- Biscarbene palladium(II) complexes. reactivity of saturated versus unsaturated N-heterocyclic carbenes
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A series of designed palladium biscarbene complexes including saturated and unsaturated N-heterocyclic carbene (NHC) moieties have been prepared by the carbene transfer methods. All of these complexes have been characterized by 1H and 13C NMR spectroscopy as well as X-ray diffraction analysis. The reactivity of Pd-C(saturated NHC) is distinct from that of Pd-C(unsaturated NHC). The Pd-C(saturated NHC) bonds are fairly stable toward reagents such as CF3COOH, AgBF4 and I2, whereas Pd-C(unsaturated NHC) bonds are readily cleaved under the similar conditions. Notably, the catalytically activity of these palladium complexes on Suzuki-Miyaura coupling follows the order: (sat-NHC)2PdCl2 > (sat-NHC)(unsat-NHC)PdCl2 > (unsat-NHC)2PdCl2.
- Fu, Ching-Feng,Lee, Chun-Chin,Liu, Yi-Hung,Peng, Shie-Ming,Warsink, Stefan,Elsevier, Cornelis J.,Chen, Jwu-Ting,Liu, Shiuh-Tzung
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- NHC-mediated synthesis of an asymmetric, cationic phosphoranide, a phosphanide, and coinage-metal phosphanido complexes
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A cationic phosphoranide featuring a normal and an abnormal imidazoliumyl substituent was prepared through the reaction of a P-centered cation with an N-heterocyclic carbene (NHC). The remarkable reactivity of this compound allows the formation of two- or three-coordinate P-centered cations, illustrating the ability of imidazoliumyl substituents to stabilize high- and low-coordinated P atoms. Copyright
- Schwedtmann, Kai,Holthausen, Michael H.,Feldmann, Kai-Oliver,Weigand, Jan J.
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- Reaction of N-heterocyclic carbene (NHC) with different HF sources and ratios – A free fluoride reagent based on imidazolium fluoride
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Treatment of N-heterocyclic carbene (1,3-Bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene; (LDipp)) with different sources of hydrofluoric acid (Et3N?3HF, anhydrous hydrofluoric acid and KHF2) in 1:1, 1:2, 1:3 ratios affords [(LDipp)H]+[F]?(1), [(LDipp)H]+[(HF)F]?(2) and [(LDipp)H]+[(HF)2F]?(3) salts respectively. Different fluoride sources all yield the same products, but ease of manipulation and isolation can influence the choice in the future use. Compound (1), which shows characteristics of a free fluoride reagent, can be obtained with good yield and without the contaminants usually present in such compounds. All products were characterized by X-Ray crystallography, NMR spectroscopy and free fluoride (Ff ?) chemical analysis.
- Ali?, Bla?,Tav?ar, Ga?per
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- Fast and Slow Release of Catalytically Active Species in Metal/NHC Systems Induced by Aliphatic Amines
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The behavior of ubiquitously used nickel, palladium, and platinum complexes containing N-heterocyclic carbene ligands was studied in solution in the presence of aliphatic amines. Transformation of M(NHC)X2L complexes readily occurred according to the following reactions: (i) release of the NHC ligand in the form of azolium salt and formation of metal clusters or nanoparticles and (ii) isomerization of mono-NHC complexes M(NHC)X2L to bis-NHC derivatives M(NHC)2X2. Facile cleavage of the M-NHC bond was observed and provided the possibility for fast release of catalytically active NHC-free metal species. Bis-NHC metal complexes M(NHC)2X2 were found to be significantly more stable and represented a molecular reservoir of catalytically active species. Slow decomposition of the bis-NHC complexes by removal of the NHC ligands (also in the form of azolium salts) occurred, generating metal clusters or nanoparticles. The observed combination of dual fast- and slow-release channels is an intrinsic latent opportunity of M/NHC complexes, which balances the activity and durability of a catalytic system. The fast release of catalytically active species from M(NHC)X2L complexes can rapidly initiate catalytic transformation, while the slow release of catalytically active species from M(NHC)2X2 complexes can compensate for degradation of catalytically active species and help to maintain a reliable amount of catalyst. The study clearly shows an outstanding potential of dynamic catalytic systems, where the key roles are played by the lability of the M-NHC framework rather than its stability.
- Khazipov, Oleg V.,Shevchenko, Maxim A.,Chernenko, Andrey Yu.,Astakhov, Alexander V.,Pasyukov, Dmitry V.,Eremin, Dmitry B.,Zubavichus, Yan V.,Khrustalev, Victor N.,Chernyshev, Victor M.,Ananikov, Valentine P.
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- Modular Ni(0)/Silane Catalytic System for the Isomerization of Alkenes
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Alkenes are used ubiquitously as starting materials and synthetic targets in all areas of chemistry. Controlling their geometry and position along a chain is vital to their reactivity and properties yet remains challenging. Alkene isomerization is an atom-economical process to synthesize targeted alkenes, and selectivity can be controlled using transition metal catalysts. The development of mild, selective isomerization reactivity has enabled efficient tandem catalytic systems for the remote functionalization of alkenes, a process in which a starting alkene is isomerized to a new position prior to the functionalization step. The key challenges in developing isomerization catalysts for remote functionalization applications are (i) a lack of modularity in the catalyst structure and (ii) the requirement of nonmodular and/or harsh additives during catalyst activation. We address both challenges with a modular (NHC)Ni(0)/silane catalytic system (NHC, N-heterocyclic carbene), demonstrating the use of triaryl silanes and readily accessible (NHC)Ni(0) complexes to form the proposed active (NHC)(silyl)Ni-H species in situ. We show that modification of the steric and electronic nature of the catalyst via modification of the ancillary ligand and silane partner, respectively, is easily achieved, creating a uniquely versatile catalytic system that is effective for the formation of internal alkenes with high yield and selectivity for the E-alkene. The use of silanes as mild activators enables isomerization of substrates with a variety of functional groups, including acid-labile groups. The broad substrate scope, enabled by catalyst design, makes this catalytic system a strong candidate for use in tandem catalytic applications. Preliminary mechanistic studies support a Ni-H insertion/elimination pathway.
- Chang, Alison Sy-Min,Cook, Amanda K.,Kawamura, Kiana E.,Martin, Daryl J.,Morris, Parker T.,Smith, Haley M.
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supporting information
p. 486 - 496
(2022/03/02)
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- N-Heterocyclic carbene palladium (II)-pyridine (NHC-Pd (II)-Py) complex catalyzed heck reactions
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A mild, efficient, and practical catalytic system for the synthesis of highly privileged stilbene pharmacophores is reported. This system uses N-heterocyclic carbene palladium (II) Pyridine (NHC-Pd (II)-Py) complex to catalyze the formation of carbon-carbon bonds between olefin derivatives and various bromide. This simple, gentle and user-friendly method can offer a variety of stilbene products in excellent yields under solvent-free condition. And its scale-up reaction has excellent yield and this system can be applied to industrial fields. The utility of this method is highlighted by its universality and modular synthesis of a series of bioactive molecules or important medical intermediates.
- Li, Dan,Tian, Qingqiang,Wang, Xuetong,Wang, Qiang,Wang, Yin,Liao, Siwei,Xu, Ping,Huang, Xin,Yuan, Jianyong
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supporting information
p. 2041 - 2052
(2021/05/25)
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- Preparation method of NHC-PdCl2-3-chloropyridine complex
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The invention relates to a preparation method of an NHC-PdCl2-3-chloropyridine complex. The preparation method comprises the following steps: subjecting 2,6-diisopropylaniline, glyoxal and acetic acid to reacting in an ethanol solvent for 2-4 days to obtain glyoxal-bis-(2,6-diisopropylphenyl)imine; stirring a mixed solution of glyoxal-bis-(2,6-diisopropylphenyl)imine, chloromethylethyl ether, tetrahydrofuran and water at 30-50 DEG C for a reaction for 10-20 hours to obtain 1,3-bis-(2,6-diisopropylphenyl)imidazolium chloride, wherein a molar ratio of glyoxal-bis-(2,6-diisopropylphenyl)imine to water is 1: (2-10); and subjecting 1,3-bis-(2,6-diisopropylphenyl)imidazolium chloride, palladium chloride, cesium carbonate and 3-chloropyridine to reacting for 10-20 hours at a temperature of 60-100 DEG C to obtain [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](3-chloropyridyl)palladium (II) dichloride. The method has the advantages that raw materials are easy to obtain, operation is simple, reaction conditions are mild and easy to control and industrial mass production is easy.
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Paragraph 0029; 0033-0035; 0041-0042; 0043-0044; 0045-0046
(2021/05/08)
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- Stable Singlet Carbenes as Organic Superbases
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A simple experimental procedure for scaling carbene Br?nsted basicity is described. The results highlight the strong basicity of pyrazol-4-ylidenes, a type of mesoionic carbene, also named cyclic-bentallenes (CBA). They are more basic (pKaH >42.7 in acetonitrile) than the popular proazaphosphatrane Verkade bases, and even the Schwesinger phosphazene superbase P4(tBu). The basicity of these compounds can readily be tuned, and they are accessible in multigram quantities. These results open new avenues for carbon centered superbases.
- Bertrand, Guy,Grotjahn, Douglas B.,Jazzar, Rodolphe,Junor, Glen P.,Vermersch, Fran?ois,Yazdani, Sima
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p. 27253 - 27257
(2021/11/22)
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- Application of Quantitative 1H and 19F NMR to Organometallics
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Purity assessment of organometallics is particularly important for catalytic applications. While quantitative NMR is a well-known method in pharmaceutic chemistry, the present work illustrates its usefulness for the determination of the ligands and organometallics purities using proton and fluorine NMR. This method is fast, straightforward and provides accuracy results.
- Akhdar, Ayman,Andanson, Jean-Michel,Faure, Sophie,Gautier, Arnaud,Tra?kia, Mounir
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- Iron-based compound as well as preparation method and application thereof
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The invention discloses an iron-based compound as well a a preparation method and application thereof, and belongs to the technical field of thickened oil viscosity reduction exploitation. The preparation method comprises the following steps of: mixing 1, 3-bis (2, 6-diisopropyl-1-phenyl) imidazolium chloride, potassium tert-butoxide and a first organic solvent, and carrying out stirring for a reaction to obtain free N-heterocyclic carbene; and mixing the free N-heterocyclic carbene, an iron source and a second organic solvent, and carrying out stirring for a reaction to obtain the iron-based compound. The invention also comprises an iron-based compound prepared by the preparation method. In addition, the invention also provides application of the iron-based compound in catalytic degradation of thickened oil. The degradation rate of the iron-based compound provided by the invention on heavy oil can reach 85%.
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- Preventing Pd-NHC bond cleavage and switching from nano-scale to molecular catalytic systems: Amines and temperature as catalyst activators
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Many reactions catalyzed by Pd complexes with N-heterocyclic carbene (NHC) ligands are performed in the presence of amines which usually act as coupling reagents or mild bases. However, amines can react with Pd/NHC complexes in a number of ways: enhancing molecular catalysis, causing the catalyst deactivation or triggering the ligandless modes of catalysis by producing NHC-free active palladium species. This study gains insight into conditions required for the efficient use of amines as activators of molecular Pd/NHC catalysis and preventing the undesirable reductive cleavage of the Pd-NHC bond in catalytic systems. Reactions of Pd/NHC complexes with various amines within a temperature range of 25-140 °C and thermal stability of the resulting amino-complexes are examined. The results indicate the major influence of the amine structure and reaction temperature on the catalyst transformation. In particular, thermal decomposition of Pd/NHC complexes with aliphatic amine ligands predominantly leads to reductive Pd-NHC bond cleavage, while deprotonation of the complexes with primary and secondary aliphatic amine ligands in the presence of strong bases at 25-60 °C promotes the activation of molecular Pd/NHC catalysis. Efficient Pd-PEPPSI complex-amine systems suitable for strong-base-promoted C-S cross-coupling reactions between aryl halides and thiols are suggested on the basis of these findings.
- Ananikov, Valentine P.,Astakhov, Alexander V.,Chernenko, Andrey Yu.,Chernyshev, Victor M.,Khazipov, Oleg V.,Pasyukov, Dmitry V.,Shevchenko, Maxim A.,Tafeenko, Victor A.
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p. 1228 - 1247
(2020/03/26)
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- Method for preparing substituted aryl ketone by ketone arylation (by machine translation)
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The invention provides a method, for preparing substituted aryl ketone, by using a nitrogen heterocyclic carbene catalyst, with a saturated nitrogen heterocyclic carbene structure in an oxygen-containing atmosphere at, through α - catalysis of a nitrogen heterocyclic carbene structure, in a nitrogen heterocyclic carbene catalyst with a saturated nitrogen heterocyclic carbene structure under an alkaline condition, in an oxygen-containing atmosphere and can efficiently prepare various substituted, aryl ketones α - under the condition of containing an oxygen. atmosphere. (by machine translation)
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Paragraph 0026; 0029
(2020/03/05)
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- Mechanism studies of oxidation and hydrolysis of Cu(I)–NHC and Ag–NHC in solution under air
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The decomposition of copper(I)–NHC and silver-NHC complexes in solution under air was studied. The Cu(I)–NHCs were oxidized into urea derivatives and hydrolysed into imidazoliums or benzimidazoliums. The decomposition of Ag–NHC with a saturated backbone led to ring-opening product, while the Ag–NHC with an unsaturated backbone led to imidazolium and Ag-bisNHC complex. The effects of steric property, hydrophilicity, and binding energy of NHC to O2 and H2O on the decomposition of Cu(I)–NHC were studied using theoretical calculations. Steric hindrance played an important role on the stability of Cu(I)–NHC. Pathways for the decomposition of Cu(I)–NHC and Ag–NHC were proposed.
- Li, Dazhi,Ollevier, Thierry
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supporting information
(2019/11/29)
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- Incorporation of coinage metal-NHC complexes into heptaphosphide clusters
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Cu(i) and Au(i) ions, capped with an N-heterocyclic carbene (NHC), react with (TMS)3P7 (TMS = trimethyl-silyl) to afford an η4-coordinated anion [NHCDippCu-P7(TMS)]- and a neutral trinuclear complex (NHCDippAu)3P7. Protecting the P7 cage with the TMS groups is instrumental in controlling the course of these reactions. This journal is
- Dragulescu-Andrasi, Alina,Jo, Minyoung,Li, Jingbai,Rogachev, Andrey Yu,Shatruk, Michael
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p. 12955 - 12959
(2020/10/13)
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- Synthesis method of gamma-aryl substituted ketone compound
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The invention relates to a synthetic method of an organic compound, in particular to a method for synthesizing a gamma-aryl substituted ketone compound by using a tertiary cyclobutanol derivative andaryl halide as reaction substrates under the catalytic action of nickel. According to the method, a substituted cyclobutanol compound shown as a formula I and a brominated compound shown as a formulaII are used as raw materials to obtain the gamma-aryl substituted ketone compound shown as a formula III. The nickel acetate tetrahydrate is rich in reserves and low in price, the reaction cost is reduced, and the method can be used for selectively synthesizing the remote gamma-aryl substituted ketone compound.
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Paragraph 0034-0035
(2020/12/31)
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- New expanded-ring NHC platinum(0) complexes: Synthesis, structure and highly efficient diboration of terminal alkenes
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The synthesis and structural characterization of a series of novel platinum(0) complexes were reported. A number of (NHC)Pt(dvtms) (dvtms = 1,3-divinyl-1,1,3,3-tetramethyldisiloxane) complexes were investigated in catalytic addition of B2Pin2 to terminal alkenes. The novel expanded ring N-heterocyclic carbene complex (7-Dipp)Pt(dvtms) showed highest performance, turnover numbers up to 3800 were achieved. The scope of the reaction was illustrated by 20 examples with a variety of alkyl, alkoxy, halogen, ester, ketone and acetal substituents.
- Rzhevskiy, Sergey A.,Topchiy, Maxim A.,Lyssenko, Konstantin A.,Philippova, Anna N.,Belaya, Maria A.,Ageshina, Alexandra A.,Bermeshev, Maxim V.,Nechaev, Mikhail S.,Asachenko, Andrey F.
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supporting information
(2020/02/18)
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- Robust Buchwald-Hartwig amination enabled by ball-milling
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An operationally simple mechanochemical method for the Pd catalysed Buchwald-Hartwig amination of arylhalides with secondary amines has been developed using a Pd PEPPSI catalyst system. The system is demonstrated on 30 substrates and applied in the context of a target synthesis. Furthermore, the performance of the reaction under aerobic conditions has been probed under traditional solution and mechanochemical conditions, the observations are discussed herein.
- Cao, Qun,Nicholson, William I.,Jones, Andrew C.,Browne, Duncan L.
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supporting information
p. 1722 - 1726
(2019/02/20)
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- NHC-Pd(II)-azole complexes catalyzed Suzuki–Miyaura cross-coupling of sterically hindered aryl chlorides with arylboronic acids
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In order to synthesize hindered biaryls efficiently, a series of NHC-Pd(II)-azole complexes bearing sterically hindered ligands were synthesized and characterized. The steric environment effect as well as the electronic effect of the azole ligands has been assessed. All these complexes were applied in the Suzuki–Miyaura cross-coupling reaction of sterically hindered aryl chlorides with low catalysts loadings (0.1 mol %) under mild conditions in air and good to excellent isolated yields of sterically hindered biaryls were obtained.
- Han, Fangwai,Li, Yanji,Liu, Guiyan,Lu, Qingwen,Ni, Chang,Zeng, Yongfei,Zhang, Rong,Zhang, Xue,Zhang, Yingying,Zhao, Yuxuan
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- Markovnikov-Selective Hydroboration of Olefins Catalyzed by a Copper N-Heterocyclic Carbene Complex
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The efficient and atom-economical hydroboration of alkenes and alkynes using an N-heterocyclic carbene (NHC) copper hydroxide catalyst has been developed. An equimolar combination of substrate and HBpin allows for the selective Markovnikov hydroboration of alkenes and alkynes. A variety of functional groups were tolerated in good to excellent yield. This system features a facile reaction setup, atom economy, high selectivity, and an easily synthesized copper-NHC catalyst.
- Dibenedetto, Tarah A.,Parsons, Astrid M.,Jones, William D.
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p. 3322 - 3326
(2019/09/30)
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- Synthesis of Imidazolidinone, Imidazolone, and Benzimidazolone Derivatives through Oxidation Using Copper and Air
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A new synthetic method of urea derivatives using copper and air was developed. These mild conditions provided moderate to very good yields for 15 examples (53-93%), while low yields were obtained with sterically hindered substrates (3 examples). The reaction was found to go through an in situ generated copper-N-heterocyclic carbene, which was then oxidized into cyclic urea derivatives possessing alkyl, benzyl, aryl, hydroxy, Boc-protected, and tertiary amine groups.
- Li, Dazhi,Ollevier, Thierry
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supporting information
p. 3572 - 3575
(2019/05/24)
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- Direct intramolecular carbon(sp2)-nitrogen(sp2) reductive elimination from gold(iii)
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The reactivity of bidentate AuIII-Cl species, [(C^N)AuCl2], with a bisphosphine or carbon donor ligands results in reductive elimination. Combined experimental and computational investigations lead to the first evidence of a direct intramolecular C(sp2)-N(sp2) bond formation from a monomeric [(C^N)AuCl2] gold(iii) complex. We show that bidentate ligated Au(iii) systems bypass transmetallation to form C(sp2)-N(sp2) species and NHC-Au-Cl. Mechanistic investigations of the reported transformation reveal a ligand-induced reductive elimination via a key AuIII intermediate. Kinetic studies of the reaction support a second-order rate process.
- Kim, Jong Hyun,Mertens, R. Tyler,Agarwal, Amal,Parkin, Sean,Berger, Gilles,Awuah, Samuel G.
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p. 6273 - 6282
(2019/05/17)
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- An imido ligand significantly enhances the effective energy barrier of dysprosium(iii) single-molecule magnets
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We report herein an imido ligand 1,3-bis(2,6-diisopropylphenyl) imidazolin-2-imine (ImDippNH) that can form a very short Dy-N bond (2.12 ?) with the dysprosium(iii) ion, which leads to a much larger effective energy barrier for magnetisation reversal (803 K) compared to the analogous alkoxide ligand (53 K). Moreover, we predict that a linear two-coordinate [Dy(ImDippN)2]+ complex may have an effective energy barrier larger than 4000 K.
- Liu, Bing-Cheng,Ge, Ning,Zhai, Yuan-Qi,Zhang, Tao,Ding, You-Song,Zheng, Yan-Zhen
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p. 9355 - 9358
(2019/08/08)
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- Mechanochemical Activation of Zinc and Application to Negishi Cross-Coupling
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A form independent activation of zinc, concomitant generation of organozinc species and engagement in a Negishi cross-coupling reaction via mechanochemical methods is reported. The reported method exhibits a broad substrate scope for both C(sp3)–C(sp2) and C(sp2)–C(sp2) couplings and is tolerant to many important functional groups. The method may offer broad reaching opportunities for the in situ generation organometallic compounds from base metals and their concomitant engagement in synthetic reactions via mechanochemical methods.
- Cao, Qun,Howard, Joseph L.,Wheatley, Emilie,Browne, Duncan L.
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supporting information
p. 11339 - 11343
(2018/08/28)
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- Two Stereoinduction Events in One C?H Activation Step: A Route towards Terphenyl Ligands with Two Atropisomeric Axes
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Herein we disclose the synthesis of original chiral scaffolds—ortho-orientated terphenyls presenting two atropisomeric Ar–Ar axes. These unusual structures were built up by using the C?H activation approach, and remarkably, both chiral axes were controlled with excellent stereoselectivity in a single transformation. During the reaction, not only does atroposelective functionalization of a biaryl precursor occur to establish one stereogenic axis, but an unprecedented atropo-stereoselective C?H arylation also takes place to generate the second stereogenic element. These enantiomerically pure ortho-terphenyls show an original tridimensional structure and thus constitute a unique foundation for building up a library of enantiomerically pure bidentate ligands, such as the new ligands S/N-Biax and diphosphine BiaxPhos.
- Dherbassy, Quentin,Djukic, Jean-Pierre,Wencel-Delord, Joanna,Colobert, Fran?oise
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supporting information
p. 4668 - 4672
(2018/03/21)
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- Selective Oxidative Carbonylation of Aniline to Diphenylurea with Ionic Liquids
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A catalytic system for the selective oxidative carbonylation of aniline to diphenylurea based on Pd complexes in combination with imidazolium ionic liquids is presented. Both oxidants, Pd complexes, and ionic liquids affect the activity of the reaction, and the choice of oxidant determines the selectivity of the reaction. Together they allow the reaction to proceed under comparatively mild conditions without a loss of activity. Examination of the reaction by use of in situ NMR spectroscopy allowed us to observe an intermediate suggested only previously, which supported the proposed mechanism.
- Zahrtmann, Nanette,Claver, Carmen,Godard, Cyril,Riisager, Anders,Garcia-Suarez, Eduardo J.
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p. 2450 - 2457
(2018/04/11)
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- A more sustainable and efficient access to IMes·HCl and IPr·HCl by ball-milling
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Herein is described a mechanochemical one-pot two-step procedure giving access to various NHC (N-heterocyclic carbene) precursors. This original approach enabled the production of the widely used IPr·HCl, IMes·HCl, Io-Tol·HCl and ICy·HCl in much better yields than conventional solvent-based procedures, while the environmental impact was drastically reduced.
- Beillard, Audrey,Bantreil, Xavier,Métro, Thomas-Xavier,Martinez, Jean,Lamaty, Frédéric
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supporting information
p. 964 - 968
(2018/03/13)
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- A New Mode of Operation of Pd-NHC Systems Studied in a Catalytic Mizoroki-Heck Reaction
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Metal complexes bearing N-heterocyclic carbene (NHC) ligands are typically considered the system of choice for homogeneous catalysis with well-defined molecular active species due to their stable metal-ligand framework. A detailed study involving 19 different Pd-NHC complexes with imidazolium, benzimidazolium, and triazolium ligands has been carried out in the present work and revealed a new mode of operation of metal-NHC systems. The catalytic activity of the studied Pd-NHC systems is predominantly determined by the cleavage of the metal-NHC bond, while the catalyst performance is strongly affected by the stabilization of in situ formed metal clusters. In the present study, the formation of Pd nanoparticles was observed from a broad range of metal complexes with NHC ligands under standard Mizoroki-Heck reaction conditions. A mechanistic analysis revealed two different pathways to connect Pd-NHC complexes to "cocktail"-type catalysis: (i) reductive elimination from a Pd(II) intermediate and the release of NHC-containing byproducts and (ii) dissociation of NHC ligands from Pd intermediates. Metal-NHC systems are ubiquitously applied in modern organic synthesis and catalysis, while the new mode of operation revealed in the present study guides catalyst design and opens a variety of novel opportunities. As shown by experimental studies and theoretical calculations, metal clusters and nanoparticles can be readily formed from M-NHC complexes after formation of new M-C or M-H bonds followed by C-NHC or H-NHC coupling. Thus, a combination of a classical molecular mode of operation and a novel cocktail-type mode of operation, described in the present study, may be anticipated as an intrinsic feature of M-NHC catalytic systems.
- Astakhov, Alexander V.,Khazipov, Oleg V.,Chernenko, Andrey Yu.,Pasyukov, Dmitry V.,Kashin, Alexey S.,Gordeev, Evgeniy G.,Khrustalev, Victor N.,Chernyshev, Victor M.,Ananikov, Valentine P.
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p. 1981 - 1992
(2017/06/14)
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- Recyclable Single-Component Rare-Earth Metal Catalysts for Cycloaddition of CO2 and Epoxides at Atmospheric Pressure
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Ionic rare-earth metal complexes 1-4 bearing an imidazolium cation were synthesized, which, as single-component catalysts, showed good activity in catalyzing cyclic carbonate synthesis from epoxides and CO2. In the presence of 0.2 mol % catalyst, monosubstituted epoxides bearing different functional groups were converted into cyclic carbonates in 60-97% yields under atmospheric pressure. In addition, bulky/internal epoxides with low reactivity yielded cyclic carbonates in 40-95% yields. More importantly, the readily available samarium complex 2 was reused for six successive cycles without any significant loss in its catalytic activity. This is the first recyclable rare-earth metal-based catalyst in cyclic carbonate synthesis.
- Zhao, Zhiwen,Qin, Jie,Zhang, Chen,Wang, Yaorong,Yuan, Dan,Yao, Yingming
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p. 4568 - 4575
(2017/04/26)
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- Rare-earth imidazole salt compound as well as preparation method and application of rare-earth imidozole salt compound as catalyst
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The invention discloses a rare-earth imidazole salt compound as well as a preparation method and application of the rare-earth imidazole salt compound as a catalyst. The general formula of the rare-earth imidazole salt compound is [RECl4(THF)2](HIPr), wherein RE is rear-earth metal selected from one of La, Sm, Yb and Y, HIPr is a 1,3-di(2-6-diisopropylphenyl) imidazole cation; and the rare-earth imidazole salt compound disclosed by the invention is simple to synthesize, clear in structure and high in yield. The invention provides the preparation method of the compound and an application method of the compound serving as a catalyst to catalyze reaction between an aziridine derivative and carbon dioxide, and according to the application method, the condition is mild, the activity is high, the selectivity is good, and the substrate applicable range is wide.
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- Pd-catalyzed hydroborylation of alkynes: A ligand controlled regioselectivity switch for the synthesis of α- Or β-vinylboronates
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A ligand controlled selective hydroborylation of alkynes to α- or β-vinylboronates has been developed using a Pd catalyst. The high α-selectivity displayed by this reaction can be switched to furnish β-vinylboronates by altering the ligand from a trialkylphosphine to N-heterocyclic carbene. A variety of terminal alkynes are shown to furnish the corresponding α- or β-vinylboronates in good to excellent selectivity and yield. The mechanistic studies suggest that the solvent is the proton source and bromobenzene functions as an important additive in driving this reaction forward.
- Ojha, Devi Prasan,Prabhu, Kandikere Ramaiah
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supporting information
p. 432 - 435
(2016/02/18)
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- A new nitrogen heterocyclic carbene containing diiron complex as bio-inspired catalyst for proton reduction and benzene hydroxylation
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A new diiron complex (μ-dmedt)[Fe2(CO)5IPr] (2, dmedt = 2,3-butanedithiol, IPr = 1,3-bis(2,6-diisopropylphenyl) imidazol-2-ylidene) was synthesized as analogue of the active site of [Fe-Fe]-H2ases. The sterically bulky nitrogen heterocyclic carbene ligand of IPr coordinated to the iron center was introduced via CO/L substitution reaction in mild conditions. The reactivity of electrocatalytic reduction of proton and catalytic hydroxylation of benzene were explored for the developed diiron complex. Complex 2 undergoes two irreversible reduction events at ca. -2.17 V and ?2.50 V and acts as an efficient electrocatalyst for proton reduction to hydrogen with both HOAc and H2O as proton source. The catalytic hydroxylation of benzene by complex 2 achieved phenol yield of 32.4% with almost 100% selectivity. The enhanced catalytic activity compared to the all carbonyl precursor and related derivatives was attributed to the good electron donating ability of introduced IPr ligand.
- Wang, Yanhong,Yang, Yiwen,Zhang, Tianyong,Zhang, Xia,Jiang, Shuang,Zhang, Guanghui,Li, Bin
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- Unraveling the synthesis of homoleptic [Ag(N, N -diaryl-NHC)2]Y (Y = BF4, PF6) complexes by ball-milling
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A user-friendly and general mechanochemical method was developed to access rarely described NHC (N-heterocyclic carbene) silver(i) complexes featuring N,N-diarylimidazol(idin)ene ligands and non-coordinating tetrafluoroborate or hexafluorophosphate counter anions. Comparison with syntheses in solution clearly demonstrated the superiority of the ball-milling conditions.
- Beillard, Audrey,Bantreil, Xavier,Métro, Thomas-Xavier,Martinez, Jean,Lamaty, Frédéric
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supporting information
p. 17859 - 17866
(2016/11/18)
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- Convergent Activation Concept for CO2 Fixation in Carbonates
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Concepts to facilitate the conversion of epoxides with carbon dioxide to the corresponding cyclic carbonates commonly focus on the activation of the epoxide. Herein we report a catalytic system which allows the simultaneous activation of carbon dioxide and the epoxide. This convergent activation concept is realized by combining a suitable carbene as catalyst for the carbon dioxide activation with a second catalytic system based on potassium iodide for epoxide activation. Initial experiments showed synergistic effects and thus proving the feasibility of this activation concept. Moreover a standard protocol was developed and the substrate scope under these conditions has been studied. Under mild and solvent-free conditions 14 epoxides could be converted. The respective cyclic carbonates were obtained in good to excellent yields with selectivities ≥ 99 % after simple filtration.
- Desens, Willi,Werner, Thomas
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p. 622 - 630
(2016/02/27)
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- PhenoFluorMix: Practical chemoselective deoxyfluorination of phenols
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A practical deoxyfluorination with novel deoxyfluorinating reagent PhenoFluorMix, a mixture of N,N'-1,3-bis(2,6-diisopropylphenyl)chloroimidazolium chloride and CsF, is presented. PhenoFluorMix overcomes the challenges associated with hydrolysis of PhenoFluor. PhenoFluorMix does not hydrolyze, is readily available on decagram scale, and is storable in air. In this paper, we demonstrate the practicality of the reagent and exhibit the deoxyfluorination of a variety of phenols and heterocycles.
- Fujimoto, Teppei,Ritter, Tobias
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supporting information
p. 544 - 547
(2015/03/05)
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- Phosphine-free, efficient double carbonylation of aryl iodides with amines catalyzed by water-insoluble and water-soluble N-heterocyclic carbene-amine palladium complexes
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The water-insoluble and water-soluble N-heterocyclic carbene (NHC)-amine palladium complexes, Ipr-Pd(deba)Cl and SO3-Ipr-Pd(deba)Cl, were synthesized. Both catalysts exhibit excellent activity in the phosphine-free double carbonylation of aryl iodides with amines to produce α-keto amides. Moreover, as the water-soluble catalyst exhibits significant compatibility in the aqueous phase with the activities of different Pd-NHC complexes, we conclude that the intramolecular amine ligand strongly affects the selectivity of the products in double carbonylation reaction and serves as an alternative of phosphine ligands.
- Wang, Yan,Yang, Xiaolong,Zhang, Chunyan,Yu, Jianqiang,Liu, Jianhua,Xia, Chungu
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supporting information
p. 2539 - 2546
(2014/09/29)
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- PhenoFluor: Practical synthesis, new formulation, and deoxyfluorination of heteroaromatics
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We report a practical synthesis method of the reagent PhenoFluor on decagram scale, provide a new formulation of PhenoFluor as a toluene solution, which should decrease challenges associated with the moisture sensitivity of the reagent, and expand the substrate scope of deoxyfluorination with PhenoFluor to heteroaromatics.
- Fujimoto, Teppei,Becker, Fabian,Ritter, Tobias
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p. 1041 - 1044
(2014/11/07)
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- Synthesis, structural and spectral properties of Au complexes: Luminescence properties and their non-covalent DNA binding studies
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Gold complexes of 1,3- bis-pyridylimidazolium chloride (L1), 1,3-bis-[2,6-diisopropylphenyl]imidazolium chloride (L2) and 1,3-bis-[benzyl]benzimidazolium chloride (L3) were synthesized and characterized by analytical methods. For the complexes, electronic spectral results show that there is a marked difference in the band feature observed in the spectra, ascribed to the greater relativistic effect of gold. In fluorescence studies, the complexes develop emission bands in the visible region (400-600 nm) after excitation at around 350 nm. Au complex-DNA binding was studied, and it was observed that genomic DNA isolated from the U373-GB cell line was fragmented and in some cases degraded by the Au complexes. Furthermore, the intensity of the DNA band increased when concentration of the metal complex was augmented. This study shows that the DNA cleavage is mediated by the Au complex. Copyright
- Huerta-Aguilar, Carlos,Talamantes Gomez, Jose M.,Thangarasu, Pandiyan,Camacho-Arroyo, Ignacio,Gonzalez-Arenas, Aliesha,Narayanan, Jayanthi,Srivastava, Rajendra
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p. 578 - 587
(2013/10/21)
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- A direct and practical approach for the synthesis of N-heterocyclic carbene coinage metal complexes
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A novel direct and practical synthetic route leading to N-heterocyclic carbene coinage metal complexes has been developed by using air stable, commercial available Au(III) salt [MAuCl4·2H2O], CuCln (n=1,2) or AgCl, and imidazolium salts as starting materials. The reaction proceeded without sacrificing carbene transfer agent (Ag 2O) or using highly sensitive free NHC.
- Zhu, Shifa,Liang, Renxiao,Jiang, Huanfeng
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supporting information; experimental part
p. 7949 - 7955
(2012/09/22)
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- Intermolecular mono-and dihydroamination of activated alkenes using a recoverable gold catalyst
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A combination of gold chloride organometallic complex and a silver salt was used to catalyze intermolecular hydroamination of activated alkenes, i.e aza-Michael reactions. The gold-catalyzed reactions of activated alkenes with nitrogen substrates were investigated and found to afford various mono-and dihydroamination products, the latter being rare and original. After flash chromatography, gold NHC catalyst could be recovered as a gold hydroxide NHC complex. When combined with a silver salt, the gold complex lead again to an active hydroamination catalyst.
- Medina, Florian,Michon, Christophe,Agbossou-Niedercorn, Francine
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p. 6218 - 6227
(2013/01/15)
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- PKas of the conjugate acids of N-heterocyclic carbenes in water
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pKa values of 19.8-28.2 are reported for the conjugate acids of a large series of NHCs in water. The effects of ring size, N-substituent and C(4)-C(5) saturation on pKa are discussed.
- Higgins, Eleanor M.,Sherwood, Jennifer A.,Lindsay, Anita G.,Armstrong, James,Massey, Richard S.,Alder, Roger W.,O'Donoghue, Annmarie C.
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supporting information; experimental part
p. 1559 - 1561
(2011/03/22)
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- Deoxyfluorination of phenols
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An operationally simple ipso fluorination of phenols with a new deoxyfluorination reagent is presented.
- Tang, Pingping,Wang, Weike,Ritter, Tobias
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supporting information; experimental part
p. 11482 - 11484
(2011/10/02)
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- Nickel-catalyzed amination of aryl Pivalates by the cleavage of aryl C-O bonds
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(Figure Presented) Catalytic animation: The title reaction demonstrates the use of aryl carboxylates as suitable electrophilic coupling substrates in catalytic amination reactions. Nheterocyclic carbene ligands and NaOtBupromote the amination of aryl pivalates through the cleavage of normally unreactive aryl carbon-oxygen bonds (see scheme; cod = cyclooctadiene).
- Shimasaki, Toshiaki,Tobisu, Mamoru,Chatani, Naoto
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supporting information; experimental part
p. 2929 - 2932
(2010/06/15)
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- Probing the efficiency of N-heterocyclic carbene promoted O- to C-carboxyl transfer of oxazolyl carbonates
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(Chemical Equation Presented) Screening of a range of azolium salts, bases and solvents for reactivity indicates that triazolinylidenes, generated in situ with KHMDS in THF, promote the Steglich rearrangement of oxazolyl carbonates with high catalytic efficiency (typical reaction time 5 min at 1.5 mol % NHC). This protocol shows wide substrate applicability, even allowing the efficient generation of vicinal quaternary centers. An improved experimental procedure is also described that allows a simplified one-pot reaction protocol to be employed with similarly high catalytic efficiency.
- Thomson, Jennifer E.,Campbell, Craig D.,Concellon, Carmen,Duguet, Nicolas,Rix, Kathryn,Slawin, Alexandra M. Z.,Smith, Andrew D.
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p. 2784 - 2791
(2008/09/20)
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- Complexes of borane and N-heterocyclic carbenes: A new class of radical hydrogen atom donor
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Calculations suggest that complexes of borane with N-heterocyclic carbenes (NHC) have B-H bond dissocation energies more then 20 kcal/mol less than free borane, diborane, borane-THF, and related complexes. Values are in the range of popular radical hydrogen atom donors like tin hydrides (70-80 kcal/mol). The resulting prediction that NHC borane complexes could be used as radical hydrogen atom donors was verified by radical deoxygenations of xanthates by using either AIBN or triethylborane as initiator. Copyright
- Ueng, Shau-Hua,Brahmi, Malika Makhlouf,Derat, Etienne,Fensterbank, Louis,Lacote, Emmanuel,Malacria, Max,Curran, Dennis P.
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supporting information; scheme or table
p. 10082 - 10083
(2009/02/04)
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- SYNTHESIS OF 1,3 DISUBSTITUTED IMIDAZOLIUM SALTS
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Imidazolium salts are the immediate precursors to N-heterocyclic carbenes (NHC) yet a simple, general synthetic route to a wide variety of imidazolium salts is not yet available. Such a straightforward route is described for two specific members of this family of ligand precursor: l,3-Bis(2,4,6-trimethylphenyl)imidazolium chloride (IMes-HCl) and l,3-Bis(2,6-diispropylphenyl)imidazolium chloride (IPrHCl). The procedure appears general and similar protocols can be used to isolate various imidazolium salts.
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Page/Page column 4; 6-7; 8-9
(2008/06/13)
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- Synthesis of chromium N-heterocyclic carbene complexes using chromium Fischer carbenes as a source of chromium carbonyls
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Chromium Fischer carbene complexes, [Cr{{double bond, long}OMe(R)}(CO)5] have been utilized as a source of chromium carbonyls in the synthesis of chromium NHC complexes. Using the synthetic method, chromium complexes of various NHC ligands were isolated in reasonable yields. Moreover, the method can be employed for the synthesis of molybdenum and tungsten NHC compounds.
- Kim, Seongjin,Choi, Soo Young,Lee, Young Tak,Park, Kang Hyun,Sitzmann, Helmut,Chung, Young Keun
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p. 5390 - 5394
(2008/03/12)
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- Synthesis of 1,3 distributed imidazolium salts
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Imidazolium salts are the immediate precursors to N-heterocyclic carbenes (NHC) yet a simple, general synthetic route to a wide variety of imidazolium salts is not yet available. Such a straightforward route is described for two specific members of this family of ligand precursor: 1,3-Bis(2,4,6-trimethylphenyl)imidazolium chloride (IMes.HCl) and 1,3-Bis(2,6-diispropylphenyl)imidazolium chloride (IPr.HCl). The procedure appears general and similar protocols can be used to isolate various imidazolium salts.
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Page/Page column 4-7
(2008/06/13)
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- A sterically demanding nucleophilic carbene: 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene. Thermochemistry and catalytic application in olefin metathesis
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The sterically demanding nucleophilic carbene ligand 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr, 4) has been synthesized. The reaction of [Cp*RuCl]4 (5; Cp* = η5-C5Me5) with this ligand affords a coordinatively unsaturated Cp*Ru(IPr)Cl (6) complex. Solution calorimetric results in this system provide information concerning the electron donor properties of the carbene ligand. Steric parameters associated with this ligand are determined from the X-ray crystal structure study. The carbene ligand reacts with RuCl2(=C(H)Ph)(PCy3)2 (1) to yield a mixed carbene-phosphine ruthenium complex RuCl2(=C(H)Ph)(IPr)(PCy3) (9). A single-crystal X-ray diffraction study has been performed on 9. The thermal stability of 9 has been studied at 60°C and its catalytic activity has been evaluated for the ring closing metathesis of diethyldiallylmalonate.
- Jafarpour, Laleh,Stevens, Edwin D.,Nolan, Steven P.
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