A Convenient Method for the Preparation of 1,5‐Diaryl‐3‐(arylamino)‐1H‐pyrrol‐2(5H)‐ones

A simple and eco‐friendly method for the preparation of 1,5‐diaryl‐3‐(arylamino)‐1H‐pyrrol‐2(5H)‐ones via the cyclo‐condensation reaction of aldehydes, amines and ethyl pyruvate in the presence of silica supported ferric chloride (SiO₂‐FeCl₃) as reusable heterogeneous catalyst is described. The present methodology offers several advantages such as excellent yields, simple procedure and short reaction times.     

Preparation of Tin Oxide-Based Metal Oxide Particles

Tin oxide-doped hybrid particles were prepared by a wet chemical process with organic-inorganic (phenyl/silica) hybrid particles in an alcoholic solution. The phenyl/silica hybrid particles, with a diameter of ca. 790 nm were used as a new support material for tin oxide (SnO₂) particles from tin(IV) chloride. The surface of the particles was modified via nitration of aromatic groups in the particles, to promote formation of the tin oxide coating on the particles. The thickness and surface morphology of the tin oxide layer coated on the nitrated-phenyl/silica hybrid particles could be controlled by varying the tin(IV) chloride concentration and reaction time. The size and morphology of the resultant particles were investigated with field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The particles obtained were also characterised by infrared (FTIR) and solid-state ¹³C magic angle spinning nuclear magnetic resonance (¹³C-CP/MAS NMR) spectroscopy. The effect of processing parameters on the crystallinity and structure of the doped hybrids were confirmed by X-ray diffraction (XRD) patterns.     

Mechanism for the formation of tin oxide nanoparticles and nanowires inside the mesopores of SBA-15

The formation of polycrystalline tin oxide nanoparticles (NP) and nanowires was investigated using nanocasting approach included solid-liquid strategy for insertion of SnCl₂ precursor and SBA-15 silica as a hard template. HR-TEM and XRD revealed that during the thermal treatment in air 5 nm tin oxide NP with well defined Cassiterite structure were formed inside the SBA-15 matrix mesopores at 250 °C. After air calcination at 700 °C the NP assembled inside the SBA-15 mesopores as polycrystalline nanorods with different orientation of atomic layers in jointed nanocrystals. It was found that the structure silanols of silica matrix play a vital role in creating the tin oxide NP at low temperature. The pure tin chloride heated in air at 250 °C did not react with oxygen to yield tin oxide. Tin oxide NP were also formed during the thermal treatment of the tin chloride loaded SBA-15 in helium atmosphere at 250 °C. Hence, it is well evident that silanols present in the silica matrix not only increase the wetting of tin chloride over the surface of SBA-15 favoring its penetration to the matrix pores, but also react with hydrated tin chloride according to the proposed scheme to give tin oxide inside the mesopores. It was confirmed by XRD, N₂-adsorption, TGA-DSC and FTIR spectra. This phenomenon was further corroborated by detecting the inhibition of SnO₂ NP formation at 250 °C after inserting the tin precursor to SBA-15 with reduced silanols concentration partially grafted with tin chloride.     

Novel substituted epoxide initiators for the carbocationic polymerization of isobutylene

This article presents the first detailed account of the discovery that substituted epoxides can initiate the carbocationic polymerization of isobutylene. α‐Methylstyrene epoxide (MSE), 2,4,4‐trimethyl‐pentyl‐epoxide‐1,2 (TMPO‐1), 2,4,4‐trimethyl‐pentyl‐epoxide‐2,3 (TMPO‐2), and hexaepoxi squalene (HES) initiated isobutylene polymerization in conjunction with TiCl₄. MSE, TMPO‐2, and HES initiated living polymerizations. A competitive reaction mechanism is proposed for the initiation and propagation. According to the proposed mechanism, initiator efficiency is defined by the competition between the S_N1 and S_N2 reaction paths. A controlled initiation with external epoxides such as MSE should yield a primary hydroxyl head group and a tert‐chloride end‐group. The presence of tert‐chloride end‐groups was verified by NMR spectroscopy, whereas the presence of primary hydroxyl groups was implied by model experiments. Multiple initiation by HES was verified by diphenyl ethylene end‐capping and NMR analysis; the resulting star polymer had an average of 5.2 arms per molecule. A detailed investigation of the reaction mechanism and the characterization of the polymers are in progress. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 444–452, 2000     

Synthesis of 4μ‐PS2PEO2, 4μ‐PS2PCL2, 4μ‐PI2PEO2, and 4μ‐PI2PCL2 star‐shaped copolymers by the combination of glaser coupling with living anionic polymerization and ring‐opening polymerization

4μ‐A₂B₂ star‐shaped copolymers contained polystyrene (PS), poly(isoprene) (PI), poly(ethylene oxide) (PEO) or poly(ε‐caprolactone) (PCL) arms were synthesized by a combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). Firstly, the functionalized PS or PI with an alkyne group and a protected hydroxyl group at the same end were synthesized by LAP and then modified by propargyl bromide. Subsequently, the macro‐initiator PS or PI with two active hydroxyl groups at the junction point were synthesized by Glaser coupling in the presence of pyridine/CuBr/N,N,N ′,N ″,N ″‐penta‐methyl diethylenetri‐amine (PMDETA) system and followed by hydrolysis of protected hydroxyl groups. Finally, the ROP of EO and ε‐CL monomers was carried out using diphenylmethyl potassium (DPMK) and tin(II)‐bis(2‐ethylhexanoate) (Sn(Oct)₂) as catalyst for target star‐shaped copolymers, respectively. These copolymers and their intermediates were well characterized by SEC, ¹H NMR, MALDI‐TOF mass spectra and FT‐IR in details. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Characterization of ABTS at a Polymer‐Modified Electrode

ABTS, 2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonate), a colorless dianion that forms a colored radical upon oxidation, was characterized with electrochemistry and spectroscopy and demonstrated to be a detectable analyte in a polymer‐modified spectroelectrochemical sensor. Three positively charged polymers were incorporated into a thin film on an indium tin oxide (ITO) optically transparent electrode and used to concentrate ABTS at the electrode surface. Of the three films, poly(vinylbenzyl trimethyl ammonium chloride)‐poly(vinyl alcohol) (PVTAC‐PVA), poly(diallyldimethylammonium chloride)‐silica (PDMDAAC‐SiO₂), and quaternized poly(4‐vinyl‐N‐methylpyridinium nitrate)‐silica (QPVP‐SiO₂), PVTAC‐PVA demonstrated the best ability to absorb ABTS. Within 20 min, a change of 0.2 absorbance units at 417 nm and 13.6 μA/cm² in anodic peak current density in cyclic voltammetry at a scan rate of 0.025 V/s were observed.     

Ruthenium‐catalyzed formation of quinolines via reductive cyclization of nitroarenes with tris(3‐hydroxypropyl)amine in an aqueous medium

Nitroarenes react with tris(3‐hydroxypropyl)amine in an aqueous medium (dioxane/H₂O) at 180° in the presence of a catalytic amount of a ruthenium catalyst and tin(II) chloride along with isopropanol as hydrogen donor to afford the corresponding quinolines in good yields. The presence of tin(II) chloride is essential for the formation of quinolines. A reaction pathway involving initial reduction of nitroarenes to anilines, propanol group transfer from tris(3‐hydroxypropyl)amine to anilines to form 3‐anilino‐1‐propanols, N‐alkylation of anilines by 3‐anilino‐1‐propanol to form 1,3‐dianilinopropane and intramolecular heteroannulation of 1,3‐dianilinopropane is proposed for this catalytic process.     

Silica‐Grafted Tris(neopentyl)aluminum: A Monomeric Aluminum Solid Co‐catalyst for Efficient Nickel‐Catalyzed Ethene Dimerization

A silica‐supported monomeric alkylaluminum co‐catalyst was prepared via surface organometallic chemistry by contacting tris(neopentyl)aluminum and partially dehydroxylated silica. This system, fully characterized by solid‐state ²⁷Al NMR spectroscopy augmented by computational studies, efficiently activates (ⁿBu₃P)₂NiCl₂ towards dimerization of ethene, demonstrating comparable activity to previously reported dimeric diethylaluminum chloride supported on silica. Three types of aluminum surface species have been identified: monografted tetracoordinated Al species as well as two types of bisgrafted Al species—tetra‐ and pentacoordinated. Of them, only the monografted Al species is proposed to be able to activate the (ⁿBu₃P)₂NiCl₂ complex and generate the active cationic species.     

Eco‐friendly and Efficient Synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones

A simple and facile method for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones through the direct cyclocondensation of one‐pot three‐component cyclocondensation of isatoic anhydride, ammonium acetate (or primary amines) and aldehydes; and anthranilamide and aldehydes using silica supported ferric chloride (SiO₂‐FeCl₃) as catalyst under solvent‐free conditions is described.     

Solid‐state synthesis of a new core–shell nanocomposite of polyaniline and silica via oxidation of aniline hydrochloride by FeCl3.6H2O

Among the different oxidants used for the preparation of polyaniline in the solid‐state, iron (III) chloride (FeCl₃.6H₂O) can act as both oxidant and dopant. This work reports the synthesis and characterization of novel composite of polyaniline/silica. The polymerization was performed by oxidative polymerization of aniline hydrochloride in the presence of silica and FeCl₃.6H₂O under solid‐state (solvent‐free) condition. The FeCl₃.6H₂O has been chemically supported on silica and generated silica‐supported FeCl₃ ( SSFe ), which plays three important roles simultaneously (a) oxidant, (b) primary dopant, and (c) secondary dopant (Lewis acid). Furthermore, the existence of silica is important for proceeding of polymerization in solid state. In the other words, the surface polymerization and green chemistry in solid state have been coupled. The characterization and doping process are verified by ultraviolet‐visible, Fourier transform infrared, atomic absorption spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and elemental analysis (CHNS). From atomic absorption spectroscopy the ratio of Fe/N in the composite obtained about 1, which confirms the formation of delocalized polarons by SSFe in the composites. The conductivity is in the range of semi‐conductive. Furthermore, contact resistance was determined by circular‐transmission line measurement. According to scanning electron microscopy images silica particles have been thoroughly coated by polyaniline within the range of 0.2 to 1 µm. However, transition electron microscopy images depict the uniform solid nanospheres (no hollow spheres or fibers), and their mean diameters are under of 50 nm. It confirms nanocomposite of core–shell PANI‐SSFe. Copyright © 2016 John Wiley & Sons, Ltd.     

Coordination polymers based on building blocks of dimethyltin(IV) Chloride iso‐thiocyanate and dimethyltin(IV) di‐iso‐thiocyanate with pyrazine‐2‐carboxylate and 4, 4′‐bipyridine

The reaction of 4,4′‐bipy with dimethyltin(IV) chloride iso‐thiocyanate affords the one‐dimensional (1D) coordination polymer, [Me₂Sn(NCS)Cl·(4,4′‐bipy)]_n ( 1 ), whereas reaction of dimethyltin(IV) dichloride with sodium pyrazine‐2‐carboxylate in the presence of potassium iso‐thiocyanate affords the two‐dimensional (2D) coordination polymer, {[Me₂Sn(C₄H₃N₂COO)₂]₂ [Me₂Sn(NCS)₂]}_n ( 2 ). Both coordination polymers were characterized by elemental analysis and infrared spectroscopy in addition to ¹H and ¹³C NMR spectroscopy of the soluble coordination polymer ( 1 ). A single‐crystal structure determination showed that the asymmetric unit in 1 contains Me₂Sn(NCS)Cl and 4,4′‐bipy moieties and a 1D infinite rigid chain structure forms through bridging of the 4,4′‐bipy ligand between tin atoms and the geometry around the tin atom is a distorted octahedral. Coordination polymer 2 contains two distinct tin atom geometrics in which one tin atom is seven coordinate, and the other is six coordinate. The two tin atom environments are best described as a pentagonal bipyramidal in the former and distorted octahedral in the latter where the carboxylate groups bridge the two tin atoms and construct a 2D‐coordination polymer. The ¹¹⁹Sn NMR spectroscopy indicates the octahedral geometry of 1 retains in solution. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:699–706, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/.20736     

Iron powder and tin/tin chloride as new reducing agents of Meerwein arylation reaction with unexpected recycling to anilines

Abstract

Simple and rapid route for Meerwein arylation reaction using iron powder or a mixture of tin/tin chloride has been developed. In the presence of iron powder, different aryl diazonium salts reacted with methyl vinyl ketone, acrylates, and isopropenyl acetate. Production of oximes was detected as the main product with acrylates or in a mixture with β-aryl methyl ketones in the case of methyl vinyl ketone. The in situ produced HNO₂ from an excess of NaNO₂/HCl was trapped by alkyl aryl radical to form oximes in the E configuration form. The presence of tin/tin chloride mixture in the reaction of the aryl diazonium salts with methyl vinyl ketone produced Michael products along with β-aryl methyl ketones. The predicted α-aryl methyl ketones from the reaction of isopropenyl acetate with the diazotized anilines were obtained using iron or tin/tin chloride mixture.     

Synthesis of adaptative and amphiphilic polymer model conetworks by versatile combination of ATRP,ROP, and “Click chemistry”

Well‐defined adaptative and amphiphilic polymer conetworks based on hydrophilic poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PDMAEMA) and hydrophobic poly(ε‐caprolactone) (PCL) have been prepared by combination of ATRP, ROP, and “Click chemistry.” Telechelic α,ω‐alkyne terminated PCL crosslinker was obtained by ring‐opening polymerization (ROP) of CL in THF at 80 °C initiated by 1,4‐butanediol and catalyzed by tin(II) bis 2‐ethyl hexanoate (Sn(Oct)₂), followed by the quantitative esterification of hydroxyl end‐groups by activated 4‐pentynoic acid. In parallel, an azido‐containing PDMAEMA‐based copolymer was obtained in a three‐step strategy involving primarily the copolymerization of DMAEMA with newly synthesized 2‐(2‐azidoethoxy)ethyl methacrylate (AEEMA) monomer. The latter was obtained by nucleophilic substitution of chloride atom from 2‐(2‐chloroethoxy)ethanol by an azide group followed by the esterification reaction of the hydroxyl group with methacrylic anhydride. The copolymerization was carried out in an equivolumic mixture of H₂O and isopropanol at r.t. and initiated by a ω‐bromoisobutyryl oligo PEO macroinitiator in the presence of various ligated copper(I)‐based catalysts. In a last step, both polymer precursors were chemically linked by the Huisgen‐1,3‐dipolar cycloaddition in anhydrous THF at r.t. using CuBr complexed by 2,2′‐bipyridine ligand as catalyst. Final material was characterized by the means of DSC and SEM, both attesting of a homogeneous distribution of the PCL crosslinkers and a highly porous structure in this new amphiphilic model conetworks. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4997–5013, 2008     

Melt transesterification and characterization of segmented block copolyesters containing 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol

Conventional melt transesterification successfully produced high‐molecular‐weight segmented copolyesters. A rigid, high‐T_g polyester precursor containing the cycloaliphatic monomers, 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol, and dimethyl‐1,4‐cyclohexane dicarboxylate allowed molecular weight control and hydroxyl difunctionality through monomer stoichiometric imbalance in the presence of a tin catalyst. Subsequent polymerization of a 4000 g/mol polyol with monomers comprising the low‐T_g block yielded high‐molecular‐weight polymers that exhibited enhanced mechanical properties compared to a nonsegmented copolyester controls and soft segment homopolymers. Reaction between the polyester polyol precursor and a primary or secondary alcohol at melt polymerization temperatures revealed reduced transesterification of the polyester hard segment because of enhanced steric hindrance adjacent to the ester linkages. Differential scanning calorimetry, dynamic mechanical analysis, and tensile testing of the copolyesters supported the formation of a segmented multiblock architecture. Further investigations with atomic force microscopy uncovered unique needle‐like, interconnected, microphase separated surface morphologies. Small‐angle X‐ray scattering confirmed the presence of microphase separation in the segmented copolyesters bulk morphology. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Polystyrene and Silica Gel–Supported,AlCl3-Catalyzed Preparation of Diaryl Sulfoxides from Arenes and Thionyl Chloride

A simple, chemoselective, and efficient method has been developed for direct conversion of arenes to symmetrical diaryl sulfoxides using thionyl chloride in the presence of a catalytic amount of cross-linked polystyrene-supported aluminium chloride (Ps-AlCl₃) and silica gel–supported aluminium chloride (SiO₂-AlCl₃). These solid acid catalysts are stable and can be easily recovered and reused without appreciable change in their efficiency.     

Direct functionalization of polyisobutylene by living initiation with α‐methylstyrene epoxide

This article describes the synthesis and characterization of polyisobutylene (PIB) carrying one primary hydroxyl head group and a tertiary chloride end group, [Ph? C(CH₃)(CH₂OH)–PIB–CH₂? C(CH₃)₂Cl] prepared with direct functionalization via initiation. The polymerization of isobutylene was initiated with the α‐methylstyrene epoxide/titanium tetrachloride system. Living conditions were obtained from ?75 to ?50 °C (198–223 K). Low molecular weight samples (number‐average molecular weight ～ 4000 g/mol) were prepared under suitable conditions and characterized by Fourier transform infrared and ¹H NMR spectroscopy. The presence of primary hydroxyl head groups in PIB was verified by both methods. Quantitative Fourier transform infrared with 2‐phenyl‐1‐propanol calibration and ¹H NMR performed on both the hydroxyl‐functionalized PIB and its reaction product with trimethylchlorosilane showed that each polymer chain carried one primary hydroxyl head group. The synthetic methodology presented here is an effective and simple route for the direct functionalization of PIB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1005–1015, 2002     

A Rapid and Convenient Synthesis of Acylals from Aldehydes and Acetic Anhydrides Catalyzed by SnCl_4/SiO_2

Acylals (1, 1-diacetates) are efficient protecting groups for aldehydes as they are stable in neutral and basic media1. Usually, the acylals are prepared from aldehydes and acetic anhydride in the presence of strong protonic acids such as sulfuric acid2, phosphoric acid2, or methanesulfonic acid2, and Lewis acids such as anhydrous zinc chloride3, phosphorus(III) chloride4, and anhydrous ferric(III) chloride5. Recently the use of montmorillonite clay7, TMCS-NaI8, Sc (OTf)39, Cu (OTf)210 …     

Ruthenium‐catalyzed synthesis of quinolines via reductive heteroannulation of nitroarenes with 3‐amino‐1‐propanols

Nitroarenes are reductively cyclized with 3‐amino‐1‐propanols in dioxane/H₂O in the presence of a ruthenium catalyst and tin(II) chloride dihydrate together with isopropanol to afford the corresponding quinolines. A reaction pathway involving initial reduction of nitroarenes to anilines, propanol group transfer from 3‐amino‐1‐propanols to anilines, N‐alkylation of anilines by 3‐anilino‐1‐propanols and heteroannulation of 1,3‐dianilinopropanes is proposed.     

Nonenzymatic H2O2 Electrochemical Sensor Based on SnO2‐NPs Coated Polyethylenimine Functionalized Graphene

This paper demonstrated using polyethylenimine (PEI)‐functionalized graphene (Gr) incorporating tin oxide (SnO₂) hybrid nanocomposite as a platform for nonenzymatic H₂O₂ electrochemical sensor. The results of UV‐vis spectroscopy and X‐ray diffraction (XRD) confirmed the simultaneous formation of tin oxide (SnO₂) nanocomposite and reduction of graphene oxide (GO). Transmission electron microscopy (TEM) images showed a uniform distribution of nanometer‐sized tin oxide nanoparticles on the grapheme sheets, which could be achieved using stannous chloride (SnCl₂) complex instead of tin oxide as precursor. The electrochemical measurements, including cyclic voltammetry (CV) and amperometric performance (I‐t), showed that the PEI‐functionalized Gr supported SnO₂ (SnO₂‐PEI‐Gr) exhibited an excellent electrocatalytic activity toward the H₂O₂. The corresponding calibration curve of the current response showed a linear detection range of 9×10⁻⁶∼1.64×10⁻³ mol L⁻¹, while the limit of detection was estimated to be 1×10⁻⁶ mol L⁻¹. Electrochemical studies indicated that SnO₂ and functionalized Gr worked synergistically for the detection of H₂O₂.     

Synthesis and NMR Characterization of Multi‐hydroxyl End‐groups PEG and PLGA‐PEG Barbell‐like Copolymers

Multi‐hydroxyl end‐groups poly(ethylene glycol) (PEG) was prepared from PEG and epichlorohydrin. Then, PEG‐supported poly(lactic‐ran‐glycolic acid) (PLGA)_n‐PEG‐(PLGA)_n (n=1, 2, 4) linear‐dendritic barbell‐like copolymers were synthesized through direct polycondensation under bulk condition from the multi‐hydroxyl end‐groups PEG, lactic acid and glycolic acid. Arm numbers were varied, with 2, 4 and 8, by using bis‐, tetra‐, and octa‐hydroxyl end‐groups PEG, respectively. The chemical structures, absolute number‐average molecular weight, the monomer units per single arm and the molar ratio of hydroxyl acid monomer units of the (PLGA)_n‐PEG‐(PLGA)_n barbell‐like copolymers were analyzed by NMR spectroscopy. The result indicated that the structures of the multi‐hydroxyl end‐groups PEG and (PLGA)_n‐PEG‐(PLGA)_n barbell‐like copolymers were consistent with design. Compared with the theoretical values, molecular weights determined by ¹H‐NMR end‐group analysis gave reasonably consistent values, but the values determined by gel permeation chromatography (GPC) were considerably less than theoretical values. The results indicated that (PLGA)_n‐PEG‐(PLGA)_n copolymers have linear‐dendritic structures.