Showing papers on "Styrene oxide published in 2002"

Pilot-scale production of (S)-styrene oxide from styrene by recombinant Escherichia coli synthesizing styrene monooxygenase.

Abstract: Recombinant Escherichia coli JM101(pSPZ10) cells produce the styrene monooxygenase of Pseudomonas sp. strain VLB120, which catalyzes the oxidation of styrene to (S)-styrene oxide at an enantiomeric excess larger than 99%. This biocatalyst was used to produce 388 g of styrene oxide in a two-liquid phase 30-L fed-batch bioconversion. The average overall volumetric activity was 170 U per liter over a period of more than 10 h, equivalent to mass transfer rates of 10.2 mmoles per liter per hour at a phase ratio of 0.5. At this transfer rate, the biotransformation system appeared to be substrate mass-transfer limited. The reactor had an estimated power input in the order of 5 W · L−1, which is close to values typically obtained with commercially operating units. The product could be easily purified by fractional distillation to a purity in excess of 97%. The process illustrates the feasibility of recombinant whole cell biotransformations in two-liquid phase systems with toxic substrates and products. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 80: 33–41, 2002.

(Salen)chromium Complex Mediated Asymmetric Ring Opening of meso- and Racemic Epoxides with Different Fluoride Sources

Abstract: The asymmetric ring opening of five meso- and three racemic epoxides with different fluorinating reagents in the presence of stoichiometric or slightly sub-stoichiometric amounts of Jacobsen's enantiopure (salen)chromium chloride complex A gave the corresponding optically active vicinal fluorohydrins. Silver fluoride was used as one of the fluoride sources either in the presence of Bu4N+H2F3− in diethyl ether or in acetonitrile. The latter reactions starting from cyclohexene oxide (1) showed maximum 72% ee in the formed fluorohydrin 2 isolated in 90% yield. From other meso-epoxides such as cyclopentene oxide and cycloheptene oxide the corresponding fluorohydrins were isolated in 80% and 82% yield with 65% and 62% ee, respectively. In case of ring opening under similar conditions of the racemic styrene oxide or phenyl glycidyl ether 83% and 75% of the fluorohydrins with fluorine in the primary position were isolated with 74% ee and 65% ee, respectively. Tetrahydronaphthalene oxide yielded a 2:1 mixture of trans- (23% ee) and cis-2-fluoro-3,4-benzocyclohexenol (2% ee) suggesting competing SN2 and SN1 type ring openings. Other epoxides such as cyclooctene oxide, cis-stilbene oxide and α-methylstyrene oxide did not react or gave the fluorohydrins with very small enantiomeric excess.

Oxidative catalysis by Mn4O46+ cubane complexes

Abstract: The oxidation of a variety of substrates (thioethers, hydrocarbons, alkenes, benyzl alcohol and benzaldehyde) by t BuOOH catalyzed by Mn 4 O 4 (O 2 PPh 2 ) 6 ( 1 ) and Mn 4 O 4 (O 2 P( p -MePh) 2 ) 6 ( 2 ) is reported. These reactions illustrate the first examples of oxidative catalysis using a manganese-oxo complex with a Mn 4 O 4 cubane core. These uncharged complexes contain Mn ions in a mixed valence oxidation state, formally Mn 4 (2III, 2IV), and are bridged by bulky diphenylphosphinate chelates across each of the six faces of the cube. Using this system, methyl phenyl sulfide is selectively mono-oxygenated to methyl phenyl sulfoxide with high catalytic efficiency, and no evidence for further oxidation to the thermodynamically preferred sulfone. Toluene is oxidized to a mixture of benzyl alcohol, benzaldehyde, and benzoic acid with high catalytic efficiencies. Lower catalytic efficiencies are observed in the oxidation of styrene to a mixture of styrene oxide and benzaldehyde, of cyclohexene to a mixture of cyclohexene oxide, 2-cyclohexen-1-ol, and 2-cyclohexen-1-one, and of cyclohexane to a mixture of cyclohexanol and cyclohexanone. The observed product distribution from the oxidation of hydrocarbons has the characteristics of a free radical-based oxidation mechanism. However, the sulfoxidation and epoxidation activity of the 1 / t BuOOH system, as well as the observed steric preferences for less congested substrates, suggest that a metal-oxo centered oxidation mechanism is active in the reactions studied here. An intermediate species, characterized by a UV–VIS band centered at 610 nm is observed in all reaction mixtures, and forms upon reaction of 1 or 2 with t BuOOH . Preliminary evidence suggests this reactive intermediate may correspond to a Mn(V)O species. Kinetic studies suggest two pathways for oxidation: one involving an oxygen atom transfer (two-electron branch), and the other involving a hydrogen atom abstraction (one-electron branch).

Micellization and gelation of triblock copolymers of ethylene oxide and styrene oxide in aqueous solution

Abstract: Nine triblock copolymers of ethylene oxide and styrene oxide (type EmSnEm, E = oxyethylene, S = oxyphenylethylene, n and m = number-average block lengths) were prepared by sequential oxyanionic polymerization. Surface tensiometry was used to determine critical micelle concentrations (cmc's) and standard enthalpies of micellization, and isothermal titration calorimetry was used to confirm the enthalpy of micellization. Light scattering was used to determine micellar association numbers and hydrodynamic radii. Phase diagrams defining regions of hard and soft gel were determined by tube inversion and Couette rheometry. Comparison is made with reported results for diblock copolymers of ethylene oxide and styrene oxide and, so far as possible, with results for triblock copolymers of ethylene oxide and styrene. Compilation of values of the cmc for three series of triblock copoly(oxyalkylene)s, EmSnEm, EmBnEm (B = oxybutylene), and EmPnEm (P = oxypropylene), reveals a discontinuity in the block length dependence of log(cmc) at S6 and B12.

Detection of Chemically‐Induced Damage in Layered DNA Films with Co(bpy)33+ by Square‐Wave Voltammetry

Abstract: Damage of double stranded (ds) DNA by metabolites of lipophilic pollutants and drugs constitutes a major toxicity pathway. We evaluated films of DNA and poly(dimethyldiallylammonium chloride) (PDDA) grown layer-by-layer on pyrolytic graphite electrodes for the detection of DNA damage by the model metabolite styrene oxide, which forms chemical adducts with DNA bases. The method features electroactive probe Co(bpy)33+, which binds to films with DNA as the outer layer [(PDDA/ds-DNA)2] in greater amounts when the ds-DNA is intact than when it is damaged. Square-wave voltammetry peaks of Co(bpy)33+ decreased with incubation time of (PDDA/DNA)2 electrodes in styrene oxide solutions, while no changes in the peaks were found for control incubations with non-reactive toluene. Comparison with capillary electrophoretic analyses suggested that this voltammetric method can detect roughly 0.05% damage. The presence of hemoprotein in the films did not interfere with the analysis. The method appears promising for the rapid detection of relative rates of DNA damage by human liver metabolites.

Isomerization of Styrene Epoxide on Basic Solids

Abstract: The isomerization of styrene oxide has been investigated on mixed oxides obtained by calcination of hydrotalcites, rare earth phosphates and KF supported on alumina All solids form β-phenylacetaldehyde Basic catalysts deactivate rapidly or show a lower selectivity, most probably due to the formation of heavy products by aldolisation ZnAl catalyst shows a selectivity towards β-phenylacetaldehyde >98% with no deactivation after 7 h on stream, in a flow gas phase process at 423 K

Simultaneous production of chirally enriched epoxides and 1,2-diols from racemic epoxides via hydrolytic kinetic resolution (HKR)

Abstract: Hydrolytic kinetic resolution (HKR) of racemic epichlorohydrin, styrene oxide and propene oxide was investigated using dimeric homochiral Co(III) Schiff base complex derived from mono-tartrate salt of (1R,2R)-(−)-cyclohexane diamine with 3,5-di-tert-butyl salicylaldehyde and 5,5-methylene-di-3-tert-butyl salicylaldehyde with an objective to get high efficiency and recycling capability of the catalyst. Excellent conversions to enantiomerically pure epoxide and diols along with high chiral induction were obtained in all the cases. With a loading <0.3 mol% of the catalyst, the system works well up to three cycles without any loss in activity and selectivity.

Electrochemical and Catalytic Properties of Novel Manganese(III) Complexes with Substituted 2‐(2′‐Hydroxyphenyl)oxazoline Ligands − X‐ray Structures of Tris[5‐methyl‐2‐(2′‐oxazolinyl)phenolato]manganese(III) and Tris[5‐chloro‐2‐(2′‐oxazolinyl)phenolato]manganese(III)

Abstract: A series of manganese complexes of the type MnL3 were synthesised and characterised, with HL being (substituted) 2-(2′-hydroxyphenyl)oxazoline ligands. The molecular structures of [Mn(5′-Mephox)3] and [Mn(5′-Clphox)3] reveal their meridional configuration with a significant Jahn−Teller distortion. The ligand substituents exert a significant influence on the redox and catalytic properties of the manganese complexes. Cyclic voltammetry experiments show that the electrochemically quasi-reversible MnII/MnIII and reversible MnIII/MnIV redox couples shift towards higher potentials with more electron-withdrawing substituents. The same trend applies for the oxidation of the manganese(IV) complexes. Electrolysis experiments monitored with UV/Vis and EPR spectroscopy revealed that the reduction of the manganese(III) complexes to manganese(II), and their oxidation to manganese(IV) are both chemically reversible, while subsequent oxidation of the manganese(IV) species was found to be irreversible. All complexes are active oxidation catalysts with dihydrogen peroxide as the oxidant. In the oxidation of styrene, up to 220 turnover numbers were obtained towards styrene oxide. The turnover numbers in the oxidation reactions as well as the selectivity in the oxidation of styrene and cis-stilbene are affected significantly by the substituents, but no clear correlation with the electrochemical properties was observed. The most striking substituent effect is the higher stability of [Mn(5′-NO2phox)3] compared to the other complexes during styrene oxidation with dihydrogen peroxide in methanol.

Structural analysis of styrene oxide/haemoglobin adducts by mass spectrometry: identification of suitable biomarkers for human exposure evaluation.

Abstract: The structural characterisation of adducts formed by the in vitro reaction of haemoglobin (Hb) with styrene oxide (SO), the most reactive metabolite of the industrial reagent styrene, was obtained by liquid chromatography/electrospray ionisation mass spectrometry (LC/ES-MS) analysis of modified tryptic peptides of human Hb chains. The reactive sites of human Hb towards SO were identified through characterisation of alkylated tryptic peptides by matrix-assisted laser desorption/ionisation with tandem mass spectrometry (MALDI-MS/MS). A procedure was set up based on this characterisation, allowing Hb modification to be assessed by monitoring SO/Hb adducts using HPLC with selected ion recording (SIR) mass spectrometry. By this methodology it was also possible to compare advantages and disadvantages of presently available strategies for the measurement of Hb adducts with SO. The results obtained could most plausibly lead to the optimisation of molecular dosimetry of SO adducts, and the analytical procedure described herein could be applied to the biological monitoring of styrene exposure in the workplace.

Manganese Oxidation Catalysts with 2-(2'-Hydroxyphenyl)oxazoline Ligands: Catalyst Intermediates and Degradation Products - Crystal Structure of Bis[{2,(2'-oxazolinyl)phenolato}bis(1-methylimidazole)manganese(III)] Perchlorate.

Abstract: Manganese complexes with phox ligands [Hphox = 2-(2′-hydroxyphenyl)oxazoline] act as oxidation catalysts with dihydrogen peroxide. Their catalytic efficiency is strongly affected by the presence of a base, such as 1-methylimidazole (1-Meim). The crystal structure of an Mn−phox complex with two axial 1-Meim ligands, [Mn(phox)2(1-Meim)2](ClO4), is reported. The [Mn(phox)2]+ and [Mn(phox)2(1-Meim)]+ species have been detected in catalytic reaction mixtures by electrospray mass spectrometry. In the catalytic oxidation of styrene, turnover numbers of 428 and 456 have been obtained for styrene oxide in the presence of [Mn(phox)3] and of [Mn(5′-NO2phox)3], respectively. During these reactions, catalyst degradation occurs, and is the main obstacle to obtaining higher turnover numbers. GC-MS analysis of the degradation products of [Mn(5′-Clphox)3] after catalytic reactions indicates that the oxazoline group is decomposed. The same decomposition products are also observed with electrospray mass spectrometry at higher ionisation potentials. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Microwave Induced Reaction of H-Dimethylphosphonate with Styrene Oxide

Abstract: Microwave catalyzed reaction of a neat mixture of styrene oxide and H-dimethylphosphonate furnished dimethyl methylphosphonate, trimethylphosphate, phenylacetaldehyde, 1-methoxy-2-phenylethanol, 1-phenylethleneglycol, cis- and trans-1,3-diphenylcyclobutanes, hydrogen 1-(2-phenylethyl)methylphosphinate, (1-phenylethyl)dimethylphosphonate, and (1-phenylethyl)dimethylphosphonate via free radical processes.

Observations on the origin of phenylacetaldehyde in styrene epoxidation and the mechanism of oxidations catalysed by manganese complexes of porphyrins

Abstract: Phenylacetaldehyde (PhA) has been observed as a by-product in H2O2 metalloporphyrin catalytic oxidation of styrene. We have found that the mechanism of these oxidations depends on the relative amount of the carboxylic acid that is used as co-catalyst. With an excess of the organic acid less PhA is formed due to the intervention of metalloacylperoxo species (1) instead of a metallo-oxo species (2). Whatever the conditions used, the PhA which is formed comes chiefly from styrene oxide (SO) isomerization. This process seems to be due to the presence of oxygen centered radicals formed through metalloporphyrin reaction with hydrogen peroxide.

Enantioselective Hydrolyses with Yarrowia lipolytica: A Versatile Strain for Esters, Enol Esters, Epoxides, and Lactones.

Abstract: Racemic secondary esters 1 – 3 , γ-lactones 8 – 9 , and styrene oxide 7 are kinetically resolved via hydrolysis with Yarrowia lipolytica YL2 strain. The enantioselective hydrolysis of prochiral enol esters 4 – 6 to the corresponding homochiral carbonyl compounds 13 – 15 is also described. Subsequent reduction of the ketone 13 and of the aldehyde 15 can be avoided using lyophilised cells.

(Salen)chromium Complex Mediated Asymmetric Ring Opening of meso- and Racemic Epoxides with Different Fluoride Sources.

Abstract: The asymmetric ring opening of five meso- and three racemic epoxides with different fluorinating reagents in the presence of stoichiometric or slightly sub-stoichiometric amounts of Jacobsen's enantiopure (salen)chromium chloride complex A gave the corresponding optically active vicinal fluorohydrins. Silver fluoride was used as one of the fluoride sources either in the presence of Bu4N+H2F3− in diethyl ether or in acetonitrile. The latter reactions starting from cyclohexene oxide (1) showed maximum 72% ee in the formed fluorohydrin 2 isolated in 90% yield. From other meso-epoxides such as cyclopentene oxide and cycloheptene oxide the corresponding fluorohydrins were isolated in 80% and 82% yield with 65% and 62% ee, respectively. In case of ring opening under similar conditions of the racemic styrene oxide or phenyl glycidyl ether 83% and 75% of the fluorohydrins with fluorine in the primary position were isolated with 74% ee and 65% ee, respectively. Tetrahydronaphthalene oxide yielded a 2:1 mixture of trans- (23% ee) and cis-2-fluoro-3,4-benzocyclohexenol (2% ee) suggesting competing SN2 and SN1 type ring openings. Other epoxides such as cyclooctene oxide, cis-stilbene oxide and α-methylstyrene oxide did not react or gave the fluorohydrins with very small enantiomeric excess.

Oxiranyl Anion Mediated Synthesis of Highly Enantiomerically Enriched Styrene Oxide Derivatives.

Abstract: [reaction: see text] The stereospecific alpha-lithiation of optically active styrene oxides and the trapping reaction of the corresponding highly reactive intermediates with electrophiles to produce optically active styrene oxide derivatives are described. This methodology has been applied to the synthesis of an optically active oral antifungal agent of industrial interest.

New copolymer based on alkylene oxide and styrene oxide, useful as pigment and bitumen emulsifier and as anionic or non-ionic emulsifier in emulsion polymerization

Abstract: A copolymer of given formula (based on alkylene oxide and styrene oxide) containing 1-5C alkyl or 2-5 alkenyl residues, obtainable from a hetero atom, and containing an acid group or aliphatic or aromatic 1-50C hydrocarbon carrying an acid group is new. A copolymer of formula (1): asteriskasterisk(structure I, page 13): asteriskasterisk(structure (2), page 13) R1 = H,1-5C alkyl or 2-5C alkenyl obtainable from a hetero atom, and containing an acid group or aliphatic or aromatic 1-50C hydrocarbon carrying an acid group; R2 and R3 = H, Me, and/or Et, n = 0-100, m = 3-30, k = 1-200, A = H, an acid group, 1-5C alkyl or 2-8C alkenyl, which can be obtained from a hetero atom, and containing a 1-50C aliphatic or aromatic group carrying an acid group, or a copolymer unit of formula (2). R4 = H, 1-5C alkyl or 2-5C alkenyl, which can be obtained from a hetero atom, and containing an acid group or a 1-50C aliphatic or aromatic hydrocarbon carrying an acid group, R5 = H, Me, Et, x = 0-100, y = 3-30, A corresponds to formula (2), R1 = H or an acid group.

Highly Efficient Asymmetric Epoxidation of Alkenes with a D4-Symmetric Chiral Dichlororuthenium(IV) Porphyrin Catalyst.

Abstract: A dichlororuthenium(IV) complex of 5,10,15,20-tetrakis[(1S,4R,5R,8S)-1,2,3,4,5,6,7,8-octahydro-1,2:5,8-dimethanoanthrance-9-yl]porphyrin, [Ru(IV)(D(4)-Por)Cl(2)] (1), was prepared by heating [Ru(II)(D(4)-Por)(CO)(MeOH)] (2) in refluxing CCl(4). Complex 1 is characterized by (1)H NMR (paramagnetically shifted pyrrolic protons at delta(H) = -52.3 ppm), FAB-mass spectroscopies, and magnetic susceptibility measurement (mu(eff) = 3.1 mu(B)). The ruthenium complex exhibits remarkable catalytic activity toward enantioselective alkene epoxidation using 2,6-dichloropyridine N-oxide (Cl(2)pyNO) as terminal oxidant. The Ru(IV)-catalyzed styrene epoxidation is achieved within 2 h (versus 48 h for the 2-catalyzed reaction), and optically active styrene oxide was obtained in 69% ee and 84% yield (875 turnovers). Likewise, substituted styrenes and some conjugated cis-disubstituted alkenes (e.g., cis-beta-methylstyrene, cis-1-phenyl-3-penten-1-yne, 1,2-dihydronaphthalene, and 2,2-dimethylchromenes) are converted effectively to their organic epoxides in 50-80% ee under the Ru(IV)-catalyzed conditions, and more than 850 turnovers of epoxides have been attained. When subjecting 1 to four repetitive uses by recharging the reaction mixture with Cl(2)pyNO and styrene, styrene oxide was obtained in a total of 2190 turnovers and 69% ee. UV-vis and ESI-mass spectral analysis of the final reaction mixture revealed that a ruthenium-carbonyl species could have been formed during the catalytic reaction, leading to the apparent catalyst deactivation. We prepared a heterogeneous chiral ruthenium porphyrin catalyst by immobilizing 1 into sol-gel matrix. The heterogeneous catalyst is highly active toward asymmetric styrene epoxidation producing styrene oxide in 69% ee with up to 10,800 turnovers being achieved. The loss of activity of the Ru/sol-gel catalyst is ascribed to catalyst leaching and/or deactivation. On the basis of Hammett correlation (rho(+) = -1.62, R = 0.99) and product analysis, a dioxoruthenium(VI) porphyrin intermediate is not favored.

Fe-MCM-41 for Selective Epoxidation of Styrene with Hydrogen Peroxide.

Abstract: Fe-MCM-41 prepared by direct hydrothermal synthesis catalyzes the epoxidation of styrene with diluted H2O2. The selectivity to styrene oxide reached 67% at styrene conversion of 17% over the catalyst with Si/Fe ratio of 86, which is better than that obtained over TS-1 or a titanium-incorporated silica.