Asymmetric Suzuki-Miyaura Cross-coupling Research Articles

Construction of axially chiral 2-arylpyrroles using catalytic asymmetric Suzuki-Miyaura cross-coupling: an efficient approach to esaxerenone.

A general and efficient method has been developed to access axially chiral 2-arylpyrroles using catalytic asymmetric Suzuki-Miyaura cross-coupling. A wide range of axially chiral arylpyrroles were obtained in high yields with good to excellent enantioselectivities. The key to success is the use of a combined catalytic system involving a palladium catalyst and chiral ferrocene diphosphine ligand for achieving effective enantiocontrol. More importantly, this axially chiral CF3-substituted 2-arylpyrrole serves as a key intermediate in the preparation of the anti-hypertensive and diabetic nephropathy drug esaxerenone. It was directly asymmetrically synthesized with high enantioselectivity (92% ee). Thus, a new strategy is provided for the catalytic asymmetric synthesis of esaxerenone.

Development of a chiral TPr# ligand and application for asymmetric palladium and copper catalysis

We report the design and synthesis of chiral triazolylidene-metal complexes with bulky substituents at the triazole ring. The palladium complex could be applied to the asymmetric Suzuki-Miyaura cross coupling reaction of 1-naphthaleneboronic acid and 1-bromo-2-methoxynaphthalene to afford the coupling product with good enantioselectivity. The reaction was found to proceed even at 10 mol ppm catalyst loading, leading to high turnover numbers of up to 2300. The chiral triazolylidene-copper complex was employed as an asymmetric catalyst for the borylation of methyl cinnamate to provide the borylated product with good enantioselectivity.

Developing Biarylhemiboronic Esters for Biaryl Atropisomer Synthesis via Dynamic Kinetic Atroposelective Suzuki-Miyaura Cross-Coupling.

We herein introduce biarylhemiboronic esters as a new type of bridged biaryl reagent for asymmetric synthesis of axially chiral biaryl structures, and the palladium-catalyzed asymmetric Suzuki-Miyaura cross-coupling of biarylhemiboronic esters is developed. This dynamic kinetic atroposelective coupling reaction exhibits high enantioselectivity, good functional group tolerance, and a broad substrate scope. The synthetic application of the current method was demonstrated by transformations of the product and a programmed synthesis of chiral polyarene. Preliminary mechanistic studies suggested that the reaction proceeded via an enantio-determining dynamic kinetic atroposelective transmetalation step.

Effective N‐Heterocyclic Carbenes with Indole Moiety Applied in the Pd‐Catalyzed Synthesis of Sterically Hindered Biaryls

AbstractIndolyl‐based benzimidazolium salts have been designed and prepared using three easy steps, namely indole alkylation, iodine‐catalyzed C−N bond coupling, and substitution. These salts have high catalytic performance in Pd‐catalyzed sterically hindered biaryl synthesis. The variability of the salt scaffold can be modified by the substitution of indole and alkyl halides. The Suzuki‐Miyaura cross‐coupling (SMC) of aryl chlorides was performed with satisfactory functional group tolerance and biaryls were obtained in 42–87% yield at 90 °C by using 0.5 mol% of Pd(OAc)2/1 i as the catalyst. Our results highlight the importance of maintaining a balance between the length of the carbon chain of substituents on the indole moiety and the steric congestion of substituents on the indole moiety for catalytic activity; this can be beneficial in difficult coupling processes. In addition, an asymmetric SMC reaction of aryl chloride under optimal reaction conditions was achieved with an 8% ee preliminarily.

Enantioselective construction of ortho-sulfur- or nitrogen-substituted axially chiral biaryls and asymmetric synthesis of isoplagiochin D

Axially chiral biaryl motifs possessing ortho-heteroatom-substituted functionalities exist widely in the structures of natural products and have served as foundation for constructing prominent chiral organocatalysts, ligands, functional materials, and even bioactive molecules. However, a general and enantioselective synthesis of such chiral structures with high synthetic value is rare. Taking advantage of the BaryPhos-facilitated asymmetric Suzuki-Miyaura cross-coupling, we have established a general, efficient and enantioselective construction of the ortho sulfur- or nitrogen-substituted axially chiral biaryls. The protocol shows excellent compatibility to various functional groups and structural features, delivering chiral biaryl structures with ortho-sulfonyl groups or with ortho-nitro groups at a broad range of molecular diversity and complexity. The immobilization of BaryPhos on polyethylene glycol (PEG) support has enabled homogeneous enantioselective cross-coupling in aqueous media and the palladium catalyst recycling for multiple times. The method has enabled a concise 10-step asymmetric synthesis of isoplagiochin D as well as the construction of chiroptical molecules with circularly polarized luminescence (CPL) properties.

Competent synthesis of biaryl analogs via asymmetric Suzuki–Miyaura cross-coupling for the development of anti-inflammatory and analgesic agents

Based on the core structure of diflunisal drug, herein, we report a resembling series of biaryl analogs (3a–j) containing halogens, nitro, and methoxy substituents. They were designed and synthesized via a Suzuki–Miyaura cross-coupling reaction using Pd (OH)2 as a catalyst at a temperature of 65 °C with an intent to obtain improved and safer anti-inflammatory and analgesic agents. Suzuki–Miyaura transformation is the most significant among the cross-coupling reactions since its practical advantages include the commercially available low toxic reagents, mild reaction conditions, and functional group compatibility. On the other hand, a few conditions can be used to cross-couple aryl boronic acids or esters with aryl halides, especially 2-benzyl halides. Because of this, a novel Suzuki–Miyaura protocol is investigated that facilitates the selective conversion of halo aromatics, with an emphasis on the reaction to convert substituted bromobenzene to conjugated biphenyls. Finally, the obtained biaryl analogs (3a–j) were tested for in vitro and in vivo anti-inflammatory and analgesic applications. The results showed that compound 3b performed better than the standard drug with IC50 values comparable to that of the standard drug for COX-1 and COX-2 inhibition. Finally, molecular docking tests for the effective compound were carried out.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13738-021-02460-0.

Rh-catalyzed asymmetric Suzuki-Miyaura cross-coupling

Pd-catalyzed dynamic kinetic asymmetric transformations with racemic allylic electrophiles and stabilized nucleophiles have been widely developed. Our group previously reported a Cu-catalyzed addition of alkyl nucleophiles to racemic allyl halides. Due to the importance of the Suzuki-Miyaura cross-coupling, we became interested in developing analogous reactions using sp2-hybridized boronic acid nucleophiles. We developed a Rh-catalyzed asymmetric Csp2-Csp3 cross-coupling of arylboronic acids and racemic allyl halides.

Fine Tuning of Chiral Bis(N-heterocyclic carbene) Palladium Catalysts for Asymmetric Suzuki–Miyaura Cross-Coupling Reactions: Exploring the Ligand Modification

Novel chiral N,N′-bisaryl bis(NHC) ligand precursors H2[(S)-2]Cl2 on a spiro scaffold and H2[(S)-3b–g]Cl2 with a binaphthyl linkage were rationally designed and their cyclometalated cis-chelated NH...

Axially Chiral Biaryl Monophosphine Oxides Enabled by Palladium/WJ-Phos-Catalyzed Asymmetric Suzuki–Miyaura Cross-coupling

A highly enantioselective palladium/WJ-Phos-catalyzed Suzuki–Miyaura coupling reaction for efficient construction of axially chiral biaryl monophosphine oxides was developed. A series of axially ch...

Consecutive Intermolecular Reductive Amination/Asymmetric Hydrogenation: Facile Access to Sterically Tunable Chiral Vicinal Diamines and N-Heterocyclic Carbenes.

A highly enantioselective iridium- or ruthenium-catalyzed intermolecular reductive amination/asymmetric hydrogenation relay with 2-quinoline aldehydes and aromatic amines has been developed. A broad range of sterically tunable chiral N,N'-diaryl vicinal diamines were obtained in high yields (up to 95 %) with excellent enantioselectivity (up to >99 % ee). The resulting chiral diamines could be readily transformed into sterically hindered chiral N-heterocyclic carbene (NHC) precursors, which are otherwise difficult to access. The usefulness of this synthetic approach was further demonstrated by the successful application of one of the chiral vicinal diamines and chiral NHC ligands in a transition-metal-catalyzed asymmetric Suzuki-Miyaura cross-coupling reaction and asymmetric ring-opening cross-metathesis, respectively.

Enantioselective synthesis of chiral heterocyclic biaryls via asymmetric Suzuki-Miyaura cross-coupling of 3-bromopyridine derivatives.

A series of chiral heterocyclic biaryls with a pyridyl moiety were prepared in moderate to good yields with up to 92% ee via asymmetric Suzuki-Miyaura coupling. The chiral-bridged biphenyl monophosphine ligand L1 was found to be much more effective in the reaction enantioselection than its counterpart binaphthyl monophosphine ligands.

1 H-1,2,3-Triazol-5-ylidenes: Readily Available Mesoionic Carbenes.

Classical carbenes are usually described as neutral compounds featuring a divalent carbon with only six electrons in their valence shell. It was only in 1988 that our group prepared the first isolable example, in which the carbene center was stabilized by a push-pull effect, using a phosphino and a silyl substituent. In the last 30 years, a myriad of acyclic and cyclic push-pull and push-push carbenes, bearing different heteroatom substituents, have been isolated. Among them, the so-called N-heterocyclic carbenes (NHCs), which include cyclic (alkyl)(amino)carbenes (CAACs), are arguably the most popular. They have found a vast number of applications ranging from catalysis to material science, and even in medicine. In this Account, we focus on the synthesis, structure, electronic properties, coordination, and applications of a different class of stable cyclic carbenes, namely, 1 H-1,2,3-triazol-5-ylidenes. In contrast with NHCs and CAACs, these compounds have no reasonable canonical resonance forms that can be drawn showing a carbene without additional charges. According to the IUPAC, they belong to the family of mesoionic compounds and thus they are named mesoionic carbenes (MICs). In 2010, we prepared the first stable 1,2,3-triazol-5-ylidene, via a CuAAC reaction, followed by alkylation of the resulting 1,2,3-triazole, and deprotonation. Later, we synthesized more robust N3-arylated counterparts from 1,3-diarylated-1 H-1,2,3-triazolium salts. Both synthetic routes can be carried out in multigram scales, making these MICS readily available. Importantly, MICs do not dimerize which contrasts with NHCs that can give the corresponding Wanzlick-type olefin. This property leads to relaxed steric requirements for their isolation; even C-unsubstituted MICs can be stored for months in the solid state at room temperature. The practicality and easily scalable syntheses of MICs allow for the preparation of polycarbenes, such as bis(1,2,3-triazol-5-ylidenes) (i-bitz), the analogues of the well-known 2,2'-bipyridines (bpy). MIC-transition metal complexes are excellent precatalysts for variety of chemical transformations, which include hydrohydrazination of alkynes, olefin metathesis, reductive formylation of amines with carbon dioxide and diphenylsilane, hydrogenation and dehydrogenation of N-heteroarenes in water, cycloisomerization of enynes, asymmetric Suzuki-Miyaura cross-coupling, and water oxidation (WO) reactions. Besides their catalytic applications, MIC-transition metal complexes have found applications in material sciences as exemplified by the preparation of the first iron(III) complex that is luminescent at room temperature. The peculiar properties of mesoionic triazolylidenes, combined with their enhanced stability, position them as excellent candidates to address some current challenges such as access to high-oxidation-state 3d metal complexes, the stabilization of highly reactive main group elements, the stabilization of nanoparticles, the preparation of efficient catalysts and photosensitizers based on earth-abundant transition metals, and the functionalization of self-assembled monolayers (SAMs) on gold.

Chiral triazolylidene-Pd-PEPPSI: synthesis, characterization, and application in asymmetric Suzuki-Miyaura cross-coupling.

A chiral triazolylidene-Pd-PEPPSI (PEPPSI = pyridine, enhanced, precatalyst, preparation, stabilization, initiation) complex with ferrocene-based planar chirality has been synthesized and characterized. Investigation of the electronic and steric nature of this complex revealed its powerful electron-donating ability (TEP 2044 cm-1) and high steric bulk (%Vbur = 42.2). These unique properties allow the complex to exhibit very high catalytic activity (TON = 420) for asymmetric Suzuki-Miyaura cross-coupling, providing the coupling product with good enantioselectivity (75% ee).

Pd(II) complexes of monodentate deoxycholic acid derived binaphthyl diamido phosphites as chiral catalysts in the asymmetric Suzuki-Miyaura cross-coupling

Chiral binaphthyl diamidophosphites derived from deoxycholic acid were synthesized and used as ligands for the preparation of mononuclear Pd(II) complexes, which were employed as catalysts in the asymmetric Suzuki-Miyaura cross-coupling of arylboronic acids with aryl bromides. Among the different reaction parameters, the substrate concentration emerged as being crucial for the outcome of the reaction: the reaction was faster in a concentrated reaction mixture, and could be performed at 0°C, where the reaction promoted by the Pd-complexes was more enantioselective affording cross-coupling products with ee up to 70%.

Palladium-Catalyzed Asymmetric Suzuki–Miyaura Cross Coupling with Homochiral Phosphine Ligands Having Tetrahydro-1H-imidazo[1,5-a]indole Backbone

Amphiphilic polystyrene-poly(ethylene glycol) resin-supported chiral imidazoindole phosphines (PS-PEG-L*), (3<i>R</i>,9a<i>S</i>)-2-aryl-3-(2-dialkylphosphino)phenyltetrahydro-1<i>H</i>-imidazo[1,5-<i>a</i>]indol-1-one, bearing PPh₂, P(<i>t</i>-Bu)₂, and P(<i>c</i>-Hex)₂ groups were designed and prepared with a view toward using them in aqueous heterogeneous asymmetric Suzuki–Miyaura biaryl coupling. The asymmetric coupling of 2-substituted 1-iodonaphthalenes and 2-substituted naphthalen-1-ylboronic acid took place in water under heterogeneous conditions in the presence of 10 mol% palladium of PS-PEG-L*-Pd complexes to give up to 94% ee of (<i>S</i>)-2,2′-disubstituted 1,1′-binaphthyls.

Enantioselective synthesis of axially chiral 3-bromo-4-alkoxy-2,6-dimethyl-5-(naphthalen-1-yl)pyridines via an asymmetric Suzuki–Miyaura cross-coupling reaction

A simple method is reported for the synthesis of chiral mono-naphthyl substituted pyridine derivatives in good yield and with good enantiomeric excess via the asymmetric Suzuki–Miyaura cross-coupling reaction of 3,5-dibromo-4-alkoxy-2,6-dimethylpyridine and naphthalen-1-ylboronic acid. The structure and absolute stereochemistry of 3-bromo-4-methoxy-2,6-dimethyl-5-(naphthalen-1-yl)pyridine were established by single-crystal X-ray analysis.

Efficient synthesis of chiral biaryls via asymmetric Suzuki-Miyaura cross-coupling of ortho-bromo aryl triflates

Efficient asymmetric Suzuki-Miyaura coupling of ortho-bromo aryl triflates with various arylboronic acids were described, providing a series of chiral biaryl triflates in high yields and up to 91% ee under mild conditions. The aryl triflates could be easily transformed to various chiral biaryl products by further derivatization. A one-pot tandem asymmetric cross-coupling/cross-coupling sequence was also achieved by using a single palladium catalyst, demonstrating the versatility of this method for preparation of chiral biaryl products.

Back Cover: Asymmetric Suzuki-Miyaura Cross-Coupling for the Synthesis of Chiral Biaryl Compounds as Potential Monophosphine Ligands (Chem. Eur. J. 18/2015)

Back Cover: Asymmetric Suzuki-Miyaura Cross-Coupling for the Synthesis of Chiral Biaryl Compounds as Potential Monophosphine Ligands (Chem. Eur. J. 18/2015)

ChemInform Abstract: Total Synthesis of the Antitumor Antibiotic (.+‐.)‐Streptonigrin: First‐ and Second‐Generation Routes for de Novo Pyridine Formation Using Ring‐Closing Metathesis.

The total synthesis of (±)-streptonigrin, a potent tetracyclic aminoquinoline-5,8-dione antitumor antibiotic that reached phase II clinical trials in the 1970s, is described. Two routes to construct a key pentasubstituted pyridine fragment are depicted, both relying on ring-closing metathesis but differing in the substitution and complexity of the precursor to cyclization. Both routes are short and high yielding, with the second-generation approach ultimately furnishing (±)-streptonigrin in 14 linear steps and 11% overall yield from inexpensive ethyl glyoxalate. This synthesis will allow for the design and creation of druglike late-stage natural product analogues to address pharmacological limitations. Furthermore, assessment of a number of chiral ligands in a challenging asymmetric Suzuki–Miyaura cross-coupling reaction has enabled enantioenriched (up to 42% ee) synthetic streptonigrin intermediates to be prepared for the first time.

Development of Efficient Asymmetric Suzuki-Miyaura Cross-Coupling and Applications in Synthesis

A series of structurally rigid, sterically bulky biaryl monophosphorus ligands were designed and synthesized to investigate the reactivity and stereoselectivity of asymmetric Suzuki-Miyaura cross-coupling reaction. High efficiencies were achieved in sterically demanding cross-couplings for the synthesis of tetra-ortho-substituted biaryls with various functional- ities. Sterically demanding aryl-alkyl Suzuki-Miyaura couplings between di-ortho-substituted aryl halides and secondary al- kylboronic acids were also successful. In achieving efficient asymmetric Suzuki-Miyaura coupling, we implemented a new concept by employment of a chiral biaryl monophosphorus ligand developed in the group as well as utilization of a secondary interaction between two coupling partner. Using a π-π interaction of a benzooxazolidinone substituent with one aryl partner, we developed enantioselective biaryl couplings containing ortho-carbonyl substituents. High enantioselectivities were also achieved in biaryl coupling containing ortho-oxy substituents by utilizing a polar-π interaction between a polar bis(2- oxo-3-oxazolidinyl)phosphonic (BOP) substituent and one aryl partner. The methodology enabled us for the first time to im- plement efficient asymmetric Suzuki-Miyaura coupling in total synthesis and accomplish the syntheses of chiral biaryl natural products korupensamines A and B, ultimately a concise and stereoselective synthesis of michellamine B. Keywords monophosphorus ligand; sterically demanding; Suzuki-Miyaura coupling; secondary interaction; total synthesis