Solid–liquid two‐phase alkylation of tetraethyl methylenebisphosphonate under microwave irradiation

Optimum conditions for the solid–liquid phase alkylation of tetraethyl methylenebisphosphonate are dependent on the nature of the alkyl halide. The benzylation with benzyl bromide takes place efficiently in boiling acetonitrile in the presence of potassium carbonate and a phase transfer catalyst. The ethylation with ethyl iodide was best accomplished under solventless microwave conditions in the presence of cesium carbonate and in the absence of an onium salt. The analogous propylation and butylation were complicated by the formation of mixed esters. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:11–, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20648     

Synthesis of new pterocarpans and rapid O‐alkylation under microwave irradiation

Herein, it is described five new pterocarpans. Pterocarpans 8 and 9 were synthesized by classical [3 + 2] cycloaddition reaction of 2H‐chromene 7a and 7b with 2‐methoxy‐1,4‐benzoquinone. Pterocarpan 8 was O‐alkylated in the absence of solvents using a domestic microwave oven as a heat source and a classical O‐alkylation method with traditional heating. In this way three more new pterocarpans were obtained. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:239–244, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20175     

Novelties of cyanide displacement reaction in ibuprofen amide process by phase transfer catalysis: Solid–liquid versus solid–liquid (omega)–liquid systems

This work deals with the phase transfer catalysed cyanide displacement reaction on 1-(4-isobutyl phenyl) ethyl chloride to synthesize 2-(4-isobutyl phenyl) propionitrile, which is an intermediate for the synthesis of ibuprofen analogs, belonging to a class of NSAID (nonsteroidal anti-inflammatory drugs). The reaction was studied using solid–liquid phase transfer catalysis (S-L PTC) with trace quantities of water, forming the so-called omega phase at 90 °C. The rates of reaction and selectivity to the product are enhanced in the S-L(org.)-L (ω) PTC in comparison with S-L PTC, which in turn is superior to L-L PTC; the latter suffers from the disadvantage of side reactions in the aqueous phase. In the current work, the effects of various parameters such as catalyst structure, catalyst loading, substrate loading and temperature were studied on the conversion and rates of reaction of 1-(4-isobutyl phenyl) ethyl chloride with solid sodium cyanide under S-L and S-L(ω)-L PTC at 90 °C with toluene as the organic solvent. Tetrabutylammonium bromide (TBAB) was found to be the best catalyst. The role of omega liquid phase in intensification of the S-L PTC was theoretically and experimentally investigated. The kinetic constants have been determined and the apparent activation energy is found as 4.2 kcal/mol, which suggests that the reaction is quite fast, which is likely to bring in mass transfer effects.     

Synthesis of diethers derived from furoin by phase transfer catalysis under microwave irradiation

A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (>75%) within a few minutes, and the products of dihalides were synthesized in fair yields (about 45%). The yields are dramatically improved compared to conventional heating under the same conditions, in spite of similar profiles of rising in temperature.     

Synthesis and alkylation of pyridylacetylenes under phase transfer catalysis conditions in a liquid/solid system

We have investigated the alkylation of 2-methyl-5-ethynylpyridine by butyl bromide in liquid/liquid and liquid/solid two-phase catalytic systems. We have shown that the catalytic system solid KOH/18-crown-6/CuBr/toluene is the most active in this reaction; using this system, we obtained alkylation products of ethynylpyridines in 34–43% yields.Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsikicheskikh Soedinenii. No. 4, pp. 518–521, April, 1998.     

Liquid–liquid phase transfer of magnetite nanoparticles

The study presents first experimental results of the transfer of magnetite nanoparticles from an aqueous to a second non-miscible non-aqueous liquid phase. The transfer is based on the adsorption of macromolecular surfactants onto the particle surface at the liquid–liquid interface. For a successful direct phase transfer, it is essential to have cations, like ammonium ions, present in the aqueous phase as well as a threshold concentration of surfactant in the organic liquid phase. While penetrating the liquid–liquid interface, the particles are covered with the surfactant and therefore a partial de-agglomeration is initiated. Based on literature and experimental data a mechanism of surfactant adsorption is proposed. The competing adsorption of the surfactant molecules at the liquid–liquid interface leads to the formation of emulsions and therefore to a hindrance for particles passing the interface. Nevertheless a high efficiency of 100% yield can be reached using optimized process parameters for the phase transfer process.     

Reaction of benzyl chloride with ammonium sulfide under liquid–liquid phase transfer catalysis: Reaction mechanism and kinetics

The reaction between benzyl chloride and aqueous ammonium sulfide was carried out in an organic solvent – toluene, using tetrabutylammonium bromide (TBAB) as phase transfer catalyst (PTC). Two products, namely dibenzyl sulfide (DBS) and benzyl mercaptan (BM), were identified in the reaction mixture. The selectivity of DBS was maximised by changing various parameters such as NH₃/H₂S mole ratio, stirring speed, catalyst loading, concentration of benzyl chloride, volume of aqueous phase, and temperature. The highest selectivity of DBS obtained was about 90% after 445 min of reaction with excess benzyl chloride at 60 °C. Complete conversion of benzyl chloride could be achieved at the cost of very low selectivity of DBS and very high selectivity of BM. The apparent activation energy for the kinetically controlled reaction was found to be 12.3 kcal/mol. From the detailed study of the effects of various parameters on the reaction, a suitable mechanism was established which could explain the course of the reaction.     

Reversible addition–fragmentation chain transfer polymerization of styrene under microwave irradiation

Reversible addition–fragmentation chain transfer (RAFT) polymerizations of styrene under microwave irradiation (MI), with or without azobisisobutyronitrile, were successfully carried out in bulk at 72 and 98 °C, respectively. The results showed that the polymerizations had living/controlled features, and there was a significant enhancement of the polymerization rates under MI in comparison with conventional heating (CH) under the same conditions. The polymer structures were characterized with ¹H and ¹³C NMR. The results showed the same structure for both polymers obtained by MI and CH. Successful chain‐extension experimentation further demonstrated the livingness of the RAFT polymerization carried out under MI. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6810‐6816, 2006     

Synthesis of O-benzyl oximes by combination of phase transfer catalysis and ultrasound irradiation

The reactions of oximes with benzyl bromide catalyzed by benzyldimethyltetradecylammonium chloride are carried out at room temperature for 30–60 min in aqueous sodium hydroxide solution under ultrasound irradiation to offer O-benzyl oxime derivatives in 60–96% yields. In comparison to classical methods, the advantages of the present procedure include short reaction time, high yields and environmental friendliness. __________ Translated from Chinese Journal of Organic Chemistry, 2008, 28(4) (in Chinese)     

Solid–liquid phase equilibrium in the systems of LiBr–H2O and LiCl–H2O

A set of empirical temperature-molar fraction expressions for solid–liquid equilibrium curves of LiBr–H₂O and LiCl–H₂O systems is presented. The expressions are based upon a body of experimental data that have been compiled and critically evaluated. The equations cover the full composition range for LiCl–H₂O system and compositions up to the salt mole fraction of x = 0.46 (i.e. mass fraction of w=0.805) for LiBr–H₂O, corresponding to transition from monohydrate to anhydrate. Temperatures and solution compositions at the eutectic point and at transition points between hydrates have been determined from intersections of the curves corresponding to the adjacent hydrate ranges of the phase diagram. Equations of a special structure were used, involving the coordinates of the transition points as parameters, which makes possible their direct non-linear optimization. To obtain more reliable results, a procedure was employed optimizing both the temperature–composition and composition–temperature equations simultaneously. The uncertainty in the obtained values of the transition point coordinates are estimated to be of the order of 1 K for temperature and 0.001 for the composition expressed in salt mole fraction. Gaps in the database are shown to give experimenters orientation for future research.     

Solid‐phase extraction using chloropropyl functionalized sol–gel hybrid sorbent for simultaneous determination of organophosphorus pesticides in selected fruit samples

A new sol–gel hybrid methyltrimethoxysilane‐chloropropyltriethoxysilane was prepared as sorbent for solid‐phase extraction. The extraction efficiency of the prepared sol–gel hybrid methyltrimethoxysilane‐chloropropyltriethoxysilane was assessed by using three selected organophosphorus pesticides, namely, chlorpyrifos, profenofos, and malathion. Gas chromatography–mass spectrometry was used for detection of organophosphorus pesticides. Several vital parameters were optimized to identify the best extraction conditions. Under the optimum extraction conditions, solid‐phase extraction‐methyltrimethoxysilane‐chloropropyltriethoxysilane method showed good linearity range (0.05‐1 μg/mL) with coefficient of determination more than 0.995. The limits of detection obtained were in the range of 0.01–0.07 μg/mL and limits of quantification ranging from 0.03 to 0.21 μg/mL. The limits of detection obtained for the developed method were 2.3–6.5× lower than the limits of detection of commercial octadecyl silica sorbent. Real samples analysis was carried out by applying the developed method on red apple and purple grape samples. The developed method exhibited good recoveries (88.33–120.7%) with low relative standard deviations ranging from 1.6 to 3.3% compared to commercial octadecyl silica sorbent, which showed acceptable recoveries (70.3–100.2%) and relative standard deviations (6.3–8.8%). The solid‐phase extraction‐methyltrimethoxysilane‐chloropropyltriethoxysilane method is presented as an alternative extraction method for determination of organophosphorus pesticides.     

Solid‐phase extraction and analysis of paroxetine in human plasma by ultra performance liquid chromatography–electrospray ionization mass spectrometry

A rapid, sensitive and rugged solid‐phase extraction ultra performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method was developed for determination of paroxetine in human plasma. The procedure for sample preparation includes simple SPE extraction procedure coupled with Hypersil Gold C₁₈ column (100 mm ? 2.1 mm, i.d., 1.9 μm) with isocratic elution at a flow‐rate of 0.350 mL/min and fluoxetine was used as the internal standard. The analysis was performed on a triple‐quadrupole tandem mass spectrometer by multiple reactions monitoring mode via electrospray ionization. Using 500 μL plasma, the methods were validated over the concentration range 0.050–16.710 ng/mL for paroxetine, with a lower limit of quantification of 0.050 ng/mL. The intra‐ and inter‐day precision and accuracy of the quality control samples were within 10.0%. The recovery was 69.2 and 74.4% for paroxetine and fluoxetine respectively. Total run time was only 1.9 min. The method was highly reproducible and gave peaks with excellent chromatography properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Functional mesoporous poly (ionic liquid) derived from P123: From synthesis to catalysis and alkylation of styrene and o‐xylene

A novel strategy was proposed for the fabrication of high‐performance acidic mesoporous poly ionic liquids catalyst. In this work, mesoporous poly ionic liquids (MPILs) were synthesized with P123 (PEO₂₀PPO₇₀PEO₂₀) served as pore‐forming agent. Then, MPILs were treated with PW^3? anion exchange, thereby fabricating PW/MPIL‐S(x). MPIL and PW/MPIL‐S(x) were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), Thermogravimetric analysis (TA), N₂ adsorption–desorption and Fourier transform infrared (FT‐IR) spectra and X‐ray photoelectron spectroscopy (XPS) spectra. The effect of solvent and concentration of P123 on the morphology and mesoporous structure of MPILs were investigated systematically. And the results show that MPILs were featured with mesoporous channel structure, high surface area (up to 737 m²/g) and large pore volumes (1.16 cm³/g), which benefit heterogeneous phase reaction (such as, alkylation of styrene with o‐xylene). In the alkylation reaction, under optimal reaction conditions, the catalyst PW/MPIL‐THF (4.0 g) shows high conversion of styrene (100%) and PXE yield (96.21%), demonstrating the excellent catalytic activities. Furthermore, PW/MPIL‐S(x) are easy to be separated from the catalytic system by filtration and show no obvious decrease in catalytic activity after 6 cycle runs. The obtained PW/MPIL‐S(x) catalyst exhibit high thermal and mechanical stability as well, indicating extensive application in high temperature acidic catalysis. This work might open up a new method for the synthesizing of porous polymer catalysts in the future.     

Solid‐phase extraction combined with dispersive liquid–liquid microextraction for the determination of pyrethroid pesticides in wheat and maize samples

A rapid, selective and sensitive sample preparation method based on solid‐phase extraction combined with the dispersive liquid–liquid microextration was developed for the determination of pyrethroid pesticides in wheat and maize samples. Initially, the samples were extracted with acetonitrile and water solution followed phase separation with the salt addition. The following sample preparation involves a solid‐phase extraction and dispersive liquid–liquid microextraction step, which effectively provide cleanup and enrichment effects. The main experimental factors affecting the performance both of solid‐phase extraction and dispersive liquid–liquid microextration were investigated. The validation results indicated the suitability of the proposed method for routine analyze of pyrethroid pesticides in wheat and maize samples. The fortified recoveries at three levels ranged between 76.4 and 109.8% with relative standard deviations of less than 10.7%. The limit of quantification of the proposed method was below 0.0125 mg/kg for the pyrethoroid pesticides. The proposed method was successfully used for the rapid determination of pyrethroid residues in real wheat and maize samples from crop field in Beijing, China.     

The electronic structure of a diarsaallene –As=C=As– and a phosphaarsaallene –P=C=As–: UV photoelectron spectroscopy and theoretical studies

The electronic properties of a diarsaallene ArAs=C=AsAr and a phosphaarsaallene ArP=C=AsAr (Ar: 2,4,6-tri-tert-butylphenyl) have been investigated by using UV photoelectron spectroscopy and by density functional calculations on model compounds [(CH₃)₂C₆H₃Pn=C=AsC₆H₃(CH₃)₂, Pn: As, P]. Moreover, a comparison of the geometrical and electronic structures of the parent heteroallenes with those of the arsaethene H₂C=AsH and phosphaethene H₂C=PH has also been undertaken in order to determine the magnitude of the interaction between the π bond and the pnictogen lone pair n_Pn.     

One‐pot solvent and catalyst‐free synthesis of functionalized 1,8‐naphthyridines and quinolines by microwave irradiation

A series of functionalized, aryl substituted naphthyridines and quinolines has been synthesized by microwave‐assisted one‐pot two‐component synthesis under solvent‐free conditions in good yields by the reaction of a variety of aryl or heteroaryl amines and aryl vinyl ketones. A combinatorial type approach for a one‐step microwave reaction has been developed where a ring‐closing condensation is followed by a spontaneous aromatization to afford the functionalized aryl substituted 1,8‐naphthyridines and quinolines.     

An approach to creating novel anions: silylated triel compounds with –CH2– and –O– linkers, [InCl2{O(HO)Si(t‐Bu)2}]2 and Li[B(CH2SiMe3)4]

Bis[μ‐di‐tert‐butyl(hydroxy)silanolato]bis[chloridoindium(III)], [In₂(C₈H₁₉O₂Si)₂Cl₄], (I), is a centrosymmetric two‐centre indium complex featuring a system of three annulated four‐membered rings; the structure is the first example of an In₂O₂ ring which is annulated with two Si—O units to form a ring system composed of three rings. The coordination environment of the In centres is a distorted trigonal bipyramid. The crystal packing of (I) is characterized by chains of molecules connected by O—H...Cl hydrogen bonds. The crystal of (I) was a nonmerohedral twin. There is no known example of an In₂O₂ ring in which the In atoms carry any two halogen ligands. The structure of tetrakis(tetrahydrofuran)lithium tetrakis[(trimethylsilyl)methyl]borate, [Li(C₄H₈O)₄](C₁₆H₄₄BSi₄), (II), is composed of discrete cations and anions. The coordination geometries of the Li and B centres is tetrahedral. The cations and anions lie in planes parallel to the ab plane. There are no short contacts between the cations and anions. Compound (II) is the first example of a B centre bonded to four –CH₂Si units.     

Rate constants for the reaction of O(3P) atoms with CH2 = CHF,CH2 = CHCl,and CH2 = CHBr at 298 ± 2°K

Absolute rate constants for the reaction of O(³P) atoms with CH₂ = CHF, CH₂ = CHCl, and CH₂ = CHBr have been obtained at 298 ± 2°K using a modulation phase shift technique. The rate constants (k₂ × 10^?8 l./mole · sec) obtained are: CH₂ = CHF (1.61 ± 0.20), CH₂ = CHCl (2.54 ± 0.26), and CH₂ = CHBr (2.45 ± 0.25). These rate constants are lower than those determined by discharge flow techniques, but that for CH₂ = CHF is in good agreement with relative rate measurements.     

Functional polymers and sequential copolymers by phase transfer catalysis. XXVI. Synthesis and characterization of thermotropic liquid crystalline polypodants

Thermotropic liquid crystalline (LC) polyethers and copolyethers have been synthesized from 4,4′-dihydroxy-α-methylstilbene (HMS) and α,ω-dichlorooligo(oxyethylene)s having between 2 and 5 as well as 8.7 oxyethylene units. Copolyethers were prepared from a 1:1 mol/mol ratio of two dissimilar spacers. These polymers have been prepared by a phase transfer catalyzed (PTC) polyetherification of bisphenols with these electrophiles by utilizing 50 mol% tetrabutylammonium hydrogen sulfate per phenol group. Kinetic experiments with either 5 or 50 mol% catalyst vs phenol groups in the polyetherification of 4,4%-isopropylidenediphenol with 2-chloroethyl ether have shown that a change in catalyst primarily affects the rate of reaction, with 50 mol % being faster. The prepared polyethers and copolyethers are soluble in common organic solvents. Both polyethers and copolyethers are crystalline. Polymers prepared to contain tetraoxyethylene spacers exhibit monotropic LC behavior. Copolymers prepared to contain tri- and tetraoxyethylene spacers (1 : 1 mol/mol) [PE34] were the only polymers exhibiting enantiotropic LC behavior. Longer spacers tend to destabilize the phase transitions, as suggested by the dependence of thermal transition temperatures upon the differential scanning calorimeter rate. All prepared polymers act as podants in solution, measured by picrate extraction experiments. Solid state complexes have been prepared from the polymer with a pentaoxyethylene spacer [PE5] and PE34 with LiCF₃SO₃. PE5 can dissolve LiCF₃SO₃ in the range of 0.21–2.2 mol salt/mol polymer (m.r.u.) [S/P] without the observation of free salt. PE5 complexes of/or below S/P of 0.43, upon annealing at room temperature, exhibited the two melting transitons observed in the polymer alone. PE5 complexes of/or above S/P of 0.77 only exhibited a T_g. The T_g of PE5 complexes were found to change nonlinearly with S/P, while T_m1 changed linearly. T_m2 was independent of S/P. Only one complex with PE34 gave two transitions (T_m2,Tⁱ) in dynamic DSC experiments. Other PE34 complexes followed a behavior similar to PE5 complexes.