Efficient copper-free Sonogashira coupling of aryl chlorides with palladium on charcoal

Palladium on charcoal serves as an efficient and reusable solid supported catalyst for the Sonogashira coupling of aryl chlorides with terminal acetylenes in the presence of a bulky, electron-rich biphenyl type ligand (XPhos), without copper co-catalyst.     

Sonogashira coupling of aryl halides catalyzed by palladium on charcoal

With the proper choice of solvent, palladium on charcoal acts as an efficient catalyst in the Sonogashira cross-coupling reaction of aryl bromides. The catalytically active species in the process is probably palladium, which leaches into the solution but returns onto the surface of the charcoal at the end of the reaction.     

Sonogashira reaction of aryl halides with propiolaldehyde diethyl acetal catalyzed by a tetraphosphine/palladium complex

All-cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ efficiently catalyzes the Sonogashira reaction of propiolaldehyde diethyl acetal with a variety of aryl bromides and chlorides. A minor electronic effect of the substituents of the aryl bromide was observed. Similar reaction rates were observed in the presence of activated aryl bromides such as 4-trifluoromethylbromobenzene and deactivated aryl bromides such as bromoanisole. Turnover numbers up to 95,000 can be obtained for this reaction. Even aryl chlorides and heteroarylbromides or chlorides have been successfully alkynylated with this catalyst. Moreover, a wide variety of substituents on the aryl halide such as fluoro, trifluoromethyl, acetyl, benzoyl, formyl, nitro, dimethylamino or nitrile are tolerated.     

高效可循环离子型钯配合物催化羰化Sonogashira反应

炔酮类化合物作为一类具有生物活性的分子,是天然产物全合成中构建杂环类化合物的重要中间体.炔酮类化合物的传统合成方法是通过过渡金属催化金属有机炔烃和酰氯的交叉偶联,但存在酰氯本身稳定性和底物官能团耐受力较差的缺点.近年来,钯催化的羰化Sonogashira反应(末端炔烃和芳基卤化物与CO的偶联反应)成为合成炔酮类化合物更为直接和有效的方法,其中与钯中心原子配位的配体的电子效应和空间效应可显著调控钯配合物的催化性能.但均相钯催化的羰化Sonogashira反应体系存在催化剂流失、分离困难和难以循环使用的问题.我们以2-(1-咪唑基)噻唑为母体分子,合成了具有P,S,N杂合配体特征的配体L1,同时将配体L1通过与MeOTf的季铵化反应得到相应的离子型膦配体L2.在此基础上,利用L1和L2与过渡金属中心的配位作用合成相应的钯配合物1A和2A.由于L1和L2中含有多种不同配位能力的配体(P-配体,S-配体和/或N-配体),故通过N/S杂原子对Pd-中心原子的协同弱配位作用,可以调变相应钯配合物对羰化Sonogashira反应的催化性能.另外,2A中具有强吸电子效应的正电荷的存在,使其结构和催化性能也必然不同于中性配合物1A.实验结果表明,在温和的反应条件(90℃,lh,CO压强1.0 MPa)下,对于碘苯和苯乙炔的羰化Sonogashira偶联反应,1A体现出优于2A的催化性能,TOF值达到840 h-1;但反应温度提高到120℃时,1A的TOF高达3560 h-1,2A的TOF为2960 h-1.与L1的2JP-Se=744 Hz相比,L2的2JP-Se=768 Hz,说明L2中具有吸电子效应的正电荷的存在降低了相应P原子的σ给电子能力(2JP-Se数值越大,相应膦配体的6给电子能力越弱);同时,1A中具有弱配位能力的N配体的缺失削弱了配体对Pd活性中心的稳定作用.在底物普适性研究中发现,4-硝基溴苯在相同反应条件下几乎得不到羰化Sonogashira偶联产物.而将反应体系中的CO换为同样压强下的N2,却可以顺利实现Sonogashira偶联反应.我们推测,在CO氛围下形成的pd0-CO活性物种(与N2氛围下形成的Pd0活性物种相比)具有相对较低的对底物的氧化加成能力.离子型钯配合物2A的优势在于,当将其与室温离子液体[Bmim]PF6(溶剂)结合使用,在2A催化碘苯与苯乙炔的羰化Sonogashira偶联反应过程中,循环使用8次催化性能没有明显下降.     

Enhanced catalyst recovery in an aqueous copper-free Sonogashira cross-coupling reaction

We report the synthesis of a superparamagnetic nanoparticle MNP (γ-Fe(2)O(3)/polymer) supported dendritic catalyst based on a bulky electron-rich phosphine Pd(II) complex. The high reactivity of this catalyst is described in a copper-free Sonogashira C-C cross-coupling reaction in water, and the significant role of surfactant additives is highlighted in the recovery study.     

A copper-free Sonogashira coupling reaction in ionic liquids and its application to a microflow system for efficient catalyst recycling

[reaction: see text] The PdCl2(PPh3)2-catalyzed Sonogashira coupling reaction, in good to high yields, was performed in an ionic liquid ([BMIm][PF6]) in the absence of a copper salt. The use of an ionic liquid allows for the facile separation and recycling of the catalyst. The application of the above reaction in a microflow system in conjunction with an IMM micromixer was also successful.     

水溶性氮杂环卡宾钯金属配合物催化的Sonogashira反应

成功合成了一种磺酸钠基团官能团化的水溶性氮杂环卡宾钯金属配合物。在无膦、以水作溶剂的反应条件下,这种水溶性卡宾钯金属配合物能高效催化碘代芳烃和端基炔烃的Sonogashira偶联反应,反应结束后,可以通过萃取的方式把催化剂从反应混合物中分离出来,该催化剂可以重复循环使用四次。     

A general and efficient copper catalyst for the amidation of aryl halides

An experimentally simple and inexpensive catalyst system was developed for the amidation of aryl halides by using 0.2-10 mol % of CuI, 5-20 mol % of a 1,2-diamine ligand, and K(3)PO(4), K(2)CO(3), or Cs(2)CO(3) as base. Catalyst systems based on N,N'-dimethylethylenediamine or trans-N,N'-dimethyl-1,2-cyclohexanediamine were found to be the most active even though several other 1,2-diamine ligands could be used in the easiest cases. Aryl iodides, bromides, and in some cases even aryl chlorides can be efficiently amidated. A variety of functional groups are tolerated in the reaction, including many that are not compatible with Pd-catalyzed amidation or amination methodology.     

Sonogashira reaction of aryl and heteroaryl halides with terminal alkynes catalyzed by a highly efficient and recyclable nanosized MCM-41 anchored palladium bipyridyl complex

A heterogeneous catalyst, nanosized MCM-41-Pd, was used to catalyze the Sonogashira coupling of aryl and heteroaryl halides with terminal alkynes in the presence of CuI and triphenylphosphine. The coupling products were obtained in high yields using low Pd loadings to 0.01 mol%, and the nanosized MCM-41-Pd catalyst was recovered by centrifugation of the reaction solution and re-used in further runs without significant loss of reactivity.     

Rapid, easy copper-free Sonogashira couplings using aryl iodides and activated aryl bromides

We present here an easy, rapid copper-free methodology for the Sonogashira coupling reaction. It works well for a range of aryl iodides and activated aryl bromides.     

Highly efficient cyclopalladated ferrocenylimine catalyst for Suzuki cross-coupling reaction of 3-pyridylboronic pinacol ester with aryl halides

The Suzuki cross-coupling reaction of 3-pyridylboronic pinacol ester with aryl iodides, bromides and chlorides was carried out in DMF/H₂O (3/1, v/v) at 110 °C in the presence of cyclopalladated ferrocenylimine I and K₂CO₃ or CsCO₃ (1.0 equiv.) without the protection of inert gas. By using this method the synthesis of 3-pyridyl biaryl compounds could be readily achieved.     

Heck reaction of aryl halides with linear or cyclic alkenes catalysed by a tetraphosphine/palladium catalyst

cis,cis,cis-1,2,3,4-Tetrakis(diphenylphosphinomethyl)cyclopentane/[PdCl(C₃H₅)]₂ system catalyses efficiently the Heck reaction of aryl halides with linear alkenes such as pent-1-ene, oct-1-ene or dec-1-ene. Selectivities up to 70% in favour of E-1-arylalk-1-ene isomers can be obtained. In the presence of cyclic alkenes the selectivities of the reactions strongly depends on the ring size. Addition to cyclohexene or cycloheptene led mainly to 1-arylcycloalk-3-ene derivatives. On the other hand, addition to cyclooctene led to 1-arylcycloalk-1-ene adducts.     

Dimethylaminoalkyl chalcogenolate palladium(II) complexes as an efficient copper- and phosphine-free catalyst for Sonogashira reaction

N,N-Dimethylaminoalkyl chalcogenolate Pd(II) complexes [PdCl(E^∩NMe₂)]_n has been investigated as a moisture/air-stable and robust catalyst for Sonogashira cross-coupling reaction in the absence of copper and phosphine ligand. The dimeric palladium(II) complex of selenium containing ligand shows the best catalytic activity as compared with monomeric and trimeric complexes. The variety of functional groups are tolerated under optimized catalytic systems and provide excellent yields of the products.     

Monodentate phosphorus-coordinated palladium(Ⅱ)complexes as new catalyst for Mizoroki-Heck reaction of aryl halides with electron-deficient olefins

Four novel monodentate phosphorus-coordinated palladium(Ⅱ) complexes derived from 3,5-disubstituted-1H-1,2,4-diazaphospholes were developed as efficient catalyst for Mizoroki-Heck reactions of aryl halides with electron-deficient olefins. The role of these monophosphine ligands in catalysis was illustrated by control experiments using Pd salt and ligands as combined catalyst.     

A highly efficient catalyst for Suzuki coupling of aryl halides and bromoarylphosphine oxides

The biphenyl-based phosphine, P(o-C₆H₄C₆H₄Me)Ph₂, is a moderately bulky and electron-rich phosphine, which has been successfully applied to the palladium catalyzed Suzuki coupling of activated and deactivated aryl halides as well as bromoarylphosphines and bromoarylphosphine oxides, with low catalyst loading and good to excellent conversions and turnovers.     

An efficient palladium catalytic system for microwave assisted cyanation of aryl halides

Application of a new catalytic system for cyanation reaction of various aryl halides using K₄[Fe(CN)₆] as cyanating source was examined. The reactions were performed under microwave irradiation and results showed that application of this catalytic system and DMF at 130 °C minimized the reaction times from hours to minutes in good to excellent yields.     

Heterogeneous copper-free Sonogashira coupling reaction catalyzed by a reusable palladium Schiff base complex in water

Heterogeneous Sonogashira coupling of terminal alkynes with aryl halides was studied over a polymer-supported macrocyclic Schiff base palladium complex. The cross-coupling reaction proceeded smoothly by adding a piperidine in water medium. The catalyst exhibited effective catalytic activities to afford the corresponding products in good to excellent yields under copper-free conditions. Furthermore, the catalyst could be easily recovered and reused for several times without a significant loss of its activity.     

Palladium-tetraphosphine complex: an efficient catalyst for the coupling of aryl halides with alkynes

The cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)-cyclopentane-[PdCl(eta3-C3H5)]2 system catalyses the coupling of aryl halides with alkynes with very high ratios of substrates-catalyst in good yields; a turnover number of 2600000 can be obtained for the reaction of 4-trifluoromethylbromobenzene with phenylacetylene in the presence of this catalyst.     

Bi- and trinuclear oxalamidinate complexes of palladium as catalysts in the copper-free Sonogashira reaction and in the Negishi reaction

The binuclear complex [(acac)Pd(oxam)Pd(acac)] 1 (oxam: tetraphenyl oxalic amidinate) has been prepared from H₂oxam and Pd(acac)₂ in excellent yield. The complex was characterized by elemental analyses, mass spectroscopy, ¹H NMR, ¹³C NMR spectroscopy and in the solid state by X-ray single crystal diffraction analyses. 1 consists of a bimetallic centrosymmetric unit in which the planar oxam ligand acts in a bis-chelating fashion. Each palladium center is in a planar environment.The complex 1 acts as highly selective pre-catalyst in the copper-free Sonogashira reaction between 4-bromoacetophenone and phenylacetylene. Its long-time catalytic activity is higher than that of the related binuclear complex 2 (oxam: tetra-p-tolyl oxalic amidinate) or that of the trinuclear compound [(acac)Pd(oxam)Zn(oxam)Pd(acac)] (3), the solid-state structure of which was also determined by an X-ray structural analysis of single crystals. In addition, 2 is an active and extremely selective pre-catalyst for the Negishi reaction between 3,5,6,8-tetrabromophenanthroline and R-CC-ZnCl (R: Ph, (ⁱprop)₃Si) to form tetra-alkyne-substituted derivatives.