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。
Structurally Diverse α-Substituted Benzopyran Synthesis through a Practical Metal-Free C(sp<sup>3</sup>)–H Functionalization
作者:Wenfang Chen、Zhiyu Xie、Hongbo Zheng、Hongxiang Lou、Lei Liu
DOI:10.1021/ol503004a
日期:2014.11.21
A trityl ion-mediated practical C–H functionalization of a variety of benzopyrans with a wide range of nucleophiles (organoboranes and C–H molecules) at ambient temperature has been disclosed. The metal-free reaction has an excellent functional group tolerance and high chemoselectivity and displays a broad scope with respect to both benzopyran and nucleophile partners, efficiently affording a collection
CAN Interceded Oxidative Coupling of β‐Dicarbonyl Compounds to 2‐Aryl/Heteroarylchromenes: A Regio‐ and Diastereoselective Synthesis of Tetrahydro‐benzofuro[3,2‐<i>c</i>]chromenones
A CAN mediated oxidative coupling of 1,3-dicarbonyl compounds to 2-arylchromenes followed by cyclization affords tetrahydro-benzofuro[3,2-c]chromenones with regio- and diastereoselectivity in high yield.
CAN 介导的 1,3-二羰基化合物与 2-芳基色烯的氧化偶联,然后环化,以高产率提供具有区域和非对映选择性的四氢苯并呋喃并[3,2- c ]色烯酮。