- Contra-thermodynamic Olefin Isomerization by Chain-Walking Hydroboration and Dehydroboration
-
We report a dehydroboration process that can be coupled with chain-walking hydroboration to create a one-pot, contra-thermodynamic, short-or long-range isomerization of internal olefins to terminal olefins. This dehydroboration occurs by a sequence comprising activation with a nucleophile, iodination, and base-promoted elimination. The isomerization proceeds at room temperature without the need for a fluoride base, and the substrate scope of this isomerization is expanded over those of previous isomerizations we have reported with silanes.
- Bloomer, Brandon,Butcher, Trevor W.,Ciccia, Nicodemo R.,Conk, Richard J.,Hanna, Steven,Hartwig, John F.
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p. 1005 - 1010
(2022/02/10)
-
- Norrish type II reactions of acyl azolium salts
-
The photochemical reactivity of acyl azolium salts derived from aliphatic carboxylic acids has been investigated. These species, which serve as models for intermediates generated in N-heterocyclic carbene (NHC) organocatalysis, undergo Norrish type II elimination reactions under irradiation with UVA light in analogy to structurally related aromatic ketones. Moreover, efficient Norrish-Yang cyclization was observed from an adamantyl-substituted derivative. These results further demonstrate the ability of NHCs to influence the absorption properties and photochemical reactivity of carbonyl groups during a catalytic cycle.
- Hopkinson, Matthew N.,Mavroskoufis, Andreas,Rieck, Arielle
-
-
- Preparation method of vinylcyclohexane
-
The invention discloses a preparation method of vinylcyclohexane, and belongs to the technical field of organic synthesis. Cyclohexyl ketone is used as a raw material, and is firstly condensed with 2, 4, 6-triisopropylbenzenesulfonyl hydrazide to obtain 1-acetocyclohexane-2, 4, 6-triisopropylbenzenesulfonyl hydrazone; and reaction is carried out in the presence of an inorganic base and a non-nucleophilic strong base to obtain vinylcyclohexane. The method has the advantages of two-step reaction, simple route, high area selection and relatively easy product separation, and a certain amount of polymerization inhibitor needs to be added in the product distillation process to prevent polymerization in the distillation process.
- -
-
Paragraph 0028-0039
(2021/04/29)
-
- A METHOD FOR PRODUCING VINYLCYCLOALKANES COMPOUNDS
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The present invention relates to a method for producing vinylcycloalkanes compounds represented by the general formula (5) highly selectively and economically, which comprises hydrogenation and dehydration. Hydrogenation step: hydrogenating the compounds represented by the general formula (1) or/and (2) or/and (3) or/and (4) with hydrogen to prepare the corresponding primary or secondary alcohols in the presence of hydrogenation catalyst with min. 0.1 part by wight. Dehydration step: dehydrating the corresponding primary or secondary alcohols prepared by the above-mentioned hydrogenation step to prepare vinylcycloalkanes compounds represented by the general formula (5) in the presence of dehydration catalyst. R 1 -CH2-CH2-OH (1) Wherein R 1 of the general formula (1)~(4) is hydrocarbyl (hydrocarbon functional group) having aromatic rings. R 2 -CH=CH2(5) Wherein R 2 of the general formula (5) is cycloalkyl or cycloalkyl-substituted alkyl.
- -
-
Paragraph 0047-0050
(2021/07/13)
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- A Systems Approach to a One-Pot Electrochemical Wittig Olefination Avoiding the Use of Chemical Reductant or Sacrificial Electrode
-
An unprecedented one-pot fully electrochemically driven Wittig olefination reaction system without employing a chemical reductant or sacrificial electrode material to regenerate triphenylphosphine (TPP) from triphenylphosphine oxide (TPPO) and base-free in situ formation of Wittig ylides, is reported. Starting from TPPO, the initial step of the phosphoryl P=O bond activation proceeds through alkylation with RX (R=Me, Et; X=OSO2CF3 (OTf)), affording the corresponding [Ph3POR]+X? salts which undergo efficient electroreduction to TPP in the presence of a substoichiometric amount of the Sc(OTf)3 Lewis acid on a Ag-electrode. Subsequent alkylation of TPP affords Ph3PR+ which enables a facile and efficient electrochemical in situ formation of the corresponding Wittig ylide under base-free condition and their direct use for the olefination of various carbonyl compounds. The mechanism and, in particular, the intriguing role of Sc3+ as mediator in the TPPO electroreduction been uncovered by density functional theory calculations.
- Chakraborty, Biswarup,Kostenko, Arseni,Menezes, Prashanth W.,Driess, Matthias
-
supporting information
p. 11829 - 11834
(2020/08/19)
-
- An Annelated Mesoionic Carbene (MIC) Based Ru(II) Catalyst for Chemo- And Stereoselective Semihydrogenation of Internal and Terminal Alkynes
-
The catalytic utility of [RuL1(CO)2I2] (1), containing an annelated π-conjugated imidazo-naphthyridine-based mesoionic carbene (MIC) ligand (L1), is evaluated for E-selective alkyne semihydrogenation. The precatalyst 1, in combination with 2 equiv of AgBArF, semihydrogenates a broad range of internal alkynes with molecular hydrogen (5 bar) in water. (E)-Alkenes are accessed in high yields, and a number of reducible functional groups are tolerated. A chelate MIC ligand and two cis carbonyls provide a well-defined platform at the Ru center for hydrogenation and isomerization. The loss of two iodides and the presence of two carbonyls render the Ru center electron deficient and thus the formation of metal vinylidenes with terminal alkynes is avoided. This is leveraged for the semihydrogenation of terminal alkynes by the same catalytic system in isopropyl alcohol. Reaction profile, isomerization, kinetic, and DFT studies reveal initial alkyne hydrogenation to a (Z)-alkene, which further isomerizes to an (E)-alkene via metal-catalyzed Z → E isomerization.
- Bera, Jitendra K.,Choudhury, Joyanta,Das, Shubhajit,Dutta, Indranil,Pati, Swapan K.,Saha, Sayantani,Yadav, Suman
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p. 3212 - 3223
(2020/10/02)
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- Fast and Selective Semihydrogenation of Alkynes by Palladium Nanoparticles Sandwiched in Metal–Organic Frameworks
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The semihydrogenation of alkynes into alkenes rather than alkanes is of great importance in the chemical industry. Unfortunately, state-of-the-art heterogeneous catalysts hardly achieve high turnover frequencies (TOFs) simultaneously with almost full conversion, excellent selectivity, and good stability. Here, we used metal–organic frameworks (MOFs) containing Zr metal nodes (“UiO”) with tunable wettability and electron-withdrawing ability as activity accelerators for the semihydrogenation of alkynes catalyzed by sandwiched palladium nanoparticles (Pd NPs). Impressively, the porous hydrophobic UiO support not only leads to an enrichment of phenylacetylene around the Pd NPs but also renders the Pd surfaces more electron-deficient, which leads to a remarkable catalysis performance, including an exceptionally high TOF of 13835 h?1, 100 % phenylacetylene conversion 93.1 % selectivity towards styrene, and no activity decay after successive catalytic cycles. The strategy of using molecularly tailored supports is universal for boosting the selective semihydrogenation of various terminal and internal alkynes.
- Choe, Kwanghak,Li, Guodong,Qiu, Xueying,Ri, Myonghak,Shi, Xinghua,Tang, Zhiyong,Wang, Hui,Wang, Yinglong,Xue, Guangxin,Yuan, Yi,Zhao, Wenshi,Zheng, Fengbin
-
supporting information
p. 3650 - 3657
(2020/02/04)
-
- Semihydrogenation of Alkynes Catalyzed by a Pyridone Borane Complex: Frustrated Lewis Pair Reactivity and Boron–Ligand Cooperation in Concert
-
The metal-free cis selective hydrogenation of alkynes catalyzed by a boroxypyridine is reported. A variety of internal alkynes are hydrogenated at 80 °C under 5 bar H2 with good yields and stereoselectivity. Furthermore, the catalyst described herein enables the first metal-free semihydrogenation of terminal alkynes. Mechanistic investigations, substantiated by DFT computations, reveal that the mode of action by which the boroxypyridine activates H2 is reminiscent of the reactivity of an intramolecular frustrated Lewis pair. However, it is the change in the coordination mode of the boroxypyridine upon H2 activation that allows the dissociation of the formed pyridone borane complex and subsequent hydroboration of an alkyne. This change in the coordination mode upon bond activation is described by the term boron-ligand cooperation.
- Wech, Felix,Hasenbeck, Max,Gellrich, Urs
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supporting information
p. 13445 - 13450
(2020/09/23)
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- Creation of Redox-Active PdSx Nanoparticles Inside the Defect Pores of MOF UiO-66 with Unique Semihydrogenation Catalytic Properties
-
Semihydrogenation of alkynes to produce alkenes is very important in the industry; however, over-hydrogenation heavily complicates the postprocesses, which are highly energy consuming and not environmentally friendly. One of the most efficient pathways to solve this challenging issue is to develop highly selective catalysts that could only hydrogenate alkynes and are inactive in hydrogenation of alkenes. This work presents herein an efficient catalyst, consisting of in situ created PdS0.53 nanoparticles as the redox-active sites inside the defect pores of metal–organic framework UiO-66, which demonstrates very high alkene selectivity (up to 99.5%) in semihydrogenation of easily over-hydrogenated terminal alkynes. In contrast to the traditional catalysts, strict control over the reaction time becomes the nonessential condition because the catalyst system is almost inactive in hydrogenation of alkenes. Therefore, this paradigm work provides a practically applicable pathway for the development of efficient catalysts with unique catalytic properties for selective semihydrogenation reactions.
- Dong, Ming-Jie,Wang, Xuan,Wu, Chuan-De
-
-
- Br?nsted Acid Catalyzed Peterson Olefinations
-
A mild and facile Peterson olefination has been developed employing low catalyst loading of the Br?nsted acid HNTf2. The reactions are typically performed at room temperature, with the reaction tolerant to a range of useful functionalities. Furthermore, we have extended this methodology to the synthesis of enynes.
- Britten, Thomas K.,McLaughlin, Mark G.
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p. 301 - 305
(2019/12/25)
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- Transfer hydrogenation of alkynes into alkenes by ammonia borane over Pd-MOF catalysts
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Ammonia borane with both hydridic and protic hydrogens in its structure acted as an efficient transfer hydrogenation agent for selective transformation of alkynes into alkenes in non-protic solvents. Catalytic synergy between the μ3-OH groups of the UiO-66(Hf) MOF and Pd active sites in Pd/UiO-66(Hf) furnished an elusive >98% styrene selectivity and full phenylacetylene conversion at room temperature. Such performance is not achievable by a Pd + UiO-66(Hf) physical mixture or by a commercial Pd/C catalyst.
- Bakuru, Vasudeva Rao,Samanta, Debabrata,Maji, Tapas Kumar,Kalidindi, Suresh Babu
-
supporting information
p. 5024 - 5028
(2020/05/08)
-
- Monodisperse nickel-nanoparticles for stereo- and chemoselective hydrogenation of alkynes to alkenes
-
Here, we report the use of monosaccharides for the preparation of novel nickel nanoparticles (NP), which constitute selective hydrogenation catalysts. For example, immobilization of fructose and Ni(OAc)2 on silica and subsequent pyrolysis under inert atmosphere produced graphitic shells encapsulated Ni-NP with uniform size and distribution. Interestingly, fructose acts as structure controlling compound to generate specific graphitic layers and the formation of monodisperse NP. The resulting stable and reusable catalysts allow for stereo- and chemoselective semihydrogenation of functionalized and structurally diverse alkynes in high yields and selectivity.
- Murugesan, Kathiravan,Alshammari, Ahmad S.,Sohail, Manzar,Beller, Matthias,Jagadeesh, Rajenahally V.
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p. 372 - 377
(2019/01/26)
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- Phosphonium Phenolate Zwitterion vs Phosphonium Ylide: Synthesis, Characterization and Reactivity Study of a Trimethylphosphonium Phenolate Zwitterion
-
4-Methoxy-3-(trimethylphosphonio)phenolate was obtained from a regioselective addition of PMe3 to p-quinone monoacetal. This compound undergoes hydrogen isotope exchange with D2O or CD3CN, and is capable of catalyzing H/D exchange of CD3CN with substrates bearing weakly acidic hydrogens. It exhibits similar reactivity to phosphorus ylides for olefinations of aldehydes. A possible tautomerization between the phosphonium phenolate zwitterion and phosphonium ylide is proposed for the first time to rationalize the unique reactivity.
- Xiao, Jing,Li, Qiang,Shen, Ruwei,Shimada, Shigeru,Han, Li-Biao
-
supporting information
p. 5715 - 5720
(2019/11/22)
-
- Metal-Free Catalytic Reductive Cleavage of Enol Ethers
-
In contrast to the well-known reductive cleavage of the alkyl-O bond, the cleavage of the alkenyl-O bond is much more challenging especially using metal-free approaches. Unexpectedly, alkenyl-O bonds were reductively cleaved when enol ethers were reacted with Et3SiH and a catalytic amount of B(C6F5)3. Supposedly, this reaction is the result of a B(C6F5)3-catalyzed tandem hydrosilylation reaction and a silicon-assisted β-elimination. A mechanism for this cleavage reaction is proposed based on experiments and density functional theory (DFT) calculations.
- Chulsky, Karina,Dobrovetsky, Roman
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p. 6804 - 6807
(2018/11/02)
-
- Design of Core-Pd/Shell-Ag Nanocomposite Catalyst for Selective Semihydrogenation of Alkynes
-
We designed core-Pd/shell-Ag nanocomposite catalyst (Pd@Ag) for highly selective semihydrogenation of alkynes. The construction of the core-shell nanocomposite enables a significant improvement in the low activity of Ag NPs for the selective semihydrogenation of alkynes because hydrogen is supplied from the core-Pd NPs to the shell-Ag NPs in a synergistic manner. Simultaneously, coating the core-Pd NPs with shell-Ag NPs results in efficient suppression of overhydrogenation of alkenes by the Pd NPs. This complementary action of core-Pd and shell-Ag provides high chemoselectivity toward a wide range of alkenes with high Z-selectivity under mild reaction conditions (room temperature and 1 atm H2). Moreover, Pd@Ag can be easily separated from the reaction mixture and is reusable without loss of catalytic activity or selectivity.
- Mitsudome, Takato,Urayama, Teppei,Yamazaki, Kenji,Maehara, Yosuke,Yamasaki, Jun,Gohara, Kazutoshi,Maeno, Zen,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
-
supporting information
p. 666 - 670
(2016/02/18)
-
- Silica supported palladium phosphine as a robust and recyclable catalyst for semi-hydrogenation of alkynes using syngas
-
This work reports a chemo-selective semi-hydrogenation of alkynes to alkenes using silica supported palladium phosphine catalyst with syngas (CO/H2). This developed methodology is an alternative to classical Lindlar catalyst for chemo-selective semi-hydrogenation of alkynes to alkenes. Various alkynes were smoothly convert to alkenes in 60-97% conversion with 85-98% selectivity. The prepared catalyst was well characterized by Field Emmission Gun Scanning Electron Microscopy (FEG-SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS), Inductively Coupled Plasma- Atomic Emmission Spectroscopy (ICP-AES) analysis techniques. In addition, catalyst was effectively recycled up to four consecutive run without significant loss in its catalytic activity and selectivity.
- Jagtap, Samadhan A.,Sasaki, Takehiko,Bhanage, Bhalchandra M.
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-
- Ligand-Controlled Cobalt-Catalyzed Transfer Hydrogenation of Alkynes: Stereodivergent Synthesis of Z- and E-Alkenes
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Herein, we report a novel cobalt-catalyzed stereodivergent transfer hydrogenation of alkynes to Z- and E-alkenes. Effective selectivity control is achieved based on a rational catalyst design. Moreover, this mild system allows for the transfer hydrogenation of alkynes bearing a wide range of functional groups in good yields using catalyst loadings as low as 0.2 mol %. The general applicability of this procedure is highlighted by the synthesis of more than 50 alkenes with good chemo- and stereoselectivity. A preliminary mechanistic study revealed that E-alkene product was generated via sequential alkyne hydrogenation to give Z-alkene intermediate, followed by a Z to E alkene isomerization process.
- Fu, Shaomin,Chen, Nan-Yu,Liu, Xufang,Shao, Zhihui,Luo, Shu-Ping,Liu, Qiang
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supporting information
p. 8588 - 8594
(2016/07/27)
-
- A Simple and Versatile Approach for the Fabrication of Paper-Based Nanocatalysts: Low Cost, Easy Handling, and Catalyst Recovery
-
A versatile method for the preparation of efficient and reusable nanocatalysts involving the painting of a commercial filter paper with a Pd@CNT (CNT=carbon nanotubes) ink was herein explored. The resulting paper-based material provided excellent results in the semihydrogenation of alkynes and alkynols and could be recycled at least five times without loss of activity or selectivity.
- Montiel, Laura,Delgado, Jorge A.,Novell, Marta,Andrade, Francisco J.,Claver, Carmen,Blondeau, Pascal,Godard, Cyril
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p. 3041 - 3044
(2016/10/11)
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- Cross-Linked "poisonous" Polymer: Thermochemically Stable Catalyst Support for Tuning Chemoselectivity
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Designed catalyst poisons can be deliberately added in various reactions for tuning chemoselectivity. In general, the poisons are "transient" selectivity modifiers that are readily leached out during reactions and thus should be continuously fed to maintain the selectivity. In this work, we supported Pd catalysts on a thermochemically stable cross-linked polymer containing diphenyl sulfide linkages, which can simultaneously act as a catalyst support and a "permanent" selectivity modifier. The entire surfaces of the Pd clusters were ligated (or poisoned) by sulfide groups of the polymer support. The sulfide groups capping the Pd surface behaved like a "molecular gate" that enabled exceptionally discriminative adsorption of alkynes over alkenes. H2/D2 isotope exchange revealed that the capped Pd surface alone is inactive for H2 (or D2) dissociation, but in the presence of coflowing acetylene (alkyne), it becomes active for H2 dissociation as well as acetylene hydrogenation. The results indicated that acetylene adsorbs on the Pd surface and enables cooperative adsorption of H2. In contrast, ethylene (alkene) did not facilitate H2-D2 exchange, and hydrogenation of ethylene was not observed. The results indicated that alkynes can induce decapping of the sulfide groups from the Pd surface, while alkenes with weaker adsorption strength cannot. The discriminative adsorption of alkynes over alkenes led to highly chemoselective hydrogenation of various alkynes to alkenes with minimal overhydrogenation and the conversion of side functional groups. The catalytic functions can be retained over a long reaction period due to the high thermochemical stability of the polymer.
- Yun, Seongho,Lee, Songhyun,Yook, Sunwoo,Patel, Hasmukh A.,Yavuz, Cafer T.,Choi, Minkee
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p. 2435 - 2442
(2016/04/26)
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- Direct Olefination of Alcohols with Sulfones by Using Heterogeneous Platinum Catalysts
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Carbon-supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant-free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt0 sites on the Pt metal particles are responsible for the rate-limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method. Olefination of alcohols: The first heterogeneous catalytic terminal and internal olefination of primary alcohols and methylenation of secondary alcohols with sulfones, a reusable carbon-supported Pt catalyst, and KOtBu is reported (see scheme).
- Hakim Siddiki,Touchy, Abeda Sultana,Kon, Kenichi,Shimizu, Ken-Ichi
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p. 6111 - 6119
(2016/04/26)
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- One-step Synthesis of Core-Gold/Shell-Ceria Nanomaterial and Its Catalysis for Highly Selective Semihydrogenation of Alkynes
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We report a facile synthesis of new core-Au/shell-CeO2 nanoparticles (Au@CeO2) using a redox-coprecipitation method, where the Au nanoparticles and the nanoporous shell of CeO2 are simultaneously formed in one step. The Au@CeO2 catalyst enables the highly selective semihydrogenation of various alkynes at ambient temperature under additive-free conditions. The core-shell structure plays a crucial role in providing the excellent selectivity for alkenes through the selective dissociation of H2 in a heterolytic manner by maximizing interfacial sites between the core-Au and the shell-CeO2.
- Mitsudome, Takato,Yamamoto, Masaaki,Maeno, Zen,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 13452 - 13455
(2015/11/10)
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- Copper-catalyzed selective semihydrogenation of terminal alkynes with hypophosphorous acid
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A novel copper-catalyzed selective semihydrogenation of terminal alkynes using hypophosphorous acid as hydrogen donor took place efficiently to afford the corresponding alkenes in high yields. A broad range of substituted terminal aromatic and aliphatic alkenes, including terminal dienes and enynes bearing internal triple bonds, can be efficiently synthesized by this reaction.
- Cao, Huanyang,Chen, Tieqiao,Zhou, Yongbo,Han, Daoqing,Yin, Shuang-Feng,Han, Li-Biao
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p. 765 - 769
(2014/04/03)
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- Colloid and nanodimensional catalysts in organic synthesis: VI.1 Hydrogenation and hydrogenolysis of carbonyl compounds
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Aldehydes and ketones are found to be hydrogenated to alcohols with hydrogen at atmospheric pressure under the catalysis with nickel nanoparticles. The reaction under study may be used as technologically available and cheap method for hydrogenation of carbonyl groups. It is found that in the case of aromatic ketones hydrogenolysis of C=O bond with partial hydrogenation of aromatic groups takes place.
- Mokhov,Popov,Nebykov
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p. 1656 - 1661
(2015/01/09)
-
- BMIm-PF6@SiO2 Microcapsules: Particulated ionic liquid as a new material for the heterogenization of catalysts
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A method for the preparation of silica microcapsules containing a high loading of ionic liquids (ILs) is described. The method paves the way to the conversion of ionic liquids into particulated materials, which results in ILs with new properties without changing their molecular structures. The synthesis of these new materials is based on the emulsification of ionic liquids in water, using surfactants or dispersants, and the resulting ionic liquid droplets are then confined in a silica shell formed via interfacial hydrolysis and polycondensation of tetraethoxysilane. This material can be isolated by centrifugation, followed by drying to yield a fine powder of ionic liquid-silica microcapsules, which are water and organic solvents redispersible. These new materials are utilized in the heterogenization of palladium catalyst and then applied in the hydrogenation of alkynes. The catalyst shows chemoselectivity in the hydrogenation of internal alkynes such as 4-octyne. Comparative studies have shown that the same catalyst loses this selectivity when it is applied under homogeneous conditions.
- Weiss, Ester,Dutta, Bishnu,Kirschning, Andreas,Abu-Reziq, Raed
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p. 4781 - 4787
(2014/11/07)
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- Role of polyaniline morphology in Pd particles dispersion. Hydrogenation of alkynes in the presence of Pd-polyaniline catalysts
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Two polyaniline (PANI) samples of various molecular masses were used for the preparation of palladium catalysts (with 2 mass % of Pd). The physicochemical features of starting polyanilines were found to substantially affect the size and extent of palladium nanoparticles aggregation. Strongly aggregated large palladium particles appeared in the PANI sample of more compact morphology (PANI-H), higher crystallinity and lower specific surface area. Pd nanoparticles of a definitively smaller size were formed in the more amorphous PANI sample of looser morphology (PANI-L) and the extent of particles aggregation was markedly lower. The catalytic properties of Pd/PANI samples were studied in a liquid phase hydrogenation of unsaturated triple bond (C≡C) in alkynes reactants, phenylacetylene, and cyclohexylacetylene. The 2 mass % Pd/PANI-L catalyst prepared using polymer of less compact texture exhibited much higher activity in both reactions. In the presence of the 2 mass % Pd/PANI-L catalyst, alkene products were formed with a high selectivity (approximately 90 %) attained at the almost complete conversion of alkynes. This highly selective hydrogenation of the C≡C to the C=C bond was related to the presence of an electroactive polymer, PANI, in close proximity with Pd active sites. Polyaniline could have a role in a steric effect as well as in a modification of adsorptive properties of Pd centres.
- Kosydar, Robert,Goral, Monika,Drelinkiewicz, Alicja,Stejskal, Jaroslav
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p. 1087 - 1095
(2013/07/26)
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- Method for Producing a Compound with a Double Bond
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A method is provided for highly selectively producing a compound with a double bond represented by formula (III), including the following steps: (A): reacting a compound represented by a ketone of formula (I) and/or a compound represented by an aralkyl alcohol of formula (II) with hydrogen in the presence of 0.1 parts by weight or more of a hydrogenation catalyst, thereby obtaining a reaction liquid,(B): removing the hydrogenation catalyst until the amount of the hydrogenation catalyst contained in the reaction liquid obtained in step (A) becomes 0.0010 parts by weight or less, thereby obtaining a hydrogenation catalyst-removed liquid,(C): obtaining a compound with a double bond represented by formula (III) in the presence of a dehydration catalyst from the hydrogenation catalyst-removed liquid obtained in step (B).
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Page/Page column 5
(2012/07/13)
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- Controlling the regioselectivity of the hydrosilylation reaction in carbon nanoreactors
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Hollow graphitized carbon nanofibres (GNF) are employed as nanoscale reaction vessels for the hydrosilylation of alkynes. The effects of confinement in GNF on the regioselectivity of addition to triple carbon-carbon bonds are explored. A systematic comparison of the catalytic activities of Rh and RhPt nanoparticles embedded in a nanoreactor with free-standing and surface-adsorbed nanoparticles reveals key mechanisms governing the regioselectivity. Directions of reactions inside GNF are largely controlled by the non-covalent interactions between reactant molecules and the nanofibre channel. The specific π-π interactions increase the local concentration of the aromatic reactant and thus promote the formation of the E isomer of the β-addition product. In contrast, the presence of aromatic groups on both reactants (silane and alkyne) reverses the effect of confinement and favours the formation of the Z isomer due to enhanced interactions between aromatic groups in the cis-orientation with the internal graphitic step-edges of GNF. The importance of π-π interactions is confirmed by studying transformations of aliphatic reactants that show no measurable changes in regioselectivity upon confinement in carbon nanoreactors. Nanoscale reaction vessels: Carbon nanoreactors are prepared by encapsulating catalytic Rh or RhPt nanoparticles in hollow graphitised nanofibres. Inside the nanoreactors, the pathways of the hydrosilylation reactions differ from those on the surface of nanofibres or in the bulk phase (see scheme). Copyright
- Solomonsz, William A.,Rance, Graham A.,Suyetin, Mikhail,La Torre, Alessandro,Bichoutskaia, Elena,Khlobystov, Andrei N.
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supporting information
p. 13180 - 13187
(2013/01/15)
-
- PROCESS FOR MAKING NITRILES
-
Adiponitrile is made by reacting 3-pentenenitrile with hydrogen cyanide. The 3- pentenenitrile is made by reacting 1,3-butadiene with hydrogen cyanide. The catalyst for the reaction of 1,3-butadiene with hydrogen cyanide to make 3-pentenenitrile is recycled. At least a portion of the recycled catalyst is purified by an extraction process, which separates catalyst degradation products and reaction byproduct from the catalyst.
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Page/Page column 86-88
(2012/02/01)
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- Synthesis and reactivity of rhodium mono-and bis(diolefin) complexes. Characterization of intermediates in the rhodium-catalyzed cyclotetramerization of butadiene
-
Rhodium bis(diolefin) complexes of the general composition [Rh(η4-diene)2(L)]X (diene = butadiene, isoprene, 2,3-dimethylbutadiene; L = PiPr3, PCy3, PtBu 2Me, AsiPr3, SbiPr3, CO,
- Bosch, Marco,Werner, Helmut
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body text
p. 5646 - 5660
(2011/01/11)
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- α-Selective Ni-catalyzed hydroalumination of aryl- and alkyl-substituted terminal alkynes: Practical syntheses of internal vinyl aluminums, halides, or boronates
-
A method for Ni-catalyzed hydroalumination of terminal alkynes, leading to the formation of α-vinylaluminum isomers efficiently (>98% conv in 2-12 h) and with high selectivity (95% to >98% α), is described. Catalytic α-selective hydroalumination reactions proceed in the presence of a reagent (diisobutylaluminum hydride; dibal-H) and 3.0 mol % metal complex (Ni(dppp)Cl2) that are commercially available and inexpensive. Under the same conditions, but with Ni(PPh3)2Cl2, hydroalumination becomes highly β-selective, and, unlike uncatalyzed transformations with dibal-H, generates little or no alkynylaluminum byproducts. All hydrometalation reactions are reliable, operationally simple, and practical and afford an assortment of vinylaluminums that are otherwise not easily accessible. The derived α-vinyl halides and boronates can be synthesized through direct treatment with the appropriate electrophiles [e.g., Br 2 and methoxy(pinacolato)boron, respectively]. Ni-catalyzed hydroaluminations can be performed with as little as 0.1 mol % catalyst and on gram scale with equally high efficiency and selectivity.
- Gao, Fang,Hoveyda, Amir H.
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supporting information; experimental part
p. 10961 - 10963
(2010/09/17)
-
- Nanoparticle-supported and magnetically recoverable nickel catalyst: A robust and economic hydrogenation and transfer hydrogenation protocol
-
A magnetic nanoparticle-supported leach-proof Ni catalyst was readily prepared from inexpensive starting materials which catalyzes various hydrogenation and transfer hydrogenation reactions; high catalytic activity and ease of recovery using an external magnetic field are additional eco-friendly attributes of this catalytic system.
- Polshettiwar, Vivek,Baruwati, Babita,Varma, Rajender S.
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experimental part
p. 127 - 131
(2010/04/22)
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- Hydroindation of allenes and its application to radical cyclization
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Hydroindation of allenes and radical cyclization of 1,2,7-trienes (allenenes) were accomplished by HInCl2 with high regioselectivity to afford a variety of cyclic compounds. The resulting vinylic indiums could be used for successive coupling reactions in a one-pot procedure. The use of HInCl2 generated slowly in situ is extremely effective for the radical cyclization. The Royal Society of Chemistry.
- Hayashi, Naoki,Hirokawa, Yusuke,Shibata, Ikuya,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 1949 - 1954
(2009/01/31)
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- Only para-hydrogen spectroscopy (OPSY), a technique for the selective observation of para-hydrogen enhanced NMR signals
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An NMR method is reported for the efficient removal of signals derived from nuclei with thermally equilibrated spin state populations whilst leaving, intact, signals derived from para-hydrogen induced polarisation (PHIP) through gradient assisted coherence selection. The Royal Society of Chemistry.
- Aguilar, Juan A.,Elliott, Paul I. P.,Lopez-Serrano, Joaquin,Adams, Ralph W.,Duckett, Simon B.
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p. 1183 - 1185
(2008/02/02)
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- METHOD FOR PRODUCING ETHERS
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Disclosed is a method for producing ethers which is characterized in that a telomerization reaction of a conjugated diene compound in the presence of a hydroxyl compound represented by the following general formula (I): R1OH, is firstly perf
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Page/Page column 15
(2008/06/13)
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- PROCESS FOR THE CARBONYLATION OF A CONJUGATED DIENE
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A process for the carbonylation of a conjugated diene, comprising reacting the conjugated diene with carbon monoxide and a co-reactant having an active hydrogen atom in the presence of a catalyst system including: (a) a source of palladium; and (b) a bidentate diphosphine ligand of formula (II): R1 > P1 -R- P2 2R3 wherein P1 and p2 represent phosphorus atoms; R1 represents an optionally substituted divalent organic group linked to the phosphorus atom by two tertiary carbon atoms; and R2 and R3 independently represent univalent groups of from 1 to 20 atoms containing a tertiary carbon atom through which each group is linked to the phosphorus atom, or R2 and R3 jointly form an optionally substituted divalent organic group containing at least 2 tertiary carbon atoms through which the group is linked to the phosphorus atom; and R represents a divalent bridging group comprising 3 atoms through which P1 is linearly connected to P2;and (c) a source of an anion.
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Page/Page column 15-17
(2010/02/13)
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- Structural characterization and catalytic activity of the rhodium-carbene complex Rh(PPh3)2(IMes)Cl (IMes = bis(1,3-(2,4,6-trimethylphenyl)imidazol-2-ylidene)
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The rhodium-carbene complex Rh(PPh3)2(IMes)Cl (2) is an active catalyst for the hydroboration of simple olefins at room temperature. The reactivity of 2 was also tested in the methylenation of aldehydes. The crystal structure of 2 is
- Grasa, Gabriela A.,Moore, Zakhia,Martin, Kenneth L.,Stevens, Edwin D.,Nolan, Steven P.,Paquet, Valérie,Lebel, Hélène
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p. 126 - 131
(2007/10/03)
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- One-pot transformation of RCHO to (E)-RCH=CHSiMe3 using CHI3, Mn, Me3SiCl, and a catalytic amount of CrCl2
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Iodoform is reduced with manganese in the presence of Me3SiCl to give Me3SiCHI2 (1). A one-pot transformation of aldehydes to (E)-1- alkenyltrimethylsilanes is then performed with iodoform, manganese, Me2SiCl, and a catalytic amount of chromium(II) chloride in THF via in situ formation of 1.
- Takai, Kazuhiko,Hikasa, Shintaro,Ichiguchi, Tetsuya,Sumino, Naoki
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p. 1769 - 1771
(2007/10/03)
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- Stereoselective synthesis of homochiral (E)-vinyl phosphonates derived from (-)-ephedrine
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A new synthesis of homochiral vinyl phosphonates starting from 1-alkynes is described. The title compounds were obtained in good yields by the reaction of chiral 2-chloro-1,3,2-oxazaphospholidin-2-one (1) with the 'ate'-complexes of vinyl alanes. The latter were prepared by zirconocene dichloride catalyzed hydroalumination of 1-alkynes with diisobutyl aluminum hydride (DIBAH).
- Taapken, Thomas
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p. 6659 - 6662
(2007/10/02)
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- Kinetics of the Thermal Isomerizations of Gaseous Cycloheptene and Cyclooctene
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Single-pulse shock tube kinetic studies of the thermal isomerizations of gaseous cycloheptene (CHEP) and cis-cyclooctene (COCT), and static reactor isomerizations of COCT at lower temperatures, have revealed a mechanistic dissimilarity in the two superficially analogous cycloalkene to, α,ω-alkadiene reactions observed.At 1035-1256 K, CHEP produced mostly vinylcyclopentane, log10(k,s-1) = 15.1 (+/- 0.7) - 69.7 (+/- 3.3) x 103/4.576T, and some 1,6-heptadiene.From COCT, heated over the range 610-1091 K, the dominant product was 1,7-octadiene, log10(k,s-1) = 13.8 (+/- 0.2) -54.6 (+/- 0.5) x 103/4.576T, with small amounts of vinylcyclohexane formed at the higher temperatures, log10(k,s-1) = 15.2 (+/- 0.3) - 64.4 (+/- 1.2) x 103/4.576T.The activation energy for the COCT isomerization to 1,7-octadiene is too low to associate with formation of a diradical, but is consistent with a concerted retro-ene mechanism.The higher activation energy isomerization to vinylcyclohexane, however, passes through a diradical transition structure.In contrast, the structure of CHEP is not adaptable to a concerted retro-ene precess, and both 1,6-heptadiene and vinylcyclopentane are formed through diradical-mediated reactions.
- Kalra, Bansi L.,Afriyie, Yau,Brandt, Benjamin,Lewis, David K.,Baldwin, John E.
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p. 8142 - 8146
(2007/10/02)
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- Laser-Powered Decomposition of Spiroalkanes (n = 2-5)
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The laser heating of spiroalkanes (n=2-5) and of their 1,1,2,2-tetradeuterated isotopomers reveals dissimilar modes of their thermal decomposition.Spiropentane decomposes into ethene and propadiene via two competing routes: the direct cleavage and the more important cleavage via intermediary methylenecyclobutane.Spirohexane decomposes through two important concurrent pathways which are the expulsions of ethene from the three-membered ring and a more feasible expulsion of ethene from the four-membered ring.Spiroheptane and spirooctane decompose by a radical-chain mechanism and afford complex mixtures of products; upon addition of propene both compounds rearrange into two cycloalkanes wherein the larger ring of the spiroalkane is preserved and substituted with ethylidene and a vinyl group.
- Fajgar, Radek,Pola, Josef
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p. 7709 - 7717
(2007/10/02)
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- Hindered organoboron groups in organic chemistry. 24. The condensation of aliphatic aldehydes with dimesitylboron stabilised carbanions to give ketones
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The condensation of boron stabilised carbanions, MeS2BCHLiR1, (R1≠H) with aliphatic aldehydes, R2CHO, followed by treatment with trifluoroacetic anhydride (TFAA) or N-chlorosuccinimide (NCS) is an unique, broadly applicable redox process that yields ketones, R1CH2COR2, directly and in high yields. The anion MeS2BCH2Li (MeS2BCHLiR1, R1=H) gives high yields of alkenes, R2CH=CH2 in the same conditions.
- Pelter, Andrew,Smith, Keith,Elgendy, Said M. A.,Rowlands, Martin
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p. 7104 - 7118
(2007/10/02)
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- Synthetically Useful β-Lithioalkoxides from Reductive Lithiation of Epoxides by Aromatic Radical Anions
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Epoxides are reductively cleaved by means of lithium 4,4'-di-tert-butylbiphenylide.Ethylene oxide itself cleaves to lithium 2-lithioethoxide (15) in less than 5 min at -95 deg C.Epoxides possessing one unsubstituted carbon atom reduce in a matter of minutes at -78 deg C.When both carbon atoms are monosubstituted, at least 1 h is required.Epoxides with one or with two geminal saturated substituents open mainly between the oxygen atom and the least substituted carbon atom.Ring opening in the other direction leads to an unstable β-lithioalkoxide which very rapidly forms an olefin.Acyclic 1,2-disubstituted epoxides yield only olefins.Cyclooctene oxide produces, after protonation, a 3:7 ratio of cyclooctanol and cyclooctene.Cyclohexene oxide gives a 3:1 ratio of cyclohexanol and cyclohexene.Vinyloxiranes, on the other hand, open at the most substituted C-O bond to produce an allylic anion associated with an alkoxide.The carbanionic centers of the resulting dianions add to the carbonyl groups of aldehydes and ketones; however, when a hydrogen atom is present on the carbon atom which is attached to both negatively charged atoms, some reduction of the carbonyl group competes with the nucleophilic addition.The allylic anions derived from vinyloxiranes, after treatment with titanium tetraisopropoxide or cerium(III) chloride, add to aldehydes mainly at the most or least substituted terminus, respectively.In the former case, the configuration of the resulting glycols is predominantly anti.A number of adducts of the dianions with conjugated unsaturated aldehydes and ketones can be converted to unsaturated cyclic 6-membered ring ethers in the presence of acid or methanesulfonyl chloride.
- Cohen, Theodore,Jeong, In-Howa,Mudryk, Boguslaw,Bhupathy, M.,Awad, Mohamed M. A.
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p. 1528 - 1536
(2007/10/02)
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- Rotational Barriers of Strained Olefines
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For the olefins 1-8 heats of formation have been derived from heats of hydrogenation and force-field calculations, respectively.From the kinetics of their geometrical isomerisation the corresponding values for the transition states were obtained.The rotational barriers, which vary by nearly 30 kcal/mol, can be described by a unique torsional potential (65.9 +/- 0.9 kcal/mol), which is independent of the degree of substitution, if a correction is made for the steric energy contribution in the ground- and transition-states. - Key Words: Rotational barriers / Olefins, strained / Heat of Hydrogenation / Force-field calculation
- Doering, William v. E.,Roth, Wolfgang R.,Bauer, Frank,Breuckmann, Rolf,Ebbrecht, Thomas,at al.
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p. 1263 - 1276
(2007/10/02)
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- Photochemical Dehydrogenation of Alkanes Catalyzed by trans-Carbonylchlorobis(trimethylphosphine)rhodium: Aspects of Selectivity and Mechanism
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The photochemical dehydrogenation of alkanes is catalyzed in solution by trans-Rh(PMe3)2(CO)Cl with high efficiency; quantum yields up to 0.10 and turnover numbers as high as 5000 are achieved with cyclooctane as substrate.The intramolecular regioselectivity of the reaction is investigated with methyl-, ethyl-, and isopropylcyclohexane.In competition experiments, cyclooctane is found to be 17 times as reactive as cyclohexane; under carbon monoxide atmosphere, the selectivity is enhanced to a factor of 130.A kinetic isotope effect, kH/kD=5.3, is found for thedehydrogenation of C6H12/C6D12.Both intra- and intermolecular selectivities are consistent with a pathway involving a reversible C-H oxidative addition followed by a β-hydrogen elimination. trans-Rh(PMe3)2(CO)Cl is demonstrated to be the only significant photoactive species in solution.The dehydrogenation reaction is quenched by carbon monoxide with Stern-Volmer kinetics.On the basis of these results, a mechanism is proposed in which the enrgy needed to drive these thermodynamically unfavorable dehydrogenations is obtained only from Rh-CO bond photolysis.
- Maguire, John A.,Boese, William T.,Goldman, Alan S.
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p. 7088 - 7093
(2007/10/02)
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- HINDERED ORGANOBORON GROUPS IN ORGANIC SYNTHESIS. 14. STEREOSELECTIVE SYNTHESIS OF ALKENES BY THE BORON-WITTIG REACTION USING ALIPHATIC ALDEHYDES
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In the presence of HX, carbanions Mes2BCHLiR1 react with aliphatic aldehydes to give alkenes.The stereochemistry of product alkene depends upon the nature of HX.
- Pelter, Andrew,Smith, Keith,Elgendy, Said,Rowlands, Martin
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p. 5647 - 5650
(2007/10/02)
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- Organic Reactions in Liquid-Crystalline Solvents. 9. Investigation of the Solubilization of Guest Molecules in a Smectic (Crystal-B) Liquid Crystal by Deuterium NMR, Calorimetry, Optical Microscopy, and Photoreactivity Methods.
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The solubilization behavior of three aromatic ketones in the smectic (crystal-B) and nematic liquid-crystalline phases of trans,trans-4'-butylbicyclohexyl-4-carbonitrile (CCH-4) has been studied in detail by 2H NMR spectroscopy, differential scanning calorimetry (DSC), and thermal microscopy, and complete binary phase diagrams for each ketone/CCH-4 system have been constructed.Combined with previously reported data, the results indicate that most aromatic molecules have very low solubilities (ca. 0.2-2.0 molpercent) in the crystal-B phase of this mesogen.For a given solute, solubility in this phase increases with decreasing temperature.For bulk compositions above the solubility limit, the solute order parameters (from NMR) appear to decrease with decreasing temperature.This has been shown to be due to phase separation and the complex temperature-dependent behavior of the resulting smectic/nematic biphasic system.Other evidence indicates that the isotropic NMR behavior observed for many solute/CCH-4 mixtures at low temperatures is due to the formation of a smetic/isotropic biphasic system, not a plastic or cubic phase as has been proposed previously.The Norrish type II photoreactivity at 30 deg C and the 2H NMR behavior of γ-cyclohexylbutyrophenone-α,α-d2 over the 30-80 deg C range in CCH-4 have been investigated over a wide range of sample composition (0.6-40 molpercent).The results obtained in the temperature range below the S-N transition of the pure liquid crystal can be explained within the context of a biphasic solubilization model.
- Fahie, Brian J.,Mitchell, D. Scott,Workentin, Mark. S.,Leigh, William J.
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p. 2916 - 2929
(2007/10/02)
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- Electron-transfer processes. 43. Attack of alkyl radicals upon 1-alkenyl and 1-alkynyl derivatives of tin and mercury
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Alkyl radicals, obtained by reaction of Bu3Sn? or ClHg? with alkylmercury halides, will undergo regioselective and in some cases stereospecific substitution by a free radical chain addition-elimination mechanism with 1-alkenylstannanes or -mercurials. The chain reaction is also observed for 1-alkynyl derivatives and in the photostimulated demercuration of mixed alkyl and 1-alkenyl- or 1-alkynylmercurials. Chain propagation with alkyl radical formation is also observed to occur in the reactions of β-eliminated ClHg? with Grignard reagents in PhH-THF solution. In competitive reactions of Bu3Sn? or ClHg? with pairs of alkylmercury chlorides, it is observed that a tert-butylmercurial is >1000 times more reactive than a n-butylmercurial, suggesting a concerted dissociate electron-transfer process not involving the intermediacy of RHg? species.
- Russell, Glen A.,Ngoviwatchai, Preecha,Tashtoush, Hasan I.
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p. 696 - 702
(2008/10/08)
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- Reactions of Alkylmercurials with Heteroatom-Centered Acceptor Radicals
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The relative reactivities of alkylmercury halides toward PhS., PhSe., or I. decrease drastically from R = tert-butyl to R = sec-alkyl to R = n-butyl, indicative that R. is formed in the rate-determining step in the attack of these radicals upon RHgCl.The alkyl radicals thus formed will enter into chain reactions in which a heteroatom-centered radical (A.) is regenerated from substrates such as RS-SR, ArSe-SeAr, ArTe-TeAr, PhSe-SO2Ar, Cl-SO2Ph; ZCH=CHA (A = Cl, I, SPh, SO2Ph); or PhCCHA (A = I, SPh, SO2Ph). β-Styrenyl (PhCH=CHA, Ph2C=CHA) and β-phenethynyl (PhCCA) systems with A = I, Br, SO2Ph also enter into chain reactions with mercury(II) salts with the ligands PhS, PhSe, PhSO2, or (EtO)2PO.The relative reactivities of a series of reagents toward t-Bu. and of PhCH=CHA, Ph2C=CHA, and PhCCA toward c-C6H11. are reported as well as the regioselectivity of t-Bu. attack observed for 1,2-disubstituted ethylenes (ZCH=CHA) with Z and A from the group Ph, Cl, Br, I, SO2Ph, SPh, Bu3Sn.Reactions of (E)- and (Z)-PhCH=CHI or MeO2CCH=CHI with t-Bu. or c-C6H11. occurred in a regioselective and stereospecific (retention) manner.Reactions of (E)- and (Z)-ClCH=CHCl occurred in a nonstereospecific manner in which the E/Z product ratio increased with the bulk of the attacking radical.A similar effect on the E/Z product ratios was observed for (Z)-MeO2CCH=CHCl.
- Russell, Glen A.,Ngoviwatchai, Preecha,Tashtoush, Hasan I.,Pla-Dalmau, Anna,Khanna, Rajive K.
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p. 3530 - 3538
(2007/10/02)
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- Electrophilic Cleavage of Cyclopropanes. Acetolysis of Bicyclic and Tricyclic Cyclopropanes
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The acetolysis of a series of bicycloalkanes and propellanes has been studied.The effect of ring strain, caused by changing ring size or introducing a trans-ring fusion, on the rate and products of the reaction has been examined.No correlation was found between rates of acetolysis and strain energy relief, but with the exception of propellane, there is a rough correlation with ionization potentials.The degree of polarization of the C-C bonds in the presence of a proton correlates very well with reactivity and is a controlling factor for the acetolysis rates.The importance of the energies of unoccupied orbitals with the appropriate symmetry in controlling electron polarization is shown by the large difference in rate of reaction between - and propellanes.
- Wiberg, Kenneth B.,Kass, Steven R.,Meijere, Armin de,Bishop, K. C.
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p. 1003 - 1007
(2007/10/02)
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