Oxidize Amines to Nitrile Oxides: One Type of Amine Oxidation and Its Application to Directly Construct Isoxazoles and Isoxazolines
作者:Xiao-Wei Zhang、Xiao-Lin He、Nan Yan、Hong-Xing Zheng、Xiang-Guo Hu
DOI:10.1021/acs.joc.0c02281
日期:2020.12.4
A facile oxidative heterocyclization of commercially available amines and tert-butyl nitrite with alkynes or alkenes leading to isoxazoles or isoxazolines is described. The unprecedented strategy of the oxidation of an amine directly to a nitrile oxide was used in this cyclization process. This reaction is highly efficient, regiospecific, operationally simple, mild, and tolerant of a variety of functional
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。
A Facile Approach to the Synthesis of 3-Acylisoxazole Derivatives with Reusable Solid Acid Catalysts
gel-supported sodium hydrogen sulfate (NaHSO4/SiO2) or Amberlyst 15 as solid acid catalyst, and then the corresponding 3-acylisoxaszoles were obtained by reacting with alkynes via the 1,3-dipolar [3+2] cycloaddition. These heterogeneous catalysts are easily separable from the reaction mixture and reused. This synthetic method provides a facile, efficient, and reusable production of 3-acylisoxazoles.
accomplished. This chemistry is operative under the cooperative catalysis of cupric oxide nanoparticles (<50 nm) and DABCO. The key beneficial aspects of this protocol include: (i) broad substrate scope, (ii) no vigorous work-up, (iii) short reaction time, (iv) solvent-free condition, (v) commercial viability of substrates/reagents (vi) good chemical yields and selectivity. The other merit of this chemistry
Aromatic and aliphatic nitrile oxides are generated by the oxidation of α-hydroxyimino carboxylic acid with ammoniumhexanitratocerate(IV). They react with olefinic and acetylenic dipolarophiles to give the corresponding cycloaddition products in good yield. The oxidation of α-oxo aldoximes also affords α-oxo carbonitrile oxides.