Microwave-promoted solvent-free synthesis of N-(diphenylmethylene)glycine alkyl esters

The efficient synthesis of N-(diphenylmethylene) glycine alkyl esters was achieved for the first microwave irradiation under solvent-free condition, using PEG or quaternary ammonium salts as phase transfer catalysts (PTCs). Under the optimum conditions, N-(diphenylmethylene) glycine alkyl esters were obtained in excellent yields in most cases.     

Phase Transfer Catalysis: Preparation of Alkyl Thiocyanates

Phase transfer catalysis has been employed for many nucleo-philic substitution reactions.¹ Generally these reactions have employed quaternary ammonium salts as catalysts. Among the displacement reactions reported is the formation of thiocyanates.² Tertiary amines have also been used as catalysts for phase transfer generation of carbenes.³ Recently we reported the preparation of alkyl cyanides to be catalyzed by amines under phase transfer conditions.⁴     

Mesoionic Carbene Cobalt Complexes as Multipurpose Catalyst Precursors for Hydrosilylation and Dihydropyrimidinone Synthesis

Metalation of CH₂OH-substituted triazolium salts with CoCl₂ under basic conditions affords C,O-bidentate chelating carbene Co(III) complexes ( 3a , 3b ), while analogous phenyl-substituted triazolium salts produce monodentate carbene Co(II) complexes ( 3c , 3d ). The distinct substituent-induced properties of the metal centers were demonstrated by electrochemical measurements and catalytic activities in two specific processes. The complexes showed appreciable activity in the reduction of C=O bonds through hydrosilylation, with methoxybenzene-functionalized triazolylidene Co(III) complex 3a achieving a high selectivity towards aldehydes vs. ketones with turnover frequencies (TOFs) up to 200 h⁻¹. The C,O-chelate systems were also active catalysts in the Biginelli process, a one-step three-component reaction for efficient dihydropyrimidinone synthesis. Optimization of reaction conditions provides high activity with complex 3a , reaching TOFs of 800 h⁻¹, the highest activity known for cobalt NHC complexes to date.     

Efficient Synthesis of α,β‐Epoxy Carbonyl Compounds in Acetonitrile: Darzens Condensation of Aromatic Aldehydes with Ethyl Chloroacetate

The Darzens reaction of ethyl 2‐chloroacetate ( 1 ) with aromatic aldehydes 2 in the presence of polymer‐supported or nonsupported quaternary ammonium salts proceeds under mild conditions by phase‐transfer catalysis to give the corresponding epoxides 3 in satisfactory yields (Tables 1 and 2). With both MeCN as solvent and polystyrene‐supported catalysts, diastereoselective Darzens reactions proceed in excellent yields and short times, with a fair degree of stereoinduction.     

Study of Ground State Interactions of Enantiopure Chiral Quaternary Ammonium Salts and Amides,Nitroalkanes, Nitroalkenes,Esters, Heterocycles,Ketones and Fluoroamides

Chiral phase-transfer catalysis provides high level of enantiocontrol, however no experimental data showed the interaction of catalysts and substrates. ¹H NMR titration was carried out on Cinchona and Maruoka ammonium bromides vs. nitro, carbonyl, heterocycles, and N−F containing compounds. It was found that neutral organic species and quaternary ammonium salts interacted via an ensemble of catalyst ⁺N−C−H and (sp²)C−H, specific for each substrate studied. The correspondent BArF salts interacted with carbonyls via a diverse set of ⁺N−C−H and (sp²)C−H compared to bromides. This data suggests that BArF ammonium salts may display a different enantioselectivity profile. Although not providing quantitative data for the affinity constants, the data reported proofs that chiral ammonium salts coordinate with substrates, prior to transition state, through specific C−H positions in their structures, providing a new rational to rationalize the origin of enantioselectivity in their catalyses.     

Microwave-promoted solvent-free synthesis of N-(diphenylmethylene)glycine alkyl esters

The efficient synthesis of N-(diphenylmethylene) glycine alkyl esters was achieved for the first microwave irradiation under solvent-free condition,using PEG or quaternary ammonium salts as phase transfer catalysts(PTCs).Under the optimum conditions, N-(diphenylmethylene) glycine alkyl esters were obtained in excellent yields in most cases.     

Catalytic investigations of calix[4]arene scaffold based phase transfer catalyst

Calix[4]arene scaffold based quaternary ammonium salts as multi-site phase transfer catalysts were prepared and their catalytic activities were investigated for Darzens condensation, O/N-alkylation reactions and ethyl benzene oxidation. These calix[4]arene based multi-site phase transfer catalysts showed significant high catalytic activity as compared to single-site phase transfer catalysts.     

组合化学法筛选聚苯乙烯固载季铵盐相转移催化剂研究(I)

利用组合化学方法合成了一个含有60种不同结构的聚苯乙烯固载季铵盐相转移催化剂的催化剂库,以有外加碱条件下亲核取代反应为探针反应,利用迭代法从中筛选出了活性最高的催化剂,建立了一种快速合成和筛选聚苯乙烯固载季铵盐相转移催化剂的方法。     

手性相转移催化剂及其不对称催化反应

综述了手性季铵盐和手性冠醚两类手性相转移催化剂及其在不对称催化反应（包括加成，取代，氧化及还原等反应）中的应用，参考文献９７篇。     

Sustainable Triazine-Based Dehydro-Condensation Agents for Amide Synthesis

Conventional methods employed today for the synthesis of amides often lack of economic and environmental sustainability. Triazine-derived quaternary ammonium salts, e.g., 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM(Cl)), emerged as promising dehydro-condensation agents for amide synthesis, although suffering of limited stability and high costs. In the present work, a simple protocol for the synthesis of amides mediated by 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) and a tert-amine has been described and data are compared to DMTMM(Cl) and other CDMT-derived quaternary ammonium salts (DMT-Ams(X), X: Cl⁻ or ClO₄⁻). Different tert-amines (Ams) were tested for the synthesis of various DMT-Ams(Cl), but only DMTMM(Cl) could be isolated and employed for dehydro-condensation reactions, while all CDMT/tert-amine systems tested were efficient as dehydro-condensation agents. Interestingly, in best reaction conditions, CDMT and 1,4-dimethylpiperazine gave N-phenethyl benzamide in 93% yield in 15 min, with up to half the amount of tert-amine consumption. The efficiency of CDMT/tert-amine was further compared to more stable triazine quaternary ammonium salts having a perchlorate counter anion (DMT-Ams(ClO₄)). Overall CDMT/tert-amine systems appear to be a viable and more economical alternative to most dehydro-condensation agents employed today.     

季铵盐插层蒙脱土及其去除海洋卡盾藻的研究

利用插层法制备了5种季铵盐改性的蒙脱土,通过FTIR、XRD和DTG等表征表明5种季铵盐已成功插入蒙脱土中;随后以中国典型赤潮藻海洋卡盾藻(Chattonella marina)为研究对象,考察了5种季铵盐改性蒙脱土的除藻效果。发现以双溴化十四烷基二甲基乙基溴化铵改性的蒙脱土在用量为8mg·L-1时,24h内对海洋卡盾藻的去除率最高,可达100%,而未改性蒙脱土在相同条件下除藻率仅为5.64%;除藻效果与除藻剂的结构有密切关系,在官能团相同时,链长数为14的脂肪族季铵盐除藻率最高,24h可达67.03%;在链长数相同时,含吡啶官能团的季铵盐比脂肪族季铵盐除藻率高,24h为33.62%,且随时间延长明显提高。渗溢性评估实验显示,改性蒙脱土经72h浸泡后表观插层率从71.9%降低到69.6%,表明除藻剂在水体中基本不释放。     

聚合物负载手性季铵盐的合成与表征

以金鸡纳生物碱中的辛可宁为原料,氯甲基化聚苯乙烯-聚乙二醇、一缩二乙二醇、二缩三乙二醇、乙二醇等为载体合成了几种聚合物负载的手性季铵盐,并对它们的结构用红外光谱、元素分析、扫描电镜和X射线光电子能谱等测试手段进行了表征。     

Dehydrochlorination of vinylidene chloride-vinyl chloride copolymer by aqueous sodium or potassium hydroxide solutions under two-phase conditions

The reaction of solid copolymer of vinylidene chloride and vinyl chloride with aqueous sodium or potassium hydroxide solutions in the presence of quaternary ammonium or phosphonium salts as phase transfer catalysts gave dehydrochlorinated products with chlorine-substituted polyene structure. Among the catalysts used tetrapropylammonium bromide was the best and potassium hydroxide was more active than sodium hydroxide. The activity of quaternary ammonium salts was discussed in terms of hydrophile–lipophile balance. The effects of temperature and the concentration of the bases and catalysts were investigated to obtain the optimum reaction condition. Treatment of the polymer films and solutions in tetrahydrofuran with aqueous bases under two-phase conditions also produced dehydrochlorinated films and powders.     

A Base‐Free Neutral Phase‐Transfer Reaction System

Although phase‐transfer reactions catalyzed by using quaternary ammonium salts are generally believed to require base additives, we discovered that, even without any base additives, conjugate additions of 3‐substituted oxindoles to nitroolefins proceeded smoothly in the presence of lipophilic quaternary ammonium bromide under water–organic biphasic conditions. The mechanism of this novel base‐free neutral phase‐transfer reaction system is investigated and the assumed catalytic cycle is presented together with interesting effects of water and lipophilicity of the phase‐transfer catalyst. The base‐free neutral phase‐transfer reaction system can be applied to highly enantioselective conjugate addition and aldol reactions under the influence of chiral bifunctional ammonium bromides as key catalysts. The structure of the chiral ammonium enolate intermediate is discussed based on the single‐crystal X‐ray structures of relevant ammonium salts and the importance of bifunctional design of catalyst is clearly explained in the model of intermediate.     

相转移催化合成增塑剂BBP和水杨醛的研究

相转移催化合成增塑剂ＢＢＰ和水杨醛的研究郭锡坤，高文华，曾东宇（汕头大学化学系，汕头５１５０６３）关键词相转移催化，季铵盐，聚乙二醇，邻苯二甲酸丁苄酯，水杨醛，增塑剂邻苯二甲酸丁苄酯（增塑剂ＢＢＰ）是一种优良的增塑剂．邻羟基苯甲醛（水杨醛）不仅是重要...     

相转移催化在高分子化合物合成中的应用

 综述了相转移催化用于高分子化合物合成的主要研究进展．介绍了季铵盐类及冠醚类相转移催化剂在高聚物的亲核取代反应、阴离子开环聚合反应及自由基聚合反应中的应用．重点总结了亲核取代反应中聚苯乙烯类化合物的功能化及化学修饰，包括合成路线、反应机理、温度以及催化剂和溶剂的种类与用量等因素对反应的影响．冠醚类化合物的催化效果略优于季铵盐类化合物，而后者的成本低、毒性小、应用更广泛，其催化的反应应作为今后研究的重点，以期将相转移催化技术尽早用于工业化生产．     

Synthesis of dimethyl carbonate and propylene glycol from transesterification of propylene carbonate and methanol using quaternary ammonium salt catalysts

Summary The synthesis of dimethyl carbonate (DMC) was investigated through the transesterification of propylene carbonate (PC) with methanol using quaternary ammonium salt catalysts. The reaction was carried out in an autoclave at 120-140 oC under carbon dioxide pressure of 250-400 psig. The main by-product was propylene glycol. The quaternary salts of larger alkyl group and more nucleophilic counter anion exhibited higher catalytic activity. Kinetic studies were also performed to better understand the reaction mechanism. Quaternary ammonium chlorides immobilized on polystyrene supports were also tested for their possible uses as heterogeneous catalysts.     

The kinetics and mechanism of the reaction between 1-chloro-2,3-epoxypropane and p-cresol in the presence of basic catalysts

Rate constants for the reaction of 1-chloro-2,3-epoxypropane with p-cresol in the presence of basic catalysts were studied at the temperature range of 71–100°C. It was found that in the presence of sodium p-cresolate, three consecutive reactions proceeded giving the following products: 1-chloro-3-(tolyloxy)-2-propanol (CTP), 1-(p-tolyloxy)-2,3-epoxypropane (TEP) as a main product, and 1,3-di(p-tolyloxy)-2-propanol (DTP). Their rate constants at 71°C were: k₁ = 0.030 ± 0.009, k₂ = 1.58 ± 0.02, and k₃ = 0.033 ± 0.005 dm³/mol · min, respectively. In the presence of quaternary ammonium salts, this process consisted of 5 reactions which led to CTP as a main product as well as TEP and 1,3-dichloro-2-propanol (DCP). The rate constant of CTP formation at 71°C was established, k₁ = 0.130 ± 0.030 dm³/mol · min, as were the ratios of the other rate constants k₂/k₋₄ = 1.5 ± 0.2, k₅/k₋₄ = 20.0 ± 5.0, and k₄/k₁ = 0.6 ± 0.7. Based on the changes in Cl⁻ ion concentration during the reaction, the catalystic activity of quaternary ammonium salts was explained. The kinetic model of these reactions in the presence of basic catalysts has been proposed and appropriate kinetic equations have been presented. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 73–79, 1997.     

A convenient preparation of N- (arenesulfonyl) sulfoximines by oxidation of N- (arenesulfonyl) sulfilimines with sodium hypochlorite in a two phase system

N-(Arenesulfonyl) sulfilimines can be oxidized to the corresponding sulfoximes in high yields with sodium hypochlorite in an AcOEt-H₂O two phase system in the presence of quaternary ammonium salts as catalysts.     

Design of chiral organocatalysts for practical asymmetric synthesis of amino acid derivatives

A series of structurally rigid, chiral quaternary ammonium salts and several chiral sec-amine catalysts derived from commercially available (R)- or (S)-binaphthol have been designed as new C(2)-symmetric chiral phase-transfer catalysts and chiral bifunctional amino-catalysts. These chiral organocatalysts have been successfully applied to the highly practical asymmetric synthesis of various amino acid derivatives.