Use of pyridinium ionic liquids as catalysts for the synthesis of 3,5-bis(dodecyloxycarbonyl)-1,4-dihydropyridine derivative

The synthesis of cationic amphiphilic 1,4-dihydropyridine derivative, potential gene delivery agent is achieved via an efficient multi-step sequence. The key step of this approach is a two-component Hantzsch type cyclisation of 3-oxo-2-[1-phenylmethylidene]-butyric acid dodecyl ester and 3-amino-but-2-enoic acid dodecyl ester utilising bis(2-hydroxyethyl)ether as a solvent and 1-butyl-4-methylpyridinium chloride as a catalyst. The 1,4-dihydropyridine derivative with long alkyl ester chains at positions 3 and 5 of the 1,4-DHP ring — 3,5-bis(dodecyloxycarbonyl)-2,6-dimethyl-4-phenyl-1,4-dihydropyridine was obtained in substantially higher yield with respect to classical Hantzsch synthesis. Bromination of this compound followed by nucleophilic substitution of bromine with pyridine gave the desired cationic amphiphilic 1,4-dihydropyridine.      

The binary system PbO - BiVO4

Phase equilibria established in the PbO - BiVO₄ system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed using DTA and XRD.      

Spectral study of coumarin-3-carboxylic acid interaction with human and bovine serum albumins

Fluorescence spectroscopy and circular dichroism (CD) spectroscopy were used to investigate the interaction of coumarin-3-carboxylic acid with human serum albumin (HSA) and bovine serum albumin (BSA) under physiological conditions in a buffer solution of pH 7.4.      

2-(benzimidazol-2-yl)-3-hydroxychromone derivatives: spectroscopic properties and a possibile alternative intramolecular proton phototransfer

Three 2-(benzimidazol-2-yl)-3-hydroxychromone derivatives were synthesized. Their spectroscopic and fluorescent properties, due to excited state intramolecular proton transfer (ESIPT) from OH to carbonyl, were studied. Theoretical possibility of an alternative intramolecular H-bonding and experimental evidence for such behavior are discussed.      

Metathesis transformations of unsaturated derivatives of β-diketones

Selected β-diketones bearing unsaturated derivatives have been demonstrated to undergo homo-metathesis and cross-metathesis with selected olefins in the presence of Grubbs catalysts. The reactions led to respective homo- and cross-metathesis products mainly with good yields and selectivities.      

N- Hydroxyphthalimide and transition metal salts as catalysts of the liquid-phase oxidation of 1-methoxy-4-(1-methylethyl)benzene with oxygen

The oxidation process of 1-methoxy-4-(1-methylethyl)benzene catalysed by N-hydroxyphthalimide (NHPI) or NHPI in combination with Cu(II), Co(II), Mn(II) and Fe(II) salts was studied. The effects of the amount of catalyst and the temperature were determined. 1-Methyl-1-(4-methoxyphenyl)ethyl hydroperoxide was obtained in a yield of 73 mol% when 1-methoxy-4-(1-methylethyl)benzene was oxidised for 3 h at 60°C in acetonitrile as a solvent in the presence of NHPI. 1-(4-Methoxyphenyl)ethanone with high selectivity up to 68–75 mol%, but low yield amounting to 11 mol% was obtained when 1-methoxy-4-(1-methylethyl)benzene was oxidised in the presence of the NHPI/Cu(II) system at 120°C.      

Recent development in capillary ion chromatography technology

This review summarizes the development of capillary ion chromatography (CIC) over approximately the last 5 years. It mainly focuses on the technologic aspects of several key components associated with CIC, including micropump, microscale electrodialytic eluent generator, microscale suppressor and the detector.      

An analysis of SCF and geometry convergence for diatomic molecules

A geometry and SCF convergence study of Hartree-Fock calculations using the 6-31G* basis set is carried out on the set of all possible diatomic molecules formed from atoms with Z≤36. The utility of Hartree-Fock calculations using the smaller STO-3G basis set to improve the convergence behavior is demonstrated.      

One-pot, three-component condensation of 2-hydroxybenzaldehyde derivatives, primary amines with alkyl isocyanides to N-alkyl-2-(2-hydroxyphenyl)-2-imino-acetamides

One-pot, three-component condensation of 2-hydroxybenzaldehyde derivatives, primary amines with alkyl isocyanides is reported. N-alkyl-2-(2-hydroxyphenyl)-2-iminoacetamide derivatives are generated presumably via the preliminary formation of N, N′-disubstituted benzo[b]furan-2,3-diamines and subsequent oxidation with molecular oxygen.      

Facile dehalogenation of halogenated anilines and their derivatives using Al-Ni alloy in alkaline aqueous solution

This article describes the simple hydrodehalogenation of halogenated anilines and their derivatives by the action of Raney aluminium-nickel alloy in aqueous alkaline solution at room temperature. The reaction course was monitored by means of 1H nuclear magnetic resonance (NMR) spectroscopy and GC-MS spectra.      

<Emphasis Type="Italic">N</Emphasis>-Alkylation of benzimidazoles with ketonic Mannich bases and the reduction of the resulting 1-(3-oxopropyl)benzimidazoles

Benzimidazole, benzimidazoles diversely substituted at position 2, and 5,6-dimethylbenzimidazole have been alkylated at N ¹ with ketonic Mannich bases derived from acetophenones, acetylnaphthalenes, 2-acetylthiophene and 1-tetralone to afford a series of novel 1-(3-oxopropyl)benzimidazoles. The reduction of these transamination products with NaBH₄ in methanol produced the corresponding 1-(3-hydroxypropyl)benzimidazoles in excellent yields.      

ZrOCl<Subscript>2</Subscript> · 8H<Subscript>2</Subscript>O: An efficient catalyst for rapid one-pot synthesis of 3-carboxycoumarins under ultrasound irradiation in water

In this report, a rapid, efficient and environmental friendly synthesis of 3-carboxycoumarins under ultrasound irradiation in water media is described. The Knoevenagel condensation of Meldrum’s acid with substituted benzaldehydes in the presence of zirconium oxide chloride (ZrOCl₂·8H₂O) and ultrasonic irradiation in water gave the corresponding 3-carboxycoumarins in good to excellent yields.      

Ionic liquids - deanol derivatives as the Diels-Alder reaction solvents

The Diels-Alder reaction between cyclopentadiene and dienophiles in deanol derivatives containing bis(trifluoromethylsulfonyl)imide anion as media have been studied. The effect of the substituents attached to the cation on the endo:exo selectivity as well as the reaction yield have been evaluated in the absence and presence of Lewis acid catalyst - Y(OTf)₃. Catalytic activity of metal triflates and the recycling of chosen catalytic systems have also been investigated      

Synthesis of 1-aryl-1-phenylpropenes using an alkylation-rearrangement-methylation-isomerization one-pot reaction sequence

(Z/E)-1-(2-Methoxyaryl)-1-phenylpropenes have been prepared in good yields by heating a mixture of a phenolic substrate, cinnamyl chloride, tetramethylammonium chloride and K₂CO3 in polyethyleneglycol at 180°C. The one-pot synthesis proceeds through four discrete reaction steps: alkylation of the phenol with cinnamyl chloride, Claisen rearrangement, O-methylation and double-bond migration. The configuration of one crystalline product was determined using a single-crystal X-ray diffraction analysis. The thermodynamic and structural features of the products were evaluated using computational chemistry techniques.      

Use of multivariate statistical techniques to optimize the separation of isoflavones by liquid chromatography

The aim of this paper is to optimize and validate a high performance liquid chromatography (HPLC) method for separation and quantification of five isoflavones. A statistical central composite design was used to separate all peaks. These multivariate procedures were efficient in determining the optimal separation condition using resolution, capacity factor, asymmetry and number of theoretical plates.      

Synthesis of fluorescent long-chain thiols/disulfides as building-blocks for self-assembled monolayers preparation

New symmetrical disulfides together with the corresponding thiols bearing fluorescent end-groups have been synthesized as building-blocks for self-assembled monolayers (SAMs). The synthesis has been accomplished starting from aromatic nitrogen heterocycles in three steps. The conversion of the tosylated intermediate into the final disulfide is accomplished by use of sodium hydrogen sulfide (NaSH). Both products (thiols and disulfides) were isolated and characterized.      

Voltammetric determination of some alkaloids and other compounds in pharmaceuticals and urine using an electrochemically activated glassy carbon electrode

Electrochemical behaviour of some alkaloids, namely: caffeine, aminophylline, theophylline, codeine phosphate and papaverine hydrochloride, that are in solution in various combinations or in the presence of other compounds contained in pharmaceuticals or in real samples (urine) was investigated using cyclic voltammetry (CV), square-wave voltammetry (SWV) and differential pulse voltammetry (DPV) on electrochemically activated glassy carbon electrode.      

Equilibrium and kinetic study of the proton transfer reactions between nitroalkanes and strong organic bases — phosphazenes in tetrahydrofuran solvent

Proton transfer reactions rates between carbon acids 1-nitro-1-(4-nitrophenyl)ethane (NPNE), 2-methyl-1-nitro-1-(4-nitrophenyl)propane (MNPNP)) and phosphazenes (BEMP, BTPP, P₁-t-Oct) in tetrahydrofuran have been measured, and the activation parameters were determined. The results are compared with those previously obtained for P₁-t-Bu phosphazene, guanidines and amidines.