111-67-1Relevant articles and documents
Olefin isomerization by iridium pincer catalysts. experimental evidence for an η3-allyl pathway and an unconventional mechanism predicted by DFT calculations
Biswas, Soumik,Huang, Zheng,Choliy, Yuriy,Wang, David Y.,Brookhart, Maurice,Krogh-Jespersen, Karsten,Goldman, Alan S.
, p. 13276 - 13295 (2012)
The isomerization of olefins by complexes of the pincer-ligated iridium species (tBuPCP)Ir (tBuPCP = κ3-C 6H3-2,6-(CH2PtBu2) 2) and (tBuPOCOP)Ir (tBuPOCOP = κ3-C6H3-2,6-(OPtBu 2)2) has been investigated by computational and experimental methods. The corresponding dihydrides, (pincer)IrH2, are known to hydrogenate olefins via initial Ir-H addition across the double bond. Such an addition is also the initial step in the mechanism most widely proposed for olefin isomerization (the "hydride addition pathway"); however, the results of kinetics experiments and DFT calculations (using both M06 and PBE functionals) indicate that this is not the operative pathway for isomerization in this case. Instead, (pincer)Ir(η2-olefin) species undergo isomerization via the formation of (pincer)Ir(η3-allyl)(H) intermediates; one example of such a species, (tBuPOCOP) Ir(η3-propenyl)(H), was independently generated, spectroscopically characterized, and observed to convert to ( tBuPOCOP)Ir(η2-propene). Surprisingly, the DFT calculations indicate that the conversion of the η2-olefin complex to the η3-allyl hydride takes place via initial dissociation of the Ir-olefin π-bond to give a σ-complex of the allylic C-H bond; this intermediate then undergoes C-H bond oxidative cleavage to give an iridium η1-allyl hydride which "closes" to give the η3-allyl hydride. Subsequently, the η3-allyl group "opens" in the opposite sense to give a new η1-allyl (thus completing what is formally a 1,3 shift of Ir), which undergoes C-H elimination and π-coordination to give a coordinated olefin that has undergone double-bond migration.
Activation of tetrabutylammonium hydrogen difluoride with pyridine: A mild and efficient procedure for nucleophilic fluorination
Moughamir, Khadija,Atmani, Aziz,Mestdagh, Helene,Rolando, Christian,Francesch, Charlette
, p. 7305 - 7306 (1998)
The nucleophilic fluorination of alkyl iodides, bromides and tosylates and of α-bromo- or α-chloroketones is smoothly effected by tetrabutylammonium hydrogen difluoride in the presence of pyridine, in dioxane or THF, with good or satisfying substitution-to-elimination ratio.
Mechanism of the Zr-Catalyzed Carboalumination of Alkynes. Evidence for Direct Carboalumination
Yoshida, Tadao,Negishi, Ei-ichi
, p. 4985 - 4987 (1981)
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Synthesis of the deuterated sex pheromone components of the grape borer, xylotrechus pyrrhoderus
Kiyota, Ryutaro,Yamakawa, Rei,Iwabuchi, Kikuo,Hoshino, Keita,Ando, Tetsu
, p. 2252 - 2256 (2009)
Adult males of the grape borer, Xylotrechus pyrrho- derus, secrete (S)-2-hydroxy-3-octanone [(S)-1] and (2S,3S)-2,3-octanediol [(2S,3S)-2] from their nota of prothoraces as sex pheromone components. Their structural similarity suggests that one of them is the biosynthetic precursor of the other component. In order to confirm the biochemical conversion, deuterated derivatives of both components were synthesized by starting from a Wittig reaction between hexanal and an ylide derived from D5-iodoethane and ending with enantiomeric resolution by chiral HPLC. The molecular ions of 1 and 2 could scarcely be detected by using a GC- MS analysis, and the labeled compounds showed similar mass spectra to the unlabeled pheromone components. However, several fragment ions, including four deuterium atoms, were observed in the mass spectra of their acetate derivatives, indicating that the conversion could be confirmed by examining a compound with the diagnostic ions after acetylation of the volatiles collected from insects treated with the labeled precursors.
Hydroformylation in fluorous solvents
Foster, Douglas F.,Adams, Dave J.,Gudmunsen, David,Stuart, Alison M.,Hope, Eric G.,Hamilton, David J.
, p. 722 - 723 (2002)
Triaryl-phosphines and -phosphites bearing fluorous ponytails give high rates, good linear selectivity and good retention of catalyst in the fluorous phase during hydroformylation of alkenes in fluorous solvents.
Comparative Dimerization of 1-Butene mith a Variety of Metal Catalysts, and the Investigation of a New Catalyst for C-H Bond Activation
Small, Brooke L.,Schmidt, Roland
, p. 1014 - 1020 (2004)
Catalytic dimerization of 1-butene by a variety of catalysts is carried out, and the products are analyzed by gas chromatography and mass spectrometry. Catalysts based on cobalt and iron can produce highly linear dimers, with the cobalt-based dimers exceeding 97% linearity. Catalysts based on vanadium and aluminum prefer to make branched dimers, which are most often methyl-heptenes in the case of vanadium and almost exclusively 2-ethyl-1-butene in the case of aluminum. The vanadium catalyst also produces substantial amounts of dienes and alkanes, suggesting a competing hydrogenation/dehydrogenation pathway that appears to involve vinyl C-H bond activation. Nickel catalysts are generally less selective than those based on iron or cobalt for making linear dimers, but they can make dimers with 60% linearity. The major by-products for the nickel systems are trisubstituted internal olefins. An important side reaction that must be considered for dimerization reactions is 1-butene isomerization to 2-butene, which makes recycling the butene difficult for a linear dimerization process. Aluminum, iron, and vanadium systems promote very little isomerization, but nickel and cobalt systems tend to isomerize the undimerized substrate heavily.
Retaining catalyst performance at high temperature: The use of a tetraphosphine ligand in the highly regioselective hydroformylation of terminal olefins
Yan, Yongjun,Zhang, Xiaowei,Zhang, Xumu
, p. 1582 - 1586 (2007)
A new tetraphosphine ligand has been developed and applied in the highly regioselective hydroformylation of terminal olefins. The ligand retains high performance at high temperature when compared with its bisphosphine analogue.
Platinum Catalysis Revisited-Unraveling Principles of Catalytic Olefin Hydrosilylation
Meister, Teresa K.,Riener, Korbinian,Gigler, Peter,Stohrer, Jürgen,Herrmann, Wolfgang A.,Kühn, Fritz E.
, p. 1274 - 1284 (2016)
Hydrosilylation of C-C multiple bonds is one of the most important applications of homogeneous catalysis in industry. The reaction is characterized by its atom-efficiency, broad substrate scope, and widespread application. To date, industry still relies on highly active platinum-based systems that were developed over half a century ago. Despite the rapid evolution of vast synthetic applications, the development of a fundamental understanding of the catalytic reaction pathway has been difficult and slow, particularly for the industrially highly relevant Karstedt's catalyst. A detailed mechanistic study unraveling several new aspects of platinum-catalyzed hydrosilylation using Karstedt's catalyst as platinum source is presented in this work. A combination of 2H-labeling experiments, 195Pt NMR studies, and an in-depth kinetic study provides the basis for a further development of the well-established Chalk-Harrod mechanism. It is concluded that the coordination strength of the olefin exerts a decisive effect on the kinetics of the reaction. In addition, it is demonstrated how distinct structural features of the active catalyst species can be derived from kinetic data. A primary kinetic isotope effect as well as a characteristic product distribution in deuterium-labeling experiments lead to the conclusion that the rate-limiting step of platinum-catalyzed hydrosilylation is in fact the insertion of the olefin into the Pt-H bond rather than reductive elimination of the product in the olefin/silane combinations studied.
Et3n .2Hf, a new convenient reagent for nucleophilic fluorine displacement reactions
Giudicelli,Pica,Veyron
, p. 6527 - 6530 (1990)
Syntheses of fluoro compounds by nucleophilic substitution of bromides or methane sulfonates using Et3N .2HF as the reagent are reported. The formation of undesired elimination side products is limited. The synthesis of this new fluorinating reagent is also reported.
An insight into copper catalyzed allylation of alkyl zinc halides. Comparison of reactivity profiles for catalytic and stoichiometric alkylzinc-copper reagents
Erdik, Ender,Ko?o?lu, Melike
, p. 1890 - 1897 (2009)
The γ-selective allylation of catalytic and stoichiometric alkylzinc-cuprates have been kinetically studied. The reactivity profiles generated by allylation reactions of n-butylzinc chloride catalyzed by CuX compounds (X = I, Br, Cl, CN, SCN) and also cat
ALDEHYDE GENERATION VIA ALKENE HYDROFORMYLATION
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Paragraph 0035; 0079-0081, (2021/09/26)
Aldehyde generation includes providing a first input stream, a second input, and an alkene substrate to a reactor system. The first input stream includes a catalyst, a ligand, and an organic solvent. The second input stream includes a mixture of carbon monoxide (CO) and hydrogen gas (H2). The alkene substrate is in either gaseous form or liquid form, the liquid form of the alkene substrate being provided with the first input stream, the gaseous form of the alkene substrate being provided with the second input stream. The reactor system includes a first reactor and a second reactor, where the second reactor is gas permeable and positioned within the first reactor.
Photocatalytic-controlled olefin isomerization over WO3–x using low-energy photons up to 625 nm
Sun, Xichen,Waclawik, Eric R.,Wang, Yunwei,Zhang, Jin,Zheng, Zhanfeng,Zhu, Pengqi
, p. 1641 - 1647 (2021/06/28)
WO3–x (W-1) was used to achieve controllable photoisomerization of linear olefins without substituents under 625 nm light irradiation. Thermodynamic and kinetic isomers were obtained by regulating the carbon chain length of the olefins. Terminal olefins were converted into isomerized products, and the internal olefin mixtures present in petroleum derivatives were transformed into valuable pure olefin products. Oxygen vacancies (OVs) in W-1 altered the electronic structure of W-1 to improve its light-harvesting ability, which accounted for the high activity of olefin isomerization under light irradiation up to 625 nm. Additionally, OVs on the W-1 surface generated unsaturated W5+ sites that coordinated with olefins for the efficient adsorption and activation of olefins. Mechanistic studies reveal that the in situ formation of surface π-complexes and π-allylic W intermediates originating from the coordination of coordinated unsaturated W5+ sites and olefins ensure high photocatalytic activity and selectivity of W-1 for the photocatalytic isomerization of olefins via a radical mechanism.
The effect of the position of cross-linkers on the structure and microenvironment of PPh3moiety in porous organic polymers
Ji, Guangjun,Li, Cunyao,Xiao, Dong,Wang, Guoqing,Sun, Zhao,Jiang, Miao,Hou, Guangjin,Yan, Li,Ding, Yunjie
, p. 9165 - 9174 (2021/04/16)
Three trivinyl functionalization triphenylphosphine (3vPPh3)-based porous organic ligands (3vPPh3-POLs) with cross-linkers in different positions were obtained through solvothermal polymerization. By simply changing the position of the cross-linkers (vinyl groups) attached to the PPh3monomer, the resulting porous organic polymer (POP) materials acquired diverse hierarchical porous structures, and the microenvironment of POPs was sequently regulated. Among the three 3vPPh3-POLs, the BET surface areas ranged from 168 to 1583 m2g?1, while the proportion of micropores changed from 0.0% to 52.0%. Benefiting from the unique structure, Rh ions could be coordinated and dispersed as a single site inm-3vPPh3-POL to form HRh(CO)2(PPh3-POL)2species, which endowed the Rh/m-3vPPh3-POL catalyst with an activity similar to that in the homogeneous system, anl/bratio (the ratio of the linear aldehyde to the branched aldehyde) approximately as high as 10, and stability for a duration of more than 500 h in the hydroformylation of 1-octene.
