共轭双烯辅助下的烯丙基碳氢键活化:Rh(I)催化的多取代的四氢吡咯、四氢呋喃及环戊烷衍生物的合成

<正>J.Am.Chem.Soc.2010,132,4542～4543选择性C-H键官能团化是一种非常经济、高效地利用碳氢化合物的方法.在诸多C-H键活化/C-C键形成的反应中,将C-H键进行活化后直接加     

催化研究的新希望:烷烃C-H键的活化

选择性是催化反应的精髓。近几年通过金属有机化合物,高选择性的活化饱和烷烃中的不活泼碳-氢键获得成功。反应在均相体系和温和条件下进行,反应选择性发生在饱和碳氢键的伯碳位置。饱和碳氢化合物中的碳氢键与金属有机络合物首先发生氧化加成,然后进行还原消除,生成金属-碳σ键化合物。类似结构的铑络合物也能活化丙烷中的C-H键。     

低碳烷烃与二氧化碳催化转化研究进展

页岩气革命为低碳经济发展提供了重要契机.在低碳烷烃(甲烷和乙烷)催化转化过程中,以二氧化碳作为氧化剂参与反应,通过C-H键的选择性活化可将页岩气转化为优质化工原料——合成气和乙烯,是一种低碳烷烃转化与二氧化碳资源化利用的工艺路线.本文总结了近年来甲烷干重整与乙烷和二氧化碳反应中与C-H键活化相关的研究进展,分析了甲烷干...     

Fe-N-C单原子催化剂的C-H键选择性氧化反应（英文）

C-H键活化是近年来发展最为迅速的研究领域之一,从自然界中广泛存在C-H键的简单底物为原料,利用C-H键直接活化策略来构建高附加值的化学品是一类具有高原子经济性的化学反应.然而,由于C-H键的稳定性使得C-H键的选择性官能团化过程具有极大的挑战.例如,烃类化合物的C-H选择性氧化生成醇/酮化合物在C1化学以及有机合成反应中占据重要地位,同时C-H键的高解离能以及氧化试剂的高活性往往使得这类反应的选择性难以调控.近日,中科院大连化学物理研究所张涛和王爱琴领导的团队在脂肪族、芳香族烃类化合物的C-H选择性氧化反应中取得新的研究进展.作者使用Fe-N-C单原子催化剂,化学计量的叔丁基过氧化氢为氧化剂,在室温条件下实现了烃类化合物的选择性氧化反应,一系列底物包括带有吸电子基团的硝基(-NO_2)、供电子基团的甲氧基(-OCH_3)、杂环化合物以及脂肪族化合物(环己烷)均可以高选择性(98%)实现转化.事实上,Fe-N-C单原子催化剂的活性与选择性可与均相催化剂([Cu((R,R)-BPBP)]+)相媲美,同时该催化剂在绿色水溶剂中表现出优异的循环稳定性.这项工作的另一个意义在于建立起多相催化领域中活性位点与反应性能之间的构效关系.通过HAADF-STEM,XPS,XAS,ESR及穆斯堡尔谱等表征手段,清楚地证明Fe-N-C催化剂中三价铁离子存在多种配位结构(FeN_x,x=4,5,6),催化剂活性与Fe-Nx的特定结构密切关联.C-H键选择性氧化反应的最高活性位点为中自旋FeN_5位点,其活性高出低自旋/高自旋的FeN_6位点一个数量级,是FeN_4位点活性的3倍之多.而该FeN_5结构的数量在Fe-N-C-700的单原子催化剂上仅占18%,说明Fe-N-C催化剂的活性具有很大的提升空间.文中报道的Fe-N_x-C催化剂可被认为是一类新型的单原子催化剂,其中,N_x基团为一种强有力的配体.由于单原子催化剂兼具均相催化剂孤立均一的活性位点及多相催化剂易于循环使用的优势,单原子催化剂有望成为连接均相催化与非均相催化的桥梁.目前,单原子催化剂已成为多相催化领域一个新的研究热点与前沿.这篇工作中的FeN_5位点与血红蛋白的Fe中心结构类似,从这个角度出发,FeN_5位点为连接酶催化剂与多相单原子催化剂提供了一个很好的案例.然而,FeN_5位点周围环境的细微变化都会直接影响其反应活性以及选择性,从而导致多相催化中的FeN_5具有较差的O_2活化能力.因此,设计更为高效的多相单原子催化剂,实现类似于酶催化中高效高选择性地活化底物分子,仍然具有很大的挑战与空间.     

镧系金属有机络合物活化甲烷键

饱和烷烃中碳-氢键的活化,以甲烷键最困难。用镧系金属有机络合物活化甲烷键首次获得成功,典型的反应是:镥或镱的烷基衍生物或氢化物,在温和条件下不仅能活化sp~2 C-H键,而且也能活化Si(CH_3)_4中的sp~3C-H键。通过改变络合物的结构,可以控制这个反应的选择性,这是实现催化控制的新途径。活化反应如下:     

芳香化合物的电化学C—H键官能化研究进展

C—H键是有机化合物中最基本和最广泛的化学键.利用电化学方法实现芳香化合物C—H键的官能化和直接转化可以避免反应物的预官能化,是一种绿色可持续且更具有原子经济性的转化途径.该方法借助阳极上的氧化反应实现芳香化合物C—H键的官能化,完成C—X键(X=C、N、O、S)的构建和稠环化合物的合成,无需使用氧化剂.通过控制电极材料、电解质和溶剂等条件,也可以实现特定的化学选择性和区域选择性.综述了近年来芳香化合物的电化学C—H键官能化这一领域的研究进展.     

基于导向策略的C—H键活化反应的研究进展

C—H键是有机化合物中存在最广泛的化学键之一.过渡金属催化的C—H键活化反应具有反应效率高、原子经济性高、产生废物少等优点,因此发展新的C—H键的转化类型和方法十分重要.由于分子内经常存在高度稳定且活性相似的C—H键,所以导致传统的C—H键活化反应的区域选择性很差,难以真正被应用于天然产物或者药物分子等的合成中.向反应体系中引入导向基团后,不仅可以大大提高C—H键官能化反应的活性,更可以提高区域选择性,实现高效合成单一目标产物的目的.因此,探索导向基导向的C—H键直接官能化反应具有重要意义.将从不同导向原子的角度介绍近十年导向基辅助的C—H键活化反应,并对其作用机理进行相关阐述.     

交叉脱氢偶联反应*

发现高效高选择性的有机合成反应是有机合成化学研究中一个重要的发展方向。传统的有机合成化学是建立在官能团相互转化基础上的,又称官能团化学。非活泼化学键（如C-H键）的直接官能团化省去了一步甚至多步制备官能团化的反应底物,因此,非活泼化学键活化是提高有机合成反应效率的一个重要发展方向。交叉脱氢偶联（Cross-Dehydrogenative-Coupling,CDC）反应就是直接利用不同反应底物中的C-H键,在氧化条件下,进行脱氢偶联反应形成C-C键。交叉脱氢偶联反应实现了更短的合成路线和更高的原子利用效率,为直接利用简单的原料进行高效的复杂的有机合成任务提供了一种新的思路和手段。     

CuO+氧化苯直接形成苯酚反应机理的理论研究

在UB3LYP/6-31G(d,p) 水平下研究了CuO+氧化苯形成苯酚反应的详细机理,同时计算了单重态和三重态势能面。计算结果表明,苯与CuO+间相互作用主要为?配键,反馈?键较弱. CuO+氧化苯形成苯酚反应通过非自由基氢摘取机理完成,主要包括C-H键活化和苯基与羟基耦合两步反应. C-H键活化为整个反应的决速步骤. C-H键活化步骤涉及势能面交叉,且自旋交叉与动力学相关。CuO+氧化苯形成苯酚反应在气相中很容易进行.     

Pd催化的配体导向C—H键乙酰化反应的理论研究

Pd催化的配体导向C-H键官能化反应已经成为有机化学中一种重要的合成手段. 我们用B3PW91密度泛函方法研究了Pd催化的配体导向C-H键乙酰化反应中催化剂和底物配合步骤以及C-H键活化步骤中的热力学性质. 研究发现, 具有不同导向基团的反应物之间竞争反应的选择性取决于导向基团与Pd(OAc)₂的配合步骤, 配合反应稳定常数大的较容易生成乙酰化的产物. 另一方面, 反应的选择性与C-H键的活化步骤无关, 并且与导向基团的配位原子的气相碱性、原子上的电荷密度以及最高占据轨道能量都没有相关性.     

Recent progress in transition metal catalysed hydrofunctionalisation of less activated olefins

The electrophilic activation(C-H activation) of alkenes by transition metal catalysts is a fundamental step in a rapidly growing number of catalytic processes since it would provide simple, clean, and economic methods for making controlled and selectively functionalized organic moieties directly from simple olefins. Also catalytic activation of C-H bonds leading to useful organic reactions such as new C-C, C-N and C-O bond formation is of considerable interest for the chemical and pharmaceutical industries and remained a long-term challenge to chemists. A substantial progress has made in the last decade in this area. Contrary to traditional belief, it is nowadays possible to control the regiochemistry of various additions of nucleophiles to alkenes by the choice of transition metal catalysts. Atom economy, an inevitable factor of current research also can be accomplished in these reactions. Developments in this area of selective hydrofunctionalisation of alkenes by taking into consideration of the mechanistic aspects and the role of organometallic catalyst or active species formed during the reaction on the outcome of the reactions are reviewed.     

Catalytic C-H functionalization by metalloporphyrins: recent developments and future directions

Metalloporphyrins are a class of versatile catalysts with the capability to functionalize saturated C-H bonds via several well-defined atom/group transfer processes, including oxene, nitrene, and carbene C-H insertions. The corresponding hydroxylation, amination, and alkylation reactions provide direct approaches for the catalytic conversion of abundant hydrocarbons into value-added functional molecules through C-O, C-N, and C-C bond formations, respectively. This tutorial review describes metalloporphyrin-based catalytic systems for the functionalization of different types of sp(3) C-H bonds, both inter- and intramolecularly, including challenging primary C-H bonds. Additional features of metalloporphyrin-catalyzed C-H functionalization include unusual selectivities and high turnover numbers.     

无过渡金属条件下喹啉C5位碳-氢键官能化反应

喹啉是一类重要的杂环化合物,喹啉类化合物的合成方法研究备受关注。通过喹啉的碳-氢键直接官能化反应制备取代喹啉类衍生物是一种简便而有效的方法。然而,喹啉的C5位选择性碳-氢键官能化反应仍然存在挑战,目前大多在过渡金属催化下实现,无过渡金属条件下的反应亟待开发。本文按成键类型(碳-卤键、碳-氮键、碳-氧键、碳-硫键和碳-碳键)分类综述了近年来在无过渡金属条件下喹啉C5位碳-氢键官能化反应的研究进展,并对该领域的研究现状及所存在的问题进行了总结。     

Bifunctional transition metal-based molecular catalysts for asymmetric syntheses

The discovery and development of conceptually new chiral bifunctional transition metal-based catalysts for asymmetric reactions is described. The chiral bifunctional Ru catalyst was originally developed for asymmetric transfer hydrogenation of ketones and imines and is now successfully applicable to enantioselective C-C bond formation reaction with a wide scope and high practicability. The deprotonation of 1,3-dicarbonyl compounds with the chiral amido Ru complexes leading to the amine Ru complexes bearing C- or O-bonded enolates, followed by further reactions with electrophlies gives C-C bond formation products. The present bifunctional Ru catalyst offers a great opportunity to open up new fundamentals for stereoselective molecular transformation including enantioselective C-H and C-C as well as C-O, C-N bond formation.     

Interaction of niobium and tantalum pentahalides with O-donors: coordination chemistry and activation reactions

The chemistry of niobium and tantalum pentahalides, MX(5), with oxygen compounds is reviewed herein. The polynuclear structure of MX(5) is readily broken by addition of oxygen-containing organic molecules, L, to give either mononuclear or ionic dinuclear coordination adducts. Then activation of the organic ligand may take place favoured by several factors, i.e. low M-X bond energy, high temperature, presence of more than one oxygen function within L, L/M molar ratio ≥ 2. The activation reactions are often uncommon in the context of metal halides; they include the cleavage of C(sp3)-O, C(sp2)-O, C-H and C-C bonds, and eventual successive rearrangements proceeding with C-O or C-C couplings. The recently elucidated reactivity of MX(5) with limited amounts of oxygen compounds will be presented, and possible connections with the relevant MX(5)-directed syntheses reported in the literature will be outlined.     

Asymmetric transformations involving 1,2-dicarbonyl compounds as pronucleophiles

This article concentrates on the versatile nucleophilic reactivity of 1,2-dicarbonyl compounds in various asymmetric transformations. Although underexploited in comparison to their 1,3-dicarbonyl homologues, the presence of adjacent multiple reactive centres allows the selection of specific activation modes for enhancing the reactivity of these important ambident pronucleophiles. They can be involved in selective formation of C-C, C-O or C-N bonds leading to various optically active targets in the acyclic and cyclic series including three- to seven-membered ring systems. Recent contributions in the field of biochemical, organometallic and organic catalytic transformations as well as some relevant stoichiometric approaches are discussed from synthetic and mechanistic point of views highlighting some important stereochemical issues.     

Tandem reactions initiated by copper-catalyzed cross-coupling: a new strategy towards heterocycle synthesis

Copper-catalyzed cross-coupling reactions which lead to the formation of C-N, C-O, C-S and C-C bonds have been recognized as one of the most useful strategies in synthetic organic chemistry. During past decades, important breakthroughs in the study of Cu-catalyzed coupling processes demonstrated that Cu-catalyzed reactions are broadly applicable to a variety of research fields related to organic synthesis. Representatively, employing these coupling transformations as key steps, a large number of tandem reactions have been developed for the construction of various heterocyclic compounds. These tactics share the advantages of high atom economics of tandem reactions as well as the broad tolerance of Cu-catalyst systems. Therefore, Cu-catalyzed C-X (X = N, O, S, C) coupling transformation-initiated tandem reactions were quickly recognized as a strategy with great potential for synthesizing heterocyclic compounds and gained worldwide attention. In this review, recent research progress in heterocycle syntheses using tandem reactions initiated by copper-catalyzed coupling transformations, including C-N, C-O, C-S as well as C-C coupling processes are summarized.     

C-C, C-O and C-N bond formation via rhodium(III)-catalyzed oxidative C-H activation

Rhodium(III)-catalyzed direct functionalization of C-H bonds under oxidative conditions leading to C-C, C-N, and C-O bond formation is reviewed. Various arene substrates bearing nitrogen and oxygen directing groups are covered in their coupling with unsaturated partners such as alkenes and alkynes. The facile construction of C-E (E = C, N, S, or O) bonds makes Rh(III) catalysis an attractive step-economic approach to value-added molecules from readily available starting materials. Comparisons and contrasts between rhodium(III) and palladium(II)-catalyzed oxidative coupling are made. The remarkable diversity of structures accessible is demonstrated with various recent examples, with a proposed mechanism for each transformation being briefly summarized (critical review, 138 references).     

The golden gate to catalysis

The use of gold in homogeneous catalysis is a relatively new field of transition metal catalysis, but has already witnessed spectacular achievements. By virtue of their unique ability to activate carbon-carbon double and triple bonds as soft, carbophilic Lewis acids, gold salts are highly efficient catalysts for the formation of C-C, C-O, C-N, and C-S bonds. Moreover, they are capable of activating C-H bonds of aromatic and other substrates, opening unprecedented pathways for their functionalisation. By using chiral allenes as substrates, gold catalysts can even be applied in stereoselective target-oriented synthesis.