A simple, efficient, and selective deuteration via a flow chemistry approach

A simple and efficient deuteration methodology has been established for a wide variety of substrates using a continuous flow hydrogenation reactor. The described procedure is many times faster (1 mg min⁻¹) compared to literature methods and the purity of the crude product can be as high as 99%. The deuterium source is D₂O, the consumption of which is very low.     

Regioselective removal of the anomeric O-benzyl from differentially protected carbohydrates

A mild, regioselective deprotection of the anomeric O-benzyl from multi-functionally protected carbohydrates via catalytic transfer hydrogenation is described. The protocol is tolerant of O-benzyl and O-benzylidene protections at non-anomeric positions, groups which are normally labile under typical hydrogenolysis conditions.     

Hydroxyl group deprotection reactions with Pd(OH)2/C: a convenient alternative to hydrogenolysis of benzyl ethers and acid hydrolysis of ketals

Benzyl ethers, ketals and orthoformates were cleaved with Pd(OH)₂/C in methanol, to generate the corresponding alcohol; carboxylic acid esters were stable under these reaction conditions. Pd(OH)₂/C in methanol was used for the deprotection of hydroxyl groups during the preparation of sequoyitol via myo-inositol orthobenzoate. This method of deprotection has the potential to be useful in the synthesis of different classes of organic compounds since the reaction conditions do not involve strong acids, bases or hydrogen.     

Rapid and efficient protection of alcohols and phenols,and deprotection of trimethylsilyl ethers catalyzed by a cerium‐containing polyoxometalate

Herein, we want to report a simple and convenient way for protection‐deprotection of alcohols in the presence of ammonium decatungstocerate(IV) {(NH₄)₈[CeW₁₀O₃₆]·20H₂O} as catalyst under ambient temperature in CH₃CN. Using 0.002 mmol of the catalyst, various alcohols and phenols were transformed easily to the corresponding TMS ethers in excellent yields. In the second part, various TMS ethers were successfully converted to the parent hydroxyl compounds in the presence of the ammonium decatungstocerate(IV) catalyst. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparison of metallic electrodes for constant-potential amperometric detection of carbohydrates,amino acids and related compounds in flow systems

Constant-potential amperometric detection of carbohydrates, amino acids, and other aliphatic organic compounds is possible by means of their oxidation in alkaline solution at a variety of metal/metal oxide electrodes including Pt, Au, Cu, Ni, Ag and Co. The experimental conditions required for optimum detection and the analytical performance obtainable vary widely for different electrode materials and analytes. In this work, the cyclic voltammetric behavior exhibited by selected analytes (glucose, glycine, lactic acid, ethylamine and ethanol) at each of these electrodes was used to determine the optimum potentials suitable for flow detection so that the capabilities of the different metal electrodes could be evaluated and systematically compared. In general, the Cu electrode was found to provide superior detection capabilities in terms of its range of response, detection limits and especially stability. Despite the fact that Pt and Au are typically used only with a pulsed applied potential, both can provide long-lived constant-potential detection of carbohydrates and other analytes at low concentrations if the potentials ere carefully chosen and the electrodes are allowed to undergo an initial stabilization period.     

A combination of flow and batch mode processes for the efficient preparation of mGlu2/3 receptor negative allosteric modulators (NAMs)

Benzodiazepinones are privileged scaffolds with activity against multiple therapeutically relevant biological targets. In support of our ongoing studies around allosteric modulators of metabotropic glutamate receptors (mGlus) we required the multigram synthesis of a β-ketoester key intermediate. We report the continuous flow synthesis of tert-butyl 3-(2-cyanopyridin-4-yl)-3-oxopropanoate and its transformation to potent mGlu_2/3 negative allosteric modulators (NAMs) in batch mode.     

A simple, efficient and versatile synthesis of primary gem-dihydroperoxides from aldehydes and hydrogen peroxide

Aldehydes were efficiently converted directly into the corresponding gem-dihydroperoxides (DHPs) on treatment with aqueous 70% H₂O₂ in a biphasic system with ether catalyzed by camphorsulfonic acid. The synthesis represents the most versatile access to this class of compounds.     

Combining engineering and chemistry for the selective continuous production of four different oxygenated compounds by photo-oxidation of cyclopentadiene using liquid and supercritical CO2 as solvents

A range of products is reported from the photo-oxidation of cyclopentadiene from photochemically generated singlet oxygen (¹O₂) using carbon dioxide (CO₂) as a solvent and 5,10,15,20-tetrakis-(pentafluorophenyl)porphyrin (TPFPP) as a CO₂-soluble photosensitizer. The endo-peroxide intermediate, generated from the reaction with singlet oxygen, is transformed into one of several different products in good yield depending on the conditions applied and by adding different reactors and reagents downstream of the photo-reactor, allowing the reaction products to be switched in one streamlined process. The addition of a thermal reactor facilitated the rearrangement of the endoperoxide to form Z-4,5-epoxy-2-pentanal. Quenching with thiourea yielded the syn-diol, (1R,3S)-cyclopent-4-ene-1,3-diol. Treatment with acid or base afforded furfuryl alcohol and 4-hydroxy-2-cyclopentenone respectively. High productivities for all products were obtained when compared to traditional batch reactions.     

A simple, efficient and highly selective deprotection of t-butyldimethylsilyl (TBDMS) ethers using silica supported sodium hydrogen sulfate as a heterogeneous catalyst

t-Butyldimethylsilyl (TBDMS) ethers have been efficiently and selectively deprotected using silica supported sodium hydrogen sulfate (NaHSO₄·SiO₂) as a heterogeneous catalyst at room temperature to regenerate the parent alcohols in high yields.     

A simple TiCl4 promoted arylation of orthoformate and benzyl ethers by N,N-dialkylarylamines

N,N-Dialkylarylamines react with trimethyl orthoformate and TiCl₄ under ambient conditions to give the corresponding formyl derivatives in 75-89% yields, whereas the corresponding arylated products are obtained from benzyl ethers and acetals in 42-78% yields.     

A simple and efficient synthesis of 2-substituted benzothiazoles catalyzed by H_2O_2/HCl

A simple and efficient procedure for the synthesis of substituted benzothiazoles through condensation of 2-aminothiophenol with aromatic aldehydes in the presence of H_2O_2/HCl system in ethanol at room temperature is described.The target compounds have been characterized by ~1H NMR,~(13)C NMR,IR and MS.Short reaction time,easy and quick isolation of the products,and excellent yields are the main advantages of this procedure.     

Rapid, highly efficient and stereoselective deoxygenation of epoxides by ZrCl4/NaI

An effective and highly chemoselective method is described for the rapid deoxygenation of different epoxides to the corresponding olefins using ZrCl₄/NaI in anhydrous CH₃CN, in excellent yields and with retention of relative stereochemistry.     

Synthesis of PCL–graft–PS by combination of ROP, ATRP, and click chemistry

Poly(ε-caprolactone)–graft–polystyrenes were successfully synthesized by grafting an azide end-functionalized polystyrene onto a PCL backbone with multiple pendant alkyne moieties using a “click” chemistry reaction. Both precursors, the PCL backbone and the PS side chains, were prepared separately by two different living/controlled mechanisms, ring-opening polymerisation and ATRP, respectively. Molecular weights, polydispersity indexes, and chemical compositions of the backbone and branches were controlled. The subsequent copper-catalysed Huisgen 1,3-dipolar cycloaddition of PS onto PCL was achieved at room temperature with high conversion. However, a bimodal molecular weight distribution was observed in size exclusion chromatography due to the presence of unreacted PS. Nevertheless, crude product was purified by selective fractionation in cyclohexane to achieve pure graft copolymers.     

Catalysis by ionic liquid: a simple, green and efficient procedure for the Michael addition of thiols and thiophosphate to conjugated alkenes in ionic liquid, [pmIm]Br

A room temperature ionic liquid, 1-pentyl-3-methylimidazolium bromide, [pmIm]Br efficiently catalyzes Michael addition of thiols and diethyl dithiophosphate to a variety of conjugated alkenes such as α,β-unsaturated carbonyl compounds, carboxylic esters, nitriles and chalcones without requiring any other organic solvent and catalyst. The ionic liquid can be recycled for subsequent reactions without any appreciable loss of efficiency.     

A simple and efficient synthesis of 2-substituted benzothiazoles catalyzed by H_2O_2/HC1

A simple and efficient procedure for the synthesis of substituted benzothiazoles through condensation of 2-aminothiophenol with aromatic aldehydes in the presence of H₂O₂/HCl system in ethanol at room temperature is described. The target compounds have been characterized by ¹H NMR, ¹³C NMR, IR and MS. Short reaction time, easy and quick isolation of the products, and excellent yields are the main advantages of this procedure.     

A facile and efficient strategy for one-step in situ preparation of hydrophobic organic monolithic stationary phases by click chemistry and its application on protein separation

A simple one-step in situ “click” modification strategy was developed for the preparation of hydrophobic organic monolithic columns for the first time. The column morphology and surface chemistry of the fabricated monolithic columns were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, respectively. The chromatographic performances of the C8/C18 “click” monoliths were evaluated through the separation of a mixture of five proteins such as ribonuclease A, soybean trypsin inhibitor, cytochrome c, bovine haemoglobin and bovine serum albumin. Compared with the blank column, the higher hydrophobicity stationary phases obtained from the “clicked” modification have longer retention times and higher resolution for the five proteins. The separation of five proteins mixture on click C18 monolith with gradient elution at different flow rates was also investigated, the baseline separation of five proteins could be achieved at three different flow rates.     

Determination of carbohydrates in juices by capillary electrophoresis, high-performance liquid chromatography, and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry

The objective of this work was to develop a sample preparation procedure for determination of the carbohydrate profiles in commercial juice samples by three principally different analytical methods: capillary electrophoresis (CE) with indirect detection, high-performance liquid chromatography (HPLC), and matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS). The preparation and purification of juice samples prior to analysis is described. The method using Carrez reagents was found to be an efficient preparation tool for all three methods. The addition of Carrez reagents to the samples for mass analysis improved the quality of the mass spectra of oligosaccharides. The amounts of glucose, fructose, and sucrose as major carbohydrates in fruit juices measured by CE using a simple instrument are in good agreement with the HPLC values and the data declared by the producers of the juices. The results from both methods are critically evaluated and their impact for studies of authenticity is discussed. The decrease of sucrose amount during the storage of samples was explained by acid hydrolysis of this disaccharide.     

Synthesis,characterization and application of alumina/ vanadium pentoxide nanocomposit by sol–gel method

In this work, we report the preparation of Al₂O₃/V₂O₅ nanocomposit using vanadium and aluminum nitrate by sol–gel method. Characterization of nanocomposit was carried out by powder X‐ray diffractometry (XRD), Fourier transform infrared (FT‐IR), scanning electron microscopy (SEM), Energy‐Dispersive X‐ray (EDX) and UV spectroscopy. Then, applicability of the synthesized nanocomposit was tested as a nanocatalyst for the synthesis of diindolyl oxindole derivatives, an important class of potentially bioactive compounds. The products were obtained in good to high yields from one‐pot three‐component condensation of isatin with indole. Also, this nanocatalyst has been reused several times, without observable loss of activity.