Transition-metal catalyzed oxidative cross-coupling reactions to form C-C bonds involving organometallic reagents as nucleophiles

Transition-metal-catalyzed coupling reactions have become a versatile tool for chemical bond formation. From the variation of the coupling partners, coupling reactions can be classified into three models: traditional coupling, reductive coupling and oxidative coupling. The oxidative coupling, which is different from the traditional coupling, occurs between two nucleophiles. This critical review focuses on transition-metal-catalyzed oxidative coupling reactions involving organometallic reagents as nucleophiles. Since the scope of the oxidative coupling is highly diversified, this paper only reviews the oxidative coupling reactions concerning C-C bond formation, including the coupling between organometal reagents and hydrocarbons as well as coupling between two organometal reagents. Since terminal alkynes are normally activated by metal salts and in situ form the alkynyl metal reagents in coupling reactions, they are directly considered as organometal reagents in this review. Intramolecular oxidative couplings and oxidative cyclizations are not included in this critical review. Moreover, there are many examples of oxidative coupling leading to the formation of functional materials, such as the oxidative polymerization of thiophenes. Since several reviews in these areas have been published they are not included in this review either (99 references).     

Catalysts and thermodynamic coupling of chemical reactions

The condition of occurrence of the thermodynamic coupling of chemical reactions is analysed from kinetics. It is found that the thermodynamic coupling is impossible for those reactions which obey kinetically the mass action law. The thermodynamic coupling of chemical reactions is further analysed in the case with catalyst. It is found that the thermodynamic coupling which is impossible without catalyst may become possible by introducing proper catalyst into the system. This implies that the catalysts can change not only the rates of chemical reactions, but also the behaviors of thermodynamic coupling of chemical reactions, including the direction of some reactions. Such role of catalysts comes into play not by changing the total free energy of the system, but by changing the reaction mechanism.     

Preparation of stereodefined homoallylic amines from the reductive cross-coupling of allylic alcohols with imines

Regio-, diastereo-, and enantioselective coupling reactions between imines and allylic alcohols have been developed. These coupling reactions deliver complex homoallylic amine products through a convergent C-C bond forming process that does not proceed through intermediate allylic organometallic reagents. In general, convergent coupling, by exposure of an allylic alkoxide to a preformed Ti-imine complex, occurs with allylic transposition in a predictable and stereocontrolled manner. While simple diastereoselection in these reactions is high, delivering anti-products with ≥20:1 selectivity, the organometallic transformation described is compatible with a diverse range of functionality and substrates (including aliphatic and aromatic imines, allylic silanes, trisubstituted alkenes, vinyl- and aryl halides, trifluoromethyl groups, thioethers, and aromatic heterocycles). Alkene geometry of the products is a complex function of the allylic alcohol structure and is consistent with a mechanistic proposal based on syn-carbometalation followed by syn-elimination by way of a boat-like transition state geometry. Single asymmetric coupling reactions provide a means to translate the stereochemical information of the allylic alcohol to the homoallylic amine or to control diastereoselection in the coupling reactions of achiral allylic alcohols with chiral imines. Double asymmetric coupling reactions are also described that afford a unique means to control stereoselection in these complex convergent coupling processes. Finally, empirical models are proposed that are consistent with the observed stereochemical course of these coupling reactions en route to chiral homoallylic amines possessing di- or trisubstituted alkenes and anti- or syn- relative stereochemistry at the allylic and homoallylic positions.     

金属催化端炔与亚胺衍生物亲核加成制备炔丙基胺的研究进展

综述了端炔与C=N双键亲核加成制备炔丙基胺的合成方法的研究进展.其中包括醛亚胺的间接或直接偶联反应,烯胺的间接偶联反应,酮亚胺的间接或直接偶联反应等.参考文献30篇.     

Transition metal-catalyzed cyclocarbonylation in organic synthesis

Cyclocarbonylation reactions proceed mainly by the coupling reactions of carbonylation components with cyclization components having an unsaturated π-electron bond, in the presence of transition metal compounds. The representative reactions are cyclocarbonylation of alkynes by carbon monoxide such as Pauson–Khand reactions, hetero Pauson–Khand reactions, cyclocarbonylation of alkynyl alcohols, cyclocarbonylation of alkynyl amines, cyclocarbonylative alkyne–alkyne coupling reactions, and reductive cyclocarbonylation of alkynes. The other reactions are cyclocarbonylation of alkenes by carbon monoxide such as alkene–alkene coupling reactions, cyclocarbonylation with aldehydes, ketones, amines or imines, cyclocarbonylation of alkenyl alcohols. Carbonylation via cyclometalation, carbonylative ring expansion reactions, cyclocarbonylation by aldehydes, carboxylic acids or carboxylic acid esters are also cyclocarbonylation reactions. These reactions are conveniently used for organic syntheses, especially, for the syntheses of pharmaceutical intermediates.     

低价钒试剂促进的有机反应及其在有机合成中的应用

综述了近年来低价钒试剂促进的有机反应及其在有机合成中的应用。重点讨论了低价钒试剂促进下的碳-碳键的形成反应，如卤代烃的还原偶联、醛(酮)的还原偶联、羰基化合物的脱氧烷基化及脱氧偶联反应等。另外，还介绍了催化量的低价钒度剂在促进有机反应方面的应用。     

An efficient nickel-catalyzed alkenylation of functionalized benzylic halides with alkenylaluminum reagents

Highly efficient and simple coupling reactions of benzylic bromides or chlorides with alkenylaluminum reagents catalyzed by NiCl(2)(PPh(3))(2) are reported. The coupling reactions proceed effectively at room temperature employing low loading of catalyst, 0.5 mol% for benzylic bromides having either electron-donating or -withdrawing substituents on the aromatic ring, affording coupling products in excellent yields of up to 94% in short reaction times. The coupling reactions of benzylic chloride require 5 mol% of the catalyst and a longer reaction time of 2 h.     

Synthesis of cryptands with di-yne units via acetylenic homocoupling reactions of C3 tripodands

Cryptands with di-yne units were obtained in good yields by the acetylenic homocoupling reaction of tripodands possesing terminal ethynyl units on the pendant arms. The coupling reactions also led to isomeric bismacrocylic compounds, and the shifting of the process toward the products of intramolecular or intermolecular coupling reactions was influenced by the structure of tripodands and by the coupling reaction conditions.     

Synthesis and characterization of covalently linked multilayer films prepared in the absence of solvent

We report the preparation of multilayer organic thin films prepared by sequential vapor-phase coupling of monomers. The reactions were carried out at room temperature and atmospheric pressure. Films prepared using up to six sequential coupling reactions are reported. The following specific vapor-phase reactions were found to be viable: reactions between acid chlorides and both aliphatic and aromatic amine, hydrolysis reactions, anhydride activation, and reactions between anhydrides and primary amines. Homobifunctionalized monomers, such as hexamethylenediamine, react primarily via a single endgroup rather than cross coupling to the reactive surface via both reactive groups. The estimated coverage of the multilayer films is between 36 and 46%. The films were characterized using ellipsometric, contact angle, and spectroscopic measurements.     

Palladium-catalyzed coupling of allylboronic acids with iodobenzenes. Selective formation of the branched allylic product in the absence of directing groups

Palladium-catalyzed coupling reactions of functionalized allylboronic acids with iodobenzenes were achieved under standard Suzuki-Miyaura coupling conditions. The coupling reactions afforded selectively the branched allylic products in high to excellent yields. In contrast to palladium-catalyzed nucleophilic substitution reactions proceeding via (eta3-allyl)palladium intermediates, this process does not require directing groups in the allyl moiety to achieve substitution at the congested allylic terminus. The regioselectivity of the process was largely unaffected by the substituent effects of the iodobenzenes and the allylic substrates.     

Au(I) /Au(III) catalysis: an alternative approach for C-C oxidative coupling

When reacted in the presence of external oxidants, gold complexes are capable of catalyzing oxidative homo- and cross-coupling reactions involving the formation of new C-C bonds. Over the last few years, several cascade processes have been reported in which coupling is preceded by a gold-mediated aryl C-H functionalization or nucleophilic addition. These reactions combine the unique reactivity of gold with oxidative coupling, enabling the construction of C-C bonds between coupling partners that are not easily accessed using alternative catalysts. In this Concept paper, the development of gold-catalyzed oxidative coupling reactions is discussed focusing on C-C bond-forming reactions of broad synthetic appeal.     

Anodic coupling reactions: the use of N,O-ketene acetal coupling partners

Intramolecular anodic olefin coupling reactions utilizing N,O-ketene acetals have been studied. Coupling reactions with both enol ether and allylsilane terminating groups were examined. The reactions involving the coupling of the N,O-ketene acetals with allylsilane groups were found to be much more efficient than corresponding reactions utilizing dithioketene acetal groups and allylsilanes. The reactions were also more efficient than the intramolecular coupling reactions between enol ethers and allylsilanes studied earlier.     

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.     

Simple and efficient nickel-catalyzed cross-coupling reaction of alkynylalanes with benzylic and aryl bromides

Highly efficient and simple coupling reactions of benzylic and aryl bromides with aluminium acetylide catalyzed by NiCl(2)(PPh(3))(2) are reported. The coupling reactions proceed at room temperature employing 4 mol% catalyst, affording coupling products in excellent yields of up to 95% in short reaction times. The system worked efficiently with aryl and heterocyclic bromides as well.     

Ni催化的碳(sp2)-碳和碳(sp2)-杂交叉偶联反应

综述了Ni催化的碳(sp²)-碳和碳(sp²)-杂交叉偶联反应. 主要反应类型有: Heck反应、Sonogashira反应、Kumada-Corriu反应、Negishi反应、Stille反应、Suzuki反应、Ullmann反应、C—N偶联反应、C—O偶联反应、C—P偶联反应和C—S偶联反应. 详细地介绍了各个反应的底物要求、反应条件、反应选择性和产率. 最后, 我们对Ni催化的反应机理研究也作了总结.     

Ullmann‐Ma Reaction: Development,Scope and Applications in Organic Synthesis†

Copper‐catalyzed cross‐couplings of aryl halides and nucleophiles, traditionally called Ullmann‐type coupling reactions, were initially reported by Ullmann et al. from 1901—1929. A seminal report in 1998 by Ma et al. from Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences revealed an accelerating effect caused by amino acids, which brought Ullmann‐type coupling reactions into a ligand‐accelerating era. From 1999 to the first 10 years of 2000s, the first‐generation ligands were developed by many researchers and promoted Ullmann‐type coupling reactions of aryl iodides and bromides under relatively mild conditions. Amino acid ligands, developed by Ma and coworkers, are one class of the most important first‐generation ligands. In the second 10 years of 2000s, Ma et al. led the discovery of second‐generation ligands for copper‐catalyzed cross‐coupling reactions. Two great breakthroughs have been realized by using second‐generation oxalic diamide and related amide ligands, with aryl chlorides as general coupling partner and with low catalyst loadings. Now copper‐catalyzed cross coupling reactions of aryl halides and nucleophiles with amino acids or oxalic diamides and related amides as ligands are recognized as Ullmann‐Ma reactions and have found extensive applications in organic synthesis.     

亚铜催化的碳杂偶联反应机理*

近年来,亚铜催化的碳杂偶联反应以其高效、低成本和易制备等优点被广泛研究并应用于工业生产,有机合成及生物活性分子的制备中。目前对于这些碳杂偶联反应机理的探究仍然处于探索性阶段。本文主要评述了近年来亚铜催化的碳杂偶联反应机理的研究进展。重点综述近年来研究相对较多,对机理认识较为完善的碳-氮偶联(特别是酰胺类化合物的芳基化过程),碳氧偶联以及碳硼偶联(不饱和有机化合物的硼化、二硼化反应)机理等方面的进展。最后,基于目前这些机理研究工作的现状,展望了未来机理探究的主要方向。     

The first N-heterocyclic carbene-based nickel catalyst for C-S coupling

We have developed the first N-heterocyclic carbene (NHC)-based transition metal catalysts for C-S coupling reactions. Ni-NHC catalysts showed good to excellent activities toward various aryl halides in C-S coupling reactions. The catalytic activities were greatly affected by the electronic and steric properties of the NHC ligands. The new catalysts were inexpensive, easy to synthesize, and environmentally friendly. They could be excellent candidates to replace Pd-organophosphanes for C-S coupling catalysis.     

Head-to-tail regioregular oligothiophene-functionalized 9,9'-spirobifluorene derivatives. 1. Synthesis

Two series of novel fully conjugated oligomers, oligothiophene-functionalized 9,9'-spirobifluorene derivatives, have been developed in this contribution. First, four 9,9'-spirobifluorene bromide derivatives (compounds 1a-d) are prepared through various synthetic routes. Oligothiophene derivatives with or without substituents are synthesized through the Grignard and Suzuki coupling reactions. The Negishi coupling reactions between oligothienylzinc chloride and various 9,9'-spirobifluorene bromides with Pd(PPh(3))(4) as catalyst successfully produce the desired compounds, unsubstituted oligothiophene-functionalized 9,9'-spirobifluorene derivatives, compounds 2 to 4a-d. Since the Negishi coupling reactions afford regioregularly head-to-tail (H-T) oligo(4-n-hexylthiophene)-functionalized 9,9'-spirobifluorene derivatives in poor yields, the Suzuki coupling reactions between sodium 4-n-hexylthienyl-2-boronate 8, and various 9,9'-spirobifluorene-based bromides 1a-d and 9-16 are employed to produce highly regioregular head-to-tail oligothiophene-functionalized 9,9'-spirobifluorene derivatives (compounds 5 to 7a-d) in very high yields. We also investigate the effect of solvents on the Suzuki coupling reactions. The structure and purity of all compounds are verified by FT-IR, (1)H and (13)C NMR, MS, and elemental analysis.     

Silane treatment in polypropylene composites: Adsorption and coupling

The study of the effect of eight silane coupling agents on mechanical properties of PP/CaCO₃ composites showed that the application of certain compounds leads to the reactive coupling of the components. The adsorption of the silanes on the surface of the filler was studied by a dissolution method, while the structure of the adsorbed layer was determined by FTIR spectroscopy and GPC measurements. Model reactions and an FTIR study were carried out to reveal possible coupling reactions of PP and the active silanes. The results showed that amino-functional silane coupling agents adsorb on the surface of the filler, polycondensation taking place and a polysiloxane layer of high molecular weight forms as a result. The model reactions indicated that during processing, PP oxidizes even in the presence of stabilizers and oxygen-containing functional groups form on the polymer chains. These easily react with the amino functionality of the silane coupling agents strongly bonding the polymer to the treated filler.