Rhodium-catalyzed asymmetric 1,4-addition of arylboron reagents to α,β-unsaturated esters

Reaction of arylboron reagents, arylboronic acids or arylborates, which are readily accessible by lithiation of aryl bromides followed by treatment with trimethoxyborane, with α,β-unsaturated esters in the presence of rhodium/(S)-binap catalyst proceeded with high enantioselectivity to give high yields of optically active β-aryl esters of up to 98% ee. The enantioselectivity depends on the steric bulkiness of the ester moiety.     

Metallomicelles of palladium(II) complexes as efficient catalysts for the Suzuki–Miyaura reaction in neat water

Metallomicelles of palladium(II) complex 4 are found to be an efficient catalyst for Suzuki–Miyaura reactions of aryl bromides substituted with a long alkyl chain and arylboronic acids at 80 °C in neat water. The reactions proceed smoothly to generate the corresponding biaryl compounds in moderate to excellent yields. Various biphenyl derivatives were successfully obtained by complex 4 catalysis of the Suzuki–Miyaura reactions in the absence of any surfactants in neat water. Copyright © 2013 John Wiley & Sons, Ltd.     

Azidosubstituted arylboronic acids: synthesis and Suzuki-Miyaura cross-coupling reactions

Arylboronic acids having a remote azido group were prepared from the corresponding azidosubstituted aryl bromides via lithiation and treatment with trialkyl borates. Preparative yields were achieved when the starting aryl bromides possessed ortho-alkoxy groups, which would stabilize the intermediate aryllithium species. Conventional Suzuki cross-coupling of the arylboronic acids proceeded generally well with retention of azido group; however, sometimes azidomethyl fragment underwent oxidative transformation into a nitrile.     

Ligand‐Free Suzuki Coupling Reaction Catalyzed by Pd/C in Microemulsion

Ligand‐free Suzuki reactions catalyzed by Pd/C can be efficiently performed in TX100 microemulsions. A number of aryl halides, including aryl iodides, bromides, and chlorides, were coupled with arylboronic acids smoothly and efficiently to produce good to excellent yields.     

18‐Crown‐6 promoting Pd/C‐catalyzed cross‐coupling reaction of aryl bromides and arylboronic acids in aqueous media

Pd/C‐catalyzed Suzuki–Miyaura cross‐coupling between aryl bromides and arylboronic acids in 50% methanol aqueous solution proceeded smoothly in the presence of 18‐crown‐6. Various aryl bromides bearing electron‐withdrawing groups and electron‐donating groups coupled with arylboronic acid in high yields. In addition, the catalyst could be recycled five times without loss of activity. Copyright © 2012 John Wiley & Sons, Ltd.     

trans-Pd(OAc)2(Cy2NH)2 catalyzed Suzuki coupling reactions and its temperature-dependent activities toward aryl bromides

A new catalytic system based on Pd-simple amines for Suzuki coupling reactions of aryl bromides is described. A well-defined air-stable complex, trans-Pd(OAc)₂(Cy₂NH)₂ effectively promotes Suzuki couplings of aryl bromides with a range of aryl boronic acids to give diaryl products in high yields. It also exhibits temperature-dependent activity toward aryl bromides bearing different electronic substituents under reaction conditions.     

Palladium Membrane‐Installed Microchannel Devices for Instantaneous Suzuki–Miyaura Cross‐Coupling

Instantaneous catalytic carbon–carbon bond‐forming reactions were achieved in catalytic membrane‐installed microchannel devices that have a polymeric palladium‐complex membrane. The catalytic membrane‐installed microchannel devices were provided inside the microchannels by means of coordinative and ionic molecular convolution at the interface between the organic and aqueous phases flowing laminarly, in which both non‐crosslinked linear polymer ligands and palladium species dissolved. The palladium‐catalyzed Suzuki–Miyaura reaction of aryl, heteroaryl, and alkenyl halides with arylboronic acids and sodium tetraarylborates was performed with the catalytic membrane‐installed microchannel devices to give quantitative yields of biaryls, heterobiaryls, and aryl alkenes within 5 s of residence time in the defined channel region. These microchannel devices were applied to the instantaneous allylic arylation reaction of allylic esters with arylboron reagents under microflow conditions to afford the corresponding coupling products within 1 s of residence time.     

Phosphine-free Suzuki cross-coupling reaction: a mild and selective method for the carbon–carbon bond formation in aqueous tea extract

A mild and selective protocol has been developed for the palladium-catalyzed phosphine-free Suzuki cross-coupling reaction of aryl bromides with arylboronic acids in aqueous tea extract at room temperature. It is noteworthy that the aqueous tea extract plays an important role in the reaction, and various functional groups are tolerated under the optimized conditions. The reactions proceeded with very good chemoselectivity in favor of the bromo instead of the chloro group even at higher temperatures. Furthermore, this protocol could be applied to the cross-coupling of 4-bromoindole without protecting the base sensitive amine group with arylboronic acids in moderate to excellent yields.     

低温Suzuki反应合成联苯及三联苯化合物

发展了一个低温下无配体钯催化溴代芳烃与芳基硼酸的Suzuki反应体系。该体系以醋酸钯为催化剂,无水碳酸钾为碱,乙醇水溶液为溶剂,无需加入任何配体,在0oC下即可高效催化溴代芳烃与芳基硼酸的Suzuki反应;反应的底物容忍性好,产品分离收率最高达97%。以溴代芳基N-甲基亚氨基二乙酸硼酸酯为砌块分子,通过调控反应温度,实现了砌块分子选择性Suzuki反应,从而一锅合成了不对称三联苯化合物,产品收率最高为81%。     

Oxygen-promoted PdCl2-catalyzed ligand-free Suzuki reaction in aqueous media

A simple and efficient protocol has been developed for the PdCl(2)-catalyzed ligand-free and aerobic Suzuki reaction of aryl bromides or nitrogen-based heteroaryl bromides with arylboronic acids in good to excellent yields in aqueous ethanol. A systematic investigation on the effect of different atmospheres on the reactivity of the palladium-catalyzed Suzuki reaction has been carried out, the results show that an aerobic atmosphere demonstrates a positive effect on the reactivity of the Suzuki reaction in an aqueous media and a negative effect in a pure organic solvent, which exhibits that the water plays a crucial role for the function of the atmosphere on the palladium-catalyzed ligand-free Suzuki reaction.     

Efficient salicylaldimine ligands for a palladium‐catalyzed Suzuki–Miyaura cross‐coupling reaction

A series of salicylaldimine ligands were designed to promote palladium‐catalyzed Suzuki–Miyaura cross‐coupling reaction. After a screening process, a ligand with a bulky 2,4‐di‐tert‐butyl substituent on the salicyaldehyde backbone and cyclohexylamine moiety was found to serve as a good combination for this reaction in aqueous solutions of DMF. The protocol demonstrated a significant advance in the efficiency of the cross‐coupling of aryl bromides and aryl chlorides with arylboronic acids to produce the desired biaryl products. Copyright © 2012 John Wiley & Sons, Ltd.     

Alcoholic solvent‐assisted ligand‐free room temperature Suzuki–Miyaura cross‐coupling reaction

We have observed the enhancing effect of alcoholic solvents in palladium‐catalysed ligand‐free Suzuki–Miyaura reactions. No extra additives or ligands are required for the Suzuki–Miyaura reaction of aryl bromides with arylboronic acids when we carried out the reaction in alcoholic or aqueous alcoholic solvents. Moreover, ethanol or aqueous ethanol is found to be a very good solvent for the Suzuki–Miyaura reaction involving electronically diverse aryl bromides and arylboronic acids under mild and ligand‐free conditions with low catalyst loading. It is observed from Hg(0) poisoning tests that the in situ generated palladium(0) species is the actual catalytic species for the reaction. Copyright © 2015 John Wiley & Sons, Ltd.     

Aqueous-phase, palladium-catalyzed cross-coupling of aryl bromides under mild conditions, using water-soluble, sterically demanding alkylphosphines

Sterically demanding, water-soluble alkylphosphines have been used in combination with various palladium salts in Suzuki, Sonogashira, and Heck couplings of aryl bromides under mild conditions in aqueous solvents. The tert-butyl-substituted ligands 2-(di-tert-butylphosphino)ethyltrimethylammonium chloride (t-Bu-Amphos) and 4-(di-tert-butylphosphino)-N,N-dimethylpiperidinium chloride (t-Bu-Pip-phos) in combination with palladium(II) salts were found to give catalysts that were significantly more active than catalysts derived from tri(3-sulfonatophenyl)phosphine trisodium (TPPTS). Suzuki couplings of unactivated aryl bromides occurred efficiently at room temperature in water/acetonitrile and water/toluene biphasic mixtures or in neat water. Notably, Suzuki couplings of hydrophilic aryl bromides gave high yields without using organic solvents for the reaction or purification. This methodology has been applied to a highly efficient synthesis of diflunisal. The catalyst derived from t-Bu-Amphos was recycled three times in Suzuki couplings in water/toluene before catalyst activity began to significantly drop. The average yield of four cycles was >80% per cycle. Heck and Sonogashira couplings were carried out under mild conditions (50 and 80 degrees C, respectively) with unactivated aryl bromides to give coupled products in high yield.     

Nation-Teflon bimembrane-supported palladium catalysts for Suzuki coupling reactions

Nation-Teflon bimembrane was used as an efficient support for the preparation and application of heterogeneous palladium catalysts.The supported palladium catalysts exhibit high activity and stability in the Suzuki cross-coupling of aryl bromides with arylboronic acids to afford the corresponding biaryls in good to excellent yields,and can be readily recovered and reused several times without significant loss of activity.     

Application of silicon-based cross-coupling technology to triflates

Aryl silatranes undergo fluoride-induced cross-coupling with aryl triflates to provide unsymmetrical biaryl derivatives in good to excellent yields. Silatranes also couple with aryl iodides and bromides, although the yields of adduct are lower than with the corresponding siloxane derivates. Aryl siloxanes (which had previously failed to couple with triflates) can be employed for triflate couplings using the Denmark modification, although the yields are lower than the corresponding silatrane reactions.     

Use of thallium(I) ethoxide in Suzuki cross coupling reactions

[reaction: see text]Thallium(I) ethoxide promotes Suzuki cross couplings for a range of vinyl- and arylboronic acids with vinyl and aryl halide partners in good to excellent yields. This reagent offers distinct advantages over thallium(I) hydroxide in terms of commercial availability, stability, and ease of use.     

氯化钯在氟化四丁基铵中当场生成纳米钯：一种高效、可回收的催化体系，在无配体和无溶剂条件下催化Suzuki-Miyaura反应

氯化钯在氟化四丁基铵中当场生成纳米钯,该钯催化剂在Suzuki-Miyaura交叉偶联反应中显示很高的催化效率。在氯化钯和氟化四丁基铵存在下,许多芳基卤代烃可以顺利与芳基硼酸发生偶联反应,得到中等到高的产率。此外,在Suzuki-Miyaura偶联反应中该氯化钯/氟化四丁基铵催化体系可以回收重复使用多次,并且芳基溴代烃可以在15-60分钟内反应完全。值得指出的是,该反应是在无溶剂、无配体和催化体系可回收重复使用的条件下进行的。这和无配体条件下TBAB中钯催化卤代芳烃与芳基硼酸的Suzuki-Miyaura交叉偶联反应方法。该氯化钯/氟化四丁基铵催化反应的反应机理也进行了讨论。     

Aryl bromide/triflate selectivities reveal mechanistic divergence in palladium-catalysed couplings; the Suzuki-Miyaura anomaly

In palladium-catalysed cross-coupling reactions, the outcome of competition between aryl bromides and aryl triflates depends on the nucleophilic partner; Suzuki couplings with R-B generally follow a different pattern from other R-M species.     

Efficient aqueous-phase Heck and Suzuki couplings of aryl bromides using tri(4,6-dimethyl-3- sulfonatophenyl)phosphine trisodium salt (TXPTS)

[reaction: see text] Sterically demanding, sulfonated arylphosphines TXPTS and TMAPTS have been applied to the aqueous-phase Heck and Suzuki coupling of aryl bromides. TXPTS provides good yields of Heck coupling products from aryl bromides at 80 degrees C, while both TMAPTS and TPPTS gave significantly less active catalysts. TXPTS is the first ligand to promote the aqueous-phase Heck coupling under such mild conditions. Both TXPTS and TMAPTS provide active catalysts for Suzuki couplings of aryl bromides at 50 degrees C.     

Highly active oxime-derived palladacycle complexes for Suzuki-Miyaura and Ullmann-type coupling reactions

Oxime-derived chloro-bridged palladacycles 12 and 13 are efficient complexes for the Suzuki-Miyaura reactions of aryl-, allyl-, and benzyl halides with arylboronic acids. The isolated catalysts are thermally stable, not sensitive to air or moisture, and easily accessible from inexpensive starting materials. The reaction can be performed under aerobic conditions with aryl bromides and chlorides, displaying turnover numbers (TON) of up to 5 x 10(5) and turnover frequencies (TOF) of up to 198 000 h(-1) for aryl bromides. Aryl chlorides undergo the Suzuki reaction with arylboronic acids with TON of up to 4700 and TOF up to 4700 h(-1). Even inexpensive and readily available benzyl and allyl chlorides undergo the coupling reaction with good turnover numbers. Complexes of 12 catalyze the syntheses of symmetrical biaryls in good yields via reductive coupling of iodoarenes in the presence of Hünig's base.