Water-stable biphasic nanocolloids with potential use as anisotropic imaging probes

Electrified co-jetting of two aqueous polymer solutions followed by a thermal cross-linking step was used to create water-stable biphasic nanocolloids. For this purpose, aqueous solution mixtures of poly(acrylamide-co-acrylic acid) and poly(acrylic acid) were employed as jetting solutions. When the biphasic nanocolloids created by side-by-side electrified co-jetting were thermally treated, a cross-linking reaction occurred between amide groups and carboxylic groups to form stable imide groups. Infrared spectroscopy was employed to monitor the reaction. The quality and the integrity of the resulting biphasic nanocolloids were confirmed by confocal laser scanning microscopy, flow cytometry analysis, and dynamic light scattering. Selective encapsulation of two biomolecules in each phase of the biphasic colloids was maintained even after thermal reaction and suspension in aqueous environment. Well-dispersed spherical colloids with stable dye loadings in each hemisphere were kept intact without aggregation or dissolution for several weeks. Finally, biphasic nanocolloids were selectively surface-modified with a biotin-dextran resulting in water-stable particles to ensure binding of proteins only to a single hemisphere.     

Efficient aldol condensation in aqueous biphasic system under microfluidic conditions

A microfluidic system was applied to aldol reaction in aqueous biphasic medium. Advantageous aspects of microfluidic conditions, that is, efficient mixing, fast heat transfer, and residence time control led to the high-yielding reaction of acetone enolate with even α-proton-containing aldehydes in biphasic aqueous-acetone system, by minimizing the formation of self-condensation products.     

Rhodium-catalyzed [2 + 2 + 2] cyclotrimerization in an aqueous-organic biphasic system

Macrocyclization via rhodium-catalyzed intramolecular [2 + 2 + 2] annulation of triynes has been explored in an aqueous-organic biphasic system. The biphasic system controls the concentration of hydrophobic substrates in the aqueous reaction phase and offers diluted reaction conditions without the use of a slow addition technique. The system also achieves selective cross-annulation between hydrophobic diynes and hydrophilic alkynes.     

Hydroformylation of 2,5‐norbornadiene in organic/aqueous two‐phase system and acceleration by cationic surfactants

The organic/aqueous biphasic hydroformylation of 2,5‐norbornadiene (NBD) was investigated for the first time using HRh(CO)(TPPTS)₃ (TPPTS: trisodium salt of tri(m‐sulphonylphenyl)phosphine) as the catalyst precursor. A comparison was made of homogeneous and biphasic systems. The optimum reaction parameters are discussed and the reaction mechanism is presented. In order to ensure the process attained high activity under moderate conditions, the effect of various cationic surfactants was tested in the biphasic hydroformylation of NBD. The results indicated that the hydroformylation of NBD in the biphasic system exhibited high activity and high selectivity to dialdehyde products under mild conditions. The addition of cationic surfactants markedly accelerated the reaction. A single long‐chain surfactant seemed to exert a greater impact on the hydroformylation of NBD than a double long‐chain surfactant. Moreover, the recycling of aqueous solution containing catalyst with or without surfactant was investigated. In the absence of the surfactant, the aqueous catalyst could be recycled six times without a significant decrease in activity and selectivity. Copyright © 2016 John Wiley & Sons, Ltd.     

Biphasic Enantioselective Fluorescent Recognition of Amino Acids by a Fluorophilic Probe

A fluorophilic fluorescent probe based on a perfluoroalkyl-substituted bis(binaphthyl) compound was designed and synthesized. It displayed a highly enantioselective fluorescence response toward structurally diverse amino acids in a biphasic fluorous/aqueous system with enantiomeric fluorescent enhancement ratio (ef; ΔI_D/ΔI_L) values up to 45.2 (histidine). It can be used to determine the enantiomeric compositions of amino acids and also allows the amino acid enantiomers to be visually discriminated. NMR and mass-spectroscopic investigations provided insights into the observed high enantioselectivity. This biphasic fluorescent recognition was used to determine the enantiomeric composition of the crude phenylalanine products generated by an enzyme-catalyzed asymmetric hydrolysis under various reaction conditions. The fluorous-phase-based fluorescence measurement under the biphasic conditions was able to minimize the interference of other reaction components and thus has potential in asymmetric reaction screening.     

Practical asymmetric enzymatic reduction through discovery of a dehydrogenase-compatible biphasic reaction media

[reaction: see text] An enzyme-compatible biphasic reaction media for the asymmetric biocatalytic reduction of ketones with in situ cofactor regeneration has been developed. In this biphasic reaction media, which is advantageous for reactions at higher substrate concentrations, both enzymes (alcohol dehydrogenase and FDH from Candida boidinii) remain stable. The reductions with poorly water-soluble ketones were carried out at substrate concentrations of 10-200 mM, and the optically active (S)-alcohols were formed with moderate to good conversions and with up to >99% ee.     

温控液/液两相催化进展*

本文以作者在温控水/有机两相及温控非水液/液两相催化领域的研究工作为主线,对这一领域的研究进展作一评述,重点是环绕经典水/有机两相催化体系存在“应用范围受底物水溶性限制”的根本问题展开。特别是对“温控相转移催化”作了较为详细的介绍,同时,按体系介质不同,对氟两相体系、PEG两相体系、离子液体两相体系等非水液/液两相体系以及温控相分离催化分别作了阐述。     

Phase Transfer Controlled Selective Oxidation of Diarylsulfides to Diarylsulfoxides Using Potassium Hydrogen Persulfate

The use of biphasic reaction conditions and a phase transfer catalyst controls the oxidation reaction of potassium hydrogen persulfate with diarylsulfides yielding predominately sulfoxides. This is in contrast to the reaction in polar solvents where sulfones are the major products.     

金属络合物的相转移催化分析与分离

以可简单分离回收、可反复使用为目标，详细介绍了相转移催化的变化发展过 程．通过对溶剂的选择，使得催化剂选择性地溶解在某一液相中，而使产物溶解在 另一液相中，如水-有机两相催化体系；通过温度的变化，简单地实现了在较高温 度下反应为均相体系以提高催化剂的活性，而在较低温度下实现了催化剂与产物不 相溶使得催化剂得以简单分离，如温控型水-有机两相催化体系、氟-有机两相催化 体系、温控型含氟催化剂、温控型有机金属催化剂等．     

温控配体与液／液两相催化

 以作者近年的研究工作为主，对液／液两相催化研究领域取得的进展做一综述．着重介绍了以温控配体为基础的新型液／液两相催化过程温控相转移催化（thermoregulatedphasetransfercatalysis，TRPTC）和温控相分离催化（thermoregulatedphase－separablecatalysis，TPSC）的基本原理及其在高碳烯烃氢甲酰化、芳香硝基化合物的CO选择性还原及烯烃加氢等反应中的应用．基于温控配体在水中的“浊点”特性而提出的温控相转移催化概念，为从根本上解决水／有机两相催化 的适用范围受底物水溶性限制的问题提供了一条新途径．而利用温控配体在某些有机溶剂中存在临界溶解温度（CST）的特性而实现的温控相分离催化，则使在高于临界溶解温度的反应温度时为均相的反应体系，在低温（＜CST）时则分成两相，催化剂自成一相，形成一种具有“均相反应、两相分离”特色的液／液两相催化新体系．     

1,1,3,3-四(全氟己基乙基)二锡氧烷二聚体在环氧化合物开环反应中的催化作用

采用氟碳-有机溶剂两相催化体系,考察了1,1,3,3-四(全氟己基乙基)二锡氧烷二聚体(1)在环氧化合物开环反应中的催化作用.结果表明,催化剂(1)在氟碳-有机溶剂两相体系中使环氧苯乙烯和甲醇的开环反应产率高达95%,¹³CNMR谱表明,开环反应的区域选择性为100%.在氟碳-有机溶剂两相催化体系中以一锅法制备了3-苯基丙酸2-甲氧基-2-苯乙醇酯,收率高,方法简便,催化剂几乎可以定量回收循环使用.     

Acid zeolites as alcohol racemization catalysts: screening and application in biphasic dynamic kinetic resolution

Acid zeolites were screened as heterogeneous catalysts for racemization of benzylic alcohols. The most promising zeolites appeared to be H-Beta zeolites, for which the optimal reaction conditions were studied in further detail. The zeolite performance was compared to that of homogeneous acids and acid resins under similar reaction conditions. In a second part of the research, H-Beta zeolites were applied in dynamic kinetic resolution (DKR) of 1-phenylethanol, which was conducted by means of a two-phase approach and which resulted in yields smoothly crossing the 50% border up to 90%, with an enantiomeric excess of >99%. To explore the applicability of this biphasic methodology, several other substrates were examined in the standard racemization reaction and in the biphasic dynamic kinetic resolution.     

Biphasic asymmetric hydroformylation and hydrogenation by water-soluble rhodium and ruthenium complexes of sulfonated (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl in ionic liquids

A biphasic catalytic system with water-soluble rhodium complexes of sulfonated (R)-2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (labeled as (R)-BINAPS) in ionic liquid BMI·BF₄ has been developed for the asymmetric hydroformylation of vinyl acetate under mild conditions. The corresponding ruthenium complexes have been investigated for the biphasic asymmetric hydrogenation of dimethyl itaconate. The biphasic asymmetric hydroformylation of vinyl acetate provided 28.2% conversion and 55.2% enantiomeric excess when BMI·BF₄–toluene was used as the reaction medium at 333 K and 1.0 MPa for 24 h. The biphasic asymmetric hydrogenation of dimethyl itaconate in BMI·BF₄–ⁱPrOH at 333 K and 2.0 MPa afforded 65% enantiomeric excess with an activity similar to the homogenous analogs. Both biphasic catalytic systems with (R)-BINAPS ligand could be reused several times without significantly decrease in the activity, enantio- and regio-selectivities. The effects of properties of ionic liquid, molar ratio of ligand to rhodium, temperature, pressure and reaction time have been discussed.     

Acid Zeolites as Alcohol Racemization Catalysts: Screening and Application in Biphasic Dynamic Kinetic Resolution

Acid zeolites were screened as heterogeneous catalysts for racemization of benzylic alcohols. The most promising zeolites appeared to be H‐Beta zeolites, for which the optimal reaction conditions were studied in further detail. The zeolite performance was compared to that of homogeneous acids and acid resins under similar reaction conditions. In a second part of the research, H‐Beta zeolites were applied in dynamic kinetic resolution (DKR) of 1‐phenylethanol, which was conducted by means of a two‐phase approach and which resulted in yields smoothly crossing the 50 % border up to 90 %, with an enantiomeric excess of >99 %. To explore the applicability of this biphasic methodology, several other substrates were examined in the standard racemization reaction and in the biphasic dynamic kinetic resolution.     

Preparation of allyl sulfoxides by palladium-catalyzed allylic alkylation of sulfenate anions

Palladium-catalyzed allylic alkylation of sulfenate anions, generated from beta-sulfinylesters by retro-Michael reaction, can take place under biphasic conditions. This new reaction provides a simple, mild, and efficient route to allyl sulfoxides in good yields.     

Homogeneous and biphasic autoxidation of tetralin catalyzed by transition metal salts and complexes

The biphasic autoxidation of tetralin was carried out using various Co, Ni and Mn complexes as catalysts. Cobalt–N,N′-dimethylethylenediamine complex, which is amphiphilic and surface-active, was found to be most effective; it could be easily recovered in a compact emulsion layer after the reaction and could be reused with no apparent loss of activity. The biphasic reaction differs from the homogeneous counterpart in that (1) little hydroperoxide product is formed, (2) there is lesser sensitivity to product inhibition and a greater degree of conversion and (3) there is an easier catalyst recovery and substrate recycle.     

温控离子液体/有机两相体系中纳米Rh催化烯烃氢甲酰化反应

将具有"高温混溶、室温分相"功能的离子液体[CH3(OCH2CH2)16N+Et3][CH3SO3–](ILPEG750)与甲苯-正庚烷组成的两相体系用于纳米Rh催化的烯烃氢甲酰化反应中,在优化的反应条件下,1-辛烯转化率和醛收率分别为99%和91%.催化剂经简单分相即可与产物分离,且可连续使用8次,其活性基本保持不变.     

超临界二氧化碳/聚乙二醇两相体系的性质及其在催化反应中的应用

非均相催化过程中常常出现产物的转化率低、选择性差的问题, 而均相催化过程往往具有优异的催化性能, 但是却受制于催化剂、产物难于分离而达到循环使用的缺点. 近年来两相催化体系的发展为这些问题的解决提供了一条新途径. 超临界二氧化碳/聚乙二醇参与的两相体系是使用超临界二氧化碳作流动相, 聚乙二醇作为另一溶剂之一, 用于固定和稳定催化剂, 进行有机催化反应. 其显著特点是: 可在反应的同时实现分离的操作, 可实现均相催化过程的连续化. 综述了超临界二氧化碳/聚乙二醇体系的相行为及其性质, 并介绍了其在催化合成反应中的应用.     

Fluorous biphasic hydrolytic kinetic resolution of terminal epoxides

Although application of light-fluorous techniques facilitates the isolation of reaction products from the hydrolytic kinetic resolution (HKR) of terminal epoxides catalysed by cobalt complexes of salen ligands, the extension of the original fluorous biphasic approach to this reaction is far from being a trivial exercise. The nature of the counter anion has a dramatic effect on the catalytic activity of heavily fluorinated chiral (salen) cobalt(III) complexes. Excellent enantioselectivities are obtained in the fluorous biphasic HKR of 1,2-hexene oxide when fluorinated anions are introduced (e.e.s up to 99% both for the diol and the epoxide), with C₈F₁₇COO^- affording reaction rates even higher than those observed with non-fluorous systems.     

Using soluble polymers in latent biphasic systems

A new strategy for carrying out reactions with a soluble polymer-bound reagent or catalyst is described. In this latent biphasic process, a solvent mixture at the cusp of immiscibility is prepared and used to carry out a reaction under homogeneous conditions. Then, after the reaction is complete, this mixture is perturbed by the addition of solvent or some other perturbing agent to produce a biphasic mixture. The product-containing phase is then separated under liquid/liquid conditions from the polymer-containing phase. The generality of this process is demonstrated using both dye-labeled polymers as surrogates for polymer-bound catalysts and with various polymer-bound organic and transition metal catalysts or reagents. In cases where a polymeric catalyst is used, the addition of fresh solvent and substrate reforms the original mixture allowing facile reuse of the catalyst.