Effects of organic solvents and ionic liquids on the aminolysis of (RS)-methyl mandelate catalyzed by lipases

The enzymatic resolution of (RS)-methyl mandelate with n-butylamine using lipases in organic solvents (n-hexane, tert-butanol, and chloroform) and ionic liquids [BMIm][BF₄] and [BMIm][PF₆] is reported. The amide configuration is dependent on the organic solvent. When using mixtures of chloroform or tert-butanol/ionic liquids (10:1 v/v) with CAL-B as the catalyst, the amides were obtained in high enantiomeric excess (ee_p >99% and E >200).     

Enantioselective enzymatic resolution of racemic alcohols by lipases in green organic solvents

The effects of two eco-friendly solvents, 2-methyltetrahydrofuran (MeTHF) and cyclopentyl methyl ether (CPME), on the enzyme activity and enantioselectivity of Novozym 435, Candida rugosa lipase (CRL), Porcine pancreas lipase (PPL), Lipase AK, Lipase PS, and Lipozyme, a series of commercial lipases, in the enantioselective transesterfications of racemic menthol, racemic sulcatol and racemic α-cyclogeraniol were studied. Vinyl acetate was chosen as the acyl donor and the reactions were carried out at water activity 0.06. The activity of lipases in CPME was similar to that observed in other largely employed organic solvents [toluene and tert-butyl methyl ether (MTBE)], and was slightly lower in MeTHF. However, for most of the lipases tested, the enantioselectivity was higher in the eco-friendly solvents. Lipase AK exhibited a high enantioselectivity (E = 232) for the resolution of racemic menthol but the reaction rate was low. Lipase formulation (the enzyme was frozen and lyophilized in potassium phosphate buffer without and with 5% (w/v) of sucrose, d-mannitol, or methoxy poly(ethylene glycol)) was tested with this lipase in order to improve its activity, which increased up to 4.5 times, compared to the untreated enzyme. CALB was found to be a useful biocatalyst for the resolution of racemic sulcatol, where high activity and enantioselectivity were obtained (E ≥ 1000). For the resolution of the racemic primary alcohol α-cyclogeraniol, most of the lipases tested were active but not enantioselective, except lipase PS which displayed a moderate enantioselectivity (E = 19). The effect of the presence of a low percentage of two ionic liquids (ILs) 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]) (5% (v/v)) and 1-Butyl-3-methylimidazoliumtetrafluoroborate ([BMIM][BF4]) (1% (v/v)) in the medium was also investigated. Only in the case of CRL the ILs slightly increased the enantioselectivity from E = 91 to E = 103 and E = 120 for [BMIM][TFSI] and [BMIM][BF4], respectively. However, in all cases ILs caused a decrease of enzyme activity.     

Ferric chloride catalyzed photooxidation of alkanes by air in organic solvents

In the presence of catalytic amounts of FeCl₃, alkanes (cyclohexane, n-hexane), toluene and ethylbenzene are oxidized by air oxygen to CH₃CN, (CH₃)₂CO or CH₂Cl₂ under visible light irradiation to yield ketones and alcohols.

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FeCl₃ (, -), CH₃CN, (CH₃)₂CO CH₂Cl₂ .

     

Lipase catalyzed synthesis of macrocyclic lactones in organic solvents

A new method for the preparation of macrocyclic lactones from ω-hydroxyacid methyl esters is described. The approach utilizes intramolecular transesterification catalyzed by lipase in organic solvents. This procedure is also applicable to the synthesis of asymmetric lactones.     

DESs: Green solvents for transition metal catalyzed organic reactions

In this review, the recent development about using DESs as green solvents in transition metal catalyzed organic reactions was highlighted. Firstly, the development of DESs was simply introduced. After presenting the advantages of DESs, transition metals catalyzed organic reactions using DESs as green solvents were classified and introduced in detail. Different transition metals such as Au, metal impregnated on magnetite, Pd and Ru catalyzed organic reactions proceeded smoothly in DESs and gave corresponding products in good yields. And in some cases, the catalytic systems could be recycled up to several times without any decrease in activity.     

DESs: Green solvents for transition metal catalyzed organic reactions

The recent development about using DESs as green solvents in transition metal catalyzed organic reactions was highlighted, and Au, Metal impregnated on magnetite, Pd, Ru catalyzed organic reactions proceeded smoothly in DESs and gave corresponding products in reasonable yields. And in some cases, the catalytic systems could be recycled up to several times.     

Enantioselective acylation of rac-2-phenylcycloalkanamines catalyzed by lipases

The kinetic resolution of some 2-phenylcycloalkanamines was performed by means of aminolysis reactions catalyzed by lipases, with Kazlauskas’ rule being obeyed in all cases. The size of the ring and the stereochemistry of the stereogenic centers of the amines had a strong influence on both the enantiomeric ratio and the reaction rate of these aminolysis processes. Lipase B from Candida antarctica (CAL-B) showed excellent enantioselectivities toward trans-2-phenylcyclohexanamine in a variety of reaction conditions (E >150), whereas lipase A from C. antarctica (CAL-A) was the best catalyst for the acylation of cis-2-phenylcyclohexanamine (E = 34) and trans-2-phenylcyclopropanamine (E = 9).     

Enzymatic synthesis of triglycerides catalyzed by lipases fromPenicillium sp.

Two lipases have been isolated from Penicillium sp.and purified. A synthetase activity of the total lipase preparation has been shown in an aqueous medium and in a system of reversed micelles (RMs) of a surfaceactive agent (SAA) in benzene, and advantages of the reversed-micelle system over an aqueous medium have been demonstrated. Institute of Microbiology, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 41 71 29. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 122–126, January-February, 1995. Original article submitted October 14, 1994.     

Michael additions of primary and secondary amines to acrylonitrile catalyzed by lipases

The present Letter details our findings on the lipase-catalyzed Michael reactions between primary or secondary amines and acrylonitrile. Several lipases were evaluated, and good results were obtained leading to the formation of Michael adducts in shorter reaction times than the uncatalyzed reactions.     

Stereoselective synthesis of 1,3-dienylstannanes by palladium catalyzed cross-coupling reactions

(Z)-α-Bromovinylstannanes are new difunctional group reagents, which undergo palladium catalyzed cross-coupling reactions with (E)-alkenylzirconium complexes to give stereoselectively 1,3-dienylstannanes in good yields.     

双金属纳米材料催化的有机反应进展

纳米催化介于均相催化与多相催化之间, 也称为”半多相催化”, 目前正受到人们越来越多的关注. 最近几年, 应用双金属纳米材料进行催化研究取得了很大进展, 使用这些催化材料可以增加反应活性和选择性, 而且能很好地得以回收. 本文综述了双金属纳米材料催化的各种有机反应, 如选择性氧化/氢化、偶联和其它反应(脱卤、酰胺化、还原氨化、芳基硼酸与烯酮的1,4-不对称加成和氢解). 将双金属纳米材料用于催化合成更加复杂的有机分子值得期待. 在双金属纳米有机催化领域, 基础理论和实际应用尚有较大的发展空间. 未来该领域的发展需要开展多学科的合作, 包括合理设计和可控制备相关的双金属纳米材料、深入理解催化机理及发展计算催化.     

Stereoselective synthesis of pseudoglycosides catalyzed by TeCl4 under mild conditions

Catalytic amounts of tellurium(IV) tetrachloride were used to promote the O-glycosylation of 3,4,6-tri-O-acetyl-d-glucal to give the corresponding 2,3-unsaturated-O-glycosides. With simple alcohols, the desired compounds were obtained in good yields and excellent anomeric selectivity in a short reaction time using only 2 mol % of the catalyst. The application of the method in the synthesis of a small set of glycopyranosides with rigid or flexible linkers gave the corresponding α anomers as products in good yields. Further applications of some of the synthesized compounds in allylation reaction of aldehydes gave the corresponding homoallylic alcohols in good yields.     

Fluorimetric microdeterminations in organic solvents by using mercurated fluorescein

Summary To identify and determine amounts above 10^–10 mole of such substances as thiols, dithiocarbamates and thioureas in organic solvents, the use of an alcoholic solution of tetramercurated fluorescein (TMF) with oxine or prominal has been suggested. The determination is based on the displacement of oxine or prominal from their complexes with TMF and recording the change in fluorescence. The fluorescence of TMF complexes relative to the prominal complex as reference has been established for aqueous and organic solvent media. Fluorimetric titration with TMF-oxine and TMF-prominal is illustrated by determination of butanethiol in chloroform and thiomalic acid in hexanol.

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Zusammenfassung Zum Nachweis und zur Bestimmung von Thiolen, Dithiocarbamaten, Thioharnstoffderivaten und ähnlichen Verbindungen in organischen Lösungsmitteln wird die Verwendung einer alkoholischen Lösung von tetramercuriertem Fluoreszein (TMF) mit Oxin bzw. mit Prominal vorgeschlagen. Die Bestimmung beruht auf der durch Dekomplexierung verursachten Fluoreszenzänderung. Die Fluoreszenz von TMF-Komplexen wurde mit der von Prominalkomplexen in Wasser und in organischen Lösungsmitteln verglichen. Als Beispiel für fluorimetrische Titrationen mit TMF—Oxin wurde die Bestimmung von Butanthiol in Chloroform, für die Titration mit TMF—Prominal die Bestimmung von Thioäpfelsäure in Hexanol beschrieben. Der Schnittpunkt zweier Geraden zeigt den Endpunkt an.

     

Oxidation of alcohols by chlorine dioxide in organic solvents

The kinetics of oxidation of a series of alcohols (propan-2-ol, 2-methylpropan-1-ol, butan-1-ol, butan-2-ol, 3-methylpentan-1-ol, heptan-4-ol, decan-2-ol, cyclohexanol, borneol) by chlorine dioxide in organic solvents was studied using spectrophotometry. The reaction is described by the second-order rate equation w = k[ROH][ClO₂]. The rate constants were measured in the range of 10–60 °C, and the activation parameters of the processes were calculated. The products were identified, and the yields were determined.     

Microdetermination of alkaloids in organic solvents by potentiometric titration

A small-intefacial voltaic cell (antimony scratch) is shown to be satisfactory for end-point detection in titrations of various alkaloids and other basic drugs and their salts in ethanol, chloroform or dibutyl ether media with picric acid in the same medium. Small (0.4–4 mg) amounts can be determined. This method has the advantages of being simple and rapid with sharp end-points. The recoveries were 96.52-100.8% for the determinations of 19 drugs and their salts. The relative error was ±5% for five pharmaceutical tablets and injections.     

Asphaltene aggregation in organic solvents

Asphaltenic solids formed in the Rangely field in the course of a carbon dioxide flood and heptane insolubles in the oil from the same field were used in this study. Four different solvents were used to dissolve the asphaltenes. Near-infrared (NIR) spectroscopy was used to determine the onset of asphaltene precipitation by heptane titration. When the onset values were plotted versus asphaltene concentrations, distinct break points (called critical aggregation concentrations (CAC) in this paper) were observed. CACs for the field asphaltenes dissolved in toluene, trichloroethylene, tetrahydrofuran, and pyridine occurred at concentrations of 3.0, 3.7, 5.0, and 8.2 g/l, respectively. CACs are observed at similar concentrations as critical micelle concentrations (CMC) for the asphaltenes in the solvents employed and can be interpreted to be the points at which rates of asphaltene aggregations change. CMC values of asphaltenes determined from surface tension measurements (in pyridine and TCE) were slightly higher than the CAC values measured by NIR onset measurements. The CAC for heptane-insoluble asphaltenes in toluene was 3.1 g/l. Thermal gravimetric analysis (TGA) and elemental compositions of the two asphaltenes showed that the H/C ratio of the heptane-insoluble asphaltenes was higher and molecular weight (measured by vapor pressure osmometry) was lower.     

Inorganic polarography in organic solvents

A review of inorganic polarography in organic solvents is presented.     

Coal solubilization by enhanced enzyme activity in organic solvents

Applied Biochemistry and Biotechnology - Both oxidative and reductive enzymes can be utilized to enhance coal solubilization in aqueous and organic media. Aerobic solubilization was carried out...     

Lipase catalysis in organic solvents

The conditions for esterification and transesterification catalyzed by porcine pancreatic lipase in organic media were studied. It was found that the enzyme reaction was dependent on the following factors: the pH at which the enzyme powder was prepared from its solution, the polarity of organic media, the reaction temperature, the water content in reaction system, and the substrate structures. Effects of the above factors on enzyme activity were discussed.