Microwave-assisted synthesis of pinacol boronates from aryl chlorides catalyzed by a palladium/imidazolium salt system

[reaction: see text] Aryl chlorides bearing electron-withdrawing groups react with bis(pinacol)borane 1 to give aryl boronates in good to excellent yields in the presence of a catalyst formed in situ from Pd(OAc)(2) and the imidazolium chloride 2. The reaction is greatly accelerated when carried out under microwave heating.     

Carbon-carbon and carbon-nitrogen coupling reactions catalyzed by palladium nanoparticles derived from a palladium substituted Keggin-type polyoxometalate

Palladium 15-20 nm particles stabilized by a Keggin-type polyoxometalate were prepared by reduction of K(5)PPdW(11)O(39) with H(2). The nanoparticles were shown to be effective catalysts for Suzuki-, Heck-, and Stille-type carbon-carbon coupling and carbon-nitrogen coupling reactions of bromoarenes in aqueous media. Chloroarenes were also reactive in reaction media without solvent. [reaction: see text]     

Cross-coupling reactions catalyzed by P, O chelate palladium complexes at room temperature

A new catalytic system based on P, O chelate palladium complexes for cross-coupling reactions is described. These catalysts have all shown high activity and selectivity under mild reaction condition.     

High stereoselectivity in chelation-controlled intermolecular Heck reactions with aryl chlorides, vinyl chlorides and vinyl triflates

Highly stereoselective chelation-controlled Pd(0)-catalyzed beta-arylations and beta-vinylations of a five-membered chiral, pyrrolidine-based vinyl ether were achieved using aryl- and vinyl chlorides as substrates, yielding quaternary 2-aryl/vinyl-2-methyl cyclopentanones in 89-96% ee under neutral reaction conditions.     

Suzuki-Miyaura cross-coupling reaction of aryl chlorides with aryl boronic acids catalyzed by a palladium dichloride adduct of N-diphenylphosphanyl-2-aminopyridine

One palladium dichloride adduct of a phosphine-pyridine ligand N-diphenylphosphanyl-2-aminopyridine (L₁) [(L₁)PdCl₂] (1) has been prepared and structurally characterized. Compound 1 can be used as an effective catalyst for the Suzuki-Miyaura cross-coupling reactions of unreactive aryl chlorides with aryl boronic acids, and worked much better than its mono- or bidentate phosphine ligands. The reactions with a wide scope of substrates proceeded to give desired products in good to excellent yields.     

An air-stable palladium/N-heterocyclic carbene complex and its reactivity in aryl amination

[reaction: see text] The synthesis and characterization of [Pd(IPr)Cl(2)](2) (1), an air- and moisture-stable complex, is reported. The utilization of 1 as a catalyst for amination of aryl chlorides and bromides with a variety of amine coupling partners under mild conditions is described. The amination reactions with 1 show a remarkable insensitivity to oxygen and water, and thus the amination reactions could be performed in air on the benchtop with undried reagent grade solvents and substrates with small effects on reaction times and conversions.     

Carbonylative Stille coupling reactions of benzyl chlorides with allyltributylstannane catalyzed by palladium nanoparticles

The carbonylative Stille coupling reaction of benzyl chlorides with allyltributylstannane was successfully conducted by using palladium nanoparticles as the catalyst under phosphine ligand-free conditions. The corresponding α,β-unsaturated ketone products were obtained in good to excellent yields.     

Cross-coupling of cyclopropyl- and cyclobutyltrifluoroborates with aryl and heteroaryl chlorides

Suitable conditions were found for the Suzuki-Miyaura cross-coupling reaction of potassium cyclopropyl- and cyclobutyltrifluoroborates with aryl chlorides. Both of these secondary alkyl trifluoroborates coupled in moderate to excellent yield with electron-rich, electron-poor, and hindered aryl chlorides to give a variety of substituted aryl cyclopropanes and cyclobutanes.     

Cross-coupling reactions of 1-alkenylboranes with 3,4-epoxy-1-butene catalyzed by palladium or nickel complexes

1-Alkenylboranes react with 3,4-epoxy-1-butene in the presence of palladium or nickel complexes to form the corresponding coupling products 2,5-alkadien-1-ol and 2-ethenyl-3-alken-1-ol, in high yields with in some cases high regioselectivity, and high turnover of the catalyst. The ratio of the two dienols can be reversed by changing the metal complex.     

Kumada coupling of aryl, heteroaryl, and vinyl chlorides catalyzed by amido pincer nickel complexes

A series of amido pincer complexes of nickel were examined for their catalysis in the Kumada cross-coupling reaction. The P,N,O-pincer nickel complexes tested are active catalysts for the cross-coupling of aryl, heteroaryl, and vinyl chlorides with aryl Grignard reagents. The reactions can proceed at room temperature and tolerate functional groups in aryl chlorides with the aid of LiCl and ZnCl(2) additives.     

纳米钯催化苄基氯代物与烯丙基硼酸频哪醇酯的羧化Suzuki偶联反应

CO2是廉价的C1源,同时具有无毒、储量丰富的优点, 符合绿色化学发展要求. 利用 CO2构筑新的 C–C 键是化学固定CO2的重要方法. Β,γ-不饱和酯类结构单元是许多生物活性分子的重要组成部分, 经由双π-烯丙基钯中间体与 CO2反应, 合成新的β,γ-不饱和酯类化合物, 具有重要意义. CO2与有机硼化合物的羧化反应已有报道, 有机硼化合物具有低毒、对水不敏感等优点. 但是已报道的羧化 Suzuki 偶联反应存在诸多缺点: (1) 需要使用含膦或者氮杂环卡宾配体的催化剂, 而这些催化剂的制备过程使前期实验步骤变得冗长, 同时反应液的酸化后处理过程也会造成环境污染; (2) 有机硼试剂的官能团兼容范围窄, 限制了底物范围的拓展. 本课题组以原位生成的纳米钯粒子为催化剂, 在 CO2存在的温和条件下, 高效实现了苄氯与烯丙基硼酸频哪醇酯的羧化 Suzuki 偶联反应. 反应过程中无其它配体加入, 反应结束后不需要酸化或酯化的后处理过程. 该反应将具有广泛的官能团兼容性.本文以 TBAB 稳定的纳米钯粒子为催化剂, 在温和条件下, 实现了氯甲基芳香化合物、烯丙基硼酸频哪醇酯和 CO2的三组分羧化 Suzuki 偶联反应. 最佳反应条件为: Pd(acac)2(5 mol%)、TBAB (0.7 mmol, 1.4 equiv.)、KF (1 mmol, 2.0 equiv.)、苄基卤代物 (0.5 mmol)、烯丙基硼酸频哪醇酯 (0.6 mmol, 1.2 equiv.)、CO2(2.0 Mpa)、溶剂 THF (5 mL), 50 oC 反应 24 h. 在最佳反应条件下, 苯环、萘环以及杂芳环的氯甲基化合物均可发生该羧化反应. 苯环上取代基的位置对产物的收率有影响. 当使用 1-溴甲基萘作为底物时反应也能够发生, 收率与 1-氯甲基萘作为底物时的收率相当. 与已报道有机硼试剂的羧化反应相比, 该反应体系无需加入配体, 原位生成了纳米钯粒子, 避免了催化剂或者配体的复杂制备过程. 该反应中, 氟离子的存在是必要的, 对烯丙基硼酸频哪醇酯具有活化作用.     

Efficient Negishi coupling reactions of aryl chlorides catalyzed by binuclear and mononuclear nickel-N-heterocyclic carbene complexes

We describe the first nickel-N-heterocyclic carbene catalyzed Negishi cross-coupling reaction of a variety of unactivated aryl chlorides, heterocyclic chlorides, aryl dichlorides, and vinyl chloride. The mononuclear and binuclear nickel-NHC complexes supported by heteroarene-functionalized NHC ligands are found to be highly efficient for the coupling of unactivated aryl chlorides and organozinc reagents, leading to biaryls and terphenyls in good to excellent yields under mild conditions. For all aryl chlorides, the binuclear nickel catalysts show activities higher than those of mononuclear nickel complexes because of possible bimetallic cooperative effect.     

Solvent free amination reactions of aryl bromides at room temperature catalyzed by a (pi-allyl)palladium complex bearing a diphosphinidenecyclobutene ligand

An air- and moisture-stable (pi-allyl)palladium complex bearing a unique diphosphinidenecyclobutene ligand effectively catalyzes amination reactions of aryl bromides with amines, where the reactions proceed under mild conditions without solvent, with 2 mol % of catalyst and 1 equiv of t-BuOK at room temperature. Under these conditions the amination products were obtained in good to excellent isolated yields.     

A palladium Chugaev carbene complex as a modular, air-stable catalyst for Suzuki-Miyaura cross-coupling reactions

A new Chugaev-type palladium carbene complex was prepared via a convenient metal-templated route and fully characterized by X-ray crystallography, NMR, and IR. This complex proved effective as a precatalyst for Suzuki-Miyaura cross-coupling reactions of a range of aryl bromides, even under aerobic conditions, and its modular synthesis should allow for further catalyst fine-tuning.     

Microwave-assisted palladium-catalyzed cross-coupling of aryl and vinyl halides with H-phosphonate diesters

A general and efficient method for the microwave-assisted formation of the C-P bond was developed. Using a prevalent palladium catalyst, Pd(PPh3)4, a quantitative cross-coupling of various H-phosphonate diesters with aryl and vinyl halides was achieved in less than 10 min. The reactions occurred with retention of configuration at the phosphorus center and in the vinyl moiety. Using this protocol, several C-phosphonates, including those bearing nucleoside and cholesteryl moieties, were prepared in high yields.     

Suzuki–Miyaura coupling reactions of aryl chlorides catalyzed by a new nickel(II) σ‐aryl complex

A new nickel(II) σ‐aryl complex, trans‐chloro(9‐phenanthrenyl)bis(triphenylphosphine)nickel(II), was used as a precatalyst for the Suzuki–Miyaura coupling reactions of aryl chlorides. The catalytic conditions were optimized by investigating the cross‐coupling of p‐chloroanisole with phenylboronic acid. The results show that this complex is efficient for both electron‐rich and electron‐deficient aryl chlorides, though it gives better yields for activated arylboronic acids than deactivated ones. All isolated cross‐coupled biaryl products have been characterized by ¹H and ¹³C NMR, and their spectral data are consistent with those reported. Side products from the coupling of arylboronic acid with the precatalyst complex have also been isolated and characterized, which is helpful for understanding the coupling mechanism. Copyright © 2013 John Wiley & Sons, Ltd.