Efficient Suzuki Cross-coupling Research Articles

Developing Efficient Suzuki Cross-Coupling Catalysts by Doping Palladium Clusters with Silver

It is shown that doping of a Pd cluster by Ag atoms can provide an efficient catalyst for the Suzuki–Miyaura cross-coupling reactions. We demonstrate this intriguing possibility by considering a model reaction involving bromobenzene and phenylboronic acid as reagents where the reaction involves oxidation, transmetallation, and reduction steps. We have examined the reaction barriers of all three steps for a conventional ligated Pd catalyst, a nearly icosahedral Pd13 cluster, and a monosilver-doped Pd12Ag cluster using gradient-corrected density functional theory. It is observed that the reaction carried out on the Pd sites adjacent to an Ag atom in a Pd12Ag cluster shows substantially lower barriers for the oxidation and reduction steps compared to the conventional ligated Pd catalyst and the pure Pd13 cluster. A detailed analysis indicates that the Ag site donates charge to the neighboring Pd site. While such a donation may have been expected to reduce the barrier for the oxidative step, the lowering of the barrier for the reduction step indicates that the respective sites not only act as a donor but can also serve as an acceptor for the reduction step. Furthermore, because of the differential donor–acceptor characteristic of the Ag and Pd atoms, it is observed that the barrier heights of the redox steps are primarily dependent on the chosen active site. The calculated results show that by altering the atom (Ag or Pd) at the active site of the reaction, the activation energies of the redox steps can either be reduced or increased. This shows that the active sites of a bimetallic cluster-like Pd12Ag can be utilized to control the barrier heights of suitable chemical reactions. The relative trend of the barrier heights for both clusters is also observed to be predictable by the conceptual density functional theory. Previous studies in our group have indicated that the reaction barriers for Pdn clusters can be lowered by supporting them on reduced graphene. We, therefore, propose that silver-doped Pdn clusters may provide an even better catalyst.

Molecular engineered palladium single atom catalysts with an M-C1N3 subunit for Suzuki coupling

Efficient Suzuki cross-coupling is promoted by ultrathin palladium single atom catalyst with molecularly precise Pd-N3C1 subunit, which is attributed to a facilitated oxidative addition on electron-rich Pd centers than conventional Pd-N4 coordination.

Highly efficient Suzuki cross-coupling reaction of biomaterial supported catalyst derived from glyoxal and chitosan

In this study a new chitosan based water soluble Schiff base was produced through carboxymethylation of chitosan and its Pd(II) complex were synthesized and characterized by FTIR, 1H NMR, 13C CP-MAS NMR, TG/DTG, SEM/EDAX, XRD, ICP-OES, UV–Vis, magnetic moment measurements, molar conductivity measurements. The catalytic activity of the complex was tested in Suzuki coupling reactions for synthesis of biaryls containing various substrates. The identifications of the biarlys were performed by 1H NMR and GC–MS. The catalytic activity tests revealed that high selectivity was achieved with a small addition of the catalyst. Moreover by-product formation was not observed in the spectra of 1H NMR and GC–MS. Mercury poisoning and leaching test confirmed that the catalyst has heterogeneous character. The reusability tests showed that the catalyst did not lose its activity after six runs.

New dimeric phosphine ylide copper (I) complexes: Synthesis, coordination behavior, and application in Suzuki cross-coupling reactions

The reaction of the non-symmetric phosphorus ylides, Ph 2 P(CH 2 ) n PPh 2 C(H)C(O)PhR with CuCl in equimolar ratios using dry methanol as solvent give binuclear complexes of the type [Cu(μ-Cl){Ph 2 P(CH 2 ) n PPh 2 C(H)C(O)PhR}] 2 ( n = 1: R = Br ( 1 ), OCH 3 ( 2 ); n = 2: R = Br ( 3 ), OCH 3 ( 4 )). X-ray analyses of 1 demonstrate the Cl bridged dimeric structures with P,C-chelated ligands. Characterizations of these compounds were carried out by FT-IR and multinuclear NMR technique. Elemental analysis indicate a 1:1 stoichiometry between the ylides and the Cu(I) chloride in the four complexes. The precursor complexes 1 and 3 are found to exhibit high catalytic activity in the Cu-catalyzed Suzuki cross-coupling reactions in an air atmosphere at medium catalyst loading in DMF as a solvent. The use of 5 mol% catalyst in the presence of Cs 2 CO 3 allows the coupling reaction to proceed with moderate to excellent yields. The reactions of CuCl with bidentate α-keto stabilized phosphorus ylides give binuclear complexes of the type [Cu(μ-Cl){ Ph 2 P(CH 2 ) n PPh 2 C(H)C(O)PhR}] 2 ( n = 1: R = Br ( 1 ), OCH 3 ( 2 ), n = 2: R = Br ( 3 ), and OCH 3 ( 4 )). X-ray analysis of 1 demonstrates a Cl bridged dimeric structure with P,C-chelated ligands. Highly efficient Suzuki cross-coupling reaction between various aryl halides and phenylboronic acid using 1 and 3 as catalyst precursors under aerobic conditions has been developed. • Synthesis and characterization of Cu(I) phosphine-ylide complexes are presented. • X-ray analyses demonstrate the structures (L-Cu(μ-Cl )2 Cu-L) with P, C-chelated ligands. • Elemental analysis indicate a 1:1 stoichiometry between ylides and Cu(I). • These Cu(I) complexes were used for the first time in Suzuki cross-coupling reactions. • High yields were obtained in the reaction of phenylboranic acid with various aryl halides.

Highly efficient Suzuki cross-coupling reaction within an open channel plastic microreactor immobilized with palladium complexes

A practical open channel microfluidic reactor with immobilized palladium complex was built on a cyclic olefin copolymer (COC) chip that was fabricated with a very simple hot-embossing technique. Palladium complex was immobilized on a photochemically grafted layer of polymerized N-[3-(dimethylamino)propyl]methacrylamide. Surface modification and catalyst immobilization onto COC were systematically characterized with streaming potential, surface contact angle, attenuated total reflection Fourier transform infrared spectrometry, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The reactor was comprised of a single 15 cm long serpentine channel of 120 μm (i.d.) and exhibited high efficiency for the Suzuki cross-coupling reaction of aryl iodides and bromides with arylboronic acids, affording good to excellent yields of the corresponding products. The reactions could be carried out smoothly with reduced reaction time and lower reactant consumption in the microreactor thermostated at 50°C. The proposed system may have great potential for high-throughput screening of catalysts and reaction conditions.

Pd/P(t-Bu)(3)-Catalyzed Suzuki Cross-Couplings in the Presence of Water.

Pd(2)(dba)(3)/[HP(t-Bu)(3)]BF(4)/KF•2H(2)O serves as a mild, robust, and user-friendly method for the efficient Suzuki cross-coupling of a diverse array of aryl and heteroaryl halides with aryl- and heteroarylboronic acids.

ChemInform Abstract: Palladium-bisimidazol-2-ylidene Complexes as Catalysts for General and Efficient Suzuki Cross-Coupling Reactions of Aryl Chlorides with Arylboronic Acids.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Divergent Approach to the Synthesis of 3-Substituted-2-pyrazolines: Suzuki Cross-Coupling of 3-Sulfonyloxy-2-pyrazolines

The efficient Suzuki cross-coupling of pyrazoline nonaflates with organoboron reagents was achieved to afford diverse 3-substituted-2-pyrazolines in excellent yield. The nonaflates displayed improved reactivity over the corresponding triflates and smoothly coupled to a variety of aryl- and heteroarylboronic acids. This process and its broad scope constitute a rapid, divergent strategy for the synthesis of elaborated 2-pyrazolines that are not readily obtained via conventional methods.

Pd[tBuNH(S)NHP(O)(OiPr)2-S]2Cl2 Complex as Air- and Moisture-Stable Catalyst for Palladium Catalyzed Suzuki Cross-Coupling Reaction

A highly efficient Suzuki cross-coupling reaction between phenyl bromide and phenylboronic acid catalyzed by the palladium complex Pd[tBuNH(S)NHP(O)(OiPr)2-S]2Cl2 in acetonitrile, toluene, THF or DMF has been investigated. The bases we have employed for this reaction were Na2CO3, K2CO3 or Cs2CO3. It was established that using DMF and K2CO3 at 100 °C shows excellent yields of the product at the catalyst amount of 0.1 mmol. The cross-coupling reactions of iodo- and chloro-benzene with phenylboronic acid were also investigated. The influence of the halide nature was as expected.

A Simple, Modular Method for the Synthesis of 3,4,5-Trisubstituted Pyrazoles

A modular approach for the regiocontrolled preparation of pyrazoles bearing substituents on all three carbon atoms is described. Central to this method is the use of a switchable metal-directing group (MDG) to enable sequential direct lithiation of the 3- and 5-positions of the pyrazole ring. Pyrazole boronic esters obtained from these lithiated intermediates can undergo efficient Suzuki cross-coupling under the developed nonaqueous conditions, which minimize undesirable protolytic deboronation. Halogenation of the 4-position provides the means for substitution at the remaining carbon atom.

Total Synthesis and Structure Revision of the Marine Metabolite Palmerolide A.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Total Synthesis and Structure Revision of the Marine Metabolite Palmerolide A

We describe a highly convergent and flexible synthesis of the novel antarctic marine metabolite palmerolide Aan effort leading to a reformulation of palmerolide A as ent-24, the enantiomer of the C19,C20-bis-epimer of the original proposed structure 1. Our total synthesis features a highly stereoselective vinylogous Mukaiyama aldol reaction to introduce the C19,C20-stereodiad, an efficient Suzuki cross-coupling to install the endocyclic diene unit, and an intramolecular Horner−Wadsworth−Emmons olefination to close the macrocycle. Starting from fragments 2, 3 (ent-3), and 13 (prepared in five to eight steps each, 38−70% overall yield) the synthesis of the proposed structure 1 and the enantiomer of palmerolide A (24) was completed in an additional 14 steps (22 steps longest linear sequence).

Palladium‐Catalyzed Ligand‐Free Suzuki Cross‐Coupling Reactions of Benzylic Halides with Aryl Boronic Acids under Mild Conditions.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Palladium catalyzed ligand-free Suzuki cross-coupling reactions of benzylic halides with aryl boronic acids under mild conditions

A highly efficient Suzuki cross-coupling reaction between benzylic halides and aryl boronic acids using palladium chloride as catalyst in acetone:water (3:1) as the solvent system has been developed. High yields of products, mild reaction conditions and short reaction times in the absence of ligand are important features of this method.

Synthesis of 2,8-Disubstituted Analogues of Troeger’s Base

Starting from the 2,8-dibromo- and the 2,8-diiodo-substituted Troeger's base analogues 1 and 2, several new symmetrically disubstituted derivatives 4, 5, and 7-17 could be obtained by transition metal-catalyzed cross-coupling reactions or other functionalizations like borylation or protecting group operations. For the first time, conditions for a highly efficient Suzuki cross-coupling reaction involving the Troeger's base core were established.

Synthesis of Non‐Proteinogenic Phenylalanine Analogues by Suzuki Cross‐Coupling of a Serine‐Derived Alkyl Boronic Acid.

Protected serine-derived boronic acids have been prepared as β-anionic alanine equivalents, and undergo efficient Suzuki cross-coupling with a variety of aryl halides to give, after elaboration, non-proteinogenic phenylalanine analogues.

Synthesis of non-proteinogenic phenylalanine analogues by Suzuki cross-coupling of a serine-derived alkyl boronic acid

Protected serine-derived boronic acids have been prepared as β-anionic alanine equivalents, and undergo efficient Suzuki cross-coupling with a variety of aryl halides to give, after elaboration, non-proteinogenic phenylalanine analogues.

Palladium−Imidazol-2-ylidene Complexes as Catalysts for Facile and Efficient Suzuki Cross-Coupling Reactions of Aryl Chlorides with Arylboronic Acids

Palladium−Imidazol-2-ylidene Complexes as Catalysts for Facile and Efficient Suzuki Cross-Coupling Reactions of Aryl Chlorides with Arylboronic Acids