Catalytic Epoxidation Of Styrene Research Articles

Catalytic epoxidation of olefins by polymer-anchored amino acid ruthenium complexes

A synthetic strategy was developed to anchor an amino acid l-valine on to styrene–divinylbenzene co-polymer beads with 8% and 6% cross linking. The polymeric ligands containing bidentate N,O donor sites were treated with a solution of ruthenium(III) chloride to form the metal complex on the support. These immobilized Ru(III) complexes were characterized by elemental analysis, FT-IR, UV–visible diffuse reflectance, ESR, SEM and thermal analysis. The catalytic epoxidation of styrene, norbornylene, cyclooctene, and cyclohexene were investigated using the supported catalysts in the presence of tert.-butyl hydroperoxide as the terminal oxidant. Selective epoxide formation was observed with norbornylene and cis-cyclooctene whereas in the case of styrene the corresponding epoxide, benzaldehyde and acetophenone were obtained. Amongst the olefins screened, good activity was observed in the case of cyclohexene. The effect of various reaction parameters as well as some aspects of catalyst recycling and possible mechanistic pathways has also been investigated.

Structural, magnetic and catalytic properties of a self-recognized mu-oxo-bridged diiron(III) bis(benzimidazole) complex.

The inherent nonplanarity and C(2) symmetry of the dimethyl-substituted bis(benzimidazole) ligand (Me(2)BBZ) results in two distinct atropisomers that, when separated, have been suggested to have potential for chiral recognition and catalysis. Here is reported the synthesis and characterization of a diiron mu-oxo-bridged bis(benzimidazole) complex, 1, that provides indirect support for this hypothesis. Dimerization of a racemic solution of iron-Me(2)BBZ monomers via the mu-oxo bridge yields (+,+) and (-,-) diastereomers whose complementary association can be attributed to the inherent sidedness of the metal-Me(2)BBZ interaction surface, and to the differences in the torsional angles of the phenyl(benzimidazole) units (34 degrees) and the Schiff base linkages (54 degrees). These results highlight the steric differences between the phenyl(benzimidazole) and Schiff-base portions of the ligand, features that could be important in the chiral recognition of ligands and in differentiating substrate trajectories as required for asymmetric catalysis. For completeness, studies of 1 in the catalytic epoxidation of styrene are also reported.

Catalytic epoxidation of styrene over copper hydroxyphosphate Cu2(OH)PO4

Catalytic epoxidation of styrene with hydrogen peroxide over copper hydroxyphosphate Cu2(OH)PO4 was studied. Catalytic data shows that the catalyst Cu2(OH)PO4 is very active, and the main products are styrene epoxide and benzaldehyde, particlularly giving high selectivity for styrene epoxide. In contrast, over TS-1 a large amount of phenylacetaldehyde product is formed. Some important factors associated with the catalytic activity and selectivity are investigated extensively.

Catalytic Epoxidation of Styrene by Molecular Oxygen over a Novel Catalyst of Copper Hydroxyphosphate Cu2(OH)PO4

Catalytic epoxidation of styrene by molecular oxygen over a novel copper hydroxyphosphate catalyst, Cu2(OH)PO4, was studied. Catalytic data show that the catalyst Cu2(OH)PO4 is very active, and the main products are benzaldehyde and styrene epoxide. Some important factors associated with the catalytic activity and selectivity have been investigated extensively.

Catalytic epoxidation of styrene with molecular oxygen in a flow cell with a manganese porphyrin-modified graphite felt cathode

Abstract Epoxidation of styrene with molecular oxygen was achieved using electrochemically reduced manganese porphyrins on chemically modified electrodes in a flow cell. It was possible to recycle the solution through the flow cell and the yield in styrene oxide increased after each electrolysis. © 2000 Academie des sciences / Editions scientifiques et medicales Elsevier SAS

Chiral oxazoline ligands. Synthesis and characterization of palladium, nickel and manganese complexes containing bidentate N,O and N,P moieties †

Complexes of palladium, nickel and manganese, with the chiral ligand (+)-(4′R)-2-(4′-ethyl-3′,4′-dihydrooxazol-2′-yl)phenol HLOH were synthesized and characterized by 1H, 31P NMR spectroscopy, magnetic susceptibility and including the crystal structure determinations of trans-[PdLOH2] and [PdClLOH(PPh3)]. The LOH moiety is co-ordinated in a bidentate fashion in neutral, cationic and anionic complexes, rigid on the NMR time-scale. Monodentate O-co-ordinated complexes were obtained only in the presence of phosphines. The manganese complex [MnClLOH2] showed little activity in the catalytic epoxidation of styrene. The first phosphinite oxazoline ligand LOP was synthesized from HLOH. Neutral and cationic alkyl and allyl complexes of palladium with it were obtained and characterized. The cationic complexes showed dynamic behaviour.

Catalytic antibodies. Circular dichroism and UV-vis studies of antibody-metalloporphyrin interactions

Circular dichroism and UV-vis measurements were used to study the interaction between several water-soluble metalloporphyrins and monoclonal antibodies (MABs) that were elicited against a structurally related dihydroxytin(IV) porphyrin, la. Some of the MAB-metalloporphyrin complexes studied were previously shown to mimic hemoprotein-like activity, such as catalytic epoxidation of styrene by iodosobenzene. MAB-metalloporphyrin complex formation is usually accompanied by significant bathochromic shift and hypo-/hyperchromicity changes of the absorption maxima in the porphyrin Soret band region. Induced CD spectra in the same region (350-450 nm) are detected upon complex formation. They follow Beer’s law, exhibit isosbestic behavior, and show no significant change in the general shape of the Cotton effect as a function of the antibody:porphyrin ratio. Signal intensity (ellipticity) increases with increasing antibody:metalloporphyrin ratio, reaching an upper limit that represents saturation complexation, all indicating a specific 1:l binding phenomenon. Strong dependence of both signal shape and signal intensity upon the specific metal and antibody were observed, suggesting that induced CD may serve as a powerful tool for the unequivocal differentiation of two seemingly identical MAB clones. In cases of intense induced CD signals, it is possible to obtain MAB-metalloporphyrin dissociation constants using a titration curve where ellipticity is measured as a function of the antibody:porphyrin ratio and presented as a Scatchard plot. Both the UV-vis absorbance and induced CD spectrum of the metalloporphyrin-MAB complex remain unchanged over a broad pH range between 6 and 11, indicating remarkable stability of these complexes and reflecting the dominant role of electrostatic interactions between the hapten carboxylate groups and the antibody combining site.