Catalyzed Cross-coupling Reaction Research Articles

Induction heating enables efficient heterogeneous catalytic reactions over superparamagnetic nanocatalysts

Most catalytic processes are achieved by heating the whole reaction systems including the entire reactor, substrate and solvent, which leads to energy loss and obvious heat transfer limits. In this study, induction heating was employed to boost the catalytic Suzuki-Miyaura cross-coupling reactions by using conductive superparamagnetic microspheres with loaded Pd nanoparticles as heterogeneous catalysts. It was found that, at the same apparent reaction temperatures, the reactions by adopting the induction heating all exhibit better catalytic performance with higher conversion and yield, as compared to the reactions using conventional joule heating. The improvement is mainly attributed to the localized heating effect endowed by high efficiency of the heat transfer from the heat source to catalytic sites, which dissipates the electromagnetic energy through Néel relaxation mechanism. Moreover, it has be found that the reactions have been largely accelerated, resulting in much shorter reaction time required to approach a given value of reactant conversion. These results indicate that the unique heating method based on the superparamagnetic nanomaterials as both the inductive component and catalyst support holds a promising application for fast and efficient heterogeneous catalytic process, and exhibits potential for improving energy transfer efficiency and reducing the side reactions attributed to the uneven temperature profile.

Photocatalyst-engineering-promoted sulfonamidation of aryl halides via metallaphotoredox

In this issue of Chem Catalysis, Hou and co-workers demonstrate the integrated Ni/nitrogen-vacancy engineered carbon nitride for the synthesis of valuable aryl sulfonamide building blocks driven by visible light. Mechanistic investigation and the unprecedented substrate scope highlight the potential of photocatalyst modulation in achieving challenging metallaphotoredox catalytic cross-coupling reactions.

Transition-Metal-Catalyzed C-S, C-Se, and C-Te Bond Formations via Cross-Coupling and Atom-Economic Addition Reactions. Achievements and Challenges.

In the present review, we discuss recent progress in the field of C-Z bond formation reactions (Z = S, Se, Te) catalyzed by transition metals. Two complementary methodologies are considered─catalytic cross-coupling reactions and catalytic addition reactions. The development of advanced catalytic systems is aimed at improved catalyst efficiency, reduced catalyst loading, better cost efficiency, environmental concerns, and higher selectivity and yields. The important rise of research efforts in sustainability and green chemistry areas is critically assessed. The paramount role of mechanistic studies in the development of a new generation of catalytic systems is addressed, and the key achievements, problems, and challenges are summarized for this field.

Palladium catalyzed radical relay for the oxidative cross-coupling of quinolines

Traditional approaches for transition-metal catalyzed oxidative cross-coupling reactions rely on sp2-hybridized starting materials, such as aryl halides, and more specifically, homogeneous catalysts. We report a heterogeneous Pd-catalyzed radical relay method for the conversion of a heteroarene C(sp3)–H bond into ethers. Pd nanoparticles are supported on an ordered mesoporous composite which, when compared with microporous activated carbons, greatly increases the Pd d charge because of their strong interaction with N-doped anatase nanocrystals. Mechanistic studies provide evidence that electron-deficient Pd with Pd–O/N coordinations efficiently catalyzes the radical relay reaction to release diffusible methoxyl radicals, and highlight the difference between this surface reaction and C–H oxidation mediated by homogeneous catalysts that operate with cyclopalladated intermediates. The reactions proceed efficiently with a turn-over frequency of 84 h−1 and high selectivity toward ethers of >99%. Negligible Pd leaching and activity loss are observed after 7 catalytic runs.

Pd-Catalyzed Cross-Couplings: On the Importance of the Catalyst Quantity Descriptors, mol % and ppm.

This Review examines parts per million (ppm) palladium concentrations in catalytic cross-coupling reactions and their relationship with mole percentage (mol %). Most studies in catalytic cross-coupling chemistry have historically focused on the concentration ratio between (pre)catalyst and the limiting reagent (substrate), expressed as mol %. Several recent papers have outlined the use of “ppm level” palladium as an alternative means of describing catalytic cross-coupling reaction systems. This led us to delve deeper into the literature to assess whether “ppm level” palladium is a practically useful descriptor of catalyst quantities in palladium-catalyzed cross-coupling reactions. Indeed, we conjectured that many reactions could, unknowingly, have employed low “ppm levels” of palladium (pre)catalyst, and generally, what would the spread of ppm palladium look like across a selection of studies reported across the vast array of the cross-coupling chemistry literature. In a few selected examples, we have examined other metal catalyst systems for comparison with palladium.

Palladium catalyzed cross-coupling of 3-methylthiophene-2-carbonyl chloride with aryl/het-aryl boronic acids: a convenient method for synthesis of thienyl ketones

Bi-aryl ketones are important motifs in large number of pharmaceutical compounds and natural products. A protocol for the synthesis of thienyl ketones has been developed via Pd (0) catalyzed cross-coupling reaction. The desired thienyl ketones (3a-x) were synthesized by cross coupling of 3-methylthiophene-2-carbonyl chloride with variety of aryl/heteroaryl-boronic acids in good to excellent yields (46–91%) under mild conditions (1.5 eq Cs2CO3 at 50 °C). Different functional groups were well tolerated under the developed reaction conditions.

Development of Catalytic Cross-Coupling Reactions Based on Transition Metal→Z-type Ligand Interactions

Development of Catalytic Cross-Coupling Reactions Based on Transition Metal→Z-type Ligand Interactions

Regioselective Synthesis of Naphthothiophenes by Pd Catalyzed Cross-Coupling Reactions and Alkyne-Carbonyl Metathesis.

Naphthothiophenes were prepared from commercially available 2,3-dibromothiophenes in two steps by one-pot Suzuki/Sonogashira or Sonogashira/Suzuki coupling reactions, followed by intramolecular alkyne-carbonyl-metathesis reactions. The final cyclization reaction proceeds in the presence of p-toluenesulfonic acid and provides a rapid access to two series of isomeric naphthothiophenes.

Sulfonated poly(phenylene-co-arylene ether sulfone) multiblock membranes for application in high-performance fuel cells

Sulfonated multiblock poly(phenylene- co -arylene ether sulfone) (SmPPES) membranes for application in polymer electrolyte membrane fuel cells are prepared via Colon's Nickel catalyzed cross-coupling reaction. Their chemical stabilities and proton transport abilities are examined as functions of ion-exchange capacity (IEC) and hydrophilic (sulfonated phenylene) and hydrophobic (arylene ether sulfone) block lengths. The membranes show well-defined phase separation and proton conductivities comparable to or exceeding that of a reference Nafion membrane. Block length is positively correlated with conductivity and oxidative stability; SmPPES10–2.0 showed conductivities of 0.11 and 0.13 S/cm in water at 25 °C and 80 °C (90% relative humidity), respectively, and those of SmPPES5-2.0 were 0.10 and 0.11 S/cm, respectively. The SmPPES membrane oxidative stabilities (determined by Fenton's oxidative tests and peroxide exposure tests) are superior to those of conventional poly(arylene ether) membranes because of their sulfonated phenylene blocks. At 80 °C and 100% relative humidity, the optimal SmPPES membrane (IEC = 2.5 meq/g) delivers a current density of 1.5 A/cm 2 at 0.6 V (hydrogen/air) and a high-frequency resistance of 38 mΩ cm 2 , outperforming the reference Nafion NR211 membrane. This control over sulfonated phenylene and ether sulfone hydrophobic blocks provides new insight into designing high-performance polymer electrolyte membranes. • Sulfonated multiblock poly(phenylene- co -arylene ether sulfone) (SmPPES) membranes. • SmPPES membranes prepared using a combination of meta - and para -phenylene. • SmPPES membranes outperformed sulfonated poly(arylene ether sulfone) copolymers. • Fuel cell performance of optimal SmPPES membrane exceeded that of a Nafion membrane. • Flexible phenylene block copolymers comparable to perfluorosulfonic acid membranes.

Synthesis of imidazo[1,2-a]benzoazepines by alkyne-carbonyl-metathesis

Imidazo[1,2-a]benzoazepines were prepared by Brønsted acid-mediated intramolecular alkyne-carbonyl metathesis (ACM). The starting materials, imidazole and benzimidazole derivatives, were prepared by N-alkylation, formylation and Sonogashira cross-coupling reaction. The final intramolecular ACM delivered the final products in good to excellent yields and with a wide tolerance towards functional groups.

Competitive gold/nickel transmetalation.

Transmetalation is a key method for the construction of element-element bonds. Here, we disclose the reactivity of [NiII(Ar)(I)(diphosphine)] compounds with arylgold(I) transmetalating agents, which is directly relevant to cross-coupling catalysis. Both aryl-for-iodide and unexpected aryl-for-aryl transmetalation are witnessed. Despite the strong driving force expected for Au-I bond formation, aryl scrambling can occur during transmetalation and may complicate the outcomes of attempted catalytic cross-coupling reactions.

A reactivity model for oxidative addition to palladium enables quantitative predictions for catalytic cross-coupling reactions.

Making accurate, quantitative predictions of chemical reactivity based on molecular structure is an unsolved problem in chemical synthesis, particularly for complex molecules. We report an approach to reactivity prediction for catalytic reactions based on quantitative structure-reactivity models for a key step common to many catalytic mechanisms. We demonstrate this approach with a mechanistically based model for the oxidative addition of (hetero)aryl electrophiles to palladium(0), which is a key step in myriad catalytic processes. This model links simple molecular descriptors to relative rates of oxidative addition for 79 substrates, including chloride, bromide and triflate leaving groups. Because oxidative addition often controls the rate and/or selectivity of palladium-catalyzed reactions, this model can be used to make quantitative predictions about catalytic reaction outcomes. Demonstrated applications include a multivariate linear model for the initial rate of Sonogashira coupling reactions, and successful site-selectivity predictions for Suzuki, Buchwald-Hartwig, and Stille reactions of multihalogenated substrates relevant to the synthesis of pharmaceuticals and natural products.

A water soluble Ni-Schiff base complex for homogeneous green catalytic C[sbnd]S cross-coupling reactions

Since the embarkation of CS cross-coupling from aryl halides with thiols a handful of works have been contemplated in aqueous medium. Herein, we report an example of a water soluble Ni-Schiff base complex as the green catalyst for the synthesis of thioethers. We have synthesized a Ni-Schiff base complex [NiL(H2O)2](ClO4)2 using N4-donor Schiff base ligand (1,3-bis(((E)-pyridin-2-ylmethylene)amino)propan-2-ol) and characterized by single crystal X-ray diffraction (SC-XRD) study along with different spectral analyses. The complex is mononuclear and cationic in nature having two perchlorate anions. Two water molecules remain coordinated with the Ni(II)-centre. The hydrogen bonding interaction through coordinated water and perchlorate anions connect the monomeric units to form 2D supramolecular structure. Based on its aqueous solubility, the complex has been used for the catalytic CS cross-coupling reaction between aryl iodide and aryl or alkyl thiols using TBAB at 60 °C in aqueous media (yield 92%). At room temperature, an isolated yield of 57% can be achieved. This environmentally benign protocol is paramount in view of the environmental sustainability.

Narrowly-Distributed Conjugated Polymers Synthesized through Suzuki Polymerization with Palladium(II) N-Heterocyclic Carbene Complex Confined in Dendritic Mesoporous Silica Nanoparticles.

A catalytic heterogenous Suzuki polymerization method was developed by confining the Pd(II)-catalyzed cross coupling reactions to take place exclusively in the nanochannels of dendritic mesoporous silica nanoparticles. Conjugated polymers with various monomer combinations, including donor-acceptor structures, were obtained in high yields. The molecular weights of the obtained polymers were well controlled with narrow molecular weight distributions (PDI value down to 1.13). All the polymeric products were highly soluble in common organic solvents, granting them with high processability. All the features of this confined Suzuki polymerization method endow the conjugated polymers great potential in optoelectronic applications.

Experimental and theoretical investigation of synthesized pregnenolone derivatives via palladium catalyzed cross coupling reactions, their anticancer activity against lung cancer cells

In the current research work synthesis of novel steroids, PGLCROBB, PGLCROMBT, and PGLCROB are being reported employing palladium catalyzed Mizoroki-Heck reaction. Structure elucidation of all the synthesized compounds was done by 1H NMR, 13C NMR, IR, and mass spectrometry. These prodrugs PGL, PGLCRO, PGLCROBB, PGLCROMBT, and PGLCROB were tested on human lung cancer cell line (A549). The results were very promising as PGLCROB has shown significant anticancer activity against lung cancer cells. In order to look into the structural stability and electronic feature analyses, quantum chemical calculations have been performed using the DFT approach. To spot, describe, and estimate competently the weak C-H⋯O H-bonding and H⋯H (conventional) as well as C⋯H (unconventional) non-covalent interactions (NCIs) involved therein, the Bader's QTAIM and NCI-plot have also been executed. The H⋯H bond paths range from 2.021 Å to 2.039 Å however the C⋯H bond paths fall between 2.806 Å and 2.871 Å and such type of interactions demonstrate all the characteristics of a closed-shell interaction. The analyzed chemical reactivity mainly emphasized for PGLCRO, PGLCROB, PGLCROBB and PGLCROMBT systems shows that the PGLCROB (with a very marginal difference with the PGLCROBB) is chemically more reactive (highly sensitive) species among all steroids. This work represents another instance of the utilization and successful application of the concept of bond path and the QTAIM.

Photoredox-Mediated Asymmetric Cross-Dehydrogenative Coupling of Enones and Tertiary Amines by Chiral Primary Amine Catalysis

AbstractA catalytic asymmetric dehydrogenative cross-coupling reaction between enones and tertiary amines enabled by synergistic photoredox and chiral primary amine catalysis is reported. The reaction was proposed to proceed via the interception of iminium ion intermediate, in situ generated from photoredox oxidation, by dienamine at α-position, followed by isomerization, leading to aza-Morita–Baylis–Hillman-type products with good diastereo- and enantioselectivity.

Existence of a Heterogeneous Pathway in Palladium-Catalyzed Carbon–Carbon Coupling Reaction: Evidence from Ag@Pd 3 Cu Intermetallic Nanoplates

Palladium (Pd)-catalyzed cross-coupling reaction is a widely studied process with significant economic interest and represents one of the most successful nanocatalytic examples. Owing to the observ...

Editorial Catalysts: Special Issue on Transition Metal Catalyzed Cross-Coupling Reactions

Transition metal catalyzed cross-coupling reactions have proved to be powerful tools for carbon–carbon as well as carbon–heteroatom bond formation in the development of synthetic methodologies for applications ranging from pharmaceuticals to materials [...]

A Visible-Light-Harvesting Covalent Organic Framework Bearing Single Nickel Sites as a Highly Efficient Sulfur-Carbon Cross-Coupling Dual Catalyst.

Covalent Organic Frameworks (COFs) have recently emerged as light-harvesting devices, as well as elegant heterogeneous catalysts. The combination of these two properties into a dual catalyst has not yet been explored. We report a new photosensitive triazine-based COF, decorated with single Ni sites to form a dual catalyst. This crystalline and highly porous catalyst shows excellent catalytic performance in the visible-light-driven catalytic sulfur-carbon cross-coupling reaction. Incorporation of single transition metal sites in a photosensitive COF scaffold with two-component synergistic catalyst in organic transformation is demonstrated for the first time.

Phosphine–Borane Ligands Induce Chemoselective Activation and Catalytic Coupling of Acyl Chlorides at Palladium

Acyl chlorides are highly reactive and widely used substrates in catalytic cross-coupling reactions, but so far, site selectivity over other functional groups has remained an issue. In this work, Pd complexes deriving from the phosphine-boranes [i-Pr2P(o-C6H4)](2)BFXyl and i-Pr2P(o-C6H4)-BFXyl(2) (Fxyl = 3,5-(F3C)(2)C6H3) were found to preferentially activate acyl chlorides over C-I, C-Br, C-Cl, C-OTf, and C-OTs bonds. The system is amenable to catalysis (Stille and Negishi couplings), providing a simple and efficient means to forge C(=O)-C bonds in a site-selective manner and to readily access functionalized ketones. To gain insight into the role and influence of the ambiphilic ligands, key Pd complexes have been authenticated and the reaction profiles have been analyzed by density functional theory (DFT) calculations.