应用量子化学反应性指数研究频哪醇重排反应

1,2-二醇类化合物的频哪醇重排反应是经典的化学重排反应。无环的或环状的1,2-二醇类化合物在质子酸或路易斯酸的作用下会重排发生取代基的1,2-迁移,其产物往往伴随不同基团的迁移而生。但是,主产物取决于二羟基相连接的碳原子上取代基的空间架构和性质。本文采用净亲电指数(Multiphilic index)和Wiberg键级等量子化学反应性指数来定量描述1,2-二醇类化合物的频哪醇重排反应机理,并依此作为预测频哪醇反应主产物的依据。     

频哪醇重排反应的研究进展

频哪醇重排反应是由1,2-二醇在酸催化下发生分子内重排脱水,生成频哪酮的反应。频哪酮是一种重要的有机化工中间体,广泛应用于农药、医学、染料等领域。本文综述了频哪醇重排反应的研究进展,主要包括频哪醇在高温液态水和超临界水中的重排反应;无机酸、路易斯酸和分子筛催化的反应;固相条件下的反应;以及光化学、电化学重排等方面的研究...     

新的烯丙型环氧醇重排还原反应研究

自１９８０年Ｓｈａｒｐｌｅｓｓ［１］报道烯丙醇制备立体选择性烯丙型环氧醇化合物以来,有关烯丙型环氧醇的反应及其在有机合成中的应用研究日益受到重视,其中路易斯酸催化的反应尤为重要［２］．但由路易斯酸催化的反应极少涉及碳骨架的重排或基团的迁移．我们最近在...     

片呐醇电合成的研究

以铝合金为电极在酸性条件下电合成片呐醇, 探讨了电压、反应时间等对产率的影响. 最佳反应条件为: 电解电压为12 V, 反应时间60～80 min, 甲醇和盐酸(36%)用量各5 mL, 片呐醇的产率可达31%～81%.     

叔膦促进下两种亲电试剂之间的环化反应研究进展

发展环状化合物的高效合成方法对药物分子、天然产物及其他功能有机分子的合成具有重要意义.近年来,叔膦促进下两种亲电试剂之间的环化反应,由于具有原料简单易得、反应条件温和、且无需金属参与等优点,同时为多种碳环及杂环化合物的合成提供了高效的新途径,因而受到了合成化学家的广泛关注.这类反应通常经过叔膦对亲电试剂进行亲核加成,产生两性离子活性中间体这一关键步骤来完成.根据两性离子的不同来源,综述了叔膦促进下缺电子联烯、Morita-Baylis-Hillman烯丙基化合物、缺电子烯烃与其他亲电试剂之间的环化反应.     

微波辐射FeCl3催化无溶剂条件下的呐醇重排

通过微波辐射, 以FeCl3为催化剂进行无溶剂条件下的呐醇重排反应, 1 min产率可达86%～96%. 该方法具有操作简便、反应时间缩短、对环境友好等优点.     

微波辐射FeCl3催化无溶剂条件下的[口片]呐醇重排

通过微波辐射,以FeCl3为催化剂进行无溶剂条件下的口片呐醇重排反应,1min产率可达86%～96%.该方法具有操作简便、反应时间缩短、对环境友好等优点.     

碘催化的2-炔基苯胺与二硒醚的亲电环化反应

研究了碘催化的2-炔基苯胺与二硒醚的亲电环化反应. 结果表明, 在碘单质(0.2 mmol)、 2-炔基苯胺(0.2 mmol)、 二硒醚(0.1 mmol)和甲苯(2 mL)共存体系中, 反应温度为110℃时, 2-炔基苯胺与二硒醚能发生亲电环化反应, 生成相应的3-硒取代吲哚化合物, 产率为中等到良好. 该反应在无金属催化的条件下进行, 为合成官能团吲哚提供了一种新途径.     

不对称呐醇偶联反应新进展

综述了近年来不同催化体系的不对称合成呐醇的方法, 并总结了不同的催化效率和对映选择性的差异.     

单重态二碘代乙叉重排反应的AM1方法研究

采用量子化学中的ＡＭ１方法研究了单重态二碘代乙叉重排反应的机理。结果发现,该重排反应经过一个三元环过渡态,反应的能势为２５．８ｋＪ／ｍｏｌ。根据计算结果,详细研究了该反应的热力学及动力学函数,结果表明该反应是放热反应,放出的热量约为２５０ｋＪ／ｍｏｌ;该反应的Ａ因子稍小于１０１３ｓ－１,是典型的单分子反应。由于反应的平衡常数和速度常数都很大,故Ｉ２Ｃ＝Ｃ：一旦生成就立即转变为ＩＣ≡ＣＩ。     

Density Functional Study on the Mechanism of Amadori Rearrangement Reaction

The reaction mechanism of amadori rearrangement in the initial stage of Maillard reaction has been investigated by means of density functional theory calculations in the gaseous phase and aqueous solution.Cyclic ribose and glycine were taken as the model in the amadori rearrangement.Reaction mechanisms have been proposed,and possibility for the formation of different compounds has been evaluated through calculating the relative energy changes for different steps of the reaction by following the total mass balance.The calculations reveal that the amadori rearrangement initialized via the intramolecular rearrangement,transferring one proton from N(3) to O(4) atom.In the next step,the second proton is also transferred from N(3) to O(4) atom,corresponding to the cleavage of C(4)-O(4) bond and the release of one water molecule.Then another proton is transferred from N(3) to C(5) atom via TS3 with the reaction barrier of 58.3 kcal·mol-1 after tunneling the effect correction calculated at the B3LYP/6-31+G(d) level of theory,and this step is rate limiting for the whole catalytic cycle.Ultimately,the product is generated via keto-enolic tautomerization.Present calculation could provide insights into the reaction mechanism of Maillard reaction since experimental evaluation of the role of intermediates in the Maillard reaction is quite complicated.     

Theoretical Study on the Transition State of N-nitropyrazoles Rearrangement Reaction

Theoretical studies on the rearrangement reactions of nitropyrazoles have been investigated. In order to gain a better understanding of the intermediate process of rearrangement reactions, the transition states of the rearrangement reactions were obtained by TS method at the B3 LYP/6-311 G(d, p) level of theory. The natural bond orbital charge, electrostatic potential and frontier molecular orbital of the molecules in the process of rearrangement were analyzed, and the solvent effect was also discussed. The rearrangement of nitropyrazoles involves two transition states and one intermediate, and the nitro group and hydrogen atom are two transfer groups for rearrangement reactions. The migration of these two groups leads to the change of charge distribution and molecular structure. The structural changes of the molecules in different solvents are not significant, but the dipole moment of the molecule has obvious change.     

炔丙氧基硫代磷酸酯在GC毛细管中的重排反应研究

通过芳氧基甲氧基炔丙氧基硫代磷酸酯的GC／MS研究，首次发现了芳氧基甲氧 基快丙氧基硫代磷酸酯在CC毛细管中的重排反应及其重排规律，由此探索出氮气保 护下芳氧基甲氧基丙二烯基硫赶磷酸酯在SiO2载体上新的合成方法．     

单重态H_2N=B:→HNBH重排反应的理论研究

用量子化学中的从头算方法, 在MP2/6-311++G(d,p)水平上研究了单重态H_2N=B→HNBH重排反应的机理。结果表明, 该重排反应经过一个三元环过渡态。根据计算结果，初步讨论了该反应的热力学及动力学函数。     

Ferrier重排反应研究进展

Ferrier重排反应是一种类似于烯丙基重排的反应, 它可以广泛地用来合成2,3-不饱和糖苷. 综述了近年来Ferrier重排反应的研究进展.     

不饱和硼烯HClN=B:重排反应的DFT研究

采用量子化学中的密度泛函方法, 在B3LYP/6-311G**水平上研究了不饱和硼烯HClN=B:的重排反应机理。结果表明, 无论是氢原子H迁移还是氯原子Cl迁移都经过1个三元环过渡态,生成直线型产物。但氢原子H迁移是在面内进行, 而氯原子Cl迁移是在面外进行。根据计算结果,详细研究了不饱和硼烯HClN=B:重排反应的热力学及动力学函数, 在此基础上讨论了不饱和硼烯HClN=B:的存在寿命问题。     

叶绿素-a及其衍生物的Qy轴向氧化反应和E-环重排反应

在酸碱性条件下对叶绿素-a (1)进行空气氧化反应, 分别得到卟吩衍生物2b～4b; 通过酯交换和去金属镁离子, 将叶绿素-a转化为脱镁叶绿酸-a甲酯(MPa) (5), 其3-位碳碳双键与氯化氢的加成生成卟吩醇(6), 经碱性空气氧化和E-环重排则转化成紫红素-18衍生物7. 选用四氧化锇和高碘酸钠将5氧化成卟吩醛(8), 在丁醇中以丁醇钠作催化剂, 8的氧化和重排反应给出3-甲酰基紫红素-18酯(9)和紫红素-7三甲酯衍生物10. 异构体4的空气氧化和重排反应也生成紫红素-18酯(3), 进一步与2-甲基丁胺进行缩合反应, 得到N-烷基紫红素-18酰亚胺(11a)以及氧化重排产物3-甲酰基-N-烷基紫红素-18酰亚胺(11b). 所得叶绿素衍生物均经UV, IR, 1H NMR及元素分析证明其结构, 并对相应的反应提出可能的反应机理.     

Metalla-Claisen Rearrangement in Gold-Catalyzed [4+2] Reaction: A New Elementary Reaction Suggested for Future Reaction Design

We report here computational evidence for a metalla-Claisen rearrangement (MCR) in the case of gold-catalyzed [4+2] cycloaddition reaction of yne-dienes. The [4+2] reaction starts from exo cyclopropanation, followed by MCR and reductive elimination. The cyclopropane moiety formed in the first step is crucial for a low barrier of the MCR step. In addition, the importance of an appropriate combination of the tether group and the terminal substituent on alkyne in the yne-diene substrates was studied. The mechanism of rhodium-catalyzed [4+2] reaction of yne-dienes was also investigated to see whether an MCR mechanism is involved or not. The findings and new understanding hereby reported represent an important advance in the catalysis field.     

Electron-Impact Induced Rearrangement Reactions of Organic Molecules

Hydrogen migrations accompany many mass spectrometric fragmentation processes and a detailed study of these migrations, largely by means of deuterium labeling, has shed much light on electron-impact induced bond fissions. More recently, it has been found that groups other than hydrogen, such as alkyl, aryl, hydroxyl, etc., also can migrate after electron bombardment and the present article is concerned with a discussion of such molecular rearrangements among organic compounds. These observations are not only of intrinsic mechanistic interest, but a detailed knowledge of the occurrence of such migration reaction is crucial to the proper interpretation of mass spectra and to the avoidance of misinterpretations in “element mapping”.