- The solid-phase catalytic oxydation of 2-hydroxy-3,5-di-tert-butylbenzyl alcohol
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The solid-phase catalytic oxidation in the 2-hydroxy-3,5-di-tert-butylbenzyl alcohol-MnO2-NaOH system to yield 2-hydroxy-3,5-di-tert-butylbenzaldehyde was carried out.Gaseous oxygen participates in the regeneration of the active form of the oxidant. - Key words: oxidation, benzyl alcohol, salicylic aldehyde, catalysis, synthesis, solid phase, liquid phase.
- Dokukina, M. A.,Vol'eva, V. B.,Belostotskaya, I. S.,Komissarova, N. L.,Karmilov, A. Yu.,et al.
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- Cobalt(II) phenoxy-imine complexes in radical polymerization of vinyl acetate: The interplay of catalytic chain transfer and controlled/living radical polymerization
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A series of cobalt(II) phenoxy-imine complexes (CoII(FI)2) have been synthesized to mediate the radical polymerization of vinyl acetate (VAc) and methyl acrylate (MA) to evaluate the influence of chelating atoms and configuration to the control of polymerization. The VAc polymerizations showed the properties of controlled/living radical polymerization (C/LRP) with complexes 1a and 3a, but the catalytic chain transfer (CCT) behaviors with complexes 2a, 1b, 2b, and 3b. The control of VAc polymerization mediated by complex 1a could be improved by decreasing the reaction temperature to approach the molecular weights that not only linearly increased with conversions but also matched the theoretical values and relatively narrow molecular weight distributions. The catalytic chain transfer polymerizations (CCTP) mediated by complexes 2a, 1b, 2b, and 3b were characterized by Mayo plots and the polymer chain end double bonds were observed by 1H NMR spectra. The tendency toward C/LRP or CCTP in VAc polymerization mediated by CoII(FI)2 could be determined by the ligand structure. Cobalt complex coordinated by the ligand with more steric hindered and less electron-donating substituents favored the controlled/living radical polymerization. In contrast, the efficiency of CCT process could be enhanced by less steric hindered, more electron-donating ligands. The controlled/living radical polymerization of MA, however, could not be achieved by the mediation of these cobalt(II) phenoxy-imine complexes. Associated with the results of polymerization mediated by other cobalt complexes, this study implied that the configuration and spin state of cobalt complexes were more critical than the chelating atoms to the control behavior of radical polymerization.
- Chen, Yi-Hao,Chen, Shih-Ji,Li, Jia-Qi,Wu, Zhenqiang,Lee, Gene-Hsiang,Liu, Yi-Hung,Cheng, Wei-Ting,Yeh, Chen-Yu,Peng, Chi-How
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- Optical and electrochemical properties of hydrogen-bonded phenol-pyrrolidino[60]fullerenes
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We report the photophysical and electrochemical properties of phenol-pyrrolidino[60]fullerenes 1 and 2, in which the phenol hydroxyl group is ortho and para to the pyrrolidino group, respectively, as well as those of a phenyl-pyrrolidino[60]fullerene model compound, 3. For the ortho analog 1, the presence of an intramolecular hydrogen bond is supported by 1H NMR and FTIR characterization. The redox potential of the phenoxyl radical-phenol couple in this architecture is 240 mV lower than that observed in the associated para compound 2. Further, the C60 excited-state lifetime of the hydrogen-bonded compound 1 in benzonitrile is 260 ps, while the corresponding lifetime for 2 is identical to that of the model compound 3 at 1.34 ns. Addition of excess organic acid to a benzonitrile solution of 1 gives rise to a new species, 4, with an excited-state lifetime of 1.40 ns. In nonpolar aprotic solvents such as toluene, all three compounds have a C60 excited-state lifetime of a??1 ns. These results suggest that the presence of an intramolecular H-bond in 1 poises the potential of phenoxyl radical-phenol redox couple at a value that it is thermodynamically capable of reducing the photoexcited fullerene. This is not the case for the para analog 2 nor is it the case for the protonated species 4. This work illustrates that in addition to being used as light activated electron acceptors, pyrrolidino fullerenes are also capable of acting as built-in proton-accepting units that influence the potential of an attached donor when organized in an appropriate molecular design.
- Moore, Gary F.,Megiatto, Jackson D.,Hambourger, Michael,Gervaldo, Miguel,Kodis, Gerdenis,Moore, Thomas A.,Gust, Devens,Moore, Ana L.
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Read Online
- Synthesis of 6-tert-octyl and 6,8-ditert-butyl coumarins, two coumarins of biological interest
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In this study, the synthesis of new coumarins with aliphatic chains is discussed. The incorporation of the 6-tert-octyl and 6,8-ditert-butyl chains into a coumarin structure from alkylphenols, allows obtaining hydrophobic coumarins with good yields. These coumarins can be potential modulators of TRPV1 receptors. Synthesis and spectroscopic data of these new coumarins are analyzed.
- Arroyo, P.,Darouch, M.,Lisboa, E.,Miranda, A.,Zárraga, M.
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p. 5220 - 5222
(2021/07/12)
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- Phosphasalalen Rare-Earth Complexes for the Polymerization of rac-Lactide and rac-β-Butyrolactone
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A series of new phosphasalalen pro-ligands, analogues of salalen but with an iminophosphorane replacing the imine functionality, and their corresponding rare-earth alkoxide and siloxide complexes were synthesized. The multinuclear NMR spectra and X-ray diffraction analyses revealed that, for the tert-butoxide and ethoxide complexes, the resulting phosphasalalen rare-earth product was composed of a mononuclear alkoxide and a binuclear complex containing bridged alkoxo and hydroxo groups, while an analogous binuclear complex was isolated as the sole product for the siloxide complex. All the complexes could catalyze the heteroselective ring-opening polymerization (ROP) of rac-lactide (Pr up to 0.77) with high catalytic activities and a controlled polydispersity. Remarkably, the yttrium and lutetium phosphasalalen complexes could also efficiently catalyze the ROP of rac-β-butyrolactone to produce syndiotactic polymers (Pr up to 0.73) while their salalen analogues were inert, revealing the special effects of the iminophosphorane moiety. Detailed end-group analyses and kinetic investigations suggested that the alkoxo-hydroxo-bridged complexes maintained their binuclear structures in the polymerization.
- Liu, Hui,Shi, Xiaochao
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p. 705 - 717
(2021/02/05)
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- Enantioselective Hydroboration of Ketones Catalyzed by Rare-Earth-Metal Complexes Supported with Phenoxy-Functionalized TsDPEN Ligands
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Six novel chiral rare-earth-metal complexes bearing the phenoxy-functionalized TsDPEN ligand H3L1 (H3L1 = N-((1R,2R)-2-((3,5-di-Tert-butyl-2-hydroxybenzyl)amino)-1,2-diphenylethyl)-4-methylbenzenesulfonamide) were synthesized successfully and well characterized. The solid-state structures of four tetranuclear rare-earth-metal complexes [RE2L13]2 (RE = Nd (1), Sm (2), Eu (3), Gd (4)) and the dual-core yttrium complex Y2L13 (5) were determined by X-ray diffraction, respectively. The structure of lanthanum complex 6 was speculated by the 1H DOSY spectroscopy in THF-d8 together with DFT calculations. Complexes 1-5 were employed to catalyze the enantioselective hydroboration of ketones and α,β-unsaturated ketones using pinacolborane (HBpin) as a reductant, and complex 1 gave better outcomes in comparison to the others. The corresponding secondary alcohols were obtained in excellent yields and moderate ee values. The same results were also achieved using the combined catalyst system of the neodymium amide Nd[N(SiMe3)2]3 with the phenoxy-functionalized TsDPEN ligand H3L1 in a 1:1.5 molar ratio.
- Yu, Qishun,Lu, Chengrong,Zhao, Bei
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supporting information
p. 2529 - 2537
(2021/07/28)
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- PROCESS FOR MAKING BIARYL-BRIDGED CYCLIC PEPTIDES
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The invention provides a method of preparing a biaryl-bridged cyclic peptide compound of Formula (I), where R1, R2, R3, R4, R5, R8, R7, R8, R9, R10, R11, R12, n and m are as defined in the specification. The biaryl-bridged cyclic peptides of Formula (I) are used in the preparation of pharmaceutically active substances, such as, for example, arylomycin and arylomycin analogues.
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Page/Page column 97
(2021/06/04)
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- ALPHAvBETA1 INTEGRIN ANTAGONISTS
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The present disclosure provides pharmaceutical agents, including those of the formula: (I) wherein the variables are defined herein. Also provided are pharmaceutical compositions, kits and articles of manufacture comprising such pharmaceutical agents. Methods of using the pharmaceutical agents are also provided. The compounds may be used for the inhibition or antagonism of integrins ανβ1 and/or α5β1. In some embodiments, the compounds provided herein exhibit reduced inhibitory or antagonistic activity of integrins ανβ3, ανβ5, ανβ6, ανβ8, and/or αIIbβ3.
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Paragraph 0171; 0240
(2020/01/31)
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- Preparation method of cycloalkylaminophenol intermediate (by machine translation)
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The invention provides a preparation method, of a cycloalkylaminophenol intermediate. The method comprises the following steps: A) reacting an alkyl-substituted phenol, hexamethylenetetramine and acetic acid or a derivative thereof, obtaining first crude product; B) reacting the first crude product and the cycloalkylamine compound to obtain second crude product; C) reacting the second crude, the hydrogenated reducing agent in an alcohol solvent, and obtaining an aminophenol intermediate. The preparation method of the cycloalkylaminophenol intermediate is simple in process, mild in condition, and mild in condition. The prepared alkylaminophenol intermediate has good purity and yield, and is suitable for industrial production. (by machine translation)
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Paragraph 0073-0074; 0078
(2019/08/20)
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- Mononuclear Salen-Sodium Ion Pairs as Catalysts for Isoselective Polymerization of rac-Lactide
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A series of mononuclear salen-sodium anions, as the first examples, were synthesized with tetra-alkyl ammonium as a counterpart cation. These complexes are efficient catalysts for the isoselective ring-opening polymerization of rac-lactide; the molecular weights of polymers are under control and molecular weight distributions are narrow when five equivalents of BnOH is used as an initiator. The best isoselectivity value of Pm = 0.82 was achieved at -70 °C. The experimental results together with a density functional theory calculation show that a ligand-assisted activated monomer mechanism is more reasonable than an activated monomer mechanism for this system.
- Cui, Yaqin,Jiang, Jinxing,Mao, Xiaoyang,Wu, Jincai
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supporting information
p. 218 - 227
(2019/01/04)
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- Cobalt(II)[salen]-Catalyzed Selective Aerobic Oxidative Cross-Coupling between Electron-Rich Phenols and 2-Naphthols
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A selectivity-driven catalyst design approach was adopted to address chemoselectivity issues in the oxidative coupling of phenols. This approach was utilized for developing a Co(II)[salen]-catalyzed aerobic oxidative cross-coupling of phenols in a recyclable 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) solvent. The waste-free conditions offer a sustainable entry to nonsymmetric biphenols via a mechanistic scheme that involves coupling of a liberated phenoxyl radical with a ligated 2-naphthoxyl radical.
- Reiss, Hagai,Shalit, Hadas,Vershinin, Vlada,More, Nagnath Yadav,Forckosh, Hagit,Pappo, Doron
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supporting information
p. 7950 - 7960
(2019/06/07)
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- Copper(II)-Schiff Base Complex-Functionalized Polyacrylonitrile Fiber as a Green Efficient Heterogeneous Catalyst for One-Pot Multicomponent Syntheses of 1,2,3-Triazoles and Propargylamines
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A series of copper(II)-Schiff bases-functionalized polyacrylonitrile fiber catalysts were successfully prepared using copper acetate as copper source and characterized by elemental analysis, fourier-transfer infrared spectroscopy, ultraviolet-visible spectroscopy, X-ray photoelectron spectroscopy and inductively coupled plasma analysis. Excellent physical strength and thermal stability of the fiber catalysts were demonstrated by scanning electron microscopy, X-ray diffraction, thermogravimetric/differential scanning calorimetry analysis and mechanical strength measurements. Furthermore, these catalysts were successfully applied to one-pot multicomponent copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction and aldehyde, alkyne, amine (A3) coupling reaction in which the influences of different substituent groups on the catalytic activities of fiber catalysts were investigated in detail. Among them, the bis[N-ethyl-3,5-di-tert-butyl-salicylideneiminato]copper(II)-functionalized polyacrylonitrile fiber (PANS2F?Cu) as a green, efficient catalyst exhibited the best catalytic activity for its high hydrophobic micro-environment can aggregate the reactants to the catalytic sites and accelerate the reaction. In addition, the PANS2F?Cu has performed well in scaled-up experiment and shown excellent recyclability (at least ten times), and these enable it to have great potential for further applications. (Figure presented.).
- Li, Pengyu,Liu, Yuanyuan,Wang, Lu,Xiao, Jian,Tao, Minli
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supporting information
p. 1673 - 1684
(2018/03/21)
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- Efficient microwave-assisted regioselective one pot direct: Ortho -formylation of phenol derivatives in the presence of nanocrystalline MgO as a solid base catalyst under solvent-free conditions
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In this research, at first nanocrystalline MgO was prepared and then the solvent-free reactions of phenol derivatives with paraformaldehyde in the presence of the obtained nanocrystalline MgO as a new catalyst under microwave irradiation were investigated. In this reaction, ortho-hydroxyaromatic aldehydes were yielded as products. This method seems to be comparable with other reported methods due to its high yield and regioselectivity. The significant features of this method are short reaction times, high yields, and easy and quick isolation of the products.
- Naeimi, Hossein,Zakerzadeh, Elham
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p. 4590 - 4595
(2018/03/21)
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- Synthesis and structural characterization of a highly substituted triazine ring comprising a sterically flexible methylene linker and coordinating substituents
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The efficient multi-step, large-scale synthesis, spectroscopic characterization and solid-state molecular structure of a new type of three-fold functionalized, sterically demanding triazine is reported. The aromatic heterocycle 6,6′,6′'-((1,3,5-triazine-2,4,6-triyl)tris(methylene))tris(2,4-di-tert-butylphenol) possesses three 2,4-di-tert-butylphenol synthons bound to the 1,3,5-triazine ring via synthetically challenging methylene linkages in the 2,4,6 positions. The key to success was found in the generation of a highly reactive imidate hydrochloride salt, namely ethyl 2-(3,5-di-tert-butyl-2-methoxyphenyl)acetimidate hydrochloride, that readily undergoes cyclotrimerization. The reported preparation opens new perspectives in the design and synthesis of novel triazine molecules bearing flexible and sterically demanding functionalized groups for various applications.
- Werlé, Christophe,Yin, Chih-Juo Madeline,Heinemann, Frank W.,Hauser, Christina,Meyer, Karsten
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supporting information
p. 2715 - 2719
(2017/06/23)
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- Solvent dependent disproportionation of Cu(II) complexes of N2O2-type ligands: Direct evidence of formation of phenoxyl radical: An experimental and computational study
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Four Cu(II) complexes (1, 2, 3 and 4) with N2O2-type ligand, H2L1, H2L2, H2L3 and H2L4, respectively have been synthesized as the functional model for galactose oxidase. In presence of acetonitrile the Cu(II) centres in the complexes, undergo reduction with simultaneous oxidation of the ligands. The ligand oxidized products are isolated and characterized. Spectroscopic studies indicate that this disproportionation goes through the formation of a Cu(II)-phenoxyl intermediate. The complexes also undergoes the same reaction with pyridine, which indicates the involvement of the exergonic N-donor ligand for the formation of Cu(II)-phenoxyl complex. The Cu(II)-phenoxyl complexes are found to be stable in methanol in presence of a strong base. The paramagnetic centers in the Cu(II)-phenoxyl complexes were found to be weakly ferromagnetically coupled. The complexes, in acetonitrile solvent, have been found to oxidize primary alcohols to corresponding aldehydes. In absence of single crystal structures of the complexes, we optimized the structures using density functional theory (DFT). The UV-visible peaks of complexes as found from time dependent density functional theory (TDDFT) calculations match well with the observed experimental results.
- Debnath, Rajib Kumar,Kalita, Apurba,Sinha, Sourab,Bhattacharyya, Pradip Kr.,Mondal, Biplab,Ganguli, Jatindra Nath
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p. 4490 - 4500
(2015/11/27)
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- Highly Enantioselective Epoxidation of α,β-Unsaturated Ketones Catalyzed by Rare-Earth Amides [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 with Phenoxy-Functionalized Chiral Prolinols
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A simple and efficient catalytic enantioselective epoxidation of α,β-unsaturated ketones has been successfully developed, which was catalyzed by rare-earth metal amides [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 (RE = Yb (1), La (2), Sm (3), Y (4), Lu (5)) in the presence of phenoxy-functionalized chiral prolinols at room temperature using tert-butylhydroperoxide (TBHP) as the oxidant. The combination of an Yb-based amide 1 and a chiral proligand (S)-2,4-di-tert-butyl-6-((2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl)phenol) performed very well, and both the yields and the enantiomeric excess of the chiral epoxides reached up to 99% and 99% ee. (Figure Presented).
- Zeng, Chao,Yuan, Dan,Zhao, Bei,Yao, Yingming
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supporting information
p. 2242 - 2245
(2015/05/13)
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- Olefin polymerization and copolymerization by complexes bearing [ONNO]-Type salan ligands: Effect of ligand structure and metal type (titanium, zirconium, and vanadium)
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A series of novel titanium(IV) complexes bearing tetradentate [ONNO] salan type ligands: [Ti{2,2′-(OC6H3-5-t-Bu) 2-NHRNH}Cl2] (Lig1TiCl2: R = C 2H4; Lig2TiCl2: R = C 4H8; Lig3TiCl2: R = C 6H12) and [Ti{2,2′-(OC6H 2-3,5-di-t-Bu)2-NHC6H12NH}Cl 2] (Lig4TiCl2) were synthesized and used in the (co)polymerization of olefins. Vanadium and zirconium complexes: [M{2,2′-(OC6H3-3,5-di-t-Bu)2-NHC 6H12NH}Cl2] (Lig4VCl2: M = V; Lig4ZrCl2: M = Zr) were also synthesized for comparative investigations. All the complexes turned out active in 1-octene polymerization after activation by MAO and/or Al(i-Bu)3/[Ph 3C][B(C6F5)4]. The catalytic performance of titanium complexes was strictly dependent on their structures and it improves for the increasing length of the aliphatic linkage between nitrogen atoms (Lig1TiCl2 2TiCl2 3TiCl2) and declines after adding additional tert-Bu group on the aromatic rings (Lig3TiCl2 4TiCl2). The activity of all titanium complexes in ethylene polymerization was moderate and the properties of polyethylene was dependent on the ligand structure, cocatalyst type, and reaction conditions. The Et2AlCl-activated complexes gave polymers with lover molecular weights and bimodal distribution, whereas ultra-high molecular weight PE (up to 3588 kg mol-1) and narrow MWD was formed for MAO as a cocatalyst. Vanadium complex yielded PE with the highest productivity (1925.3 kg mol v-1), with high molecular weight (1986 kg mol -1) and with very narrow molecular weight distribution (1.5). Copolymerization tests showed that titanium complexes yielded ethylene/1-octene copolymers, whereas vanadium catalysts produced product mixtures.
- Bialek, Marzena,Pochwala, Monika,Spaleniak, Grzegorz
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p. 2111 - 2123
(2014/07/08)
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- Design of postmetallocene catalytic systems of arylimine type for olefin polymerization: XVI. Synthesis of (N-aryl)salicylaldimines containing pent-4-enyloxy group and their complexes with titanium(IV) dichloride
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Reactions of p-(pent-4-enyloxy)aniline with salicylaldehyde containing versatile substituents in the positions 3 and 5 in an open system without solvent at 130°C afforded a series of (N-aryl)salicylaldimines, which with TiCl2(OPr-i)2 formed complexes of titanium(IV) dichloride L2TiCl2.
- Oleinik,Oleinik,Zaitsev,Ivanchev
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p. 191 - 199
(2014/04/17)
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- Development of a halide-free aluminium-based catalyst for the synthesis of cyclic carbonates from epoxides and carbon dioxide
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Kinetic studies of the synthesis of glycerol carbonate from glycidol and carbon dioxide have been carried out. These showed that under suitable reaction conditions, bimetallic aluminium(salen) complex 4 is able to catalyse the conversion of epoxides into the corresponding cyclic carbonates without the need for a co-catalyst.
- Castro-Osma, Jose A.,North, Michael,Wu, Xiao
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supporting information
p. 15005 - 15008
(2015/01/08)
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- Facile one-pot transformation of phenols into o-cyanophenols
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The treatment of phenols with paraformaldehyde in the presence of MgCl2 and Et3N in THF at 80 C, followed by reaction with molecular iodine and aq. ammonia at room temperature provided the corresponding o-cyanophenols in moderate to good yields. The present reaction is a one-pot transformation of phenols into o-cyanophenols using much less expensive reagents than are typically used; the reaction is free of both transition-metals and cyanide. The utility of this reaction was highlighted during our preparation of Febuxostat from p-bromophenol.
- Nakai, Yuhta,Moriyama, Katsuhiko,Togo, Hideo
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p. 6077 - 6083
(2015/03/30)
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- A convenient approach for the deprotection and scavenging of the PMB group using POCl3
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A convenient and high yielding approach for the deprotection and scavenging of the p-methoxybenzyl (PMB) group in PMB ethers and PMB esters was developed using POCl3 as the reagent. 4-Methoxybenzyl chloride, a starting material used for the preparation of PMB ethers and esters was regenerated in the deprotection step. This mild and selective procedure tolerates several acid sensitive functional groups. The Royal Society of Chemistry 2013.
- Ilangovan, Andivelu,Saravanakumar, Shanmugasundar,Malayappasamy, Subramani,Manickam, Govindaswamy
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p. 14814 - 14828
(2013/09/02)
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- Formation of a Cu(II)-phenoxyl radical complex from a Cu(II)-phenolate complex: A new model for galactose oxidase
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A new N3O type tetradentate ligand (HL) [2,4-di-tert-butyl-6- ((4-(2-(6,8-di-tert-butyl-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethyl)piperazin-1-yl) methyl)phenol] and its complex [CuL(CH3OH)]ClO4(CH 3OH) have been synthesised. The complex has been crystallographically and spectroscopically characterised. It has been noticed that in the presence of acetonitrile the Cu(II) centers in the complex undergo reduction with a concomitant oxidation of the ligand. EPR and UV-Vis spectroscopic studies of the complex in acetonitrile indicate that this disproportionation proceeds via the formation of a Cu(II)-phenoxyl intermediate. The Cu(II)-phenoxyl complex is found to be stable in methanol in the presence of base. The oxidised products of the ligand are isolated and characterized. The paramagnetic centers in the Cu(II)-phenoxyl complexes were found to be weakly ferromagnetically coupled.
- Debnath, Rajib Kumar,Kalita, Apurba,Kumar, Pankaj,Mondal, Biplab,Ganguli, Jatindra Nath
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p. 222 - 227
(2013/04/23)
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- Heteroscorpionate-based Co2+,Zn2+, and Cu 2+ complexes: Coordination behavior, aerobic oxidation, and hydrogen sulfide detection
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The coordination behavior and reactivity of the phenol-substituted bis(pyrazolyl)methane ligands, (3,5-tBu2-2-phenol)-bis(3,5-Me 2-pyrazol-1-yl)methane (L1-H) and 2-phenol-bis(3,5-Me 2-pyrazol-1-yl)methane (L2-H) have been investigated in the metal complexes (L1-H)CoCl2 (l), (L1-H)ZnCl2 (2), (L3)CuCl 2 (3), (L2)2Co2Cl2 (4)(L2-H)ZnCl2 (5), and (L2-H)CuCl2 · H 2O (6). The mononuclear tetrahedral cobalt complex 1 was isolated and fully characterized by X-ray single crystal diffraction and 1H NMR spectroscopy and relaxometry. The neutral L1-H is κ2;-coordinated to the metal center whereas the not coordinated hydroxy-phenyl group is involved in extended intermolecular hydrogen bonds. Aerobic oxidation of L1-H was observed in the reaction of this ligand with CuCl2 to yield the para-quinone derivative L3 (L3 = 2-tBu-6-(bis(3,5-Me2-pyrazol-1-yl)methyl) cyclohexa-2,5-diene-1,4-dione). Upon oxidation L3 resulted κ2-coordinated to the tetrahedral Cu(II) metal center, affording 3. The reaction of L2-H with CoCl2 6H2O produced the elimination of 1 equiv of hydrochloric acid and the formation of the binuclear complex 4 in which one cobalt is in an octahedral environment featuring two κ3-coordinated deprotonated ligands whereas the second cobalt center is detected in tetrahedral coordination geometry, bound to the octahedral cobalt via two phenoxo bridging moieties. Interestingly L2-H, (3-tBu-2-phenol)bis(3,5-Me2-pyrazol-1- yl)methane (L4-H),or (5-tBu-2-phenol)b/s(3,5-Me2-pyrazol-1-yl)methane (L5-H) were not oxidized in the reaction with CuCl2. The reaction of the ligand L2-H with ZnCl2 and CuCl2 2H2O yielded the κ2-coordinated tetrahedral complex 5 and the square planar complex 6, respectively. The application of the cobalt complex 1 as molecular dosimeter for H2S was explored and compared to that of the zinc analogue 2. Density functional theory (DFT) calculations and NMR experiments to assess the possible mechanisms of H2S detection by both 1 and 2 are also described.
- Strianese, Maria,Milione, Stefano,Bertolasi, Valerio,Pellecchia, Claudio,Grassi, Alfonso
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body text
p. 900 - 910
(2011/04/16)
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- Large ultra-high molecular weight polyethylene spherical particles produced by AlR3 activated half-sandwich chromium(iii) catalysts
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A series of half-sandwich pentamethylcyclopentadienyl chromium(iii) complexes bearing a salicylaldiminato ligand, Cp*[2-R1-4-R 2-6-(CHNR3)C6H2O]CrCl [R1 = iPr (1, 4), tBu (2, 3, 5), Ad (6); R2 = H (1, 2, 3), tBu (4, 5, 6); R3 = iPr (1, 2, 5, 6), tBu (3, 4)], were synthesized. All complexes were characterized by elemental analyses and the structures of complexes 1-4 and 6 were determined by X-ray diffraction analysis. These complexes adopt a pseudo-octahedral coordination environment with a three-legged piano stool geometry. Upon activation with a small amount of AlR3, complexes 1-6 all catalyze the polymerization of ethylene in a quasi living fashion with good to high catalytic activity under mild conditions and produce ultra-high molecular weight polyethylene as spherical particles with a diameter of 1-6 mm. The catalytic activity of these complexes and the molecular weight of the produced polyethylene can be tuned in a broad range by changing the R1, R 2, and R3 groups as well as the AlR3 cocatalyst. It was found that complex 6 with R1 = Ad, R2 = tBu, and R3 = iPr shows the highest catalytic activity and produces polyethylene with the highest molecular weight. The Royal Society of Chemistry 2011.
- Sun, Mingtai,Xu, Tieqi,Gao, Wei,Liu, Yang,Wu, Qiaolin,Mu, Ying,Ye, Ling
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scheme or table
p. 10184 - 10194
(2011/12/05)
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- Reducing the cost of production of bimetallic aluminium catalysts for the synthesis of cyclic carbonates
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Bimetallic aluminium complexes of general formula [(salen)Al]2O or [(acen)Al]2O catalyse the formation of cyclic carbonates from carbon dioxide and terminal epoxides under exceptionally mild reaction conditions. To improve the potential for industrial scale application of these catalysts, the cost of their production has been evaluated and reduced significantly by optimization of the synthesis, including replacement of the most expensive chemicals by less expensive alternatives. The largest cost saving was associated with the formation of aluminium triethoxide insitu, which reduced the cost of the chemicals need for production of the catalysts by 49-87%. Further savings were made by avoiding the use of tetrabutylammonium bromide and acetonitrile, resulting in overall cost savings of 68-93%. Copyright
- North, Michael,Young, Carl
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scheme or table
p. 1685 - 1693
(2012/03/10)
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- Mononuclear iron(III) complexes supported by tripodal N3O ligands: Synthesis, structure and reactivity towards DNA cleavage
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A new synthetic route to the known tripodal tetradentate N3O ligand L1 (HL1 = [N-(3,5-di-tert-butyl-2-hydroxybenzyl)-N,N-di-(2-pyridylmethyl)]amine) is reported. The related compounds HLn (n = 2, 3) were prepared by a similar procedure. Treatment of HLn (n = 1-3) with FeCl3·6H2O in hot methanol led to the mononuclear iron(III) complexes [Fe(Ln)Cl2] (1: n = 1, 2: n = 2, 3: n = 3). The solid-state structures of complexes 1 and 2 were determined by X-ray crystallography. [Fe(L1)Cl2] (1) showed effective nuclease activity in the presence of hydrogen peroxide, converting supercoiled plasmid DNA to its linear form.
- Wong, Yee-Lok,Mak, Chun-Yin,Kwan, Hoi Shan,Lee, Hung Kay
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experimental part
p. 1246 - 1253
(2010/07/05)
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- Asymmetric synthesis of a new salen type-titanium complex as the catalyst for asymmetric trimethylsilylcyanation of aldehydes
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This work describes the asymmetric synthesis of a new salen-type ligand via a Diels-Alder reaction and Curtius rearrangement. The ligand with a norbornane skeleton was used in the trimethylsilylcyanation of aldehydes, but the enantioselectivity was 55%ee. The norborane skeleton was cleaved to destroy this rigidity, and the eanatioselectivity was thereby increased to 85%ee.
- Lin, Zheng-Chang,Chen, Chinpiao
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experimental part
p. 726 - 737
(2011/04/23)
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- New dioxo-molybdenum(vi) and -tungsten(vi) complexes with N-capped tripodal N2O2 tetradentate ligands: Synthesis, structures and catalytic activities towards olefin epoxidation
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A series of N2O2 tripodal tetradentate ligands derived from di-/tetra-tert-butyl substituted 2-[bis(2-hydroxybenzyl) aminomethyl]X (X = pyridine and benzimidazole) (H2Ln (n = 1-4)) and 8-[bis(3,5-di-tert-butyl-2-hydroxybenzyl)]aminoquinoline (H 2L5) were synthesised through a 4-step reaction scheme involving sequential formylation, reduction, bromination and alkylation. Treatment of H2Ln (n = 1-5) with [WO2Cl 2(dme)] (dme = 1,2-dimethoxyethane) in the presence of triethylamine gave the corresponding cis-dioxotungsten(vi) complexes [WO2(L n)] (n = 1-5). The corresponding molybdenum analogues [MoO 2(Ln)] (n = 1-5) were also prepared from the reaction of [MoO2(acac)2] (acac = acetylacetonate) with H 2Ln (n = 1-3) or [MoO2Cl2(dme)] (dme = 1,2-dimethoxyethane) with H2Ln (n = 4 and 5). All these compounds were fully characterised by a wide range of spectroscopic methods. The molecular structures of [MoO2(Ln)] (n = 2, 4) and [WO2(L2)] were also confirmed by single-crystal X-ray diffraction analysis. The catalytic activities of [MO2(L n)] (M = Mo, W; n = 1-4) towards epoxidation of styrene were also examined.
- Wong, Yee-Lok,Tong, Lok H.,Dilworth, Jonathan R.,Ng, Dennis K. P.,Lee, Hung Kay
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supporting information; experimental part
p. 4602 - 4611
(2010/08/22)
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- Titanium-salan-catalyzed asymmetric oxidation of sulfides and kinetic resolution of sulfoxides with H2O2 as the oxidant
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Asymmetric oxidation of sufides to sulfoxides by aqueous hydrogen peroxide with catalysis by titanium-salan complexes is presented. Optically active sulfoxides have been obtained with good to high enantioselectivities (up to 97% ee) by a tandem enantioselective oxidation and kinetic resolution procedure, the catalyst performing over 500 turnovers with no loss of enantioselectivity. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Bryliakov, Konstantin P.,Talsi, Evgenii P.
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experimental part
p. 3369 - 3376
(2009/04/07)
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- New opportunities for duff reaction
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Reaction of 2,4-di-tert-butylphenol with urotropin in conditions of Duff reaction takes an abnormal route and instead of the expected di-tert-butylsalicylaldehyde provides a mixture of N-substituted 3,5-di-tert-butyl-2-hydroxybenzylamines and redox conjugate benzoxazines containing mostly 6,8-di-tert-butyl-3-(3,5-di-tert-butyl-2-hydroxybenzyl)-2H-3, 4-dihydrobenz[e][1,3]oxazine. A solvolysis of an individual benzoxazine in the system HO(CH2)2OH-H2O-HCl affords di(3,5-di-tert-butyl-2-hydroxybenzyl)amine, and in AcOH 3,5-di-tert- butylsalicilaldehyde. A mechanism of Duff reaction was suggested involving the formation of a benzoxazine intermediate. 2005 Pleiades Publishing, Inc.
- Belostotskaya,Komissarova,Prokof'Eva,Kurkovskaya,Vol'Eva
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p. 703 - 706
(2007/10/03)
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- A high yielding one-pot method for the preparation of salen ligands
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Phenols are converted to salicylaldehydes with paraformaldehyde, MgCl 2-Et3N in THF, and subsequently treated with (+)-(R,R)-1,2-diammoniumcyclohexane mono-(+)-tartrate salt affording the corresponding salen ligands in high yields. The reactions are conveniently carried out as a one-pot procedure.
- Hansen, Trond Vidar,Skatteb?l, Lars
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p. 3829 - 3830
(2007/10/03)
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- Non-metallocene compounds, method for the production thereof and use of the same for the polymerisation of olefins
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The invention relates to a method for producing special transition metal compounds, to novel transition metal compounds and to the use of the same for the polymerisation of olefins.
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- Syndiospecific living propylene polymerization catalyzed by titanium complexes having fluorine-containing phenoxy-imine chelate ligands
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The propylene polymerization behavior of a series of Ti complexes featuring fluorine-containing phenoxy-imine chelate ligands is reported. The Ti complexes combined with methylalumoxane (MAO) can be catalysts for living and, at the same time, stereospecific polymerization of propylene at room temperature or above. DFT calculations suggest that the attractive interaction between a fluorine ortho to the imine nitrogen and a β-hydrogen of a growing polymer chain is responsible for the achievement of room-temperature living propylene polymerization. Although the Ti complexes possess C2 symmetry, they are capable of producing highly syndiotactic polypropylenes. 13C NMR is used to demonstrate that the syndiotacticity is governed by a chain-end control mechanism and that the polymerization is initiated exclusively via 1,2-insertion followed by 2,1-insertion as the principal mode of polymerization. 13C NMR spectroscopy also elucidated that the polypropylenes produced with the Ti complexes possess regio-block structures. Substitutions on the phenoxy-imine ligands have profound effects on catalytic behavior of the Ti complexes. The steric bulk of the substituent ortho to the phenoxy oxygen plays a decisive role in achieving high syndioselectivity for the chain-end controlled polymerization. Over a temperature range of 0-50 °C, Ti complex having a trimethylsilyl group ortho to the phenoxy oxygen forms highly syndiotactic, nearly monodisperse polypropylenes (94-90% rr) with extremely high peak melting temperatures (Tm = 156- 149 °C). The polymerization behavior of the Ti complexes can be explained well by the recently proposed site-inversion mechanism for the formation of syndiotactic polypropylene by a Ti complex having a pair of fluorine-containing phenoxy-imine ligands.
- Mitani, Makoto,Furuyama, Rieko,Mohri, Jun-ichi,Saito, Junji,Ishii, Seiichi,Terao, Hiroshi,Nakano, Takashi,Tanaka, Hidetsugu,Fujita, Terunori
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p. 4293 - 4305
(2007/10/03)
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- Fluorine- and trimethylsilyl-containing phenoxy-imine Ti complex for highly syndiotactic living polypropylenes with extremely high melting temperatures
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A fluorine- and trimethylsilyl-containing phenoxy-imine titanium complex was synthesized and the structure was determined by an X-ray analysis. The complex on activation with MAO initiates highly controlled syndiospecific living propylene polymerization to form extremely high Tm syndiotactic polypropylenes (Mw/Mn = 1.05-1.08, Tm = 156-152 °C) at 0 or 25 °C. Moreover, at 50 °C, the complex afforded monodisperse syndiotactic polypropylene with very high Tm's of 149, 150 °C. In contrast, complexes having a t-Bu group instead of the silyl group provided lower tacticity polymers with much lower Tm's. In addition, we revealed the substituent effect that plays a key role for the highly controlled syndiospecific polymerization displayed by the catalyst. Copyright
- Mitani, Makoto,Furuyama, Rieko,Mohri, Jun-ichi,Saito, Junji,Ishii, Seiichi,Terao, Hiroshi,Kashiwa, Norio,Fujita, Terunori
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p. 7888 - 7889
(2007/10/03)
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- An improved method for synthesis of Jacobsen's catalyst
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The improved synthesis of Jacobsen catalyst 1 was developed. For both enantiomers the obtained overall yield starting from commercially available 4 was 80-85%.
- Cepanec,Mikuldas,Vinkovic
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p. 2913 - 2919
(2007/10/03)
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- Effects of metal ions on physicochemical properties and redox reactivity of phenolates and phenoxyl radicals: Mechanistic insight into hydrogen atom abstraction by phenoxyl radical-metal complexes
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Phenolate and phenoxyl radical complexes of a series of alkaline earth metal ions as well as monovalent cations such as Na+ and K+ have been prepared by using 2,4-di-tert-butyl-6-(1,4,7,10-tetraoxa-13-aza-cyclopentadec-13-ylmethyl) phenol (L1H) and 2,4-di-tert-butyl-6-(1,4,7,10,13-pentaoxa-16-aza-cyclo-octadec-16-ylmethyl) phenol (L2H) to examine the effects of the cations on the structure, physicochemical properties and redox reactivity of the phenolate and phenoxyl radical complexes. Crystal structures of the Mg2+- and Ca2+-complexes of L1- as well as the Ca2+- and Sr2+-complexes of L2- were determined by X-ray crystallographic analysis, showing that the crown ether rings in the Ca2+-complexes are significantly distorted from planarity, whereas those in the Mg2+- and Sr2+-complexes are fairly flat. The spectral features (UV-vis) as well as the redox potentials of the phenolate complexes are also influenced by the metal ions, depending on the Lewis acidity of the metal ions. The phenoxyl radical complexes are successfully generated in situ by the oxidation of the phenolate complexes with (NH4)2[Ce4+(NO3)6] (CAN). They exhibited strong absorption bands around 400 nm together with a broad one around 600-900 nm, the latter of which is also affected by the metal ions. The phenoxyl radical-metal complexes are characterized by resonance Raman, ESI-MS, and ESR spectra, and the metal ion effects on those spectroscopic features are also discussed. Stability and reactivity of the phenoxyl radical-metal complexes are significantly different, depending on the type of metal ions. The disproportionation of the phenoxyl radicals is significantly retarded by the electronic repulsion between the metal cation and a generated organic cation (Ln+), leading to stabilization of the radicals. On the other hand, divalent cations decelerate the rate of hydrogen atom abstraction from 10-methyl-9,10-dihydroacridine (AcrH2) and its 9-substituted derivatives (AcrHR) by the phenoxyl radicals. On the basis of primary kinetic deuterium isotope effects and energetic consideration of the electron-transfer step from AcrH2 to the phenoxyl radical-metal complexes, we propose that the hydrogen atom abstraction by the phenoxyl radical-alkaline earth metal complexes proceeds via electron transfer followed by proton transfer.
- Itoh,Kumei,Nagatomo,Kitagawa,Fukuzumi
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p. 2165 - 2175
(2007/10/03)
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- NBS-Promoted Reactions of Symmetrically Hindered Methylphenols via p-Benzoquinone Methide
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Symmetrically hindered methylphenols 1 react smoothly with NBS to form transient intermediates, p-benzoquinone methides (BM), which can be further processed to give hydroxybenzaldehydes in the presence of DMSO. This reaction is initiated by the formation of the phenoxy radical, followed by disproportionation to afford BM. None of the side-chain-brominated product is observed. The existence of BM is supported by the following observations: the formation of BM in solution can be monitored by GC and GC-MS; the electrophilic methine part participates in electrophilic aromatic substitution with anisoles to give hydroxybenzylated products 15; and the double bond character of the exocyclic methine plays a role in [4 + 2] cycloaddition with diene to afford Diels-Alder adducts. In contrast, unsymmetrically hindered or simple methylphenol (p-cresol) with NBS gives the nuclear brominated products, as usual. The energies of symmetrically hindered BMs, unsymmetrically hindered BM, and simple BM were calculated using density functional theories. Relative stabilization energies calculated at the B3LYP/6-31G*//B3LYP/6-31G* level by an isodesmic equation are enhanced 3-6 kcal/mol for symmetrically hindered BMs.
- Baik, Woonphil,Lee, Hyun Joo,Jang, Jung Min,Koo, Sangho,Kim, Byeong Hyo
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p. 108 - 115
(2007/10/03)
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- Trialkylamine controlled phenol-for maldehyde reaction over clay catalysts: Selective and environmentally benign synthesis of salicylic aldehydes
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Substituted salicylic aldehydes 6 are synthesised in good yields and excellent selectivities by reaction of phenols 1 with formaldehyde 2 over montmorillonite KSF-Et3N as a heterogeneous and reusable catalyst. (C) 2000 Elsevier Science Ltd.
- Bigi, Franca,Conforti, Maria Lina,Maggi, Raimondo,Sartori, Giovanni
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p. 2709 - 2712
(2007/10/03)
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- Polystyrene and polymethacrylate resin-supported Jacobsen's alkene epoxidation catalyst
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Polystyrene and polymethacrylate-based resin supported Jacobsen's chiral Mn salen complexes have been prepared. The resins are of defined molecular structure and morphology, and the complexes have been attached primarily in a pendant fashion. The loadings of Mn(In) are in the range ～0.08-0.35 mmol g-1 to maximise the likelihood of site-isolation. The polymer-supported complexes have been used as enantioselective catalysts in the epoxidation of 1,2-dihydronaphthalene, indene, 1-phenylcyclohex-1-ene and 1-phenyl-3,4-dihydronaphthalene using m-chloroperbenzoic acid as the oxidant and 4-methylmorpholine N-oxide as the co-oxidant. Though the activities of the polymer catalysts are reduced relative to the soluble homogeneous analogue, the catalysts are sufficiently active to be useful. The corresponding reduction in enantioselectivity is more significant, and is both substrate and polymer resin dependent. However, in the case of 1-phenylcyclohex-1-ene and a macroporous polymethacrylate-based resin the enantioselectivity is equivalent to that of the soluble complex (91-92% ee). This is the first report of a polymersupported analogue of Jacobsen's catalyst being as selective as the homogeneous species. The catalysis data is discussed in detail in the context of the design of the polymer-supported system, and the existing data already available in the literature. Attempts have also been made to recycle the polymer catalysts with and without re-loading of Mn. In fact the level of leaching of Mn is very low, but the catalysts show a very rapid fall off in both activity and selectivity in the first and second cycles. Overall therefore it seems that the intrinsic stability of the chiral Mn(II) salen complex itself is too low to allow viable recycling, and the development of other more stable supported chiral metal salen complexes for use in other enantioselective reactions seems a better future option.
- Canali, Laetitia,Cowan, Elaine,Deleuze, Herve,Gibson, Colin L.,Sherrington, David C.
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p. 2055 - 2066
(2007/10/03)
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- Oxidation of 2-dialkylaminomethyl-4,6-di-tert-butylphenols
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Oxidative transformations of 2-dialkylaminomethyl-4,6-di-tert-butylphenols depend on the nature of the oxidant, the character of the substituents at the nitrogen atom, and the medium. A mechanism of the oxidation of these compounds is suggested. The molecular structure of the compound obtained as a result of oxidative trimerization of 2-dimethylaminomethyl-4,6-di-tert-butylphenol was established by X-ray structural analysis.
- Belostotskaya,Vol'eva,Komissarova,Dekaprilevich,Khrustalev,Karmilov,Ershov
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p. 1272 - 1280
(2007/10/03)
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- Modelle fuer Reaktionen am aktiven Zentrum der Galactose-Oxidase
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Keywords: Galactose-Oxidase; Kupferverbindungen; Oxidationen; Radikale
- Halfen, Jason A.,Young, Victor G.,Tolman, William B.
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p. 1832 - 1835
(2007/10/03)
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- Highly efficient preparation of optically active 5-hydroxy-3-oxoesters by enantioselective reaction of diketene with aldehydes promoted by novel chiral Schiff base-titanium alkoxide complexes
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Optically active 5-hydroxy-3-oxoesters 1 can be obtained in up to 91% enantiomeric excess (e.e.) by the enantioselective reaction of diketene with aldehydes promoted by novel chiral Schiff base-titanium alkoxide complexes.
- Hayashi,Tanaka,Oguni
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p. 1833 - 1836
(2007/10/03)
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- Process for 3,5-di-tert-butylsalicylaldehyde
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A process for the synthesis of 3-5-tert-butylsalicylaldehyde from 2,4-di-tert-butylphenol and hexamethylenetetramine is disclosed. The reaction provides 3,5-tert-butylsalicylaldehyde in commercially attractive yields from readily available starting materials.
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- Sterically hindered, regenerable Schiff base complexes, solutions thereof and process using the same
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There are disclosed saltmen-type metallo Schiff base complexes and oxygen-sorbing and -desorbing solutions of the same, pressure- and temperature-swing oxygen separation processes using the complexes and solutions, and methods of regenerating such complexes and solutions.
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- Photochromatic compound, a method for its preparation, and articles which contain it
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A photochromatic compound represented by the following general formula (I): STR1 where: R1 and R2 independently represent a linear, branched or cyclic C1-C10 alkyl radical, H, OH, F, Cl, Br, NH2, N(R4)2, COOH, OR4 or COOR4 where R4 is a C1-C10 linear, branched or cyclic alkyl radical, or an aryl radical; R3 is a variously substituted mono or polycondensed heterocyclic or aryl radical. A compound (I) demonstrates marked photochromatic characteristics both when in an organic solvent solution and when incorporated into polymer matrices.
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- Steric acceleration of intramolecular cycloaddition reactions
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Use of conformational constraints, induced by different ortho-substituents in 1-allyloxy-2-(substituted)methylbenzenes, where the substituent is a 1,3-dipole such as the azide or 3-oxidopyridinium group, can be employed to accelerate the 1,3-dipolar cycloaddition reaction. In this manner cycloadditions that otherwise do not proceed can be forced to react.
- Orlek, Barry S.,Sammes, Peter G.,Weller, David J.
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p. 8179 - 8194
(2007/10/02)
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- SEMI-HINDERED PHENOLS. 1. SYNTHESIS OF 3,5-DI-TERT-BUTYLSALICYLIC ALDEHYDE
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Some differences were observed in the solid- and liquid-phase benzylic oxidation of 2-(hydroxy- or dialkylamino)methyl-4,6-di-tert-butylphenols.Oxidation of these semi-hindered phenols with lead tetraacetate gave a new compound: 3,5-di-tert-butyl-ortho-benzoquinone diacylal.Keywords: semi-hindered phenols, synthesis, aldehyde, benzylic alcohol, oxidation, liquid phase, solid phase.
- Dokukina, M. A.,Vol'eva, V. B.,Belostotskaya, I. S.,Komissarova, N. L.,Karmilov, A. Yu.,Ershov, V. V.
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p. 1868 - 1870
(2007/10/02)
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