- Copper(II) complexes of piperazine-derived tetradentate ligands and their chiral diazabicyclic analogues for catalytic phenol oxidative C-C coupling
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Reaction of the chiral ligands (1S,4S)-2,5-bis(6-methylpyridyl)- diazabicyclo[2.2.1]heptane (L1) and (1S,4S)-2,5-bis(1-methyl-2- methylbenzimidazolyl)-diazabicyclo[2.2.1]heptane (L2) with CuCl 2 results in the hydroxo-bridged dicopper complexes [(L 1)Cu2(μ-OH)(H2O)Cl3] (3), and [(L2)Cu2(μ-OH)(H2O)Cl3] (4). Both chiral complexes were characterized spectroscopically, and 3 in the solid state by X-ray crystallography, confirming they are structurally related to their previously reported copper acetate analogues (1 and 2) due to their hydroxo-bridged bimetallic core. The achiral ligand analogues N,N′-bis(2-picolyl)piperazine (L3) and N,N′-bis(1-methyl- 2-methylbenzimidazolyl)piperazine (L4) were employed to obtain the corresponding complexes with CuCl2, affording the chloro-bridged [(L3)(CuCl)2(μ-Cl)2]n (5) and [(L4)(CuCl)2(μ-Cl)2] (6), neither of which features a bridging hydroxo ligand; instead, complex 5 was structurally characterized as a coordination polymer. The acetate-derived complexes 1 and 2 are active in oxidative C-C coupling of 2,4-di-tert-butylphenol, while 3 and 4 have low activity; the achiral complexes 5 and 6, lacking a bridging hydroxo ligand, are inactive in this reaction.
- Castillo, Ivan,Pérez, Viridiana,Monsalvo, Iván,Demare,Regla, Ignacio
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- Bismuthanes as Hemilabile Donors in an O2-Activating Palladium(0) Complex
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A xanthene-based bismuthane/phosphane chelating ligand has been accessed that has enabled the synthesis of a palladium(0) bismuthane complex. The bismuthane donor proved to be hemilabile as it switched to a dangling position upon addition of O2 that gave a palladium(II) peroxide complex. Unlike the corresponding 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) palladium peroxide, the bismuth analogue could be employed for catalytic phosphane oxidation and oxidative phenol coupling.
- Materne, Karolin,Braun-Cula, Beatrice,Herwig, Christian,Frank, Nicolas,Limberg, Christian
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- Unprecedented direct cupric-superoxo conversion to a bis-μ-oxo dicopper(III) complex and resulting oxidative activity
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Investigations of small molecule copper-dioxygen chemistry can and have provided fundamental insights into enzymatic processes (e.g., copper metalloenzyme dioxygen binding geometries and their associated spectroscopy and substrate reactivity). Strategically designing copper-binding ligands has allowed for insight into properties that favor specific (di)copper-dioxygen species. Herein, the tetradentate tripodal TMPA-based ligand (TMPA = tris((2-pyridyl)methyl)amine) possessing a methoxy moiety in the 6-pyridyl position on one arm (OCH3TMPA) was investigated. This system allows for a trigonal bipyramidal copper(II) geometry as shown by the UV–vis and EPR spectra of the cupric complex [(OCH3TMPA)CuII(OH2)](ClO4)2. Cyclic voltammetry experiments determined the reduction potential of this copper(II) species to be ?0.35 V vs. Fc+/0 in acetonitrile, similar to other TMPA-derivatives bearing sterically bulky 6-pyridyl substituents. The copper-dioxygen reactivity is also analogous to these TMPA-derivatives, affording a bis-μ-oxo dicopper(III) complex, [{(OCH3TMPA)CuIII}2(O2?)2]2+, upon oxygenation of the copper(I) complex [(OCH3TMPA)CuI](B(C6F5)4) at cryogenic temperatures in 2-methyltetrahydrofuran. This highly reactive intermediate is capable of oxidizing phenolic substrates through a net hydrogen atom abstraction. However, after bubbling of the precursor copper(I) complex with dioxygen at very low temperatures (?135 °C), a cupric superoxide species, [(OCH3TMPA)CuII(O2[rad]?)]+, is initially formed before slowly converting to [{(OCH3TMPA)CuIII}2(O2?)2]2+. This appears to be the first instance of the direct conversion of a cupric superoxide to a bis-μ-oxo dicopper(III) species in copper(I)-dioxygen chemistry.
- Quist, David A.,Ehudin, Melanie A.,Karlin, Kenneth D.
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- Oxidant-Controlled Catalytic Transformations of Phenols with Unexpected Cleavage of Aromatic Rings
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Oxidative transformations of phenols have attracted significant attention of chemists due to their importance in biological process and organic synthesis. In contrast to the relatively well-developed oxygenation and coupling reactions of phenols, the highly efficient and selective oxidative ring cleavage of phenols is under-represented. This work describes a novel CuCl-catalyzed tandem homocoupling/skeletal rearrangement of phenols that realizes the cleavage of the phenol ring by using air or Ag2CO3 as the oxidant. Interestingly, simply changing the oxidant to K2S2O8 results in the oxidative coupling/cyclization of phenols to give dibenzofurans. These results set an important precedent of oxidant-controlled catalytic transformations of phenols.
- Li, Wei,Song, Feijie,You, Jingsong
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- Activation of a high-valent manganese-oxo complex by a nonmetallic lewis acid
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The reaction of a manganese(V)-oxo porphyrinoid complex with the Lewis acid B(C6F5)3 leads to reversible stabilization of the valence tautomer MnIV(O)(π-radical cation). The latter complex, in combination with B(C6F5)3, reacts with ArO-H substrates via formal hydrogen-atom transfer and exhibits dramatically increased reaction rates over the MnV(O) starting material.
- Baglia, Regina A.,Duerr, Maximilian,Ivanovic-Burmazovic, Ivana,Goldberg, David P.
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- A Bis(μ-oxido)dinickel(III) Complex with a Triplet Ground State
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A bis(μ-oxido)dinickel(III) complex was synthesized and characterized by single crystal X-ray diffraction, resonance Raman, and ESI-mass measurements. Magnetic susceptibility measurements by SQUID and EPR spectroscopy reveal that the complex has a triplet ground state, which is unprecedented for high-valent metal (M) complexes with [M2(μ-O)2] diamond core. DFT studies indicate ferromagnetic coupling of the nickel(III) centers. The complex exhibits hydrogen abstraction reactivity and oxygenation reactivity toward external substrates.
- Morimoto, Yuma,Takagi, Yusaku,Saito, Toru,Ohta, Takehiro,Ogura, Takashi,Tohnai, Norimitsu,Nakano, Motohiro,Itoh, Shinobu
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- Influence of ligand architecture on oxidation reactions by high-valent nonheme manganese oxo complexes using water as a source of oxygen
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Mononuclear nonheme MnIV=O complexes with two isomers of a bispidine ligand have been synthesized and characterized by various spectroscopies and density functional theory (DFT). The MnIV=O complexes show reactivity in oxidation reactions (hydrogen-atom abstraction and sulfoxidation). Interestingly, one of the isomers (L1) is significantly more reactive than the other (L2), while in the corresponding FeIV=O based oxidation reactions the L2-based system was previously found to be more reactive than the L1-based catalyst. This inversion of reactivities is discussed on the basis of DFT and molecular mechanics (MM) model calculations, which indicate that the order of reactivities are primarily due to a switch of reaction channels (σ versus π) and concomitant steric effects.
- Barman, Prasenjit,Vardhaman, Anil Kumar,Martin, Bodo,W?rner, Svenja J.,Sastri, Chivukula V.,Comba, Peter
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- Copper(i) complexes based on ligand systems with two different binding sites: Synthesis, structures and reaction with O2
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The synthesis of the ligand systems L1 and L2 with two different N3-binding sites linked through a dibenzofuran spacer and their coordination properties towards a variety of CuI precursors are reported. The reaction of L1 with copper halides leads to the formation of a bimetallic species [(L1)(CuICl)2] (1), and metallodimers [((L1)(CuIX)2)2(μ-(CuI2)(μ-X)2)] (2: X = Br, 3: X = I) in which two dicopper complexes are bridged by a (μ-(CuI2)(μ-X)2)-moiety whereas L2 reacts with copper chloride to afford {[CuI2(L2)Cl2]}n (8). Furthermore, starting from L1 in combination with copper(i) salts of weakly coordinating anions the dicopper complexes [(L1)(CuI(NCCH3))2](BF4)2 (4), [(L1)(CuI(NCCH3))(Cu(Y))](Y) (5: Y = OTf, 6: Y = ClO4) and [(L1)(CuI2(dppe))](PF6)2 (7) were isolated, and employing L2, the complexes [(L2)(CuI(NCCH3))2](Z)2 (9: Z = PF6, 10: Z = OTf) and [(L2)(CuI2(dppe))](PF6)2 (11) were obtained. Complexes 4-6 as well as 9 and 10 react rapidly with O2 to form metastable O2 adducts in acetone at -90 °C, where O2 is bound between the two copper centers within one dicopper molecule, as evidenced by UV/Vis spectroscopy, kinetic investigations, Raman spectroscopy and studies with ligands containing the isolated donor sites. The reactivity of the O2 adducts towards selected substrates was also investigated, showing their ability to act as electrophiles as well as nucleophiles.
- Li,Braun-Cula,Hoof,Limberg
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- Direct Resonance Raman Characterization of a Peroxynitrito Copper Complex Generated from O2 and NO and Mechanistic Insights into Metal-Mediated Peroxynitrite Decomposition
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We report the formation of a new copper peroxynitrite (PN) complex [CuII(TMG3tren)(κ1-OONO)]+ (PN1) from the reaction of [CuII(TMG3tren)(O2.?)]+ (1) with NO.(g) at ?125 °C. The first resonance Raman spectroscopic characterization of such a metal-bound PN moiety supports a cis κ1-(?OONO) geometry. PN1 transforms thermally into an isomeric form (PN2) with κ2-O,O′-(?OONO) coordination, which undergoes O?O bond homolysis to generate a putative cupryl (LCuII?O.) intermediate and NO2.. These transient species do not recombine to give a nitrato (NO3?) product but instead proceed to effect oxidative chemistry and formation of a CuII–nitrito (NO2?) complex (2).
- Liu, Jeffrey J.,Siegler, Maxime A.,Karlin, Kenneth D.,Mo?nne-Loccoz, Pierre
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- Oxidation of 2,4-Di-t-butylphenol with Hydrogen Peroxide Catalyzed by Bis(ethylenediamine)copper(II) Complex
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2,4-Di-t-butylphenol (1) was efficiently oxidized with H2O2 in methanol in the presence of bis(ethylenediamine)copper(II) (Cu(II)(en)2 complexes.Activity of the Cu(II) complexes was strongly dependent on the structure of the en ligands, as in the cases of the O2 oxidation of phenol I.In the H2O2 oxidation of I, ens having none of N-alkyl substituent were of the most efficient.By addition of H2O2, stable Cu(II)(en)2 complexes exhibited a new absorption at 340 nm, which was assigned to Cu(II)-en-H2O2 (1:2:1) complexes.Furthermore, the rapid-scanning spectrophotometry proved that quadruple Cu(II)-en-phenol 1-H2O2 (1:1:1) complexes were the key intermediate for the oxidation of 1.The initial velocity can be summarized in the equation υ = k.The oxidation mechanism of phenol I with H2O2 is proposed.
- Kushioka, Keiko,Tanimoto, Iwao,Maruyama, Kazuhiro
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- Cu(II)-mediated phenol oxygenation: Chemical evidence implicates a unique role of the enzyme active site in promoting the chemically difficult tyrosine monooxygenation in TPQ cofactor biogenesis of copper amine oxidases
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Cu(II)-mediated autoxidations of 4-tert-butylphenol under various conditions was studied, the data confirmed imidazole is the best ligand to promote phenol oxygenation. The same reaction of 2,4-di-tert-butylphenol proceeded much more quickly to lead nearly exclusively to oxidative coupling rather than oxygenation under high pressure O2. These results suggested that Cu(II)-catalyzed phenol autoxidation by activating O2 and phenol in terms of a phenoxy radical (ArO.)-Cu(II)-superoxide ternary complex, whereas selectivity between oxygenation and coupling depends mainly on the electronic structure of ArO.. It is appeared that CuAOs could achieve stoichiometric tyrosine monooxygenation by modulating the redox potential of Cu(II) and stabilizing the ternary complex through protein conformational adjustment.
- Fu, Zhengjiang,Xu, Feng,Cai, Hu
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- A Reactive Manganese(IV)-Hydroxide Complex: A Missing Intermediate in Hydrogen Atom Transfer by High-Valent Metal-Oxo Porphyrinoid Compounds
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High-valent metal-hydroxide species are invoked as critical intermediates in both catalytic, metal-mediated O2 activation (e.g., by Fe porphyrin in Cytochrome P450) and O2 production (e.g., by the Mn cluster in Photosystem II). However, well-characterized mononuclear MIV(OH) complexes remain a rarity. Herein we describe the synthesis of MnIV(OH)(ttppc) (3) (ttppc = tris(2,4,6-triphenylphenyl) corrole), which has been characterized by X-ray diffraction (XRD). The large steric encumbrance of the ttppc ligand allowed for isolation of 3. The complexes MnV(O)(ttppc) (4) and MnIII(H2O)(ttppc) (1·H2O) were also synthesized and structurally characterized, providing a series of Mn complexes related only by the transfer of hydrogen atoms. Both 3 and 4 abstract an H atom from the O-H bond of 2,4-di-tert-butylphenol (2,4-DTBP) to give a radical coupling product in good yield (3 = 90(2)%, 4 = 91(5)%). Complex 3 reacts with 2,4-DTBP with a rate constant of k2 = 2.73(12) × 104 M-1 s-1, which is ~3 orders of magnitude larger than 4 (k2 = 17.4(1) M-1 s-1). Reaction of 3 with a series of para-substituted 2,6-di-tert-butylphenol derivatives (4-X-2,6-DTBP; X = OMe, Me, tBu, H) gives rate constants in the range k2 = 510(10)-36(1.4) M-1 s-1 and led to Hammett and Marcus plot correlations. Together with kinetic isotope effect measurements, it is concluded that O-H cleavage occurs by a concerted H atom transfer (HAT) mechanism and that the MnIV(OH) complex is a much more powerful H atom abstractor than the higher-valent MnV(O) complex, or even some FeIV(O) complexes.
- Zaragoza, Jan Paulo T.,Siegler, Maxime A.,Goldberg, David P.
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- BOX ligands in biomimetic copper-mediated dioxygen activation: A hemocyanin model
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The μ-η2:η2-peroxodicopper(II) core found in the oxy forms of the active sites of type III dicopper proteins have been a key target for bioinorganic model studies. Here, it is shown that simple bis(oxazoline)s (BOXs), which are classified among the so-called "privileged ligands", provide a suitable scaffold for supporting such biomimetic copper/dioxygen chemistry. Three derivatives R,HBOX-Me2 (R = H, Me, tBu) with different backbone substituents have been used. Their bis(oxazoline)-copper(I) complexes bind dioxygen to yield biomimetic μ-η2:η2-peroxodicopper(II) species. O2 can be reversibly released upon an increase in temperature. Their formation kinetics have been studied under cryo-stopped-flow conditions for the tBu derivative, giving activation parameters ΔH?on = (2.27 ± 0.18) kcal mol-1, ΔS?on = (-46.3 ± 0.8) cal K-1 mol-1 for the binding event and ΔH?off = (11.7 ± 1.9) kcal mol-1, ΔS?off = (-16.1 ± 8.2) cal K-1 mol-1 for the release of O2, as well as thermodynamic parameters ΔH = (-10.0 ± 1.7) kcal mol-1 and ΔS = (-32.7 ± 7.4) cal K-1 mol-1 for this equilibrium. The μ-η2:η2-peroxodicopper(II) complexes have been isolated as surprisingly stable solids and investigated in depth by a variety of methods, both in solution and in the solid state. Resonance Raman spectroscopy revealed a characteristic isotope-sensitive stretch τilde {nu}$O-O = 731-742 cm-1 (Δ[18O2] ≈ -39 cm-1) and an intense feature around 280 cm-1 diagnostic for the fundamental symmetric Cu2O2 core vibration. A slight butterfly-shape of the Cu2O2 core has been derived from EXAFS data and DFT calculations. SQUID magnetic data evidenced strong antiferromagnetic coupled CuII2 (-2J ≥ 1000 cm-1). Thermal degradation in solution yields bis(hydroxo)-bridged [(tBu,HBOX-Me2)(L)Cu(OH)]2(PF6)2 (L = H2O, MeCN or THF); whereas in the case of H,HBOX-Me2, ligand oxygenation has been detected. Preliminary reactivity studies with the substrate 2,4-di-tert-butylphenol indicate the formation of the C-C coupling product 3,3,5,5-tetra-tert-butyl-2,2-biphenol, whereas ortho-hydroxylation was not observed. The copper(I) complex [(tBu,HBOX-Me2)Cu(MeCN)]PF6 as well as two dicopper(II) complexes [(L)(tBu,HBOX-Me2)Cu(OH)]2(PF6)2 have been characterised by single-crystal X-ray diffraction. Considering the vast number of known BOX derivatives, a rich and versatile Cu/O2 chemistry based on this platform is anticipated.
- Walli, Adam,Dechert, Sebastian,Bauer, Matthias,Demeshko, Serhiy,Meyer, Franc
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- A lipophilic, fluorine-free, thermostable, inexpensive, S 4-Symmetric, highly soluble, weakly coordinating, protolabile aluminate
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This communication presents the facile and cost-effective synthesis as well as properties of salts of a lipophilic aluminate anion. Its unprecedented solubility in pentane makes possible tetrabutylammonium salt extraction with pentane. Nevertheless, its symmetry leads to high melting points of its thermostable salts. Several single crystals for X-ray diffraction studies have been obtained. The anion is devoid of halogens, but: is stable against sterically demanding electrophiles such as the trityl cation. However, it is unstable in protic media and hydrolyzes in the presence of water within days.
- Straub, Bernd F.,Wrede, Michael,Schmid, Karin,Rominger, Frank
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- Purification method of 3, 3 ', 5, 5'-tetrasubstituent-2, 2 '-biphenol
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The invention relates to the technical field of organic chemical industry, in particular to a purification method of 3, 3 ', 5, 5'-tetrasubstituent-2, 2 '-biphenol, which comprises the following steps: A) stirring and mixing 3, 3', 5, 5 '-tetrasubstituent-2, 2'-biphenol and a purifying agent to obtain a mixed material; wherein the purifying agent comprises one or more of liquid organic alcohol compounds; and B) carrying out solid-liquid separation on the mixed material, and drying the obtained solid product to obtain the purified 3, 3 ', 5, 5'-tetrasubstituent-2, 2 '-biphenol. The purification of 3, 3 ', 5, 5'-tetrasubstituent-2, 2 '-biphenol is realized under specific process steps by adopting the purifying agent with specific composition, and the method is simple in process, mild in condition, recyclable in purifying agent, low in material consumption and energy consumption, high in overall operability, capable of effectively improving the purity and appearance of the product and high in yield of the purified product.
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Paragraph 0077-0084; 0093-0108
(2021/06/23)
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- Counterion-Enhanced Pd/Enamine Catalysis: Direct Asymmetric α-Allylation of Aldehydes with Allylic Alcohols by Chiral Amines and Achiral or Racemic Phosphoric Acids
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We report a straightforward and efficient Pd/enamine catalytic procedure for the direct asymmetric α-allylation of branched aldehydes. The use of simple chiral amines and easily prepared achiral or racemic phosphoric acids, together with a suitable Pd-source resulted in a highly active and enantioselective catalyst system for the allylation of various α-branched aldehydes with different allylic alcohols. The reported procedure could provide an easy access to both product antipodes. Furthermore, two possible orthogonal derivatizations of the enantioenriched aldehydes were performed without any decrease in enantioselectivity.
- Pálv?lgyi, ádám Márk,Smith, Jakob,Schnürch, Michael,Bica-Schr?der, Katharina
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p. 850 - 860
(2021/01/09)
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- Phenol Reduces Nitrite to NO at Copper(II): Role of a Proton-Responsive Outer Coordination Sphere in Phenol Oxidation
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In the view of physiological significance, the transition-metal-mediated routes for nitrite (NO2-) to nitric oxide (NO) conversion and phenol oxidation are of prime importance. Probing the reactivity of substituted phenols toward the nitritocopper(II) cryptate complex [mC]Cu(κ2-O2N)(ClO4) (1a), this report illustrates NO release from nitrite at copper(II) following a proton-coupled electron transfer (PCET) pathway. Moreover, a different protonated state of 1a with a proton hosted in the outer coordination sphere, [mCH]Cu(κ2-O2N)(ClO4)2 (3), also reacts with substituted phenols via primary electron transfer from the phenol. Intriguingly, the alternative mechanism operative because of the presence of a proton at the remote site in 3 facilitates an unusual anaerobic pathway for phenol nitration.
- Bertke, Jeffery A.,Kundu, Subrata,Mondal, Aditesh,Reddy, Kiran P.
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supporting information
(2020/02/04)
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- Method for catalyzing oxidative coupling of 2,4-di-tert-butylphenol by means of cobalt
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The invention relates to a method for catalyzing oxidative coupling of 2,4-di-tert-butylphenol by means of cobalt to produce 2,2'-dihydroxy-3,3',5,5'-tetra-tert-butylbiphenyl. According to the method,air or oxygen is adopted as an oxidizing agent, a reaction has excellent activity and selectivity, discharge of waste liquid can be greatly reduced, and a technology process is environmentally friendly. The product 2,2'-dihydroxy-3,3',5,5'-tetra-tert-butylbiphenyl is a main raw material of production of a 2-propyl-1-heptanol catalyst ligand through hydroformylation of mixed C4, and by means of the method, the production cost of the ligand can be effectively reduced, and waste discharge can be reduced.
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Paragraph 0005; 0019-0034
(2020/02/17)
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- Method for synthesizing bisphosphite
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The invention provides a method for synthesizing bisphosphite, comprising the following steps: 1) carrying out an oxidative coupling reaction on phenol as shown in a general formula (I) under the action of a supported copper-based catalyst to obtain diphenol as shown in a general formula (II); 2) carrying out a reaction between the diphenol shown in the general formula (III) and phosphorus trichloride to obtain biphenoxy phosphine chloride as shown in the general formula (IV); and 3) carrying out a reaction between the diphenol represented by the general formula (II) and biphenyl oxyphosphinechloride as shown in the general formula (IV) to obtain bisphosphite as shown in the general formula (V). In the general formulas (I), (II), (III), (IV) and (V), X1, X2, Y1, Y2, Z1 and Z2 are independently hydrogen, C1-6 alkyl or C1-6 alkoxy.
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Paragraph 0069; 0071; 0075; 0076
(2020/06/02)
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- Phosphine ligand compound and preparation method thereof, catalyst composition and application thereof, and vinyl acetate hydroformylation method
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The invention relates to the field of vinyl acetate hydroformylation, and discloses a phosphine ligand compound and a preparation method thereof, a catalyst composition and application thereof, and avinyl acetate hydroformylation method. The phosphine ligand compound has a structure shown as a formula (1); wherein A is selected from a substituted or unsubstituted C1-C20 alkylene group; B1 and B2are each independently selected from a substituted or unsubstituted biphenyl group; substituent groups optionally existing in A, B1 and B2 are respectively and independently selected from at least oneof C1-C20 alkyl, halogen, C1-C10 alkoxyl, hydroxyl, carboxyl and aldehyde group; and the provided phosphine ligand compound can effectively improve the conversion rate of vinyl acetate and the selectivity of 2-acetoxy propionaldehyde.
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Paragraph 0078-0087
(2020/07/13)
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- Phosphine ligand compound and preparation method thereof, catalyst composition and application thereof, and vinyl acetate hydroformylation method
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The invention relates to the field of vinyl acetate hydroformylation, and discloses a phosphine ligand compound and a preparation method thereof, a catalyst composition and application thereof, and avinyl acetate hydroformylation method. The phosphine ligand compound has a structure shown as a formula (1); wherein A is selected from substituted or unsubstituted phenyl and substituted or unsubstituted biphenyl; B1 and B2 are each independently selected from a substituted or unsubstituted biphenyl group; substituent groups optionally existing in A, B1 and B2 are respectively and independently selected from at least one of C1-C20 alkyl, halogen, C1-C10 alkoxyl, hydroxyl, carboxyl and aldehyde group; and the provided phosphine ligand compound can effectively improve the conversion rate of vinyl acetate and the selectivity of 2-acetoxy propionaldehyde.
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Paragraph 0078-0083
(2020/07/13)
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- Phosphine ligand compound and preparation method thereof, catalyst composition and application thereof, and vinyl acetate hydroformylation method
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The invention relates to the field of vinyl acetate hydroformylation, and discloses a phosphine ligand compound and a preparation method thereof, a catalyst composition and application thereof, and avinyl acetate hydroformylation method. The phosphine ligand compound has a structure shown as a formula (1); wherein A is selected from substituted or unsubstituted biphenyl; B1 and B2 are each independently selected from substituted or unsubstituted C1-C20 alkylene groups; substituent groups optionally existing in A, B1 and B2 are respectively and independently selected from at least one of C1-C20 alkyl, halogen, C1-C10 alkoxyl, hydroxyl, carboxyl and aldehyde group; and the provided phosphine ligand compound can effectively improve the conversion rate of vinyl acetate and the selectivity of2-acetoxy propionaldehyde.
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Paragraph 0081-0086
(2020/07/13)
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- Oxidative photocatalytic homo- And cross-coupling of phenols: Nonenzymatic, catalytic method for coupling tyrosine
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An oxidative photocatalytic method for phenol? phenol homo- and cross-coupling is described, and isolated yields of 16?97% are obtained. Measured oxidation potentials and computed nucleophilicity parameters support a mechanism of nucleophilic attack of one partner onto the oxidized neutral radical form of the other partner. Our understanding of this model permitted the development of cross-coupling reactions between nucleophilic phenols/arenes and easily oxidized phenols with high selectivity and efficiency. A highlight of this method is that one equivalent of each coupling partner is utilized. Building on these findings, a nonenzymatic, catalytic method for coupling tyrosine was also developed.
- Niederer, Kyle A.,Gilmartin, Philip H.,Kozlowski, Marisa C.
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p. 14615 - 14623
(2020/12/23)
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- Solid-Phase ortho-Hydroxylation of 2,4-Di-tert-butylphenol and Its Derivatives
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Abstract: Direct phenol–catechol conversion has been realized as a result of the solid-phase reaction of 2,4-di-tert-butylphenol with cuprous oxide under high pressure and shear deformation on the Bridgman anvils. The yield of 3,5-di-tert-butylcatechol in this reaction was about 85%. When cupric oxide was used in the solid-phase process, oxidative coupling of the starting phenol took place, resulting in quantitative formation of tetra-tert-butyl-ortho-bisphenol. The reaction of 6-substituted derivatives of 2,4-di-tert-butylphenol with cuprous oxide was used as an example to demonstrate the possibility of substitutive ortho-hydroxylation yielding 7–20% of pyrocatechols.
- Kurkovskaya, L. N.,Ovsyannikova, M. N.,Vol’eva, V. B.,Zhorin, V. A.
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p. 350 - 352
(2020/04/21)
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- Nitric Oxide Dioxygenase Activity of a Nitrosyl Complex of Mn(II)-Porphyrinate in the Presence of Superoxide: Formation of a Mn(IV)-oxo Species through a Putative Peroxynitrite Intermediate
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A nitrosyl complex of MnII-porphyrinate, [(F20TPP)MnII(NO)], 1 (F20TPPH2 = 5,10,15,20 tetrakis(pentafluorophenyl)porphyrin), was synthesized and characterized. Spectroscopic and structural characterization revealed complex 1 as a penta-coordinated MnII-nitrosyl with a linear Mn-N-O (180.0°) moiety. Complex 1 does not react with O2. However, it reacts with superoxide (O2 -) in THF at -80 °C to result in the corresponding nitrate (NO3 -) complex, 2, via the formation of a presumed MnIII-peroxynitrite intermediate. ESI-mass spectrometry and UV-visible and X-band EPR spectroscopic studies suggest the generation of MnIV-oxo species in the reaction through homolytic cleavage of the O-O bond of the peroxynitrite ligand as proposed in NOD activity. The intermediate formation of the MnIII-peroxynitrite was further supported by the well accepted phenol ring nitration which resembles the biologically well-established tyrosine nitration.
- Mondal, Baishakhi,Borah, Dibyajyoti,Mazumdar, Rakesh,Mondal, Biplab
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p. 14701 - 14707
(2019/11/03)
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- Finding a new pathway for acid-induced nitrite reduction reaction: Formation of nitric oxide with hydrogen peroxide
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Here, we report a new pathway for nitrite reduction chemistry, formation of cobalt-nitrosyl ({CoII-NO}8) with H2O2 in the reaction of a CoII-nitrito complex with a one-fold acid (H+) via the formation of a CoII-nitrous acid intermediate ({CoII-ONOH}). Mechanistic investigations using 15N-labeled-15NO2- revealed that the N-atom in the {CoII-NO}8 complex is derived from the nitrito ligand, and H2O2 came from the homolysis of the ON-OH moiety. Spectral evidence supporting the formation of the CoII-ONOH intermediate and the generation of H2O2 is also presented.
- Puthiyaveetil Yoosaf, Mohammed Ajmal,Ghosh, Somnath,Narayan, Yatheesh,Yadav, Munendra,Sahoo, Subash Chandra,Kumar, Pankaj
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supporting information
p. 13916 - 13920
(2019/10/02)
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- Catalytic Aerobic Phenol Homo- and Cross-Coupling Reactions with Copper Complexes Bearing Redox-Active Guanidine Ligands
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Due to their large importance in synthetic chemistry, catalytic C?C coupling reactions of phenols are currently intensively studied. Herein, new copper catalysts for the C?C coupling reaction of phenols using dioxygen as a green oxidizing reagent are reported. By using redox-active guanidine ligands, the activity as well as chemoselectivity in the cross-coupling reaction of non-complementary phenols (between an electron-rich phenol and a less nucleophilic second phenol) is significantly improved. Based on the collected data for several test reactions, a reaction mechanism is proposed.
- Sch?n, Florian,Kaifer, Elisabeth,Himmel, Hans-J?rg
-
supporting information
p. 8279 - 8288
(2019/06/04)
-
- Employing Linear Tridentate Ligands with Pyrazole End Groups in Catalytic Tyrosinase Model Chemistry: Does Hemilability Matter?
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Several copper(I) and copper(II) complexes supported by hemilabile bis(pyrazolylmethyl)amine (pzma) ligands are synthesized and structurally characterized. The copper(I) complexes with hexafluoridophosphate or perchlorate anions are employed as catalysts for the tyrosinase-like oxygenation of 2,4-di-tert-butylphenol (DTBP-H). Their activities are comparable to that of [Cu(MeCN)2PMP]PF6 (PMP= pyrazolylmethylpyridine) investigated earlier. In contrast to the copper(I) pzma complexes, their congeners supported by non-hemilabile bis(pyrazolylethyl)amine (pzea) ligands are found to be catalytically inactive.
- Herzigkeit, Benjamin,Jurgeleit, Ramona,Fl?ser, Benedikt M.,Mei?ner, Nadja E.,Engesser, Tobias A.,N?ther, Christian,Tuczek, Felix
-
supporting information
p. 2258 - 2266
(2019/05/01)
-
- Stabilizing Terminal Ni(III)-Hydroxide Complex Using NNN-Pincer Ligands: Synthesis and Characterization
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The reaction of [Ni(COD)2] (COD; cyclooctadiene) in THF with the NNN-pincer ligand bis(imino)pyridyl (L1) reveals a susceptibility to oxidation in an inert atmosphere ([O2] level III(L1··)2-(OH)] (1). Various isotopically labeled experiments (16O/18O) assertively endorse the origin of terminal oxygen based ligand in 1 due to the activation of molecular dioxygen. The presence of proton bound to the terminal oxygen in 1 is well supported by NMR, IR spectroscopy, DFT calculations, and hydrogen atom transfer (HAT) reactions promoted by 1. The observation of shakeup satellite peaks for the primary photoelectron lines of Ni(2p) in the X-ray photoelectron spectroscopy (XPS) unambiguously confirms the paramagnetic signature associated with the distorted square planar nickel ion, which is consistent with the trivalent oxidation state assigned for the nickel ion in 1. The variable temperature magnetic susceptibility data of 1 shows dominant antiferromagnetic interactions exist among the paramagnetic centers, resulting in an overall S = 1/2 ground state. Variable temperature X-band EPR studies performed on 1 show evidence for the S = 1/2 ground state, which is consistent with magnetic data. The unusual g-tensor extracted for the ground state S = 1/2 is analyzed under a strong exchange limit of spin-coupled centers. The electronic structure predicted for 1 is in good agreement with theoretical calculations.
- Shanmugam, Maheswaran,Rajpurohit, Jitendrasingh,Shukla, Pragya,Kumar, Pardeep,Das, Chinmoy,Vaidya, Shefali,Sundararajan, Mahesh,Shanmugam, Muralidharan
-
p. 6257 - 6267
(2019/05/08)
-
- Hydrogen Atom Abstraction by High-Valent Fe(OH) versus Mn(OH) Porphyrinoid Complexes: Mechanistic Insights from Experimental and Computational Studies
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High-valent metal-hydroxide species have been implicated as key intermediates in hydroxylation chemistry catalyzed by heme monooxygenases such as the cytochrome P450s. However, in some classes of P450s, a bifurcation from the typical oxygen rebound pathway is observed, wherein the FeIV(OH)(porphyrin) species carries out a net hydrogen atom transfer reaction to form alkene metabolites. In this work, we examine the hydrogen atom transfer (HAT) reactivity of FeIV(OH)(ttppc) (1), ttppc = 5,10,15-tris(2,4,6-triphenyl)-phenyl corrole, toward substituted phenol derivatives. The iron hydroxide complex 1 reacts with a series of para-substituted 2,6-di-tert-butylphenol derivatives (4-X-2,6-DTBP; X = OMe, Me, Et, H, Ac), with second-order rate constants k2 = 3.6(1)-1.21(3) × 104 M-1 s-1 and yielding linear Hammett and Marcus plot correlations. It is concluded that the rate-determining step for O-H cleavage occurs through a concerted HAT mechanism, based on mechanistic analyses that include a KIE = 2.9(1) and DFT calculations. Comparison of the HAT reactivity of 1 to the analogous Mn complex, MnIV(OH)(ttppc), where only the central metal ion is different, indicates a faster HAT reaction and a steeper Hammett slope for 1. The O-H bond dissociation energy (BDE) of the MIII(HO-H) complexes were estimated from a kinetic analysis to be 85 and 89 kcal mol-1 for Mn and Fe, respectively. These estimated BDEs are closely reproduced by DFT calculations and are discussed in the context of how they influence the overall H atom transfer reactivity.
- Zaragoza, Jan Paulo T.,Cummins, Daniel C.,Mubarak, M. Qadri E.,Siegler, Maxime A.,De Visser, Sam P.,Goldberg, David P.
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p. 16761 - 16770
(2019/12/24)
-
- Generation and Reactivity of a One-Electron-Oxidized Manganese(V) Imido Complex with a Tetraamido Macrocyclic Ligand
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The synthesis and X-ray structure of a new manganese(V) mesitylimido complex with a tetraamido macrocyclic ligand (TAML), [MnV(TAML)(N-Mes)]? (1), are reported. Compound 1 is oxidized by [(p-BrC6H4)3N]+.[SbCl6]? and the resulting MnVI species readily undergoes H-atom transfer and nitrene transfer reactions.
- Shi, Huatian,Xie, Jianhui,Lam, William W. Y.,Man, Wai-Lun,Mak, Chi-Keung,Yiu, Shek-Man,Lee, Hung Kay,Lau, Tai-Chu
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p. 12895 - 12899
(2019/09/13)
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- Development of the radical C–O coupling reaction of phenols toward the synthesis of natural products comprising a diaryl ether skeleton
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Compounds comprising a diaryl ether skeleton exist among natural phenols. The diaryl ether skeleton is thought to be biosynthesized through the coupling of two or more phenols. It is an important structural feature in medicines and agrochemicals, and it is imperative to develop methods for constructing such skeletons in organic synthesis. However, by the synthesis method through the coupling of phenols, coupling occurs preferentially at the ortho-substituted carbon atom of phenols. In this study, various radical-generating reagents and conditions were investigated with the aim of developing a short-step construction method of the diaryl ether skeleton by the radical homo-coupling of two phenol molecules. In addition, cross-coupling reactions between radicals of 2,4,6-tri-tert-butylphenol and p-substituted phenol were conducted to synthesize eight C (ortho)–O coupling products. Based on the results, a computational chemical approach was employed to verify the cause of C (ortho)–O bond formation.
- Tanaka, Kumpei,Gotoh, Hiroaki
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p. 3875 - 3885
(2019/06/18)
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- Tyrosinase Model Systems Supported by Pyrazolylmethylpyridine Ligands: Electronic and Steric Factors Influencing the Catalytic Activity and Impact of Complex Equilibria in Solution
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Two new copper(I) complexes supported by pyrazolylmethylpyridine (PMP) ligands are synthesized and investigated regarding their ability to catalyze the oxygenation of several monophenolic substrates. The PMP ligands containing a pyridine and a pyrazole donor group represent hybrids between dipyridylmethane (DPM) and bis(pyrazolyl)methane (BPM) ligands. The catalytic activity of the two new [Cu(MeCN)2PMP]PF6 complexes is found to be intermediate between that of catalytically inactive [Cu(MeCN)2DPM]PF6 and highly active [Cu(MeCN)2BPM]PF6, suggesting that the electronic properties of a multidentate ligand can be designed in a modular fashion. DFT calculations are used to explore the differences in reactivity between the two systems. Regarding the behavior of these complexes in solution, evidence for an equilibrium between homoleptic and heteroleptic forms is presented. The crystal structure of a dinuclear complex exhibiting two homoleptic CuII units bridged by a fluorido ligand is obtained, which might represent one of the decay products of PMP-type catalysts after prolonged reaction times.
- Herzigkeit, Benjamin,Fl?ser, Benedikt M.,Engesser, Tobias A.,N?ther, Christian,Tuczek, Felix
-
supporting information
p. 3058 - 3069
(2018/07/29)
-
- Click. Coordinate. Catalyze. Using CuAAC Click Ligands in Small-Molecule Model Chemistry of Tyrosinase
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Three triazolylmethylpyridine ligands are synthesized using the copper-catalyzed azide-alkyne cycloaddition (CuAAC). The corresponding copper(I) complexes are investigated as catalysts for the oxygenation of several monophenols, in analogy to the enzyme tyrosinase. Importantly, they show a higher catalytic activity than previously investigated systems. This is ascribed to the lower charge donation of the electron-poor triazole heterocycle, supporting the hydroxylation of phenolic substrates by an electrophilic substitution mechanism.
- Herzigkeit, Benjamin,Fl?ser, Benedikt M.,Mei?ner, Nadja E.,Engesser, Tobias A.,Tuczek, Felix
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p. 5402 - 5405
(2018/11/27)
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- A Mononuclear Non-heme Manganese(III)-Aqua Complex as a New Active Oxidant in Hydrogen Atom Transfer Reactions
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A mononuclear non-heme Mn(III)-aqua complex, [(dpaq)MnIII(OH2)]2+ (1, dpaq = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate), is capable of conducting hydrogen atom transfer (HAT) reactions much more efficiently than the corresponding Mn(III)-hydroxo complex, [(dpaq)MnIII(OH)]+ (2); the high reactivity of 1 results from the positive one-electron reduction potential of 1 (Ered vs SCE = 1.03 V), compared to that of 2 (Ered vs SCE = -0.1 V). The HAT mechanism of 1 varies between electron transfer followed by proton transfer and one-step concerted proton-coupled electron transfer, depending on the one-electron oxidation potentials of substrates. To the best of our knowledge, this is the first example showing that metal(III)-aqua complex can be an effective H-atom abstraction reagent.
- Sankaralingam, Muniyandi,Lee, Yong-Min,Karmalkar, Deepika G.,Nam, Wonwoo,Fukuzumi, Shunichi
-
supporting information
p. 12695 - 12699
(2018/10/20)
-
- Green production process of biphenol from 2,4-disubstituted phenol
-
The invention discloses a green production process of biphenol from 2,4-disubstituted phenol. The green production process includes the steps of: with the 2,4-disubstituted phenol (I) as a raw material and water as a solvent, performing an oxidizing coupling reaction at certain temperature to generate 2,2'-biphenol (II) with H2O2 as an oxidant under the effect of a catalyst, wherein an emulsifier and a pH conditioner are added; when the reaction is finished, centrifuging and purifying the reaction product to obtain the biphenol (II) being 99% in content. The process is green and environment-friendly, is safe, economical and effective, has mild reaction conditions and simple post-treatment process, is easy to achieve in industrial production, has good product appearance and is high in yield.
- -
-
Paragraph 0019; 0021; 0022; 0023; 0024
(2017/08/30)
-
- A New Domain of Reactivity for High-Valent Dinuclear [M(μ-O)2M′] Complexes in Oxidation Reactions
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The strikingly different reactivity of a series of homo- and heterodinuclear [(MIII)(μ-O)2(MIII)′]2+(M=Ni; M′=Fe, Co, Ni and M=M′=Co) complexes with β-diketiminate ligands in electrophilic and nucleophilic oxidation reactions is reported, and can be correlated to the spectroscopic features of the [(MIII)(μ-O)2(MIII)′]2+core. In particular, the unprecedented nucleophilic reactivity of the symmetric [NiIII(μ-O)2NiIII]2+complex and the decay of the asymmetric [NiIII(μ-O)2CoIII]2+core through aromatic hydroxylation reactions represent a new domain for high-valent bis(μ-oxido)dimetal reactivity.
- Engelmann, Xenia,Yao, Shenglai,Farquhar, Erik R.,Szilvási, Tibor,Kuhlmann, Uwe,Hildebrandt, Peter,Driess, Matthias,Ray, Kallol
-
supporting information
p. 297 - 301
(2016/12/30)
-
- Oxidation of Organic Molecules with a Redox-Active Guanidine Catalyst
-
Herein, we report the first examples of the use of redox-active guanidines as catalysts in the green oxidation of organic molecules with dioxygen. In one half-reaction, the oxidized form of the redox-active guanidine is converted into the reduced, protonated state, thereby enabling dehydrogenative oxidation of the substrate (3,5-di-tert-butylcatechol→ortho-benzoquinone, benzoin→benzil, and 2,4-di-tert-butylphenol→biphenol). In the other half-reaction, efficient re-oxidation of the guanidine to the oxidized state is achieved with dioxygen in the presence of a copper catalyst. These results pave the way for the broader use of redox-active guanidines as oxidation catalysts.
- Wild, Ute,Sch?n, Florian,Himmel, Hans-J?rg
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p. 16410 - 16413
(2017/11/27)
-
- Synthesis method and application of hindered phenol antioxidant
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The invention discloses a synthesis method and application of a hindered phenol antioxidant. The synthesis method comprises the steps of synthesizing a hindered phenol antioxidant 3,3',5,5'-tetra-tert-butyl-2,2'-biphenol by taking 2,4-ditert-butyl phenol as a raw material and copper chloride and tetramethylethylenediamine as catalysts, and synthesizing another hindered phenol antioxidant 5,5'-ditert-butyl-2,2'-biphenol by taking the hindered phenol antioxidant 3,3',5,5'-tetra-tert-butyl-2,2'-biphenol as the raw material and aluminum chloride and nitromethane as catalysts. The protection performance of the two hindered phenol antioxidants as antiagers is put forward for the first time, and the hindered phenol antioxidants are applicable to natural rubber.
- -
-
Paragraph 0037; 0038
(2017/06/02)
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- HETEROCYCLIC SELENABISPHOSPHITES AND PROCESS FOR PREPARATION THEREOF
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Novel heterocyclic selenabisphosphites, process for preparation thereof and use thereof as ligand unit for preparing ligands for use in complexes.
- -
-
Paragraph 0122; 0123; 0124
(2017/09/02)
-
- Reactivity of a stable copper-dioxygen complex
-
We report the isolation of a room temperature stable dipyrromethene Cu(O2) complex featuring a side-on O2 coordination. Reactivity studies highlight the unique ability of the dioxygen adduct for both hydrogen-atom abstraction and acid/base chemistry towards phenols, demonstrating that side-on superoxide species can be reactive entities.
- Iovan, Diana A.,Wrobel, Alexandra T.,McClelland, Arthur A.,Scharf, Austin B.,Edouard, Guy A.,Betley, Theodore A.
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supporting information
p. 10306 - 10309
(2017/09/23)
-
- Synthesis and Catalytic Reactivity of a Dicopper(II) μ-η2:η2-Peroxo Species Supported by 1,4,7-Tri-tert-butyl-1,4,7-triazacyclononane
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O2-derived CunO2 adducts are attractive targets for aerobic oxidation catalysis because of their remarkable reactivity, but oxidation of the supporting ligand limits catalytic turnover. We report that tBu3tacn (1,4,7-tri-tert-butyl-1,4,7-triazacyclononane) supports a dicopper(II) μ-η2:η2-peroxo species with the highest solution stability outside of an enzyme. Decomposition of this species proceeds without oxidation of the tBu3tacn ligand. Additive-free catalytic aerobic oxidation reactions at or above room temperature are described, highlighting the potential of oxidatively robust ligands in aerobic copper catalysis.
- Karahalis, Gregory J.,Thangavel, Arumugam,Chica, Bryant,Bacsa, John,Dyer, R. Brian,Scarborough, Christopher C.
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p. 1102 - 1107
(2016/02/09)
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- A cobalt compound, preparation method and its use
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The invention provides a cobalt complex, a preparation method and an application thereof, and belongs to the technical field of metal-organic complex materials. The cobalt complex has a molecular formula of [Co(qc)2(H2O)].2H2O, wherein qc represents 3-hydroxyl-2-quinoxaline carboxylate radicals. The invention also provides a method for preparing the cobalt complex. The cobalt complex is obtained by reacting 3-hydroxyl-2-quinoxaline carboxylic acid and a bivalent cobalt compound in a solution. The invention also provides an application of the cobalt complex in catalyzing an oxidative coupling reaction of 2,4-di-tert-butylphenol. The cobalt complex provided by the invention has a certain granularity and a unique structure, and has relatively high catalytic activity, selectivity and good stability. The preparation method of the cobalt complex is simple, has high yield and has no pollution to the environment. By using the cobalt complex to prepare biphenol, water can be used as a solvent; selectivity is good; yield is high; three wastes are little; and the product is free from pollution.
- -
-
Paragraph 0041; 0042
(2017/03/21)
-
- Preparation method of novel bidentate phosphite ligand and application thereof in Buchwald-Hartwig reaction
-
The invention discloses a preparation method of novel bidentate phosphite ligands and application thereof in Buchwald-Hartwig reaction and belongs to the field of organic synthetic chemistry. A series of novel bidentate phosphite ligands are synthesized by using 3,3',5,5'-tetra-tert-butyl-2,2'-dihydroxyl diphenyl and glycols with different structures as raw materials through a two-step one-pot method, are compounds very wide in application range and have the following structures. The novel preparation method has the advantages of being stable in structure, simple and convenient to synthesize, high in yield and easy to prepare in a large-scale mode. The ligands have higher reaction activity and substrate universality in the Pd catalyzed Buchwald-Hartwig reaction.
- -
-
Paragraph 0028; 0029; 0030
(2016/10/09)
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- Solvent-Dependent Facile Synthesis of Diaryl Selenides and Biphenols Employing Selenium Dioxide
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Biphenols are important structure motifs for ligand systems in organic catalysis and are therefore included in the category of so-called "privileged ligands". We have developed a new synthetic pathway to construct these structures by the use of selenium dioxide, a stable, powerful, and commercially available oxidizer. Our new, and easy to perform protocol gives rise to biphenols and diaryl selenides depending on the solvent employed. Oxidative treatment of phenols in acetic acid yields the corresponding biphenols, whereas conversion in pyridine results in the preferred formation of diaryl selenides. As a consequence, we were able to isolate a broad scope of novel diaryl selenides, which could act as pincer-like ligands with further applications in organic synthesis or as ligands in transition metal catalysis.
- Quell, Thomas,Mirion, Michael,Schollmeyer, Dieter,Dyballa, Katrin M.,Franke, Robert,Waldvogel, Siegfried R.
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p. 115 - 119
(2016/05/02)
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- Industrialized synthesis method of high-purity biphenyl diphenol compound
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The invention discloses an industrialized synthesis method of a high-purity biphenyl diphenol compound. The synthesis method comprises the steps that a phenolic compound A of which the ortho-position or para-position is a hydrogen atom serves as the raw material, alkali metal hydroxide or alkaline earth metal hydroxide or weak-acid alkali metal salt serves as a catalyst, different phenolic compounds are added to serve as oxidation regulators, all the substances are mixed and heated to 65 DEG C-185 DEG C, and meanwhile oxygen or air is blown into the mixture for an oxidation coupling reaction; after the PH value of the reaction system is adjusted through an acidic substance, a disproportionated reaction is conducted in an inert gas environment at the temperature ranging from 65 DEG C to 245 DEG C, and the high-purity biphenyl diphenol compound B or C is obtained. According to the preparation method of the high-purity biphenyl diphenol compound, the steps are simple, the reaction conditions are mild, the cost is low, the reaction materials can be recycled, the product is good in color, the product purity reaches up to 99.9 percent, and the preparation method is very suitable for industrialized production.
- -
-
Paragraph 0025; 0026
(2016/11/14)
-
- Tuning the Reactivity of Terminal Nickel(III)-Oxygen Adducts for C-H Bond Activation
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Two metastable NiIII complexes, [NiIII(OAc)(L)] and [NiIII(ONO2)(L)] (L = N,N′-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate, OAc = acetate), were prepared, adding to the previously prepared [NiIII(OCO2H)(L)], with the purpose of probing the properties of terminal late-transition metal oxidants. These high-valent oxidants were prepared by the one-electron oxidation of their NiII precursors ([NiII(OAc)(L)]- and [NiII(ONO2)(L)]-) with tris(4-bromophenyl)ammoniumyl hexachloroantimonate. Fascinatingly, the reaction between any [NiII(X)(L)]- and NaOCl/acetic acid (AcOH) or cerium ammonium nitrate ((NH4)2[CeIV(NO3)6], CAN), yielded [NiIII(OAc)(L)] and [NiIII(ONO2)(L)], respectively. An array of spectroscopic characterizations (electronic absorption, electron paramagnetic resonance, X-ray absorption spectroscopies), electrochemical methods, and computational predictions (density functional theory) have been used to determine the structural, electronic, and magnetic properties of these highly reactive metastable oxidants. The NiIII-oxidants proved competent in the oxidation of phenols (weak O-H bonds) and a series of hydrocarbon substrates (some with strong C-H bonds). Kinetic investigation of the reactions with di-tert-butylphenols showed a 15-fold enhanced reaction rate for [NiIII(ONO2)(L)] compared to [NiIII(OCO2H)(L)] and [NiIII(OAc)(L)], demonstrating the effect of electron-deficiency of the O-ligand on oxidizing power. The oxidation of a series of hydrocarbons by [NiIII(OAc)(L)] was further examined. A linear correlation between the rate constant and the bond dissociation energy of the C-H bonds in the substrates was indicative of a hydrogen atom transfer mechanism. The reaction rate with dihydroanthracene (k2 = 8.1 M-1 s-1) compared favorably with the most reactive high-valent metal-oxidants, and showcases the exceptional reactivity of late transition metal-oxygen adducts.
- Pirovano, Paolo,Farquhar, Erik R.,Swart, Marcel,McDonald, Aidan R.
-
supporting information
p. 14362 - 14370
(2016/11/13)
-
- Industrial preparation method of biphenol compounds with high purity
-
The invention discloses an industrial preparation method of biphenol compounds with high purity. The preparation method comprises the following steps: (1) a phenolic compound A containing a tert-butyl group whose ortho-position or para-position is a hydrogen atom is used as a raw material, an oxidative coupling reaction and a disproportionation reaction are carried out, and a tert-butyl-containing 4,4'-biphenol or 2,2'-biphenol compound is obtained; (2) a de-tert-butylation reaction is carried out for the tert-butyl-containing 4,4'-biphenol or 2,2'-biphenol compound at 100-220 DEG C with a strongly acidic catalyst in phenols or aliphatic solvents with high-boiling point, and a 4,4'-biphenol compound B or a 2,2'-biphenol compound C with high-purity is obtained. The preparation method of the 4,4'-biphenol or 2,2'-biphenol compound has the advantages of simple steps, mild reaction condition, low cost, cyclic utilization of reaction raw materials, excellent color of the product and high yield; the purity of the product reaches 99.9%, and the method is suitable for industrial production.
- -
-
Paragraph 0026-0027
(2017/03/14)
-
- A Peroxynitrite Dicopper Complex: Formation via Cu-NO and Cu-O2 Intermediates and Reactivity via O-O Cleavage Chemistry
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A mixed-valent Cu(I)Cu(II) complex, [CuI,II2(UN-O-)]2+ (1), reacts with NO(g) at -80 °C to form [CuI,II2(UN-O-)(NO)]2+ (2), best described as a mixed-valent nitrosyl complex that has a ?(N-O) band at 1670 cm-1 in its infrared (IR) spectrum. Complex 2 undertakes a one-electron oxidation via the addition of O2(g) to generate a new intermediate, best described as a superoxide and nitrosyl adduct, [CuII2(UN-O-)(NO)(O2-)]2+ (3), based on its distinctively blue-shifted ?(N-O) band at 1853 cm-1. Over the course of 20 min at -80 °C, 3 is converted to the peroxynitrite (PN) complex [CuII2(UN-O-)(-OON=O)]2+ (4), which was characterized by low-temperature electrospray ionization mass spectrometry (ESI-MS) and IR spectroscopy; ?(N-O) absorptions at 1520 and 1640 cm-1 have been assigned as cis- and trans-conformers of the PN ligand in 4. Alternatively, the superoxide complex [CuII2(UN-O-)(O2?-)]2+ (5) is found to react with NO(g) to generate the same intermediate superoxide and nitrosyl adduct 3 (based on IR criteria), which likewise converts to the same PN complex 4. The O-O bond in 4 undergoes heterolysis in dichloromethane solvent and is postulated to produce nitronium ion, leading to ortho-nitration of 2,4-di-tert-butylphenol (DTBP). However, in 2-methyltetrahydrofuran as solvent, the O-O bond undergoes homolysis to generate ?NO2 (detected spectrophotometrically) and a putative higher-valent complex, [CuII,III2(UN-O-)(O2-)]2+, that abstracts a H-atom from DTBP to give [CuII2(UN-O-)(OH)]2+ and a phenoxyl radical. The latter may dimerize to form the bis-phenol observed experimentally or couple with the ?NO2 present, leading to o-phenol nitration.
- Cao, Rui,Elrod, Lee Taylor,Lehane, Ryan L.,Kim, Eunsuk,Karlin, Kenneth D.
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p. 16148 - 16158
(2016/12/24)
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- Changing the chemical and physical properties of high valent heterobimetallic bis-(μ-oxido) Cu-Ni complexes by ligand effects
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Two new heterobimetallic [LNiO2Cu(RPY2)]+ (RPY2 = N-substituted bis 2-pyridyl(ethylamine) ligands with R = indane, 3a or R = Me, 3b) complexes have been spectroscopically trapped at low temperatures. They were prepared by reacting the mononuclear side-on LNiII superoxo precursor bearing a β-diketiminate ligand (L = [HC-(CMeNC6H3(iPr)2)2]) with the Cu(i) complexes. In contrast to the oxo groups in known high-valent [M2(μ-O)2]n+ (M = Fe, Co, Ni, Cu) cores that display electrophilic reactivities, 3a and 3b display rather nucleophilic oxo cores active in aldehyde deformylation reactions. However, the spectroscopic and reactivity properties of 3a/3b are found to be distinct relative to that of the previously reported [LNiO2Cu(MeAN)]+ complex containing a more basic (nucleophilic) N,N,N′,N′,N′-pentamethyl-dipropylenetriamine (MeAN) ligand at the copper centre. The geometry and electronic properties of the copper ligands affect the electron density of the oxygen atoms of the heterodinuclear {Ni(μ-O)2} core and 3a/3b undergo slower nucleophilic and faster electrophilic reactions than the previously reported [LNiO2Cu(MeAN)]+ intermediate. The present study therefore demonstrates the tuning of the electrophilicity/nucleophilicity of the oxygen atoms of the heterobimetallic [Ni(μ-O)2Cu]2+ cores by controlling the electron donation from the ancillary ligands, and underlines the significance of subtle electronic changes in the physical and chemical properties of the biologically relevant heterobimetallic metal-dioxygen intermediates.
- Kafentzi, Maria-Chrysanthi,Orio, Maylis,Réglier, Marius,Yao, Shenglai,Kuhlmann, Uwe,Hildebrandt, Peter,Driess, Matthias,Simaan, A. Jalila,Ray, Kallol
-
supporting information
p. 15994 - 16000
(2016/10/22)
-
- Facile and Selective Cross-Coupling of Phenols Using Selenium Dioxide
-
Nonsymmetric biphenols are important structural motifs in organic chemistry. Therefore, an easy and versatile protocol for oxidative cross-coupling is essential to generate these so-called “privileged ligands”. We developed an efficient and selective oxidative pathway to synthesize 2,2′-biphenols as well as 2,4′- and 4,4′-biphenols. The use of selenium dioxide, a stable, powerful, and commercially available oxidizer, in 1,1,1,3,3,3-hexafluoroisopropanol allowed the oxidative coupling of alkyl-, alkoxy-, and halogen-substituted phenols.
- Quell, Thomas,Beiser, Nicole,Dyballa, Katrin M.,Franke, Robert,Waldvogel, Siegfried R.
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supporting information
p. 4307 - 4310
(2016/09/13)
-
- PROCESS FOR PREPARING 2,2'-SELENOBIARYL ETHERS OR 4,4'-SELENOBIARYL ETHERS USING SELENIUM DIOXIDE
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A process for preparing a 2,2′-selenobiaryl ether or a 4,4′-selenobiaryl ether, proceeds by a) adding a first phenol to the reaction mixture, b) adding a second phenol to the reaction mixture, c) adding selenium dioxide to the reaction mixture, d) adding a base having a pKb in the range from 8 to 11 to the reaction mixture, and e) adjusting the reaction temperature of the reaction mixture such that the first phenol and the second phenol are converted to said 2,2′-selenobiaryl ether or said 4,4′-selenobiaryl ether.
- -
-
Paragraph 0149; 0150; 0180-0185; 0221
(2015/12/05)
-
- Bioinspired copper(I) complexes that exhibit monooxygenase and catechol dioxygenase activity
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New tripodal ligand L2 featuring three different pyridyl/imidazolyl-based N-donor units at a bridgehead C atom, from which one of the imidazolyl units is separated by a phenylene linker, was synthesized and investigated with regards to copper(I) complexation. The resulting complex [(L2)Cu]OTf (2OTf), the known complex [(L1)Cu]OTf (1OTf; L1 differs from L2 in that it lacks the phenylene spacer) and [(L3)Cu]OTf (3OTf), prepared from a known chiral, tripodal, N-donor ligand featuring pyridyl, pyrazolyl, and imidazolyl donors, were tested as catalysts for the oxidation of sodium 2,4-di-tert-butylphenolate (NaDTBP) with O2. Indeed, they mediated NaDTBP oxidation to give mainly the corresponding catecholate and quinone (Q). None of the complexes 1OTf, 2OTf, and 3OTf is superior to the others, as yields were comparable and, if the presence of protons is guaranteed by concomitant addition of the phenol DTBP, the oxidation can also be performed catalytically. For all complexes stoichiometric oxidations under certain conditions (concentrated solutions, high NaDTBP content) were found to also generate products typical for metal-mediated intradiol cleavage of the catecholate with O2. As shown representatively for 1OTf this dioxygenation sets in at a later stage of the reaction. Initially a copper species responsible for the monooxygenation must form from 1OTf/NaDTBP/O2, and only thereafter is the copper species responsible for dioxygenation formed and consumes Q as substrate. Hence, under these circumstances complexes 1OTf-3OTf show both monooxygenase and catechol dioxygenase activity.
- Arnold, Aline,Metzinger, Ramona,Limberg, Christian
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p. 1198 - 1207
(2015/03/05)
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- Controlling the catalytic aerobic oxidation of phenols
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The oxidation of phenols is the subject of extensive investigation, but there are few catalytic aerobic examples that are chemo- and regioselective. Here we describe conditions for the ortho-oxygenation or oxidative coupling of phenols under copper (Cu)-catalyzed aerobic conditions that give rise to ortho-quinones, biphenols or benzoxepines. We demonstrate that each product class can be accessed selectively by the appropriate choice of Cu(I) salt, amine ligand, desiccant and reaction temperature. In addition, we evaluate the effects of substituents on the phenol and demonstrate their influence on selectivity between ortho-oxygenation and oxidative coupling pathways. These results create an important precedent of catalyst control in the catalytic aerobic oxidation of phenols and set the stage for future development of catalytic systems and mechanistic investigations.
- Esguerra, Kenneth Virgel N.,Fall, Yacoub,Petitjean, Laurène,Lumb, Jean-Philip
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supporting information
p. 7662 - 7668
(2014/06/10)
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- {Cu2+-Co3+-Cu2+} and {Cu2+-Fe3+-Cu2+} heterobimetallic complexes and their catalytic properties
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We report on the heterobimetallic complexes {Cu+-Co3+-Cu+} (3), {Cu+-Fe3+-Cu+} (4), {Cu2+-Co3+-Cu2+} (5), and {Cu2+-Fe3+-Cu2+} (6) and show their catalytic applications in the oxidation of hindered phenols and the oxidative coupling of terminal alkynes. The former reaction produces C-C-coupled and dealkylated products, whereas the latter leads to the homo- and heterocoupling of terminal alkynes. The facile redox interconversion between Cu+ and Cu2+ for the secondary metal ions in these heterobimetallic complexes appears to be essential for the observed catalysis, and an important design aspect is better substrate accessibility and the use of molecular oxygen as the sole oxidant. Heterobimetallic complexes {Cu+-Co3+-Cu+} (3), {Cu+-Fe3+-Cu+} (4), {Cu2+-Co3+-Cu2+} (5), and {Cu2+-Fe3+-Cu2+} (6) have been used as catalysts for the oxidation of substituted phenols and the oxidative homo- and heterocoupling of terminal alkynes.
- Srivastava, Sumit,Ali, Afsar,Tyagi, Adish,Gupta, Rajeev
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p. 2113 - 2123
(2015/04/27)
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