
作者:Ausilia Baglieri、Luca Meschisi、Francesco De Sarlo、Fabrizio Machetti
DOI:10.1002/ejoc.201600897
日期:2016.9
are prepared by catalytic condensation of primary nitro compounds with terminalacetylenes by using a copper/base catalytic system. The additional catalytic effect of the copper(II) salts is evidenced by comparing the kinetic profiles. Selectivity dependence on reaction conditions is considered for phenylacetylene in the following competitive processes: oxidative coupling of terminal alkynes to conjugated
异恶唑,主要是 3,5-二取代,是通过使用铜/碱催化系统将伯硝基化合物与末端乙炔催化缩合制备的。通过比较动力学曲线证明了铜 (II) 盐的额外催化作用。在以下竞争过程中,苯乙炔的选择性取决于反应条件:在空气存在下,由 CuII 和碱催化的末端炔烃与共轭二炔的氧化偶联;除了与苯甲酰硝基甲烷缩合生成 3-苯甲酰异恶唑外,还生产呋喃,这是亲偶极试剂与 3,4-二苯甲酰呋喃反应的结果;将缺电子炔烃(例如丙炔酸甲酯)与自身和硝基化合物加成。因此,氧化偶联在与“活性”硝基化合物的反应中可以忽略不计,而对于硝基烷烃,可以观察到两种产物:仅检测到痕量的异恶唑,而没有铜。类似地,在铜存在下,3-苯甲酰基-5-苯基异恶唑比呋喃唑占优势。此外,在单独存在碱的情况下,缺电子炔烃的缩合会产生复杂的反应混合物,但环加合物可以方便地用铜制备。结果表明该催化方法在合成实践中的实用性和普遍性。但环加合物可以方便地用铜制备。