烯酮类化合物的aza Diels-Alder环加成反应研究进展

烯酮类化合物因其特殊的结构和化学性质而广泛应用于环加成反应中。烯酮类化合物的aza Diels-Alder反应研究在近年来得到了迅速发展。根据烯酮在aza Diels-Alder反应中的作用（双烯体、亲双烯体和自身环化）分类,综述了其在aza Diels-Alder反应中的研究进展。     

α-氧代烯酮环二硫代缩酮化学(ⅩⅫ) ——硫醇(酚)为亲核体的α-氧代烯酮环二硫代缩酮与2-甲基烯丙基氯化镁加成物的取代-环合芳构化反应

缩酮基为五元和六元环的α-氧代烯酮环二硫代缩酮与2-甲基烯丙基氯化镁反应得1,2-加成产物。所得加成产物在酸催化条件下以乙硫醇为亲核体时生成芳基乙基硫醚;苯硫酚为亲核体时,产物为芳基苯基硫醚。同样实验条件下,缩酮基为甲硫基的α-氧代烯酮二硫代缩酮与2-甲基烯丙基氯化镁的1,2-加成则生成芳构化产物芳基甲基硫醚。本实验从亲核体的选用上进一步拓展了所述取代-环合芳构化反应,并进一步验证了缩酮基结构对反应活性的影响。     

亮点介绍

通过三烯胺机制催化2,4-二烯酮的不对称Diels-Alder反应Angew.Chem.Int.Ed.2012,51,4401～4404三烯胺(trienamine)机制作为新发展的一种有机胺催化模式,已经成功应用于通过HOMO-活化的不对称Diels-Alder反应中,然而仅有的几篇报道都局限于2,4-二烯醛底物.四川大学华西药学院     

经由α-羰基烯酮环二硫代缩醛的取代-环合芳构化及分解反应

本文报道了芳香族α-羰基烯酮环二硫代缩醛与2-甲基烯丙基Grignard试剂的1,2-加成产物在酸催化下的取代-环合芳构化反应及分解反应。探讨了亲核试剂体积、缩醛基结构对取代-环合芳构化反应活性的影响。     

经由α-羰基烯酮环二硫代缩醛的取代-环合芳构化及分解反应

本文报道了芳香族α-羰基烯酮环二硫代缩醛与 2-甲基烯丙基Grignard试剂的1,2-加成产物在酸催化下的取代-环合芳构化反应及分解反应. 探讨了亲核试剂体积, 缩醛基结构对取代-环合芳构化反应活性的影响.     

分子内Diels-Alder反应的立体化学

Diels-Alder反应是研究得最多的环化加成反应,它的反应历程、立体化学等问题是近年来有机化学工作者广泛探讨的一个领域。本文在不对称分子间Diels-Alder反应的立体化学基础上,初步介绍分子内Diels-Alder反应(以下简称IMDA反应)的立体选择性。第一个IMDA反应于1953年由Alder和Schumaker提出,它是一个苯乙烯的衍生物,     

呋喃类化合物在离子液体和硅胶负载离子液体中的Diels-Alder反应

以1-丁基-3-甲基咪唑盐作为离子液体阳离子,与3种不同阴离子BF4、PF6、Tf2N组成性质不同的3种离子液体,催化呋喃类和丁炔二羧酸酯之间发生Diels-Alder反应,合成了一系列化合物,研究了离子液体的催化效果.研究结果表明,呋喃类化合物的极性越低, Diels-Alder反应的活性越高.在含硫的呋喃类化合物的反应中,当以[Bmim]PF6作离子液体时,Diels-Alder反应产率可达53%.当[Bmim]PF6离子液体被吸附在硅胶表面上时,Diels-Alder的反应产率有所提高.     

呋喃类化合物在离子液体和硅胶负载离子液体中的Diels-Alder反应研

以1-丁基3-甲基咪唑盐作为离子液体阳离子,与三种不同阴离子BF4、PF6、Tf2N组成性质不同的三种离子液体,催化呋喃类和丁炔二羧酸酯之间发生的Diels-Alder反应,合成了一系列化合物,研究了离子液体的催化效果。研究表明,呋喃类化合物的极性越低, Diels-Alder 反应的活性越高。在含硫的呋喃类化合物的反应中,当以 [Bmim]PF6 作为离子液体时,Diels-Alder 反应的产率可达到53%。另外,当 [Bmim]PF6 离子液体被吸附在硅胶表面上时,Diels-Alder的反应产率有所提高。     

α—氧代烯酮环二硫代缩酮化学（XXII）：硫醇（酚）为亲核体的…

缩酮基为五元和六元环的α－氧代烯酮环二硫代缩酮与２－甲基烯丙基氯化镁反应得１，２－加成产物。所得加成产物在酸催化条件下以乙硫醇为亲核体时生成芳基乙基硫醚；苯硫酚为亲核体时，产物为芳基苯基硫醚。同样实验条件下，缩酮基为甲硫基的α－氧代烯酮二硫代缩酮与２－甲基烯丙基氯化镁的１，２－加成则生成芳构化产物芳基甲基硫醚。本实验从亲核体的选用上进一步拓展了所述取代－环合芳构化反应，并进一步验证了缩酮基结构对反     

经由β,β-(1,4-亚丁二硫基)-α,β-不饱和酮的芳构化反应

为研究缩醛基结构上的差异对反应性能的影响,我们对α-羰基烯酮环二硫代缩醛2的合成及其在合成上的应用做了一些讨论. 本文合成了一些新的缩醛基为七元环的标题化合物2~c~1-~c~1~0, 选择其中代表物2~c~1与烯丙基, 2-甲基烯丙基, 苄基等Grignard试剂反应, 并观察了加成产物在BF~3·Et~2O催化下的芳构化反应性能.     

Multiple rate-determining steps for nonideal and fractal kinetics

We show that the kinetic model of a single rate-determining step in a reaction mechanism can be extended to systems with multiple overall reactions for which the elementary reactions obey nonideal or fractal kinetics. The following assumptions are necessary: (1) The system studied is either closed or open, but no constraints exist preventing the evolution toward equilibrium. (2) Elementary reactions occur in pairs of forward and backward steps. (3) The kinetics of the elementary steps are either nonideal or fractal and are compatible with equilibrium thermodynamics. (4) The number of reaction routes is identical with the number of rate-determining steps. If these hypotheses are valid, then the overall reaction rates can be explicitly evaluated: they have a form similar to the kinetic equations for the elementary reactions and the apparent reaction orders and fractal coefficients can be expressed analytically in terms of the kinetic parameters of the elementary reactions. We derive a set of relationships which connect the equilibrium constants of the reaction routes, the corresponding overall rate coefficients, and the stoichiometric numbers of the rate-determining steps. We also derive a set of generalized Boreskov relations among the apparent activation energies of the forward and backward overall processes, the corresponding reaction enthalpies, and the stoichiometric coefficients of the rate-determining steps. If the elementary reactions obey fractal kinetics, the same is true for the rate-determining steps. The fractal exponents of the forward and backward overall reactions are linear combinations of the fractal exponents of the fractal elementary reactions. Similar to the theory of single rate-determining steps, our approach can be used for selecting suitable reaction mechanisms from experimental data.     

Shift of the rate-determining step in a consecutive chemical reaction with variation of the reaction affinity

A consecutive single-route reaction is considered. When two (groups of) steps compete in controlling the overall reaction rate, there exists a general rule that the earlier step in the flow of the overall reaction tends to be rate-determining with the increase of the reaction affinity. The latter may, however, be distributed more or less evenly to both steps.     

Total synthesis of lamellarins D, H, and R and ningalin B

A concise total synthesis of lamellarins D (7 steps), H (7 steps), and R (5 steps) and ningalin B (5 steps) is achieved starting from the corresponding aldehydes and amines. The synthesis features three oxidative reactions as key steps in a biomimetic manner, involving an AgOAc-mediated oxidative coupling reaction to construct the pyrrole core, a Pb(OAc)(4)-induced oxidative cyclization to form the lactone, and Kita's oxidation reaction to form the pyrrole-arene C-C bond.     

Construction of the reaction networks for heterogeneous catalytic reactions: Fischer—Tropsch synthesis and related reactions

The key approaches to the generation of reaction networks for the synthesis of products from CO and H₂ are considered. The selection rules for the elementary steps on the surface of heterogeneous catalysts are formulated. Data on the surface compounds and steps related to reactions of CO and H₂ are analyzed and a set of transforms (models of elementary steps) for generation of the reaction network are selected. Eight variants of generation of reaction networks for the formation of C1 products with different sets of transforms (12 to 31) were tested in computer experiments, and eight reaction networks comprising 34 substances and 132 to 1647 elementary steps were obtained. The pathways to CO₂, CH₄, and CH₃OH and pairs of compounds CH₄, CO₂ and CH₄, HCOOH obtained from the reaction network (220 elementary steps) are compared with the published schemes.     

一个改进的Dallacker双内酯的合成

以5步反应从邻碘苯甲酸乙酯合成了9,10-二氢-9,9,10,10-双(γ-丁内酯)菲,减少了3步反应,总产率提高7%.又由邻碘苯甲酰氯与乙烷-1,1,2-三羧酸三乙酯缩合,继以消除两个乙酯基合成Dallacker双内酯,反应减少一步,产率则增高13%.还研究了联苯-2,2-二甲酰氯分别与乙烷-1,1,2-三羧酸三乙酯和氰基琥珀酸二乙酯的缩合,均能得到良好的产率.     

Concise synthesis of 1-epi-castanospermine

1-epi-Castanospermine (5) was synthesized from readily available 2,3,4,6-tetra-O-benzyl-1-deoxynojirimycin (11) in 9 steps and 21% overall yield, with selective debenzylation, Barbier reaction and reductive amination as the main reaction steps.     

乙烯基炔与一氧化氮反应机理的理论探讨

利用半经验AM1方法，研究了乙烯基乙炔与一氧化氮反应生成丙炔腈（反应1）和丙烯腈（反应2）的两条竞争反应途径．采用Berny梯度法优化得到了反应势能面上的所有驻点，并逐一进行了振动分析确认．结果表明，反应互较反应Ⅱ易引发（即；NO比较容易与乙烯基乙炔进行分步的1，4-加成，形成六元环过渡态及中间体，最终消除CH2O和H自由基后生成丙炔腈），而反应Ⅱ较难引发（NO与乙烯基乙炔较难进行1，2-加成，形成四元环过渡态及中间体），但一经引发，就能较容易地进行分步裂解，生成丙烯腈和CHO自由基．     

Investigation of thermal decomposition of phosphonic acids

The paper compares building and decomposition pathways of two phosphonic acids, amino trimethylene phosphonic acid (ATMP) and 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP).The theoretical formation reactions were composed using elementary reactions and compared to reaction routes published in literature. As result, summary reaction pathways for both phosphonic acids are proposed which only vary in the number of reaction steps required. These reaction steps include carbonyl reactions, S_N2-reactions, and ionic reactions. The synthesis of ATMP proceeds in three reaction steps, whereas HEDP is formed in one reaction. The thermal decomposition of both phosphonic acids in solid state was examined by combination of thermogravimetry coupled with infrared spectroscopy as well as pyrolysis gas chromatography coupled with mass spectrometry. Decomposition mechanisms were deduced and compared to the theoretical findings resulting in the conclusion that the decomposition processes of ATMP and HEDP follows the formation mechanism.Thus, the suitability of theoretical considerations for the understanding of thermal decomposition processes is shown.     

Mechanism of TBD-catalyzed hydrolysis of acetonitrile

1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) has recently been shown to be an effective organocatalyst for the hydrolysis reaction of acetonitrile. This reaction involves the acetamide-forming reaction of acetonitrile hydrolysis and the further hydrolysis of acetamide to form acetic acid and NH₃. Density functional theory (DFT) and Hartree–Fock (HF) methods were employed to comprehensively investigate these two hydrolysis steps to elucidate the TBD-catalyzation mechanism. Structures and energies of the reactants, intermediates, transition states and products along the reaction path were presented. Charge population and bond orders were given by natural bond orbital (NBO) analysis to clarify the computed atomic and molecular behaviors. The results showed that compared with the noncatalyzed reaction, the TBD-catalyzed process had significantly lower energy barriers in both the hydration steps and the isomerization steps. As a result, the whole reaction process could be accelerated and the TBD-catalyzation mechanism was clarified.     

Studies on macrocyclic diterpenoids. V. Synthesis of (±)-sarcophytol-A benzyl ether

The title compound, sarcophytol-A benzyl ether has been synthesized through 13 steps by employing acetone and geraniol as starting materials. The key steps in the synthesis were double bond migration reaction of allylic alcohols 5 and 6, phase transfer catalytic coupling (PTC) reaction of II with 7 and the cyclization reaction of dicarbonyl acyclic precursor induced by TiCl₃-AlCl₃(3:1)/Zn-Cu system.