- Synthesis of Racemic Brevioxime and Related Model Compounds
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The synthesis, in racemic form, of the insect juvenile hormone inhibitor brevioxime (1) is described, as well as exploratory studies that led to the related model compounds 14 and 15a. The route to 1 involves Ag+-mediated coupling of the amine derived from 20 with the β-keto thioester 32. Acid treatment of the coupled product 33 led by acetal hydrolysis, cyclization, and desilylation to 34a,b, from which 1 was reached by oxidation and conversion into the oxime. In the synthesis of the amino component 20, a known, but unusual, reduction was used for converting a nitrile into an amine hydrochloride.
- Clive, Derrick L. J.,Hisaindee, Soleiman
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Read Online
- Migratory Hydrogenation of Terminal Alkynes by Base/Cobalt Relay Catalysis
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Migratory functionalization of alkenes has emerged as a powerful strategy to achieve functionalization at a distal position to the original reactive site on a hydrocarbon chain. However, an analogous protocol for alkyne substrates is yet to be developed. Herein, a base and cobalt relay catalytic process for the selective synthesis of (Z)-2-alkenes and conjugated E alkenes by migratory hydrogenation of terminal alkynes is disclosed. Mechanistic studies support a relay catalytic process involving a sequential base-catalyzed isomerization of terminal alkynes and cobalt-catalyzed hydrogenation of either 2-alkynes or conjugated diene intermediates. Notably, this practical non-noble metal catalytic system enables efficient control of the chemo-, regio-, and stereoselectivity of this transformation.
- Liu, Bingxue,Liu, Qiang,Liu, Xufang
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p. 6750 - 6755
(2020/03/13)
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- Cobalt-Catalyzed Intermolecular Hydrofunctionalization of Alkenes: Evidence for a Bimetallic Pathway
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A functional group tolerant cobalt-catalyzed method for the intermolecular hydrofunctionalization of alkenes with oxygen- and nitrogen-based nucleophiles is reported. This protocol features a strategic use of hypervalent iodine(III) reagents that enables a mechanistic shift from conventional cobalt-hydride catalysis. Key evidence was found supporting a unique bimetallic-mediated rate-limiting step involving two distinct cobalt(III) species, from which a new carbon-heteroatom bond is formed.
- Zhou, Xiao-Le,Yang, Fan,Sun, Han-Li,Yin, Yun-Nian,Ye, Wei-Ting,Zhu, Rong
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supporting information
p. 7250 - 7255
(2019/05/16)
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- Total Synthesis and Biological Evaluation of Siladenoserinol A and its Analogues
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The total synthesis of siladenoserinol A, an inhibitor of the p53–Hdm2 interaction, has been achieved. AuCl3-catalyzed hydroalkoxylation of an alkynoate derivative smoothly and regioselectively proceeded to afford a bicycloketal in excellent yield. A glycerophosphocholine moiety was successfully introduced through the Horner–Wadsworth–Emmons reaction using an originally developed phosphonoacetate derivative. Finally, removal of the acid-labile protecting groups, followed by regioselective sulfamate formation of the serinol moiety afforded the desired siladenoserinol A, and benzoyl and desulfamated analogues were also successfully synthesized. Biological evaluation showed that the sulfamate is essential for biological activity, and modification of the acyl group on the bicycloketal can improve the inhibitory activity against the p53–Hdm2 interaction.
- Yoshida, Masahito,Saito, Koya,Kato, Hikaru,Tsukamoto, Sachiko,Doi, Takayuki
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supporting information
p. 5147 - 5150
(2018/03/26)
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- Rhenium-catalyzed deoxydehydration of renewable triols derived from sugars
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An efficient method for the catalytic deoxydehydration of renewable triols, including those obtained from 5-HMF, is described. The corresponding unsaturated alcohols were obtained in good yields using simple rhenium(vii)oxide under neat conditions and ambient atmosphere at 165 °C.
- Wozniak, Bartosz,Li, Yuehui,Tin, Sergey,De Vries, Johannes G.
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supporting information
p. 4433 - 4437
(2018/10/17)
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- Pd(II)-Catalyzed [4 + 2] Heterocyclization Sequence for Polyheterocycle Generation
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A new Pd(II)-catalyzed cascade sequence for the formation of polyheterocycles, from simple starting materials, is reported. The sequence is applicable to both indole and pyrrole substrates, and a range of substituents are tolerated. The reaction is thought to proceed by a Pd(II)-catalyzed C-H activated Heck reaction followed by a second Pd(II)-catalyzed aza-Wacker reaction with two Cu(II)-mediated Pd(0) turnovers per sequence. The sequence can be considered a formal [4 + 2] heterocyclization.
- Glaisyer, Elizabeth L.,Watt, Michael S.,Booker-Milburn, Kevin I.
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supporting information
p. 5877 - 5880
(2018/09/25)
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- Reactions of 2-Methyltetrahydropyran on Silica-Supported Nickel Phosphide in Comparison with 2-Methyltetrahydrofuran
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The reactions of 2-methyltetrahydropyran (2-MTHP, C6H12O) on Ni2P/SiO2 provide insights on the interactions between a cyclic ether, an abundant component of biomass feedstock, with a transition-metal phosphide, an effective hydrotreating catalyst. At atmospheric pressure and a low contact time, conditions similar to those of a fast pyrolysis process, 70% of products formed from the reaction of 2-MTHP on Ni2P/SiO2 were deoxygenated products, 2-hexene and 2-pentenes, indicating a good oxygen removal capacity. Deprotonation, hydrogenolysis, dehydration, and decarbonylation were the main reaction routes. The reaction sequence started with the adsorption of 2-MTHP, followed by ring-opening steps on either the methyl substituted side (Path I) or the unsubstituted side (Path II) to produce adsorbed alkoxide species. In Path I, a primary alkoxide was oxidized at the α-carbon to produce an aldehyde, which subsequently underwent decarbonylation to 2-pentenes. The primary alkoxide could also be protonated to give a primary alcohol which could desorb or form the final product 2-hexene. In Path II, a secondary alkoxide was oxidized to produce a ketone or was protonated to a secondary alcohol that was dehydrated to give 2-hexene. The active sites for the adsorption of 2-MTHP and O-intermediates were likely to be Ni sites.
- Bui, Phuong P.,Oyama, S. Ted,Takagaki, Atsushi,Carrow, Brad P.,Nozaki, Kyoko
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p. 4549 - 4558
(2016/07/12)
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- On the Functional Group Tolerance of Ester Hydrogenation and Polyester Depolymerisation Catalysed by Ruthenium Complexes of Tridentate Aminophosphine Ligands
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The synthesis of a range of phosphine-diamine, phosphine-amino-alcohol, and phosphine-amino-amide ligands and their ruthenium(II) complexes are reported. Five of these were characterised by X-ray crystallography. The activities of this collection of catalysts were initially compared for the hydrogenation of two model ester hydrogenations. Catalyst turnover frequencies up to 2400 h-1 were observed at 85 °C. However, turnover is slow at near ambient temperatures. By using a phosphine-diamine RuII complex, identified as the most active catalyst, a range of aromatic esters were reduced in high yield. The hydrogenation of alkene-, diene-, and alkyne-functionalised esters was also studied. Substrates with a remote, but reactive terminal alkene substituent could be reduced chemoselectively in the presence of 4-dimethylaminopyridine (DMAP) co-catalyst. The chemoselective reduction of the ester function in conjugated dienoate ethyl sorbate could deliver (2E,4E)-hexa-2,4-dien-1-ol, a precursor to leaf alcohol. The monounsaturated alcohol (E)-hex-4-en-1-ol was produced with reasonable selectivity, but complete chemoselectivity of C=O over the diene is elusive. High chemoselectivity for the reduction of an ester over an alkyne group was observed in the hydrogenation of an alkynoate for the first time. The catalysts were also active in the depolymerisation reduction of samples of waste poly(ethylene terephthalate) (PET) to produce benzene dimethanol. These depolymerisations were found to be poisoned by the ethylene glycol side product, although good yields could still be achieved. A simple catalyst for difficult reductions: Ruthenium complexes of P,N,N and P,N,O ligands catalyse the reduction of esters with high activities. The Ru complex of a phosphine-diamine ligand (see scheme) has been found to be a good catalyst for reducing alkene-, diene-, and alkyne-functionalised esters, displaying good activity and chemoselectivity. This catalyst was also active in the hydrogenation of waste poly(ethylene terephthalate) (PET).
- Fuentes, José A.,Smith, Samuel M.,Scharbert, M. Theresa,Carpenter, Ian,Cordes, David B.,Slawin, Alexandra M. Z.,Clarke, Matthew L.
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supporting information
p. 10851 - 10869
(2015/07/20)
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- Highly functionalized and potent antiviral cyclopentane derivatives formed by a tandem process consisting of organometallic, transition-metal-catalyzed, and radical reaction steps
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A simple modular tandem approach to multiply substituted cyclopentane derivatives is reported, which succeeds by joining organometallic addition, conjugate addition, radical cyclization, and oxygenation steps. The key steps enabling this tandem process are the thus far rarely used isomerization of allylic alkoxides to enolates and single-electron transfer to merge the organometallic step with the radical and oxygenation chemistry. This controlled lineup of multiple electronically contrasting reactive intermediates provides versatile access to highly functionalized cyclopentane derivatives from very simple and readily available commodity precursors. The antiviral activity of the synthesized compounds was screened and a number of compounds showed potent activity against hepatitisC and dengue viruses.
- Jagtap, Pratap R.,Ford, Leigh,Deister, Elmar,Pohl, Radek,Cisarova, Ivana,Hodek, Jan,Weber, Jan,Mackman, Richard,Bahador, Gina,Jahn, Ullrich
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supporting information
p. 10298 - 10304
(2014/08/18)
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- Alkene isomerisation catalysed by a ruthenium PNN pincer complex
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The [Ru(CO)H(PNN)] pincer complex based on a dearomatised PNN ligand (PNN: 2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) was examined for its ability to isomerise alkenes. The isomerisation reaction proceeded under mild conditions after activation of the complex with alcohols. Variable-temperature (VT) NMR experiments to investigate the role of the alcohol in the mechanism lend credence to the hypothesis that the first step involves the formation of a rearomatised alkoxide complex. In this complex, the hemilabile diethylamino side-arm can dissociate, allowing alkene binding cis to the hydride, enabling insertion of the alkene into the metal-hydride bond, whereas in the parent complex only trans binding is possible. During this study, a new uncommon Ru0 coordination complex was also characterised. The scope of the alkene isomerisation reaction was examined. The catalyst tested positive! A dearomatised ruthenium PNN (2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) pincer complex, [Ru(CO)H(PNN)], was evaluated as an alkene isomerisation catalyst. The isomerisation reaction was greatly accelerated by the addition of alcohols, in particular isopropanol. Isomerisation of terminal to internal alkenes took place at room temperature. A mechanism was proposed based on variable-temperature NMR spectroscopy.
- Perdriau, Sébastien,Chang, Mu-Chieh,Otten, Edwin,Heeres, Hero J.,De Vries, Johannes G.
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supporting information
p. 15434 - 15442
(2016/02/18)
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- Iron(III) chloride-benzotriazole adducts with trigonal bipyramidal geometry: Spectroscopic, structural and catalytic studies
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The reactions of FeCl3 with benzotriazole (btaH), 1-methylbenzotriazole (Mebta), 5,6-dimethylbenzotriazole (5,6Me2btaH) and 5-chlorobenzotriazole (5ClbtaH) were studied in non-polar solvents. The new solid complexes [FeCl3(btaH)2] (1), [FeCl 3(Mebta)2] (2), [FeCl3(5,6Me 2btaH)2] (3) and [FeCl3(5ClbtaH) 2]·2(5ClbtaH) (4) have been isolated. The structures of the complexes have been determined by single-crystal, X-ray crystallography. The structures of 1-4 consist of mononuclear, high-spin 5-coordinate molecules; in addition, the crystal structure of 4 contains two lattice 5ClbtaH molecules per [FeCl3(5ClbtaH)2] unit. The coordinated benzotriazole molecules behave as monodentate ligands with their ligated atom being the nitrogen of the position 3 of the azole ring. The geometry at iron(III) is trigonal bipyramidal with the chlorido ligands occupying the equatorial sites. The crystal structures of the complexes are stabilized by stacking interactions and H bonds (for 1, 3 and 4 only). The new complexes were characterized by elemental analyses, magnetic susceptibilities at room temperature and spectroscopic (IR, far-IR, solid-state electronic UV/VIS/near-IR, 57Fe-Mo?ssbauer, EPR only for complex 4) methods. All data are discussed in terms of the nature of bonding and the known structures. Complexes 1, 2 and 4 have been tested as homogeneous (MeCN) oxidation catalysts in the presence of the "green" H2O2 oxidant; they display moderate to high catalytic activity in the oxidation of several alkenes, cyclohexane and n-hexane, which is described in detail.
- Anastasiadis, Nikolaos C.,Bilis, George,Plakatouras, John C.,Raptopoulou, Catherine P.,Psycharis, Vassilis,Beavers, Christine,Teat, Simon J.,Louloudi, Maria,Perlepes, Spyros P.
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p. 189 - 202
(2013/10/08)
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- Control of the selectivity in multi-functional group molecules using supported gold-palladium nanoparticles
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The oxidation of 2-hexen-1-ol and 1-hexen-3-ol with air has been studied using supported gold, palladium and gold-palladium catalysts. The main aim was to determine if either the alcohol or alkene functional group can be oxidised selectively. However, based on the reaction products observed (2-hexen-1-ol forms 2-hexene, hexanal, (E)-2-hexenal, (E)-3-hexen-1-ol, 4-hexen-1-ol and (E)-2-hexanoic acid. 1-Hexen-3-ol forms 1-hexene, 3-hexanone, 1-hexen-3-one and 3-hexenol), the main pathway in these reactions is isomerisation and, in addition, significant yields of the products are due to a disproportionation reaction. Controlling the selectivity in molecules with multiple function groups by manipulating the catalyst composition and reaction conditions can promote or hinder the various reaction pathways, thereby increasing the selectivity to the desired oxidation products.
- Alshammari, Hamed,Miedziak, Peter J.,Morgan, David J.,Knight, David W.,Hutchings, Graham J.
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p. 1244 - 1254
(2013/06/26)
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- A biocatalytic hydrogenation of carboxylic acids
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The hyperthermophile Pyrococcus furiosus catalyses the hydrogenation of a broad range of carboxylic acids selectively to the corresponding primary alcohols. Other functional groups such as isolated CC-double bonds are not touched. The chemoselectivity of the carboxylate reduction may be directed towards aldehydes by simple medium engineering.
- Ni, Yan,Hagedoorn, Peter-Leon,Xu, Jian-He,Arends, Isabel W. C. E.,Hollmann, Frank
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supporting information
p. 12056 - 12058
(2013/01/16)
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- Vapor-phase catalytic dehydration of terminal diols
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Vapor-phase catalytic reactions of several terminal diols were investigated over several rare earth oxides, such as Sc2O3, Y 2O3, CeO2, Yb2O3, and Lu2O3. Sc2O3 showed selective catalytic activity in the dehydration of terminal diols with long carbon chain, such as 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,12-dodecanediol, to produce the corresponding unsaturated alcohols. In the dehydration of 1,6-hexanediol, 5-hexen-1-ol was produced with selectivity over 60 mol%, together with by-products such as ε-caprolactone and oxacycloheptane. In the dehydration of 1,10-decanediol, 9-decen-1-ol was produced with selectivity higher than 70 mol%. In addition to Sc 2O3, heavy rare earth oxides such as Lu2O 3 as well as monoclinic ZrO2 showed moderate selectivity in the dehydration of the terminal diols.
- Abe, Katsutoshi,Ohishi, Yusuke,Okada, Takuto,Yamada, Yasuhiro,Sato, Satoshi
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experimental part
p. 419 - 424
(2012/02/03)
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- Mechanistic studies of wacker-type intramolecular aerobic oxidative amination of alkenes catalyzed by Pd(OAc)2/pyridine
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Wacker-type oxidative cyclization reactions have been the subject of extensive research for several decades, but few systematic mechanistic studies of these reactions have been reported. The present study features experimental and DFT computational studies of Pd(OAc)2/pyridine-catalyzed intramolecular aerobic oxidative amination of alkenes. The data support a stepwise catalytic mechanism that consists of (1) steady-state formation of a PdII-amidate-alkene chelate with release of 1 equiv of pyridine and AcOH from the catalyst center, (2) alkene insertion into a Pd-N bond, (3) reversible β-hydride elimination, (4) irreversible reductive elimination of AcOH, and (5) aerobic oxidation of palladium(0) to regenerate the active trans-Pd(OAc)2(py)2 catalyst. Evidence is obtained for two energetically viable pathways for the key C-N bond-forming step, featuring a pyridine-ligated and a pyridine-dissociated PdII species. Analysis of natural charges and bond lengths of the alkene-insertion transition state suggest that this reaction is best described as an intramolecular nucleophilic attack of the amidate ligand on the coordinated alkene.
- Ye, Xuan,Liu, Guosheng,Popp, Brian V.,Stahl, Shannon S.
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experimental part
p. 1031 - 1044
(2011/04/19)
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- Asymmetric iodocyclization catalyzed by salen-CrIIICl: Its synthetic application to swainsonine
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The previously developed enantioselective iodocyclization of γ-hydroxy-cis-alkenes required 30 mol% of (R,R)-salen-CoII complex as chiral catalyst and 0.75 equivalent of N-chlorosuccinimide (NCS) as activator to produce 2-substituted tetrahydrofurans with 61 to 90% ee. Due to the considerable loading amount of the CoII complex, another more effective catalyst was pursued by screening (R,R)-salentransition metal complexes. When 10 mol % of the catalysts were applied with 0.5 equivalent of NCS, a higher level of stereoselectivity was attained with the corresponding CrIIICl (84% ee), MnIICl (52% ee) and CoII complexes (66% ee). Refinement of the conditions established a novel catalytic enantioselective iodocyclization protocol using iodine in the presence of 7 mol% of (R,R)-salen-CrIIICl complex activated by 0.7 equivalent of NCS in toluene to induce 74 to 93 % ee.
- Kwon, Hyo Young,Park, Chul Min,Lee, Sung Bae,Youn, Joo-Hack,Kang, Sung Ho
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p. 1023 - 1028
(2008/09/21)
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- Development of isomerization and cycloisomerization with use of a ruthenium hydride with N-heterocyclic carbene and its application to the synthesis of heterocycles
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A pure ruthenium hydride complex with N-heterocyclic carbene (NHC) ligand was efficiently generated from the reaction of a second-generation Grubbs ruthenium catalyst with vinyloxytrimethylsilane and unambiguously characterized. This ruthenium hydride complex showed high catalytic activity for the selective isomerization of terminal olefin and for the cycloisomerization of 1,6-dienes. These reactions of N-allyl-o-vinylaniline lead to novel synthetic methods for heterocycles such as indoles and 3-methylene-2,3-dihydroindoles, which are useful synthons for bioactive natural products. These procedures address an important issue in diversity-oriented synthesis.
- Arisawa, Mitsuhiro,Terada, Yukiyoshi,Takahashi, Kazuyuki,Nakagawa, Masako,Nishida, Atsushi
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p. 4255 - 4261
(2007/10/03)
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- New selectivities from old catalysts. Occlusion of Grubbs' catalysts in PDMS to change their reactions
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This article describes new selectivities for Grubbs' first and second generation catalysts when occluded in a hydrophobic matrix of polydimethylsiloxane (PDMS). Occlusion of catalysts in mm-sized slabs of PDMS is accomplished by swelling with methylene chloride then removing the solvent under vacuum. The catalysts are homogenously dissolved in PDMS yet remain catalytically active. Many substrates that react by olefin metathesis with Grubbs' catalysts freely dissolved in methylene chloride also react by olefin isomerization with occluded catalysts. Eleven examples of substrates that exhibit dual reactivity by undergoing olefin isomerization with occluded catalysts and olefin metathesis with catalysts dissolved in methylene chloride are reported. Most of these substrates have olefins with allylic phosphine oxides, carbonyls, or ethers. Control experiments demonstrate that isomerization is occurring in the solvent by decomposition of the catalyst from a ruthenium carbene to a proposed ruthenium hydride. This work was extended by heating occluded Grubbs' first generation catalyst to 100 °C in 90% MeOH in H2O in the presence of various alkenes to transform the Grubbs' catalyst into an isomerization catalyst for unfunctionalized olefins. This work demonstrates that occlusion of organometallic catalysts in PDMS has important implications for their reactions and can be used as a method to control which reactions they catalyze.
- Brett Runge,Mwangi, Martin T.,Bowden, Ned B.
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p. 5278 - 5288
(2007/10/03)
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- Electrocatalytic hydrogenation of organic compounds using current density gradient and sacrificial anode of nickel
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Preparative electrocatalytic hydrogenation (ECH) of some organic compounds were performed: cyclohexene, 2-cyclohexen-1-one, benzaldehyde, acetophenone, styrene, 1,3-cyclohexadiene, trans-trans-2,4-hexadien-1-ol, citral, linalool and geraniol. H2O/MeOH (1:1), NH4OAc or NH4Cl (0.2 M) were used as solvent and supporting electrolyte. A sacrificial anode of nickel allowed the use of an undivided cell, with a cell voltage varying between 2.3 and 1.3 V, depending on the supporting electrolyte. A current density gradient was applied to diminish the time of reaction and obtain a good electrochemical efficiency. An in situ prepared cathode of nickel deposited on iron provided a highly efficient ECH process, and the constant deposition of nickel on the electrode surface avoided catalyst poisoning. The ECH system was somewhat selective, hydrogenating conjugated olefins in good yield.
- Santana, Diogo S.,Lima, Márcio V. F.,Daniel, Jorge R. R.,Navarro, Marcelo
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p. 4725 - 4727
(2007/10/03)
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- Selective isomerization of a terminal olefin catalyzed by a ruthenium complex: The synthesis of indoles through ring-closing metathesis
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Aruthenium complex, generated from the Grubbs carbene catalyst with vinyloxytrimethylsilane, catalyzed the isomerization of terminal alkenes RCH2-CH=CH2 to internal alkenes RCH=CH-CH3. Application of this olefin isomerization to 2-(N-allylamino)styrene gave the corresponding enamines, which were converted into indoles by a standard ring-closing metathesis, see scheme (Ts = tosyl).
- Arisawa, Mitsuhiro,Terada, Yukiyoshi,Nakagawa, Masako,Nishida, Atsushi
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p. 4732 - 4734
(2007/10/03)
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- Palladium-Catalyzed Reductive Coupling of Acid Chlorides with β-Stannyl Enones: Synthesis of 1,4-Diketones and Mechanistic Aspects
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The palladium-catalyzed coupling of acid chlorides with (E)-1,2-bis(tri-n-butylstannyl)ethene or β-stannyl enones gives butane-1,4-diones directly by reduction of the intermediate enedicarbonyl intermediate.The double bond conjugated with a single carbonyl group was not significantly reduced.The generality of the method is illustrated by two syntheses of the 1,4-diketone ipomeanine.By performing the reaction at lower temperatures, α,β-unsaturated 1,4-diketones can also be prepared.The reduction of the intermediate α,β-unsaturated 1,4-diketones probably proceeds by insertion of a palladium hydride, formed in situ by reaction of a Pd(II) complex with Bu3SnCl, followed by hydrolysis of the intermediate palladium enolate.
- Echavarren, Antonio M.,Perez, Marta,Castano, Ana M.,Cuerva, Juan M.
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p. 4179 - 4185
(2007/10/02)
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- COMPOUNDS WITH HERBAL ODOR. V. UNBRANCHED PRIMARY (Z)-ALKENOLS
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The similarity between the odor of alkenols (Z)-CH3-(CH2)n(H=CH(CH2)mOH and the odor of leaf alcohol (m=2, n=1), taken as standard, gradually weakened with change in the m and/or n values and is determined by the number of carbon atoms in the molecules.
- Vasil'ev, A. A.,Cherkaev, G. V.,Nikitina, M. A.
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p. 735 - 739
(2007/10/02)
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- Regiochemistry and Stereochemistry of Intramolecular Photocycloaddition of Carbon-Carbon Double Bonds to Cyclohexenones
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The intramolecular photocycloaddition mechanism of alkenes tethered by a three-methylene chain to cyclohexenones has been studied.It was found that the reversion from a 1,4-diradical intermediate to starting material is slow relative to the rate of photoadduct formation.Only "straight" closure was observed in the systems studied.For compounds 1-3 and 5, the assumption that the first bond is formed between the β-carbon of the enone and C-4' leading to a 1,4-diradical is supported.For the formation of compounds 6-11, possible mechanisms are discussed.
- Becker, D.,Nagler, M.,Sahali, Y.,Haddad, N.
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p. 4537 - 4543
(2007/10/02)
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- Seven-Membered Ring Synthesis Based On Arene Olefin Cycloadditions: The Total Synthesis of (+/-)-Rudmollin
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The total synthesis of the antileukemic agent rudmollin (1) is described, based on a new approach to complex seven-membered ring synthesis involving the arene olefin meta photocycloaddition.
- Wender, Paul A.,Fisher, Karl
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p. 1857 - 1860
(2007/10/02)
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- EVOLUTION THERMIQUE DE N-OXYDES DE DIMETHYLAMINO-5 ALCANOLS-1 SUBSTITUES EN 5. COMPETITION ENTRE REARRANGEMENTS DE COPE ET DE MEISENHEIMER
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The effect of the substituent R in the 5 position was studied in the decomposition of 1,5-aminoalcohol N-oxides: Meisenheimer rearrangements takes place when R is the vinyl group but is not observed with the phenyl substituent; elimination to alkenol only
- Barbry, Didier,Hasiak, Bruno,Augait, Jean-Michel,Couturier, Daniel
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p. 956 - 961
(2007/10/02)
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- A New "One-Electron" Carbon-Carbon Bond Fprming Reaction: Separation of the Chain Propagation Steps in Free Radical Allylation
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Certain allylic phenyl sulfides react with alkyl halides or selenides upon irradiation in the presence of hexabutylditin to give formal SH2' substitution products.The process is successful for the introduction of groups such as phenyl, which cannot be accomplished by using an allylstannane.
- Keck, Gary E.,Byers, Jeffrey H.
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p. 5442 - 5444
(2007/10/02)
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- Reactions of 6,8-Dioxabicyclo(3.2.1)oct-3-ene and 6,8-Dioxabicyclo(3.2.1)oct-2-ene with Lithium Aluminium Hydride
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Reduction of 6,8-dioxabicyclo(3.2.1)oct-3-ene (6) with lithium aluminium hydride in refluxing 1,2-dimethoxyethane gives 2-hydroxymethyl-3,4-dihydro-2H-pyran (7) in an excellent yield.However, under identical conditions 6,8-dioxabicyclo(3.2.1)oct-2-ene (8) gives a mixture of 4-hexen-1-ol (9), 5-hexen-1-ol (10) and 2-hexene-1,6-diol (11).When 6 is refluxed with LAH in di-n-propyl ether, 7 is obtained in addition to 2-hydroxymethyl-2,3-dihydro-6H-pyran (33).However, compound 8 remains unaffected by LAH under similar conditions.
- Majumdar, K. C.,Ranganayakulu, K.,Brown, R. K.
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p. 303 - 306
(2007/10/02)
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- Transformation of Carbon-Oxygen into Carbon-Carbon Bonds Mediated by Low-Valent Nickel Species
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The substitution of alkoxy groups of enol ethers (1-methoxycyclohexenes, 1-methoxy-1-alkenes, and benzofuran) and aryl ethers (methoxynaphthalenes, cresyl methyl ethers, and dimethoxybenzenes) by hydrogen, alkyl groups, and aryl units, through Grignard reactions catalyzed by bis(triphenylphosphine)nickel dichloride or nickel dichloride, is described.The stereochemistry of the new reaction is portrayed, especially in connection with processes involving ring opening of dihydropyrans and dihydrofurans.The reaction has been applied to the synthesis of a termite trail pheromone and the acetate of the Douglas fir beetle aggregation pheromone.
- Wenkert, Ernest,Michelotti, Enrique L.,Swindell, Charles S.,Tingoli, Marco
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p. 4894 - 4899
(2007/10/02)
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- Novel Synthesis of (Z)-3-Hexen-1-ol and cis-Jasmone
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Both (Z)-3-hexen-1-ol and cis-jasmone were synthesised via 1,4-selective hydrogenation of conjugated dienes in the presence of arene Cr(CO)3 or Cr(CO)6 catalysts as the key step.
- Furuhata, Akimichi,Onishi, Ken,Fujita, Akira,Kogami, Kunio
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p. 1757 - 1760
(2007/10/02)
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- RHODIUM CATALYZED HYDROACYLATION OF ETHYLENE WITH 4-PENTENALS. REACTIONS OF 4-HEXENAL-1-d
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A catalyst derived from 2,4-pentanedionatobis(ethylene)rhodium(I), I, promoted the addition of 4-pentenal to ethylene.The reaction was accompanied by the formation of double bond migration products derived from the 4-pentenal reactant and from the 6-hepten-3-one primary product.Compound I accomplished the addition of 4-hexenal to ethylene to afford high yields of 6-octen-3-one.The fate of the aldehyde hydrogen in this transformation has been determined in experiments employing 4-hexenal-1-d as reactant.Treatment of 4-hexenal-1-d with I in CHCl3 and CDCl3 afforded 6-octen-3-one possesing > 50percent d0 molecules while the isotopic composition of recovered unexpended 4-hexenal remained > 96percent d1. 6-Octen-3-one products with isotopic compositions of > 66percent d0 were afforded when ethylene was introduced to reaction mixtures.The location of deuterium in 6-octen-3-one, derived from treatment of 4-hexenal-1-d with I in the absence of added C2H4, was determined to be distributed at C-1 and C-2 and at the C=C bond by analysis of the 1H and 2H NMR spectra.Unexpended ethylene was recovered and was found to contain a substantial amount of deuterium.Mechanistic implications of these results are discussed.
- Vora, Krishnakant P.,Lochow, Charles F.,Miller, Roy G.
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p. 257 - 264
(2007/10/02)
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