1,721,065 research outputs found
ON THE MECHANISM OF THE PLATINUM(0)-ACID CATALYZED HYDROGENATION OF ALKENES
No full textThe hydrogenation of styrene promoted by the system [Pt(C2H4)(DPPB)]/acid is strongly affected by the nature of the solvent, the nature of the acid co-catalyst and the Pt/acid molar ratio. The highest catalytic activity is obtained in toluene working with methanesulfonic acid at a Pt/acid ratio = 1 The influence of the temperature and the hydrogen pressure on the catalytic activity has also been studied. The results indicate that at least two different catalytic systems operate. One of these accounts for the catalysis in the temperature range 25-35°C, while the other one is effective above 35°C. The catalytic activity of some model compounds has been also studied. 31P-NMR spectroscopy demonstrates that the complexes [Pt{CH(CH3)(C6H5)}(CH3SO3)(DPPB)] and [Pt(CH3SO3)2(DPPB)] are present in the low-temperature catalytic cycle. © 1994
New heteroscorpionate lanthanide complexes for ring-opening polymerisation of ε-caprolactone and rac-lactide
No full textYttrium and lanthanum amido-complexes with bis(pyrazol-1-yl) acetates in their coordination spheres were studied as the catalysts in epsilon-caprolactone and lactide ring-opening polymerisation. A high molecular mass poly(epsilon-caprolactone) (PCL) was obtained in almost quantitative yield under mild conditions. rac-Lactide polymerisations were less efficient and required quite harsh experimental conditions to obtain atactic PLA samples with moderate yields. The average chain-length of PCL was dependent upon the choice of the metal centre and the presence of substituents on the pyrazole rings of the ancillary ligand. The ground-state geometries of the complexes and the first stages of epsilon-caprolactone polymerisation were computationally modelled by means of DFT calculations
A NEW PLATINUM-BASED CATALYST SYSTEM FOR OLEFIN ASYMMETRIC HOMOGENEOUS HYDROFORMYLATION
No full textThe complex [Pt(C2H4)((+)-DIOP)] interacts with [PtCl2((+)-DIOP)] to give catalysts active in hydroformylation of styrene and 1-hexene. The activities of these systems depend upon the molar ratio of the two platinum complexes and the nature of the substrate. The systems display good chemioselectivity and induce asymmetry in the branched aldehydes formed. 2-Phenylpropanal can be isolated in ∼ 27% optical purity from hydroformylation of styrene. © 1990
Synthesis of dendritic polypyridines with ethoxycarbonyl groups as surface functionality
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The Pt(II)-SnCl2 catalyzed hydromethoxycarbonylation of 1-alkynes: a remarkable example of regioselectivity control
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The asymmetric hydrogenation of 1,1,4,4,7-pentamethyl-2-methylen-1,2,3,4-tetrahydro-naphthalene, a viable catalytic approach to the synthesis of non-racemic Fixolide®
No full textEnantioselective transition-metal catalysis in fragrance chemistry: a new synthesis of Galaxolide
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