【作者】 刘颖；

【导师】 郑轶莹； 张景萍；

【作者基本信息】 东北师范大学 ， 物理化学， 2016， 硕士

【摘要】 绿色催化剂的设计和开发是合成化学的热点研究领域。计算化学作为反应机理研究中的重要手段,能够模拟催化剂的作用及存在形式,同时可得到实验上观测不到的过渡态结构和热力学参数。本文采用Gaussian09程序和量子化学计算方法对有机小分子催化碳-碳偶联合成反应机理进行研究,深入探究了反应条件特别是不同催化剂对机理影响差异的根源,进而实现新颖催化剂的设计和开发。主要研究内容如下:1.利用PBE0/6-311+G**//PBE0/6-31G**研究了无催化、自催化、以及水催化条件下的异吲哚啉-1酮衍生物合成的反应机理。基于底物2-羧基苯甲酸(1),(4-甲氧基苯基)甲胺(2),吲哚(3)反应顺序的不同,探究了两种反应机理M1和M2。M1:底物2先与3反应,M2:底物2先与1反应。计算结果表明M1优于M2,且水催化的路径P1最合理。P1经历协同亲核加成和氢转移、亲核进攻和脱水,及分子内环化和脱水三个过程,其决速步骤为第二步亲核进攻和脱水。此外,还探究了决速步中底物2上氮原子分别亲核进攻中间体羰基碳和羧基碳位点的反应活性差异。这两个位点的能垒差归因于非共价相互作用,前线分子轨道分析和NBO分析进一步证实。我们发现水不仅作溶剂,还作为高效的催化剂、质子传递体、和稳定体,通过π…H-O,O…H-N,O…H-C,和O…H-O氢键相互作用稳定过渡态和中间体结构。研究结果帮助实验研究者深入理解水相催化和带有苄胺基团的底物对反应机理和合成路径的影响,为进一步设计该类反应提供理论指导。2.采用 B3LYP/(Br,lanl2dz;其他原子,6-311+G**)//B3LYP/(Br,lanl2dz;其他原子,6-31G*)计算了芳基卤化物和芳烃的交叉偶联反应机理。发现自由基机理优于复分解反应机理。自由基机理分为三个步骤,第一步为叔丁醇钾拔溴得到苯甲醚自由基,第二步是自由基物种与芳烃加成得到环己二烯自由基,随后经历单电子转移和质子迁移得到产物。研究发现叔丁醇钾在整个反应中作自由基引发剂和稳定剂。在理论层面为叔丁醇钾催化C-C键偶联提供指导。更多还原

【Abstract】 The design and development of green catalyst have attracted increasing interest in synthetic chemistry.Computational chemistry is an important tool that uses computer simulation to investigate roles and forms of catalysts as well as to obtain the structures and activation parameters.In this work,we employed Gaussian09 software and quantum chemistry methods to study the mechanisms of organocatalyst catalyzed the carbon-carbon formation reactions,especially deeper understanding for the effect of reaction conditions on the mechanism and the catalytic origin of the different catalysts to achieve the development of novel catalyst.The research contains two parts,shown as following.The mechanisms on the synthesis of 2-substituted-3-(1H-indol-3-yl)-isoindolin-1-one derivatives have been investigated with the PBEO/6-311+G**//PBEO/6-31G**method under unassisted,self-assisted,and water-assisted conditions.Two different mechanisms,M1 and M2 have been studied by DFT calculations,differing in the reaction sequence of substrates 1 with 2 or 3,and M1 is the more favored one.Our calculations also suggest that water-assisted pathway P1W is the most favorable one,which undergoes concerted nucleophilic addition and H-shift,nucleophilic addition and water elimination,and intramolecular cyclization and water elimination.The rate-determining step is the nucleophilic attack and water elimination.Moreover,we also explored the effect of nucleophilic attack of the nitrogen of(4-methoxyphenyl)methanamine on hydroxyl or carbonyl group carbon of phthalaldehydic acid on the activation energy of the rate-determining step.The difference between these two attacking sites is ascribed to the non-covalent interactions,which is further confirmed by the frontier molecular orbital and NBO analyses.We found that water molecules play a critical role in the whole reaction,not only act as solvent but also as an efficient catalyst,proton shuttle,and stabilizer to stabilize the structures of transition states and intermediates viaπ…H-O,O…H-N,O…H-C,and O…H-O interactions.This investigation contributes significantly to our understanding the effect of aqueous catalysis and substrates with-NH2 group on the mechanism and the synthetic routes,which provides a theoretical basis for further designing reactions.The B3LYP/6-311+G**(Br:Lanl2dz)//B3LYP/6-31G*(Br:Lanl2dz)method was carried out to investigate the mechanism of the cross coupling reaction of aryl halides and benzene.Radical mechanism and double decomposition mechanism was proposed,and the former is the most favorable one.The radical mechanism contains three steps,bromine benzyl ether radical generated firstly by t-BuOK,which combines with benzene to form cyclohexadienyl radical,then followed by a single electron oxidation and deprotonation by t-BuO-to get target product and t-BuOH.In addition,we found that t-BuOK acts as radical initiator and stabilizer in the radical reaction processes,which provides a guidance of theoretical research in the t-BuOH-catalyzed cross coupling reaction of C-C bond formation.更多还原