- Radical reactions catalysed by homobimetallic ruthenium(II) complexes bearing Schiff base ligands: Atom transfer radical addition and controlled polymerisation
-
The homobimetallic ruthenium Schiff base complexes Ia-f mediated the atom transfer radical addition (ATRA) of carbon tetrachloride across olefins in excellent yields which markedly depended on the catalyst and the substrate used. The best catalytic system Ic is able to compete with the highest performing ruthenium catalysts reported so far for ATRA reactions. In addition these systems are also capable of performing atom transfer radical polymerisation (ATRP) reactions with styrene in high yields and with good control over molecular weight and molecular weight distribution.
- De Clercq, Bob,Verpoort, Francis
-
-
Read Online
- Atom transfer radical additions with the cationic half-sandwich complex [Cp*Ru(PPh3)2(CH3CN)]OTf
-
The cationic ruthenium half-sandwich complex [Cp*Ru(PPh 3)2(CH3CN)][OTf] (2) (Cp* = η5-C5Me5, OTf = SO3CF 3) was synthesized by reduction of [Cp*RuCl2] 2 with zinc in the presence of NaOTf and subsequent reaction with PPh3. When NaOTf was omitted, the corresponding tetrachlorozincate salts were obtained. Complex 2, as well as the salts [Cp*Ru(CH 3CN)3]2[ZnCl4] (3) and [Cp*Ru(PPh3)2-(CH3CN)] 2[ZnCl4] (4), were characterized by single-crystal X-ray analysis. Complex 2 proved to be a potent catalyst for the atom transfer radical addition of CCl4 and CHCl3 to terminal olefins, displaying a performance superior to that of the previously described neutral catalyst [Cp*RuCl(PPh3)2]. For the addition of CHCl3 to styrene, a total turnover number of 890 was achieved. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Quebatte, Laurent,Scopelliti, Rosario,Severin, Kay
-
-
Read Online
- Microwave-enhanced ruthenium-catalysed atom transfer radical additions
-
The first monomode microwave-assisted atom transfer radical additions (ATRA) of carbon tetrachloride to various olefins were successfully performed, affording the adducts with almost quantitative yields in less than 10 min at 160 °C.
- Borguet, Yannick,Richel, Aurore,Delfosse, Sébastien,Leclerc, Alain,Delaude, Lionel,Demonceau, Albert
-
-
Read Online
- Microwave activation of homogeneous and heterogeneous catalytic reactions
-
Microwave healing was applied in homogeneous and in heterogeneous reactions and the results were compared from the point of view of activation of chemical reactions. Reactions including the addition of halo compounds to alkenes catalyzed by copper and ruthenium complexes in different solvents and NaY zeolite catalyzed alkylation of secondary amine in the absence of solvent were studied as model reactions to compare possibilities of microwave activation of reactants and catalysts. Rate enhancement of over one order of magnitude in homogeneous reactions was caused mainly by thermal dielectric heating effect which resulted from the effective coupling of microwaves to polar solvents. Activation of reactants and catalysts was very low if any. In heterogeneously catalyzed alkylation reactions highly efficient activation of zeolite catalyst was recorded. The results indicated that the best reaction conditions were in experiments when both activation of catalyst and performance of reaction were carried out under microwave conditions. Rate enhancement was most probably caused by "hot spots" or by "selective heating" of active sites. In both homogeneous and heterogeneous reactions non-thermal activation (specific effect) was excluded.
- Hajek, Milan
-
-
Read Online
- New pincer-type diphosphinito (POCOP) complexes of NiII and NiIII
-
This communication reports the synthesis and characterization of the new, pincer-type, square-planar, 16-electron compounds {2,6-(OPPri 2)2C6H3}NiIIBr, 1, and {(Pri2POCH2)2CH}NiIIBr, 2, and the square-pyramidal, 17-electron complex {(Pri 2POCH2)2CH}NiIIIBr2, 3. The Royal Society of Chemistry.
- Pandarus, Valerica,Zargarian, Davit
-
-
Read Online
- The modulating possibilities of dicarbollide clusters: Optimizing the Kharasch catalysts
-
exo-Cluster dicarbollides substitution has allowed tuning of the E° (Ru(II)/Ru(III)) potential to obtain the best-performing Kharasch catalyst. We postulate that this is possible through the to-and-fro electron movement between the boron cluster and the sulfonium moieties. Copyright
- Tutusaus, Oscar,Vinas, Clara,Nunez, Rosario,Teixidor, Francesc,Demonceau, Albert,Delfosse, Sebastien,Noels, Alfred F.,Mata, Ignasi,Molins, Elies
-
-
Read Online
- 31Cl NQR SPECTRA OF COMPOUNDS IN Cl3CCH2CXRR' SERIES
-
In molecules in the series Cl3CCH2CClRR', the substituents R and R' virtually do not affect the chlorine atoms of the Cl3C group, while the NQR frequency of the chlorine atom of the CClRR' group correlates satisfactorily with the ?* constants of these substituents.The regularities observed in the mutual influence of the atoms in the molecules of the studied series indicate that the previously assumed structure of some products of radical telomerization of Cl3CH with H2C=CHCl is erroneous.
- Feshin, V. P.,Dolgushin, G. V.,Voronkov, M. G.,Gaek, M.,Yanoushek, Z.
-
-
Read Online
- Synthesis, Characterization, and Reactivity of PCN Pincer Nickel Complexes
-
New diamagnetic nickel(II) complexes based on an unsymmetrical (1-(3-((ditert-butylphosphino)methyl)phenyl)-N,N-dimethyl-methanamine) (PCN) pincer ligand were synthesized and characterized by 1H, 31P{1H}, and 13C{1H} NMR spectroscopy. Their molecular structures were confirmed by X-ray diffraction. Oxidation to high-valent paramagnetic Ni(III) dihalide complexes was achieved through straightforward reaction of the corresponding diamagnetic halide complexes with anhydrous CuX2 (X = Cl, Br). In agreement with this, the complexes are active in Kharasch addition of CCl4 to olefins. The reaction of the hydroxo complex (8) and the amido complex (11) with CO2 produced the hydrogen carbonate and carbamate complexes, respectively. The hydrogen carbonate complex was converted to the dinuclear nickel carbonate complex (10). The methyl (13), phenyl (14), and p-tolylacetylide (15) complexes are also described in the current study providing the first example of the hydrocarbyl nickel complexes based on an unsymmetric aromatic pincer ligand. Furthermore, the reactivity of the methyl complex toward different electrophiles has been investigated, showing that C-C bond formation is possible with aryl halides, whereas the reaction with CO2 is sluggish.
- Mousa, Abdelrazek H.,Bendix, Jesper,Wendt, Ola F.
-
-
Read Online
- Kharasch addition catalysed by half-sandwich ruthenium complexes. Enhanced activity of ruthenacarboranes
-
Ruthenium complexes of the type [RuH(η5-CB)(PPh 3)2] {CB is a monoanionic charge-compensated carborane ligand such as [9-SR2-7,8-C2B9H 10]- and [9-SR2-7-CH3-7,8-C 2B9H9]-} efficiently catalyse the Kharasch addition of CCl4 across olefins and, with maximum total turnover numbers of 9000 and initial turnover frequencies of 1900 h -1 at 40°C, highly surpass their Ru-Cp# analogues in these reactions.
- Tutusaus, Oscar,Delfosse, Sébastien,Demonceau, Albert,Noels, Alfred F.,Vi?as, Clara,Teixidor, Francesc
-
-
Read Online
- Mechanistic and computational studies of the atom transfer radical addition of CCl4 to styrene catalyzed by copper homoscorpionate complexes
-
Experimental as well as theoretical studies have been carried out with the aim of elucidating the mechanism of the atom transfer radical addition (ATRA) of styrene and carbon tetrachloride wwith a TpxCu(NCMe) complex as the catalyst precursor (Tpx = hydrotrispyrazolyl-borate ligand). The studies shown herein demonstrate the effect of different variables in the kinetic behavior. A mechanistic proposal consistent with theoretical and experimental data is presented.
- Munoz-Molina, Jose Maria,Sameera,Alvarez, Eleuterio,Maseras, Feliu,Belderrain, Tomas R.,Perez, Pedro J.
-
-
Read Online
- New, highly efficient catalyst precursors for Kharasch additions - [RuCl(Cp*)(PPh3)2] and [RuCl(Ind)(PPh3)2]
-
[RuCl(Cp*)(PPh3)2] and [RuCl(Ind)(PPh3)2] are excellent catalyst precursors for promoting the Kharasch addition of CCl4 and CHCl3 across olefins under mild reaction conditions (at temperatures as low as 40 °C with CCl4). The effect of the substituents on the cyclopentadienyl ring has been investigated. In terms of efficiency and activity, [RuCl(Cp*)(PPh3)2] and [RuCl(Ind)(PPh3)2] surpass the best ruthenium systems reported so far. A two-step mechanism, in which the extrusion of a phosphane ligand occurs prior to the activation of the halogenated compound by the unsaturated ruthenium center, is suggested.
- Simal, Fran?ois,Wlodarczak, Lise,Demonceau, Albert,Noels, Alfred F.
-
-
Read Online
- Highly efficient Kharasch addition catalysed by RuCl(Cp*)(PPh3)2
-
Air-stable and readily available RuCl(Cp*)(PPh3)2 is so far the best ruthenium-based catalyst precursor for promoting the addition of CCl4 and CHCl3 across olefins at a temperature as low as 40°C. (C) 2000 Elsevier Science Ltd.
- Simal,Wlodarczak,Demonceau,Noels
-
-
Read Online
- Bimolecular concerted elimination as an elementary stage in free-radical reactions. Reaction of organocobaloximes with bromotrichloromethane
-
In free-radical reaction of cis-β-phenylvinylcobaloxime with bromotrichloromethane the primary product, phenylacetylene, arises as a result of elimination, and further it adds the bromotrichloromethane. Similarly proceeds the reaction between β-phenylethylcobaloxime with bromotrichloromethane. The values of absolute rate constants and their relation to the nature of the axial ligand completely agree with the assumption that in the reactions in question similarly to the E2 mechanism of nucleophilic elimination the elimination occurs as one-stage bimolecular process with the simultaneous rupture of C-Co and C-H bonds.
- Dneprovskii,Kasatochkin
-
-
Read Online
- Immobilized metal ion-containing ionic liquids: Preparation, structure and catalytic performance in Kharasch addition reaction
-
Immobilized metal ion-containing ionic liquid catalysts were prepared by the reaction between silyl-functionalized imidazolium ionic molecules and surface silanol groups of silica, followed by addition of MnCl2, FeCl2, CoCl2, NiCl2, CuCl2, or PdCl2; only the immobilized copper catalyst, which has a sandwiched CuCl42- moiety, was very active for the Kharasch reaction between styrene and CCl4. The Royal Society of Chemistry 2005.
- Sasaki, Takehiko,Zhong, Chongmin,Tada, Mizuki,Iwasawa, Yasuhiro
-
-
Read Online
- Cycloruthenated complexes as homogeneous catalysts for atom-transfer radical additions
-
Various cycloruthenated complexes were used as homogeneous catalysts for the atom-transfer radical addition of polyhalogenated compounds to several olefinic substrates. Yields obtained through conventional or microwave heating could reach high values (up to 98% with CBrCl3 and 88% with CCl4).
- Parkhomenko, Ksenia,Barloy, Laurent,Sortais, Jean-Baptiste,Djukic, Jean-Pierre,Pfeffer, Michel
-
-
Read Online
- Microwave-assisted catalytic addition of halocompounds to alkenes
-
Microwave irradiation has been applied to homogeneous catalytic addition reactions of tetrachloromethane and ethyl trichloroacetate with styrene. The 3 to 21-fold increase of the reaction rate was observed compared to classical heating.
- Adamek,Hajek
-
-
Read Online
- Radical reactions catalysed by ruthenium(II) complexes with anionic carborane phosphine ligands: Kharasch addition to olefins and controlled polymerisation
-
Ruthenium-carborane complexes 1-3 mediated the Kharasch addition of carbon tetrachloride across olefins with high yields which markedly depended on the catalyst and the substrate used. In addition, the atom transfer radical polymerisation of methyl methacrylate could be carried out in a highly controlled way. (C) 2000 Elsevier Science Ltd.
- Simal, Fran?ois,Sebille, Sophie,Demonceau, Albert,Noels, Alfred F.,Nu?ez, Rosario,Abad, Mar,Teixidor, Francesc,Vi?as, Clara
-
-
Read Online
- Atom-transfer radical reactions under mild conditions with [{RuCl 2(1,3,5-C6H3iPr3)}2] and PCy3 as the catalyst precursors
-
Simply mixing the complex [{RuCl2(1,3,5-C6H 3iPr3)}2] (1) with PCy3 is sufficient to generate a catalyst suitable for highly efficient atom-transfer radical addition and polymerization reactions at exceptionally low temperatures (see scheme). The steric congestion at the metal caused by the bulky ligands is thought to be essential for the reactivity of the catalyst.
- Quebatte, Laurent,Haas, Michel,Euro Solari, Rosario Scopelliti,Nguyen, Quoc T.,Severin, Kay
-
-
Read Online
- Cu-Catalyzed photoredox chlorosulfonation of alkenes and alkynes
-
Visible-light photoredox chlorosulfonation of alkenes and alkynes is achieved using a Cu photocatalyst. The reactions occur under mild conditions, have broad scope, and have high functional group tolerance.
- Alkan-Zambada, Murat,Hu, Xile
-
p. 4525 - 4533
(2019/04/25)
-
- Efficient Pincer-Ruthenium Catalysts for Kharasch Addition of Carbon Tetrachloride to Styrene
-
A series of NNN pincer-ruthenium complexes (R2NNN)RuCl2(PPh3) (R=Cyclohexyl (Cy), t-butyl (tBu), i-propyl (iPr) and phenyl (Ph)) have been synthesized and characterized. These pincer-ruthenium complexes have been used to catalyse the Kharasch addition or atom transfer radical addition (ATRA) of carbon tetrachloride to styrene. Among the pincer-ruthenium catalysts screened for the Kharasch addition, the catalytic activity followed the order (Cy2NNN)RuCl2(PPh3)>(iPr2NNN)RuCl2(PPh3)?(Ph2NNN)RuCl2(PPh3). The oxidation of Ru(II) is easier with (Cy2NNN)RuCl2(PPh3) and (iPr2NNN)RuCl2(PPh3) in comparison with (Formula presented.) RuCl2(PPh3) as indicated by cyclic voltammetry studies. The catalyst precursor (R2NNN)RuCl2(PPh3) itself is the resting state of the reaction. The rate determining step involves the generation of the five-coordinate 16-electron ruthenium(II) species (R2NNN)RuCl2. Owing to weaker binding of triphenyl phosphine to ruthenium, the generation of catalytically active 16-electron species (Cy2NNN)RuCl2 and (iPr2NNN)RuCl2 are more favourable. The complex (Cy2NNN)RuCl2(PPh3) demonstrates very high productivity (5670 turnovers after 48 h at 140 °C) in the absence of any co-catalyst radical initiator. To the best of our knowledge, our turnovers (ca. 5670) are much higher than that reported hitherto. Quantum mechanical calculations demonstrate that the path involving the activation of carbon tetrachloride by (Cy2NNN)RuCl2 is more favoured than the path where carbon tetrachloride is activated by (Cy2NNN)RuCl2(η2-styrene). Density functional theory (DFT) and kinetic studies are in accord with the widely accepted mechanism involving the single electron transfer (SET) from ruthenium(II) to chloride radical with concomitant generation of a benzyl radical which is trapped by the resulting ruthenium(III) species. (Figure presented.).
- Das, Kanu,Dutta, Moumita,Das, Babulal,Srivastava, Hemant Kumar,Kumar, Akshai
-
supporting information
p. 2965 - 2980
(2019/04/30)
-
- Atom Transfer Radical Addition Catalyzed by Ruthenium-Arene Complexes Bearing a Hybrid Phosphine-Diene Ligand
-
The synthesis and characterization of a series of arene ruthenium complexes bearing either (3,5-cycloheptadienyl)diphenylphosphine or (cycloheptyl)diphenylphosphine are reported. Upon irradiation or heating, all these complexes lose their arene ligand but then exhibit a different behavior depending on the nature of the phosphine ligand. (Cycloheptadienyl)phosphine complexes 1 and 3 give a cationic dinuclear Ru complex 5 for which the two Ru atoms are bridged by three chlorido ligands and flanked by two tridendate (cycloheptadienyl)phosphines. (Cycloheptyl)diphenylphosphine complexes 2 and 4 undergo arene exchange when toluene is used as solvent or degrade in dichloromethane. ATRA catalytic trials conducted in parallel with these complexes using CCl4 and styrene as standard substrates, highlighted the deep impact of the dienyl moiety on the results. Under smooth conditions (UV irradiation or moderate heating), only (cycloheptyl)phosphine derivatives give Karasch adduct in satisfactory yields. Their performance was considerably improved by combining irradiation and heating. At higher temperature, cationic dinuclear complex 5 was revealed as active and robust, giving turnover numbers as high as 9700 when tetradecene and CCl4 were used as substrates.
- Chotard, Florian,Malacea-Kabbara, Raluca,Balan, Cédric,Bodio, Ewen,Picquet, Michel,Richard, Philippe,Ponce-Vargas, Miguel,Fleurat-Lessard, Paul,Le Gendre, Pierre
-
p. 812 - 820
(2018/03/21)
-
- Rhodium-Catalyzed Enantioselective Radical Addition of CX4 Reagents to Olefins
-
We describe the synthetically useful enantioselective addition of Br?CX3 (X=Cl or Br) to terminal olefins to introduce a trihalomethyl group and generate optically active secondary bromides. Computational and experimental evidence supports an asymmetric atom-transfer radical addition (ATRA) mechanism in which the stereodetermining step involves outer-sphere bromine abstraction from a [(bisphosphine)RhIIBrCl] complex by a benzylic radical intermediate. This mechanism appears unprecedented in asymmetric catalysis.
- Chen, Bo,Fang, Cheng,Liu, Peng,Ready, Joseph M.
-
p. 8780 - 8784
(2017/07/17)
-
- Structural and Electronic Noninnocence of α-Diimine Ligands on Niobium for Reductive C-Cl Bond Activation and Catalytic Radical Addition Reactions
-
A d0 niobium(V) complex, NbCl3(α-diimine) (1a), supported by a dianionic redox-active N,N′-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1,3-butadiene (α-diimine) ligand (ene-diamido ligand) served as a catalyst for radical addition reactions of CCl4 to α-olefins and cyclic alkenes, selectively affording 1:1 radical addition products in a regioselective manner. During the catalytic reaction, the α-diimine ligand smoothly released and stored an electron to control the oxidation state of the niobium center by changing between an η4-(σ2,π) coordination mode with a folded MN2C2 metallacycle and a κ2-(N,N′) coordination mode with a planar MN2C2 metallacycle. Kinetic studies of the catalytic reaction elucidated the reaction order in the catalytic cycle: the radical addition reaction rate obeyed first-order kinetics that were dependent on the concentrations of the catalyst, styrene, and CCl4, while a saturation effect was observed at a high CCl4 concentration. In the presence of excess amounts of styrene, styrene coordinated in an η2-olefinic manner to the niobium center to decrease the reaction rate. No observation of oligomers or polymers of styrene and high stereoselectivity for the radical addition reaction of CCl4 to cyclopentene suggested that the C-C bond formation proceeded inside the coordination sphere of niobium, which was in good accordance with the negative entropy value of the radical addition reaction. Furthermore, reaction of 1a with (bromomethyl)cyclopropane confirmed that both the C-Br bond activation and formation proceeded on the α-diimine-coordinated niobium center during transformation of the cyclopropylmethyl radical to a homoallyl radical. With regard to the reaction mechanism, we detected and isolated NbCl4(α-diimine) (6a) as a transient one-electron oxidized species of 1a during reductive cleavage of the C-X bonds; in addition, the monoanionic α-diimine ligand of 6a adopted a monoanionic canonical form with selective one-electron oxidation of the dianionic ene-diamido form of the ligand in 1a.
- Nishiyama, Haruka,Ikeda, Hideaki,Saito, Teruhiko,Kriegel, Benjamin,Tsurugi, Hayato,Arnold, John,Mashima, Kazushi
-
supporting information
p. 6494 - 6505
(2017/09/12)
-
- Synthesis, characterization, X-ray crystallography analysis, and catalytic activity of bis(2-pyridylmethyl)amine copper complexes containing coupled pendent olefinic arms in atom transfer radical addition (ATRA) reactions
-
The synthesis, characterization, and catalytic activity of bis(2-pyridylmethyl)amine (BPMA) copper complexes incorporating olefinic pendent arms are reported. Four copper(I) and four copper(II) complexes were synthesized employing four different counterions [chloride (Cl-), perchlorate (ClO4-), trifluoromethanesulfonate (CF3SO3-), and tetraphenylborate (BPh4-)]. The counterions used ranged from coordinating (Cl-) to non-coordinating (BPh4-), producing different coordination modes in respective complexes. Solid state results obtained for the copper(I) complex incorporating the non-coordinating (BPh4-) counterion displayed an associative bond between the metal center and the C=C group in the olefinic arm of a neighboring complex. This interaction led to augmentation of the C=C bond due to back-bonding from the metal center. Five solid state structures were obtained for the copper(II) complexes with two also displaying intermolecular associative bonding between olefinic pendent arms and the metal center. X-ray crystallography studies showed that the olefinic arm motifs incorporated were hemilabile. Solution studies indicated that the copper complexes had some inherent reducing power and could be potential candidates for use as catalysts in atom transfer radical processes. However, only moderate conversions and yields were obtained in atom transfer radical addition (ATRA) reaction studies performed utilizing the copper complexes due to the presence of a competing reaction.
- Bussey, Katherine A.,Cavalier, Annie R.,Mraz, Margaret E.,Oshin, Kayode D.,Sarjeant, Amy,Pintauer, Tomislav
-
supporting information
p. 256 - 267
(2016/07/06)
-
- Assessment of catalysis by arene-ruthenium complexes containing phosphane or NHC groups bearing pendant conjugated diene systems
-
Two p-cymene-ruthenium complexes 1 and 2 were isolated in high yields by treating the [RuCl2(p-cymene)]2 dimer with new hybrid phosphane- or NHC-linked diene ligands. Both complexes were fully characterized by NMR spectroscopy, and the molecular structure of the ruthenium-p-cymene complex 1, containing the phosphane-diene ligand system, was determined by X-ray diffraction analysis. The catalytic activities of both compounds were probed in atom-transfer radical addition (ATRA) and polymerization (ATRP), in the cyclopropanation of olefins, in the ring-opening metathesis polymerization (ROMP) of norbornene, and in the synthesis of enol esters from hex-1-yne and 4-acetoxybenzoic acid.
- Baraut, Johann,Massard, Alexandre,Chotard, Florian,Bodio, Ewen,Picquet, Michel,Richard, Philippe,Borguet, Yannick,Nicks, Fran?ois,Demonceau, Albert,Le Gendre, Pierre
-
supporting information
p. 2671 - 2682
(2015/06/22)
-
- A half-sandwich 1,2-azaborolyl ruthenium complex: Synthesis, characterization, and evaluation of its catalytic activities
-
A half-sandwich 1,2-azaborolyl (Ab) ruthenium complex, (Ab-CCPh) RuCl(PPh3)2 (1), has been synthesized by treating RuCl2(PPh3)3 with lithium 1,2-azaborolide L-1, or by treating either RuCl2(PPh3)3 or RuHCl(PPh3)3 directly with 1,2-azaborole LH-1. It is evaluated as a suitable precatalyst in [2 + 2] cycloadditions of norbornene derivatives with DMAD and in atom transfer radical additions of halogenated compounds with olefins. The Royal Society of Chemistry.
- Liu, Zicheng,Xu, Junjie,Ruan, Wenqing,Fu, Chen,Zhang, Hui-Jun,Wen, Ting-Bin
-
supporting information
p. 11976 - 11980
(2013/09/02)
-
- Visible light-mediated atom transfer radical addition via oxidative and reductive quenching of photocatalysts
-
Herein, the development of visible light-mediated atom transfer radical addition (ATRA) of haloalkanes onto alkenes and alkynes using the reductive and oxidative quenching of [Ir{dF(CF3)ppy}2(dtbbpy)]PF 6 and [Ru(bpy)3]Cl2 is presented. Initial investigations indicated that the oxidative quenching of photocatalysts could effectively be utilized for ATRA, and since that report, the protocol has been expanded by broadening the scope of the reaction in terms of the photocatalysts, substrates, and solvents. In addition, further modifications of the reaction conditions allowed for the efficient ATRA of perfluoroalkyl iodides onto alkenes and alkynes utilizing the reductive quenching cycle of [Ru(bpy) 3]Cl2 with sodium ascorbate as the sacrificial electron donor. These results signify the complementary nature of the oxidative and reductive quenching pathways of photocatalysts and the ability to predictably direct reaction outcome through modification of the reaction conditions.
- Wallentin, Carl-Johan,Nguyen, John D.,Finkbeiner, Peter,Stephenson, Corey R. J.
-
supporting information; experimental part
p. 8875 - 8884
(2012/07/02)
-
- [(PhBP3)Cu(PPh3)] as a surrogate of TpxCuL in homogeneous catalysis (PhBP3 = PhB(CH2PPh 2)3; Tpx = hydrotrispyrazolylborate)
-
The novel complexes [(PhBP3)Cu(L)] (PhBP3 = PhB(CH2PPh2)3, L = PPh3, 1; L = tetrahydrofuran, 2) have been synthesized and spectroscopically and, in the case of 1, structurally characterized. Both complexes undergo dissociation of the PPh3 or THF ligand in solution to deliver the (PhBP3)Cu unit, similar in geometry to and isoelectronic with TpxCu (Tp x = trispyrazolylborate ligand). A complete study of the catalytic properties of 1 has shown that it can be considered as a surrogate of Tp xCu. The study includes (a) olefin cyclopropanation, cyclopropenation, aziridination, halocarbon addition, and radical polymerization, (b) X-H (X = O, N) functionalization by carbene insertion, and (c) furan conversion into dihydropyridines. Since the observed activity is quite comparable to that already described for TpxCu complexes, this new catalytic system could become an alternative to the latter.
- Angeles Fuentes,Alvarez, Eleuterio,Caballero, Ana,Perez, Pedro J.
-
experimental part
p. 959 - 965
(2012/04/10)
-
- Transesterification catalyzed by ionic liquids on superhydrophobic mesoporous polymers: Heterogeneous catalysts that are faster than homogeneous catalysts
-
Homogeneous catalysts usually show higher catalytic activities than heterogeneous catalysts because of their high dispersion of catalytically active sites. We demonstrate here that heterogeneous catalysts of ionic liquids functionalized on superhydrophobic mesoporous polymers exhibit much higher activities in transesterification to form biodiesel than homogeneous catalysts of the ionic liquids themselves. This phenomenon is strongly related to the unique features of high enrichment and good miscibility of the superhydrophobic mesoporous polymers for the reactants. These features should allow the design and development of a wide variety of catalysts for the conversion of organic compounds.
- Liu, Fujian,Sun, Qi,Meng, Xiangju,Xiao, Feng-Shou,Wang, Liang,Zhu, Longfeng
-
p. 16948 - 16950,3
(2020/09/02)
-
- Modulating the steric, electronic, and catalytic properties of Cp* ruthenium half-sandwich complexes with β-diketiminato ligands
-
Five different types of β-diketiminate ligands, bearing electron-donating to strongly electron-withdrawing substituents, were synthesized and used in the synthesis of Cp* ruthenium complexes (Cp* = η5-C5Me5). One series consists of complexes with a covalent RuIII-Cl bond, and the other series features a reduced RuII center, where the chloride is abstracted by treatment of the corresponding RuIII compounds with Zn or Mg. All compounds were characterized by single-crystal X-ray diffraction, UV-visible spectroscopy, and cyclic voltammetry. In the case of RuII complexes, solution NMR techniques provided key information regarding the electronic and structural differences induced by the different β-diketiminate ligands employed. Capitalizing on the facile reduction-oxidation cycle of the Cp* ruthenium β-diketiminato complexes, catalytic atom transfer radical addition (ATRA) and cyclization (ATRC) reactions were performed on relevant substrates. The turnover rates are strongly dependent on the type of β-diketiminate used, where ligands with electron-withdrawing substituents, i.e., trifluoromethyl groups, provided complexes that efficiently catalyze the addition of CCl4 or toluenesulfonyl chloride to styrene. In contrast, complexes with electron-donating substituents on the β-diketiminate promoted efficient ATR cyclization of N-allyl-N-phenyltrichloroacetamide and 2,2,2-trichloroethyl ether. Thus, the overall product conversion and yield are dependent on matching the ligand substitution pattern of the catalyst to the type of substrate.
- Phillips, Andrew D.,Thommes, Katrin,Scopelliti, Rosario,Gandolfi, Claudio,Albrecht, Martin,Severin, Kay,Schreiber, Dominique F.,Dyson, Paul J.
-
experimental part
p. 6119 - 6132
(2012/01/04)
-
- Photoinitiated ambient temperature copper-catalyzed atom transfer radical addition (ATRA) and cyclization (ATRC) reactions in the presence of free-radical diazo initiator (AIBN)
-
The use of UV light in copper-catalyzed atom transfer radical addition (ATRA) and cyclization (ATRC) reactions of various (poly)halogenated compounds to highly active alkenes in the presence of AIBN is reported. Radicals generated from photodecomposition of AIBN efficiently regenerated the copper(i) complex at ambient temperature enabling ATRA of CCl4 and CBr4 with catalyst loadings as low as 0.05 mol-%. The desired monoadduct was obtained in lower yields in the ATRA of less active halogenated compounds, which was mostly due to incomplete alkene conversions. Ambient temperature ATRA of CCl 4 to various 1,6-dienes followed by sequential ATRC was also performed in the presence of UV light using [CuII(TPMA)Cl][Cl] complex and AIBN. High yields of the 5-exo-trig cyclic product were obtained for all dienes with preferential formation of the cis isomer. The Royal Society of Chemistry 2011.
- Balili, Marielle Nicole C.,Pintauer, Tomislav
-
experimental part
p. 3060 - 3066
(2011/05/13)
-
- Dinuclear molybdenum cluster-catalyzed radical addition and polymerization reactions by tuning the redox potential of a quadruple bonded Mo2 core
-
We developed dinuclear molybdenum cluster-catalyzed radical addition and polymerization reactions by tuning the redox potential of the Mo2 core. A 2,4,6-triisopropylbenzoate-supported Mo2 complex acts as a catalyst for radical addition reactions of polyhaloalkanes to 1-alkenes and cyclopentene, while amidinate- and guanidinate-supported Mo2 clusters are effective catalysts for the radical polymerization reaction of methyl methacrylate.
- Tsurugi, Hayato,Yamada, Kohei,Majumdar, Moumita,Sugino, Yoshitaka,Hayakawa, Akio,Mashima, Kazushi
-
supporting information; experimental part
p. 9358 - 9361
(2011/11/05)
-
- Kharasch addition of tetrachloromethane to alkenes catalyzed by metal acetylacetonates
-
Various transition metal acetylacetonates have proven to be efficient catalytic systems for the Kharasch addition of tetrachloromethane to alkenes under mild conditions, providing 1:1 adducts in up to 87% yield, based on internal standard. The nature of metal, solvent, temperature, olefin/CCl 4 ratio and the presence of nucleophilic co-catalysts were tested to evaluate the scope and limitation of the reaction.
- Boualy, Brahim,Harrad, Mohamed Anouar,El Firdoussi, Larbi,Ait Ali, Mustapha,El Houssame, Soufiane,Karim, Abdellah
-
experimental part
p. 1295 - 1297
(2012/01/13)
-
- An efficient, selective, and reducing agent-free copper catalyst for the atom-transfer radical addition of halo compounds to activated olefins
-
Efficient and selective ATRA reactions of CCl4, CBr4, TsCl (Ts = tosyl), or Cl3CCO2Et with activated olefins (styrene, methyl methacrylate, n-butyl methacrylate, ferf-butyl methacrylate) using the TptBuCu(NCMe) complex as a catalyst have been achieved In the absence of any reductant and with low catalyst loadings.
- Munoz-Molina, Jose Maria,Belderrain, Tomas R.,Perez, Pedro J.
-
experimental part
p. 642 - 645
(2010/03/25)
-
- Copper-catalyzed atom transfer radical addition (ATRA) and cyclization (ATRC) reactions in the presence of environmentally benign ascorbic acid as a reducing agent
-
In recent years, copper-catalyzed atom transfer radical addition (ATRA) has emerged as a viable organic procedure for the formation of carbon-carbon bonds starting from alkyl halides and alkenes. Studies have primarily focused on the use of free-radical initiators to regenerate the copper(i) complex or activator in situ. Although these initiators led to a significant decrease in the amount of metal catalyst, they were much less effective for highly active alkenes that readily undergo free-radical polymerization. In this study, the non-radical reducing agent ascorbic acid (commonly known as Vitamin C) was effectively employed resulting in TONs as high as 15200 in the homogenous ATRA of polyhalogenated compounds to α-olefins, and enabling selective monoadduct formation for highly active alkenes such as acrylonitrile (TONs as high as 11800). As low as 7-20 mol% of ascorbic acid relative to substrate was sufficient for all ATRA and ATRC reactions examined. Further, product isolations for all selected syntheses were quite facile and nearly quantitative, requiring only simple liquid-liquid extraction techniques. Reactions in the presence of ascorbic acid were also examined kinetically via1H NMR and UV/Vis spectroscopy. A half order rate dependence on reducing agent concentration was observed, but the first order kinetic plots became nonlinear as the concentration of ascorbic acid was increased. Finally, the use of ascorbic acid circumvented otherwise necessary purging techniques, successfully furthering the utility of these reactions in organic synthesis.
- Taylor, Matthew J. W.,Eckenhoff, William T.,Pintauer, Tomislav
-
experimental part
p. 11475 - 11482
(2011/02/17)
-
- Metal phthalocyanine-catalyzed addition of polychlorine-containing organic compounds to C=C bonds
-
Organopolychlorine compounds (CCl4, CCl3CO 2Et, CCl3CHO) add at the double bond of various olefins under the catalysis of the metal phthalocyanine complexes. A possibility of quantitative catalyst recovery was shown.
- Ivanov,Maksimov,Tomilova,Zefirov
-
p. 2393 - 2396
(2014/05/06)
-
- Highly efficient ambient-temperature copper-catalyzed atom-transfer radical addition (ATRA) in the presence of free-radical initiator (V-70) as a reducing agent
-
Highly efficient, ambient-temperature, copper-catalyzed Atom Transfer Radical Addition (ATRA) of polyhalogenated compounds to alkenes in the presence of free radical initiator 2,2' -azobis (4-methoxy-2,4-dimethyl valeronitrile)(V-70)as a reducing agent was reported. The discrepancies between the alkene conversion and percent yield were mostly due to competing free-radical polymerization. ATRA of polyhalogenated compounds to monomers that are highly active in free-radical polymerization was not successful at 60 ° C when AIBN was used as radical initiator. The V-70 was proved to be very effective reducing agent, enabling selective formation of the monoadduct with α -olefins and highly active monomers such as methyl acrylate, methyl methacrylate, and vinyl acetate. The methodology for catalyst regeneration in copper-mediated ATRA in the presence of V-70 as a reducing agent also worked very well in the addition of CCl4 and CBr4 to highly active vinyl acetate.
- Pintauer, Tomislav,Eckenhoff, William T.,Ricardo, Carolynne,Balili, Marielle N. C.,Biernesser, Ashley B.,Noonan, Sean J.,Taylor, Matthew J. W.
-
supporting information; experimental part
p. 38 - 41
(2009/06/17)
-
- Highly efficient heterogeneous aqueous Kharasch reaction with an amphiphilic resin-supported ruthenium catalyst
-
An amphiphilic polystyrene-polyethylene glycol (PS-PEG) resin-supported ruthenium complex was designed and prepared. The polymeric Ru complex was found to promote the transition metal-catalyzed atom transfer radical addition of halogenated compounds to olefins, the Kharasch reaction, in water under heterogeneous as well as AIBN-free conditions with a high level of atom economy to meet green chemical requirements.
- Oea, Yohei,Uozumia, Yasuhiro
-
experimental part
p. 1771 - 1775
(2009/07/09)
-
- Immobilized ruthenium complexes bearing N,O-bidentate ligands
-
Immobilization of a family of arene and benzylidene N,O-bidentate ruthenium complexes by covalently anchoring the homogeneous complexes on MCM-41 is described. Successful applications of these immobilized catalytic systems in enol-ester synthesis, Kharasch addition, ring-closing metathesis (RCM), ring-opening metathesis polymerization (ROMP) and atom transfer radical polymerization (ATRP) are illustrated. Important advantages of these heterogeneous catalyst systems in comparison with their homogeneous counterparts are also highlighted.
- Drǎgu?an, Valerian,Verpoort, Francis
-
p. 905 - 915
(2008/09/20)
-
- Exploring the substrate scope of the Ru(II)-catalyzed kharasch reaction
-
The Kharasch reaction, or atom-transfer addition of polyhalogenated alkanes to alkenes is known to be catalyzed by a number of Ru(II) complexes. The easily prepared [RuCl2(PPh3)3] was used to investigate the reaction scope. A number of halogenated alkanes were added to a range of alkenes with good to excellent regioselectivities.
- Mume, Eskender,Munslow, Ian J.,Kaellstroem, Klas,Andersson, Pher G.
-
p. 1005 - 1013
(2008/09/21)
-
- Atom-transfer radical addition (ATRA) and cyclization (ATRC) reactions catalyzed by a mixture of [RuCl2Cp*(PPh3)] and magnesium
-
A new catalytic procedure for atom-transfer radical addition (ATRA) and cyclization (ATRC) reactions is described. The combination of the ruthenium(III) complex [RuCl2-Cp*(PPh3)] (Cp*: pentamethylcyclopentadienyl) with magnesium allows these reactions to be performed under mild conditions with high efficiency. In most cases, the catalyst concentrations required are significantly lower than those used in previously reported procedures. It is suggested that magnesium acts as a reducing agent that generates and regenerates the catalytically active ruthenium(II) species. The precatalyst [RuCl2Cp*(PPh 3)] has been analyzed by X-ray crystallography.
- Thommes, Katrin,Icli, Burcak,Scopelliti, Rosario,Severin, Kay
-
p. 6899 - 6907
(2008/03/13)
-
- Electrochemistry as a correlation tool with the catalytic activities in [RuCl2(p-cymene)(PAr3)]-catalysed Kharasch additions
-
[RuCl2(p-cymene)] complexes containing triarylphosphine ligands with various substituents at the para position were used to catalyse the atom transfer radical addition of carbon tetrachloride to various olefins, and their catalytic activities were nicely correlated with their electrochemical parameters.
- Richel, Aurore,Demonceau, Albert,Noels, Alfred F.
-
p. 2077 - 2081
(2007/10/03)
-
- Combinatorial catalysis with bimetallic complexes: Robust and efficient catalysts for atom-transfer radical additions
-
A radical alternative? Two highly efficient catalysts for atom-transfer radical additions were discovered in a parallel screening of bimetallic complexes. Both catalysts contain a rhodium-centered fragment (blue), which is connected through three chloro bridges to a ruthenium-centered fragment (red).
- Quebatte, Laurent,Scopelliti, Rosario,Severin, Kay
-
p. 1520 - 1524
(2007/10/03)
-
- Ruthenium catalysts bearing N-heterocyclic carbene ligands in atom transfer radical reactions
-
The catalytic activity of ruthenium-p-cymene complexes bearing N-heterocyclic carbene ligands in atom transfer radical addition (ATRA) or polymerisation (ATRP) strongly depends on the substituents of the carbene ligand, thereby providing a nice illustration of the importance of organometallic engineering and ligand fine tuning in homogeneous catalysis.
- Richel, Aurore,Delfosse, Sébastien,Cremasco, Cédric,Delaude, Lionel,Demonceau, Albert,Noels, Alfred F.
-
p. 6011 - 6015
(2007/10/03)
-
- From atom transfer radical addition to atom transfer radical polymerisation of vinyl monomers mediated by ruthenium indenylidene complexes
-
Ruthenium indenylidene complexes provide a new class of versatile catalysts for promoting the Atom Transfer Radical Addition (ATRA) of carbon tetrachloride and chloroform toward a whole array of olefins such as acrylates, methacrylates, styrene and 1-octene. The reaction was successfully extended to an Atom Transfer Radical Polymerisation (ATRP) process by changing the monomer/halide ratio. The polymerisation reaction can be accelerated by adding n-Bu2NH to the reaction mixture. However this leads to an uncontrolled polymerisation. Further improvements to the catalytic activity can be made by transforming the Ru complexes in the cationic 14-electron species or exchanging the indenylidene fragment with an ethoxycarbene. A very high activity is reached when these complexes are exposed to methyl methacrylate in aqueous media while maintaining excellent control over the formed polymers.
- Opstal, Tom,Verpoort, Francis
-
p. 257 - 262
(2007/10/03)
-
- Atom transfer radical addition and enol-ester synthesis catalyzed by Ru-vinylidene complexes
-
Ru-vinylidene complexes, Cl2Ru{=C=C(H)tBut}(PCy3)(L) (L=PCy3 or N-heterocyclic carbenes) reveal themselves as a versatile catalyst for the atom transfer radical addition (ATRA) of polyhalogenated alkanes to olefins, such as methylmethacrylate, styrene and 1-octene. Furthermore, these systems are excellent catalysts for the nucleophilic addition of carboxylic acids to terminal alkynes and yielded exclusively alk-1-en-2-yl esters. These complexes can also be transformed to their cationic counterparts by treating the neutral complexes with AgBF4 and their catalytic potential in ATRA and vinylation reaction are investigated.
- Opstal, Tom,Verpoort, Francis
-
p. 9259 - 9263
(2007/10/03)
-
- Alkynylhalocarbenes 4. Generation of (alk-1-ynyl)halocarbenes from 3-substituted 1,1,1,3-tetrahalopropanes under the action of bases
-
When treated with KOH under phase-transfer catalysis or with Bu tOK, 3-substituted (alkyl or phenyl) 1,1,3-tribromo-1-fluoropropanes 1a-c exclusively generate previously unknown (alk-1-ynyl)fluorocarbenes 5a-c, which react with olefins to give 1-(alk-1-ynyl)-1-fluorocyclopropanes 6a-h in 12-69% yields. Under analogous conditions, 3-alkyl- and 3-aryl-3-bromo-1,1,1-trichloropropanes 2a-c selectively afford (alk-1-ynyl)chlorocarbenes 7a-c, which are trapped by olefins to form the corresponding 1-(alk-1-ynyl)-1-chlorocyclopropanes 8a-k in 35-70% yields. (Phenylethynyl)chlorocarbene 7a is also selectively generated from 1,1,1,3-tetrachloro-3-phenylpropane (3a) upon its treatment with Bu tOK. With an excess of 2,3-dimethylbut-2-ene or 2-methylpropene, carbene 7a yields 1-chloro-1-(phenylethynyl)cyclopropanes 8a or 8c, respectively. In contrast, 1,1,1,3-tetrachloroheptane 3b and 3-alkyl- and 3-phenyl-1,1,1,3-tetrabromopropanes 4a,c,f react with bases in the presence of olefins to give, along with the corresponding 1-(alk-1-ynyl) -1-halocyclopropanes 8a,c,d and 11a-f, vinylidenecyclopropanes 12a,c-g, which suggests the generation, under these conditions, both (alk-1-ynyl)halocarbenes 7b and 9a-c and vinylidenecarbenes 10 and 11a-c. The composition and structures of intermediate products in the reactions of tetrahalides 1b, 2a, 2b, 3a, and 3b with ButOK were determined and the mechanisms for carbene generation in these reactions were proposed.
- Shavrin,Gvozdev,Nefedov
-
p. 1237 - 1253
(2007/10/03)
-
- A new heterogeneous hybrid ruthenium catalyst being an eco-friendly option for the production of polymers and organic intermediates
-
We succeeded in synthesising and characterising a new heterogeneous hybrid ruthenium catalyst that exhibits excellent stability, reusability and leaching characteristics. The host-guest interaction is studied by XRD, XRF, ICP/MS, BET, FT-Raman and solid state NMR analysis. Moreover, we tested this catalytic system in ring-closing metathesis (RCM), ring-opening metathesis polymerization (ROMP), Kharasch addition, atom transfer radical polymerization (ATRP) and vinylation reactions. The results obtained from these tests show that for ROMP, RCM, Kharasch addition and vinylation reactions the heterogeneous catalyst possesses important advantages in comparison with its homogeneous analogue.
- De Clercq, Bob,Lefebvre, Frederic,Verpoort, Francis
-
p. 1201 - 1208
(2007/10/03)
-
- Ring-closing metathesis, Kharasch addition and enol ester synthesis catalysed by a novel class of ruthenium(II) complexes
-
Ruthenium Schiff base complexes I-III mediated the Kharasch addition of carbon tetrachloride across olefins with high yields which markedly depended on the catalyst and the substrate used. In addition, ring-closing metathesis of some representative diolefins was carried out. The best catalytic system III is able to form tri- and tetrasubstituted double bond products. Finally, dependent of the catalytic system and the reaction conditions used, these systems can catalyse the stereoselective formation of enol esters or enynes in excellent yields.
- De Clercq, Bob,Verpoort, Francis
-
p. 8959 - 8963
(2007/10/03)
-
- Kharasch addition and controlled atom transfer radical polymerisation (ATRP) of vinyl monomers catalysed by Grubbs' ruthenium-carbene complexes
-
The Grubbs' ruthenium-carbene complexes, RuCl2(=CHPh)(PR3)2, mediate the Kharasch addition of CCl4 across olefins, and the controlled atom transfer radical polymerisation of vinyl monomers with high yields and selectivities which markedly depend on the phosphine ligands of the complex (R=phenyl, cyclopentyl, and cyclohexyl).
- Simal, Francois,Demonceau, Albert,Noels, Alfred F.
-
p. 5689 - 5693
(2007/10/03)
-
- Rate enhancement of organic reactions by microwaves at atmospheric pressure
-
Several different reactions have been studied to determine whether they occur more rapidly than conventionally heated reactions at atmospheric pressure. Small rate enhancements have been observed for some reactions carried out under microwave reflux in a modified domestic microwave oven. The Knoevenagel reaction of acetophenone with ethyl cyanoacetate was shown to have a rate enhancement of 2.5 times. However this reaction showed no rate increase over conventional heating, at the same temperature, in a variable-frequency microwave oven. It is therefore probable that the small rate enhancements observed in these experiments, using microwave heating, were due to hot spots or superheating of the solvent rather than to nonthermal effects.
- Gedye,Wei
-
p. 525 - 532
(2007/10/03)
-
- The Fe0 promoted addition of CCl4 and CCl3Br to olefins
-
The radical addition of CCl4 or CCl3Br to olefins is efficiently promoted by iron filings in N,N-dimethylformamide under mild conditions.
- Bellesia, Franco,Forti, Luca,Ghelfi, Franco,Pagnoni, Ugo M.
-
p. 961 - 971
(2007/10/03)
-