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。     

Pyridin‐, Quinolin‐ and Acridinylidene Palladium Carbene Complexes as Highly Efficient C–C Coupling Catalysts

A series of four new complexes bearing N‐heterocyclic carbene ligands (NHCs) as well as four compounds bearing N‐heterocyclic carbene ligands with remote heteroatoms (rNHCs) of the general types [(NHC)(PPh₃)₂PdCl]⁺BF₄⁻ and [(rNHC)(PPh₃)₂PdCl]⁺BF₄⁻, respectively, have been prepared in high yields. Crystal and molecular structures have been determined for four representative examples. These compounds proved to be efficient catalysts for aryl coupling reactions of the Heck and Suzuki types (reaching TONs of as high as 6,200,000). Both aryl bromides and aryl chlorides can be used as substrates. Like the well known mixed, standard (NHC)(phosphine) compounds, the new six‐numbered, one‐N‐heterocyclic carbene complexes (and in particular certain rNHC‐containing ones) also combine the advantageous stability of bis(carbene) and the high activity of bis(phosphine) complexes. Furthermore, their good catalytic performance and, especially, their easy synthesis based on cheap and commercially available starting materials, make them by far superior when compared to the mixed (NHC)(phosphine) catalysts known thus far.     

3，5-二溴-2，6-双（2’-嗯唑啉基）苯基钯（Ⅱ）钳型物的合成及其催化Suzuki反应

以4,6-二溴间苯二甲酸为起始原料,经过酰化、氨解、氯化以及成环反应生成配体4,6-二溴-1,3一双（2’-嗯唑啉基）苯。后者先与醋酸钯作用后经离子交换最终得到对应的钳形化合物氯化[3,5-二溴-2,6-双（2’-嗯唑啉基）]苯基钯（Ⅱ）。考察了该钳形化合物催化取代芳氯与苯硼酸的偶合反应。结果表明：除对氯苯胺外,其余各取代芳氯与苯硼酸的偶合均得到较高偶合收率,且带供电子基团的氯苯与苯硼酸的偶合收率要高于吸电子基团氯苯的偶合收率,这可能与钳形化合物中溴的吸电子性能有关。     

The development of versatile methods for palladium-catalyzed coupling reactions of aryl electrophiles through the use of P(t-Bu)3 and PCy3 as ligands

Metal-catalyzed coupling reactions of aryl electrophiles with organometallics and with olefins serve as unusually effective tools for forming new carbon-carbon bonds. By 1998, researchers had developed catalysts that achieved reactions of aryl iodides, bromides, and triflates. Nevertheless, many noteworthy challenges remained; among them were couplings of aryl iodides, bromides, and triflates under mild conditions (at room temperature, for example), couplings of hindered reaction partners, and couplings of inexpensive aryl chlorides. This Account highlights some of the progress that has been made in our laboratory over the past decade, largely through the appropriate choice of ligand, in achieving these synthetic objectives. In particular, we have established that palladium in combination with a bulky trialkylphosphine accomplishes a broad spectrum of coupling processes, including Suzuki, Stille, Negishi, and Heck reactions. These methods have been applied in a wide array of settings, such as natural-product synthesis, materials science, and bioorganic chemistry.     

Highly Active,Well‐Defined (Cyclopentadiene)(N‐heterocyclic carbene)palladium Chloride Complexes for Room‐Temperature Suzuki–Miyaura and Buchwald–Hartwig Cross‐Coupling Reactions of Aryl Chlorides and Deboronation Homocoupling of Arylboronic Acids

A new class of well‐defined N‐heterocyclic carbene (NHC)‐(cyclopentadiene)palladium chloride complexes such as CpPd(NHC)Cl wasw synthesized from the readily available starting NHC‐palladium(II) chloride dimers. These air‐stable, coordinatively saturated NHC‐Pd complexes bearing the cyclopentadiene (Cp) unit exhibit high catalytic activity in the room temperature Suzuki–Miyaura and Buchwald–Hartwig cross‐coupling reactions involving unactive aryl chlorides as the substrates. In addition, they are found to be extremely efficient catalysts in the deboronation homocoupling of arylboronic acids at room temperature.     

氯代芳烃偶联反应中钯催化剂的研究进展

在合适的钯催化作用下,可将廉价易得、低活性的氯代芳烃应用于C—C键和C杂键形成的偶联反应。对偶联反应用钯催化剂的研究进行了综述。通过选择合适的配体,钯催化剂可有效地催化带有多种体取代基的氯代芳烃或氯代杂芳烃,发生Suzuki、Negishi、Stille和Heck等多种偶联反应,获得较高的收率和很高的选择性。     

Hybrid Organic‐Inorganic Materials from Di‐(2‐pyridyl)methylamine‐Palladium Dichloride Complex as Recoverable Catalysts for Suzuki,Heck and Sonogashira Reactions

Hybrid silica materials containing the di‐(2‐pyridyl)methylamine‐palladium dichloride complex, prepared by sol‐gel cogelification, are efficient recyclable catalysts for Suzuki (aryl bromides and chlorides), Heck (aryl bromides) and Sonogashira reactions (aryl iodides and bromides). Formation of palladium(0) nanoparticles is observed in the Suzuki and Heck reactions but not in the Sonogashira 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。     

High-turnover aminopyridine-based Pd-catalysts for Suzuki–Miyaura reaction in aqueous media

A high-turnover catalytic system based on commercially available aminopyridines (L) and PdCl₂ has been developed for Suzuki–Miyaura reaction in aqueous media. Reactions of arylboronic acids with a wide range of aryl iodides, bromides and chlorides proceeded in the presence of these catalysts for a short time in aqueous media to afford the cross-coupling products in high yields. Furthermore, this protocol allows tolerating a wide range of functional groups.     

Palladium Nanoparticles in Suzuki Cross‐Couplings: Tapping into the Potential of Tris‐Imidazolium Salts for Nanoparticle Stabilization

Inspired by the proclivity of various palladium sources to form nanoparticles in imidazolium‐based ionic liquids, we now report that tris‐imidazolium salts bearing hexadecyl chains and a bridging mesitylene moiety are potent stabilizers of palladium nanoparticles efficiently prepared via a Chaudret‐type hydrogenation of the bis(dibenzylideneacetone)palladium(0). The palladium nanoparticles have been isolated in pure form and characterized by ¹H nuclear magnetic resonance, transmission electron microscopy, electron diffraction and dynamic light scattering. The new materials proved effective in Suzuki cross‐coupling at a loading of 0.2% palladium. Thus, using a tris‐imidazolium iodide‐palladium material, a series of biaryl products has been prepared starting from aryl bromides and some activated chlorides. The possibility that this catalytic activity might be due to the formation of palladium N‐heterocyclic carbenes has been addressed through solid state ¹³C NMR and the synthesis of an imidazolium analogue in which the acidic 2‐H was replaced with a methyl group.     

Synthesis of Well‐Defined Diphenylvinyl(cyclopropyl)phosphine‐Palladium Complexes for the Suzuki–Miyaura Reaction and Buchwald–Hartwig Amination

The well‐defined diphenylvinylphosphine‐palladium complex 1 and the diphenylcyclopropylphosphine‐palladium complex 2 were successfully synthesized. The crystal structures of these complexes were obtained by X‐ray crystallographic analysis. Both complexes were air‐ and moisture‐stable, and could be prepared on a gram scale. These palladium complexes catalyzed the Suzuki–Miyaura reaction of aryl bromides [turnover numbers (TON) up to 196,000] and aryl chlorides (TON up to 50,000). Furthermore, complex 2 catalyzed the Buchwald–Hartwig amination of aryl chlorides and aromatic/aliphatic amines with a low catalyst loading. These complexes showed different reactivities for the coupling of 2‐chloropyridine, and the origin of this difference is discussed.     

Synthesis and characterization amino-salicylaldimine palladium-based complexes and their Suzuki coupling reaction study

A series of amino-salicylaldimine ligands, 5-R-3-morpholinomethyl-salicylaldimine (R = t-Bu, CH₃, Br) have been synthesized and structurally analyzed. These tridentate ligands add to palladium (II) to give high yields of air-stable complexes that are characterized by IR, ¹H NMR and elemental analysis. Crystal structure details of complex 1 are presented. These Pd (II) complexes with amino-salicylaldimine ligands are versatile and efficient Suzuki catalysts towards cross-coupling of a variety of aryl chlorides with phenylboronic acid using DMF as solvent.     

Recoverable Palladium Catalysts for Suzuki–Miyaura Cross‐ Coupling Reactions Based on Organic‐Inorganic Hybrid Silica Materials Containing Imidazolium and Dihydroimidazolium Salts

The systems formed by palladium acetate [Pd(OAc)₂] and hybrid silica materials prepared by sol‐gel from monosilylated imidazolium and disilylated dihydroimidazolium salts show catalytic activity in Suzuki–Miyaura cross‐couplings with challenging aryl bromides and chlorides. They are very efficient as recoverable catalysts with aryl bromides. Recycling is also possible with aryl chlorides, although with lower conversions. In situ formation of palladium nanoparticles has been observed in recycling experiments.     

Suzuki–Miyaura Reactions of Aryl Chloride Derivatives with Arylboronic Acids using Mesoporous Silica‐Supported Aryldicyclohexylphosphine

The Suzuki–Miyaura reactions using mesoporous‐supported aryldicyclohexylphosphine as ligand have been investigated. The catalysts were based on SBA‐15 type mesoporous silica which was transformed in a four‐step synthesis leading to a phosphine‐containing hybrid material The most productive catalytic system studied was generated in situ from this material and the homogeneous palladium complex, Pd(OAc)₂. Other catalytic systems were studied for comparison [homogeneous cataysts, a “preformed” catalyst obtained by reaction of PdCl₂(PhCN)₂ and the phosphine‐containing material]. Variations involving the solvent system, the substrate aryl chloride and the arylboronic acid reactant were also studied. For both in situ and preformed catalyst systems, high conversions and yields are obtained for activated aryl chlorides. Success of the reaction for unactivated aryl chlorides was limited to the catalyst formed in situ. The catalyst formed in situ was also shown to be reactive under aqueous reaction conditions in the cross‐coupling of 1‐(4‐chlorophenyl)ethanone with phenylboronic acid.     

Expanded Heterogeneous Suzuki–Miyaura Coupling Reactions of Aryl and Heteroaryl Chlorides under Mild Conditions

A mesoporous LTA zeolite (MP‐LTA)‐supported palladium catalyst was developed for the highly efficient Suzuki–Miyaura reaction of aryl and heteroaryl chlorides. The couplings of various aryl chlorides with arylboronic acids in aqueous ethanol were efficiently achieved in the presence of 1.0 mol% of the catalyst. Furthermore, the scope of this catalyst was extended to the coupling of heteroaryl chlorides. Regardless of the substituents, all of the coupling reactions were very clean and highly efficient under mild heating. It shows that our catalyst is one of the most powerful heterogeneous catalysts for the coupling of a wide range of aryl and heteroaryl chlorides. The catalyst could be repetitively used at least 10 times without a significant loss of its catalytic activity. Compared to mesoporous SBA‐15 and MCM‐41 materials, the MP‐LTA support proved to be very stable and robust to prevent degradation upon reuse.     

Enantiomerically Pure Cyclopropane Building Blocks: Synthesis and Transformations of 2‐Iodocyclopropylboronic Esters

Enantiomerically pure 2‐iodocyclopropylboronic esters 6 and 8 have been synthesized from the readily available allylic alcohol 2 via an oxidation‐radical decarboxylation sequence. These unique building blocks have been demonstrated to be versatile intermediates for a consecutive Suzuki‐coupling with aryl‐, heteroaryl‐, alkenyl‐, and cyclopropylboron derivatives (1 example each).     

A Highly Practical and Reliable Nickel Catalyst for Suzuki–Miyaura Coupling of Aryl Halides

We disclose that [1,3‐bis(diphenylphosphino)methane]nickel(II) chloride [NiCl₂(dppp)] is a highly active, universally applicable, cheap, and stable catalyst for Suzuki–Miyaura cross‐coupling reactions of aryl halides with a catalyst loading of lower than 1 mol%, and more notably, in the absence of extra supporting ligands. Under the optimized reaction conditions, a broad range of aryl bromides as well as the notoriously unreactive aryl chlorides, including activated, non‐activated, deactivated, and heteroaromatic and sterically hindered substrates can be coupled smoothly with various boronic acids (47 examples, 48–98% yields). In addition, the transformation is tolerant of various functional groups such as ether, ester, ketone, aldehyde, cyano, and unprotected amino and hydroxy groups. Finally, the potential utilization of the methodology was further demonstrated by the gram‐scale synthesis of several core structures of commercialized antihypertensive drugs and fungicides. Thus, the combination of high activity, broad applicability, cheapness, and high stability of NiCl₂(dppp) presented in this work constitutes one of the few prominent catalysts which allow for practical and reliable construction of biaryls and heterobiaryls with structural diversity from readily available aryl halides and boronic acids.     

Oxime‐Derived Palladium Complexes as Very Efficient Catalysts for the Heck–Mizoroki Reaction

Oxime‐derived, chloro‐bridged palladacycles 16 are efficient complexes for the Heck vinylation of aryl halides. 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 iodides, bromides and chlorides with acrylic esters and olefins displaying turnover numbers (TON) of up to 10¹⁰ for phenyl iodide and turnover frequencies (TOF) of 1.4×10⁸ h⁻¹. Deactivated aryl bromides undergo the Heck reaction with styrene with TON and TOF values up to 97,000 and 6063 h⁻¹, respectively. Even aryl chlorides undergo the coupling reaction with olefins with TON up to 920. Complexes 16 catalyze the synthesis of 2,3‐disubstituted indenones and indoles in good yields via annulation reaction of internal alkynes with o‐bromo‐ or o‐chlorobenzaldehyde and o‐iodoaniline, respectively.     

Aerobic Ligand‐Free Suzuki Coupling Reaction of Aryl Chlorides Catalyzed by In Situ Generated Palladium Nanoparticles at Room Temperature

An aerobic, ligand‐free Suzuki coupling reaction catalyzed by in situ generated palladium nanoparticles in polyethylene glycol with an average molecular weight of 400 Da (PEG‐400) at room temperature has been developed. This catalytic system is a very simple and highly active protocol for the Suzuki coupling of aryl chlorides with arylboronic acids, which proceed smoothly in excellent yields in short times using low catalyst loadings. Control experiments demonstrated that the Suzuki reaction catalyzed by the in situ generated palladium nanoparticles can be carried out much quicker than that using the preprepared particles under the same conditions. The formation of palladium nanoparticles in PEG‐400 was promoted by arylboronic acids.     

Synthesis of 1-Substituted Fluorenones

A convenient and scalable synthesis of a range of 1-substituted fluorenones from readily available starting materials is described. Through the use of either a Suzuki process, benzyne chemistry, or the Hoffmann rearrangement, a range of different 1-substituted fluorenones (fluoro, chloro, bromo, iodo, methoxy, cyano, amino, phenyl, and hydroxy) were prepared on a multigram scale using robust and readily reproducible chemistry.