5161-29-5Relevant academic research and scientific papers
Styrene Production from Benzene and Ethylene Catalyzed by Palladium(II): Enhancement of Selectivity toward Styrene via Temperature-dependent Vinyl Ester Consumption
Jia, Xiaofan,Foley, Aisling M.,Liu, Chang,Vaughan, Benjamin A.,McKeown, Bradley A.,Zhang, Sen,Gunnoe, T. Brent
supporting information, p. 3532 - 3541 (2019/09/12)
Oxidative ethylene hydrophenylation catalyzed by palladium(II) acetate with Cu(II) oxidants to produce styrene generally suffers from low selectivity and/or low yield. Commonly observed side products include vinyl carboxylates and stilbene. In this Article, the selectivity for styrene formation by Pd(OAc)2 is studied as a function of reaction temperature, ethylene pressure, Br?nsted acid additive, Cu(II) oxidant amount, and oxygen pressure. Under optimized conditions, at high temperatures (180 °C) and low olefin pressure (20 psig), nearly quantitative yield (>95%) of styrene is produced based on the limiting reagent copper(II) pivalate. We propose the selectivity for styrene versus vinyl pivalate at 180 °C is due to a palladium-catalyzed conversion of benzene and in situ formed vinyl pivalate to styrene.
Mechanistic studies of single-step styrene production using a rhodium(I) catalyst
Vaughan, Benjamin A.,Khani, Sarah K.,Gary, J. Brannon,Kammert, James D.,Webster-Gardiner, Michael S.,McKeown, Bradley A.,Davis, Robert J.,Cundari, Thomas R.,Gunnoe, T. Brent
, p. 1485 - 1498 (2017/02/10)
The direct and single-step conversion of benzene, ethylene, and a Cu(II) oxidant to styrene using the Rh(I) catalyst (FlDAB)Rh(TFA)(η2-C2H4) [FlDAB = N,N′-bis(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene; TFA = trifluoroacetate] has been reported to give quantitative yields (with Cu(II) as the limiting reagent) and selectivity combined with turnover numbers >800. This report details mechanistic studies of this catalytic process using a combined experimental and computational approach. Examining catalysis with the complex (FlDAB)Rh(OAc)(η2-C2H4) shows that the reaction rate has a dependence on catalyst concentration between first- and half-order that varies with both temperature and ethylene concentration, a first-order dependence on ethylene concentration with saturation at higher concentrations of ethylene, and a zero-order dependence on the concentration of Cu(II) oxidant. The kinetic isotope effect was found to vary linearly with the order in (FlDAB)Rh(OAc)(η2-C2H4), exhibiting no KIE when [Rh] was in the half-order regime, and a kH/kD value of 6.7(6) when [Rh] was in the first-order regime. From these combined experimental and computational studies, competing pathways, which involve all monomeric Rh intermediates and a binuclear Rh intermediate in the other case, are proposed. (Chemical Equation Presented).
Novel anti-Markovnikov regioselectivity in the Wacker reaction of styrenes
Wright, Joseph A.,Gaunt, Matthew J.,Spencer, Jonathan B.
, p. 949 - 955 (2007/10/03)
The Wacker reaction is one of the longest known palladium-catalysed organic transformations, and in the vast majority of cases proceeds with Markovnikov regioselectivity. Palladium(II)-mediated oxidation of styrenes was examined and in the absence of reoxidants was found to proceed in an anti-Markovnikov sense, giving aldehydes. Studies on the mechanism of this unusual transformation were carried out, and indicate the possible involvement of a η4-palladium-styrene complex. With a heteropolyacid as the terminal oxidant, oxidation of styrene to give the anti-Markovnikov aldehyde as the major product was found to be catalytic.
Resonance Raman investigation on the interaction of styrene and 4-methyl styrene oligomers on sulphated titanium oxide
Noda,Sala
, p. 145 - 155 (2007/10/03)
In order to understand the nature of the interaction that gives rise to the yellow-orange colour observed when styrene or 4-methyl styrene are put in contact with sulphated TiO2, the resonance Raman spectra of such systems, including deuterated styrene (ring-deuterated d5 and perdeuterated d8) and allylbenzene were investigated. In all cases a substantial enhancement of the ring v(CC) stretching mode was observed. A charge transfer process involving a transition from the ring π-electrons to the empty d-π orbitals of titanium was ascribed responsible for the absorption in the visible. Two types of resonance Raman spectra were observed depending on the excitation wavelength, which can be explained by the presence of two kinds of oligomers, saturated and unsaturated, on the surface of the oxide with the former giving rise to a Raman enhancement at a higher excitation energy.
CONFORMATIONAL ORDER IN CRYSTALLINE STATES AND GELS OF ISOTACTIC, SYNDIOTACTIC AND ATACTIC POLYSTYRENES STUDIED BY VIBRATIONAL SPECTROSCOPY
Nakaoki, Takahiko,Kobayashi, Masamichi
, p. 315 - 331 (2007/10/02)
Stable conformations and their sequential order of isotactic (IPS), syndiotactic (SPS) and atactic polystyrenes (APS) in various aggregation states have been investigated by infrared (IR) spectroscopy, 13C NMR and X-ray diffraction.It has been demonstrated that the partially ordered skeletal conformation existing in IPS/CS2 gels of a (3/1) helix (TG) type having the pendant phenyl groups oriented in a disordered fashion, rather than the near-TT form proposed previously for IPS/decalin gels.The process of conformational change during gelation of IPS/CS2 and APS/CS2 systems has been followed by IR spectroscopy, and it has been concluded that the construction of regular sequences of a particular conformation promotes the gelation of both crystallizable and non-crystallizable polystyrenes.As-cast film specimens prepared from a chloroform solution are found to be a crystalline polymer-solvent complex (the γ phase) having a TTGG conformation.On heating, the γ phase transforms to a β phase at about 120 deg C, accompanied by removal of the solvent, while the TTGG conformation is retained.On further heating, the β phase transforms to an α1 or α2 phase at about 200 deg C accompanied by a change in conformation from TTGG to TT.The process of conformational change (in both type and sequence) during these phase transformations has been clarified by IR spectroscopy.
Metal-catalysed Alkyl Ketone to Ethyl Ketone Conversions in Chelating Ketones via Carbon-Carbon Bond Cleavage
Suggs, J. William,Jun, Chul-Ho
, p. 92 - 93 (2007/10/02)
8-Quinolinyl alkyl ketones, in which the alkyl group has β-hydrogens, react with various Rh(I) and Ir(I) complexes under ethylene to give, in a catalytic process, 8-quinolinyl ethyl ketone; the same reaction with 8-quinolinyl phenyl ketone produces styrene via ethylene insertion into a rhodium-phenyl bond and β-elimination of the resulting phenylethyl complex.
Gas Phase Reactions of Protonated 1,3-Diphenylpropyne and Some Isomeric + Ions
Baether, Wolfgang,Kuck, Dietmar,Gruetzmacher, Hans-Fr.
, p. 572 - 577 (2007/10/02)
Metastable (3-phenyl-2-propynyl)benzenium ions, generated by electron impact induced fragmentation from the appropriately substituted 1,4-dihydrobenzoic acid, react by loss of .CH3 and C6H6.The study of deuterated derivatives reveals that hydrogen/deuterium exchanges involving all hydrogen and deuterium atoms precede the fragmentations.The results suggest a skeletal rearrangement by electrophilic ring-closure reactions giving rise to protonated phenylindene and protonated 9,10-methano-9,10-dihydroanthracene prior to the elimination of C6H6 and .CH3, respectively.A study of isomeric + ions by collision-induced decomposition and by deuterium labelling shows that these ions interconvert by hydrogen migrations and skeletal rearrangements.
On the Electron Impact Induced Hydroxyl Loss from o-Nitrostyrene
Depke, Gisbert,Klose, Walter,Schwarz, Helmut,Blum, Wolfgang,Richter, Wilhelm J.
, p. 568 - 571 (2007/10/02)
Unimolecular hydroxyl (OD.) loss form regio- and stereo-specifically labelled o-nitrostyrenes 1a, 1c and 1d results in the formation of an ion which upon collisional activation gives identical mass spectra.Suggestions are made which aim at explaining: (i) the loss of stereochemical integrity of the diastereotopic methylene hydrogens in the course of hydroxyl elimination; and (ii) to account for the collision induced losses of CO and HCN from the (1+) ion.
