- Synthesis of 1-(3-tert-butyldimethylsiloxy)phenyl-5,5-dimethyl-2,7,8-trioxabicyclo[4.2.0] octanes: New dioxetanes giving high chemiexcitation yields in thermolysis and in fluoride-induced CIEEL-decay
-
Dioxetanes with annelated six-membered ring, 1-(3-tert-butyldimethylsiloxy)phenyl-5,5-dimethyl-2,7,8-trioxabicyclo[4.2.0] octanes (2a-2c) were synthesized by singlet oxygenation of the corresponding aryl-substituted dihydropyrans (3). Thermolysis of 2a-2c gave the corresponding ketoesters (5a-5c) as a normal decomposition product together with a considerable amount (23-26%) of ester (6) derived from Norrish type I reaction of the triplet-excited ester (5). On the other hand, treatment with tetrabutylammonium fluoride (TBAF) in DMSO induced rapid decomposition of 2 to emit blue light in high chemiexcitation yield (72-75%) of the oxyanion of a ketoester (10). These results show that the chemiexcitation efficiency of dioxetanes (2) was higher than that of their five-membered ring analog (1) not only for thermolysis and but also for the base-induced CIEEL.
- Matsumoto, Masakatsu,Murayama, Junko,Nishiyama, Masao,Mizoguchi, Yasuko,Sakuma, Toshimitsu,Watanabe, Nobuko
-
-
Read Online
- Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
-
Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
-
supporting information
p. 9029 - 9039
(2021/06/28)
-
- Site-Specific Alkene Hydromethylation via Protonolysis of Titanacyclobutanes
-
Methyl groups are ubiquitous in biologically active molecules. Thus, new tactics to introduce this alkyl fragment into polyfunctional structures are of significant interest. With this goal in mind, a direct method for the Markovnikov hydromethylation of alkenes is reported. This method exploits the degenerate metathesis reaction between the titanium methylidene unveiled from Cp2Ti(μ-Cl)(μ-CH2)AlMe2 (Tebbe's reagent) and unactivated alkenes. Protonolysis of the resulting titanacyclobutanes in situ effects hydromethylation in a chemo-, regio-, and site-selective manner. The broad utility of this method is demonstrated across a series of mono- and di-substituted alkenes containing pendant alcohols, ethers, amides, carbamates, and basic amines.
- Bartfield, Noah M.,Frederich, James H.,Law, James A.
-
supporting information
p. 14360 - 14364
(2021/05/27)
-
- Zn-Mediated Hydrodeoxygenation of Tertiary Alkyl Oxalates
-
Herein we describe a general, mild, and scalable method for hydrodeoxygenation of readily accessible tertiary alkyl oxalates by Zn/silane under Ni-catalyzed conditions. The reduction method is suitable for an array of structural motifs derived from tertiary alcohols that bear diverse functional groups, including the synthesis of a key intermediate en route to estrone.
- Ye, Yang,Ma, Guobin,Yao, Ken,Gong, Hegui
-
supporting information
p. 1625 - 1628
(2021/01/18)
-
- Photocatalytic transfer hydrogenolysis of aromatic ketones using alcohols
-
A mild method of photocatalytic deoxygenation of aromatic ketones to alkyl arenes was developed, which utilized alcohols as green hydrogen donors. No hydrogen evolution during this transformation suggested a mechanism of direct hydrogen transfer from alcohols. Control experiments with additives indicated the role of acid in transfer hydrogenolysis, and catalyst characterization confirmed a larger number of Lewis acidic sites on the optimal Pd/TiO2 photocatalyst. Hence, a combination of hydrogen transfer sites and acidic sites may be responsible for efficient deoxygenation without additives. The photocatalyst showed reusability and achieved selective reduction in a variety of aromatic ketones.
- Gao, Zhuyan,Han, Jianyu,Hong, Feng,Lei, Lijun,Li, Hongji,Liu, Huifang,Luo, Nengchao,Wang, Feng
-
p. 3802 - 3808
(2020/07/09)
-
- ISOBUTYL BENZENE AND A PROCESS FOR SYNTHESIS OF ISOBUTYL BENZENE BY USING A CATALYST
-
The present disclosure provides a process for the synthesis of isobutyl benzene by side chain alkylation of toluene in the presence of a catalyst. The catalyst used ub the process of present disclosure provides maximum conversion of toluene with high selectivity towards isobutyl benzene.
- -
-
Page/Page column 13; 16-17
(2020/12/11)
-
- Reductive Deamination with Hydrosilanes Catalyzed by B(C6F5)3
-
The strong boron Lewis acid tris(pentafluorophenyl)borane B(C6F5)3 is known to catalyze the dehydrogenative coupling of certain amines and hydrosilanes at elevated temperatures. At higher temperature, the dehydrogenation pathway competes with cleavage of the C?N bond and defunctionalization is obtained. This can be turned into a useful methodology for the transition-metal-free reductive deamination of a broad range of amines as well as heterocumulenes such as an isocyanate and an isothiocyanate.
- Fang, Huaquan,Oestreich, Martin
-
supporting information
p. 11394 - 11398
(2020/05/25)
-
- Activation of C-C Bonds via σ-Bond Metathesis: Hydroborenium-Catalyzed Hydrogenolysis of Cyclopropanes
-
High-valent transition metal or main group complex mediated σ-bond metathesis plays an important role in the activation of covalent H-E bonds. However, its involvement in the activation of C-C bonds has remained elusive. Here we describe direct hydroboration of the C-C bonds of cyclopropanes by a hydroborenium complex. Our mechanism study suggests this reaction operates through a σ-bond metathesis pathway. With this hydroborenium complex as a catalyst, hydrogenolysis of unfunctionalized cyclopropanes was achieved, which is unprecedented for homogeneous catalysts and provides an unconventional approach for C-C bond functionalization in the absence of metals.
- Su, Bo,Li, Yawei,Li, Zhen Hua,Hou, Jun-Li,Wang, Huadong
-
supporting information
p. 4159 - 4163
(2020/04/10)
-
- Carbonyl and olefin hydrosilylation mediated by an air-stable phosphorus(iii) dication under mild conditions
-
The readily-accessible, air-stable Lewis acid [(terpy)PPh][B(C6F5)4]21 is shown to mediate the hydrosilylation of aldehydes, ketones, and olefins. The utility and mechanism of these hydrosilylations are considered.
- Andrews, Ryan J.,Chitnis, Saurabh S.,Stephan, Douglas W.
-
supporting information
p. 5599 - 5602
(2019/05/21)
-
- Mild and efficient rhodium-catalyzed deoxygenation of ketones to alkanes
-
A new and simple method for the deoxygenation of ketones to alkanes is presented. Most substrates are reduced under mild conditions by triethylsilane in the presence of catalytic amounts of [Rh(μ-Cl)(CO)2]2. This system selectively provides the methylene hydrocarbons in good to excellent yields starting from acetophenones and diaryl ketones. A rapid examination of the reaction pathway suggests that the ketone is first converted into an alcohol, which then undergoes hydrogenolysis to give the alkane.
- Argouarch, Gilles
-
supporting information
p. 11041 - 11044
(2019/07/31)
-
- Cleavage of lignin C-O bonds over a heterogeneous rhenium catalyst through hydrogen transfer reactions
-
Hydrogenolysis is one of the most popular strategies applied in the depolymerization of lignin for the production of aromatic chemicals. Currently, this strategy is mainly conducted under high hydrogen pressure, which can pose safety risks and is not sustainable and economical. Herein, we reported that heterogeneous rhenium oxide supported on active carbon (ReOx/AC) exhibited excellent activity in the selective cleavage of lignin C-O bonds in isopropanol. High yields of monophenols (up to 99.0%) from various lignin model compounds and aromatic liquid oils (>50%) from lignin feedstock were obtained under mild conditions in the absence of H2. The characterization of the catalyst by X-ray absorption fine structure, X-ray photoelectron spectroscopy and H2-temperature-programed reduction suggested that the activity of ReOx/AC could be attributed to the presence of ReIV-VI. The interaction between the surface oxygen groups of the active carbon and rhenium oxide could also play an important role in the cleavage of the C-O bonds. Notably, an ReOx/AC-catalyzed C-O bond cleavage pathway beyond a typical deoxydehydration mechanism was disclosed. More importantly, 2D-HSQC-NMR and GPC characterizations showed that ReOx/AC exhibited high activity not only in β-O-4 cleavage, but also in the deconstruction of more resistant β-5 and β-β linkages in lignin without destroying the aromatic ring. This study paves the way for the development of rhenium-based catalysts for the controlled reductive valorization of realistic lignin materials through a hydrogen transfer pathway.
- Zhang, Bo,Qi, Zaojuan,Li, Xinxin,Ji, Jianwei,Zhang, Leilei,Wang, Hua,Liu, Xiaoyan,Li, Changzhi
-
supporting information
p. 5556 - 5564
(2019/10/28)
-
- Selective Cleavage of C?O Bonds in Lignin Catalyzed by Rhenium(VII) Oxide (Re2O7)
-
The selective cleavage of C?O bonds in typical model lignin β-O-4 compounds and deconstruction of a realistic lignin feedstock catalyzed by Re2O7 is described. High yields of C?O cleavage products (up to 97.8 %) from model compounds and oils (76.3 %) from organosolv pinewood lignin were obtained under mild conditions. Evidence for the pathway of this catalytic process is also provided.
- Qi, Zaojuan,Zhang, Bo,Ji, Jianwei,Li, Xinxin,Dai, Tao,Guo, Haiwei,Wang, Aiqin,Lu, Lican,Li, Changzhi
-
p. 500 - 505
(2018/03/27)
-
- Catalytic Reduction of Alkyl and Aryl Bromides Using Propan-2-ol
-
Milstein's complex, (PNN)RuHCl(CO), catalyzes the efficient reduction of aryl and alkyl halides under relatively mild conditions by using propan-2-ol and a base. Sterically hindered tertiary and neopentyl substrates are reduced efficiently, as well as more functionalized aryl and alkyl bromides. The reduction process is proposed to occur by radical abstraction/hydrodehalogenation steps at ruthenium. Our research represents a safer and more sustainable alternative to typical silane, lithium aluminium hydride, and tin-based conditions for these reductions.
- Haibach, Michael C.,Stoltz, Brian M.,Grubbs, Robert H.
-
supporting information
p. 15123 - 15126
(2017/11/20)
-
- Catalytic Synthesis of “Super” Linear Alkenyl Arenes Using an Easily Prepared Rh(I) Catalyst
-
Linear alkyl benzenes (LAB) are global chemicals that are produced by acid-catalyzed reactions that involve the formation of carbocationic intermediates. One outcome of the acid-based catalysis is that 1-phenylalkanes cannot be produced. Herein, it is reported that [Rh(μ-OAc)(η2-C2H4)2]2 catalyzes production of 1-phenyl substituted alkene products via oxidative arene vinylation. Since C C bonds can be used for many chemical transformations, the formation of unsaturated products provides a potential advantage over current processes that produce saturated alkyl arenes. Conditions that provide up to a 10:1 linear:branched ratio have been achieved, and catalytic turnovers >1470 have been demonstrated. In addition, electron-deficient and electron-rich substituted benzenes are successfully alkylated. The Rh catalysis provides ortho:meta:para selectivity that is opposite to traditional acid-based catalysis.
- Webster-Gardiner, Michael S.,Chen, Junqi,Vaughan, Benjamin A.,McKeown, Bradley A.,Schinski, William,Gunnoe, T. Brent
-
p. 5474 - 5480
(2017/04/27)
-
- Methyl Hydrazinocarboxylate as a Practical Alternative to Hydrazine in the Wolff-Kishner Reaction
-
Herein we describe a facile protocol for the reduction of aromatic ketones and aldehydes to the corresponding methylene unit. The procedure involves isolation of a carbomethoxyhydrazone intermediate that is easily decomposed to the reduced product without the requirement for large quantities of pernicious hydrazine.
- Cranwell, Philippa B.,Russell, Andrew T.,Smith, Christopher D.
-
supporting information
p. 131 - 135
(2015/12/26)
-
- METHOD FOR PRODUCING ORGANIC COMPOUND
-
PROBLEM TO BE SOLVED: To provide a method of subjecting a compound having on one carbon atom a carbon atom constituting a carbon-carbon double bond and a functional group such as a hydroxyl group to a reductive reaction condition and producing an organic compound having the functional group substituted with a hydrogen atom. SOLUTION: There is provided a method for producing a compound represented by a formula (50) from a raw material compound represented by a formula (10). The method includes a step of irradiating a reaction system with light, the reaction system comprising the raw material compound, a hydrogen source compound, and a catalyst having a palladium component supported by a carrier containing titanium oxide. (R11 to R15 are a hydrogen atom, a hydrocarbon group having 1 to 40 carbon atoms which may have a cyclic structure or a derivative group thereof, or a heteroatom-containing group having 1 to 20 carbon atoms which may have a cyclic structure or a derivative group thereof; and R16 is a hydrogen atom, a hydrocarbon group having 1 to 40 carbon atoms or an acyl group having 1 to 20 carbon atoms which may have a cyclic structure, or -CH(CH2OH)2).) COPYRIGHT: (C)2015,JPO&INPIT
- -
-
Paragraph 0123-0124; 0126; 0128
(2018/10/16)
-
- Hydrodecarboxylation of Carboxylic and Malonic Acid Derivatives via Organic Photoredox Catalysis: Substrate Scope and Mechanistic Insight
-
A direct, catalytic hydrodecarboxylation of primary, secondary, and tertiary carboxylic acids is reported. The catalytic system consists of a Fukuzumi acridinium photooxidant with phenyldisulfide acting as a redox-active cocatalyst. Substoichiometric quantities of Hünigs base are used to reveal the carboxylate. Use of trifluoroethanol as a solvent allowed for significant improvements in substrate compatibilities, as the method reported is not limited to carboxylic acids bearing α heteroatoms or phenyl substitution. This method has been applied to the direct double decarboxylation of malonic acid derivatives, which allows for the convenient use of dimethyl malonate as a methylene synthon. Kinetic analysis of the reaction is presented showing a lack of a kinetic isotope effect when generating deuterothiophenol in situ as a hydrogen atom donor. Further kinetic analysis demonstrated first-order kinetics with respect to the carboxylate, while the reaction is zero-order in acridinium catalyst, consistent with another finding suggesting the reaction is light limiting and carboxylate oxidation is likely turnover limiting. Stern-Volmer analysis was carried out in order to determine the efficiency for the carboxylates to quench the acridinium excited state.
- Griffin, Jeremy D.,Zeller, Mary A.,Nicewicz, David A.
-
p. 11340 - 11348
(2015/09/21)
-
- Palladium nanoparticles supported on ionic liquid modified, magnetic nanobeads-recyclable, high-capacity catalysts for alkene hydrogenation
-
Magnetic hybrid materials have been synthesized as recyclable catalysts for alkene hydrogenation. The materials consist of magnetic nanobeads functionalized with imidazolium-based ionic liquids and optional polymer shells. Palladium nanoparticles (NPs) were synthesized on the surface of these supports by two different methods and evaluated as catalysts for alkene hydrogenation. Deposition of palladium(0) onto the magnetic nanobeads by microwave decomposition of Pd2(dba)3·CHCl3 leads to more efficient catalysts than the reduction of a Pd(ii) precursor. Reactivity, recycling ability and ease of separation of the catalysts are compared. A hybrid material without polymer shells and a quite flexible ionic liquid was identified as the most promising for stabilizing Pd NPs resulting in a catalyst that shows high activity (TOF up to 330 h-1), good recycling ability, and minor metal leaching into the product. Notably, the activity of this catalyst increases with an enhanced Pd loading, contrasting related systems for which a decrease of activity is observed due to agglomeration. Therefore, this recyclable, high-capacity system is especially attractive for large-scale applications, requiring just a minimal amount of supporting material for the recycling of expensive Pd that is readily achieved by magnetic decantation. The Royal Society of Chemistry.
- Linhardt, Roland,Kainz, Quirin M.,Grass, Robert N.,Stark, Wendelin J.,Reiser, Oliver
-
p. 8541 - 8549
(2014/03/21)
-
- Palladium nanoparticles supported on magnetic carbon-coated cobalt nanobeads: Highly active and recyclable catalysts for alkene hydrogenation
-
Palladium nanoparticles are deposited on the surface of highly magnetic carbon-coated cobalt nanoparticles. In contrast to the established synthesis of Pd nanoparticles via reduction of Pd(II) precursors, the microwave decomposition of a Pd(0) source leads to a more efficient Pd deposition, resulting in a material with considerably higher activity in the hydrogenation of alkenes. Systematic variation of the Pd loading on the carbon-coated cobalt nanoparticle surface reveals a distinct trend to higher activities with decreased loading of Pd. The activity of the catalyst is further improved by the addition of 10 vol% Et2O to iso-propanol that is found to be the solvent of choice. With respect to activity (turnover frequencies up to 11 095 h-1), handling, recyclability through magnetic decantation, and leaching of Pd (≤6 ppm/cycle), this novel magnetic hybrid material compares favorably to conventional Pd/C or Pd@CNT catalysts.
- Kainz, Quirin M.,Linhardt, Roland,Grass, Robert N.,Vile, Gianvito,Perez-Ramirez, Javier,Stark, Wendelin J.,Reiser, Oliver
-
p. 2020 - 2027
(2014/05/06)
-
- Influence of iridium content on the behavior of Pt-Ir/Al2O 3 and Pt-Ir/TiO2 catalysts for selective ring opening of naphthenes
-
The influence of Ir content on the properties of Pt-Ir/Al2O 3 and Pt-Ir/TiO2 catalysts for selective ring opening of naphthenes was studied. It was found that these catalysts display a strong Pt-Ir interaction but only a weak metal-support interaction. Catalyst acidities depend on the metal loading, but opposite effects were observed on alumina (decrease) or titania (increase) as the metal loading increased. The results obtained from test reactions (cyclohexane dehydrogenation and cyclopentane hydrogenolysis) showed that titania supported catalysts were less active than their alumina supported counterparts. This behavior could be due to the partial blockage of metallic sites by migrated TiOx species and the sinterization of metallic phase during the reduction step. The methylcyclopentane ring opening reaction was found to occur through a partially selective mechanism, and an increase in activity as the Ir loading increased was observed. The selective mechanism was favored by higher total metal loadings, possibly due to an increase in the size of metallic aggregates. Alumina supported catalysts present higher ring opening selectivities. The activity for decalin ring opening increased both with metal loading and reaction temperature level.
- Vicerich, María A.,Benitez, Viviana M.,Especel, Catherine,Epron, Florence,Pieck, Carlos L.
-
p. 167 - 174
(2013/03/29)
-
- PdAu alloy nanoparticles encapsulated by PPI-g-MWCNTs as a novel catalyst for chemoselective hydrogenation of alkenes under mild conditions
-
The synthesis, characterization and catalytic applications of bimetallic PdAu encapsulated on polypropylene imine grafted multi-wall carbon nanotubes hybrid materials have been reported. The results show that the catalyst induces a highly activity and chemoselective hydrogenation of less hindered alkenes to the corresponding alkanes using hydrogen gas in environmentally friendly solvents H2O/EtOH at 50 °C with high yields. The characterization of catalyst was confirmed by FT-IR, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray powder diffraction.
- Shaabani, Ahmad,Mahyari, Mojtaba
-
p. 1277 - 1284
(2014/01/06)
-
- Reaction of cinnamaldehyde and derivatives with Raney Ni-Al alloy and Al powder in water. Reduction or oxido-reduction?
-
A series of experiments dealing with the reduction of cinnamaldehyde and parent compounds was carried out in completely aqueous media in order to assess the character of this process. We wish to show that the treatment of these substrates in water with Raney catalysts is an oxido-reductive process.
- Simion, Alina-Marieta,Arimura, Takashi,Simion, Cristian
-
p. 476 - 481
(2013/07/19)
-
- Study of the products of benzene transformation in the presence of argon, hydrogen, and propane-butane mixture in barrier discharge
-
The conversion of benzene in a medium of Ar, H2, and propane-butane mixture in a dielectricbarrier discharge reactor, accompanied by polymerization yielding liquid and solid compounds, has been investigated. The amount of polymerization products reaches 79.7 wt %. Addition of H2 to benzene reduces the amount of benzene-soluble polymer-like compounds in the products to ～61 wt % and precludes the formation of solid polymerization products. The transformation of benzene with a propane-butane mixture yields alkylbenzenes (up to 38.5 wt %) and liquid alkanes (to 20.5 wt %, mainly with a branched structure). It has been found that an increase in benzene flow rate from 0.08 to 0.4 cm3/min in the case of benzene conversion with the propane-butane mixture can significantly reduce the amount of polymerization products from 56.7 to 9.1 wt %. Pleiades Publishing, Ltd., 2012.
- Kudryashov,Perevezentsev,Ryabov,Shchegoleva,Sirotkin
-
experimental part
p. 60 - 64
(2012/06/04)
-
- An unprecedented iron-catalyzed cross-coupling of primary and secondary alkyl Grignard reagents with non-activated aryl chlorides
-
The use of N-heterocyclic carbene ligands in the iron-catalyzed cross-coupling of alkyl Grignards has allowed, for the first time, coupling of non-activated, electron rich aryl chlorides. Surprisingly, the tetrahydrate of FeCl2 was found to be a better pre-catalyst than anhydrous FeCl 2. Primary Grignard reagents coupled in excellent yields while secondary Grignard reagents coupled in modest yields. The use of acyclic secondary Grignard reagents resulted in the formation of isomers in addition to the desired product. These isomeric products were formed via reversible β-hydrogen elimination, indicating that the cross-coupling proceeds through an ionic pathway.
- Perry, Marc C.,Gillett, Amber N.,Law, Tyler C.
-
experimental part
p. 4436 - 4439
(2012/09/25)
-
- Selective palladium-loaded MIL-101 catalysts
-
Palladium nanoparticles (NPs) of different mean particle size have been synthesized in the host structure of the porous coordination polymer (or metal-organic framework: MOF) MIL-101. The metal-organic chemical vapor deposition method was used to load MIL-101 with the Pd precursor complex [(η5-C5H5)Pd(η3-C 3H5)]. Loadings higher than 50 wt.% could be accomplished. Reduction of the Pd precursor complex with H2 gave rise to Pd NPs inside the MIL-101 (Pd@MIL-101). The reduction conditions, especially the temperature, allows us to make size-conform (size of the Pd NPs correlates with the size of the cavities of the host structure of MIL-101) and undersized Pd NPs. The Pd@MIL-101 samples were characterized by X-ray diffraction, IR spectroscopy, Brauner-Emmett-Teller (BET) analysis, elemental analysis, and transmission electron microscopy (TEM). Catalytic studies, hydrogenation of ketones, were performed with selected Pd@MIL-101 catalysts. Activity, selectivity, and recyclability of the catalyst family are discussed.
- Hermannsdoerfer, Justus,Kempe, Rhett
-
experimental part
p. 8071 - 8077
(2011/09/12)
-
- Mechanism of efficient anti-markovnikov olefin hydroarylation catalyzed by homogeneous Ir(iii) complexes
-
The mechanism of the hydroarylation reaction between unactivated olefins (ethylene, propylene, and styrene) and benzene catalyzed by [(R)Ir(μ-acac-O, O,C3)-(acac-O,O)2]2 and [R-Ir(acac-O,O) 2(L)] (R = acetylacetonato, CH3, CH2CH 3, Ph, or CH2CH2Ph, and L = H2O or pyridine) Ir(iii) complexes was studied by experimental methods. The system is selective for generating the anti-Markovnikov product of linear alkylarenes (61:39 for benzene + propylene and 98:2 for benzene + styrene). The reaction mechanism was found to follow a rate law with first-order dependence on benzene and catalyst, but a non-linear dependence on olefin. 13C-labelling studies with CH313CH2-Ir-Py showed that reversible β-hydride elimination is facile, but unproductive, giving exclusively saturated alkylarene products. The migration of the 13C-label from the α to β-positions was found to be slower than the C-H activation of benzene (and thus formation of ethane and Ph-d 5-Ir-Py). Kinetic analysis under steady state conditions gave a ratio of the rate constants for CH activation and β-hydride elimination (k CH: kβ) of ～0.5. The comparable magnitude of these rates suggests a common rate determining transition state/intermediate, which has been shown previously with B3LYP density functional theory (DFT) calculations. Overall, the mechanism of hydroarylation proceeds through a series of pre-equilibrium dissociative steps involving rupture of the dinuclear species or the loss of L from Ph-Ir-L to the solvento, 16-electron species, Ph-Ir(acac-O,O)2-Sol (where Sol refers to coordinated solvent). This species then undergoes trans to cis isomerization of the acetylacetonato ligand to yield the pseudo octahedral species cis-Ph-Ir-Sol, which is followed by olefin insertion (the regioselective and rate determining step), and then activation of the C-H bond of an incoming benzene to generate the product and regenerate the catalyst.
- Bhalla, Gaurav,Bischof, Steven M.,Ganesh, Somesh K.,Liu, Xiang Yang,Jones,Borzenko, Andrey,Tenn III, William J.,Ess, Daniel H.,Hashiguchi, Brian G.,Lokare, Kapil S.,Leung, Chin Hin,Oxgaard, Jonas,Goddard III, William A.,Periana, Roy A.
-
experimental part
p. 69 - 81
(2011/03/21)
-
- SELECTIVE OLIGOMERIZATION OF ISOBUTENE
-
A process for oligomerizing isobutene comprises contacting a feedstock comprising isobutene with a catalyst comprising a MCM-22 family molecular sieve under conditions effective to oligomerize the isobutene, wherein said conditions including a temperature from about 45°C to less than 140°C. The isobutene may be a component of a hydrocarbon feedstock containing at least one additional C4 alkene.
- -
-
Page/Page column 16-17
(2009/05/30)
-
- Functional group tolerant Kumada-Corriu-Tamao coupling of nonactivated alkyl halides with aryl and heteroaryl nucleophiles: Catalysis by a nickel pincer complex permits the coupling of functionalized Grignard reagents
-
A nickel(II) pincer complex [(MeNN2)NiCl] (1) catalyzes Kumada-Corriu-Tamao cross coupling of nonactivated alkyl halides with aryl and heteroaryl Grignard reagents. The coupling of octyl bromide with phenylmagnesium chloride was used as a test reaction. Using 3 mol % of 1 as the precatalyst and THF as the solvent, and in the presence of a catalytic amount of TMEDA, the coupling product was obtained in a high yield. The reaction conditions could be applied to cross coupling of other primary and secondary alkyl bromides and iodides. The coupling is tolerant to a wide range of functional groups. Therefore, alkyl halides containing ester, amide, ether, thioether, alcohol, pyrrole, indole, furan, nitrile, conjugated enone, and aryl halide moieties were coupled to give high isolated yields of products in which these units stay intact. For the coupling of ester-containing substrates, O-TMEDA is a better additive than TMEDA. The reaction protocol proves to be efficient for the coupling of Knochel-type functionalized Grignard reagents. Thus aryl Grignard reagents containing electron-deficient and/or sensitive ester, nitrile, amide, and CF3 substituents could be successfully coupled to nonactivated and functionalized alkyl iodides. The catalysis is also efficient for the coupling of alkyl iodides with functionalized heteroaryl Grignard reagents, giving rise to pyridine-, thiophene-, pyrazole-, furan-containing molecules with additional functionalities. Concerning the mechanism of the catalysis, [(MeNN2)Ni-(hetero)Ar] was identified as an intermediate, and the activation of alkyl halides was found to take place through a radical-rebound process.
- Vechorkin, Oleg,Proust, Valerie,Hu, Xile
-
supporting information; experimental part
p. 9756 - 9766
(2011/03/19)
-
- Palladium nanoparticles supported onto ionic carbon nanotubes as robust recyclable catalysts in an ionic liquid
-
Palladium nanoparticles have been deposited onto imidazolium bromide-functionalized ionic MWCNTs through hydrogen reduction of Na 2PdCl4 in water without aid of surfactants under extremely mild conditions, and combined with an ionic liquid to create a new recyclable ionic liquid-based catalytic system allowing up to 50 times recycling. The Royal Society of Chemistry.
- Chun, Yu Sung,Shin, Ju Yeon,Song, Choong Eui,Lee, Sang-Gi
-
p. 942 - 944
(2008/09/21)
-
- PROCESS FOR PRODUCING SEC-BUTYLBENZENE
-
A process for producing sec-butylbenzene comprises contacting a feed comprising benzene and a C4 alkylating agent under alkylation conditions comprising a temperature of about 110°C to about 150°C with a catalyst comprising at least one molecular sieve having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom. The sec-butylbenzene can be then oxidized to produce a hydroperoxide and the hydroperoxide decomposed to produce phenol and methyl ethyl ketone.
- -
-
Page/Page column 15-16
(2008/06/13)
-
- PROCESS FOR PRODUCING PHENOL AND METHYL ETHYL KETONE
-
A process for producing phenol and methyl ethyl ketone comprises contacting benzene and a C4 olefin under alkylation conditions and in the presence of an alkylation catalyst to produce an alkylation effluent comprising secbutylbenzene and C8+ olefins. The alkylation effluent is then treated to reduce the amount of said C8+ olefins and produce a treated effluent, whereafter the secbutylbenzene in the treated effluent is oxidized to produce a hydroperoxide and the hydroperoxide is cleaved to produce phenol and methyl ethyl ketone.
- -
-
Page/Page column 18-20
(2008/06/13)
-
- PROCESS FOR PRODUCING PHENOL AND METHYL ETHYL KETONE
-
A process for producing phenol and methyl ethyl ketone comprises contacting benzene with a C4 alkylating agent under aklylation conditions with catalyst comprising zeolite beta or a molecular sieve having an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom to produce an alkylation effluent comprising sec-butylbenzene. The sec-butylbenzene is then oxidized to produce a hydroperoxide and the hydroperoxide is decomposed to produce phenol and methyl ethyl ketone.
- -
-
Page/Page column 26-27
(2008/06/13)
-
- Reactions of alkyl radicals with substituted toluenes and the effect of substituents on dissociation energies of benzyl C-H bonds
-
Reactions of isopropyl and of undecyl radicals with meta- and para-substituted toluenes are reported. The results demonstrate that the reactivities of toluenes are due to both benzyl-H abstraction and addition of the alkyl radicals to the aromatic ring. Relative reactivities yield curved Hammett plots, consistent with kinetic data reported by Dutsch and Fischer. Abstractions and ring additions occur with comparable rates, but opposite Hammett slopes. Addition is favored by electron-withdrawing and abstraction by electron-donating substituents. The effects of substituents on the dissociation energies of benzyl C-H bonds are shown to be the major factor influencing reaction rates for benzyl-H abstraction by alkyl radicals.
- Arafat, Abdelfattah M.,Mathew, Samuel K.,Akintobi, Solademi O.,Zavitsas, Andreas A.
-
p. 2226 - 2242
(2007/10/03)
-
- Method for producing alkali metal catalyst and use thereof for the side-chain alklation of alkyl aromatics
-
The invention relates to a process for the preparation of an alkali metal catalyst by mixing an alkali metal with pulverulent, solid potassium carbonate as support, wherein the potassium carbonate has a specific surface area of at least 0.3 m2/g, and to the use thereof for the side-chain alkylation of alkylbenzenes.
- -
-
-
- Radical Chain Reaction or Benzenethiol with Pentynylthiol Esters: Production of Aldehydes under Stannane/Silane-Free Conditions
-
The radical chain reaction of benzenethiol with accessible 4-pentynylthiol esters provides a new stannane/silane-free protocol for the production of aromatic and aliphatic aldehydes. The procedure is especially useful for the aryl and primary aldehydes, even in the presence of substituents highly sensitive to reductive conditions, and is also of some utility for the vinylic and secondary ones, The protocol is instead not applicable to the tertiary aldehydes, owing to preferential alkane-forming decarbonylation, although the tertiary ones derived from bridgehead precursors can still be usefully produced.
- Benati, Luisa,Leardini, Rino,Minozzi, Matteo,Nanni, Daniele,Scialpi, Rosanna,Spagnolo, Piero,Zanardi, Giuseppe
-
p. 985 - 990
(2007/10/03)
-
- Reduction of carbonyl groups to the corresponding methylenes with Ni-Al alloy in water
-
The reduction of carbonyl compounds 1a-h using Ni-Al alloy in water under reflux proceeded to give the corresponding methylene compounds 2a-h within 2 h in 89.0-99.8% relative yields.
- Ishimoto, Keiko,Mitoma, Yoshiharu,Nagashima, Satoko,Tashiro, Hideki,Prakash, G. K. Surya,Olah, George A.,Tashiro, Masashi
-
p. 514 - 515
(2007/10/03)
-
- Pinacol reduction-cum-rearrangement. A re-examination of the reduction of aryl alkyl ketones by zinc-aluminum chloride
-
Reduction of alkyl phenyl ketones by zinc and aluminum chloride in acetonitrile results in pinacol condensation followed by rearrangement. The phenyl group migrates in every instance.
- Grant, Anya A.,Allukian, Myron,Fry, Albert J.
-
p. 4391 - 4393
(2007/10/03)
-
- Palladium-catalyzed coupling of alkyl chlorides and Grignard reagents
-
Chloroalkanes refined: A simple catalyst system renders the palladium-catalyzed coupling reaction of functionalized alkyl chlorides and Grignard reagents at room temperature (see example in scheme; PCy3 = tricyclohexylphosphane, NMP = N-methylpyrrolidinone).
- Frisch, Anja C.,Shaikh, Nadim,Zapf, Alexander,Belier, Matthias
-
p. 4056 - 4059
(2007/10/03)
-
- Direct reduction of alcohols: Highly chemoselective reducing system for secondary or tertiary alcohols using chlorodiphenylsilane with a catalytic amount of indium trichloride
-
The direct reduction of alcohols using chlorodiphenylsilane as A hydride source in the presence of a catalytic amount of indium trichloride is described. Benzylic alcohols, secondary alcohols, and tertiary alcohols were effectively reduced to give the corresponding alkanes in high yields. A compound bearing both primary and secondary hydroxyl groups was reduced only at the secondary site to afford the primary alcohol after workup with Bu4NF. This system showed high chemoselectivity only for the hydroxyl group while not reducing other functional groups that are readily reduced by standard reducing systems. Thus alcohols bearing ester, chloro, bromo, or nitro groups, which are sensitive to LiAlH4 or Zn/H+, were selectively reduced only at the hydroxyl sites by the chlorodiphenylsilane/InCl3 system. NMR studies revealed the reaction course. The hydrodiphenyl-silyl ether is initially formed and then, with InCl3 acting as a Lewis acid, forms an oxonium complex, which accelerates the desiloxylation with donation of the hydrogen to the carbon.
- Yasuda,Onishi,Ueba,Miyai,Baba
-
p. 7741 - 7744
(2007/10/03)
-
- Quantum Yields of the Initiation Step and Chain Propagation Turnovers in SRN1 Reactions: Photostimulated Reaction of 1-Iodo-2-methyl-2-phenyl Propane with Carbanions in DMSO
-
Neophyl radicals were generated by photoinduced electron transfer (PET) from a suitable donor to the neophyl iodide (1, 1-iodo-2-methyl-2-phenylpropane). The PET reaction of 1 with the enolate anion of cyclohexenone (2) afforded mainly the reduction products tert-butylbenzene (5) and the rearranged isobutylbenzene (6), arising from hydrogen abstraction of the neophyl radical (15) and the rearranged radical 16 intermediates, respectively. The photostimulated reaction of 1 with 2 in the presence of di-tert-butylnitroxide, as a radical trap, afforded adduct 10 in 57% yield. The photoinduced reaction of the enolate anion of acetophenone (3) with 1 gave the substitution products 11 (50%) and 12 (16%), which arise from the coupling of 3 with radicals 15 and 16, respectively. The rate constant obtained for the addition of anion 3 to radical 15 was 1.2 × 105 M-1 s-1, by the use of the rearrangement of this radical as a clock reaction. The anion of nitromethane (4) was almost unreactive at the initiation step, but in the presence of 2 under irradiation, it gave high yields (67%) of the substitution product 13 and only 2% of the rearranged product 14. When the ratio of 4 to 1 was diminished, it was possible to observe both substitution products 13 and 14 in 16% and 6.4% yields, respectively. These last results allowed us to estimate the coupling rate constant of neophyl radicals 15 with anion 4 to be at least of the order of 106 M-1 s-1. Although the overall quantum yield determined (λ = 350 nm) for the studied reactions is below 1, the chain lengths (Φpropagation) for the reaction of 1 with anions 3 and 4 are 127 and 2, respectively.
- Argueello, Juan E.,Penenory, Alicia B.,Rossi, Roberto A.
-
p. 7175 - 7182
(2007/10/03)
-
- Hydrodehalogenation of 1,1-dibromocyclopropanes by Grignard reagents promoted by titanium compounds
-
1,1-Dibromocyclopropanes are converted into the corresponding monobromocyclopropanes (as mixtures of stereoisomers where appropriate) by reaction with 1.0-1.3 mol equiv. of ethylmagnesium bromide and 2-10 mol% titanium isopropoxide for 90%). With ethylmagnesium bromide, the reaction occurs very slowly in the absence of catalyst; with methylmagnesium bromide, the reaction does occur in the absence of catalyst, but is only slightly promoted in the presence of titanium isopropoxide. Reactions with a number of other Grignard reagents are also discussed. In the case of phenethylmagnesium bromide, the major product containing the phenethyl-group is ethylbenzene, together with small amounts of styrene and ethyl 4-phenyl-2-butyl ether, a product of trapping of the solvent, ether. In other cases, relatively large amounts of a diether, formally derived by hydrogen ion adjacent to the ether oxygen followed by dimerisation, are isolated. No products were identified incorporating the cyclopropane and either the Grignard alkyl group or the solvent. Labelling studies indicate that the hydrogen introduced into the cyclopropane is not derived from either the α- or β-positions of the Grignard reagent. When the reduction is carried out with phenethylmagnesium bromide in d8-tetrahydrofuran both monobromides contain deuterium.
- Dulayymi, Juma'a R. Al,Baird, Mark S.,Bolesov, Ivan G.,Nizovtsev, Alexey V.,Tverezovsky, Viacheslav V.
-
p. 1603 - 1618
(2007/10/03)
-
- New reactivity of a reducing reagent generated from a copper(I) salt and a hydrosilane: Selective reduction of ketones and olefins conjugated with an aromatic group
-
Aromatic ketones and olefins were selectively converted to the corresponding alcohols and alkanes by a reagent prepared from a copper(I) salt and a hydrosilane. Excess use of the hydrosilane is most important to attain the high reactivities. One-electron transfer process as well as nucleophilic reaction of hydride would contribute to the selectivity.
- Ito, Hajime,Yamanaka, Hiroshi,Ishizuka, Tomoko,Tateiwa, Jun-Ichi,Hosomi, Akira
-
p. 479 - 482
(2007/10/03)
-
- Alkylation of benzene with 1-butene in the presence of AlCl3
-
The catalytic alkylation of benzene with 1-butene at 20-50×C and varied amounts of the AlCl3 catalyst was studied with the aim of optimization of the method of synthesis of sec-butylbenzene. By means of NMR and IR spectroscopy it was shown that together with the main product, sec-butylbenzene the reaction gives 1,3- and 1,4-di-sec-butylbenzenes. The alkylation conditions that allow preparation of sec-butylbenzene and its subsequent isomerization to isobutylbenzene were found.
- Kharlampidi,Izmailov,Batyrshin
-
p. 278 - 280
(2007/10/03)
-
- Formation of cyclopropanes by homolytic substitution reactions of 3- iodopropyl radicals: Preparative and rate studies
-
Reduction of 2-substituted 1,3-diiodopropane derivatives with tin hydride provides substituted cyclopropanes. The reaction occurs through a homolytic substitution of the 3-iodopropyl radical, which has a rate constant of about 5 x 105 s-1 at 80°C.
- Curran, Dennis P.,Gabarda, Ana E.
-
p. 3327 - 3336
(2007/10/03)
-
- Side-chain alkylation of toluene with propene on caesium/nanoporous carbon catalysts
-
Caesium/nanoporous carbon materials are powerful solid-base catalysts, promoting the side-chain alkylation toluene with propene in a continuous flow reactor conditions as mild as 150°C and 50 psig.
- Stevens, Mark G.,Anderson, Melony R.,Foley, Henry C.
-
p. 413 - 414
(2007/10/03)
-
- Deactivation of catalysts based on modified faujasites and pentasils in alkylation of benzene with butanol
-
Deactivation of various cationic forms of zeolite-containing catalysts was studied in the course of alkylation of benzene with butanol. Main parameters affecting the activity and selectivity of faujasite- and Pentasil-containing catalysts in the alkylation were determined.
- Galai,Osokina,Potekhin,Timofeev
-
p. 435 - 439
(2007/10/03)
-
- 9,10-Dihydro-9-sila-10-heteroanthracenes as new radical-based reducing agents
-
9,10-Dihydro-9-silaanthracenes 1 containing a heteroatom at the 10-position have been prepared and their reducing abilities for the reduction of some organic compounds under radical conditions have been investigated. Derivatives possessing a silicon, tin, oxygen or sulfur atom at the 10-position exhibited enhanced reactivities compared with the open-chain models. Among them, 9,10-dimethyl-9,10-dihydro-9,10-disilaanthracene 1a proved to be the most effective reagent for AIBN-initiated dehalogenation of organic halides and deoxygenation of aliphatic alcohols via O-thiocarbonyl derivatives. The rate constants for hydrogen abstraction from the Si-H moiety of these silaanthracenes 1 were determined using the neophyl rearrangement as a free radical clock in order to estimate their reactivities.
- Oba, Makoto,Kawahara, Yoko,Yamada, Ryo,Mizuta, Hidetaka,Nishiyama, Kozaburo
-
p. 1843 - 1848
(2007/10/03)
-
- Chemical reactions in supercritical water -1. pyrolysis of tert.-butylbenzene
-
Supercritical water is a powerful solvent and a favourable reaction medium for oxidation of organic material. The role of supercritical water in these processes is not fully understood. The influence of supercritical water on the pyrolysis of tert.-butylbenzene as a model compound was investigated. Experiments were carried out in a flow reactor at pressures between 5 and 25 MPa, at temperatures between 505 and 540°C and residence times between 15 and 55 s. Water, nitrogen, and water-nitrogen mixtures, respectively, were used as reaction media; no significant differences in the product formation rates and distributions were detected. In an experiment with D2O, instead of H2O, it was proved, that deuterium is incorporated in all the product substances in various amounts. Interpretating the results with a reaction model based on a radical mechanism it was made probable that H-D exchange reactions occur with radical intermediates. VCH Verlagsgesellschaft mbH, 1996.
- Kruse, Andrea,Ebert
-
-
