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Understanding the stereoselectivity in Bronsted acid catalysed Povarov reactions generating cis/trans CF3-substituted tetrahydroquinolines: a DFT study

机译:了解雄骨酸催化的POVAROV反应的立体选择性,产生顺式/反式CF3取代的四氢喹啉:DFT研究

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摘要

The Bronsted acid (BA) catalysed Povarov reactions of (E)-1-phenyl-N-(4-(trifluoromethyl) phenyl) methanimine with 1-vinylpyrrolidin-2-one (VPO) and with allyltrimethylsilane (ATMS), affording CF3-substituted cis/trans tetrahydroquinoline (THQ) derivatives, have theoretically been studied using the M06-2X functional together with the standard 6-31G(d) basis set. These BA catalysed Povarov reactions are multistep processes initialised by the nucleophilic attack of the non-substituted carbon atom of the nucleophilic ethylene on the imine carbon atom of the super-electrophilic protonated imine, yielding the corresponding cationic intermediate along the endo/exo stereoisomeric approach mode. Upon the formation of the cationic intermediates, a fast intramolecular Friedel-Crafts reaction converts them into the final THQs and the BA catalyst is recovered as well. For the reaction with VPO, the energetic results indicate that the endo stereoisomeric approach mode is kinetically preferred over the exo one. Interestingly, when the ATMS was experimentally used, the trans THQ resulting from an exo approach mode was the major product. A non-covalent interaction (NCI) analysis of the electron-density of the transition state structures involved in the stereoselective-determining step of these BA catalysed Povarov reactions allows an explanation of the endo/exo stereoselectivity experimentally observed.
机译:用1-乙烯基吡咯烷蛋白-2-一(VPO)和烯丙基甲基硅烷(ATMS),刚性酸(BA)催化的POVAROV反应(E)-1-苯基-N-(4-(三氟甲基)苯基)甲沙亚胺,得到烯丙基甲基硅烷(ATM),得到CF3-理论上使用M06-2X功能与标准的6-31G(d)基础集合学理论上研究了取代的顺式/反式四喹啉(THQ)衍生物。这些BA催化的POVAROV反应是由亲核乙烯的未取代的碳原子的亲核碳原子对超亲电泳质子化亚胺的亚胺碳原子的亲核碳原子的多核方法,从而产生沿endo / exo立体异构体方法的相应阳离子中间体。在形成阳离子中间体后,快速的分子内的Friedel-Crafters反应将它们转化为最终的THQs,并且也恢复BA催化剂。对于与VPO的反应,能量结果表明,内部立体异构体方法模式在exo一个上是动力学上优选的。有趣的是,当ATM在实验使用时,由EXO方法模式产生的Trans ThQ是主要产品。非共价相互作用(NCI)分析这些BA催化的POVAROV反应的立体选择性确定步骤中涉及的过渡状态结构的电子密度允许实验观察到的内部/外部立体选择性的解释。

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  • 来源
    《RSC Advances》 |2016年第21期|共10页
  • 作者单位

    Univ Valencia Dept Organ Chem Dr Moliner 50 E-46100 Burjassot Valencia Spain;

    Univ Valencia Dept Organ Chem Dr Moliner 50 E-46100 Burjassot Valencia Spain;

    Islamic Azad Univ Shahrood Branch Chem Dept Shahrood Iran;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化学;
  • 关键词

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