Palladium-catalyzed coupling of N-tosylhydrazones and β-bromostyrene derivatives: new approach to 2H-chromenes
作者:Yamu Xia、Ying Xia、Yan Zhang、Jianbo Wang
DOI:10.1039/c4ob01979b
日期:——
structural motif that exists in natural products and non-natural compounds possessing interesting biological activities. In this investigation, a highly efficient approach toward 2H-chromenes has been developed based on palladium-catalyzedcoupling of N-tosylhydrazones and β-bromostyrenes. The mechanism of this reaction is proposed that involves the formation of vinyl palladium by carbene migratory insertion
2 H -Chromene是存在于天然产物和具有有趣生物活性的非天然化合物中的重要结构基序。在这项研究中,基于钯催化的N-甲苯磺酰hydr和β-溴苯乙烯的偶联,已经开发出一种高效的2 H-苯甲基苯胺的方法。提出了该反应的机理,该机理涉及通过卡宾迁移插入和分子内亲核取代形成乙烯基钯。
Homodimerization of 2<i>H</i>-chromenes catalyzed by Brønsted-acid derived UiO-66 MOFs
Brønsted acid UiO-66 MOFs were prepared for the efficient homo-dimerization of 2H-chromenes, which involves a tandem rearrangement/hetero-Diels–Alder reaction sequence.
SEM, XRD, FTIR, BET and TGA. An efficient and diastereoselective homo-dimerization of 2H-chromenes catalysis was achieved using the sulfonyl derived MIL-101 MOF as a catalyst. A benzopyranobenzopyran polycyclic structure was generated in high yield and diastereoselectivity under mild catalytic reaction conditions. Furthermore, a regio-isomer was observed when 2H-chromene bears different substitution
A Facile Synthesis of 2H-Chromenes and 9-Functionalized Phenanthrenes through Reactions between α,β-Unsaturated Compounds and Arynes
作者:Tiexin Zhang、Xian Huang、and Luling Wu
DOI:10.1002/ejoc.201200042
日期:2012.6
Facile syntheses of 2H-chromenes or 9-functionalizedphenanthrenes under mild conditions in moderate to good yields have been developed. They each involve annulations of arynes with α,β-unsaturatedcompounds bearing different electron-withdrawing groups (EWGs). Depending on the natures of the different EWGs, the reactions proceed by different pathways: enals react with arynesthrough a tandem [2+2]
作者:Nanda D. Paul、Sutanuva Mandal、Matthias Otte、Xin Cui、X. Peter Zhang、Bas de Bruin
DOI:10.1021/ja4111336
日期:2014.1.22
Cobalt(III)-carbene radicals, generated through metalloradical activation of salicyl N-tosylhydrazones by cobalt(II) complexes of porphyrins, readily undergo radical addition to terminal alkynes to produce salicyl-vinyl radical intermediates. Subsequent hydrogen atom transfer (HAT) from the hydroxy group of the salicyl moiety to the vinyl radical leads to the formation of 2H-chromenes. The Co(II)-catalyzed
钴(III)-卡宾自由基是通过卟啉钴(II)配合物对水杨基N-甲苯磺酰腙进行金属自由基活化而产生的,很容易与末端炔进行自由基加成,产生水杨基-乙烯基自由基中间体。随后氢原子从水杨基部分的羟基转移(HAT)至乙烯基,导致2H-色烯的形成。Co(II) 催化的过程可以耐受各种取代模式,并以良好的分离收率生产相应的 2H-色烯产物。EPR 光谱和 TEMPO 自由基捕获实验与所提出的自由基机制一致。DFT 计算揭示了通过金属自由基介导的过程形成水杨基-乙烯基自由基中间体。出乎意料的是,随后从羟基部分到乙烯基的 HAT 导致形成邻醌甲基化物中间体,该中间体自发地从钴中心解离,并很容易进行环内、σ 闭环反应,形成最终的 2H-色烯产物。