Presence Of Copper Catalyst Research Articles

TBHP/TEMPO‐Mediated Oxidative Synthesis of Imides from Amides

AbstractA new protocol for the synthesis of imides has been developed. In the presence of copper catalyst, N‐benzylamides were oxidized to the corresponding imides by TBHP/TEMPO system in moderate to good yields.

Controlled Synthesis of Nitrogen-Doped Graphene from a Heteroatom Polymer and Its Mechanism of Formation

Heteroatom polymeric precursor with an aromatic substituent (polyurethane acrylate) was designed and found to generate nitrogen-doped graphene at 1000 °C. Upon thermal degradation, a nitrogenous fragment was liberated in situ. As a consequence, nitrogen-doped graphene was formed in a single step. Further, this methodology was extended for studying the effect of annealing nonheteroatom polymer with an aromatic substituent (styrene butadiene random copolymer) under similar conditions. The isolated product demonstrated undoped graphene-like structure. The mechanism of nitrogen-doped graphitization was studied by annealing different heteroatom polymer units with an aliphatic and aromatic framework in a chemical vapor deposition reactor. The effect of precursor heteroatom polymer structure and annealing temperature in the presence of copper catalyst on the efficacy of formation of nitrogen-doped graphene was examined. The nitrogen-doped graphene exhibited semiconducting behavior over semimetallic behavior of the undoped graphene. Moreover, the nitrogen-doped graphene displayed better electrochemical properties compared to the undoped variety. These advances in the synthesis of graphitic structures can be readily extended for the fabrication of many advanced materials with controlled structure and properties.

Synthesis and Antibacterial Activity of 5-Phthalate and 5-Glutarate Derivatives of Milbemycins A3/A4*

Naturally occurring 16-membered macrolides milbemycins A3 and A4 were selectively esterified at their 5-OH group with phthalic and glutaric anhydrides. The obtained monoesters were further functionalized by amide formation. Propargylamide derivatives were demonstrated to undergo 1,2,3-triazole formation upon treatment with organic azides in the presence of copper catalyst. Some of the synthesized compounds exhibited useful levels of antibacterial properties against Staphylococcus aureus and Staphylococcus epidermidis.

Synthesis of heteroaryl containing sulfides via enaminone ligand assisted, copper-catalyzed C–S coupling reactions of heteroaryl thiols and aryl halides

The C–S cross coupling reactions between electron deficient heteroaryl thiols and aryl halides have been smoothly performed to provide various heteroaryl containing sulfides in the presence of copper catalyst and enaminone ligand.

ChemInform Abstract: New Methods of Heterogeneous Catalysis for Lignocellulosic Biomass Conversion to Chemicals

AbstractReview: 54 refs.

Site-specific bioconjugation of a murine dihydrofolate reductase enzyme by copper(I)-catalyzed azide-alkyne cycloaddition with retained activity.

Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is an efficient reaction linking an azido and an alkynyl group in the presence of copper catalyst. Incorporation of a non-natural amino acid (NAA) containing either an azido or an alkynyl group into a protein allows site-specific bioconjugation in mild conditions via CuAAC. Despite its great potential, bioconjugation of an enzyme has been hampered by several issues including low yield, poor solubility of a ligand, and protein structural/functional perturbation by CuAAC components. In the present study, we incorporated an alkyne-bearing NAA into an enzyme, murine dihydrofolate reductase (mDHFR), in high cell density cultivation of Escherichia coli, and performed CuAAC conjugation with fluorescent azide dyes to evaluate enzyme compatibility of various CuAAC conditions comprising combination of commercially available Cu(I)-chelating ligands and reductants. The condensed culture improves the protein yield 19-fold based on the same amount of non-natural amino acid, and the enzyme incubation under the optimized reaction condition did not lead to any activity loss but allowed a fast and high-yield bioconjugation. Using the established conditions, a biotin-azide spacer was efficiently conjugated to mDHFR with retained activity leading to the site-specific immobilization of the biotin-conjugated mDHFR on a streptavidin-coated plate. These results demonstrate that the combination of reactive non-natural amino acid incorporation and the optimized CuAAC can be used to bioconjugate enzymes with retained enzymatic activity.

ChemInform Abstract: Cu‐Catalyzed Couplings of Aryl Iodonium Salts with Sodium Trifluoromethanesulfinate.

A convenient method for the preparation of aryl trifluoromethylsulfones from the reactions of diaryliodonium salts with sodium trifluoromethanesulfinate in the presence of copper catalysts is described. Cuprous oxide in DMF was found to be the optimal catalyst for the reaction. The reaction conditions are tolerant of various functional groups as well as of various counteranions of the iodonium salt. The synthetic utility of the process is demonstrated by performing the reaction on a preparative scale (88 g).

Cu-Catalyzed Couplings of Aryl Iodonium Salts with Sodium Trifluoromethanesulfinate

A convenient method for the preparation of aryl trifluoromethylsulfones from the reactions of diaryliodonium salts with sodium trifluoromethanesulfinate in the presence of copper catalysts is described. Cuprous oxide in DMF was found to be the optimal catalyst for the reaction. The reaction conditions are tolerant of various functional groups as well as of various counteranions of the iodonium salt. The synthetic utility of the process is demonstrated by performing the reaction on a preparative scale (88 g).

New methods of heterogeneous catalysis for lignocellulosic biomass conversion to chemicals

This review deals with the use of solid catalysts for the enhancement of the efficiency and the development of a new generation of environmentally friendly, energy and resource efficient processes for the deep processing of lignocellulosic biomass to desired chemicals. The oxidative delignification of wood with hydrogen peroxide in the presence of the suspended TiO2 catalyst, the oxidation of wood with molecular oxygen in the presence of copper catalysts, the acidcatalyzed conversion of cellulose to glucose and levulinic acid, and the thermal conversion of lignin to fuel additives on solid acid catalysts are analyzed. New integrated processes based on the heterogeneous catalytic oxidation are suitable for the complex processing of lignocellulosic biomass to produce valuable chemicals and engine fuel components without the use of toxic and corrosion-active reagents.

Expedient synthesis of tetrafluorophenoxthiines and derivatives by copper(I)-catalyzed cross-coupling reaction

In this research, tetrafluorophenoxthiines were successfully synthesized from pentafluorobenzene and aryl thiols or diaryl disulfides in the presence of copper catalyst and ligand by using O2 as the oxidant, t-BuOLi as the base at 100°C. The ligand (E)-3-(dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-one (L) played an indispensable role in the reaction. This work contains a notable mode of CF bond activation, which is in the ortho position to the CH bond of pentafluorobenzene.

Synthesis of 2,5-Bis(hetero)aryl 4′-Substituted 4,5′-Bisoxazoles via Copper(I)-Catalyzed Domino Reactions of Activated Methylene Isocyanides with 2-Phenyl- and 2-(2-Thienyl)-4-[(aryl/heteroaryl)(methylthio)methylene]oxazol-5(4H)-ones

An efficient straightforward synthesis of 2,5,4'-trisubstituted 4,5'-bisoxazoles via copper(I)-catalyzed domino reactions of 2-phenyl- and 2-(2-thienyl)-4-[(aryl/heteroaryl)methylene]-5-oxazolones with activated methylene isocyanides has been reported. The overall domino process comprised of formation of one C-C and two C-O bonds involves initial nucleophilic ring opening of oxazolones by cupriomethylene isocyanides followed by sequential construction of two oxazole rings in the presence of copper catalyst. The broad substrate scope and excellent functional group compatibility of the reaction has been demonstrated by employing a variety of heteroaryl- and aryl-substituted oxazolones and activated methylene isocyanides, yielding bisoxazoles with three potential points of diversity. A probable mechanism for this novel copper-catalyzed domino process has been proposed.

Copper-catalyzed trifluoromethylation of aryl- and vinylboronic acids with generation of CF3-radicals

The selective trifluoromethylation of aryl- and vinylboronic acids proceeds smoothly with CF3SO2Na (Langlois reagent) in the presence of copper catalysts and t-BuOOH. Therefore, the method relies both on transition metal catalysis and selective radical reactions. Advantageously, the protocol can be performed at room temperature under an air atmosphere and avoids the issue of poor regioselectivity.

ChemInform Abstract: Copper‐Catalyzed Alkene Arylation with Diaryliodonium Salts.

AbstractA new approach to the arylation of simple alkenes is developed, involving their reaction with aryliodonium triflates (II) in the presence of copper catalysts.

Study on Metal-Induced Reactions of α-Diazocarbonyl Glucosides

Conversions of diazocarbonyl carbohydrate compounds catalyzed by a series of rhodium and copper catalysts in conventional heating or microwave conditions were investigated. C-H insertion product was obtained in the presence of Rh(2)(OAc)(4). Intermolecular reactions rather than intramolecular reactions occurred in the presence of copper catalysts.

Microwave-Assisted Click Chemistry Synthesis of 1,2,3-Triazoles from Aryldiazonium Silica Sulfates in Water

A microwave-assisted click chemistry synthesis of 1,4-disubstituted 1,2,3-triazoles is studied by in situ generation of aryl azides via the reaction of aryldiazonium silica sulfates and sodium azide, followed by coupling with a terminal alkyne in the presence of copper catalyst. These reactions are carried out in water under mild and heterogeneous conditions without using any additional ligands.

ChemInform Abstract: Copper‐Catalyzed Double Borylation of Silylacetylenes: Highly Regio‐ and Stereoselective Synthesis of syn‐Vicinal Diboronates.

AbstractIn the presence of copper catalyst, silylacetylene and aryl‐substituted alkynylsilanes undergo regio‐ and stereoselective bis‐borylation to afford products of type (III)/(V).

Catalytic, Conjugate Reduction‐Aldol Addition Reaction of β′‐Oxoalkyl α,β‐Unsaturated Carboxylates

AbstractIntramolecular conjugate reduction‐aldol addition reactions of β′‐oxoalkyl α,β‐unsaturated carboxylates were performed in the presence of copper catalysts generated in situ from copper salts, phosphine ligands and silanes. Moderate to good yields and high diastereoselectivities were obtained in 15 min to 3 h using bis[(2‐diphenylphosphino)phenyl] ether as the ligand.

Evaluation of Food Grade Corn Oil for Electrical Applications

Petroleum-based insulating liquids are applied in several items of electrical power equipment, in which they serve as a dielectric as well as a coolant. However, these oils are environmentally toxic and inflammable, require costly fire protection schemes and deluge systems. To overcome this problem, seed-based vegetable oils have been investigated since these are biodegradable, non-toxic, and posses high fire point. In this experimental investigation, a local brand of seed-based corn oil is evaluated so as to be adopted as a viable dielectric fluid. It was characterized through a series of dielectric and physio-chemical properties and compared with mineral insulating oil. Results show that its 60 Hz breakdown strength is much higher than the mineral oil, while tan δ values satisfy IEC-60156 set criteria. Higher values of permittivity will enable favorable field distribution across oil-cellulose composite insulation. Under oxidation in presence of copper catalyst, it exhibits much less degradation than in mineral oil since its acidity is decreased. It therefore offers a more cost effective replacement solution, in particular for electrical applications in under developed and developing countries where the mineral-based oils are expensive due to a price hike in petroleum crudes.

DFT Studies on the Carboxylation of the C–H Bond of Heteroarenes by Copper(I) Complexes

In this study, we have used density functional theory to identify a new mechanism for the formation of carboxylate compounds from heteroarenes, such as benzoxazole, in the presence of copper catalysts. This new mechanism involves the formation of a carbene intermediate that is indirectly stabilized by the electron-releasing copper. This intermediate carbene can isomerize to the experimentally observed resting state of the catalytic cycle, but it is the intermediate carbene itself that has the greater reactivity toward CO2 and that leads to the final carboxylate product via a lower-energy pathway. Our findings demonstrate the importance of considering metal-stabilized carbenes in such reactions. Our findings also suggest that this carbene intermediate can act as a nucleophile in other organometallic reactions.

ChemInform Abstract: Copper‐Catalyzed Intramolecular Dehydrogenative Aminooxygenation: Direct Access to Formyl‐Substituted Aromatic N‐Heterocycles.

AbstractTreatment of N‐allyl‐2‐aminopyridines or N‐allylamidines with O2 in the presence of copper catalyst allows a direct production of formyl‐substituted imidazole skeletons from acyclic substrates.