Diaryl sulfides synthesis: copper catalysts in C–S bond formation

ABSTRACT

Diaryl sulfides play an important role in the synthesis of natural products, pharmaceutically and biologically molecules. The metal catalysts are powerful tools for C–S bonds formation. Despite the utility of palladium-catalyzed carbon–sulfur bond formation, copper complexes are fascinating catalysts for this transformation because copper is less toxic and inexpensive than palladium. In recent times, a large number of protocols using various copper catalysts to perform cross-coupling reactions leading to the synthesis of diaryl sulfides have been described. In this review, we summarized recent developments in the area of synthesis of diaryl sulfides based on using copper catalysts. Both the considerable advantages and drawbacks of these protocols are discussed.     

芳基硼酸在有机合成中的应用

芳基硼酸作为一种重要的中间体,在有机合成中的应用相当广泛。Suzuki偶联反应是合成联芳基结构最有效的方法之一,近年许多用于芳基硼酸与各种卤代芳烃偶合的催化剂相继被开发。芳基硼酸与苯酚在Cu(OAc)2和NEt3存在时用于合成二芳基醚,与胺的偶联是合成C-N键的有效方法,与,α-β不饱和体系的1,4-共轭加成反应广泛用于β-取代羰基化合物的合成。反应采用相对无毒而又廉价的普通试剂,反应条件温和,产率高,立体选择性好。综述了芳基硼酸在联芳基合成、二芳基醚合成、芳香胺合成和催化加成反应中的应用。     

Activation of aryl chlorides in water for Suzuki coupling with a hydrophilic salen-Pd(II) catalyst

For exploiting aqueous condition, we have designed a simple water-soluble palladium Schiff-base catalyst for Suzuki-Miyaura reactions of aryl halides with arylboronic acids. The reactions could be performed in neat water with aryl bromides and iodides at room temperature and with aryl chlorides at 100 °C. Good-to-excellent yields of cross-coupling products were obtained with a diverse range of aryl halides including heteroaryl halides. Interestingly, the homogeneous catalyst could be conveniently recycled with aryl bromides or chlorides for at least four times, although a progressive decrease in the product yields were noticed.     

过渡金属催化合成芳基硫化物

芳基硫化物具有很好的生物活性,在医药行业和有机合成中具有广泛的应用.不同过渡金属催化合成芳基硫化物成为当前研究的一个热点.本文简单综述了不同过渡金属催化硫醇的芳基化反应合成芳基硫化物.     

Fe3O4-carbon spheres core–shell supported palladium nanoparticles:A robust and recyclable catalyst for suzuki coupling reaction

Suzuki-Miyaura(S-M) is regarded the most powerful way for synthesis biaryls, triaryls, or incorporating of substituted aryl moieties in organic preparation by the cross-coupling of aryl boronic acid with aryl halides using the Pd catalyst. This work reports the combining of the hydrothermal and microwaveassisted protocol to convert the glucose to magnetic carbon spheres(Fe₃O₄-CSPs) decorated with Pd nanoparticles(NPs) as the catalyst for Suzuki-Miyaura cross-coupling reacti...     

钯催化草酸钾盐与碘苯脱羧偶联反应的研究

利用乙二酸单乙酯酸钾和碘苯在钯催化条件下脱羧偶联反应.通过改变催化剂、溶剂得到了最优化的反应条件:以三氟乙酸钯为催化剂,N-甲基吡咯烷酮为溶剂,乙二酸单乙酯酸钾和碘苯于140℃得到产率为82％的苯甲酸乙酯;同样乙二酸单丁酯酸钾也取得了理想的收率.     

Transition-metal-catalyzed C–N cross-coupling reactions of N-unsubstituted sulfoximines: a review

ABSTRACT

In recent years, N-functionalized sulfoximines have attracted the significant attention of medicinal chemists due to their wide spectrum of biological activities. This class of organosulfur compounds has also found a number of applications in agricultural chemistry. In addition to these benefits, sulfoximines are one of the most important and versatile chiral auxiliaries and ligands in asymmetric syntheses. As a result of these, numerous efforts have been devoted to the development of effective strategies towards the synthesis of N-functionalized sulfoximines. An efficient, practical, and versatile strategy for the synthesis of titled compounds involves the transition-metal-catalyzed cross-coupling reactions of easily accessible NH-sulfoximines with various electrophilic partners. In this review, we highlight a number of recent discoveries and advances in this interesting and important research arena. The N-alkylation reactions are discussed first. This is followed by metal-catalyzed N-alkenylation and N-alkynylation reactions. Finally, N-arylation reactions will be covered at the end of the review.     

Copper(I) selenophene-2-carboxylate (CuSC) promoted C–S cross-coupling reaction of thiols with aryl iodides

We reported the synthesis of copper (I)-selenophene-2-carboxylate (CuSC) and application as new catalyst in the cross-coupling reactions of thiols with aryl iodide to afford the corresponding unsymmetrical thioethers. The optimized reaction conditions were applied to thiols and aryl iodides having a wide range of functional groups, including electron rich and electron poor substrates. The chemoselectivity of the reaction with 4-iodobromobenzene and 2-aminothiophenol derivatives was briefly examined through the competitive iodine versus bromine and thiol versus nitrogen cross-coupling.     

Pd催化芳基重氮盐的Suzuki偶联反应研究进展

综述了不同Pd催化剂催化的芳基重氮盐的Suzuki偶联反应,并对其优缺点进行了比较,同时对Suzuki偶联反应的应用进行了阐述。     

Fast, efficient and convenient method for the preparation of arylazo sulfides using aryl diazonium silica sulfates under mild and solvent-free conditions

An efficient, fast, and straightforward procedure for the synthesis of arylazo sulfides and arylazo thiosulfonates is described in the present paper by using aryl diazonium silica sulfates and sodium thiolates. Using the present method, different kinds of aryl diazonium silica sulfates, containing electron-withdrawing groups as well as electron-donating groups, were rapidly converted to the corresponding arylazo sulfides in good yield and short reaction time. These reactions were carried out at room temperature under mild and solvent-free conditions. The use of non-toxic and inexpensive materials, simple and clean work-up, short reaction times and good yields are the advantages of this method.     

硫醚合成研究进展

以芳基硫醚、二芳基硫醚、烯基硫醚、炔基硫醚、炔丙基硫醚为例,综述了近十几年来各种硫醚的合成研究进展,报道了化学家们在合成硫醚这一领域里的合成方法。这些合成方法应用了许多过渡金属催化,包括Pd,Cu,Ni,Co,Fe和Rh等等,也包括应用了无机盐,并对硫醚合成的研究前景进行了展望。     

Palladium-catalyzed Suzuki-Miyaura cross-coupling reactions employing dialkylbiaryl phosphine ligands

The cores of many types of polymers, ligands, natural products, and pharmaceuticals contain biaryl or substituted aromatic structures, and efficient methods of synthesizing these structures are crucial to the work of a broad spectrum of organic chemists. Recently, Pd-catalyzed carbon-carbon bond-forming processes, particularly the Suzuki-Miyaura cross-coupling reaction (SMC), have risen in popularity for this purpose. The SMC has many advantages over other methods for constructing these moieties, including mild conditions, high tolerance toward functional groups, the commercial availability and stability of its reagents, and the ease of handling and separating byproducts from its reaction mixtures. Until 1998, most catalysts for the SMC employed triarylphosphine ligands. More recently, new bulky and electron-rich phosphine ligands, which can dramatically improve the efficiency and selectivity of such cross-coupling reactions, have been introduced. In the course of our studies on carbon-nitrogen bond-forming reactions, we found that the use of electron-rich and bulky phosphines enhanced the rate of both the oxidative addition and reductive elimination processes; this was the beginning of our development of a new family of ligands, the dialkylbiarylphosphines L1-L12. These ligands can be used for a wide variety of palladium-catalyzed carbon-carbon, carbon-nitrogen, and carbon-oxygen bond-forming processes as well as serving as supporting ligands for a number of other reactions. The enhanced reactivity of these catalysts has expanded the scope of cross-coupling partners that can be employed in the SMC. With use of such dialkylbiarylphosphine ligands, the coupling of unactivated aryl chlorides, aryl tosylates, heteroaryl systems, and very hindered substrate combinations have become routine. The utility of these ligands has been successfully demonstrated in a wide number of synthetic applications, including industrially relevant processes. In this Account, we provide an overview of the use and impact of dialkylbiarylphosphine ligands in the SMC. We discuss our studies on the mechanistic framework of the reaction, which have allowed us to rationally modify the ligand structures in order to tune their properties. We also describe selected applications in the synthesis of natural products and new materials to illustrate the utility of these dialkylbiarylphosphine ligands in various "real-world" synthetic applications.     

Oxidation of sulfides to sulfoxides with 1, 3-dibromo-5, 5-dimethylhydantoin in the presence of hydrated silica gel

Chemo selective oxidation of sulfides to sulfoxides with 1,3-dibromo-5,5-dimethylhydantoin in dichloro-methane in the presence of hydrated silica gel has been developed. Decomposition of the bromosulfonium salt intermediate produced in this reaction to the product is facilitated by the water present in hydrated silica gel. Hydrated silica gel, as the source of necessary water, expanded the scope of oxidation reactions of sulfides to sulfoxides with N-halogenated reagents by allowing a wider range of protic and aprotic solvents. Also, the heterogeneous nature of this oxidation procedure made the product isolation easy. The procedure presented here is very simple, fast, and oxidizes a wide variety of sulfides that were difficult to achieve by many N-halo reagents in the past.     

Cross-coupling reaction of alkyl halides with grignard reagents catalyzed by Ni, Pd, or Cu complexes with pi-carbon ligand(s)

Transition metal-catalyzed cross-coupling reactions of organic halides and pseudo-halides containing a C-X bond (X = I, Br, Cl, OTf, OTs, etc.) with organometallic reagents are among the most important transformations for carbon-carbon bond formation between a variety of sp, sp(2), and sp(3)-hybridized carbon atoms. In particular, researchers have widely employed Ni- and Pd-catalyzed cross-coupling to synthesize complex organic structures from readily available components. The catalytic cycle of this process comprises oxidative addition, transmetalation, and reductive elimination steps. In these reactions, various organometallic reagents could bear a variety of R groups (alkyl, vinyl, aryl, or allyl), but the coupling partner has been primarily limited to sp and sp(2) carbon compounds: alkynes, alkenes, and arenes. With alkyl coupling partners, these reactions typically run into two problems within the catalytic cycle. First, oxidative addition of alkyl halides to a metal catalyst is generally less efficient than that of aryl or alkenyl compounds. Second, the alkylmetal intermediates formed tend to undergo intramolecular beta-hydrogen elimination. In this Account, we describe our efforts to overcome these problems for Ni and Pd chemistry. We have developed new catalytic systems that do not involve M(0) species but proceed via an anionic complex as the key intermediate. For example, we developed a unique cross-coupling reaction of alkyl halides with organomagnesium or organozinc reagents catalyzed by using a 1,3-butadiene as the additive. This reaction follows a new catalytic pathway: the Ni or Pd catalyst reacts first with R-MgX to form an anionic complex, which then reacts with alkyl halides. Bis-dienes were also effective additives for the Ni-catalyzed cross-coupling reaction of organozinc reagents with alkyl halides. This catalytic system tolerates a wide variety of functional groups, including nitriles, ketones, amides, and esters. In addition, we have extended the utility of Cu-catalyzed cross-coupling reactions. With 1-phenylpropyne as an additive, Cu-catalyzed reactions of alkyl chlorides, fluorides, and mesylates with Grignard reagents proceed efficiently. These new catalytic reactions use pi-carbon ligands such as pi-allyl units or alkynes instead of heteroatom ligands such as phosphines or amines. Overall, these reactions provide new methodology for introducing alkyl moieties into organic molecules.     

Design and Synthesis of Chiral Zn2+ Complexes Mimicking Natural Aldolases for Catalytic C–C Bond Forming Reactions in Aqueous Solution

Extending carbon frameworks via a series of C–C bond forming reactions is essential for the synthesis of natural products, pharmaceutically active compounds, active agrochemical ingredients, and a variety of functional materials. The application of stereoselective C–C bond forming reactions to the one-pot synthesis of biorelevant compounds is now emerging as a challenging and powerful strategy for improving the efficiency of a chemical reaction, in which some of the reactants are subjected to successive chemical reactions in just one reactor. However, organic reactions are generally conducted in organic solvents, as many organic molecules, reagents, and intermediates are not stable or soluble in water. In contrast, enzymatic reactions in living systems proceed in aqueous solvents, as most of enzymes generally function only within a narrow range of temperature and pH and are not so stable in less polar organic environments, which makes it difficult to conduct chemoenzymatic reactions in organic solvents. In this review, we describe the design and synthesis of chiral metal complexes with Zn²⁺ ions as a catalytic factor that mimic aldolases in stereoselective C–C bond forming reactions, especially for enantioselective aldol reactions. Their application to chemoenzymatic reactions in aqueous solution is also presented.     

Pd2dba3/Bippyphos: A Robust Catalyst System for the Hydroxylation of Aryl Halides with Broad Substrate Scope

A mixture of tris(dibenzylideneacetone)dipalladium(0) (Pd₂dba₃) and 5‐(di‐tert‐butylphosphino)‐1′,3′,5′‐triphenyl‐1′H‐[1,4′]bipyrazole (Bippyphos) is shown to be a robust and efficient catalyst system for the hydroxylation of structurally diverse (hetero)aryl halides under mild conditions and with broad substrate scope. Included in this reactivity survey is the successful synthesis of substituted benzofurans and related heteroatomic derivatives, which are formed via the hydroxylation of 2‐haloalkynylarenes. Notably, a significant number of the reactions reported herein proceed at room temperature, and we have demonstrated that it is possible to conduct reactions on the benchtop under air using unpurified solvents with negligible loss in reactivity versus related transformations conducted under inert atmosphere conditions. We also report herein the first crystallographically characterized (Bippyphos)Pd(II) complex, which confirms the ability of this synthetically useful ligand to adopt a bidentate binding motif in a manner similar to Buchwald’s biarylphosphine ligand class.     

Visible Light instead of Transition Metal: Electron Donor Acceptor Complex Enabled Cross-Coupling of Aryl Halides with Active Methylene Compounds

An arylation of anions of active methylene compounds with aryl halides provides an access to synthetically versatile α-arylated 1,3-diketones, β-keto esters, β-keto nitriles, β-cyano esters, etc. Previously, these C−C cross-coupling reactions have been accomplished only using transition metal-based catalysts. Herein, we demonstrate that these arylations can be successfully realized under catalyst-free conditions employing the electron donor-acceptor (EDA) complex photoactivation strategy. The protocol was further optimized for a semi-one pot synthesis of indole derivatives via an intramolecular C−C coupling.     

Silicone as an organosilicon reagent for the palladium-catalyzed cross-coupling reaction

Silicone, poly(diorganosiloxane), serves as an organosilicon reagent for palladium-catalyzed cross-coupling reactions. Treatment of poly[(aryl)methylsiloxane], poly[(alkenyl)methylsiloxane], or cyclic oligosiloxanes with various aryl iodides in the presence of silver(I) oxide (Ag₂O) or tetrabutylammonium fluoride (TBAF) and a catalytic amount of palladium affords the corresponding cross-coupling product in a good to excellent yield. The reaction of silicone with aryl chlorides in the presence of K₂CO₃/H₂O as an activator proceeded to afford biaryl derivatives in moderate to excellent yields. A wide range of aryl chlorides bearing an electron-donating or electron-withdrawing substituent on the aromatic ring are tolerated.     

Metal–organic framework MOF-199-catalyzed direct and one-pot synthesis of thiols,sulfides and disulfides from aryl halides in wet polyethylene glycols (PEG 400)

A highly porous metal–organic frame work Cu₃ BTC₂ (copper(II)-benzene-1,3,5-tricarboxylate) that is known as MOF-199 was synthesized from the reaction of 1,3,5-benzenetricarboxylic acid and Cu(OAc)₂·H₂O by a solvothermal method and characterized by several techniques including FT-IR, XRD, EDX and scanning electron microscopy. The MOF-199 used as an efficient catalyst for one-pot synthesis of thiols by domino reactions of aryl halides and thiourea, and subsequently conversion to aryl alkyl sulfides and diaryl disulfides in polyethylene glycols (PEGs). A variety of aryl alkyl sulfides can be obtained in good to excellent yields in a relatively short reaction time and in the presence of the trace amount of catalyst. Also, the catalyst can be separated from the reaction mixture by decanting, and be reused without significant degradation in catalytic activity.