- Ring-closing olefin metathesis in the aqueous phase of amphiphilic conetworks consisting of fluorophilic and hydrophilic compartments
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A Grubbs-Hoveyda-Type metathesis catalyst bearing a tris(perfluoroalkyl)silyl tag was immobilized in the fluorophilic phase of amphiphilic conetworks (APCNs). This catalytic system was applied to ring-closing metathesis (RCM) reactions in aqueous media. Different substrates were evaluated and with 10 mol% of catalyst at 60 °C good conversions were observed. Reuse of the catalytic system was possible, but resulted generally in lower conversions.
- Hensle, Eva M.,Tobis, Jan,Tiller, J?rg C.,Bannwarth, Willi
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- Reactions of 2-(perfluoroalkyl)ethane thiols with 1,6-heptadiene and 4-substituted 1,6-heptadienes: The synthesis of RFethanethio- cyclopentanoic and -dioic acids; and, "geminal-twin-tail" bis-(perfluoroalkylethanethio)alkanoic acids
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Kinetic analysis of the free radical addition of n-C6F 13I to 1,6-heptadiene gives a rate ratio of cyclization to addition (kd1/kc) of 0.568 at 70°C; thus, the rate of cyclization (kc) is twice that of iodine transfer (kd1). By contrast, for n-C6F13CH2CH2SH (kd1/kc) = 14.4 at 70°C, and radical transfer of H from the thiol is 14.4 times the faster than cyclization. Substitution at the center of 1,6-heptadiene has a profound effect on the linear/cyclic adduct ratio. For the addition of n-C3F7I (RFI:diene= 2:0) the adduct ratios dramatically decrease in the order: 1,6-heptadiene (1.17) > 4-carboxy-1,6-heptadiene (0.0613) > 4,4-bis-ethoxycarbonyl-1,6- heptadiene (F(CH 2)3]2CHCO2R, or [R F(CH2)3]2C(CO2R) 2 must be synthesized by other means. For the reaction of R FCH2CH2SH with the dienes (1:1), the respective adduct ratios are 11.3 (n-C6F13), 0.370 (n-C 8F17), and 0.0716 (n-C6F13). However, adding the 4-carboxy-1,6-heptadiene slowly to four mols of n-C 8F17CH2CH2SH yields 98% of the geminal bis-adduct [RFCH2CH2S(CH 2)3]2CHCO2H, which is a new, fluorophilic, geminal-twin-tail acid.
- Brace, Neal O.
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- REACTIONS OF ORGANOCOBALT COMPLEXES WITH BROMOESTERS: REGIOSPECIFIC SYNTHESIS OF ALLYL- AND CYCLOPROPYLMETHYL-SUBSTITUTED MALONIC AND ACETOACETIC ESTERS
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Allyl(pyridine)cobaloximes RCo(dmgH)2Py (R = allyl) react readily with diethyldibromomalonate, diethylbromomethylmalonate and ethyl 2-bromoacetoacetate to give the corresponding allyl-substituted esters.Transfer of the allyl group occurs with complete rearrangement in all but one cases.Buten-3-yl(pyridine)cobaloximes react with diethylbromomalonate giving cyclopropylmethylmalonic esters.
- Veber, M.,Duong, K.N.-V.,Gaudemer, A.,Johnson, M. D.
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- Simple synthesis and anti-HIV activity of novel cyclopentene phosphonate nucleosides
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A very simple synthetic route for novel cyclopentene phosphonate nucleosides is described. The characteristic cyclopentene moiety 6 was constructed via a ring-closing metathesis of divinyl 5 , which could be readily prepared from diethylmalonate. The condensation of the mesylate 11 with nucleobases (A,C,T,U) under nucleophilic substitution conditions (K 2CO3, 18-Crown-6, DMF) afforded the target nucleosides 12 , 13 , 14 , and 15 . In addition, the antiviral evaluations against various viruses were performed. Copyright Taylor & Francis Group, LLC.
- Kim, Aihong,Hong, Joon
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- Ruthenium-catalyzed cross-metathesis between diallylsilanes and electron-deficient olefins
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Diallysilanes can be selectively coupled with electron-deficient olefins under cross-metathesis (CM) conditions using the Hoveyda-Grubbs catalyst to produce mono- and/or bis-CM compounds in good yield. The formation of the mono- and the bis-CM compounds depends on the nature of the electron-deficient olefin.
- Bouzbouz, Samir,Boulard, Lucie,Cossy, Janine
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- Generation of four five-membered rings in a one pot process. Studies directed toward the synthesis of dicyclopenta[a,d]pentalene via the tandem Pauson-Khand reaction
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The synthesis of the four five-membered rings of a suitably functionalized parent system 15 of dicyclopenta[a,d]pentalene 2 has been accomplished via a tandem Pauson-Khand reaction in a one pot process.
- Van Ornum, Scott G.,Cook, James M.
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- Synthesis and anti-HCMV activity of novel 5′-norcarboacyclic nucleosides
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A very simple route for synthesizing a novel carboacyclic version of 5¢-noraristeromycin is described. Condensation of the mesylates 9 and 23 with the natural nucleosidic bases (A, U, T, C) under standard nucleophilic substitution (K2CO3, 18-Crown-6, DMF) and deblocking conditions, afforded the target nucleosides 14, 15, 16, 17, 28, 29, 30, and 31. In addition, these compounds were evaluated for their antiviral properties against various viruses.
- Kim, Aihong,Hong, Joon Hee
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- Metal-free Photochemical Atom Transfer Radical Addition (ATRA) of BrCCl3 to Alkenes
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A simple, photochemical, and metal-free protocol for the atom transfer radical addition (ATRA) of bromotrichloromethane onto various alkenes is described. Among a range of organic molecules, phenylglyoxylic acid proved to be the most suitable photoinitiator to promote a sustainable process for the addition of bromotrichloromethane to olefins. This photochemical atom transfer radical protocol can be expanded into a wide substrate scope of aliphatic olefins bearing various functional groups, leading to the corresponding products in good to excellent yields.
- Nikitas, Nikolaos F.,Voutyritsa, Errika,Gkizis, Petros L.,Kokotos, Christoforos G.
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supporting information
p. 96 - 101
(2021/01/04)
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- Catalytic C?C Bond Formation Using a Simple Nickel Precatalyst System: Base- and Activator-Free Direct C-Allylation by Alcohols and Amines
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A “totally catalytic” nickel(0)-mediated method for base-free direct alkylation of allyl alcohols and allyl amines is reported. The reaction is selective for monoallylation, uses an inexpensive NiII precatalyst system, and requires no activating reagents to be present.
- Sweeney, Joseph B.,Ball, Anthony K.,Smith, Luke J.
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supporting information
p. 7354 - 7357
(2018/05/03)
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- Correction: Exploiting and understanding the selectivity of Ru-N-heterocyclic carbene metathesis catalysts for the ethenolysis of cyclic olefins to α,ω-Dienes (Journal of the American Chemical Society (2017) 139:37 (13117-13125) DOI: 10.1021/jacs.7b06947)
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The isotropic chemical shielding (iso) was mislabeled as the isotropic chemical shift (iso) in Table S40, Figures 2, 4, S153 and in the respective discussion of these figures in the text. The corrected figures are shown below; the SI graphics are provided in the corrected SI file. In the conclusion section, "cyclic olefins" was incorrectly written as "cyclic dienes" to be the essential structural feature for the selective ethenolysis toward w-dienes. The ROMP activity of Ru-20 is not detectable in the "presence of ethylene"; this was incorrectly written as the "absence of ethylene". Equations 5 and 7, pages S47 and S135 respectively, had errors that have been fixed in the corrected SI file. None of the above affects any conclusions of the article. (Figure Presented).
- Engl, Pascal S.,Santiago, Celine B.,Gordon, Christopher P.,Liao, Wei-Chih,Fedorov, Alexey,Copéret, Christophe,Sigman, Matthew S.,Togni, Antonio
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supporting information
p. 18227 - 18228
(2019/01/09)
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- Rhodium-Catalyzed Cyclization of O,ω-Unsaturated Alkoxyamines: Formation of Oxygen-Containing Heterocycles
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O,ω-Unsaturated N-tosyl alkoxyamines undergo unexpected RhIII-catalyzed intramolecular cyclization by oxyamination to produce oxygen-containing heterocycles. Mechanistic studies show that an aziridine intermediate seems to be responsible for the formation of the heterocycles, possibly via a RhV species.
- Escudero, Julien,Bellosta, Véronique,Cossy, Janine
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supporting information
p. 574 - 578
(2018/02/21)
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- Phase-transfer Tsuji—Trost allylation of CH-acids with the assistance of palladium complexes with bidentate PIII—N—PIII ligands
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The Tsuji—Trost allylation of CH acids, in particular, those of the YCH2CO2Et type (Y = CO2Et, C(O)Me, CN), with allylic acetates in the K2CO3—DMF system in the presence of palladium catalysts with ligands RN(PPh2)2 (R = Ph, Pri, c-C6H11) is accomplished.
- Vasil′ev,Aladzheva,Bykhovskaya
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p. 661 - 665
(2017/09/11)
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- Exploiting and understanding the selectivity of Ru-N-Heterocyclic carbene metathesis catalysts for the ethenolysis of cyclic olefins to α,ω-Dienes
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A library of 29 homologous Ru-based olefin metathesis catalysts has been tested for ethenolysis of cyclic olefins toward the goal of selectively forming α,ω-diene using cis-cyclooctene as a prototypical substrate. Dissymmetry at the N-heterocyclic carbene (NHC) ligand was identified as a key parameter for controlling the selectivity. The best-performing catalyst bearing an N-CF3 group significantly outperformed the benchmark second-generation Grubbs catalyst in the ethenolysis of cis-cyclooctene. Application of this optimal catalyst to the ethenolysis of various norbornenes allows the efficient synthesis of valuable diene intermediates in good yields. The observed ligand effect trends could be rationalized through univariate and multivariate parameter analysis involving steric and electronic descriptors of the NHC ligand in the form of the buried volume and the 77Se NMR chemical shift, in particular the σyy component of the shielding tensor of [Se(NHC)] model compounds, respectively. Natural chemical shift analysis of this chemical shielding tensor shows that σyy probes the I-Acceptor property of the NHC ligand, the essential electronic parameter that drives the relative rate of degenerate metathesis and selectivity in ethenolysis with catalysts bearing dissymmetric NHC ligands.
- Engl, Pascal S.,Santiago, Celine B.,Gordon, Christopher P.,Liao, Wei-Chih,Fedorov, Alexey,Copéret, Christophe,Sigman, Matthew S.,Togni, Antonio
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supporting information
p. 13117 - 13125
(2017/09/26)
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- Nickel-Catalysed Bis-Allylation of Activated Nucleophiles with Allyl Alcohol
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Nickel-based catalysis allows the efficient bis-allylation of soft nucleophiles with allylic alcohols. The reaction is best promoted by a combination of Ni(cod)2 (cod = cyclooctadienyl) and diphenylphosphinobutane under additive-free conditions. Alternatively, nickel(II) precursors can be used provided that a reductant is used to generate the nickel(0) species. The NiCl2/Zn combination is particularly simple, and can advantageously replace the use of the more air-sensitive Ni(cod)2 precursor. The scope of the reaction was studied with nucleophiles and allylic derivatives suitable for bis-allylation reactions.
- Blieck, Rémi,Azizi, Mohamed Salah,Mifleur, Alexis,Roger, Maxime,Persyn, Clément,Sauthier, Mathieu,Bonin, Hélène
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p. 1194 - 1198
(2016/03/05)
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- Iron(II) catalyzed reductive radical cyclization reactions of bromoacetals in the presence of NaBH4: optimization studies and mechanistic insights
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5-Exo-trig radical reductive cyclization reactions of bromoacetals are catalyzed by iron in the presence of the reducing agent NaBH4. Both iron(II) and iron(III) were found to effectively mediate these reactions. As shown by cyclic voltammetry, iron(III) can be reduced to an iron(II) precatalyst before passing through an identical reaction mechanism in which monoelectronic activation of the substrate would occur by an anionic hydridoiron(I) complex. Further studies have established that both the substrate (iodo- vs bromo-derivative) and the precatalytic mixture are decisive in determining the reaction outcome.
- Kyne, Sara H.,Lévêque, Christophe,Zheng, Shiwen,Fensterbank, Louis,Jutand, Anny,Ollivier, Cyril
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p. 7727 - 7737
(2016/11/18)
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- A radical cascade reaction triggered by thiyl radical; An approach toward synthesis of tricyclic structure of platensimycin
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The formation of oxa-tricyclic core of platensimycin was attempted. A key precursor of radical cyclization, cyclic anhydride, was readily prepared from diethylmalonate in 6 steps in good yields. Obtained precursor, diallylmethylene-δ-lactone, underwent radical cascade reaction triggered by thiyl radical, giving bicyclic ether in a stereoselective manner.
- Kamimura, Akio,Kawakami, Yusuke
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p. 259 - 262
(2016/02/18)
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- Highly selective palladium-benzothiazole carbene-catalyzed allylation of active methylene compounds under neutral conditions
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The Pd-benzothiazol-2-ylidene complex I was found to be a chemoselective catalyst for the Tsuji-Trost allylation of active methylene compounds carried out under neutral conditions and using carbonates as allylating agents. The proposed protocol consists in a simplified procedure adopting an in situ prepared catalyst from Pd2dba3 and 3-methylbenzothiazolium salt V as precursors. A comparison of the performance of benzothiazole carbene with phosphanes and an analogous imidazolium carbene ligand is also proposed.
- Monopoli, Antonio,Cotugno, Pietro,Zambonin, Carlo G.,Ciminale, Francesco,Nacci, Angelo
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supporting information
p. 994 - 999
(2015/08/19)
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- A medium fluorous Grubbs-Hoveyda 2nd generation catalyst for phase transfer catalysis of ring closing metathesis reactions
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A fluorous Grubbs-Hoveyda metathesis catalyst supported on Teflon powder, that readily moves between the solid phase (Teflon) and the liquid phase (DMF) was prepared. By modulating the hydrophobicity of the reaction medium at the end of the reaction, the supported catalyst could be recovered by simple filtration even though the catalyst existed in a homogeneous state during the reaction. In RCM reactions, the catalyst could be reused up to three times with only a slight loss in reactivity with each subsequent cycle.
- Kobayashi, Yuki,Inukai, Sae,Kondo, Natsuki,Watanabe, Tomoko,Sugiyama, Yuya,Hamamoto, Hiromi,Shioiri, Takayuki,Matsugi, Masato
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supporting information
p. 1363 - 1366
(2015/03/04)
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- Allyl sulphides in olefin metathesis: Catalyst considerations and traceless promotion of ring-closing metathesis
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Allyl sulphides are reactive substrates in ruthenium-catalysed olefin metathesis reactions, provided each substrate is matched with a suitable catalyst. A profile of catalyst activity is described, along with the first demonstration of allyl sulphides as traceless promoters in relayed ring-closing metathesis reactions. This journal is
- Edwards, Grant A.,Culp, Phillip A.,Chalker, Justin M.
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supporting information
p. 515 - 518
(2015/02/19)
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- Trifluoromethylchlorosulfonylation of alkenes: Evidence for an inner-sphere mechanism by a copper phenanthroline photoredox catalyst
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Abstract A visible-light-mediated procedure for the unprecedented trifluoromethylchlorosulfonylation of unactivated alkenes is presented. It uses [Cu(dap)2]Cl as catalyst, and contrasts with [Ru(bpy)3]Cl2, [Ir(ppy)2(dtbbpy)]PF6, or eosin Y that exclusively give rise to trifluoromethylchlorination of the same alkenes. It is assumed that [Cu(dap)2]Cl plays a dual role, that is, acting both as an electron transfer reagent as well as coordinating the reactants in the bond forming processes. Double role: The trifluoromethylchlorosulfonylation of unactivated alkenes was developed using [Cu(dap)2]Cl as catalyst (dap=2,9-bis(para-anisyl)-1,10-phenanthroline). [Cu(dap)2]Cl plays a dual role; acting as an electron transfer reagent as well as coordinating the reactants in the bond forming processes.
- Bagal, Dattatraya B.,Kachkovskyi, Georgiy,Knorn, Matthias,Rawner, Thomas,Bhanage, Bhalchandra M.,Reiser, Oliver
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supporting information
p. 6999 - 7002
(2015/06/08)
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- A general synthetic approach to para-cyclophanes via ring-closing metathesis
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A new methodology for the synthesis para-cyclophanes and longithorone C frameworks has been demonstrated via alkylation, ceric ammonium nitrate (CAN) oxidation and ring-closing metathesis as key steps.
- Kotha, Sambasivarao,Shirbhate, Mukesh E.
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p. 1483 - 1494
(2016/02/26)
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- A general synthetic approach to para-cyclophanes via ring-closing metathesis
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A new methodology for the synthesis para-cyclophanes, and longithorone C frameworks has been demonstrated via alkylation, eerie ammonium nitrate (CAN) oxidation and ring-closing metathesis as key steps.
- Kotha, Sambasivarao,Shirbhate, Mukesh E.
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p. 1483 - 1494
(2016/09/09)
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- Palladium nanoparticles bonded to two-dimensional iron oxide graphene nanosheets: A synergistic and highly reusable catalyst for the Tsuji-Trost reaction in water and air
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Low cost, high activity and selectivity, convenient separation, and increased reusability are the main requirements for noble-metal-nanocatalyst- catalyzed reactions. Despite tremendous efforts, developing noble-metal nanocatalysts to meet the above requirements remains a significant challenge. Here we present a general strategy for the preparation of strongly coupled Fe3O4 and palladium nanoparticles (PdNPs) to graphene sheets by employing polyethyleneimine as the coupling linker. Transmission electron microscopic images show that Pd and Fe3O4 nanoparticles are highly dispersed on the graphene surface, and the mean particle size of Pd is around 3 nm. This nanocatalyst exhibits synergistic catalysis by Pd nanoparticles supported on reduced graphene oxide (rGO) and a tertiary amine of polyethyleneimine (Pd/Fe3O4/PEI/rGO) for the Tsuji-Trost reaction in water and air. For example, the reaction of ethyl acetoacetate with allyl ethyl carbonate afforded the allylated product in more than 99% isolated yield, and the turnover frequency reached 2200 h-1. The yield of allylated products was 66% for Pd/rGO without polyethyleneimine. The catalyst could be readily recycled by a magnet and reused more than 30 times without appreciable loss of activity. In addition, only about 7.5% of Pd species leached off after 20 cycles, thus rendering this catalyst safer for the environment. Picking up speed: A multifunctional Pd nanocatalyst was synthesized by in situ growth of palladium nanoparticles (PdNPs) and the assembly of Fe3O4 NPs on reduced graphene oxide (rGO) by employing polyethyleneimine as the coupling linker. This nanocatalyst exhibits synergistic catalysis by the amine on the same rGO surface as the PdNPs for acceleration of the Tsuji-Trost reaction in water and air (see figure).
- Liu, Jian,Huo, Xing,Li, Tianrong,Yang, Zhengyin,Xi, Pinxian,Wang, Zhiyi,Wang, Baodui
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p. 11549 - 11555
(2014/11/07)
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- Palladium(II) aminoiminophosphoranate complexes as cross-coupling catalysts
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The Tsuji-Trost reaction between diethyl malonate and allyl acetate catalyzed by palladium(II) NPN-aminoiminophosphoranate complexes yields mono- and diallylation products in the ratios depending on the complex used. The Suzuki-Miyaura cross-coupling of 4-bromoacetophenone with phenylboronic acid catalyzed by these palladium complexes proceeds with 66-99.5% conversions.
- Peganova,Kalsin,Ustynyuk,Vasil'Ev
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p. 2305 - 2308
(2015/06/22)
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- Palladium-catalyzed allylation of malonic acid derivatives in heterogeneous systems containing ionic liquids
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Palladium-catalyzed potassium carbonate-assisted reaction between diethyl malonate and allyl acetate in the presence of 1,3-dialkyl-imidazolium ionic liquids (ILs) as solvents or phase transfer catalysts affords major monoallylation product, whereas in the presence of 1,2,3-trialkylimidazolium or quaternary ammonium/phosphonium ILs diallylation product is preferably formed. These procedures are extended to some other CH-acids and allylic acetates.
- Vasil'ev, Andrei A.,Zlotin, Sergei G.
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- Design and synthesis of angularly annulated spirocyclics via enyne metathesis and the Diels-Alder reaction as key steps
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We have developed a simple and an efficient route to a range of angularly fused spirocycles by the application of enyne metathesis and the Diels-Alder reaction as key steps. The enyne metathesis protocol has been further extended to the dibenzylation of indane-1,3-dione by using cross-enyne metathesis in the presence of hexa-1,5-diene with the aid of Grubbs' 1st generation catalyst followed by an aromatization sequence with DDQ. Georg Thieme Verlag Stuttgart New York.
- Kotha, Sambasivarao,Ali, Rashid,Tiwari, Arti
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supporting information
p. 2471 - 2480
(2014/11/08)
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- Design and Synthesis of Angularly Annulated Spirocyclics via Enyne Metathesis and the Diels-Alder Reaction as Key Steps
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We have developed a simple and an efficient route to a range of angularly fused spirocycles by the application of enyne metathesis and the Diels-Alder reaction as key steps. The enyne metathesis protocol has been further extended to the dibenzylation of indane-1,3-dione by using cross-enyne metathesis in the presence of hexa-1,5-diene with the aid of Grubbs' 1st generation catalyst followed by an aromatization sequence with DDQ.
- Kotha, Sambasivarao,Ali, Rashid,Tiwari, Arti
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supporting information
p. 2471 - 2480
(2015/12/26)
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- Low catalyst loading in ring-closing metathesis reactions
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An efficient procedure is described for ring-closing metathesis reactions. A conversion of 95 % for diethyl diallylmalonate in dilute solution could be achieved within a few minutes, reaching TOF=4173min-1, with very low loading of commercially available Ru catalysts that contained unsaturated NHC ligands. In general, only 50 to 250ppm of the catalyst is required to achieve near-quantitative conversion into a broad variety of 5-16-membered heterocyclic compounds. The practicality of this procedure was illustrated in the synthesis of 5-8-membered N-tert-butoxycarbonyl (N-Boc)- and N-para-toluenesulfonyl (N-Ts)-protected cyclic amines and 9-16-membered lactones. The synthesis of macrocyclic proline-based lactams required slightly higher catalyst loadings. Along with monocyclic products, oligomeric byproducts, mostly cyclodimers, were isolated and characterized. Getting some closure: An efficient procedure is described for ring-closing metathesis reactions in which only 50 to 250ppm of catalyst is required to effect almost-quantitative conversion into a broad range of 5-16-membered heterocyclic compounds. The practicality of this procedure was illustrated in the synthesis of 5-8-membered N-protected cyclic amines, 9-16-membered lactones, and 11-16-membered proline-based lactams. Copyright
- Kadyrov, Renat
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supporting information
p. 1002 - 1012
(2013/02/23)
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- Study on the total synthesis of velbanamine: Chemoselective dioxygenation of alkenes with PIFA via a stop-and-flow strategy
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A "stop-and-flow" strategy was developed for the chemoselective dioxygenation of alkenes with a PIFA-initiated cyclization. This method is conceived for the desymmetrization of seco-diene, and a series of substituted 5-hydroxymethyl-γ-lactones were constructed after hydrolysis. This strategy also differentiates terminally substituted alkenes and constitutes a potentially novel synthetic approach for the efficient synthesis toward velbanamine.
- Liu, Huili,Zheng, Kuan,Lu, Xiang,Wang, Xiaoxia,Hong, Ran
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supporting information
p. 983 - 990
(2013/07/19)
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- Photoredox transformations with dimeric gold complexes
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Let the sunshine in! Unactivated alkyl and aryl bromides underwent a light-enabled reductive radical cyclization in the presence of a dimeric phosphine-gold complex as a photocatalyst (see scheme; X=C(CO 2Et)2, NR, O). Sunlight can be used as the energy source for this simple and efficient radical reaction, which does not require potentially hazardous and toxic chemical reagents, such as organostannanes and chemical initiators.
- Revol, Guillaume,McCallum, Terry,Morin, Mathieu,Gagosz, Fabien,Barriault, Louis
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supporting information
p. 13342 - 13345
(2014/01/06)
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- Diversity-oriented approach to macrocyclic cyclophane derivatives via ring-closing metathesis
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A short synthetic approach to the macrocyclic framework of longithorone C is described via ring-closing metathesis using the Grubbs 2nd generation catalyst. Georg Thieme Verlag Stuttgart ? New York.
- Kotha, Sambasivarao,Shirbhate, Mukesh E.
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p. 2183 - 2188
(2012/11/07)
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- Efficient chemoselective alkylation of quinoline 2,4-diol derivatives in water
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Synthesis of various C-3-dialkyl derivatives of quinoline 2,4-diol was achieved by condensation of aniline or substituted anilines with diethyl malonate, followed by chemoselective alkylation at C-3 in water. The higher yields, easy work up and environmental compatible conditions are the main aspects of our method.
- Ahmed, Nafees,Brahmbhatt, Keyur G.,Singh, Inder P.,Bhutani, Kamlesh K.
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p. 237 - 240
(2011/03/21)
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- Serendipitous and acid catalyzed synthesis of spirolactones
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Formation of three diasteroisomeric spirodilactones 14a-c and 11 has been reported from diester 13 and 9, respectively, under the influence of mineral acid.
- Kotha, Sambasivarao,Dipak, Mirtunjay Kumar,Mobin, Shaikh M.
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scheme or table
p. 4616 - 4619
(2011/06/27)
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- Metal-free oxyaminations of alkenes using hydroxamic acids
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A radical-mediated approach to metal-free alkene oxyamination is described. This method capitalizes on the unique reactivity of the amidoxyl radical in alkene additions to furnish a general difunctionalization using simple diisopropyl azodicarboxylate (DIAD) as a radical trap. This protocol capitalizes on the intramolecular nature of the process, providing single regioisomers in all cases. Difunctionalizations of cyclic alkenes provide trans oxyamination products inaccessible using current methods with high levels of stereoselectivity, complementing cis-selective oxyamination processes.
- Schmidt, Valerie A.,Alexanian, Erik J.
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supporting information; experimental part
p. 11402 - 11405
(2011/09/16)
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- Environmentally-benign palladium(II)-exchanged hydroxyapatite-catalyzed allylic alkylation of allyl methyl carbonate in water
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Palladium(II)-exchanged hydroxyapatite (PdHAP; for example, PdHAP-B has a Pd/Ca ratio = ca 1/200) was prepared by ion-exchanging with Ca2+ from calcined hydroxyapatite and Pd(NO3)2 in water at 70 °C for 24 h. The ion-exchange was revealed by inductively coupled plasma analysis; Pd2+ was almost absent in any filtrate that included over 1.6 equimolar amounts of Ca2+ relative to the amount of Pd 2+ consumed. The PdHAP (1 mol% Pd) functioned as a catalyst for the allylic alkylation of allyl methyl carbonate with active methylene compounds such as diethyl malonate, 2-ethoxycarbonylcyclopentanone, 2- ethoxycarbonylcyclohexanone, and 2,2-dimethyl-1,3-dioxane-4,6-dione at 50 °C in water under air. Over 97% of the PdHAP was recovered by centrifugation followed by decantation, and the material could be reused. The catalytic activity of PdHAP accompanied by satisfactory yields of monoallylated products was maintained in ten repetitive uses for the allylic alkylation of allyl methyl carbonate with diethyl malonate at 50 °C for 24 h in water under air. From the standpoints of yield and handling, using water as a solvent was superior to using an organic medium such as ethanol, THF or DMF. Thus, this heterogeneous PdHAP-catalyzed allylic alkylation will be one of the environmentally-benign organic syntheses.
- Masuyama, Yoshiro,Nakajima, Yukiko,Okabe, Jun
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experimental part
p. 107 - 112
(2011/06/21)
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- Nonproductive events in ring-closing metathesis using ruthenium catalysts
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The relative TONs of productive and nonproductive metathesis reactions of diethyl diallylmalonate are compared for eight different ruthenium-based catalysts. Nonproductive cross metathesis is proposed to involve a chain-carrying ruthenium methylidene. A second more-challenging substrate (dimethyl allylmethylallylmalonate) that forms a trisubstituted olefin product is used to further delineate the effect of catalyst structure on the relative efficiencies of these processes. A steric model is proposed to explain the observed trends.
- Stewart, Ian C.,Keitz, Benjamin K.,Kuhn, Kevin M.,Thomas, Renee M.,Grubbs, Robert H.
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supporting information; experimental part
p. 8534 - 8535
(2010/08/06)
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- Metal-free, aerobic dioxygenation of alkenes using hydroxamic acids
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(Chemical equation presented) One dioxygenation please, hold the metal: In the presence of either oxygen or air as the sole oxidant and external oxygen atom source, a variety of unsaturated hydroxamic acids afford cyclic hydroxamates that are readily converted into 1,2-diols, with the potential for high levels of reaction stereocontrol.
- Schmidt, Valerie A.,Alexanian, Erik J.
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supporting information; experimental part
p. 4491 - 4494
(2010/08/21)
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- Lewis acid-promoted electron transfer deoxygenation of epoxides, sulfoxides, and amine N-oxides: the role of low-valent niobium complexes from NbCl5 and Zn
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A mild and operationally simple deoxygenation of epoxides, sulfoxides, and amine N-oxides is described using a sub-stoichiometric amount of low-valent niobium complexes generated in situ from commercially available NbCl5 and zinc dust. The deoxygenation proceeds by a reductive cleavage of polarized O-C/O-N/O-S bonds through a single electron transfer from zinc metal to the niobium-substrate complex due to the high oxophilic nature of the niobium species. The presence of adjacent radical-stabilizing groups is beneficial to epoxide substrates; however the similar prerequisite does not apply to sulfoxides and amine N-oxides, where a broad range of substrates are efficiently deoxygenated in excellent yields.
- Oh, Kyungsoo,Knabe, William Eric
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supporting information; body text
p. 2966 - 2974
(2009/05/30)
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- Chiral and achiral phosphine derivatives of alkylidyne tricobalt carbonyl clusters as catalyst precursors for (asymmetric) inter- and intramolecular Pauson-Khand reactions
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Phosphine derivatives of alkylidyne tricobalt carbonyl clusters have been tested as catalysts/catalyst precursors in intermolecular and (asymmetric) intramolecular Pauson-Khand reactions. A number of new phosphine derivatives of the tricobalt alkylidyne clusters [Co3(μ3-CR)(CO) 9] (R = H, CO2Et) were prepared and characterised. The clusters [Co3(μ3-CR)(CO) 9-x(PR′3)x] (PR′3 = achiral or chiral monodentate phosphine, x = 1-3) and [Co3(μ 3-CR)(CO)7(P-P)] (P-P = chiral diphosphine; 1,1′- and 1,2-structural isomers) were assayed as catalysts for intermolecular and (asymmetric) intramolecular Pauson-Khand reactions. The phosphine-substituted tricobalt clusters proved to be viable catalysts/catalyst precursors that gave moderate to very good product yields (up to ~90%), but the enantiomeric excesses were too low for the clusters to be of practical use in the asymmetric reactions. The Royal Society of Chemistry.
- Moberg, Viktor,Mottalib, M. Abdul,Sauer, Desiree,Poplavskaya, Yulia,Craig, Donald C.,Colbran, Stephen B.,Deeming, Antony J.,Nordlander, Ebbe
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p. 2442 - 2453
(2008/09/20)
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- Ring opening of methylenecycloalkenes via the C-C bond cleavage
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(Chemical Equation Presented) 3-Methylenecycloalkene-1,1-dicarboxylates underwent facile ring opening via the cleavage of the unactivated C-C bond to yield aliphatic alkenes. The reaction (intramolecular deallylation) was catalyzed by "Ni-H" species generated in situ from a NiX 2(phosphine)n/R3AI mixture and proceeded under ambient conditions. In addition, the skeletal rearrangement of a diene could be carried out by a one-pot cycloisomerization/ deallylation sequence.
- Necas, David,Kotora, Martin
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supporting information; experimental part
p. 5261 - 5263
(2009/06/18)
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- Design and synthesis of spiro-heterocycles by ring-closing metathesis
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Synthesis of diverse spiro-heterocyclic compounds via the ring-closing (RCM) metathesis approach is described. Specifically, synthesis of various derivatives of barbituric acid, Meldrum's acid, tetronic acid and thiotetronic acid are described by RCM approach.
- Kotha, Sambasivarao,Deb, Ashoke Chandra
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p. 1120 - 1134
(2008/12/23)
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- Solvent-controlled highly selective bis-and monoallylation of active methylene compounds by allyl acetate with palladium(0) nanoparticle
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(Chemical Equation Presented) Palladium(0) nanoparticle has been used as an efficient catalyst for the allylation of active methylene compounds. Very efficient bisallylation is achieved for a variety of active methylene compounds by allyl acetate and its derivatives in one stroke in THF solvent. The reaction in water provides monoallylated product selectively by allyl acetate only. The recovered Pd(0) nanoparticle is recycled. A probable mechanism is suggested.
- Ranu, Brindaban C.,Chattopadhyay, Kalicharan,Adak, Laksmikanta
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p. 4595 - 4598
(2008/03/12)
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- Nickel-catalyzed cyclization of α,ω-dienes: Formation vs. cleavage of C-C bonds
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A combination of a catalytic amount of a Ni-phosphine complex and triethylaluminium or chlorodiethylaluminium is able to selectively cyclize a number of 1,7-heptadienes to methylidene(methyl)cyclopentanes and cyclopentenes even in cases where the dienes are prone to deallylation. the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.
- Necas, David,Tursky, Matyas,Tislerova, Iva,Kotora, Martin
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p. 671 - 674
(2007/10/03)
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- NOVEL 3, 4-PROPYLENEDIOXYTHIOPHENE DERIVATIVES WITH PENDANT FUNCTIONAL GROUPS
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The present invention relates to the syntheses of 3,4-propylenedioxythiophenes of the formula (I) wherein R represents a n-valent linear or branched, optionally substituted, aliphatic C1-Cn radical and Y represents a pendant functional group. Further, methods for the preparation of the said compounds are disclosed.
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Page/Page column 13-14
(2010/11/24)
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- Syntheses of 4-[(1H,3H)-pyrimidine-2,4-dion-1-yl]- and 4-[(1H,3H)-5- methylpyrimidine-2,4-dion-1-yl]-1,6-heptadienes
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Heptadienes containing nucleic bases are attractive building blocks for the synthesis of carbocyclic oligonucleotide analogs. Herein, we report an alternative synthetic route to 4-[(1H,3H)-pyrimidine-2,4-dion-1-yl]-1,6- heptadiene and 4-[(1H,3H)-5-methylpyrimidine-2,4-dion-1-yl]-1,6-heptadiene via building the pyrimidine ring utilizing 4-isocyanato-1,6-heptadiene intermediate.
- Bouhadir, Kamal H.,Zhou, Jing-Lan,Shevlin, Philip B.
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p. 1003 - 1010
(2007/10/03)
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- Spiro-annulation of barbituric acid derivatives and its analogs by ring-closing metathesis reaction
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Barbituric acid 1 and related β-dicarbonyl compounds were dialkenylated under the phase-transfer catalyst [e.g., benzyltriethylammonium chloride (BTEAC)] conditions to generate the diallylated products. These diallylated products were subjected to the ring-closing metathesis (RCM) reaction to deliver the corresponding spiro-annulated derivatives.
- Kotha, Sambasivarao,Deb, Ashoke Chandra,Kumar, Ramanatham Vinod
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p. 1039 - 1043
(2007/10/03)
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- Catalytic deallylation of allyl- and diallylmalonates
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Substituted allylmalonates undergo the selective C-C bond cleavage in the presence of triethylaluminum and a catalytic amount of nickel and ruthenium phosphine complexes, resulting in the loss of the allyl moiety and formation of monosubstituted malonates. Comparison of reactivity of the nickel and ruthenium complexes showed that the use of the former is general with respect to the structure of the substituted allylmalonates, and the activity of the latter depended on the substitution pattern of the double bond of the allylic moiety. The smooth deallylation may encourage the use of the allyl group as a protective group for the acidic hydrogen in malonates. Copyright
- Necas, David,Tursky, Matyas,Kotora, Martin
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p. 10222 - 10223
(2007/10/03)
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- Triethylsilane-indium(III) chloride system as a radical reagent
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(Chemical Equation Presented) A novel generation method of indium hydride (Cl2InH) was found by the transmetalation of InCl3 with Et3SiH. In the intramolecular cyclization of enynes, the previously reported system (NaBH4-InCl3) has a problem of side reactions with the coexistent borane. In contrast, the problem was solved by the presented system, which affords effective hydroindation of alkynes.
- Hayashi, Naoki,Shibata, Ikuya,Baba, Akio
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p. 4981 - 4983
(2007/10/03)
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- Direct allylic substitution of allyl alcohols by carbon pronucleophiles in the presence of a palladium/carboxylic acid catalyst under neat conditions
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The reaction of allylic alcohols with carbon pronucleophiles in the presence of the Pd(PPh3)4/carboxylic acid combined catalytic system, under neat conditions (without an organic solvent or without water as the solvent) enabled the direct allylation of the pronucleophiles, giving the corresponding allylated products in high yields.
- Patil, Nitin T.,Yamamoto, Yoshinori
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p. 3101 - 3103
(2007/10/03)
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- Triethylborane as an efficient promoter for palladium-catalyzed allylation of active methylene compounds with allyl alcohols
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Without prior activation of allyl alcohols, allylation of a variety of active methylene compounds with allyl alcohols proceeds smoothly at rt-50°C in the presence of catalytic amounts of Pd(OAc)2 (1-10mol%), Et 3B (30-240mol%), a phosphine ligand (1-20mol%), and a base (0 to 50-60mol%).
- Kimura, Masanari,Mukai, Ryutaro,Tanigawa, Naoko,Tanaka, Shuji,Tamaru, Yoshinao
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p. 7767 - 7777
(2007/10/03)
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- Microwave-Assisted Ring-Closing Metathesis Revisited. On the Question of the Nonthermal Microwave Effect
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The ring-closing metathesis reactions (RCM) of six standard diene substrates leading to five-, six-, or seven-membered carbo- or heterocycles were investigated under controlled microwave irradiation. RCM protocols were performed with standard Grubbs type II and a cationic ruthenium allenylidene catalyst in neat and ionic liquid-doped methylene chloride under sealed vessel conditions. Very rapid conversions (15 s) were achieved utilizing 0.5 mol % Grubbs II catalyst under microwave conditions. Careful comparison studies indicate that the observed rate enhancements are not the result of a nonthermal microwave effect.
- Garbacia, Stefania,Desai, Bimbisar,Lavastre, Olivier,Kappe, C. Oliver
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p. 9136 - 9139
(2007/10/03)
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- Cobalt carbonyl-mediated carbocyclizations of enynes: Generation of bicyclooctanones or monocyclic alkenes
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Depending on the thermolytic conditions, dicobalthexacarbonyl-complexed enynes underwent cyclizations to provide different carbocyclic frameworks. Bicyclopentanones were formed from enyne-Co2(CO)6 complexes, or from enynes that were treated with Co2(CO)8, or more effectively, with Co4(CO)12 in an alcoholic solvent under a H2 or N2 atmosphere. This transformation proceeded via a sequential cyclocarbonylation and 1,4-reduction and is the first account using the cobalt carbonyl cluster. Under these conditions a cobalt hydride was presumably generated, which mediated reduction of the enone to the saturated ketone. In contrast, thermolysis of dicobalthexacarbonyl-complexed enynes under a hydrogen atmosphere in toluene resulted in their reductive cyclization to form monocyclic alkenes in moderate yields, in addition to the bicyclopentenone product. In some cases, addition of a hydrosilane to the reaction induced a complete suppression of the bicyclopentenone formation. While the former results demonstrate a reaction that occurs after the cycloaddition, the latter depicts another example of an interruption of the normal route in the Pauson-Khand reaction pathway.
- Krafft, Marie E.,Bonaga, Llorente Vicente R.,Wright, James A.,Hirosawa, Chitaru
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p. 1233 - 1246
(2007/10/03)
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