Catalyst In Toluene Research Articles

High yield [ 125I]iodide-labeling of iodinated carboranes by palladium-catalyzed isotopic exchange

We have recently shown the feasibility of palladium-catalyzed isotopic exchange between [ 125I]iodide and 2-iodo- para-carborane. In this work we have modified the methodology and extended its application to a wider range of iodinated carboranes. Thus, by using Herrmann's catalyst in toluene at 100 °C, 2-I- p-, 3-I- o-, 9-I- o-, 9-I- m-carborane, 1-phenyl-3-I- o-carborane and 1,2-diphenyl-3-I- o-carborane have been radiolabeled with 125iodine in high to excellent yields.

Kinetic Modeling of Ethylene−Norbornene Copolymerization Using Homogeneous Metallocene Catalysts

The kinetics of ethylene-norbornene copolymerization to cyclic olefin copolymer has been investigated using homogeneous rac-Et(1-indenyl) 2 ZrCl 2 /methylaluminoxane catalyst in toluene at 70 °C for norbornene/ethylene mole ratios in the range of 3-55. It is shown that the catalyst is ineffective for the homopolymerization of norbornene, but the catalyst activity for the insertion of norbornene into a growing polymer chain increases dramatically in the presence of ethylene. A terminal model has been developed to quantify the kinetic behavior of the copolymerization process, but it was found inadequate to represent the copolymerization kinetics for a broad range of polymerization conditions. To overcome the limitations of the terminal model we developed a penultimate model and excellent agreement between the experimental data and model calculations has been obtained. In particular, it is shown that the penultimate model accurately predicts the effect of bulk phase norbornene concentrations on the polymerization rate.

A highly regio- and stereo-selective hydrostannation reaction of various fluorine-containing internal acetylene derivatives

The hydrostannation reaction of various fluoroalkylated acetylene derivatives with tributyltin hydride was investigated using a variety of catalysts in toluene. Among them, the Et 3B-induced hydrostannation reaction gave the highest regio- and stereo-selectivity. Their selectivity was mostly influenced upon the difference of the substituent X at the aromatic ring of the aryl-substituted internal acetylenes. Thus, the acetylenes having a halogen atom or an electron-donating group as X reacted smoothly with tributyltin hydride, affording the vinylstannane 4 Z exclusively, while the acetylenes having an electron-withdrawing group (X=CO 2Et, NO 2) resulted in the preferential formation of 5 E . The plausible mechanism of the formation of these products was discussed.

Synthesis and optical properties of hyperbranched polyarylenes

Abstract High molecular weight, hyperbranched polyarylenes were synthesized in high isolation yields by the copolycyclotrimerizations of 2,5-diethynylthiophene (1), 4,4′-biphenyldiyne (2), and 2,7-diethynylfluorenes (3) with 1-heptyne (4) and 1-dodecyne (5) using TaCl5–Ph4Sn as the catalyst in toluene. The structures of the polymers were characterized by IR, NMR, TGA, and UV analyses. All the polymers exhibited outstanding thermal stability and emitted strong blue light, whose intensities are higher than that of poly(1-phenyl-1-octyne), a well-known highly emissive polyacetylene. Little red shift was observed in the photoluminescence of the polymer thin films. The polymers strongly attenuated intense pulses of 532 nm laser pulses.

Monodentate Chiral Spiro Phosphoramidites: Efficient Ligands for Rhodium‐Catalyzed Enantioselective Hydrogenation of Enamides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hyperbranched polyarylenes from copolycyclotrimerization

High molecular weight hyperbranched polyarylenes were synthesized in high yields by one-pot copolycyclotrimerizations of 2,5-diethynylthiophene (1), 4,4′-biphenyldiyne (2) and 2,7-diethynylfluorenes (3) with 1-heptyne (4) and 1-dodecyne (5) using TaCl5·Ph4Sn catalysts in toluene. The structures and properties of the polymers were characterized and evaluated by IR, NMR, TGA, UV, fluorescence and optical limiting analyses. All the polymers possess high thermal stability and emit strong blue light upon UV irradiation, whose intensities are higher than that from poly(1-phenyl-1-octyne) (PPO), a well-known highly luminescent disubstituted polyacetylene. Little aggregation-induced red shift in the photoluminescence is observed in the thin films of the polymers.

Synthesis of 2,5-di(2-thienyl)-1 H-pyrrole N-linked with conjugated bridges

The Knorr–Paal reaction of 1,4-di(2-thienyl)-1,4-butanedione with anilines to yield N-substituted-2,5-di-(2-thienyl)-1 H-pyrroles (SNS derivatives) was tested by using different acid catalysts in toluene and acetic acid. Di-SNS derivatives were also synthesized in toluene at reflux in the presence of propionic acid, these mild conditions giving acceptable yields in a one-step procedure.

Zirconocene-catalyzed copolymerizations of ethylene with 5-methyl-1,4-hexadiene as non-conjugated diene

The mixtures of non-conjugated dienes, 4-methyl-1,4-hexadiene and 5-methyl-1,4-hexadiene (MHD), were successfully synthesized by the reaction of isoprene with ethylene using Fe(III)-based catalyst in toluene. The conversion was over 96 mol% on the basis of the initial amount of isoprene used. The production yield for MHD was nearly 50 mol%, the other was polyisoprene. The mixtures were successfully copolymerized with ethylene by using zirconium-based metallocenes. The products were characterized by the combinations of gas chromatography, high temperature gel permeation chromatography,1H NMR,13C NMR, high temperature1H NMR, UV/Visible spectroscopy, and differential scanning calorimetry. It was found that 5-methyl-1,4-hexadiene was active enough to be incorporated into the copolymer chain but the corresponding isomeric material, 4-methyl-1,4-hexadiene, was inactive in metallocene-catalyzed copolymerizations. Specifically, in the zirconocene-catalyzed copolymerizations of ethylene with MHD,ansa-structure catalysts seem to be more efficient than non-bridged type zirconocene. The degree of incorporation of MHD in the resulting copolymers was able to be controlled by the amount of non-conjugated dienes used initially.

Alkylation of N-substituted 2-phenylacetamides: Benzylation of N-(4-nitrophenyl)-2-phenylacetamide

N-(4-Nitrophenyl)-2-phenylacetamide was alkylated with benzyl chloride in the presence of powdered potassium hydroxide at different temperatures and in various solvents in order to establish the reactivity and orientation in the reaction. The reactions were also carried out in the presence of different phase-transfer catalysts in toluene. Product formation was followed by GC. The obtained results were compared to the results of the benzylation of other N-substituted 2-phenylacetamides, especially of N-phenyl-2-phenylacetamide.

Transition-Metal-Catalyzed Reactions of Propargylamine with Carbon Dioxide and Carbon Disulfide

The reactions of propargylamine derivatives with carbon dioxide and carbon disulfide have been systematically examined in the presence of transition-metal catalysts. Pd(OAc)(2) is the best catalyst for the formation of the corresponding oxazolidinones. In addition, we found that, in the reaction of propargylamine with carbon dioxide catalyzed by palladium(0) metal catalyst in toluene, both oxazolidinone 1 and imidazolidinone 2 could be obtained under mild reaction conditions at the same time. The reaction of 1 with primary and secondary amines has been examined. A plausible reaction mechanism for the formation of 2 was proposed. In addition, in this paper, we first disclosed the ligand's effect on this reaction. Using PBu(t)(3) as a ligand with Pd(2)(dba)(3), 1 was exclusively formed in 90% yield.

Solvent-free chelation-assisted intermolecular hydroacylation: effect of microwave irradiation in the synthesis of ketone from aldehyde and 1-alkene by Rh(I) complex

As a green alternative to classical homogeneous catalyst in toluene in closed vessels, the intermolecular hydroacylation of 1-alkenes with aldehydes by Rh(I) complex (Wilkinson catalyst) can be realized efficiently under solvent-free conditions. When coupled to microwave activation, it results in a serious improvement when compared to classical conditions.

“Radical-Controlled” Oxidative Polymerization of 4-Phenoxyphenol by a Tyrosinase Model Complex Catalyst to Poly(1,4-phenylene oxide)

A new concept, “radical-controlled” oxidative polymerization of phenols catalyzed by a tyrosinase model complex, has been proposed. A μ-η2:η2-peroxo dicopper(II) species formed by the reaction between the catalyst complex and dioxygen, reacted with phenol to give “controlled” phenoxy radical−copper(I) intermediate instead of “free” phenoxy radical. The polymerization of 4-phenoxyphenol was performed by the use of the tyrosinase model complexes, (hydrotris(3,5-diphenyl-1-pyrazolyl)borate)copper (Cu(Tpzb)) chloride complex and (1,4,7-R3-1,4,7-triazacyclononane)copper (Cu(LR): R = isopropyl (iPr), cyclohexyl (cHex), n-butyl (nBu)) dichloride complexes. The structures of these complexes were determined by X-ray crystallography, indicating that the order of steric repulsion of the substituents (R) in the Cu(LR) complexes is cHex > iPr > nBu. Very little of C−C coupling dimers were afforded with the Cu(Tpzb) catalyst in toluene or THF, and with the Cu(LiPr), Cu(LcHex), or Cu(LnBu) catalyst in toluene. The sele...

Palladium catalyzed [2+2+1] cyclotrimerization of alkynes: selective synthesis of fulvenes

This is the first report on the selective synthesis of fulvenes via a [2+2+1] cyclotrimerization of alkynes under catalytic conditions. The reactions of aliphatic terminal alkynes 1a– e in the presence of a palladium catalyst in toluene gave the cyclotrimerization products 2a– e, not easily available through the previously known methods, in good to fair yields.

Lipase-catalyzed degradation of polyesters in organic solvents. A new methodology of polymer recycling using enzyme as catalyst.

Enzymatic hydrolytic degradation of aliphatic polyesters in organic solvents has been examined. The degradation of poly(epsilon-caprolactone) took place using Candida antarctica lipase as catalyst in toluene at 60 degrees C to give oligomers with molecular weight of less than 500. The degradation behavior catalyzed by lipase was quite different than an acid-catalyzed degradation (random bond cleavage of polymer). After the removal of the solvent from the reaction mixture, the residual oligomer was polymerized in the presence of the same catalyst of lipase. These data provide a basic concept that the degradation-polymerization could be controlled by presence or absence of the solvent, providing a new methodology of plastics recycling.

Palladium-Catalyzed Three-Component Coupling Reaction of Aryl Halides, Norbornadiene and Alkynols. Convenient Synthesis for Their Ternary Coupling Products

Abstract 2,3-Disubstituted norbornenes were obtained by the Pd/Cu-catalyzed three-component ternary coupling reaction of aryl halides, norbornadiene, and alkynols in the presence of aqueous NaOH and a phase transfer catalyst in toluene at 100 °C in high yields.

Functionalization of organophosphazene trimers: synthesis and characterization of hexakis(dicarboxylic amino acid ester)cyclotriphosphazenes and their salt derivatives

New cyclotriphosphazenes fully substituted with dicarboxylic amino acid esters (aminomalonate, aspartate and glutamate) were synthesized and characterized by means of elemental analysis, IR and multinuclear ( 1H, 13C and 31P) NMR spectroscopies, and X-ray crystallography. The rate of full substitution of hexachlorocyclotriphosphazene with the amino acid esters has been found to be largely dependent on the steric hindrance of the corresponding amino acid esters. The full substitution of the chlorotrimer with aminomalonate was completed in 6 h when the reactants were refluxed in tetrahydrofuran (THF), but the full substitution with aspartate or glutamate required more severe conditions: The substitution with aspartate was completed in 12 h by refluxing the reactants in the presence of n-Bu 4NBr as the catalyst in toluene, but the substitution with glutamate could not be completed even after refluxing for more than two days in the presence of the same catalyst in toluene. To endow the above compounds with the functionality for incorporation of metal moiety, they have been hydrolyzed in aqueous solutions of alkali metal hydroxides to yield the corresponding metal salts, which can afford twelve active sites.

Kinetics of Hydroformylation of Ethylene in a Homogeneous Medium: Comparison in Organic and Aqueous Systems

The kinetics of hydroformylation of ethylene was studied using HRh(CO)(PPh3)3 and [Rh(COD)CI]2/TPPTS catalyst in toluene and water media, respectively. The rates were found to have a first-order dependence on the catalyst concentration. Similar trends were observed with respect to partial pressures of ethylene and carbon monoxide, in both solvents. The difference in the location of the maxima with respect to pressure is due to the poor solubility of the reactants in water as compared to toluene. The major difference observed was a 1.5 order with hydrogen in toluene compared with a first order in water. Rate models were proposed to represent the data observed.

Molecular weight and molecular weight distribution of polyethene obtained withrac-Me2Si(Ind)2ZrCl2/methylaluminoxane

Ethene and propene polymerizations were carried out with the rac-Me 2 Si(Ind) 2 ZrCl 2 (Me = CH 3 , Ind = indenyl)/methylaluminoxane (MAO) catalyst in toluene. The molecular mass distribution index (MMD = M w /M n ) of polypropenes was almost 2,0, while a bimodal MMD was observed for polyethene. The MMD of polyethene was independent of the [Al]/[Zr] ratio and the [Zr] concentration. However, the high molecular weight fraction disappeared when the polymerization was performed either at a low temperature or by using dry MAO. Addition of AlMe 3 to the MAO caused an increase of the low molecular weight fraction at the initial stage of polymerization. The low molecular weight fraction was also increased when the polymerization was conducted in a mixture of toluene and CH 2 Cl 2 as the solvent. From these results, the active species formed in the catalyst system are discussed.

Selective Alkoxycarbonylation of A-Ring Precursors of Vitamin D Using Enzymes in Organic Solvents. Chemoenzymatic Synthesis of 1alpha,25-Dihydroxyvitamin D(3) C-5 A-Ring Carbamate Derivatives(1).

A-Ring modification of 1alpha,25-dihydroxyvitamin D(3) [2, 1alpha,25-(OH)(2)-D(3)] is an important area of analog studies to investigate biological activity of vitamin D-related structures. An efficient synthesis of 1alpha,25-(OH)(2)-D(3) C-5 A-ring carbamate derivatives 19 and amino acid derivatives 21 was developed by applying a two-step chemoenzymatic strategy, involving the enzymatic synthesis of carbonates followed by reaction with amino derivatives. Accordingly, we began the studies of enzymatic alkoxycarbonylation of 1alpha,25-(OH)(2)-D(3) A-ring precursor 7. Candida antarctica lipase (CAL) was found to be the best catalyst in toluene. Regioselective alkoxycarbonylation occurred only at the C-5-(R) hydroxyl group. Good to excellent yields were achieved by chemical reaction of these carbonates with amino derivatives. The procedure provided convenient synthesis of carbamates 19 and 21 under mild reaction conditions.

Kinetic Studies of the Catalytic Oxidation of Toluene to Benzoic Acid in the Liquid Phase

The catalytic oxidation of toluene to benzoic acid in the liquid phase has been studied in an un-stirred tank reactor. Low concentration of acetic acid was added in order to increase the solubility of the catalyst in toluene. The dependence of the rate of reaction on the concentration of toluene catalyst and oxygen pressure was studied. It has been suggested that liquid phase oxidation of toluene to benzoic acid primarily is a diffusion controlled reaction and the order of reaction with respect to oxygen shifts to lower values by stirring.