Recent developments in non-enzymatic catalytic oxidative kinetic resolution of secondary alcohols

The goal of this review is to collect the recent developments in non-enzymatic catalytic oxidative kinetic resolutions of secondary alcohols reported since the beginning of 2011. It is divided into four sections, dealing successively with manganese-catalysed oxidative kinetic resolutions of secondary alcohols, palladium-catalysed oxidative kinetic resolutions of secondary alcohols, oxidative kinetic resolutions of secondary alcohols catalysed by other metals and organocatalysed oxidative kinetic resolutions of secondary alcohols.     

N-溴代丁二酰亚胺水相氧化醇类化合物反应研究

以水为反应介质、NBS为氧化剂,在水相无催化剂条件下实现了醇的氧化.芳香醇、脂肪醇都可以达到95%以上的醛(或酮)产率,但该体系对一些含供电子取代基的醇的反应活性不高,选用salen-Co(Ⅲ)配合物作为催化剂,可拓宽反应的底物适用范围.     

Glucosidation shifts of allylic and benzylic alcohols in 13C NMR spectroscopy

The ¹³C FT NMR spectra of β-D -glucopyranosides (including their tetraacetates) of several secondary allylic and benzylic alcohols were compared with those of methyl β-D -glucopyranoside and the corresponding parent alcohols. The characeristic glucosidation shifts observed for these alcohols may be applicable to the determination of the absolute configuration of the hydroxy group in these alcohols.     

Separation of amino alcohols using divalent dipeptides as counter ions in aqueous CE

Divalent dipeptides have been introduced as counter ions in aqueous CZE. The dipeptides form ion pairs with amino alcohols in the BGE and facilitate the separation of amino alcohols. High concentrations of dipeptide caused reversed effective mobility for the analytes. The net charge of the dipeptide can be controlled using a buffer or a strong base, and regulates the interaction between the dipeptide and the amino alcohol. A stronger interaction and higher selectivity of amino alcohols was observed when the dipeptides were used as divalent counter ions, than in monovalent or uncharged form. Association constants for ion pairs between divalent dipeptides and amino alcohols can be used to enhance selectivity for amino alcohols in CZE. No chiral separation of amino alcohols was observed when using the dipeptides as ion‐pairing chiral selectors in aqueous BGE, but addition of methanol to the BGE promoted enantioselectivity.     

CO加氢合成低碳混合醇催化体系研究新进展

CO加氢合成低碳混合醇是C1化学研究的重要内容之一,近年来低碳混合醇在燃料和化工领域的应用价值逐步凸现,相关研究也受到越来越普遍的关注.本文就CO加氢合成低碳混合醇的催化剂体系、反应机理、合成工艺及应用等方面的最新进展进行了综述.     

Recent advances in catalytic production of sugar alcohols and their applications

Conversion of non-edible biomass into fuels and value-added chemicals has achieved great attention to cope the world's energy requirements. Lignocellulose based sugar alcohols such as sorbitol, mannitol, xylitol, and erythritol can be potentially used as emerging fuels and chemicals. These sugar alcohols can be converted into widely used products(e.g. polymer synthesis, food and pharmaceuticals industry). The heterogeneous catalytic production of sugar alcohols from renewable biomass provides a safe and sustainable approach. Hydrolysis, coupled with hydrogenation and hydrogenolysis has been proved to be more effective strategy for sugar alcohols production from biomass. This review summarizes the recent advances in biomass upgrading reactions for the production of sugar alcohols and their comprehensive applications.     

Polymorphic transitions in n-hydrocarbon-water and n-alcohol-water binary systems

The mixing of hydrocarbons and alcohols in an excess of water is explained by polymorphic transitions similar to crystallization in an ensemble of water clusters. Enthalpies of transitions of 4.90 ± 0.07 and 2.2 ± 0.3 kJ/mol are obtained for solutions of hydrocarbons and alcohols in an excess of water, respectively. It is concluded that the mixing of water in an excess of hydrocarbons and alcohols is similar to evaporation (the breaking of H-bonds) with an enthalpy of 34 ± 1.4 kJ/mol. It is established that a polymorphic transition occurs between two binodals, and is accompanied by the emergence of microphases (concentration fluctuations) of alcohols in water. Binodals and spinodals in an excess of water and alcohol coincide for butyl and other higher alcohols.     

Enthalpy of cooperative hydrogen bonding in complexes of tertiary amines with aliphatic alcohols: Calorimetric study

The work is devoted to the investigation of thermodynamics of specific interaction of the tertiary aliphatic and aromatic amines with associated solvents as which aliphatic alcohols were taken. Solution enthalpies of aliphatic alcohols in amines (tri-n-propylamine, 2-methylpyridine, 3-methylpyridine, N-methylimidazole) as well as amines in alcohols were measured at infinite dilution. The enthalpies of specific interaction (H-bonding) in systems studied were determined based on experimental data. The enthalpies of specific interaction of amines in aliphatic alcohols significantly lower than the enthalpies of hydrogen bonding in complexes amine–alcohol of 1:1 composition determined in base media due to the reorganization of aliphatic alcohols as solvents. The determination of solvent reorganization contribution makes possible to define the hydrogen bonding enthalpies of amines with clusters of alcohols. Obtained enthalpies of hydrogen bonding in multi-particle complexes are sensitive to the influence of cooperative effect. It was shown, that hydrogen bond cooperativity factors in multi-particle complexes of alcohols with amines are approximately equal for all alcohols when pyridines and N-methylimidazole as solutes are used. At the same time, H-bonding cooperativity factors in complexes of trialkylamines with associative species of alcohols decrease with increasing of alkyl radical length in alcohol and amine molecules.This work shows that the thermodynamic functions of specific interaction of solutes with associated solvents cannot be described using the H-bond parameters for the complexes of 1:1 composition.     

Transition-Metal-Catalyzed Direct Substitution of Alcohols in Aqueous Media

The direct use of alcohols as the much greener and more sustainable alkylated reagents in substitution reactions is one of the emerging areas in green chemisty. However, owing to the poor leaving character of OH group, the direct substitution of alcohols is not an easy thing. Transition metal (TM) catalysis such as Pd-catalyzed allylic/benzyl substitution and Ir-catalyzed borrowing hydrogen provides efficient protocols for the direct substitution of alcohols, however, an organic solvent and servely anhydrous conditions are generally required. In recent decade, TM-catalyzed direct substitution of alcohols in aqueous media was developed as a much greener alternative. In this review, the recent develpoments of this area are summarized. The activation mechanism of alcohols in aqueous reactions are emphatically discussed.     

Use of oxo-metallic derivatives in isomerisation: Reactions of unsaturated alcohols

The isomerisation of α-acetylenic alcohols to ethylenic carbonyl derivatives and the isomerisation of α-ethylenic alcohols to the corresponding allyl alcohols may be effected in good yields in a single step using oxometallic derivatives. The vanadate esters are particularly efficient. Mechanistic explanations are given.     

Excess enthalpies of solution of some primary and secondary alcohols in sodium dodecylsulfate micellar solutions

The exces enthalpies of solution of some primary and secondary alcohols in aqueous sodium dodecylsulfate micellar solutions were measured and the results were explained by considering the distribution of alcohols between aqueous and micellar phases. The distribution constant and the enthalpy of transfer (and the standard free energy and entropy of transfer) were obtained. The thermodynamic parameters for the transfer of secondary alcohols from the aqueous to the sodium dodecylsulfate (NaDS) micellar phase differ slightly from those of the corresponding primary alcohols. For both series of alcohols the additivity rule holds for free energies of transfer whereas enthalpies and entropies display convex curves. The present data are compared to those for the transfer of the same solutes from the aqueous to the dodecyldimethylamine oxide (DDAO) and dodecyltrimethylammonium bromide (DTAB) micellar phases. The role of the hydrophilic interactions between the OH group and the micelles' head groups is formulated. The thermodynamics of the branched methyl group were determined. Furthermore, the thermodynamics of solvation of primary alcohols in water, in NaDS micelles, and in octane have been calculated using reference states based on the assumption that the empty space around alcohols in the initial and final states is the same. It is shown that the solvation of alcohols in NaDS micellar phase is enthalpy driven and that the thermodynamic properties of solvation vs. the length of the alcohol tail is the same for water and NaDS micelles whereas it is different for octane. A possible explanation for this difference is that the alkyl chain of alcohols folds in octane.     

Determination of sugar alcohols in confectioneries by high-performance liquid chromatography after nitrobenzoylation

A method was developed for the determination of sugar alcohols, meso-erythritol, xylitol, D-glucitol, D-mannitol, maltitol and parachinit by high-performance liquid chromatography (HPLC). The sugar alcohols were converted into strong ultraviolet (UV)-absorbing derivatives with p-nitrobenzoyl chloride. HPLC was performed on a phenyl column, using acetonitrile-water (67:33) as mobile phase and UV detection (260 nm). The calibration curves for all sugar alcohols tested were linear in the 10-250 microg/ml range. The average recoveries of the sugar alcohols from four sugarless confectioneries spiked at 5 and 10% levels of six sugar alcohol standards ranged from 73.2 to 109.0% with relative standard deviations ranging from 0.7 to 9.0%. The detection limit of the developed method was 0.1% for the above sugar alcohols contained in the samples.     

Excess enthalpies of solution of primary and secondary alcohols in dodecyldimethylamine oxide micellar solutions

The excess enthalpies of solution with respect to water of some primary and secondary alcohols in dodecyldimethylamine oxide (DDAO) micellar solutions were measured by mixing aqueous solutions of alcohols with surfactant solutions. Standard free energies, enthalpies and entropies were obtained from the distribution of alcohols between aqueous and micellar phases. It is shown that thermodynamics of transfer of secondary alcohols from aqueous to the DDAO micellar phase differ slightly from those of their corresponding primary alcohols, that the additivity rule holds for free energies of transfer and that enthalpy and entropy display convex curves. The present data are compared with those from the aqueous to the dodecyltrimethylammonium bromide (DTAB) micellar phases and to the literature data for transfer from water to octane. The role of the hydrophilic interactions between OH group and the micellar head groups and of the hydrophobic interactions between the methylene group and its apolar environment is evidenced.     

Lipase-mediated selective acetylation of primary alcohols in ethyl acetate

An environmental friendly process to selectively acetylate primary alcohols was demonstrated. The esterification process consists of treatment of a primary alcohol in the presence of immobilized C. antarctica lipase (Novozyme-435) in ethyl acetate at room temperature. Primary alcohols were acetylated in the presence of secondary alcohols and phenols.     

Recent advances in the homogeneous palladium-catalyzed aerobic oxidation of alcohols

The use of palladium catalysts for the oxidation of alcohols to aldehydes and ketones in the presence of various types of reoxidants is well known. Recently, the advantages of using molecular oxygen as the oxidant in the Pd-catalyzed oxidation of alcohols have been explored. The aim of this review is to provide an overview on the most important homogeneous palladium-catalyzed aerobic oxidation of alcohols without a co-catalyst during last decade until the end of 2007.     

Determination of low molecular weight alcohols including fusel oil in various samples by diethyl ether extraction and capillary gas chromatography

Low molecular weight alcohols including fusel oil were determined using diethyl ether extraction and capillary gas chromatography. Twelve kinds of alcohols were successfully resolved on the HP-FFAP (polyethylene glycol) capillary column. The diethyl ether extraction method was very useful for the analysis of alcohols in alcoholic beverages and biological samples with excellent cleanliness of the resulting chromatograms and high sensitivity compared to the direct injection method. Calibration graphs for all standard alcohols showed good linearity in the concentration range used, 0.001-2% (w/v) for all alcohols. Salting out effects were significant (p < 0.01) for the low molecular weight alcohols methanol, isopropanol, propanol, 2-butanol, n-butanol and ethanol, but not for the relatively high molecular weight alcohols amyl alcohol, isoamyl alcohol, and heptanol. The coefficients of variation of the relative molar responses were less than 5% for all of the alcohols. The limits of detection and quantitation were 1-5 and 10-60 microg/L for the diethyl ether extraction method, and 10-50 and 100-350 microg/L for the direct injection method, respectively. The retention times and relative retention times of standard alcohols were significantly shifted in the direct injection method when the injection volumes were changed, even with the same analysis conditions, but they were not influenced in the diethyl ether extraction method. The recoveries by the diethyl ether extraction method were greater than 95% for all samples and greater than 97% for biological samples.     

Interactions in water-alcohol mixtures studied by NMR and infrared spectroscopy

By using low temperatures and largely deuterated solvents, the rate of OH proton exchange for aqueous solutions of alcohols is reduced sufficiently to give separate NMR signals from water and alcohol OH protons. The limiting shifts for dilute alcohols in water are down-field of both the water resonance and those of the pure alcohols. This contrasts with the limiting shift for water in the alcohols, which is to high field of the bulk water resonance. The resonance shifts initially to low fields as [ROH] increases, the rate of shift being greatest for t-butyl alcohol. For dilute aqueous solutions, all the alcohols reduce the total concentration of free OH groups, as judged by the overtone infrared spectra. Some of these results are interpreted in terms of a scavenging of free OH groups by the excess lone-pairs of the alcohol molecules. An extra, temperature dependent, down-field shift in the water proton resonance induced by t-butyl alcohol is assigned to a clathrate cage effect.     

Distribution coefficients in the water-dodecane system and the heats of adsorption of C<Subscript>1</Subscript>-C<Subscript>8</Subscript> alcohols on silica

Distribution coefficients in the water-dodecane system and the heats of adsorption of C₁-C₈ alcohols on silica (Silochrom S-80) were determined by gas chromatography. At low temperatures, C₁-C₄ alcohols were largely distributed in the aqueous phase, and C₆-C₉ alcohols were predominantly dissolved in the organic phase; C₅ alcohols had intermediate properties. Permittivity was found to correlate with log K _d, which allowed us to predict the character of the distribution of alcohols in the water-oil system. The heats and isotherms of adsorption were determined for the alcohols studied. The heats of adsorption of alcohols on silica monotonically increased in the series under consideration. For C₅-C₈ alcohols, they exceeded the heat of adsorption of water. The isotherms of adsorption were described by the Freundlich equation.     

Barium dichromate [BaCr2O7], a mild reagent for oxidation of alcohols to their corresponding carbonyls in non-aqueous polar aprotic media

Barium dichromate is used as a mild oxidizing agent for the selective conversion of primary and secondary alcohols to their corresponding aldehydes and ketones, respectively. Over-oxidation does not occur and primary alcohols undergo oxidation to the aldehyde. Primary and secondary benzylic alcohols are oxidized faster and more efficiently.     

The aerobic oxidation of alcohols with a ruthenium porphyrin catalyst in organic and fluorinated solvents

Carbonylruthenium tetrakis(pentafluorophenyl)porphyrin Ru(TPFPP)(CO) was utilized for the aerobic oxidation of alcohols. The in situ activation of the catalyst with mCPBA provided a species capable of catalyzing the oxidation of alcohols with molecular oxygen. The choice of solvent and additive was crucial to obtaining high activity and selectivity. Secondary aromatic alcohols were oxidized in the presence of the ruthenium porphyrin and tetrabutyl ammonium hydroxide in the solvent bromotrichloromethane, enabling high yields to be achieved (up to 99%). Alternatively, alcohols could be oxidized in perfluoro(methyldecalin) with the ruthenium porphyrin at higher temperatures (140 degrees C) and elevated oxygen pressures (50 psi).