Showing papers on "Styrene oxide published in 2016"

Zn-salen complexes with multiple hydrogen bonding donor and protic ammonium bromide: Bifunctional catalysts for CO2 fixation with epoxides at atmospheric pressure

Abstract: Bifunctional Zn-salen complexes with multiple hydrogen bonding donors and protic ammonium bromides were developed as efficient catalysts for the formation of 4-phenyl-1,3-dioxolan-2-one from styrene oxide and CO2. Owing to synergistic effects of multiple sites on epoxide activation (Lewis acidic zinc, phenolic hydroxyl group and protonated tertiary ammonium able to activate epoxide and bromide anion acting as a nucleophile), the easily-synthesized Zn-salen complexes showed outstanding performance at mild reaction conditions (CO2 0.1 MPa, 100 °C) using only 0.3 mol% catalyst amount. Besides, this protocol is applicable to a variety of epoxides including internal epoxide, giving the corresponding cyclic carbonates in good to excellent yields. Notably, 200 mmol-scale experiment was successfully conducted and TON of 49288 ± 13 and TOF of 39473 ± 8 h−1 were achieved.

Influence of functionalization of terephthalate linker on the catalytic activity of UiO-66 for epoxide ring opening

Abstract: A series of five isostructural zirconium terephthalate UiO-66 metal organic frameworks bearing different functional groups on the terephthalate linker (UiO-66-X; X = H, NH2, NO2, Br, Cl,) have been successfully prepared and characterized. UiO-66-X materials were evaluated as heterogeneous catalysts for the epoxide ring opening of styrene oxide by methanol, observing an increase in the initial reaction rate from UiO-66-H to UiO-66-Br, over one order of magnitude. The reactivity order, however, does not follow a linear relationship between the Hammett constant value of the substituent and the initial reaction rate. UiO-66-Br exhibits a wide scope, its activity depending on the structure of epoxide and nucleophile. The absence of Zr leaching to the solution together with the preservation of the UiO-66-X crystallinity confirms the stability of the framework under the reaction conditions. Nevertheless, UiO-66 undergoes a progressive deactivation upon reuse that was attributed to a strong adsorption of the reaction product.

Modified Ti/MCM-41 catalysts for enantioselective epoxidation of styrene

Abstract: Ti sites grafted on MCM-41, pretreated at different temperatures, have been modified with chiral tartrates, leading to different species. Those solids are active catalyst for the epoxidation of styrene with tert-butyl hydroperoxide, although their efficiency is not optimal, mainly due to the subsequent epoxide rearrangement to phenyl acetaldehyde and further oxidation of it. Styrene oxide is obtained with moderate enantioselectivity, in the range of 55–62% e.e., and the best overall results correspond to the use of MCM-41 calcined at the lowest temperature (550 °C). These results are much better with regard to styrene oxide selectivity than those obtained in homogeneous phase under the same conditions, whereas enantioselectivity is similar. The heterogeneous catalysts are recoverable, but only partially due to a loss in activity, although enantioselectivity is kept at similar levels, demonstrating the stability of the supported Ti-tartrate species.

Catalytic evaluation of dendrimer and reverse microemulsion template Pd and Pt nanoparticles for the selective oxidation of styrene using TBHP

Abstract: Here, we employed colloidal Pd and Pt nanoparticles synthesized by dendrimer templates as well as reverse microemulsions in the selective oxidation of styrene using tert -butyl hydroperoxide (TBHP) as an oxidant. We investigate their catalytic behavior and the feasibility as oxidation catalysts. High selectivity to styrene oxide, was achieved in the oxidation of styrene. The catalytic activities in terms of styrene conversion decreased in the order of dendrimer-templated Pd nanoparticles > thiol-capped Pd nanoparticles by reverse microemulsions > dendrimer-templated Pt nanoparticles > thiol-capped Pt nanoparticles by reverse microemulsions. This indicated that Pd-based catalysts were more efficient to catalyze the styrene oxidation reaction as compared to Pt-based catalysts. Furthermore, the dendrimer template synthetic method produced catalysts with higher activity as compared to those prepared by the reverse microemulsion template. The catalytic activities and selectivity profiles in various reaction conditions such as solvent type, styrene to TBHP ratio, type of catalysts, catalyst dosing, and temperature are discussed. The changes of average nanoparticle size after the reactions and the recyclability of Pd and Pt catalysts are examined. Overall results indicated that although higher catalytic activities were obtained with the use of dendrimer-templated nanoparticles, better recyclability as well as selectivity to styrene oxide was achieved with the use of thiol-capped Pd nanoparticles synthesized by reverse microemulsions.

Ring-Opening Alternating Copolymerization of Epoxides and Dihydrocoumarin Catalyzed by a Phosphazene Superbase

Abstract: 3,4-Dihydrocoumarin (DHC), a six-membered phenolic lactone derived from natural resources, which does not undergo homopolymerization, was subject to ring-opening anionic copolymerization with several epoxides (ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, and 2-ethylhexyl glycidyl ether) from a mono- or dialcohol catalyzed by a phosphazene superbase (t-BuP4). Spectroscopic analysis revealed that the products were aromatic poly(ether–ester)s with perfect alternating monomeric sequences, consisting of both linear alternating copolymers and cyclic ones with relatively lower molar masses caused by intramolecular transesterification reactions. The alternating copolymers showed good thermal stability and higher glass transition temperatures as compared with the homopolymers of the corresponding epoxides. The in situ initiator-activation and chain-growth mechanism of the t-BuP4-catalyzed polymerization also allowed for copolymerization of DHC and epoxides from multifunctional initiators, su...

Halogenated meso-phenyl Mn(III) porphyrins as highly efficient catalysts for the synthesis of polycarbonates and cyclic carbonates using carbon dioxide and epoxides

Abstract: Introduction of halogen electron withdrawing atoms (chloro and fluoro) in the ortho position of the aryl groups of meso -tetraphenylporphyrin manganese(III) complexes increased their activity as catalysts in the reaction of carbon dioxide with epoxides, when compared with the meso -tetraphenylporphyrin manganese(III) counterpart, even in the absence of co-catalysts. In the polymerization reaction of carbon dioxide and cyclohexene oxide, almost ten-fold increase of the TOF was observed when 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrinatomanganese(III) acetate or 5,10,15,20-tetra(2,6-difluorophenyl)porphyrinatomanganese(III) acetate complexes were used as catalysts. Under similar conditions, when terminal epoxides were used as substrates, the selective cycloaddition of CO 2 with styrene oxide, epichlorohydrin, propylene oxide, and 1,2-epoxytetradecane yielded exclusively the corresponding cyclic carbonates (conversion 6–98%).

Spectroscopy and catalytic activity study of gold supported on barium titanate nanotubes for styrene epoxidation

Abstract: Gold (05–5 wt%) supported on barium titanate nanotubes (Au/BaTNT) were prepared, characterized and for the first time, investigated as catalysts for selective oxidation of styrene with oxygen (O 2 or H 2 + O 2 ) and peroxides (H 2 O 2 or TBHP) Conversion of styrene enhanced when H 2 was co-added to O 2 in the reactions Au/BaTNT activated O 2 and H 2 and produced H 2 O 2 in situ for use in oxidations Peroxides were found better oxidants than O 2 At optimized conditions, styrene oxide selectivity of 801 wt% at styrene conversion of 605 wt% was achieved over Au(1 wt%)/BaTNT using TBHP Au particles (50–74 nm) were dispersed and decorated on the walls of BaTNT They exhibited superior performance to the known Au catalysts in styrene oxidation Reactive oxygen species formed during oxidation reactions were followed with in situ spectral characterizations (diffuse reflectance UV–vis and FT-Raman) Au/BaTNT was reusable in four recycles with little loss in catalytic activity

Highly active and selective Zn(II)-NN′O Schiff base catalysts for the cycloaddition of CO2 to epoxides

Abstract: Mononuclear Zn(II) complexes with tridentate NN′O-donor base Schiff ligand N -(2-pyridyl)methyl-2-hydroxy-3,5-di- tert -butylbenzaldimine ( 1H ) combined with a co-catalyst are active for the cycloaddition of CO 2 and epoxides. They provide cyclic carbonates selectively even with the more hindered substrates such as cyclohexene oxide and methyl epoxyoleate. The best conditions were achieved running the reaction in expanded neat substrate in CO 2 as reaction media. The activity obtained for the cycloaddition of CO 2 to styrene oxide reached an initial TOF of 3733 h −1 . The solid state structures of [Zn( 1 ) 2 ] and [Zn( 1 )(OAc) 2 ] n were determined by X-ray diffraction methods. Relative stability of the species in solution was analysed by DFT calculations.

Aluminium salabza complexes for fixation of CO2 to organic carbonates.

Abstract: A highly stable and easy to synthesize aluminium complex bearing a flexible N2O2-donor salabza ligand (N,N′-bis(salicylene)-2-aminobenzylamine) in combination with tetrabutylammonium bromide forms an active binary catalytic system for the cycloaddition of CO2 to epoxides (TOFs 120–3434 h−1) under mild conditions (10 bar, 80 °C) and low catalyst loadings (0.05–0.2 mol%). Kinetic experiments have shown that the cycloaddition of CO2 to styrene oxide catalyzed by 1/TBAB is first order in 1, TBAB, CO2 and epoxide. A reaction mechanism is proposed based on these observations. Fe(III) and Co(III) related complexes are less active catalysts for this reaction.

Synthesis and structural characterization of titanium and zirconium complexes containing half-salen ligands as catalysts for polymerization reactions

Abstract: Complexes 1–7 were synthesized from tridentate half-salen ligands in good yields and purity. They were characterized by various spectroscopic techniques, elemental analyses, and X-ray crystallography. With titanium, homoleptic and heteroleptic complexes could be synthesized independently whereas with zirconium only homoleptic complexes could be synthesized. All the complexes were efficient and good catalysts for the ring-opening polymerization (ROP) of lactides (LA) and e-caprolactone (e-CL). The molecular weights (Mn) of the resulting poly(lactic acid) (PLA) and poly(caprolactone) (PCL) are close to the theoretical values, and the molecular weight distributions (MWDs) are narrowly distributed. Kinetic study showed that the ROP had a first-order dependency on monomer concentration. Next, preliminary studies on copolymerization of cyclohexene oxide (CHO) with CO2 were performed in the presence of tetrabutylammonium bromide (TBAB) as a cocatalyst. The results from DSC and TGA were used to describe the thermal properties of the copolymer. In addition, all the complexes can effectively catalyze the cycloaddition reactions of CO2 with propylene oxide (PO) and styrene oxide (SO) using TBAB as a cocatalyst. The formation of the homopolymerization product from CHO is witnessed in the absence of any cocatalyst. All the complexes, when activated by methylaluminoxane (MAO), showed potent catalytic efficiency towards the polymerization of ethylene. The impact of polymerization parameters such as time, temperature and solvents on the polymerization of ethylene is discussed elaborately.

Oxidation of ethylbenzene to styrene oxide in the presence of cellulose‐supported Pd magnetic nanoparticles

Abstract: Palladium and Fe3O4 nanoparticles were deposited on N-(2-aminoethyl)acetamide-functionalized cellulose for use in a catalytic reaction. The catalyst was characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, energy-dispersive X-ray analysis and transmission electron microscopy, and applied in the oxidation reaction of ethylbenzene at 100 °C using H2O2. Styrene oxide was obtained as the sole product of the oxidation reaction during 24 h. This reaction has some advantages such as one-pot transformation of ethylbenzene to styrene oxide, high yield, excellent selectivity and magnetically recoverable catalyst. Also, the recovered catalyst could be used in the oxidation reaction four times without decrease in yield. Copyright © 2016 John Wiley & Sons, Ltd.

Quantum Chemical Modeling of Enantioconvergency in Soluble Epoxide Hydrolase

Abstract: Soluble epoxide hydrolases (sEHs) catalyze the hydrolysis of epoxides to their corresponding vicinal diols. One property of a number of these enzymes is that they can catalyze the hydrolysis of some racemic substrates in an enantioconvergent one-enzyme fashion. Here, we have used the dispersion-corrected B3LYP-D3 density functional theory method to investigate the enantioconvergent conversion of styrene oxide (SO) by sEH from Solanum tuberosum (StEH1). A large cluster model of the active site, consisting of 279 atoms, is designed on the basis of the X-ray crystal structure of StEH1 in complex with the competitive inhibitor valpromide. Different substrate orientations of the two enantiomers of SO are examined, and the full reaction mechanisms for epoxide opening at the two carbons are calculated, including both the alkylation and hydrolysis half-reactions. The calculated overall reaction energy profiles show that the rate-determining step is associated with the dissociation of the covalent intermediate, wh...

A Lamellar Coordination Polymer with Remarkable Catalytic Activity

Abstract: A positively charged lamellar coordination polymer based on a flexible triphosphonic acid linker is reported. [Gd(H4 nmp)(H2 O)2 ]Cl⋅2 H2 O (1) [H6 nmp=nitrilotris(methylenephosphonic acid)] was obtained by a one-pot approach by using water as a green solvent and by forcing the inclusion of additional acid sites by employing HCl in the synthesis. Compound 1 acts as a versatile heterogeneous acid catalyst with outstanding activity in organic reactions such as alcoholysis of styrene oxide, acetalization of benzaldehyde and cyclohexanaldehyde and ketalization of cyclohexanone. For all reaction systems, very high conversions were reached (92-97 %) in only 15-30 min under mild conditions (35 °C, atmospheric pressure). The coordination polymer exhibits a protonic conductivity of 1.23×10(-5) S cm(-1) at 98 % relative humidity and 40 °C.

The structure of a one-electron oxidized Mn(III)-bis(phenolate)dipyrrin radical complex and oxidation catalysis control via ligand-centered redox activity

Abstract: The tetradentate ligand dppH3, which features a half-porphyrin and two electron-rich phenol moieties, was prepared and chelated to manganese. The mononuclear Mn(III)-dipyrrophenolate complex 1 was structurally characterized. The metal ion lies in a square pyramidal environment, the apical position being occupied by a methanol molecule. Complex 1 displays two reversible oxidation waves at 0.00 V and 0.47 V vs. Fc+/Fc, which are assigned to ligand-centered processes. The one-electron oxidized species 1+ SbF6− was crystallized, showing an octahedral Mn(III) center with two water molecules coordinated at both apical positions. The bond distance analysis and DFT calculations disclose that the radical is delocalized over the whole aromatic framework. Complex 1+ SbF6− exhibits an Stot = 3/2 spin state due to the antiferromagnetic coupling between Mn(III) and the ligand radical. The zero field splitting parameters are D = 1.6 cm−1, E/D = 0.18(1), g⊥ = 1.99 and g∥ = 1.98. The dication 12+ is an integer spin system, which is assigned to a doubly oxidized ligand coordinated to a Mn(III) metal center. Both 1 and 1+ SbF6− catalyze styrene oxidation in the presence of PhIO, but the nature of the main reaction product is different. Styrene oxide is the main reaction product when using 1, but phenylacetaldehyde is formed predominantly when using 1+ SbF6−. We examined the ability of complex 1+ SbF6− to catalyze the isomerization of styrene oxide and found that it is an efficient catalyst for the anti-Markovnikov opening of styrene oxide. The formation of phenylacetaldehyde from styrene therefore proceeds in a tandem E–I (epoxidation–isomerization) mechanism in the case of 1+ SbF6−. This is the first evidence of control of the reactivity for styrene oxidation by changing the oxidation state of a catalyst based on a redox-active ligand.

Activity of Molybdate-Intercalated Layered Double Hydroxides in the Oxidation of Styrene with Air

Abstract: Molybdate anions were intercalated into the interlayer spacings of (Mg, Al) like-hydrotalcite compounds as interlayer compensating anions. The synthesized samples have been characterized by XRD, FT-IR, Raman, EDS, UV–vis, BET, and XPS. The solids possess lamellar structure and uniform platelet particles. There is mainly Mo(VI) present in both tetrahedral and octahedral configuration in the samples. All the synthesized catalysts have been tested for the liquid oxidation of styrene at mild conditions. Under reported conditions, styrene conversion varies with the total amount of molybdate ions. Benzaldehyde and styrene oxide were two major components in the product mixture. The selectivity to styrene oxide was found to be associated with the nature of oxidants and the amount of tetrahedrally-coordinated Mo species in layered double hydroxides while that to benzaldehyde is related to the overall amount of MoO4 − anions in the sample. Product distribution obtained on Mg–Al–Molybdate like hydrotalcite catalysts in the liquid oxidation of styrene with air.

Synthesis of styrene carbonate from styrene oxide and CO2 over ZnBr2 supported on MCM-41—Coated magnetic Fe3O4

Abstract: ZnBr2 supported on magnetic nanoparticles Fe3O4 coated by MCM-41 (Fe3O4@MCM-41/ZnBr2) was prepared and characterized by infrared spectroscopy (IR), powder X-ray diffraction (XRD) and nitrogen adsorption–desorption isotherms. The as-prepared samples were used as a recyclable catalyst for solvent-free synthesis of styrene carbonate (SC) from styrene oxide (SO) and carbonate dioxide (CO2). The results showed that Fe3O4@MCM-41/ZnBr2 exhibited similar catalytic activity to homologous ZnBr2. It was found that the reaction depended on the reaction conditions in terms of the yield of SC. The yield of SC at 81.5% was obtained with 8 MPa CO2 pressure at 90 °C for 3 h. The supported catalyst Fe3O4@MCM-41/ZnBr2 can be easily recovered by a permanent magnet after the reaction and reused without further treatment. No significant change in the structure and loss in activity were observed. The yield of SC changed in a small range from 79.2 to 82.6% during 5 cycles.

Computational Insight on CO2 Fixation to Produce Styrene Carbonate Assisted by a Single‐Center Aluminum(III) Catalyst and Quaternary Ammonium Salts

Abstract: DFT calculations were used to investigate the cycloaddition reaction of CO2 to styrene oxide for the formation of styrene carbonate. The uncatalyzed process alongside the reactions assisted by tetrabutylammonium bromide (TBAB), the novel nonsymmetrical single-center aluminum(III) salen–acac hybrid complex (salenac) (Al1cat) and the binary Al1cat/TBAB system were all investigated and for all of them the optimized structures, rate-determining steps, and lowest energy barrier reaction pathways were intercepted for both gas-phase and solvent environments. For the catalyzed systems, the reaction mechanism consists of three key elementary steps: 1) epoxy ring opening; 2) CO2 electrophilic attack and 3) intramolecular cyclization. In the presence of Al1cat, the central metal of the catalyst coordinates with an oxygen atom of the epoxide, activating it towards a nucleophilic attack by the halide. An oxyanion species is formed that affords the corresponding cyclic carbonate after reaction with CO2. Our results provide important hints on the cycloaddition of CO2 and epoxides promoted by nonsymmetrical aluminum complex containing a single metal center, and can satisfactorily explain the previous experimental observations allowing the development of more efficient catalysts for organic carbonate production.

Conformational Diversity and Enantioconvergence in Potato Epoxide Hydrolase 1.

Abstract: Potato epoxide hydrolase 1 (StEH1) is a biocatalytically important enzyme that exhibits rich enantio- and regioselectivity in the hydrolysis of chiral epoxide substrates. In particular, StEH1 has been demonstrated to enantioconvergently hydrolyze racemic mixes of styrene oxide (SO) to yield (R)-1-phenylethanediol. This work combines computational, crystallographic and biochemical analyses to understand both the origins of the enantioconvergent behavior of the wild-type enzyme, as well as shifts in activities and substrate binding preferences in an engineered StEH1 variant, R-C1B1, which contains four active site substitutions (W106L, L109Y, V141K and I155V). Our calculations are able to reproduce both the enantio- and regioselectivities of StEH1, and demonstrate a clear link between different substrate binding modes and the corresponding selectivity, with the preferred binding modes being shifted between the wild-type enzyme and the R-C1B1 variant. Additionally, we demonstrate that the observed changes in selectivity and the corresponding enantioconvergent behavior are due to a combination of steric and electrostatic effects that modulate both the accessibility of the different carbon atoms to the nucleophilic side chain of D105, as well as the interactions between the substrate and protein amino acid side chains and active site water molecules. Being able to computationally predict such subtle effects for different substrate enantiomers, as well as to understand their origin and how they are affected by mutations, is an important advance towards the computational design of improved biocatalysts for enantioselective synthesis.

Supercritical carbon dioxide anchored highly dispersed silver nanoparticles on 4A-zeolite and selective oxidation of styrene performance

Abstract: We developed a facile and new method for the production of a 4A-zeolite supported silver nanoparticle (Ag NP) composite catalyst using supercritical carbon dioxide (scCO2). The small (3–6 nm) and highly dispersed silver nanoparticles were formed on the 4A-zeolite with the assistance of scCO2 and hydrogen reduction. The anchored Ag NPs are smaller in size and more uniform in distribution on the 4A-zeolite, and favor a wide range of physical and chemical properties. In order to test the properties of the synthesized composite catalyst, the selective oxidation of styrene was introduced into the experiment. The composite catalyst synthesized by this new method exhibited excellent catalytic properties in the selective oxidation reaction of styrene compared with previous reports. Furthermore, two kinds of important chemical product, styrene oxide (SO) and benzaldehyde (BZ), could be controlled selectively by changing the oxidants and solvents used.

Green Regio- and Enantioselective Aminolysis Catalyzed by Graphite and Graphene Oxide under Solvent-Free Conditions

Abstract: The ring-opening reactions of epoxides with amines were efficiently and regioselectively catalyzed by high-surface-area graphite and graphene oxide under metal-free and solvent-free conditions. For epoxides without aryl groups, catalytic activity was observed only for graphene oxide, and hence, the activity must have been due to its acidic groups. For styrene oxide, instead, graphite and graphene oxide exhibited rather similar catalytic activities, and hence, the activity was mainly due to activation of the electrophilic epoxide by π-stacking interactions with the graphitic π system. The described aminolysis procedure is green and cheap because the catalyst can be recovered and recycled without loss of efficiency. Moreover, these heterogeneous catalysts exert high stereoselective control in the presence of nonracemic epoxides and provide chiral β-amino alcohols with enantiomeric excess values up to 99 %.

Practical two-step synthesis of enantiopure styrene oxide through an optimized chemoenzymatic approach

Abstract: Enantiopure styrene oxide (SO) and its derivatives are important building blocks for chiral synthesis In this study, we developed an attractive “1-pot, 2-step” chemoenzymatic approach for producing enantiopure SO with 100 % theoretical yield This approach involved asymmetric reduction of α-chloroacetophenone by an alcohol dehydrogenase (ADH; step 1), followed by base-induced ring closure (epoxidation) of enantiopure 2-chloro-1-phenylethanol produced by the ADH (step 2) By-product formation during epoxidation was suppressed to <1 % by adding methyl tert-butyl ether (MTBE) as the second phase Therefore, with this optimized approach, ADH from Lactobacillus kefir (LkDH) successfully produced 1 M (S)-SO, with 99 % analytical yield and 978 % enantiomeric excess (ee) In the preparation of (R)-SO, a semi-rational strategy of active pocket iterative saturation mutagenesis (ISM) was successfully used to inverse the enantioselectivity of LkDH (muDH2, F147L/Y190P/A202F/M206H/V196L/S96D/K97V), which produced the opposite enantiomer (R)-2-chloro-1-phenylethanol Through the optimized chemoenzymatic approach, muDH2 was successfully used to prepare 1 M (R)-SO, with 981 % ee and 990 % analytical yield Our results indicated that this optimized chemoenzymatic approach could be used to produce both enantiomers of SO at concentrations as high as 120 g/L within 14 h, which is the highest concentration as far as we know MuDH2 obtained through ISM also showed reversed enantioselectivity toward another 13 aromatic ketones, compared with wild-type (WT) LkDH Furthermore, a molecular docking experiment demonstrated that muDH2 inverted the binding orientation of the substrate, which may be the reason for its inverse enantioselectivity

Looking inside the pores of a MCM-41 based Mo heterogeneous styrene oxidation catalyst: an inelastic neutron scattering study.

Abstract: Styrene oxidation mediated by a Mo-based mesoporous catalyst can yield selectively styrene oxide or benzaldehyde. Kinetic data evidenced that styrene oxide is the initial single-product formed by the catalytic Mo-mediated process. However, after some hours of reaction benzaldehyde yield rises while that of the epoxide decreases concomitantly. The mechanistic proposal pointed to a surface assisted acid–base mechanism by which styrene oxide is interconverted into benzaldehyde through over-oxidation and cleavage of the C–C bond and releases formaldehyde as well. In an attempt to gain some insight into whether this mechanistic proposal is realistic we have conducted a combined DRIFT and inelastic neutron scattering (INS) study to assess the adsorbed species at the catalyst's surface and confirm the mechanistic proposal. INS and DRIFT provided complementary insight into surface-adsorbed species by probing donor (INS) and acceptor (DRIFT) species. INS also allowed for an estimation of product selectivity by means of a Job method stressing the power of the technique.

Synthesis, structure and multifunctional catalytic properties of a Cu(I)-coordination polymer with outer-hanging CuBr2

Abstract: A 1D Cu(I)-coordination polymer [(CuL1)(CuBr2), 1] carrying external copper bromide moieties was synthesized. The outer-hanging [CuBr2]− moiety is attached to the 1D Cu(I)-CP backbone via a Cu⋯Cu bonding interaction, which makes it look like a coordination polymer supported CuBr2 species. 1 exhibits excellent multifunctional catalytic activity for phenol acetylation, A3-coupling (aldehyde–alkyne–amine) and styrene oxide methanolysis reactions. Its heterogeneous catalytic nature was confirmed by solution leaching experiment and it can be reused without significant loss of its catalytic activity and selectivity for the above reactions.

Chemical fixation of CO2 to cyclic carbonates using Al(III) β-aminoalcohol based efficient catalysts: An experimental and computational studies

Abstract: A series of Al(III) unsymmetrical β-aminoalcohol based complexes 1–6 were synthesized via metalation of the corresponding ligands 1′–6′ those were prepared by the reaction of benzylamine with readily available epoxides viz., styrene oxide, 1,2-epoxy-3-phenoxypropane, 4-tertbutylphenyl glycidyl ether, 4-chlorophenyl glycidyl ether, glycidyl 2-methylphenyl ether and 1,2-epoxyhexane. Among these complexes, the complex 2 was found to be most effective in the cycloaddition of aryloxy/aliphatic terminal epoxides with CO 2 under atmospheric pressure to get corresponding cyclic carbonates with high conversion and selectivity (up to >99%) in the presence of tetrabutylammonium bromide as a co-catalyst. The DFT calculations revealed the important role played by counter-ion in the co-catalyst during cycloaddition reaction of CO 2 with the substituted epoxides.

Hydrolytic Cleavage Products of Globin Adducts in Urine as Possible Biomarkers of Cumulative Dose: Proof of Concept Using Styrene Oxide as a Model Adduct-Forming Compound.

Abstract: A new experimental model was designed to study the fate of globin adducts with styrene 7,8-oxide (SO), a metabolic intermediate of styrene and a model electrophilic compound. Rat erythrocytes were incubated with SO at 7 or 22 °C. Levels of specific amino acid adducts in globin were determined by LC/MS analysis of the globin hydrolysate, and erythrocytes with known adduct content were administered intravenously to recipient rats. The course of adduct elimination from the rat blood was measured over the following 50 days. In the erythrocytes incubated at 22 °C, a rapid decline in the adduct levels on the first day post-transfusion followed by a slow phase of elimination was observed. In contrast, the adduct elimination in erythrocytes incubated at 7 °C was nearly linear, copying elimination of intact erythrocytes. In the urine of recipient rats, regioisomeric SO adducts at cysteine, valine, lysine, and histidine in the form of amino acid adducts and/or their acetylated metabolites as well as SO-dipeptide ad...