A LIMITATION OF REUSING THE CATALYST IN TRI-LIQUID-PHASE CATALYTIC SYSTEMS

This work demonstrates important factor influencing the reusability of the phase transfer catalyst in the third liquid phase in addition to the role of the possible loss of catalyst due to the dissolution of the catalyst into the aqueous and organic phases. When the catalyst might react with the byproducts, in addition to reacting with the organic substrate and aqueous nucleophile, it would lose its catalytic activity. The substitution reaction between the organic substrate and an aqueous nucleophile (sodium phenolate) with tetra-n-butylammonium bromide as a phase-transfer catalyst was employed as a model reaction and was performed in a batch reactor. Three organic substrates, including allyl bromide, n-butyl bromide, and ethyl 2-bromoisobutyrate, were tested. Each of the third liquid phases formed in these tri-liquid-phase catalytic systems was utilized three times to observe the change in the activity of the catalyst. The catalyst in the third liquid phase can be reused without any loss of its catalytic activity when allyl bromide or n-butyl bromide is utilized as the organic substrate; however, the catalytic activity declines when ethyl 2-bromoisobutyrate is the organic reactant. Therefore, the organic reactant plays a crucial role in determining whether the catalyst can be reused or not.     

ANALYSIS OF FACTORS AFFECTING THE SYNTHESIS OF ALLYL PHENYL ETHER BY TRI-LIQUID-PHASE CATALYSIS

In order to improve the selectivity of allyl phenyl ether (ROPh), the main product, in the etherification of allyl bromide (RBr) and sodium phenolate (NaOPh) with tetra-n-butylammonium bromide (QBr) as a phase-transfer catalyst, the technique of tri-liquid-phase phase-transfer catalysis, instead of the liquid-liquid one, was employed. The reaction was performed in a batch reactor, and the factors affecting the conversion and selectivity were investigated. The possibility of reusing the phase-transfer catalyst was also evaluated. Experimental results indicate that the addition of a small amount of Na₂CO₃ will benefit the formation of a third liquid phase and enhances both the conversion of RBr and the overall yield of ROPh. Both the conversion and the overall yield are maximal when the mole fraction of QBr in the mixture of NaOPh and QBr is about 0.3. A high reaction temperature enhances the conversion and the overall yield. Under optimal conditions, complete conversion and near 100% yield can be obtained within 10 minutes. Although the reaction rate by the tri-liquid-phase catalysis is slightly lower than that observed with the same amount of catalyst by conventional liquid-liquid phase-transfer catalysis, the selectivity of ROPh is higher and the catalyst can be easily reused by the reuse of the third liquid phase without any loss of its catalytic activity in the former case. Because the reuse of catalyst was found to be feasible, the production of ROPh with a continuous-flow reactor becomes possible.     

ANALYSIS OF FACTORS AFFECTING THE SYNTHESIS OF ALLYL PHENYL ETHER BY TRI-LIQUID-PHASE CATALYSIS

In order to improve the selectivity of allyl phenyl ether (ROPh), the main product, in the etherification of allyl bromide (RBr) and sodium phenolate (NaOPh) with tetra-n-butylammonium bromide (QBr) as a phase-transfer catalyst, the technique of tri-liquid-phase phase-transfer catalysis, instead of the liquid-liquid one, was employed. The reaction was performed in a batch reactor, and the factors affecting the conversion and selectivity were investigated. The possibility of reusing the phase-transfer catalyst was also evaluated. Experimental results indicate that the addition of a small amount of Na₂CO₃ will benefit the formation of a third liquid phase and enhances both the conversion of RBr and the overall yield of ROPh. Both the conversion and the overall yield are maximal when the mole fraction of QBr in the mixture of NaOPh and QBr is about 0.3. A high reaction temperature enhances the conversion and the overall yield. Under optimal conditions, complete conversion and near 100% yield can be obtained within 10 minutes. Although the reaction rate by the tri-liquid-phase catalysis is slightly lower than that observed with the same amount of catalyst by conventional liquid-liquid phase-transfer catalysis, the selectivity of ROPh is higher and the catalyst can be easily reused by the reuse of the third liquid phase without any loss of its catalytic activity in the former case. Because the reuse of catalyst was found to be feasible, the production of ROPh with a continuous-flow reactor becomes possible.     

Formation of a Third Liquid Phase and Its Reuse for Dibenzyl Ether Synthesis in a Tetraalkylammonium Salt Phase Transfer Catalytic System

This paper describes the formation of a third liquid phase in a phase transfer catalytic system in the presence of benzyl alcohol and potassium hydroxide, where dodecane and tetraalkylammonium bromide serve as organic solvent and catalyst, respectively. In this kind of system, a symmetrical ether (dibenzyl ether) was synthesized from benzyl chloride and benzyl alcohol at 323 K. In particular, the investigation demonstrates that the observed reaction rate constant depends on the length of the alkyl group of the catalyst. Tetrabutylammonium bromide exhibits the highest catalytic activity among the catalysts explored. With respect to the reuse of the third liquid phase, the results confirm that there is no decrease in phase transfer catalytic activity in three consecutive runs.     

相转移催化合成4-苯基-1，4-二氢吡啶化合物

以苯甲醛、乙酰乙酸乙酯、醋酸铵为原料,并分别以四丁基碘化铵,四丁基溴化铵和十六烷基三乙基溴化铵为相转移催化剂在水溶液中一步合成4-苯基-2,6-二甲基-1,4-二氢吡啶3,5-二甲酸二乙酯。以四丁基碘化铵为催化剂反应温度为90℃,反应时间为7小时,催化剂用量为5％时收率最高达75％,其催化活性高于另外两种催化剂,该方法具有操作简便,无污染,水溶液可以重复使用等优点。     

三种不稳定化合物临界温度和临界压力的测定

用独特的毛细管流动法装置测定物质的临界温度和临界压力,该法具有体积小、升温迅速和受热均匀等特点,适于测定不稳定化合物的临界性质。以正己烷、1 庚烯为标准试剂,对该装置进行了考核。测定了溴乙烷、丙烯酸丁酯、烯丙醇3种物质的临界温度及临界压力。首次提供了丙烯酸丁酯、烯丙醇的临界数据,并且校正了溴乙烷临界温度和临界压力值。     

聚乙二醇催化合成正丁基苯基醚

以乙醇为溶剂、聚乙二醇为相转移催化剂，氢氧化钾为碱，从正丁基溴和苯酚合成了正丁基苯基醚。当0．1mol苯酚，0．3mol正丁基溴，乙醇为溶剂，在氢氧化钾和聚乙二醇400存在下，加热2h正丁基苯基醚收率达96．7％。     

离子液体协同催化合成游离氨基酸酯

以L-氨基酸和醇为原料,酸性离子液体辅以少量强酸性阳离子交换树脂作催化剂,直接酯化合成了8种游离的L-氨基酸酯,并用1HNMR对产物进行了表征。通过L-苯丙氨酸正丁酯的合成对离子液体的活性进行了考察,结果表明,所选用的11种离子液体在反应过程中均起到了一定的催化作用和助溶作用。其中,[Hmim][HSO4]效果较好,在重复使用后,显示了较好的稳定性,是氨基酸酯化反应理想的催化剂和助溶剂。     

乙酸正丁酯制备实验的改进

文章对有机化学实验教材中乙酸正丁酯的制备方法进行了改进,把环境友好催化剂纳米复合硅钨杂多酸引入到有机化学实验教学中．并与传统乙酸正丁酯实验（硫酸催化）进行比较。具有产品后处理简单,催化荆可重复使用,对环境污染小等优点。     

Synthesis of n‐butyl phenyl ether by tri‐liquid‐phase catalysis using poly(ethylene glycol)‐600 as a catalyst – analysis of factors affecting the reaction in a batch reactor

As the second part of a series of studies on the synthesis of n‐butyl phenyl ether (ROPh) by tri‐liquid‐phase catalysis, this work examines the factors affecting the reaction between n‐butyl bromide (RBr, organic substrate) and sodium phenolate (NaOPh, aqueous nucleophile) with poly(ethylene glycol)‐600 (PEG‐600) as a phase‐transfer catalyst. The reaction is performed in a batch reactor at 45–85 °C for 2 h while the agitation speed is fixed at 1000 rpm. Experimental results indicate that the individual mole fractions of NaOPh and PEG‐600 slightly affect the reaction, while the total amount of these components exerts significant influence. When the mole fraction of PEG‐600 is 0.5, the reaction rate and the conversion of RBr are the highest. No byproducts are formed in the course of the reaction. The system using a non‐polar organic solvent might obtain a higher conversion compared with a weakly polar one owing to a higher concentration of PEG‐600 in the third liquid phase. Furthermore, adding NaOH facilitates the reaction to obtain a higher reaction rate than adding other kinds of salt because the addition of a base results in the formation of a third liquid phase. The catalytic ability of PEG with average molecular weight of 600 gmol^?1 is far higher than that with average molecular weight of 200, 400 and 1000 because PEG‐600 possesses an appropriate chain length which can tightly associate with Na⁺ to form the complex of PEG‐600‐Na⁺OPh^? for reacting with RBr. In addition, this nucleophilic substitution reaction is found to be pseudo‐first‐order with respect to RBr. © 2001 Society of Chemical Industry     

Kinetics of the allylation of phenoxide by polyethylene glycol in a two-phase reaction

Polyethylene glycol (PEG) was used as the phase transfer catalyst in the two-phase allylation of phenoxide with allyl chloride. The kinetics of the reaction both in the organic phase and in the aqueous phase was studied in detail based on the ion-extraction mechanism. The reaction rates both in the organic and aqueous phases were increased by PEG. The concentration of phenoxide in the organic phase results from adding PEG followed by a reaction second order in the concentration of phenoxide in the aqueous phase. This is due to the ability of PEGs to form complexes with sodium cations. In the aqueous phase, the PEG will enhance the solubility of allyl chloride.     

离子液体中二步法合成钙拮抗剂尼群地平

以间硝基苯甲醛、乙酰乙酸甲酯及合成的3-氨基-2-丁烯酸乙酯和间硝基苯甲醛、乙酰乙酸乙酯及3-氨基-2-丁烯酸甲酯在离子液体1-丁基吡啶四氟硼酸盐中环合合成第二代1,4-二氢吡啶类钙拮抗剂尼群地平,收率分别为93%和94%,离子液体回收套用至少3次,产物收率没有明显降低。     

Kinetics for phenolysis of ethyl 2‐bromoisobutyrate via phase‐transfer catalysis in a solid–liquid system

The kinetics of phase‐transfer catalyzed etherification of sodium phenoxide with ethyl 2‐bromoisobutyrate to produce ethyl 2‐phenoxyisobutyrate in a solid–liquid system has been investigated. Being catalyzed by the quaternary ‘onium salts, the reaction was carried out in a stirred batch reactor to explore the effects of various operating variables. At a temperature of 80 °C and a molar ratio of tetra‐n‐butylammonium bromide to sodium phenoxide equal to 0.372, 94% conversion was obtained after 4 h, and no other side products were observed. A kinetic model of pseudo‐first‐order reaction accompanied by catalyst deactivation was proposed to describe the overall reaction. A deactivation function was employed to evaluate the kinetic parameters. The decay of catalytic activity was mainly caused by the deposition of the salts produced on the surface of solid particles. The results show that the initial reaction rate was not influenced by the agitation rate when exceeding 350 rpm, but the deactivation rate increased with increasing stirring speed and the amount of catalyst used. The intrinsic organic reaction was conducted by the phase‐transfer catalytic intermediate. The order of reactivity for different phase‐transfer catalysts was determined as tetra‐n‐butylphosphonium bromide > tetra‐n‐butylammonium bromide > tetra‐n‐butylammonium iodide ≈ tetra‐n‐butylammonium hydrogen sulfate ≈ Aliquat 336. The apparent activation energy for tetra‐n‐butylammonium bromide was estimated as 51.4 kJ mol⁻¹. This work provides an improved method for synthesizing phenolic substances in solid–liquid phases and preventing unfavorable side reactions. © 2000 Society of Chemical Industry     

Amino-functionalized Ionic Liquid as an Efficient and Recyclable Catalyst for Knoevenagel Reactions in Water

The Knoevenagel condensation of aromatic aldehydes with malononitrile and ethyl cyanoacetate using amino-functionalized ionic liquid, 1-aminoethyl-3-methylimidazolium hexafluorophosphate as catalyst was successfully performed in aqueous media. The catalyst can be recycled and reused at least six times without apparently loss of activity.      

Metal Triflate‐Catalyzed Regio‐ and Stereoselective Friedel–Crafts Alkenylation of Arenes with Alkynes in an Ionic Liquid: Scope and Mechanism

In the metal triflate‐catalyzed hydroarylation of alkynes, employing an ionic liquid dramatically enhanced the catalytic activities, resulting in broadening the scope of substrates (arenes and alkynes). In some cases, even reactions that were not possible in conventional organic solvents proceeded smoothly in ionic liquids. Moreover, the ionic liquid phase containing catalyst could be readily recovered by simple decantation of the organic layer after reaction and reused for the following runs without any significant loss of activity. Mechanistic studies including ¹³C NMR analysis of reaction intermediates and isotope experiments confirmed for the first time that this type of reaction proceeds via vinyl cationic intermediates.     

Selective oxidation of alcohols with H2O2 catalyzed by long chain multi-SO3H functionalized heteropolyanion-based ionic liquids under solvent-free conditions

Two novel long chain multi-SO₃H functionalized heteropolyanion-based ionic liquids were prepared and characterized. They as homogeneous catalysts showed high catalytic activity in selective oxidation of alcohols with 35% aqueous hydrogen peroxide under solvent-free conditions without adding any phase transfer catalyst. Two ionic liquids can be recovered readily and reused five times without any significant loss in their catalytic activities.     

Kinetics and extraction of phenol in phase-transfer catalyzed reaction

Under two-phase conditions, the feasibility of extracting/removing phenol from aqueous alkaline medium via reaction with allyl bromide dissolved in dichloromethane was investigated using phase-transfer catalysts in a stirred cell. The effects of the concentrations of base, reactant and catalyst, and temperature were also evaluated to obtain the optimum reaction conditions. According to these results, the extractive efficiency of phenolic substances varied strongly with increasing base concentration. The specific extraction rate, diffusivity, mass transfer coefficient and distribution coefficient of an intermediate product were determined to explain the reaction mechanism by the proposed theoretical model. During reaction, the concentration of the intermediate product in the organic phase was also measured, and a simulation method was used to examine the mass transfer behavior of the intermediate product in the liquid-liquid system.     

Br(o)nsted酸性离子液体合成及催化酯化反应应用

以苄基氯、N-乙基咪唑、浓硫酸为原料,成功合成出一种含有磺酸基的新型Br(o)nsted酸性离子液体,通过IR、1H NMR对其结构进行了表征.将其应用于催化乙酸和乙醇的酯化反应,考察其反应条件和循环使用性能.结果表明最佳反应条件为:反应时间90 min,催化剂用量5%,反应温度80 ℃.此条件下产率为72.35%.离...     

3,5‐Bis(n‐perfluorooctyl)benzyltriethylammonium Bromide (F‐TEBA): An Efficient,Easily Recoverable Fluorous Catalyst for Solid‐Liquid PTC Reactions

A readily available 3,5‐bis(perfluorooctyl)benzyl bromide and triethylamine were reacted under mild conditions to give 3,5‐bis(n‐perfluorooctyl)benzyltriethylammonium bromide ( F‐TEBA ), an analogue of the versatile phase‐transfer catalyst, benzyltriethylammonium chloride (TEBA), containing two fluorous ponytails. This perfluoroalkylated quaternary ammonium salt was successfully employed as a catalyst in a variety of reactions run under solid‐liquid phase‐transfer catalysis (SL‐PTC) conditions. Thus, being both hydrophobic and lipophobic, F‐TEBA could be quickly recovered in quantitative yields, and reused without loss of activity over several reaction cycles.     

A facile route for synthesis of long-chain RAC-1-S-alkylglycerols

Alkyl allyl thioethers were prepared by reaction of longchain primary thiols in hexane with allyl bromide in the presence of a phase transfer catalyst (tetrabutylammonium bromide), and aqueous alkali and were hydroxylated to rac-1-S-alkylglycerols by means of a novel reagent, cetyltrimethylammonium permanganate, in dichloromethane.