Phase-transfer Catalytic Activity Research Articles

{Mo72Cr30} nanocluster as a novel self-separating catalyst for hydrogen peroxide olefin epoxidation

Phase-transfer catalytic epoxidation activity of nanosized {Mo72Cr30} Keplerate polyoxometalate in ethanol in the presence of hydrogen peroxide is exploited. The nanocluster acts as a homogeneous catalyst upon treatment with hydrogen peroxide, while it can be easily filtered and reused as a heterogeneous catalyst. The high catalytic activity and durability of catalyst was demonstrated.

Comparative study of chemically immobilized and conventional homogeneous ionic liquids as phase-transfer catalysts for the N-alkylation of heterocyclic compounds

Various ionic liquids (ILs) were screened for their phase-transfer catalytic (PTC) activity using the N -alkylation of nitrogen heterocycles as the model reaction. Immobilized ILs behaved extremely well and proved to be far better catalysts than conventional homogeneous PTCs in terms of their stability, easy recovery, and reusability. The investigation also demonstrated that quaternary tetraalkylammonium salts offer very high catalytic activity, whereas aromatic heterocyclic tetravalent nitrogen catalysts (imidazolium- and pyridinium-based salts) were poorly active.

ChemInform Abstract: Phase-Transfer Catalytic Activity of Phthalocyanines in the Alkylation of Ambident Anions.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Preparation of Quaternary Phosphonium-Type Triphase Catalysts and Rela-tionship between Chemical Structure and Phase Transfer Catalytic Activity

Preparation of Quaternary Phosphonium-Type Triphase Catalysts and Rela-tionship between Chemical Structure and Phase Transfer Catalytic Activity

Phase Transfer Catalytic Activity of Immobilized Dibenzo-18-Crown-6 for Butyl Benzoate Synthesis

在交联聚乙烯醇（CPVA）微球表面固载冠醚二苯并-18-冠-6（DBC）,从而制得三相相转移催化剂DBC-CPVA;在此基础上,以苯甲酸钾与溴代正丁烷的酯化反应为模型反应体系,重点研究固体催化剂DBC-CPVA的相转移催化性能,考察主要因素对液-固-液三相相转移催化反应的影响.结果表明,在本研究体系中,水相中的苯甲酸钾与有机相中的溴代正丁烷可顺利地发生酯化反应,这一结果显示出固载于DBC-CPVA表面的DBC与K＋离子形成的络合物阳离子,能有效地将苯甲酸根负离子转移至有机相,使酯化反应顺利地进行.有机相的极性越强,酯化反应的速率越快,溴代正丁烷的转化率越高;有机相与水相体积比为1：4时,酯化反应具有最大的速率,溴代正丁烷的转化率可达70%.固体催化剂DBC-CPVA循环使用8次,催化活性保持稳定.

Phase-transfer catalytic synthesis and hypocholesterolemic activity of thiazino[3,2-a]benzimidazole and its silicon analog

The reaction of 2-mercaptobenzimidazole with 1,3-dichloropropane or bis(chloromethyl)dimethylsilane in the two-phase catalytic system of solid K2CO3-18-crown-6-toluene at 111°C leads to a selective formation of tricyclic benzimidazole sulfides in 56 and 92% yields. The synthesized compounds were tested as hypocholesterolemic agents.

Research on the Phase-Transfer Catalytic Activity of Hexaalkylguanidium Salts

グアニジンのアルキル化の最終生成物として得られるヘキサアルキルグアニジウム塩の相間移動触媒能について検討した．採用したグアニジウム塩は，置換基およびその組み合わせの異なる12種の対称型および非対称型であり，これらはいずれもグアニジンあるいはモノ置換グアニジンとアルキル化剤との相間移動反応により合成した．各種グアニジウム塩の触媒能を有機相を出発相とする反応および水相を出発相とする反応のおのおのについて調べた．比較対照には4級アンモニウム塩のテトラブチルアンモニウムアイオダイド（TBAI）を用いた．有機相を出発相とする反応では触媒能は大略グアニジウム塩≧テトラブチルアンモニウムアイオダイドとなり，グアニジウム塩内の比較では親油性の高いものほど高い触媒能を示した．一方，水相を出発相とする反応では触媒能は大略テトラブチルアンモニウムアイオダイド>グアニジウム塩となり，グアニジウム塩内の比較では親油性の高いものほど高い触媒能を示した．しかし，いずれの反応においてもグアニジウム塩中ヘキサベンジルグアニジウム塩はほとんど触媒効果を示さず，その原因が相間移動反応条件下での強塩基による加水分解にあることを明らかにした．さらに，グアニジウム塩の触媒作用機構および有機相を出発相とする反応における高い触媒能をグアニジウム塩の構造と関連付けて考察した．

Phase-behavior and solid–liquid phase-transfer catalytic activity of tetrabutylammonium bromide

The addition of water to tetrabutylammonium bromide (TBABr)/benzene/sodium bromide ternary component systems induced the separation of TBABr-rich liquid phase (L phase) prior to the appearance of an aqueous phase (W phase). The L phase was assumed to be a bicontinuous phase similar to a microemulsion based on the phase composition. TBABr catalyzed the “solid–liquid” phase-transfer reaction of decyl methanesulfonate with sodium bromide either when the L phase was fully hydrated or after a distinct W phase was formed. The phase-transfer catalytic activity was correlated to the phase behavior of TBABr/benzene/water/NaBr four-component system. The difference and similarity between TBABr and tetrabutylphosphonium bromide (TBPBr) were discussed based on the microstructure of the phases formed by TBABr and TBPBr under the phase-transfer catalytic reaction conditions.

Phase Behavior and Phase-Transfer Catalysis of Tetrabutylammonium Salts. Interface-Mediated Catalysis

The phase behavior and component composition of the coexisting phases in the tetrabutylammonium bromide (TBABr)/benzene/water/NaBr four-component system were strongly influenced by the temperature, TBABr content, and NaBr concentration. The phase-transfer catalytic activity of TBABr for the reaction of decyl methanesulfonate with sodium bromide was closely related to the phase behavior. Under O (oil-rich phase) + L (TBABr-rich liquid phase) + W (aqueous phase) triphase conditions, the influences of temperature and stirring speed on the phase-transfer catalytic activity were small compared with those under O + W biphase conditions. The addition of other quaternary salts that were able to form w/o aggregates in the O phase enhanced the TBABr catalytic activity even under O + W conditions. The relationship between phase behavior and catalytic activity of tetrabutylammonium chloride or iodide (TBACl or TBAI) was also examined. The results strongly suggested that the catalysis of TBAX was attributable to the interfacial reactions of TBAX with the substrate. The interface includes the water-oil microinterface formed in the microemulsion-like L phase as well as the bulk water-oil interface.

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.

Synthesis and phase-transfer catalytic activity of novel chiral crown ethers immobilized onto polystyrene supports

Polymer-supported novel optically active crown ethers were prepared by the reaction of chiral crown ethers derived from L-(+)-tartaric acid and 4-chloromethylated polystyrene resins crosslinked with 2 mol% of divinylbenzene. The ring substitution which indicates percentages of functionalized unit of the obtained polymers was in the range of 12–33%. The phase-transfer catalytic activity of the polymer-bound crown ethers has been studied on the reaction of 1-halo-octane with NaI or KI under liquid/liquid/solid tri-phase conditions. The catalyst with 18-crown-6 unit exhibited higher activity than the catalyst with 15-crown-5 unit. The activity of the catalyst with 18-crown-6 moiety for the reaction of 1-chloro-octane with KI was independent of catalyst particle size and increased with decreasing the degree of ring substitution, and the reaction rates were considered to be controlled only by the intrinsic reactivity at active site. On the other hand, the activity for the reaction of 1-bromo-octane with KI were dependent on catalyst particle size and exhibited maximum near 15–20% ring substitution, and the reaction rates were concluded to be limited by both the intrinsic reactivity and the intraparticle diffusion of reactants. The recovered catalyst could be reused repeatedly without a decrease in the activity.

Microenvironmental effect on phase-transfer catalytic activity of polymeric formamides

Polymeric formamides (Pl) were prepared by the copolymerization of N-methyl- N-( p-vinylbenzyl)formamide (MVFA) with styrene by AIBN at 60°C. Similarly copolymerization of MVFA with other hydrophobic monomers such as p-fluorostyrene, p-tert-butylstyrene, and p-trimethylsilylstyrene afforded the corresponding polymers (P2-P4), respectively. These polymers displayed the catalytic activity for the reaction of n-octyl bromide with alkali-metal thiocyanates in liquid-liquid two-phase system. The catalytic activity of P2-P4 was superior to that of P1. This finding was understood by considering that the degree of desolvation of nucleophile could be increased by using more hydrophobic monomers instead of styrene to lead the enhancement of reaction rate. The polymer composition which shows the maximum catalytic activity depends strongly on alkali-metal cations in attacking agents.

Phase-transfer catalytic activity of polymer-supported ammonium and phosphonium salts in oxidation of benzyl alcohol with hydrogen peroxide

Quaternary ammonium or phosphonium salts, immobilized on polymeric support, were obtained by polymer-analogous reactions on ‘gel-type’ styrene-divinylbenzene copolymers and by trans-quatemization of the ammonium groups to phosphonium groups. Polymeric catalysts with degrees of functionalization of 0.15–2.78 mmole g −1 were used in the oxidation of benzyl alcohol with hydrogen peroxide. The activity of the single -onium salts increases as a consequence of association of ammonium and phosphonium salts on the polymeric support. The activity of polymer-supported ammonium and phosphonium salts increases with the number of carbon atoms contained in the alkyl radicals of the -onium and of the functionalization degree with phosphonium groups. Addition of RuCl 3·3H 2O to the reaction media increases the activity of the phase-transfer catalysts.

Amphiphilic Graft Copolymers as Phase-Transfer Catalysts in a Solid-Liquid System

Abstract Amphiphilic graft copolymers consisting of a hydrophobic backbone and poly(oxyethylene) (PEO) side chains were employed as solidliquid phase-transfer catalysts (PTC) in the substitution of octylbromide by solid potassium phenoxide in toluene. A wide variety of structures were synthesized via ester substitution of poly(phthalimidoacrylate) (PPIA) or poly(phthalimidoacrylate-co-styrene) [poly(PIA-co-St)] with amino-functionalized methoxy-PEO (MPEO-NH2). The phase-transfer catalytic activity (PTA) of these soluble graft copolymers was studied as a function of the structure of the backbone, the length of the side chains, and the graft density. The graft copolymers of a high degree of grafting showed PTA higher than that of parent PEOs. GPC was used to study the behavior of the graft copolymers in toluene at 90°C. It is believed that the phase-transfer reaction is accelerated in the PEO microphase.

Synthesis and phase-transfer catalytic activity of polystyrene resins containing hydroxyl groups and crown ether structures

Polystyrene resins with crown ether structures and hydroxyl groups adjacent to the macrorings were prepared by the reaction of crosslinked polystyrene resins containing epoxide groups with monoaza-15-crown-5 or monoaza-18-crown-6. The polymeric catalysts with 30–40% ring substitution exhibited high activity for the dehydrobromination of 2-bromoethylbenzene with aqueous KOH under tri-phase conditions. The active site of the catalysts was suggested to have a structure in which the K + ion was bound by the cooperative coordination of the crown ring donors and the alkoxide anions in the sidearms.

Synthesis and phase-transfer catalytic activity of polymer-supported poly(ethylene glycol)s

Polymer-supported poly(ethylene glycol)s with diol structures were prepared by the reaction of poly(ethylene glycol) (PEG) with crosslinked polystyrene resins containing epoxide groups, in the presence of NaH. The polystyrene-bound PEGs had both singly bound structures, produced by a 1:1 reaction between the epoxide groups and PEG, and doubly bound structures, produced by the reaction of one mole of PEG with two moles of the epoxides. The fraction of singly bound structures depended on the percentage of ring substitution of the resins, the spacer chain and the length (n) of the PEG oxyethylene unit. Supported PEGs, prepared from 20–40% ring-substituted resins with spaced epoxides and PEGs of n = 4−6, were rich in singly bound structures, and exhibited high phase-transfer catalytic activity for dehydrobromination of organic bromides in the presence of aqueous KOH.

ChemInform Abstract: β‐Cyclodextrin‐Epichlorohydrin Copolymers as Efficient Catalysts in Phase‐Transfer‐Catalyzed Nucleophilic Substitution Reactions.

Copolymers of β-cyclodextrin (β-CD) with epichlorohydrin showed much higher phase-transfer catalytic activity than β-CD in liquid–liquid two-phase nucleophilic displacement reactions. The enhanced efficiency of the polymer catalysts was attributed to the cooperative effect of more than one β-CD group in polymers in bringing a substrate from an organic phase to an aqueous phase.

β-Cyclodextrin–Epichlorohydrin Copolymers as Efficient Catalysts in Phase-Transfer-Catalyzed Nucleophilic Substitution Reactions

Abstract Copolymers of β-cyclodextrin (β-CD) with epichlorohydrin showed much higher phase-transfer catalytic activity than β-CD in liquid–liquid two-phase nucleophilic displacement reactions. The enhanced efficiency of the polymer catalysts was attributed to the cooperative effect of more than one β-CD group in polymers in bringing a substrate from an organic phase to an aqueous phase.

Surface Active Crown Ethers. VIII.

Amphiphilic monoaza crown compounds (2 a-f) and diaza crown compounds (3 b and 4 a-c) bearing side chains with cation-binding ability were prepared by the method shown in Scheme-1. Cloud points, complexing stability constants (log K'1) with alkali metal cations (Na+ and K+) in methanol, and phase-transfer catalytic activity were examined for the products, and the data were compared with those of reference compounds. Among amphiphiles having almost the same HLB (Hydrophile-Lipophile Balance), cloud point height was in order of (5) > (2) > (3 b), (4). This was explained as due to the structural effects of two hydrocarbon chains in the hydrophilic moiety of the surfactants. The cloud points of (2), (3 b) and (4) increased by the addition of an alkali metal salts (NaCl or KCl) as reported in the case of (5). The stability constants (log K'1) of (2) were lower than those of (5) with the same number of ether oxygen atoms, and log K'1 increased with the number of ether oxygens in each series. Log K'1 of diaza crown ether series (3 b, 4 a-c) was reduced by the introduction of ether oxygens. Depending on the reagent used (NaI or KI), (2) and (4) exhibited higher phase-transfer catalytic efficiencies than those of the reference compounds (5 d) and (7). These efficiencies may be closely related to both log K'1 and HLB of the complexes composed of azacrown compounds and the reagents.

Polymer-supported oligo(N-acetyliminoethylenes) new phase transfer catalysts

Oligo(N-acetyliminoethylenes), both free and grafted on polystyrene, polymethacrylate and cellulose were prepared by the ring-opening polymerization of 2-methyloxazoline. Their phase transfer catalytic activity in nucleophilic substitution reactions was examined.