Kinetic Model of the PTC Aminolysis of 4-Nitrophenyl Acetate with Solid Potassium Glycinate

A mechanism of phase-transfer catalysis in a solid/liquid system was proposed during akinetic investigation of the aminolysis of 4-nitrophenyl acetate with solid potassium glycinate in chlorobenzene in the presence of 18-crown-6. The quantitative parameters were determined for all the stages of the catalytic cycle, including the distribution of the reagents between the phases and the chemical reactions that occur.     

Phase-Transfer Aminolysis of 4-Nitrophenyl Acetate with Amino Acid Salts in the System Liquid-Solid. Kinetics of the Reaction in the Organic Phase

In the phase-transfer system solid potassium aminoacetate-crown ether-chlorobenzene, the fraction of the nucleophile-catalyst complex trasferred to the organic phase does not exceed 1% of the amount of the solid phase. Nevertheless, the reactivity of the crown ether complex with potassium aminoacetate is sufficient to ensure the aminolysis to proceed in the organic phase at an appreciable rate.     

Synthesis of Novel Crown Ether-Squaramides and Their Application as Phase-Transfer Catalysts

This work presents the synthesis of six new phase-transfer organocatalysts in which the squaramide unit is directly linked to the nitrogen atom of an aza-crown ether. Four chiral skeletons, namely hydroquinine, quinine, cinchonine (cinchonas), and α-d-glucopyranoside were responsible for the asymmetric construction of an all-carbon quaternary stereogenic center in α-alkylation and Michael addition reactions of malonic esters. We investigated the effects of these different chiral units and that of crown ethers with different sizes on catalytic activity and enantioselectivity. During extensive parameter investigations, both conventional and emerging green solvents were screened, providing valuable α,α-disubstituted malonic ester derivatives with excellent yields (up to 98%).     

左旋多巴Schiff碱的合成及其不对称相转移催化烷基化

通过天然左旋多巴与不同芳香醛酮的反应, 合成出5种左旋多巴Schiff碱5a～5e, 其中5c～5e是文献中未见报道的化合物. 然后以这些左旋多巴Schiff碱为底物, 通过不对称相转移催化烷基化反应, 合成出具有光学活性的甲基多巴及其类似物. 同时, 研究探讨了不同相转移催化剂及不同反应条件对左旋多巴Schiff碱甲基化反应的影响.     

Phase-Transfer Catalyzed Alkylation and Cycloalkylation of 2-Mercaptoquinazolin-4(3H)-One

Solid/liquid phase-transfer catalyzed alkylation of 2-mercaptoquinazolin-4(3H)-one at 25°C by different organohalogen compounds in the presence of tetrabutylammonium bromide as a catalyst underwent, exclusively, S-monoalkylation or S- and N-, di-, or cycloalkylation, depending on the nature of alkylating agents.     

Porphyrin Clathrates. Crystal Structures of Two Unexpected Products Obtained by Solvothermal Reactions of Pt-tetra(4-carboxyphenyl)porphyrin with Copper Acetate

The X-ray crystal structure of IX, perchlorate salt of R-(–-2-ethyl-N-benzyl-4,7,19,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene has been determined. In the molecule, the protonated nitrogen atom participates in two N-HO hydrogen bonds. The unusually high proton affinity of aza crown ether leads to the formation of diastreomer instead of complex formation with chiral R-(+)-1-phenyl ethyl ammonium perchlorate and S-(–)-1-phenyl ethyl ammonium perchlorate. The complex ability of host ethers was evaluated in terms of structural modification.     

Oxidation of Benzyl Halides to Aldehydes and Ketones with Potassium Nitrate Catalyzed by Phase-Transfer Catalyst in Aqueous Media

The catalytic oxidation of benzyl halides to aldehydes and ketones in aqueous media was studied under relatively mild reaction conditions by using phase-transfer catalyst combined with potassium nitrate and 10% aqueous potassium hydroxide solution. As a result, a simple high-yield procedure has been developed.     

Reaction Mechanism in Ionic Liquids: Kinetics and Mechanism of the Aminolysis of 4‐Nitrophenyl Acetate

In this work, we report a kinetic study of the reactions of the title compound with secondary alicyclic amines at different temperatures in acetonitrile and several ionic liquids (ILs). From this study, we have described that the reactions in MeCN and in the studied ILs occur by a concerted mechanism and that the activation parameters are sensitive to the structural properties of the ILs. The pKa values of all amines used in both MeCN and ILs were determined.     

Synergism in catalytic halogen-exchange fluorination of 4-chloronitro- and dichlorotetrafluorobenzenes

Synergism was studied in catalytic halogen-exchange fluorination of 4-chloronitro- and dichlorotetrafluorobenzenes. The synergistic effect in the fluorination of chloroaromatic compounds with potassium fluoride was mainly attributed to separation of the activation functions of catalysts with respect to substrate molecules.     

Preparation of Copolymer of Salen-crown Ether Complexes and its Catalytic Activation for Molecular Oxygen

In order to mimic the function of cytochrome P-450, synthetic porphyrin and quasi-porphyrin metal complexes have been employed1. This kind of metal complexesshowed high activity and stability in catalytic oxidation of hydrocarbon compound withmolecular ox…     

4-(4-氯苯氧基)-2-氯苯乙酮的催化合成及微波促进作用

二芳醚;微波辐射;定位选择性;4-(4-氯苯氧基)-2-氯苯乙酮的催化合成及微波促进作用     

Time-parameter Method for Studying Kinetics of Consecutive First-order Reactions in Calorimeter

Thermogravimetric analysis (TG) was used in this work to study the degradation kinetics of industrial PVC plastisols. In order to model the pyrolitic degradation of plastisols in nitrogen, a kinetic model based on phenomenological considerations was developed. Two different processes were observed during the first degradation stage. The model parameters, such as activation energies and pseudo orders of reaction, were calculated using a non-linear regression analysis. The model developed was able to describe the degradation behaviour both in isothermal and in dynamic modes. The results of such analysis were applied to obtain long-term data from short-term experiments as an engineering approach to evaluate the thermal resistance of plastisols. This revised version was published online in July 2006 with corrections to the Cover Date.     

4′-N-烷基(芳基)-氨甲基苯并-18-冠醚-6及高聚物支载和硅胶支载冠醚的合成

本文报道新冠醚4′-N-烷基-和4′-N-芳基-氨甲基苯并-18-冠醚-6及聚苯乙烯珠体和硅胶支载冠醚的合成。后二者均可用作相转移催化剂。聚苯乙烯珠体支载的苯并-18-冠醚-6催化溴辛烷与氰化钾、氰化钠、或醋酸钾的取代反应时,活性较上述高聚物支载的苯并-15-冠醚-5为高。     

室温离子液体中乙酸钠和氯苄催化合成乙酸苄酯

在多种1,3-二烷基咪唑和烷基吡啶室温离子液体中考察了较温和条件下乙酸 钠和氯化苄作用合成乙酸苄酯反应。在反应温度下（60 ℃）,熔融的三水合乙酸 钠与离子液体相混溶,氯苄同乙酸钠作用得到乙苄酯,它与四氟硼酸1-乙基-3-甲 基咪唑离子液体不溶而分层。反应结束后产物乙酸苄酯可直接倾析得到,乙酸苄酯 产率达到90%,纯度超过99%。此离子液体催化体系简化了产物分离,离子液体可以 重复使用。     

Time-Resolved IR-Thermographic Detection and Screening of Enantioselectivity in Catalytic Reactions

Simple monitoring of lipase- and transition metal catalyzed asymmetric esterifications [Eq. (1)] and opening of epoxides [Eq. (2)] can be achieved by IR thermography. Thus, a new method is available for screening of enantioselectivity in catalytic reactions.     

Kinetics of Photocationically Curable Formulations Involving Glycerol Diglycidyl Ether and Phenyl Glycidyl Ether

Kinetic analysis of formulations based on glycerol diglycidyl ether and phenyl glycidyl ether were carried out in the presence of sulfonium salt as initiator at 35 mW cm^?2using photo differential scanning calorimeter and the final conversion was found to increase with an increase in phenyl glycidyl ether content. The effects of formulation monomer ratios at three different temperatures were studied. The variations in the observed kinetic parameters can be related to increase in mobility of reactive species with temperature, distance of counter ion from the propagating cationic center, as well as extent of crosslinking reaction which controlled the course and duration of the reaction. The applicability of autocatalytic kinetic model was also evaluated and the system underwent early gelation and the activation energy decreased with an increase in phenyl glycidyl ether content. Analysis of stable photocured films containing glycerol diglycidyl ether and phenyl glycidyl ether showed better thermal stability than rigid films obtained with glycerol diglycidyl ether.     

Aminolysis ofO-alkylO-4-nitropyenyl chloromethylphosphonates in reverse micellar solutions of the nonionic surfactant

The reaction ofn-hexylamine withO-alkylO-4-nitrophenyl chloromethylphosphonates in toluene solutions of poly(ethylene glycol)-600 monolaurate (PM) has been studied by spectrophotometry. The reverse micelles of the nonionic surfactant increase more than tenfold the observed rate constant of aminolysis. The catalytic activity of the surfactant is practically independent of the alkyl radical length of phosphonate. An increase in the concentration of amine results in a decrease in the catalytic efficiency. The character of the dependence of the rate constant on the concentration of PM is affected by the alkyl chain length of the substrate. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1735–1738, September, 1998.     

Synthesis of Methyl 4,6-Di-O-ethyl-α-d-glucopyranoside-Based Azacrown Ethers and Their Effects in Asymmetric Reactions

Carbohydrate-based crown ethers have been reported to be able to generate asymmetric induction in certain reactions. Previously, it was proved that the monosaccharide unit, the anomeric substituent, and the sidearm could influence the catalytic activity of the monoaza-15-crown-5 macrocycles derived from sugars. In order to gain information about the effect of the flexibility, 4,6-di-O-ethyl-glucoside-based crown compounds were synthesized, and their efficiency was compared to the 4,6-O-benzylidene analogues. It was found that the absence of the two-ring annulation has a negative effect on the enantioselectivity in liquid-liquid two-phase reactions: in the Darzens condensation of 2-chloroacetophenone and in the epoxidation of chalcone. The same trend was observed in the solid-liquid phase Michael addition of diethyl acetamidomalonate. Surprisingly, in the solid-liquid phase cyclopropanation of benzylidenemalononitrile, one of the new catalysts was highly enantioselective (99% ee).     

Investigations on Substituent and Solvent Effects of Solvolysis Reactions. VIII. The Influence of Water and Nonaqueous Solvents on the Imidazolysis of 4-Nitrophenyl Acetate

The aminolysis reaction of 4-nitrophenyl acetate with imidazole was investigated in water, acetonitrile, propylene carbonate, and 1,4-dioxane at different temperatures. the observed rates can be evaluated with the help of a reaction mechanism consisting of two competitive reaction paths; the first is the bimolecular nucleophilic substitution of the phenol moiety by imidazole; the second path is performed via general base catalysis by a second imidazole molecule. The rate constants of the bimolecular reaction are quantitatively correlated with the four-parameter Taft–Kamlet equation for solvent effects on chemical reactions. A qualitative interpretation of the data shows that the two reaction paths are influenced to the same extent by the solvent.