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Theoretical Study of Metal Carbenoid Promoted Cyclopropanation Reactions with Ethylene and the Effect of THF Solvent on the Reaction Pathways

Author: ZhangXingHui
Tutor: GengZhiYuan
School: Northwest Normal University
Course: Inorganic Chemistry
Keywords: Carbenoid Cyclopropanation Solvation effect Transition state theory Inorganic Chemistry Metallization Methylene Theoretical study Graduate Master
CLC: O621.2
Type: Master's thesis
Year: 2006
Downloads: 160
Quote: 1
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Abstract


Contains many natural and non-natural products cyclopropyl have biological activity, but also a large number of such compounds are used as organic synthetic materials and intermediates. Therefore, the experimental chemists have been committed to exploring new ways and means of preparation cyclopropanation product. The Simmons-Smith reaction was the first time in 1958 by Simmons and Smith, it is by zinc carbenoid (referred to as SS reagent) and the olefin synthetic cyclopropanation product method. Chemists are then focused on the selection and preparation of the Simmons-Smith reagent to obtain with good stereoselectivity and higher yields of the active agent. In this regard, but relative to a Simmons-Smith type of metal carbenoid olefin cyclopropanation reactions Experimental Theoretical study is relatively small, and is mainly composed of Li, Zn, etc. metal carbene with an olefin ring The cyclopropanation reactions on. The selected system (Cu and Sm reaction with ethylene) to conduct intensive research, get some meaningful conclusions. In this paper, based on the theory of molecular orbital theory, transition state theory and quantum mechanics, the use of density functional theory (DFT), perturbation theory (MPn), coupled cluster method (CCSD (T)), the time-dependent density functional theory ( TD-DFT) and natural bond orbital (NBO) analysis method, the coordinate system to select suitable research and the basis set by calculating the optimized geometries to find out the reaction of various species (including transition state), then the potential energy of the system surface, spectral data, thermodynamic data and track relevant information. We use these data, comprehensive analysis of the reaction mechanism. Provides a theoretical basis for further experimental studies. The paper is divided into seven chapters. Chapter metal carbenoid research progress and promote olefin cyclopropanation this paper work. The second chapter outlines the work in this article quantum chemical theoretical background and the calculation method. The first two chapters are mainly summarizes the theoretical background and theoretical basis of this work, our study provides a reliable quantum chemical methods. Chapters III and IV of the density functional B3LYP method to study the the cyclopropanation reaction mechanism of the transition metal samarium carbenoid with ethylene. 3 SmCH 2 X (where X = Cl, Br and I), respectively and CH 2 CH three different samarium SS reagent CH 2 reaction of reactants, intermediates, transition states and product configuration of the entire structure of the geometric parameters were optimized using the intrinsic reaction coordinate (IRC) calculation and frequency analysis method, transition states verified. The results showed that: CH 3 SmCH 2 X (where X = Cl, Br and I) with CH 2 CH 2 cyclopropane reaction can be carried out by methylene transfer channel and carbene metal channels, the same as the reaction mechanism with lithium carbenoid methylene transfer channel only reaction was carried out more easily, carbene substituent halogen atom heavier reaction becomes easy. Select samarium carbenoid CH 3 SmCH 2 I study and the CH 2 CH 2 reaction, and calculated The effect of solvent in the THF solution, the solvation effect the carbene metal channel Shakespeare methyl transfer channel of the reaction barrier greatly improved, more conducive to the the methylene transfer channel of the reaction, not conducive carbene metal channel. And this reaction is carried out at a lower temperature can occur. Chapter V in order to further study the mechanism of samarium class carbene cyclopropanation density functional B3LYP method the the samarium carbenoid reagent ClSmCH 2 Cl study, there are two possible responses with ethylene Channel: methylene transfer channel, and carbene metal channel. The calculation results show that samarium class the carbene ClSmCH 2 Cl than the corresponding zinc carbenoid strong electron affinity and higher chemical activity, the ligand more THF molecule makes the methylene transfer channel reaction barrier is relatively low, however, consider the effect of solvation reaction barrier of the carbene metal channel increased from 44.71 kJ · mol -1 to 63.62 kJ · mol -1 , is more conducive to the reaction along methylene transfer channel. Chapter VI studied using the density functional B3LYP method the cyclopropanation reaction mechanism of the transition metal copper carbenoid with ethylene. Three different copper SS reagent CH / sub> CuCHCl, 2 ClCuCH 2 the Cl \u0026 CH 3 CuCHI 2 and CH 2 CH 2 reaction of the reactants, intermediates, transition states, and product configuration structure geometric parameters were optimized intrinsic reaction coordinate (IRC) calculation and frequency analysis method, transition states were identified and validated. The results show that: the CH 3 CuCHCl 2 and CH 3 / sub> CuCHI, 2 the CH 2 CH 2 methylene transfer mechanism and carbene metal mechanism can be the same as the reaction mechanism of lithium carbenoid cyclopropanation reactions; while the ClCuCH 2 Cl and CH 2 CH 2 cyclopropanation reaction is easier carbene metal mechanism. Chapter VII of ab initio molecular orbital theory G2MP2 carbenoid CF 3 , optimized four different equilibrium configuration of the transition state structure into each other; given geometry parameters, the symmetry of the configuration, dipole moment, the total energy of the configuration, and the frontier molecular orbital energy, and at the same time the vibration frequency analysis calculations of the transition state, and determine if they are only virtual vibration mode, and then the characteristics of each configuration, compare their stability, and the class discussed the chemical nature of the carbene.

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CLC: > Mathematical sciences and chemical > Chemistry > Organic Chemistry > Organic Chemistry general issues > Properties of organic compounds
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