N-methylimidazolium-functionalized monolithic silica column for mixed-mode chromatography

The development of mixed-mode stationary phase to achieve multiple separation capabilities in one column is very important for high performance liquid chromatography. In this paper, a new specific stationary phase based on grafting N-methylimidazolium to a monolithic silica column was successfully prepared for performing capillary liquid chromatography. The characteristics of the column were evaluated by the separation of different types of compounds including inorganic anions, aromatic acids, nucleotides, polycyclic aromatic hydrocarbons, alkylbenzenes, and phenols. The mechanisms for the separation of these compounds were investigated and appeared to involve the mixed interactions including anion-exchange, hydrophilic, π-π, dipole-dipole, and hydrophobic interactions.     

N-Methylimidazolium modified magnetic particles as adsorbents for solid phase extraction of genomic deoxyribonucleic acid from genetically modified soybeans

N-Methylimidazolium modified magnetic particles (MIm-MPs) were prepared and applied in the solid phase extraction of genomic deoxyribonucleic acid (DNA) from genetically modified soybeans. The adsorption of MIm-MPs for DNA mainly resulted from the strong electrostatic interaction between the positively charged MPs and the negatively charged DNA. The elution of DNA from MPs–DNA conjugates using phosphate buffer resulted from the stronger electrostatic interaction of phosphate ions with MPs than DNA. In the extraction procedure, no harmful reagents (e.g. phenol, chloroform and isopropanol, etc.) used, high yield (10.4 μg DNA per 30 mg sample) and high quality (A₂₆₀/A₂₈₀ = 1.82) of DNA can be realized. The as-prepared DNA was used as template for duplex-polymerase chain reaction (PCR) and the PCR products were analyzed by a sieving capillary electrophoresis method. Quick and high quality extraction of DNA template, and fast and high resolution detection of duplex PCR products can be realized using the developed method. No toxic reagents are used throughout the method.     

Simple and efficient cleavage of the N-(1-phenylethyl) unit of carboxamides with methanesulfonic acid

Cleavage of the N-(1-phenylethyl) unit of carboxamides using less than 1 equiv of MsOH in refluxing toluene was found to be simple and very efficient leading to the desired amides in good to excellent yields, and also proved to be more effective compared with reductive methods using hydrogen sources, or acid hydrolysis reagents such as TFA and TsOH. The method selectively cleaved only the N-(1-phenylethyl) group of N-benzyl-N-(1-phenylethyl)amides.     

Synthesis and characterization of a new boronate affinity monolithic capillary for specific capture of cis-diol-containing compounds

Boronate affinity chromatography (BAC) is an important tool for specific capture and separation of cis-diol-containing compounds such as glycoproteins, RNA and carbohydrates. Only a few reports on monolithic column-based BAC have appeared. In this paper, boronate functionalized monolithic capillary column was synthesized by in situ free radical polymerization for the first time. The prepared column was first characterized in terms of morphology, pore properties, capacity and retention mechanisms. The column exhibited uniform open channel network and high capture capacity. Systematical investigation on the retention mechanism revealed that multiple intermolecular interactions occur between the analytes and the boronate affinity monolith, including boronate affinity, reversed-phase, cation-exchange and hydrogen bonding interactions, depending on the conditions used. In addition, the presence of Lewis base such as fluoride ion in the mobile phase was found to be favorable to the complexation between cis-diol-containing compounds with the boronic acid ligand under less basic conditions. On the basis of these fundamental investigations, the prepared monolithic column was then applied to the capture of adenosine and flavin adenine dinucleotide. The investigations in this study provide sound understanding not only on how to manipulate the separation selectivity through selection of appropriate mobile phase composition on the currently prepared columns but also on how to design next-generation columns with desired properties and functions.     

A new anionic exchange stir bar sorptive extraction coating based on monolithic material for the extraction of inorganic anion

A novel anionic exchange stir bar sorptive extraction (SBSE) coating based on poly(2-(methacryloyloxy)ethyltrimethylammonium chloride-co-divinylbenzene) monolithic material for the extraction of inorganic anion was prepared. The effect of preparation conditions such as ratio of functional monomer to cross-linker, content of porogenic solvent on the extraction efficiencies were investigated in detailed. The monolithic material was characterized by elemental analysis, scanning electron microscopy and infrared spectroscopy. In order to investigate the extraction capacity of the new coating for inorganic anion, the new SBSE was combined with ionic chromatography with conductivity detection, Br⁻, NO₃⁻, PO₄³⁻ and SO₄²⁻ were selected as detected solutes. Several extractive parameters, including pH value and ionic strength in sample matrix, desorption solvent, extraction and desorption time were optimized. The results showed that strongly ionic strength did not favor the extraction of anlaytes. Under the optimum experimental conditions, low detection limits (S/N = 3) and quantification limits (S/N = 10) of the proposed method for the target anions were achieved within the range of 0.92–2.62 and 3.03–9.25 μg/L, respectively. The method also showed good linearity, simplicity, practicality and low cost for the extraction inorganic anions. Finally, the proposed method was successfully used to detect the two different trademarks of commercial purified water with satisfactory recovery in the range of 70.0–92.6%. To the best of our knowledge, this is the first to use SBSE to enrich inorganic anions.     

Synthesis and applications of surface-grafted Th(IV)-imprinted polymers for selective solid-phase extraction of thorium(IV)

A new functional monomer N-(o-carboxyphenyl)maleamic acid (CPMA) was synthesized and chosen for the preparation of surface-grafted ion-imprinted polymers (IIPs) specific for thorium(IV). Polymerizable double bond was introduced to silica gel surface by amidation reaction between -NH₂ and maleic anhydride. In the ion-imprinting process, thorium(IV) was complexed with the carboxyl groups, then was imprinted in the polymers grafted to the silica gel surface. The imprinted Th(IV) was removed with 3 mol L⁻¹ HCl. The obtained imprinted particles exhibited excellent selectivity and rapid kinetics process for Th(IV). The relatively selective factor (α_r) values of Th(IV)/La(III), Th(IV)/Ce(III), Th(IV)/Nd(III), Th(IV)/U(VI), and Th(IV)/Zr(IV) were 85.7, 88.9, 26.6, 64.4, and 433.8, respectively, which were greater than 1. The precision (R.S.D.), the detection limit (3σ), and the quantification limit (10σ) of the method were 1.9%, 0.51 ng mL⁻¹ and 1.19 ng mL⁻¹, respectively. The prepared IIPs as solid-phase extractants were successfully applied for the preconcentration of trace thorium in natural and certified samples prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES) with satisfactory results.     

A Keggin heteropoly acid as an efficient catalyst for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles

The Keggin heteropoly acid, silicotungstic acid, H₄SiW₁₂O₄₀, has been demonstrated to be highly efficient for an expeditious, one-pot synthesis of 1-methyl-2-(hetero)arylbenzimidazoles from N-methyl-1,2-phenylenediamine and (hetero)aryl aldehydes in ethyl acetate at room temperature. The catalyst works equally well for N-phenyl-1,2-phenylenediamine.     

General-buffer catalysis of the reaction of N-(hydroxymethyl)benzamide: a new pathway for the aqueous reaction of carbinolamides

The second-order rate constants for the general-buffer catalyzed breakdown of N-(hydroxymethyl)benzamide (1) in water at 25 °C, I = 1.0 (KCl) by pivalic, acetic, chloroacetic, and dichloroacetic acid were determined by initial rates. The observed rate increased with increasing amounts of the acidic form of the buffer and a Brønsted correlation of α = 0.35 was determined. The results presented here, represent the first evidence for a general-buffer catalytic mechanism for the aqueous reaction of 1 and for carbinolamides in general.     

N-(Trifluoromethylsulfonyl)trifluoromethanesulfinimidic acid and its salts

Lithium, sodium and potassium N-(trifluoromethylsulfonyl)trifluoromethanesulfinimidates were obtained by the reaction of the corresponding sulfinimidoyl chloride with alkali metal trimethylsilanolates. The potassium and sodium salts were converted to the free acid, having predominantly the amidic tautomeric structure, CF₃S(O)NHSO₂CF₃, by treatment with concentrated H₂SO₄ or with H⁺-cationite.     

Synthesis of new N-aryl oxindoles as intermediates for pharmacologically active compounds

Various new N-aryl oxindoles were synthesized as intermediates for the preparation of pharmacologically active 2-(N-arylamino)-phenylacetic acids. Two novel approaches were explored for the construction of diarylamine and N-aryl oxindole core structures, in addition to Buchwald-arylamination and Smiles rearrangement. Condensation of anilines with 2-oxo-cyclohexylidene-acetic acid derivatives and subsequent dehydrogenation is a new and viable method for the preparation of N-aryl oxindoles.     

An expedient route for the reduction of carboxylic acids to alcohols employing 1-propanephosphonic acid cyclic anhydride as acid activator

A simple and efficient method for the synthesis of alcohols from the corresponding carboxylic acids is described. Activation of carboxylic acid with 1-propanephosphonic acid cyclic anhydride (T3P) and subsequent reduction using NaBH₄ yield the alcohol in excellent yields with good purity. Reduction of several alkyl/aryl carboxylic acids and N^α-protected amino acids/peptide acids as well as N^β-protected amino acids was successfully carried out to obtain corresponding alcohols in good yields. All the products were fully characterized by ¹H NMR and mass spectral analyses. The procedure is mild, simple and the isolation of the products is easy.     

N-tert-Butyl-N-chlorocyanamide: a new reagent for the efficient preparation of gem-chloronitroso compounds

A new reagent for the efficient preparation of gem-chloronitroso compounds has been developed. The reaction of ketoximes with N-tert-butyl-N-chlorocyanamide takes place instantaneously in carbon tetrachloride at room temperature with excellent yields under mild conditions.     

N-Chlorophthalimide as a mild and efficient chlorination reagent in the Gassman ortho alkylation of aromatic amines. Synthesis of 3-(methylthio)oxindoles

A practical modification of the Gassman 3-(methylthio)oxindole synthesis is reported. In our method, substituted anilines and 2-(methylthio)acetamide were reacted under mild reaction conditions, in the presence of N-chlorophthalimide as a chlorinating agent to give α-amidosulfides, which, in the next step of the process, were cyclized to give 3-(methylthio)oxindoles. The method was successfully applied for the synthesis of the key intermediate, 2-(2-amino-3-benzoylphenyl)-2-(methylthio)acetamide, in the process of the preparation of nepafenac, a commonly used ophthalmic drug.     

N-(Diethoxyphosphoryl)-O-benzylhydroxylamine—a convenient substrate for the synthesis of N-substituted O-benzylhydroxylamines

Easily available N-(diethoxyphosphoryl)-O-benzylhydroxylamine was shown to be convenient, orthogonally protected substrate for regioselective N-alkylation by means of diverse halides under basic conditions (sodium hydride/tetrabutylammonium bromide). An efficient procedure for dephosphorylation of N-substituted N-(diethoxyphosphoryl)-O-benzylhydroxylamine to provide N-substituted O-benzylhydroxylamines was also established.     

Spectrofluorimetric determination of aliphatic amines using a new fluorigenic reagent: 2,6-dimethylquinoline-4-(N-succinimidyl)-formate

A new amino fluorescence probe, 2,6-dimethylquinoline-4-(N-succinimidyl) formate (DMQF-OSu) has been synthesized. Based on the selective reaction of DMQF-OSu with primary and secondary aliphatic amines to yield strong fluorescence, a new spectrofluorimetric method for the determination of total aliphatic amines has been developed. At λ_ex/λ_em=324.4/416 nm, the linear calibration range was 6×10⁻⁸-6×10⁻⁶ mol l⁻¹ with the detection limit (3σ) of 1.94×10⁻¹⁰ mol l⁻¹ for the determination of aliphatic amines in weak basic media. The proposed method has been applied to the determination of aliphatic amines in tap water and lake water with the recoveries of 99-104%. Compared with the reported methods, the method presented here is rapid, simple, sensitive and feasible.     

Silica-bonded S-sulfonic acid: an efficient and recyclable solid acid catalyst for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols)

Silica-bonded S-sulfonic acid (SBSSA) is employed as a recyclable catalyst for the condensation reaction of aromatic aldehydes with 3-methyl-l-phenyl-5-pyrazolone. This condensation reaction was performed in ethanol under refluxing conditions giving 4,4′-alkylmethylene-bis(3-methyl-5-pyrazolones) in 75-90% yields.     

Brønsted acid TfOH-mediated reactions of 2-(arylmethylene)cyclopropylcarbinols with acetonitrile

We report herein Brønsted acid TfOH-mediated reactions of 2-(arylmethylene)cyclopropylcarbinols with acetonitrile to give the corresponding ring-enlarged N-(3-arylmethylidenecyclobutyl)acetamides in moderate to good yields under mild conditions. A plausible mechanism is proposed on the basis of previous investigations.     

Synthesis of l-azaisotryptophan and its analogs: a general access to new 2-substituted azaindoles

l-(N-Cbz)-7-azaisotryptophan, l-(N-Cbz)-1a, a new isostere of tryptophan, was synthesized by reacting Li₂-(N-Boc)-2-amino-3-picoline, Li₂-(N-Boc)-2a, with appropriately protected l-aspartic acid followed by simple functional group manipulation. This synthetic success led us to access a set of analogs of azaisotryptophan (4a–c; 6a–c) as well as a new class of chiral amines (7a–c; 8a–c) for future application in asymmetric synthesis and design of homochiral ligands. Further, we have generalized the method substantiating a variety of new azaindol-2-yl derivatives (10aa–10lc) with functionalized substituents. In a preliminary luminescence characterization, l-(N-Cbz)-1a has exhibited about 30 nm bathochromic shifted fluorescence emission compared to tryptophan and (N-Cbz)-tryptophan.     

Ascorbate amperometric determination using conducting copolymers from aniline and N-(3-propane sulfonic acid)aniline

The sequential electrochemical polymerization of aniline and N-(3-propane sulfonic acid)aniline (PSA) is proposed to construct a sensor able to detect ascorbate at physiological conditions. Compared to poly(aniline) modified electrode, a device with improved conducting and electrochemical properties at neutral pH is obtained. The electrochemical copolymerization of the same starting materials is also carried out. For a PSA:aniline ratio of 10:90, a polymer with a similar electrochemical behavior to the one grown in the sequential mode is observed.The detection of ascorbate was tested for both configurations at pH 7.2, the modified electrode is able to determine ascorbate at 0 mV versus Ag/AgCl; an optimized sensor constructed by sequential polymerization can easily detect ascorbate concentrations with a detection limit of 2.2 μM. Uric acid and dopamine does not interfere in the ascorbate determination.