杂环型稳定硅烯插入HF、H_2O和NH_3反应

硅烯为卡宾的硅类似物,在有机光和热化学中作为一类重要的反应活性中间体引起了化学界的广泛兴趣.杂环型硅烯是实验合成的稳定硅烯,因其在有机硅化学中的重要作用,十几年来在实验和理论上均有研究报道.本文基于单重态杂环型硅烯的特殊电子性质和丰富的化学反应性,系统探讨了几种杂环型硅烯的插入反应.使用密度泛函理论(DFT),在B3LYP/6-311++G(d,p)水平上研究了三种氮杂环型不饱和硅烯(1,3,4)和两种氮杂环型饱和硅烯(2,5)分别与H—X(X=F,OH,NH2)键的插入反应,阐明了插入反应的机理并对各反应的结果进行了比较.杂环型硅烯与H—X的插入反应机理类似于简单硅烯,体现了硅烯的亲电亲核的双重反应性.由反应势垒和反应热看,五种硅烯与H—X键的插入反应均为HF最容易,H2O次之,NH3最难.饱和硅烯的反应性比不饱和硅烯的反应活性高,这也间接验证了杂环型饱和硅烯在实验中较难合成.     

二氟硅杂环丙烯异构化反应的理论研究

近十几年来，硅烯（：SN小'一到作为活性中间体的研究引起化学界的广泛兴趣，形成了内容丰富的硅烯化学．1975年Ilass＊等研究了硅烯和乙炔的加成反应，指出该反应的中间体为硅杂环丙烯，硅杂环丙烯异构化为硅甲基乙炔．Boatz问等利用：j－ZIG（d）基组对金属杂环丙烯小［＊xZC     

二氟硅烯与甲醛环加成反应机理的理论研究

硅烯（R2Si：）是某些有机硅反应的重要活性中间体[1],硅烯反应（如插入反应,加成反应,聚合反应等）被认为是合成含硅新键和含硅杂环的有效方法,因而硅烯反应的研究一直是有机硅化学家十分感兴趣的一个前沿研究领域[2]．对于硅烯的环加成反应而言,由于它具有合成含硅张力小环的重要价值,因此受到了许多化学家的高度重视,并对此做了若干的研究工作[3-7]。然而到目前为止,关于硅烯环加成反应的机理还处于一种推测水平,尤其是对卤代硅烯环加成反应机理的研究,至今尚未见文献报导,考虑到卤代卡宾在合成张力小环方面的重要作用[8,9]…     

有机硅反应活性中间体的研究Ⅶ: 二(α-呋喃基)硅烯与烯烃加成反应的立体化学

硅烯是有机硅化学中一类基本的反应活性中间体.在研究硅烯与烯烃加成反应的立体化学过程中,我们曾研究了二苯基硅烯、苯基环丙基硅烯与烯加成反应的立体化学.近年来,Gaspar和Boudjouk分别报道了含大体积取代基的硅烯,如二金刚烷基硅烯、二叔丁基硅烯与烯烃的加成反应.我们从取代基的电子效应考虑曾研究了2-苯基-2-(a-噻吩基)六甲基三硅烷的光解,发现反应是自由基机理.氧和硫同属第Ⅵ主族,与噻吩相对应的含呋喃环三硅烷的光解又如何呢?因此,我们又设计并合成了二(α-呋喃基)硅烯的前体,2,2-二(α-呋喃基)六甲基三硅烷(1),并研究了这种硅烯与烯烃加成的立体化学.当1在光照下与trans-2-丁烯或cis-2-丁烯反应,所得硅杂环丙烷衍生物用甲醇开环时,得到了相同的2-丁基-二(α-呋喃基)甲氧基硅烷(3).     

有机硅活性中间体的研究 Ⅲ.含噻吩环硅烯的产生及其捕获

硅烯(两价的硅)和卡宾(两价的碳)一样,是一类基本的反应活性中间体,但含有杂环的硅烯,目前研究还不多.我们曾报道了含呋喃基苯基硅烯的产生.噻吩环的硫原子虽然和呋喃环的氧同属周期表中的第六族元素,但硫是第三周期,其最外层的3s和3p电子距原子核较远,估计将会有不同于呋喃基苯基硅烯的性质.因此,进行了含噻吩环硅烯的产生及捕获的研究. 产生噻吩基苯基硅烯的前体化合物是2-(α-噻吩基)-2-苯基六甲基三硅烷(1).首先由α-     

有机硅反应活性中间体的研究Ⅶ: 二(α-呋喃基)硅烯与烯烃加成反应的立体化学

本文设计并合成了二(α-呋喃基)硅烯的前体,2,2-二(α-呋喃基)六甲基三硅烷(1),并研究了这种硅烯与烯烃加成的立体化学。结果表明： 二(α-呋喃基)硅烯与烯烃的加成反应是以立体专一方式进行的。其中间物硅杂环丙烷的开环反应也是以顺式方式进行的。这也说明 二(α-呋喃基)硅烯基态的电子组态是单线态。     

有机硅反应活性中间体研究——Ⅸ.苯基呋喃基硅烯和二呋喃基硅烯与烯烃的加成

研究了2-(-呋喃基)-2-苯基硅烯和2,2-二(-呋喃基)硅烯与烯烃的加成反应的立体化学。它们与烯烃加成时按立体专一方式进行,中间体硅杂环丙烷被甲醇开环时也是以顺式方式进行。     

铜催化共轭乙烯基联烯硅和1,3-二烯硅合成

在温和反应条件下,铜催化间隔烯炔衍生物与有机硅烷硼酸酯化合物发生反应,通过调控有机硅硼试剂的用量,以较高产率分别制备共轭乙烯基联烯硅和1,3-共轭二烯硅产物.该方法为制备多取代立体选择性官能团化联烯和1,3-共轭二烯产物提供了简单、高效的合成工具.     

烷基对取代锂氟类硅烯R2SiLiF的构型和热稳定性的影响

利用从头计算法研究了二甲基锂氟类硅烯和二乙基锂氟类硅烯的各异构体的构型和能量.烷基的引入增加了Si的σ电子对Li的授与而降低了F对Si空p轨道的电子回授,使类硅烯的p-络合物构型热稳定性下降,而σ-络合物热稳定性增加.在上述两种作用的共同影响下,三元环构型的热稳定性只有很小的变化.     

硅烯量子点二聚物的等离激元激发

基于含时密度泛函理论,研究了随着间距改变时硅烯量子点二聚物的等离激元激发特性。沿垂直于硅烯所在平面方向激发时,在一定间距范围内,硅烯量子点二聚物中形成了长程电荷转移激发模式。参与长程电荷转移激发的π电子主要在两个量子点之间运动。该等离激元模式随着间隙的减小发生蓝移。此外,在不同间距时,体系中还有两个等离激元共振带,分别位于7和15 eV附近。沿平行于硅烯所在平面方向激发时,由于两个量子点之间的耦合,在低能     

Towards click chemistry: Multicomponent reactions via combinations of name reactions

In this report, we try to show the importance of incorporation of name reactions in the sequential cascade reaction in which significantly decreasing the number of steps towards an ideal and practical multi-step synthesis of natural products as well showing virtually all the advantages already mentioned for “Click Chemistry”. In addition, since the chiral inductions are desired for most of these sequential name reactions, their asymmetric catalyzed reactions were also described.     

Recent advances in ionic liquids: green unconventional solvents of this century: part II

Abstract

In the second part of our paper, further recent developments of ionic liquids in selected name reactions of carbonyl chemistry such as Mannich, Reformatsky, Cannizaro, Streacker, Barbier, Pechmann, etc. are described.     

Competitive thermal ene reaction and Diels-Alder reactions of 2-[N-(alk-2-enyl)benzylamino]-3-vinylpyrido[1,2-a]pyrimidin-4(4H)-ones

Thermal reaction of 2-[N-(alk-2-enyl)benzylamino]-3-(2-substituted and 2,2-disubstituted)vinylpyrido[1,2-a]pyrimidin-4(4H)-ones gave azepine, the desired ene products, and/or pyran derivatives. The formation of the latter was responsible for the [4+2] cycloaddition reaction between the α,β-unsaturated ester carbonyl moiety as a diene part and the alkenylamino moiety as an ene one. The reaction features depended upon the kinds of substituents both on the vinyl and alkenyl counterparts; strongly electron-withdrawing substituents on the vinyl moiety or an electron-donating substituent on the alkenyl one changed the reaction feature from the ene reaction to the hetero Diels-Alder reaction.     

Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate) catalyzed Suzuki, Heck, Sonogashira, and cyanation reactions

Palladium bis(2,2,6,6-tetramethyl-3,5-heptanedionate): a structurally well-defined O-containing transition metal complex is reported as an efficient catalyst for Suzuki, Heck, and Sonogashira cross-coupling reactions. The protocol was also applied successfully for cyanation of aryl halides under milder operating conditions. The system tolerated the coupling of various aryl halides with alkenes, alkynes, and organoboronic acid along with the cyanation of aryl halides providing good to excellent yields of desired products.     

Oxa-Michael加成反应的研究新进展

Oxa-Michael加成反应是一类重要的反应, 经常被用于天然产物的合成, 但该反应直到近几年才被深入研究. 简要综述了oxa-Michael加成反应的研究进展.     

Boehmite@tryptophan‐Pd nanoparticles: A new catalyst for C–C bond formation

A boehmite@tryptophan‐Pd nanoparticulate catalyst was prepared by a simple, fast and convenient route. The nanomaterial was characterized using various techniques and employed as a thermally stable catalyst for Heck, Stille and Suzuki cross‐coupling reactions. Optimized conditions for these reactions are described. The catalyst could be isolated, post‐reaction, by simple filtration and recycled for several consecutive cycles without a notable change in its activity.     

Acid‐Acid‐Catalyzed Tandem Reactions Driven by an Additive‐Like Component

Acid‐catalyzed tandem reactions with auto‐tandem catalysis are effective for simplifying organic synthesis. However, some of the reported reactions were established based on the use of well‐designed substrate with complex structure. In some cases, owing to the existence of a big gap between each catalytic cycle, it is hard to bind all the individual reaction steps to be a peaceful sequence. To enrich the diversity and also to strengthen the practical usefulness of the methodology developed by auto‐tandem catalysis, an additive‐like component was added to induce acid‐acid‐catalyzed tandem reaction. During the reaction, the additive‐like component acted either as an activator to increase the reactivity of the starting material or a hided reagent to enable successful transformation of the intermediate. Many novel tandem reactions were established in a one‐pot manner with the aid of this strategy. Importantly, this strategy not only allows the use of simple and commercially available chemicals as substrates, but also possesses multiple merits, such as simplifying operation, lowering waste generation and enhancing synthetic efficiency and atom‐economy. A summarization of the additive‐like component‐induced auto‐tandem catalysis with an acid catalyst was given in this review, in which many acid‐acid‐catalyzed tandem reactions were discussed. The reported additive‐like components were classified as three types: oxidative type, reductive type and neutral type depending on their mechanisms in assisting the establishment of acid‐acid‐catalyzed tandem reactions. Many examples were collected and analyzed from the viewpoints of simplifying the synthesis and manifesting their superior and distinct functionalities of the additives. A perspective of this concept was also given at the end of this review.     

钯催化的交叉偶联反应——2010年诺贝尔化学奖获奖工作介绍

钯催化的交叉偶联反应是非常实用的合成新方法.文章给出了Heck反应、Negishi反应和Suzuki反应的概念,对其反应机理作了详细的说明,并对其在复杂化合物和天然产物全合成中的应用作了评价.     

Extension of solution‐reaction‐surface description to examination of nonequilibrium solvation effect for microsolvated reaction

A microscopic method to examine a nonequilibrium solvation effect is reported. The solution reaction is simplified as a barrier‐crossing reaction within a solution reaction surface that corresponds to a two‐dimensional space determined by solute and solvent reactive coordinates. For this simplification, the motions within the space spanned by nonreactive coordinates are frozen. We derive three rate constant expressions: (1) in the nonadiabatic solvation limit, (2) in the equilibrium solvation limit, and (3) of the transition‐state theory. This method was applied to the examination of the contact‐ion‐pair formation of t‐BuCl in four waters. We found that the nonadiabatic solvation picture overestimates the nonequilibrium solvation effect. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 77: 791–796, 2000     

具有1,2-二苯基乙醇结构化合物的异常消除反应研究

报道了4个具有1,2-二苯基乙醇结构的化合物在酸性条件下发生消除反应, 得到未遵循Saytzeff规则的烯烃; 而在SOCl2/DMF条件下, 先氯代再消除则可获得一对双键位置异构的烯烃异构体. 通过计算机模拟, 采用Gaussian 98软件, B3LYP/6-31G方法对两种异构体进行了能量优化, 计算了它们的能量, 推测这类具有1, 2-二苯基乙醇结构化合物在酸性条件下的异常消除反应为动力学主导产物的反应.