硅烷化试剂在药物合成中的应用

综述了硅烷化试剂的特点、保护原理和应用,重点介绍了硅烷化试剂在药物合成中的应用,举例介绍了氨苄西林、前列腺素、辛伐他汀和[（＋）-Detoxinine]等药物中羟基的保护和去保护条件。     

位阻型硅烷化试剂在药物合成中的研究与应用

综述了位阻型硅烷化试剂的特点、保护原理和应用。就其在保护含杂原子的有机官能 团方面讨论了对羟基、羧基、羰基及胺基等的保护和去保护条件及其在药物合成中的应用。并对位 阻型硅烷化试剂的发展趋势进行展望。     

有机硅试剂

有机硅试剂最初是作为醇的保护试剂用于有机合成的。随着有机硅化学的迅速发展,有机硅化合物作为合成试剂及中间体的研究受到了普遍的重视。许多有机硅化合物,如烯醇硅醚、三甲基碘硅烷、烯基、芳基硅烷等,均是具有多种反应性能的合成试剂,可以发生烃化、     

含异氰酸酯基丙基三乙氧基硅烷的合成

研究了氯丙基三乙氧基硅烷与氰酸钾反应制备异氰酸酯基丙基三乙氧硅烷的方法,考察了反应温度,反应物的配比优化,溶剂种类以及保护试剂的种类对合成产率的影响,确立了最佳的合成条件：反应物氯丙基三乙氧基硅烷与氰酸钾的摩尔比为1：1．15,DMF为溶剂,己内酰胺为保护试剂,反应温度为125℃,收率可达92％,并采用波谱分析确证了目标物质的结构。     

疏水性HMS分子筛的制备及水热稳定性

以三甲基氯硅烷和六甲基二硅氮烷为硅烷化试剂,分别采用气相和液相硅烷化法对HMS分子筛进行表面改性制备疏水性HMS分子筛。考察了改性方法、硅烷试剂与分子筛摩尔比、反应温度和时间对硅烷化效果的影响,研究了改性前后HMS的骨架特征、微观结构和疏水性、水热稳定性。结果表明:气相硅烷化法较液相法优势明显,硅烷化程度和效率均较高;在双硅烷化试剂、反应温度90℃、硅烷试剂与分子筛摩尔之比0.8、反应时间8 h等条件下,改性前后HMS的静态水吸附量分别为45.46%和1.38%,疏水性得到明显提高。HMS经硅烷化改性后保持介孔骨架结构和蠕虫状孔道,同时水热稳定性得到有效改善,800℃水蒸气处理6 h后介孔结构仍然存在。     

三甲基氯硅烷的性质及其应用研究进展

三甲基氯硅烷是一种非常重要的硅烷化试剂,介绍了三甲基氯硅烷的物理化学性质,重点阐述了三甲基氯硅烷在色谱分析、有机合成、基团保护等方面的应用研究。     

绿色合成3-异氰酸酯基丙基三甲氧基硅烷的研究

采用氰酸钾和3-氯丙基三甲氧基硅烷为原料,以氰化法合成3-异氰酸酯基丙基三甲氧基硅烷.确定了最佳工艺条件:反应温度105℃,催化剂用量1％,投料比n KOCN︰n3-氯丙基三甲氧基硅烷=2.5,保温时间4 h,保护试剂为己内酰胺,最佳用量n己内酰胺︰n3-氯丙基三甲氧基硅烷=1.6,溶剂为N-甲基甲酰胺,添加量为45％...     

硅烷化保护剂六甲基二硅脲的合成研究

选取特殊的催化引发剂，使合成硅烷化保护试剂ＢＳＵ的反应时间缩短到４ｈ，收率达到９８．５％。产品经室温储存二个月，硅烷化活性仍高达９７％，可满足７－ＡＤＣＡ合成的需要。     

海洋环境下涂层与硅烷对混凝土保护效果的对比

根据工程调研、暴露试验和室内试验的结果,分析比较了涂层和硅烷浸渍两种混凝土表面防护措施的保护效果。结果发现,实体结构中涂层的保护效果比硅烷差,但在暴露试验和室内试验中,涂层有比硅烷更好的抗氯离子渗透能力。涂层和硅烷保护不同龄期失效后,硅烷保护的混凝土自身扩散系数衰减因子低于涂层保护的混凝土扩散系数衰减因子。     

几种重要的有机硅试剂

近十五年来,对有机硅化合物(以后简称有机硅)的研究越来越多,其应用也越来越广。据报导,含硅取代基的某种有机化合物,能起活化、定向、稳定中间体以及保护官能团等作用。某种类型的有机硅可用作特殊的合成试剂,进行多种专一性反应,例如硅烷基烯醇醚能与多种强亲电试剂发生位置专一性的亲电取代反应。     

Controlling the Physical and Electrochemical Properties of Arylamines Through the Use of Simple Silyl Ethers: Liquid,Waxy and Glassy Arylamines

The effect of silyl ether substitution on the physical and electrochemical properties of single and two-nitrogen centered arylamines was explored. It was found that this substitution can significantly lower the T_g and suppress crystallization of these compounds. This resulted in arylamines that were isolated as liquids, waxes, glasses, and in some cases crystalline solids at ambient conditions. Additionally, these silyl ether groups were found to be relatively strong electron donating groups with similar donating potentials to the well known methyl ether group. It is concluded that silyl ether substitution is a synthetic handle to greatly alter the physical properties of arylamines without substantially changing their basic electronic properties.     

Distant C-H Activation/Functionalization: A New Horizon of Selectivity Beyond Proximity

Activation/functionalization of inert C-H bond has undergone rapid growth in last decade and provides novel retro-synthetic disconnections for the synthesis of valuable molecules. The selectivity is often achieved by the use of directing group and is mainly limited to the proximal C-H bond. Initially, meta C-H activations were based on electronic or steric control and now it can be achieved by employing nitrile-based end-on-template as the directing group. The compilation of the remote C-H activation strategy will provide the useful linkage to the scientific community. This article is focused on recent progress in remote C-H activation, mechanistic understanding, and its applications in the field of total synthesis of targeted molecules.     

Copper(I)‐Catalyzed Allylic Substitution of Silyl Nucleophiles through Si?Si Bond Activation

We report the first copper(I)‐catalyzed reaction between a disilane and allylic carbonates to produce allylsilanes. The silyl nucleophilic substitution proceeded primarily in a S_N2 fashion whereas S_N2′ products were also obtained through σ‐π‐σ isomerization of the copper(III) intermediate depending on the substrate’s steric bulk.     

Assembly of macrocycles by zirconocene-mediated, reversible carbon-carbon bond formation

Macrocyclic compounds have attracted considerable attention in numerous applications, including host-guest chemistry, chemical sensing, catalysis, and materials science. A major obstacle, however, is the limited number of convenient, versatile, and high-yielding synthetic routes to functionalized macrocycles. Macrocyclic compounds have been typically synthesized by ring-closing or condensation reactions, but many of these procedures produce mixtures of oligomers and cyclic compounds. As a result, macrocycle syntheses are often associated with difficult separations and low yields. Some successful approaches that circumvent these problems are based on "self-assembly" processes utilizing reversible bond-forming reactions, but for many applications, it is essential that the resulting macrocycle be built with a strong covalent bond network. In this Account, we describe how zirconocene-mediated reductive couplings of alkynes can provide reversible carbon-carbon bond-forming reactions well-suited for this purpose. Zirconocene coupling of alkenes and alkynes has been used extensively as a source of novel, versatile pathways to functionalized organic compounds. Here, we describe the development of zirconocene-mediated reductive couplings as a highly efficient method for the preparation of macrocycles and cages with diverse compositions, sizes, and shapes. This methodology is based on the reversible, regioselective coupling of alkynes with bulky substituents. In particular, silyl substituents provide regioselective, reversible couplings that place them into the α-positions of the resulting zirconacyclopentadiene rings. According to density functional theory (DFT) calculations and kinetic studies, the mechanism of this coupling involves a stepwise process, whereby an insertion of the second alkyne influences regiochemistry through both steric and electronic factors. Zirconocene coupling of diynes that incorporate silyl substituents generates predictable macrocyclic products in very high yields. In the absence of significant steric repulsion, the macrocyclization appears to be entropically driven, thereby providing the smallest strain-free macrocyclic structure. The scope of the reaction has been explored by variation of the spacer group between the alkynyl substituents and by incorporation of functional and chiral groups into the macrocycle. The size and shape of the resulting macrocycles are largely determined by the length and geometry of the dialkyne spacer, especially in the case of terminal trimethylsilyl-substituted diynes. For example, linear, rigid diynes with four or fewer phenylene rings lead to trimeric macrocycles, whereas bent or flexible diynes produce dimers. Depending on the reaction conditions, functional groups (such as N-heterocycles and imines) are tolerated in zirconocene coupling reactions, and in selected cases, they can be used to influence the shape of the final macrocyclic product. More recently, Cp(2)Zr(pyr)(Me(3)SiC≡CSiMe(3)) has been employed as a more general zirconocene synthon; it affords higher yields and increased functional group tolerance. Functional groups can also be incorporated through transformation of the zirconacyclopentadiene products, with acid hydrolysis to the corresponding butadiene being the most efficient derivatization. Furthermore, construction of chiral macrocycles has been accomplished by stereoselective macrocyclizations, and triynes have been coupled into three-dimensional cage compounds. We also discuss various design factors, providing a perspective on the utility of zirconocene-mediated couplings in the assembly of macrocyclic and cage compounds.     

Improved Synthesis of Pyrroles and Indoles via Lewis Acid‐Catalyzed Mukaiyama–Michael‐Type Addition/Heterocyclization of Enolsilyl Derivatives on 1,2‐Diaza‐1,3‐Butadienes. Role of the Catalyst in the Reaction Mechanism

The Mukaiyama–Michael‐type addition of various silyl ketene acetals or silyl enol ethers on some 1,2‐diaza‐1,3‐butadienes proceeds at room temperature in the presence of catalytic amounts of Lewis acid affording by heterocyclization 1‐aminopyrrol‐2‐ones and 1‐aminopyrroles, respectively. 1‐Aminoindoles have been also obtained by the same addition of 2‐(trimethylsilyloxy)‐1,3‐cyclohexadiene on some 1,2‐diaza‐1,3‐butadienes and subsequent aromatization. Mechanistic investigations indicate the coordination by Lewis acid of the enolsilyl derivative and its 1,4‐addition on the azo‐ene system of 1,2‐diaza‐1,3‐butadienes. The migration of the silyl group from a hydrazonic to an amidic nitrogen, its acidic cleavage and the final internal heterocyclization give the final products. Based on NMR studies and ab initio calculations, a plausible explanation for the migration of the silyl protecting group is presented.     

Nucleation products of ligated nanoclusters unaffected by temperature and reducing agent

Atomically uniform nucleation products of ligated metal nanoclusters are observed irrespective of reduction conditions for metal-bidentate ligand systems. Monodentate ligands are not reported to wield similar control, indicating steric contributions of complexing ligands may be as important as their electronic structure for synthesizing small nanoclusters.     

Advances in non-metallocene ⅣB group metal catalysts for olefin polymerization

按配体类型,综述了近年来第ⅣB族非茂金属烯烃聚合催化剂研究进展,其配体类型包括：胺基类、酮亚胺类、吡唑类、苯氧亚胺类等。讨论了配体结构和电子效应对催化剂聚合活性及聚合物结构、分子量等的影响;概括了高活性第ⅣB族非茂金属烯烃聚合催化剂应具备的条件。     

电位效应与空间位阻效应对飞机燃油抗氧剂膦化物的氧化反应的影响

膦化物为高性能飞机燃油潜在的抗氧剂,研究表明,膦化物取代基的电位效应与空间位阻效应对其氧化反应有一定的影响,而且在不同类型的反应中,两种效应的影响作用不同,强的吸电子电位效应及大的空间位阻效应均不利于膦化物的氧化反应。     

电位效应与空间位阻效应对飞机燃油抗氧剂膦化物的氧化反应的影响

膦化物为高性能飞机燃油潜在的抗氧剂，研究表明，膦化物取代基的电位效应与空间位阻效应对其氧化反应有一定的影响，而且在不同类型的反应中，两种效应的影响作用不同，强的吸电子电位效应及大的空间位阻效应均不利于膦化物的氧化反应。     

Theoretical analysis of the rotational barrier of ethane

The understanding of the ethane rotation barrier is fundamental for structural theory and the conformational analysis of organic molecules and requires a consistent theoretical model to differentiate the steric and hyperconjugation effects. Due to recently renewed controversies over the barrier's origin, we developed a computational approach to probe the rotation barriers of ethane and its congeners in terms of steric repulsion, hyperconjugative interaction, and electronic and geometric relaxations. Our study reinstated that the conventional steric repulsion overwhelmingly dominates the barriers.