3-羟基哒嗪及其CH3,NO2和CI取代衍生物质子转移过程的理论研究

用密度泛函理论(DFT)B3LYP方法,在6-311+G*基组下,对3-羟基哒嗪及其CH3,NO2和Cl取代衍生物分子醇式和酮式结构互变异构化反应进行了研究,优化化合物的几何构型,寻找反应的过渡态,通过振动分析和内禀反应坐标(IRC)分析加以证实,计算了反应的活化能.结果表明,3(2H)-哒嗪酮及其带取代基的衍生物不论是单体,还是相对应的二聚体,比其相对应的异构体能量低,表明在通常情况下是以3(2H)-哒嗪酮及其衍生物形式稳定存在的,这与前人通过实验数据对3-羟基哒嗪互变异构体的比率进行预测的结果是一致的.根据计算结果讨论了异构化反应的机理.     

3-羟基哒嗪及其CH3, NO2和Cl取代衍生物质子转移过程的理论研究

用密度泛函理论(DFT) B3LYP方法, 在6-311＋G*基组下, 对3-羟基哒嗪及其CH₃, NO₂和Cl取代衍生物分子醇式和酮式结构互变异构化反应进行了研究, 优化化合物的几何构型, 寻找反应的过渡态, 通过振动分析和内禀反应坐标(IRC)分析加以证实, 计算了反应的活化能. 结果表明, 3(2H)-哒嗪酮及其带取代基的衍生物不论是单体, 还是相对应的二聚体, 比其相对应的异构体能量低, 表明在通常情况下是以3(2H)-哒嗪酮及其衍生物形式稳定存在的, 这与前人通过实验数据对3-羟基哒嗪互变异构体的比率进行预测的结果是一致的. 根据计算结果讨论了异构化反应的机理.     

3,6-二羟基哒嗪质子转移过程的理论研究

为了探索3,6-二羟基哒嗪分子醇式和酮式结构互变异构化的反应机理,本研究组采用DFT B3LYP/6-311+G(d)方法对标题化合物异构化反应的势能面进行了研究,在探讨各种可能的反应途径中,发现至少有34种异构体和43种过渡态.结果表明,6-羟基-3(2H)-哒嗪酮不论是单体,与水形成配合物,还是二聚体,比其相对应的异构体能量低,表明在通常情况下是以6-羟基-3(2H)-哒嗪酮形式稳定存在的,这与前人通过实验数据对互变异构体的比率进行预测的结果是一致的;在考察的可能反应途径中,直接进行的分子内质子转移过程需要的活化能为142.2 kJ·mol^-1,水助催化时,反应活化能为41.3 kJ·mol^-1,考虑溶剂效应后,其活化能为59.2 kJ·mol^-1,二聚体双质子转移的活化能为16.8 kJ·mol^-1,二聚体双质子转移所需活化能最低,在室温下就可以进行.由此可见氢键在降低反应活化能方面起着重要的作用.     

4-氟-3-羟基-1-取代苯基-6-哒嗪酮及其衍生物的合成

报导4-氟-3-羟基-1-取代苯基-6-哒嗪酮及其衍生物的合成,氟代顺丁烯二酸酐和取代苯肼类反应的研究结果及部分化合物的药理实验结果。     

4-卤-5-(4-甲基-2H-1-苯并-2-吡喃酮-7-氧基)-2-取代-3(2H)-哒嗪酮衍生物的合成和生物活性研究

通过4,5-二氯(溴)-3(2H)-哒嗪酮与7-羟基-4-甲基香豆素在CH3CN/K2CO3体系下的缩合反应,将具有生物活性的哒嗪酮环引入到苯并吡喃酮结构中,设计、合成了9个含哒嗪酮环的香豆素类化合物,其中8个为新化合物.所有化合物的结构均经NMR,MS和元素分析确证.初步生物活性测试结果表明:化合物4-氯-5-(4-甲基-2H-1-苯并吡喃-2-酮-7-氧基)-2-(4-硝基苯基)-3(2H)-哒嗪酮对黄瓜根部具有一定的抑制作用.     

3-亚甲基异苯并呋喃-1(3H)-酮及其衍生物的合成研究

以2-乙烯基苯甲酸甲酯及其衍生物为原料,经过酯水解反应,随后发生环氧化、环合反应制备了3-羟甲基异苯并呋喃-1(3H)-酮及其衍生物;再和三溴化磷或者对甲苯磺酰氯发生亲核取代,最后通过消除反应合成了3-亚甲基异苯并呋喃-1(3H)-酮及其衍生物.在亲核取代和消除反应中,对甲苯磺酰氯法比三溴化磷法产率高.目标产物及其中间体有10个是新化合物.化合物结构用1H NMR,13C NMR,MS和IR表征.目标产物在空气中长期放置没有发生二聚.     

3-亚甲基异苯并呋喃-1(3H)-酮及其衍生物合成新方法

报道了3-亚甲基异苯并呋喃-1(3H)-酮及其衍生物简易、高效的合成方法.其特点是原料易得且价格低廉、反应条件温和、收率高.该方法以2-甲基苯甲酸及其衍生物为原料,经过酯化、自由基溴代和三苯基膦发生亲核取代反应合成了2-[(溴三苯基正膦基)甲基]苯甲酸甲酯及其衍生物;随后发生Wittig反应、羧酸酯碱性条件下水解得到2-乙烯基苯甲酸及其衍生物;接着和碘(NBS)发生环合反应,生成3-碘(溴)甲基异苯并呋喃-1(3H)-酮及其衍生物;最后消除卤化氢得到目标化合物.     

1-取代-1,4,5,6-四氢(及1,6-二氢)-6-哒嗪酮-3-酰肼衍生物的合成

哒嗪类化合物具有抗原虫,抗鞭毛虫及阿巴米等多种药理活性,一些6-芳基-4,5-3(2H)哒嗪酮具有抗高血压,利尿及中枢神经抑制作用[1],并且哒嗪类化合物在农药方面也有广泛的应用[2].另外酰氨基硫脲及其衍生物具有广谱的抗菌和杀虫作用.本文以α-酮戊二酸和水合肼为起始原料,合成哒嗪酰肼[3],将其酰肼与糖基异硫氰酸酯或芳香烃异硫氰酸酯反应,合成哒嗪酮酰氨基硫脲及衍生物.其药理活性有待测试.     

离子液体中碘催化下2-氨基苯甲酰肼和4-氧代庚二酸的反应研究

研究了以2-氨基苯甲酰肼和4-氧代庚二酸为原料,以离子液体为绿色溶剂,在碘催化下进行的反应.结果显示,当酰肼中与酰胺基相连上的N原子没有取代基时,会顺利构建三个新环生成哒嗪并[6,1-b]吡咯并[1,2-a]喹唑啉-1,6,9(7H)-酮衍生物,并通过X单晶衍射分析验证了产物2,3,4,5-四氢化-1H,9H-哒嗪并[6,1-b]吡咯并[1,2-a]喹唑啉1,6,9(7H)-三酮(3a)的结构.而当其取代基是芳基时,由于位阻效应,哒嗪环并没有如期关环,生成四氢吡咯并[1,2-a]喹唑啉-3a(1H)-丙酸衍生物.该方法具有合成路线简洁、溶剂绿色环保、操作简便且收率较高等优点.     

3-亚烷基(亚芳基)异苯并呋喃-1(3H)-酮及其衍生物的合成研究

报道了3-亚烷基(亚芳基)异苯并呋喃-1(3H)-酮及其衍生物的简易而且高效的合成方法.其特点是原料易得、价格低廉、反应条件温和、收率高.该方法以异苯并呋喃-1(3H)-酮(苯酞)及其衍生物为原料,经过自由基溴代合成了3-溴异苯并呋喃-1(3H)-酮及其衍生物,随后与三苯基膦发生亲核取代反应,接着在三乙胺的作用下发生消除反应生成Wittig试剂,最后与脂肪族醛或者芳香族醛发生Wittig反应得到目标化合物.目标产物及其中间体有13个是新化合物.     

Theoretical study of reaction mechanism for CH2CHX(XH,F, Cl) with ozone

In this work, we study the reaction mechanism of the CH₂CHX(X?H, F, Cl) with ozone reactions, using ab initio MP2 method at 6‐311++g** basis set level. The geometric configurations of reactants, intermediates, transition states, and products were optimized, and the energies were obtained at the QCISD(T)/6‐311++G** level. The transition states and intermediates of the reactions were verified by the vibrational analysis. The results show that the ozonolysis of ethylene and its derivatives is reasonable and believable along the Criegee mechanism. The results also show that the activation energies of the controlling steps along the fluoroethylene and chloroethylene with ozone reaction pathways were lower than that along the ethylene with ozone reaction pathway. That is to say, the derivatives of ethylene have the higher activity to react with ozone and deplete the ozone layer. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Density functional theory study on isomerization reactions of pyridazine derivatives bearing N,N‐dialkylaminoethyl group

The isomerization reactions of four pyridazine derivatives, i.e., 6‐chloro‐3‐hydroxy‐pyridazine, 1,2‐dihydrogen‐1‐methyl‐3,6‐pyridazindione, 6‐chloro‐3‐diethylamino‐ethoxy‐pyridazine, and 1‐methyl‐2‐diethylaminoethyl‐3,6(2H)‐pyridazindione, have been studied using density functional theory (DFT) B3LYP method at the 6‐311+G** basis set. The geometric structures of reactants, transition states and products have been optimized. The transition states have been explored and proved by vibration analysis as well as intrinsic reaction coordination (IRC) analysis. The activation energies of four reactions were calculated, and the corresponding isomerization mechanisms were also elucidated in theory. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004     

Computational study on the structures of the [H, Si, N, C, O] isomers: possible species of interstellar interest

Ab initio methods have been used to study the lowest lying [H, Si, N, C, O] isomers, which are of astrochemical interest. Over 20 [H, Si, N, C, O] isomers in the 1A' electronic state have been investigated at the MP2/aug-cc-pVTZ level of theory. Of these, the seven lowest isomers have been further investigated using different levels of theory, including B3LYP and QCISD(T). It has been found that the relative energies of the isomers in their ground electronic state (1A') are very dependent on the level of theory used with either the cis-HOSiCN or cis-HOSiNC isomers being the lowest in energy. Overall, the four lowest isomers are within 6 kcal/mol of each other, and a further three isomers are less than 15 kcal/mol higher in energy than the lowest lying isomer, including HSiNCO, which has recently been detected spectroscopically. Natural bond analysis has been carried out on the ground electronic states of the seven lowest lying isomers to examine their electronic structure. The enthalpies of formation of the seven lowest isomers have also been evaluated using the G3MP2 and G3B3 multilevel methods and show that the isomers are relatively thermodynamically stable. The structures and energies of lowest lying 1A' and 3A' electronic states of these isomers have also been investigated and show that for most of the isomers the optimized structures in these excited electronic states correspond to a transition state structure.     

A Theoretical Study on the Equilibrium Structures and Relative Stabilities of H_2SO

1INTRODUCTIONTheconformationandvariousphysicalprope-rtiesofdichalcogencompoundsR-X-Y-R?(X,Y=O,S,Se,andTe)havebeenatopicofseveralexperi-mentalandtheoreticalinvestigations[1].CompoundscontainingS=SandS=Obondshavelongbeenpro-posedasintermediatesinorganicsynthesisand,onoccasion,asstableentities[2～18].Despitethecom-monlyusedrepresentationofS–Obondinsulfoxi-desandothersulfinylderivativesasS=O,sulfoxidesareinmanywaysbestdescribedasylideswithhighlypolarizedS–Oσ-bondbecauseofelectro-sta…     

An MO study of regioselective amine addition to ortho-quinones relevant to melanogenesis

Energy profiles for alternative intramolecular cyclisations of 4-(aminoalkyl)-ortho-quinones have been calculated using the AM1 method and ab initio energies of the transition states are determined. In all the cases cyclisation at position 5 occurs via a significantly lower energy transition state than cyclisation at position 3. This is consistent with experimental observations. Optimal trajectories for attack have been determined from a study of the reactions of methylamine with 4-methyl-ortho-quinone. For cyclisation of aminoalkyl derivatives deviation from the optimal direction is less for reaction at position 5 but constraint on angle of attack only partially accounts for the regioselectivity. Intrinsic differences in the electronic energies of the alternative transition states are the main contributor to regioselectivity. The relative energies of transition states can be modified by variation of the substituent at position 4. The calculations suggest that seven-membered ring formation may occur via a boat transition state and steric hindrance in the seven-membered transition states may account for the experimentally observed influence of N-substituents on the mode of reaction.     

硅炔氢加成生成甲硅烷基硅烯的量子化学研究

利用量子化学从头算和密度泛函理论(DFT), 研究了硅炔和氢气分子加成生成甲硅烷基硅烯的反应机理. 在B3LYP/6-311G**水平上, 全参数优化了反应通道上各驻点(反应物、过渡态和产物)的几何构型, 计算出了它们的振动频率和零点振动能(ZPVE), 并对它们进行了振动分析, 以确定过渡态的真实性. 各物质总能量由QCISD(T)/6-311G**// B3LYP/6-311G**给出, 并对能量进行了零点能校正. 计算表明, 硅炔与氢分子加成反应可生成稳定的甲硅烷基硅烯. 热力学与动力学计算表明, 反应过程是一个放热、熵减少而自发趋势和反应程度较大的反应.     

Excited electronic states and photophysics of uracil–water complexes

The electronically excited singlet states of complexes of uracil with one water molecule have been studied theoretically using ab initio multireference configuration interaction methods. In agreement with previous theoretical and experimental results, four cyclic isomers of uracil forming hydrogen bonds with the water molecule have been located with energies within 0.2 eV from the lowest energy isomer. Focus has been given on the mechanism for radiationless decay to the ground state after initial UV absorption and on the effect of complexation with water on previously reported radiationless decay pathways. Features on the excited state potential energy surfaces, such as minima, transition states and conical intersections, have been located for all isomers and compared with those of free uracil. The hydrogen-bonded water molecule changes the relative energies of these features and may lead to different excited state dynamics and lifetimes, in agreement with experimental observations.     

Theoretical Study on Dehydrogenation Reactions of Silanol

The pathway of dehydrogenation reaction of silanol SiH3OH is investigated by ab initio Mo calculations using RHF/-31G basis set. The geometries of reactant, transition states and products are optimized on the singlet potential energy surface of the ground state. The activation energies, reaction heats, statistical A factor and activation entropies are calculated. The vibrational analysis of the reactant and the transition states is made. The reaction crgodography along the intrinsic reaction coordinate (IRC) are performed to examine the reaction mechanism.     

Theoretical study on the ring-opening isomerization reaction mechanism of the ring isomers of N8H8

Ring-opening isomerization from ring-shaped isomers to chain-shaped isomers of N(8)H(8) has been studied by a density function B3LYP method at 6-311+ +G** level. 20 ring-shaped isomers have been found to be able to transform into chain-shaped isomers, with 20 possible transition states got by ring-opening structure optimization. Furthermore, the ring-openings have been found in the longer N-N single bond by analyzing the length change of N-N bond of ring-shaped isomers in ring-opening processes. In addition, with the activation energies in ring-opening processes, the differences of the activation energies in isomerization between the isomers have been found according to the classification of rings. The activation energies in ring-opening isomerization of six-membered ring-shaped isomers are higher than that of the four-membered ring-shaped isomers. It indicates that six-membered ring-shaped isomers difficult in ring-opening in the isomerization are the steadiest ring-shaped isomers of N(8)H(8) while four-membered ring-shaped isomers easy in ring-opening are the most unstable.