Catalytic Amounts Of Copper Research Articles

Highly efficient immobilization of Cinchona alkaloid derivatives to silica gel via click chemistry

Click chemistry was adapted to the immobilization of various Cinchona alkaloid derivatives bearing alkyne functionality onto azide-modified silica gel surfaces. The developed protocol employs very mild reaction conditions, with catalytic amounts of copper(I) iodide (1–5 mol %) in acetonitrile at room temperature, ensuring complete chemical integrity of the multi-functional ligands. The utility of this approach is demonstrated by the attachment of didehydroquinine tert-butylcarbamate to azido-grafted silica gel to produce an effective chiral stationary phase for HPLC enantiomer separation. A comparison of the chromatographic behavior of this click-immobilized phase with that of a commercially available thioether-linked chiral stationary phase revealed very similar performance characteristics for various model analytes. This observation suggests that the click-immobilization may offer an appealing alternative to the established silica gel-grafting technologies, allowing for the specific benefits of high and readily controllable loading levels under noninvasive conditions.

Copper(I) Chloride Mediated Cyclization of Optically Active 2,3-Allenoic Acids or 1:1 Salts of Optically Active 2,3-Allenoic Acids with Chiral Amines

Copper(I) chloride mediated cyclization of optically active 2,3-allenoic acids or 1:1 salts of optically active 2,3-allenoic acids with chiral amines was developed. The reaction of optically active 2,3-allenoic acids in methanol requires only a catalytic amount of copper(I) chloride, while the reaction of the 1:1 salts of optically active 2,3-allenoic acids with chiral amines needs one equivalent of copper(I) chloride and should be carried out in dichloromethane to ensure high efficiency of chirality transfer.

A Simple Procedure for the Synthesis of Functionalized 1,3-Butadienes and Cyclopentenones from Fischer Carbene Complexes

Consecutive treatment of alkenyl carbene complexes with lithium enolates derived from methyl ketones and iodine leads to functionalized 1,3-butadiene derivatives containing both electron-donating and electron-withdrawing groups. Functionalized bicyclic cyclopentenones are easily available by sequential treatment of dihydropyranyl carbene complexes with lithium enolates, iodine, and catalytic amounts of copper(II) triflate.

Palladium(II)‐Catalyzed Synthesis of Isoxazolidines: Using a Catalytic Copper Acetate and Molecular Oxygen as the Cooxidant

An environmentally friendly process is reported for the palladium(II)‐catalyzed cyclofunctionalization of allylic hydroxylamine derivatives using a catalytic amount of copper(II) acetate and molecular oxygen as the cooxidant.

2,3,4,5-Tetrakis(dimethylsilyl)thiophene: The First 2,3,4,5-Tetrasilylthiophene

2,3,4,5-Tetrakis(dimethylsilyl)thiophene (1), the first 2,3,4,5-tetrasilylthiophene, was synthesized by the reaction of 2,3,4,5-tetrabromothiophene with chlorodimethylsilane in the presence of magnesium and a catalytic amount of copper(I) cyanide. The dimethylsilyl groups of 1 considerably affect the structure and the electronic properties of the thiophene ring, which was revealed by molecular orbital calculations and UV spectroscopy.

Copper Catalyzed Cyclopropanation of 1,2,3,4-Tetrahydropyridin-2-ones with Trimethylsilyldiazomethane: A Facile and Selective Synthesis of 2-Aza-3-oxobicyclo[4.1.0]heptanes

The reactions of a series of 1,2,3,4-tetrahydropyridin-2-ones with trimethylsilyldiazomethane using catalytic amounts of copper(II) triflate in refluxing 1,2-dichloroethane yielded exclusively 3-oxo-2-azabicyclo[4.1.0]-heptanes in good yields. The application of ultrasonic radiation enhanced the reaction rate and allowed the reactions to be conducted at room temperature.

Aerobic oxidation of phenol to quinone with copper chloride as catalyst in ionic liquid

Aerobic oxidation of 2,3,6-trimethyl-phenol to trimethyl-1,4-benzoquinone with 2.5 mol% copper(II) chloride as catalyst in ionic liquid 1- n-butyl-3-methyl-imidazolium chloride, [BMIm]Cl, with n-butanol as co-solvent affording 86% yield provides a new alternative to the copper(II) chloride catalysed aerobic oxidation. The advantage of this catalytic system is that only a catalytic amount of copper(II) chloride is necessary. This catalytic system is also applicable for oxidation of 2-methyl-1-naphthol to 2-methyl-1,4-naphthoquinone. This catalytic reaction was systematically investigated under different conditions.

Direct Formation of 2,3,5‐Trichloropyridine and its Nucleophilic Displacement Reactions in Ionic Liquid

Reaction of trichloroacetaldehyde and acrylonitrile in the presence of a catalytic amount of copper (I) chloride in ionic liquid afforded 2,3,5‐trichloropyridine, fluorination of which with KF and CsF in ionic liquid afforded 3,5‐dichloro‐2‐fluoropyridine and 5‐chloro‐2,3‐dichloropyridine. Reaction of 2,3,5‐trichloropyridine, 3,5‐dichloro‐2‐fluoropyridine, or 5‐chloro‐2,3‐dichloropyride with 2‐(4‐hydroxyphenoxy)propionates in ionic liquid afforded the corresponding 2‐aryloxylpropionates in good yields.

Diazo reactions with unsaturated compounds: VIII. Reaction of 1,3-butadiene and isoprene with aromatic and aliphatic-aromatic triazenes in the presence of sulfur(IV) oxide

1,3-Butadiene and 2-methyl-1,3-butadiene react with 1,3-diphenyltriazene, 1,3-di-p-tolyltriazene, and 1-aryl-3,3-dimethyl-1-triazenes in a sulfur(IV) oxide-saturated water-acetic acid-acetone solution containing NaCl or hydrochloric acid, and catalytic amounts of copper(I) chloride to form 1,4-arylsulfonyl-chlorination products.

Diazo Reactions with Unsaturated Compounds: VII. Vinyl p-Methylphenyl and Vinyl p-Nitrophenyl Ethers in the Meerwein Reaction

Vinyl p-methylphenyl ether in aqueous acetone at pH 3-4 in the presence of catalytic amounts of copper(II) chloride reacts with arenediazonium chlorides to form arylacetaldehydes. Vinyl p-nitrophenyl ether under the same conditions fails to react with arenediazonium chlorides.

Friedel—Crafts Reaction of Indoles with N‐Silyl‐N,O‐acetal Catalyzed by Cu(OTf)2 in the Presence of TMSCl Leading to Indolyl Primary Amines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Friedel–Crafts reaction of indoles with N-silyl- N, O-acetal catalyzed by Cu(OTf) 2 in the presence of TMSCl leading to indolyl primary amines

A catalytic amount of copper(II) trifluoromethanesulfonate (Cu(OTf) 2) in the presence of trimethylchlorosilane (TMSCl) effectively promoted the aminomethylation of indoles bearing a variety of functional groups with a N-silyl- N, O-acetal in good to excellent yields.

A General and Mild Copper-Catalyzed Arylation of Diethyl Malonate

[reaction: see text] A general method for the synthesis of alpha-aryl malonates is described. The coupling of an aryl iodide and diethyl malonate in the presence of Cs(2)CO(3) and catalytic amounts of copper(I) iodide and 2-phenylphenol affords the alpha-aryl malonate in good to excellent yields. The mild reaction conditions and high levels of functional group compatibility make this an attractive synthetic alternative to previous methods.

Thiocyanatoarylation of Diethylene Glycol Diacrylate

The example of diethylene glycol diacrylate was used to demonstrate the possibility of thiocyanatoarylation both by one and by two multiple bonds of compounds with two isolated multiple bonds. The reactions of arenediazonium tetrafluoroborates with diethylene glycol diacrylate in aqueous acetone (1:2) in the presence of catalytic amounts of copper gave 1-acryloyloxy-2-[2-(2-thiocyanato-3-arylpropionyloxy)ethoxy]ethanes. The latter were reacted with arenediazonium tetrafluoroborates in aqueous acetone (1:3) to obtain 1-[2-(2-thiocyanato-3-arylpropionyloxy)ethoxy]-2-(2-thiocyanato-3-arylpropionyloxy)ethanes via thiocyanatoarylation by two multiple bonds.

Reformatsky-type aldol reactions of 4-bromo-4,4-difluoroacetoacetate with aldehydes and ketones

In the presence of zinc and a catalytic amount of copper(I) chloride, 4-bromo-4,4-difluoroacetoacetate 4 reacted with a series of aromatic aldehydes and aryl alkyl ketones to give the corresponding δ-hydroxyl-γ,γ-difluoro-β-ketoesters 6 in good to excellent yields under mild conditions.

Preparation of AB-type diblock copolymers containing poly-(2,6-dimethyl-1,4-phenylene oxide) and methyl methacrylate or styrene blocks

High molecular weight poly-(2,6-dimethyl-1,4-phenylene oxide) (PPO) is obtained from 2,6-dimethylphenol (DMP) by oxidative coupling polymerization. The polymerization is accomplished by passing oxygen through a solution of DMP, a catalytic amount of copper(I) salt, and amine in an organic solvent. High molecular weight PPO is a useful material for engineering thermoplastic applications because of its outstanding physical and chemical properties. However, the use of neat poly-PPO is insignificant as a commercial product because of its high melt viscosity. The commercially available products are generally blends of PPO with high-impact polystyrene. Recently, low molecular weight PPO has attracted considerable interest as starting materials for the preparation of block copolymers, graft copolymers, macromonomers, and star-type polymers of well-defined architectures. Low molecular weight PPO with a narrow molecular weight distribution can be prepared by the precipitation polymerization of DMP in the solvent/nonsolvent mixture under the action of Cu(I) Cl/amine-catalyst and oxygen or by the redistribution of PPO with functional phenols. Tingerthal et al. carried out the synthesis of an ABA-type triblock copolymer containing PPO (A) and polysulfone (B) blocks. Servens et al. studied the preparation of a diblock copolymer with PPO and 1,4polyisoprene segments. More recently, VanAert et al. prepared diblock copolymers by the reaction of phenolterminated polystyrene with PPO. The controlled/“living” radical polymerization such as copper-catalyst-mediated atom transfer radical polymerizations (ATRP) has been utilized for the synthesis of well-defined polymers with narrow molecular weight distributions. ATRP involves the activation and deactivation of a propagating chain end as a result of the reversible atom transfer reaction between a metal salt and alkyl halides. A wide variety of monomers such as styrenes, acrylates, and acrylonitrile have been used for ATRP. To the best of our knowledge, this is the first report on the synthesis and characterization of AB-type block copolymers with well-defined PPO and methyl methacrylate (MMA) blocks. Also, a sample of block copolymer containing PPO and styrene (St) segments was achieved. The PPO oligomers with activated halogen end groups were used as macroinitiators for ATRP.

Cu2+ -induced low density lipoprotein peroxidation is dependent on the initial O2 concentration: an O2 consumption study.

Atherosclerotic plaques form in the arterial intima, where low density lipoprotein (LDL) is thought to be oxidatively modified at sites which may contain catalytic amounts of copper in the presence of low O2 tension. We have investigated O2 consumption during LDL peroxidation induced by Cu2+ ions in vitro and found two phases: a lag phase followed by a phase of rapid O2 consumption. The length of the lag phase was dependent on Cu2+ and on initial O2 concentrations; increasing either decreased the lag time; however, LDL. concentration had no effect. LDL-induced Cu2+ reduction, however, was not affected by low initial O2 concentrations, suggesting that O2 is not required for LDL-mediated reduction of Cu2+. Following the lag phase, O2 consumption was dependent upon LDL or initial O2 concentrations; Cu2+ concentrations had little effect, suggesting that the propagation phase is more dependent on the presence of LDL lipids and O2 as substrates for the reaction. In summary, LDL peroxidation takes place in the presence of Cu2+ at low O2 tension; however, the reaction is dependent upon initial O2 concentrations; increases shorten the lag phase and accelerate O2 consumption.

Intramolecular Copper- and Rhodium-Mediated Carbenoid Reactions of α-(Propargyloxy)silyl-α-diazoacetates

Copper(I) triflate catalyzes the transformation of α-[(2-alkynyl)oxy]silyl-α-diazoacetates 1a–g into 1,2-bis(2,5-dihydro-1,2-oxasilol-4-yl)ethenes 2 and/or 2H-1,2-oxasilines 3. With rhodium(II) perfluorobutyrate as catalyst, 1a–e furnish only 3 but no 2. Bicyclic 2-methoxyfurans 6 are formed when 1a,c,e (containing terminal alkyne functions) are treated with catalytic amounts of copper(I) chloride. The experimental observations are explained in terms of metal-mediated intramolecular cyclopropenation and subsequent metal-assisted ring-opening of the strained bicyclic cyclopropene leading to vinylcarbene-metal complexes. An unusual autoxidation of 2H-1,2-oxasilines 3a,c,e is also described.

Copper(II) Chloride Dihydrate: A Catalytic Agent for the Deprotection of Tetrahydropyranyl Ethers (THP Ethers) and 1-Ethoxyethyl Ethers (EE Ethers)

Tetrahydropyranyl ethers (THP groups) and 1-ethoxyethyl ethers (EE groups) are removed upon refluxing in 95% EtOH or Me2CO–H2O (95:5) in the presence of a catalytic amount of copper(II) chloride dihydrate (2–5 mol%).

Copper(II) Chloride Dihydrate: A Catalytic Agent for the Deprotection of Tetrahydropyranyl Ethers (THP Ethers) and 1-Ethoxyethyl Ethers (EE Ethers)

Tetrahydropyranyl ethers (THP groups) and 1-ethoxyethyl ethers (EE groups) are removed upon refluxing in 95% EtOH or Me2CO–H2O (95:5) in the presence of a catalytic amount of copper(II) chloride dihydrate (2–5 mol%).