- Rate enhancement by ethylene in the ru-catalyzed ring-closing metathesis of enynes: Evidence for an "ene-then-yne" pathway that diverts through a second catalytic cycle
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(Chemical Equation Presented) Mixing it: A dual-substrate/dual isotopic labeling strategy has shown that the accelerating effect of ethylene in intermolecular ring-closing metathesis of enynes is best explained by an ene-then-yne mechanism rather than the
- Lloyd-Jones, Guy C.,Margue, Robert G.,De Vries, Johannes G.
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- Alkene-chelated ruthenium alkylidenes: A missing link to new catalysts
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A variety of heteroatom-chelated ruthenium alkylidenes have been developed as metathesis-active catalysts. Alkenechelated ruthenium alkylidenes, however, have not been considered as a viable alternative because alkene coordination is a necessary step in the catalytic cycle. Relying on common design principles with varying steric and electronic factors, a series of structurally diverse alkene-chelated ruthenium alkylidene complexes were prepared by trapping the intermediates of enyne ring-closing metathesis (RCM) of 1,n-enynes and diynes with a stoichiometric amount of an initiator ruthenium complex. One of the crucial structural elements that promotes the formation of 1,5-alkenechelates is the exo-Thorpe.Ingold effect, exerted by a gem-dialkyl moiety. These alkene-chelated complexes show a trans relationship between the N-heterocyclic carbene (NHC) ligand and the chelated alkene. On the other hand, η3-vinyl alkylidene complexes were generated from the RCM of ynamide-tethered 1,n-enynes. The presence of an ynamide moiety with a right connectivity is essential for the formation of these rare η3-vinyl alkylidene complexes with a cis relationship between the N-heterocyclic carbene (NHC) ligand and the chelated alkene. The stability and reactivity of these alkene-chelated ruthenium alkylidenes could be finely tuned to show characteristic behaviors in RCM, cross-metathesis (CM), and ring-opening metathesis polymerization (ROMP) reactions.
- Gupta, Saswata,Sabbasani, Venkata R.,Su, Siyuan,Wink, Donald J.,Lee, Daesung
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- Lipase-catalyzed kinetic resolution of cyclic trans-1,2-diols bearing a diester moiety: Synthetic application to chiral seven-membered-ring α,α-disubstituted α-amino acid
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(Chemical Equation Presented) Chiral cycloalkane-trans-1,2-diols (±)-3 and (±)-8 having a diester moiety have been prepared from dimethyl dialkenylmalonate using olefin metathesis by Grubbs catalyst, followed by epoxidation and acidic hydrolysis. Kinetic
- Tanaka, Masakazu,Demizu, Yosuke,Nagano, Masanobu,Hama, Mariko,Yoshida, Yukio,Kurihara, Masaaki,Suemune, Hiroshi
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- Synthesis, molecular modeling and preliminary biological evaluation of 1-amino-3-phosphono-3-cyclopentene-1-carboxylic acid and 1-amino-3-phosphono-2-cyclopentene-1-carboxylic acid, two novel agonists of metabotropic glutamate receptors of group III
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On the basis of a pharmacophore definition of mGlu4 agonists, the two novel semi-rigid derivatives 12 and 13 were designed and synthesized. The preliminary biological evaluation demonstrated that both compounds interact with hmGlu(4a), while ineffective at group II receptor subtypes. In particular, derivative 13 is a full hmGlu(4a) agonist with an EC50=17 μM. (C) 2000 Elsevier Science Ltd. All rights reserved.
- Amori, Laura,Costantino, Gabriele,Marinozzi, Maura,Pellicciari, Roberto,Gasparini, Fabrizio,Flor, Peter J.,Kuhn, Rainer,Vranesic, Ivo
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- A simple oxidative procedure for the removal of ruthenium residues from metathesis reaction products
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Ruthenium residues can be easily and rapidly removed from Grubbs metathesis products by washing with 15% aqueous hydrogen peroxide, which converts any ruthenium complexes into highly insoluble ruthenium dioxide, which then catalyzes the conversion of excess peroxide into water and oxygen. Ruthenium levels lower than 2 ppm can be routinely obtained; an additional advantage is that any phosphines are also rapidly oxidized to the corresponding, more polar phosphine oxides thereby facilitating their removal as well in many cases.
- Knight, David W.,Morgan, Ian R.,Proctor, Anthony J.
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- Ruthenium hydroxycarbenes as key intermediates in cycloisomerization and decarbonylative cyclization of terminal alkynals
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The complex [Ru(η5-C5H5)(CO) (κ1-OCMe2)(PiPr3)] BF 4 (1) reacts with 3,3-bis(methoxycarbonyl)-5-hexyn-1-al to give the α,β-unsaturated cyclopentenylhydroxycarbene derivative [Ru(η5-C5H5){=C(OH)C=CHCH 2C(CO2CH3)2CH2}(CO) (PiPr3)]BF4 (2), which undergoes deprotonation with Al2O3 to afford Ru(η5-C 5H5){C(O)C=CHCH2C(CO2CH 3)2CH2}(CO) (PiPr3) (3). In the presence of P2O5, the reaction of 1 with the alkynal leads to the alkenylvinylidene [Ru(η5-C5H 5){=C=C-CH=CH-C(CO2CH3)2-CH 2}(CO)(PiPr3)]BF4 (4), which yields the β,γ-unsaturated cyclopentenylhydroxycarbene [Ru(η 5-C5H5){C(OH)CHCH=CHC(CO2CH 3)2CH2}(CO)(PiPr3)] BF4 (5) by means of a 1,2-addition of water. Complex 5 slowly isomerizes into 2. The deprotonation of 5 with Al2O3 gives Ru(η5-C5H5){C(O)CHCH=CHC(CO 2CH3)2CH2}(CO)(PiPr 3) (6). Solvate Ru complex 1 and Ru hydroxycarbene 2 catalyze the cyclization of 3,3-bis(methoxycarbonyl)-5-hexyn-1-al to give mixtures of the cycloisomerized aldehyde 1,1-bis(methoxycarbonyl)-3-formylcyclopent-3-ene (7) and cycloalkene 1,1-bis(methoxycarbonyl)cyclopent-3-ene (8).
- Batuecas, Maria,Esteruelas, Miguel A.,Garcia-Yebra, Cristina,Gonzalez-Rodriguez, Carlos,Onate, Enrique,Saa, Carlos
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- Generation and spectroscopic characterization of ruthenacyclobutane and ruthenium olefin carbene intermediates relevant to ring closing metathesis catalysis
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The reaction of phosphonium alkylidenes [(H2IMes)RuCl 2=CHPR3]+[A]- (R = C 6H11, A = OTf or B(C6F5) 4, 1-Cy; R = i-C3H7, A = CIB(C 6F5)3 or OTf, 1-iPr) with 1 equiv of ethylene at -78°C, in the presence of 2-3 equiv of a trapping olefin substrate, yields intermediates relevant to olefin metathesis catalytic cycles. Dimethyl cyclopent-3-ene-1,1-dicarboxylate gives solutions of a substituted ruthenacy-clobutane 3 of relevance to ring closing metathesis catalysis. 1H and 13C NMR data are fully consistent with its assignment as a ruthenacyclobutane, but 1JCC values of 23 Hz for the CαH2-Cβ bond and 8.5 Hz for the CαH-Cβ bond point to an unsymmetrical structure in which the latter bond is more activated than the former. In contrast, trapping with acenaphthylene leads to an olefin carbene complex (6) in which the putative ruthenacyclobutane has opened; this species was also fully characterized by NMR spectroscopy and compared to related species reported previously.
- Van Der Eide, Edwin F.,Romero, Patricio E.,Piers, Warren E.
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- Ruthenabenzene: A Robust Precatalyst
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Metallaaromatics constitute a unique class of aromatic compounds where one or more transition metal elements are incorporated into the aromatic system, the parent of which is metallabenzene. One of the main concerns about metallabenzenes generally deals with the structural characterization related to their relative aromaticity compared to the carbon archetype. Transition metal-containing metallabenzenes are also implicated in certain catalytic processes such as alkyne metathesis polymerization; however, these transition metal-based metallaaromatic compounds have not been developed as a catalyst. Herein, we describe an effective strategy to generate diverse arrays of ruthenabenzenes and demonstrated them as an aromatic equivalent of the Grubbs-type ruthenium alkylidene catalysts. These ruthenabenzenes can be prepared via an enyne metathesis and metallotropic [1,3]-shift cascade process to form alkyne-chelated ruthenium alkylidene intermediates followed by spontaneous cycloaromatization. The aromatic nature of these complexes was confirmed by spectroscopic and X-ray crystallographic data, and the mechanistic pathways for the cycloaromatization process were studied by DFT calculations. These ruthenabenzenes display robust catalytic activity for metathesis and other transformations, which illustrates that metallabenzenes are not only compounds of structural and theoretical interests but also are a novel platform for new catalyst development.
- Gupta, Saswata,Su, Siyuan,Zhang, Yu,Liu, Peng,Wink, Donald J.,Lee, Daesung
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supporting information
p. 7490 - 7500
(2021/05/26)
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- NHC (N-heterocyclic carbene) ligand, ruthenium catalyst thereof, preparation methods and application
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The invention relates to an NHC (N-heterocyclic carbene) ligand, a ruthenium catalyst thereof, preparation methods and an application of the catalyst. The NHC ligand structures are shown in formulas Ia and Ib respectively, and the corresponding ruthenium catalyst structures are shown in formulas IIa and IIb respectively. After large steric hindrance and electron-rich groups are simultaneously introduced to the NHC ligand structures, the catalytic activity and the stability of the ruthenium complex catalyst of the NHC ligand are notably improved, and the application range of the ruthenium complex catalyst of the NHC ligand is notably enlarged.
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Paragraph 0151--0158
(2019/08/02)
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- Ruthenium dihydride complexes as enyne metathesis catalysts
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Ruthenium–catalyzed enyne metathesis is a reliable and efficient method for the formation of 1,3-dienes, a common structural motif in synthetic organic chemistry. The development of new transition-metal complexes competent to catalyze enyne metathesis rea
- Dolan, Martin A.,Dixon, Alexandre D.C.,Chisholm, John D.,Clark, Daniel A.
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supporting information
p. 4471 - 4474
(2018/11/23)
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- Development of a One-Pot Four C-C Bond-Forming Sequence Based on Palladium/Ruthenium Tandem Catalysis
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A one-pot four C-C bond-forming sequence has been developed using two distinct transition metal complexes. The sequence entails a double Pd-catalyzed allylic alkylation followed by a Ru-catalyzed ring-closing metathesis and a Pd-catalyzed Heck coupling. The use of various active methylene nucleophiles was examined with yields up to 76% (93% per C-C bond).
- Manick, Anne-Doriane,Berhal, Farouk,Prestat, Guillaume
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supporting information
p. 194 - 197
(2018/01/17)
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- Helical structures of cyclopentenebased α,α-disubstituted a-amino acid homopeptides
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The cyclopentene-based α,α-disubstituted a-amino acid Ac5c= and its homopeptides, up to nonapeptides, were synthesized. The side-chain cyclopentene was expected to become symmetric, the Ca-carbon to be puckered, and other Cβ, Cβ', C, C-carbons to be coplanar. As expected, side-chain cyclopentene conformations became symmetric and Ca-carbons were puckered. Conformational studies using FT-IR absorption, 1H NMR spectra, and X-ray crystallographic analyses revealed that Ac5c= homopeptides did not form a planar conformation, but assumed a 310-helical structure, similar to cyclopentane-based α,α-disubstituted a-amino acid homopeptides.
- Tanaka, Masakazu,Yakabi, Haruka,Nakatani, Haruki,Ueda, Atsushi,Doi, Mitsunobu,Oba, Makoto
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p. 848 - 852
(2019/01/21)
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- A partially serendipitous discovery of thermo-switchable ruthenium olefin metathesis initiator that seem to be well suited for ROMP of monomers bearing vinyl pendant groups
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A latent Ru olefin metathesis catalyst bearing a chelating ligand with an azoxybenzene fragment was obtained and characterized. The complex was inactive in the ring closing metathesis (RCM) reaction of a standard test diene: diethyl diallylmalonate at room temperature but can be subsequently activated by elevated temperature (up to 100 °C). The lack of activity of this azoxy catalyst in RCM of dienes containing terminal C-C double bonds at room temperature and high activity in ring opening metathesis polymerization (ROMP) of bicyclo [2.2.1]hept-2-ene (norbornene, NBE) permitted the ROMP of the challenging monomer: 5-vinyl-2-norbornene yielding soluble polymers with cyclopentenylenevinylene chains with vinyl pendant groups.
- Szwaczko, Katarzyna,Czelu?niak, Izabela,Grela, Karol
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supporting information
p. 146 - 153
(2017/09/12)
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- Ruthenium Catalysts Supported by Amino-Substituted N-Heterocyclic Carbene Ligands for Olefin Metathesis of Challenging Substrates
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N-Heterocyclic carbene (NHC) ligands IMes (Formula presented.) and IMes (Formula presented.) derived from the well-known IMes ligand by substituting the carbenic heterocycle with one and two dimethylamino groups, respectively, were employed for the synthesis of second-generation Grubbs- and Grubbs–Hoveyda-type ruthenium metathesis precatalysts. Whereas the stability of the complexes was found to depend on the degree of dimethylamino-substitution and on the type of complex, the backbone-substitution was shown to have a positive impact on their catalytic activity in ring-closing metathesis, with a more pronounced effect in the second-generation Grubbs-type series. The new complexes were successfully implemented in a number of challenging olefin metathesis reactions leading to the formation of tetra-substituted C=C double bonds and/or functionalized compounds.
- César, Vincent,Zhang, Yin,Ko?nik, Wioletta,Zieliński, Adam,Rajkiewicz, Adam A.,Ruamps, Mirko,Bastin, Stéphanie,Lugan, No?l,Lavigne, Guy,Grela, Karol
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supporting information
p. 1950 - 1955
(2017/02/15)
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- A Ruthenium Catalyst for Olefin Metathesis Featuring an Anti-Bredt N-Heterocyclic Carbene Ligand
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A ruthenium complex bearing an "anti-Bredt" N-heterocyclic carbene was synthesized, characterized and evaluated as a catalyst for olefin metathesis. Good conversions were observed at room temperature for the formation of di- A nd tri-substituted olefins b
- Martin, David,Marx, Vanessa M.,Grubbs, Robert H.,Bertrand, Guy
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p. 965 - 969
(2016/04/05)
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- Synthesis of Polycycles by Single or Double Domino Nucleophilic Substitution/Diels-Alder Reaction
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New hexacyclo and octacyclo compounds have been synthesized by a short route whose key step consists of a single or double domino nucleophilic substitution of neopentyl-type iodides with potassium cyclopentadienide, followed by intramolecular Diels-Alder cycloaddition.
- Camps, Pelayo,Lozano, David,Font-Bardia, Mercè
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p. 5013 - 5020
(2015/08/03)
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- Enantioselective desymmetrization via carbonyl-directed catalytic asymmetric hydroboration and Suzuki-Miyaura cross-coupling
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The rhodium-catalyzed enantioselective desymmetrization of symmetric γ,δ-unsaturated amides via carbonyl-directed catalytic asymmetric hydroboration (directed CAHB) affords chiral secondary organoboronates with up to 98% ee. The chiral γ-borylated products undergo palladium-catalyzed Suzuki-Miyaura cross-coupling via the trifluoroborate salt with stereoretention.
- Hoang, Gia L.,Yang, Zhao-Di,Smith, Sean M.,Miska, Judy L.,Prez, Damaris E.,Zeng, Xiao Cheng,Takacs, James M.,Pal, Rhitankar,Pelter, Libbie S. W.
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supporting information
p. 940 - 943
(2015/03/30)
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- Heck-Matsuda arylation of olefins through a bicatalytic approach: Improved procedures and rationalization
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The scope of the palladium-catalyzed Heck-Matsuda reaction, proceeding through the catalytic activation of anilines into the corresponding diazonium salts, has been considerably extended and is now working with deactivated electrophiles. Two different procedures, using catalytic amounts of both palladium and acid, have been optimized allowing the concept of bicatalysis to cover the complete electronic range of anilines. These environmentally friendly procedures proceed under very mild conditions, at room temperature in methanol, and only generate tert-butyl alcohol, water and nitrogen as by-products. Rationalization of reaction outcomes encountered in this work has been discussed with the support of computational studies.
- Oger, Nicolas,Le Callonnec, Francois,Jacquemin, Denis,Fouquet, Eric,Le Grognec, Erwan,Felpin, Francois-Xavier
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supporting information
p. 1065 - 1071
(2014/04/03)
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- Stereoselective arylation of substituted cyclopentenes by substrate-directable Heck-Matsuda reactions: A concise total synthesis of the sphingosine 1-phosphate receptor (S1P1) agonist VPC01091
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We describe herein an efficient and diastereoselective substrate-directable Heck-Matsuda reaction with nonactivated five-membered olefins. The carbamate acts as the main directing group in the arylation process allowing the synthesis of several functionalized aryl cyclopentenes in good to excellent diastereoselectivities (>85:15) and in isolated yields ranging from 41 to 90%. No double bond isomerizations were observed in these Heck reactions, and the newly created benzylic centers were preserved in all cases examined. The substrate directable Heck arylation approach was successfully applied in a straightforward total synthesis of the sphingosine 1-phosphate receptor-subtype 1 (S1P1) agonist VPC01091 by a concise and practical route involving 5 steps in 40% overall yield.
- Oliveira, Caio C.,Dos Santos, Emerson A. F.,Bormio Nunes, Julia H.,Correia, Carlos Roque D.
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p. 8182 - 8190,9
(2020/10/15)
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- Synthesis of pyrimidine-modified NHC ruthenium-alkylidene catalysts and their application in RCM, CM, em and ROMP reactions
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A new type of N-heterocyclic carbene bearing ruthenium olefin metathesis catalyst was prepared through the incorporation of a chelated pyrimidinyl methylene subunit, in which electron-rich substituents were attached to stabilize the ruthenium complexes. These catalysts were successfully used in various types of olefin metathesis reactions, including ring-closing metathesis (RCM), cross-metathesis (CM), enyne metathesis (EM), and ring-opening metathesis polymerization (ROMP) reactions. The results therein showed that the presence of an electron-deficient pyrimidine structure greatly enhanced the new NHC ruthenium complexes' catalytic activities. New N-heterocyclic carbene bearing ruthenium olefin metathesis catalysts were synthesized and applied in various types of olefin metathesis reactions, including ring-closing metathesis, cross-metathesis, enyne metathesis, and ring-opening metathesis polymerization reactions. Copyright
- Wu, Guang-Long,Cao, Sheng-Li,Chen, Jian,Chen, Zili
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p. 6777 - 6784
(2013/01/15)
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- A simple diamine as ligand in iron-catalyzed regioselective allylic alkylation
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A simple and efficient diamine was found to be an efficient ligand for the iron-catalyzed regioselective allylic alkylation between various allyl carbonates and nucleophiles, affording excellent yields and good regioselectivity (up to 94% and >20:1).
- Yu, Chenguang,Zhou, Aihua,He, Jing
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p. 8627 - 8630
(2015/02/19)
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- A metathesis approach to volatile olefins: Synthesis of 18O-allyl alcohol
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A neat reaction: A ring-closing metathesis (RCM) strategy is presented in which the two termini of a light, and thus volatile, isotopically labelled olefin are held separate by way of a higher molecular weight diene component, allowing synthetic manipulat
- Lloyd-Jones, Guy C.,Purser, Sophie
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scheme or table
p. 4724 - 4726
(2011/05/17)
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- Synthesis of methyl-1-(tert -butoxycarbonylamino)-2- vinylcyclopropanecarboxylate via a hofmann rearrangement utilizing trichloroisocyanuric acid as an oxidant
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A trichloroisocyanuric acid (TCCA) mediated Hofmann rearrangement was utilized to synthesize methyl-1-(tert-butoxycarbonylamino)-2- vinylcyclopropanecarboxylate. A variety of functional groups are tolerated in this reaction including vinyl, cyclopropyl, pyridyl, aryl, benzyl, and nitro groups.
- Crane, Zackary D.,Nichols, Paul J.,Sammakia, Tarek,Stengel, Peter J.
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supporting information; experimental part
p. 277 - 280
(2011/03/20)
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- Ruthenium-indenylidene olefin metathesis catalyst with enhanced thermal stability
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Two new ruthenium complexes bearing a bidentate (κ2O,C)- isopropoxy-indenylidene ligand and a PPh3 (9) or PCy3 (10, Cy=cyclohexyl) ligand have been synthesized and fully characterized by 1H and 13C NMR spectroscopy and X-ray crystallography. Complex 10 displays a very high thermal stability with a half life of six days at 110°C in [D8]toluene. Complex 10 was evaluated in various ring-closing metathesis reactions and ring-opening metathesis polymerization of dicyclopentadiene, in which it showed a latent behavior with low activity at room temperature and high activity upon thermal activation. Hot catalysts! Two new ruthenium complexes bearing a bidentate (κ2O,C)-isopropoxy- indenylidene ligand and a PPh3 or PCy3 (1, Cy=cyclohexyl; see picture) ligand are thermally stable catalysts. Complex 1 displays a latent behavior in olefin-metathesis transformations and possesses a very high thermal stability with a half life of six days at 110°C in [D8]toluene. This complex features very low activity at room temperature and higher activity upon thermal activation.
- Kabro, Anzhelika,Roisnel, Thierry,Fischmeister, Cedric,Bruneau, Christian
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supporting information; experimental part
p. 12255 - 12261
(2011/02/22)
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- Synthesis of (±)-1,2,3-triazolo-3′-deoxy-4′-hydroxymethyl carbanucleosides via 'click' cycloaddition
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The synthesis of 1,2,3-triazolo-3′-deoxy-4′-hydroxymethyl carbanucleosides with different reaction conditions and diverse modulations on the heterocycle residues was developed. Heterocycle moieties were efficiently introduced on the pseudo-sugar either vi
- Broggi, Julie,Joubert, Nicolas,Díez-González, Silvia,Berteina-Raboin, Sabine,Zevaco, Thomas,Nolan, Steven P.,Agrofoglio, Luigi A.
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experimental part
p. 1162 - 1170
(2009/05/07)
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- Allylic alkylation and ring-closing metathesis in sequence: A successful cohabitation of Pd and Ru
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An allylic alkylation/ring-closing metathesis domino catalytic process, wherein a palladium and a ruthenium catalyst are concomitantly present in the reaction mixture from the outset of the reaction, is developed. Evidence for Grubbs' catalysts activity in allylic alkylation is also reported.
- Kammerer, Claire,Prestat, Guillaume,Gaillard, Thomas,Madec, David,Poli, Giovanni
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p. 405 - 408
(2008/09/19)
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- Alkyne-azide click chemistry mediated carbanucleosides synthesis
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Hitherto unknown 1,4-disubstituted-[1,2,3]-triazolo-4′,4′- dihydroxymethyl-3′-deoxy carbanucleosides were synthesized based on a "click approach." Various alkynes were introduced on a key azido intermediate by the "click" 1,3-dipolar Huisgen cycloaddition
- Broggi, Julie,Joubert, Nicolas,Aucagne, Vincent,Berteina-Raboin, Sabine,Diez-Gonzalez,Nolan, Steve,Topalis, Dimitri,Deville-Bonne, Dominique,Balzarini, Jan,Neyts, Johan,Andrei, Graciela,Snoeck, Robert,Agrofoglio, Luigi A.
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p. 1391 - 1394
(2008/09/18)
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- Ru-catalyzed cyclization of terminal alkynals to cycloalkenes
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Cycloalkenes can be efficiently prepared by a new Ru-catalyzed cyclization of terminal alkynals. Under appropriate conditions, cycloisomerizations to conjugated aldehydes may be observed. Both processes involve catalytic Ru vinylidenes. Copyright
- Varela, Jesus A.,Gonzalez-Rodriguez, Carlos,Rubin, Silvia G.,Castedo, Luis,Saa, Carlos
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p. 9576 - 9577
(2007/10/03)
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- A flexible, efficient synthesis of (±)-carbocyclic phosphonic acid nucleoside derivatives
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An efficient and flexible synthesis of cyclopentane and hydroxylated cyclopentane phosphonic acid analogues is described. The key step involves the opening of an epoxide with either a nucleoside base or a selenyl anion to access the target molecules.
- Wainwright, Phillip,Maddaford, Adrian,Bissell, Richard,Fisher, Ray,Leese, David,Lund, Andrew,Runcie, Karen,Dragovich, Peter S.,Gonzalez, Javier,Kung, Pei-Pei,Middleton, Donald S.,Pryde, David C.,Stephenson, Peter T.,Sutton, Scott C.
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p. 765 - 768
(2007/10/03)
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- Highly active silica gel-supported metathesis (pre)catalysts
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Highly active Hoveyda-Grubbs and Hoveyda-Blechert type (pre)catalysts, immobilized on silica gel, are presented. These (pre)catalysts are synthesized in a few steps from readily available precursors and demonstrate high activity in a number of test metath
- Fischer, Dirk,Blechert, Siegfried
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p. 1329 - 1332
(2007/10/03)
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- Indium(III) Chloride-Promoted Intramolecular Addition of Allylstannanes to Alkynes
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In the presence of an equimolar amount of InCl3, 8-tributylstannyl-6-octen-1-ynes (allylstannanes bearing an alkynyl group) were efficiently cyclized to 2-allyl-1-methylenecyclopentanes. In contrast, catalytic use of InCl3 gave 2-all
- Miura, Katsukiyo,Fujisawa, Naoki,Hosomi, Akira
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p. 2427 - 2430
(2007/10/03)
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- Microwave-assisted rutheniun-catalyzed olefin metathesis under solvent-free conditions
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An efficient method for ring-closing metathesis under solvent-free conditions and by microwave activation was esteblished. Non-thermal microwave specific effects were evident.
- Thanh, Giang Vo,Loupy, Andre
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p. 9091 - 9094
(2007/10/03)
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- Photopolymerizable vinyl ether based monomeric formulations and polymerizable compositions which may include certain novel spiroorthocarbonates
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Photopolymerizable compositions are provided which are the reaction products of a vinyl ether, a photoinitiator system comprising an iodonium salt, a visible light sensitizer, and an electron donor compound. These monomeric/oligomeric compositions may also include epoxides, polyols, spiroorthocarbonates. One embodiment of the present invention is a polymerizable composition comprised of a vinyl ether, a spiroorthocarbonate, and a photoinitiator system. Another embodiment of the present invention is a polymerizable composition comprised of a vinyl ether, an epoxide, a polyol, and a photoinitiator system. Still another embodiment of the present invention is a polymerizable composition comprised of a vinyl ether, an epoxide, a polyol, a spiroorthocarbonate, and a photoinitiator system. Still further, another embodiment of the present invention is certain novel spiroorthocarbonate compounds. Each of these novel spiroorthocarbonate compounds include at least one epoxy group as a substituent.
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- Microencapsulation of a metathesis catalyst
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Microencapsulation of the saturated N-heterocyclic carbene metathesis catalyst 4 in polystyrene gives a material that is catalytically active, and is easily recovered and reused.
- Gibson, Susan E.,Swamy, Vishwanath M.
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p. 619 - 621
(2007/10/03)
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- Coordinatively unsaturated ruthenium allenylidene complexes: Highly effective, well defined catalysts for the ring-closure metathesis of αω-dienes and dienynes
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The well defined, conveniently accessible and coordinatively unsaturated allenylidene complexes [RuCl2(=C=C=CPh2)(PCy3)2] and [Ru2Cl4(=C=C=CPh2)(PCy3)(n-MeC6/sub
- Fuerstner, Alois,Hill, Anthony F.,Liebl, Monika,Wilton-Ely, James D. E. T.
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p. 601 - 602
(2007/10/03)
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- Selective generation of free radicals from epoxides using a transition-metal radical. A powerful new tool for organic synthesis
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Bis(cyclopentadienyl)titanium(III) chloride reacts with epoxides by initial C-O homolysis. The regiochemistry of the opening is determined by the relative stabilities of the radicals. Depending on the reaction partners, these radicals undergo intramolecular (hex-5-enyl cyclization) or intermolecular additions to olefins. The resultant radicals are efficiently scavenged by a second equivalent of Ti(III) to afford the corresponding Ti(IV) derivative. Treatment of this intermediate with electrophiles such as H+ or halogens provides a route to functionalized cyclopentanes and other useful products. The radical initially formed from an epoxide can also be trapped by H-atom donors such as 1,4-cyclohexadiene or tert-butyl thiol, resulting in an overall reduction of the epoxide. In the absence of a H-atom donor or an olefin, this radical is trapped by Ti(III), resulting in a β-oxido-Ti organometallic species which undergoes facile elimination to give an olefin. The reaction conditions are remarkably mild and are applicable to very sensitive substrates.
- RajanBabu,Nugent, William A.
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p. 986 - 997
(2007/10/02)
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