- Thermochemistry of Bridged-ring Substances. Enthalpies of Formation of Diamantan-1-, -3-, and -4-ol and of Diamantanone
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The enthalpies of combustion and of sublimation four mono-oxygenated diamantanes have been determined.The derived solid and gas-phase enthalpies of formation in kcal mol-1 at 298.15 K follow: diamantanone, -81.16+/-0.38, -56.53+/-0.41; diamantan-1-ol, -102.49+/-0.24, -74.30+/-0.28; diamantan-3-ol, -98.89+/-0.35, -71.14+/-1.10; diamantan-4-ol, -103.96+/-0.39, -75.80+/-0.39.Oxo and hydroxy group increments within the diamantane, adamantane, and cyclohexane series are discussed.Enthalpy differences betveen the isomeric diamantanols are compared with existing data from equilibration studies in solution.Comparisons are made between the experimental gas-phase enthalpies of formation and those obtained by molecular mechanics (empirical force field) calculations based on the Allinger MM1 force field model.
- Clark, Timothy,Knox, Trevor McO.,McKervey, M. Anthony,Mackle, Henry
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- Nitronium mediated functionalization of adamantane and its derivatives
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Functionalization of adamantane and its derivatives using claycop and nitronium trifluoromethanesulfonate is described.
- Duddu, Rajagopal,Damavarapu, Reddy
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- REACTION OF HALOADAMANTANES WITH SALTS OF NITRO COMPOUNDS
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Silver and mercury salts of nitro compounds react with bromo- or chloroadamantanes with the formation of products of C- and/or O-alkylation, the ratio of which depends on the structure of the initial reactants.The direct experimental evidence of nitronic esters to be isomerized into nitro derivatives and of their role as intermediates in the formation of the nitro derivatives in the alkylation of nitro compounds has been presented for the first time.Keywords: haloadamantanes, trinitromethyladamantanes, nitronic esters,alkylation, isomerization.
- Luk'yanov, O. A.,Savost'yanova, I. A.,Gorelik, V. P.,Shlykova, N. I.,Tartakovskii, V. A.
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- Site-isolated porphyrin catalysts in imprinted polymers
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A meso-tetraaryl ruthenium porphyrin complex having four polymerizable vinylbenzoxy groups (2) has been synthesized by reaction of pyrrole with 4-(vinylbenzoxy)benzaldehyde and subsequent metalation with [Ru 3(CO)12]. The porphyrin complex was immobilized by copolymerization with ethylene glycol dimethacrylate. The resulting polymer P2 was found to catalyze the oxidation of alcohols and alkanes with 2,6-dichloropyridine N-oxide without activation by mineral acids. Under similar conditions, the homogeneous catalyst 2 was completely inefficient. By using diphenylaminomethane and 1-aminoadamantane as coordinatively bound templates during the polymerization procedure, the molecularly imprinted polymers P3 and P4 have been synthesized. Compared with the polymer P2, the imprinted catalysts displayed a significantly increased activity with rate enhancements of up to a factor of 16.
- Burri, Estelle,Oehm, Margarita,Daguenet, Corinne,Severin, Kay
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- Foiled conjugation in α-oximino carbocations
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The 4-CHNOCH3 group is a cation-stabilizing group when placed in the para-position of a cumyl cation. The effect of this group on cumyl cations when flanked by adjacent methyl groups has now been determined. Solvolysis rates of 3,5-(CH3)2-4-(CHNOCH3)cumyl trifluoroacetates are somewhat slower than that of 3,5-dimethylcumyl trifluoroacetate. This is attributed to steric inhibition of the cation-stabilizing resonance effect of the p-oximino group. In a 1-adamantyl system, where an α-oximino group has been placed directly adjacent to a developing cationic center, solvolysis rates relative to 1-adamantyl mesylate are slowed by a factor of 108. This is attributed a cation-destabilizing inductive effect where geometric constraints prevent stabilizing orbital overlap of the cationic center with the adjacent α-oximino group. This cation-destabilizing effect fades in the homoadamantyl and the bicyclo[3.3.1]nonyl systems, where rate-retarding effects are 1.6 × 104 and 1.5 × 102, respectively. The behavior of geometrically constrained α-oximino cations parallels that of analogously constrained allylic cations. Computational studies at the HF/6-31G* level indicate that twisting the α-oximino group out of planarity with a tertiary cationic center into a perpendicular arrangement decreases stabilization by 21 kcal/mol. These studies suggest that conjugative interactions, and not ground state destabilization, are the most important factors in controlling rates of formation of α-oximino cations from mesylates and trifluoroacetates.
- Creary, Xavier,Jiang, Ziqi
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- Preparative aerobic oxidations with basidiomycetous enzymes: CH-functionalization of adamantane
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The potential of basidiomycetous enzymes for selective alkane CH-functionalizations in aqueous media has been disclosed utilizing surface and submerged cultures. A screening displayed the high catalytic activity of Dichomitus albidofuscus, Pholiota squarrosa, and Abortiporus biennis in aerobic oxidations of adamantane as a model hydrocarbon. With isopropanol as a co-solvent, the oxidation was accelerated significantly without changes of the fungal growth. 1-Adamantanol was obtained in 40% preparative yield from the oxidation of adamantane by D. albidofuscus. The CH-positional selectivity (3°/2°= 3.6) and the deuterium kinetic isotopic effect (kH/kD = 2.25) values provide evidence for the participation of fungal metalloenzymes in the CH-activation step.
- Zhuk, Tatyana S.,Goldmann, Michael,Hofmann, Julia,Pohl, Juliane C.S.,Zorn, Holger
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- Oxidation of organic compounds by ozone on a surface: 1. Ozonization of adamantane on silica gel
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Adamantanol was obtained by the ozonization of adamantane, at -78°C, adsorbed on silica gel. Ozone does not decompose on silica gel in the absence of a substrate. Ozonization of adamantane on silica gel is accompanied by chemiluminescence in the IR region. The chemiluminescence quenching is of first-order with the effective rate constant k′. In the range from 0.4 to 5 mmol, k′ depends linearly on the amount of adamantane adsorbed on the silica gel. The activation energy Ea = 9.97±1.89 kcal mol-1 and the pre-exponential factor A = (2.76±0.52)·106 were calculated from the temperature dependence of k′.
- Avzyanova,Kabal'nova,Shereshovets
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- Aprotic diazotization of endo-7-aminomethylbicyclo[3,3,1]nonan-3-one
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Aprotic diazotization of endo-7-aminomethylbicyclo[3,3,1]nonan-3-one yields protoadamantan-4-one and 3-methylbicyclo[3,3,1]non-2-en-7-one; the latter was converted into adamantan-1-ol on catalytic hydrogenation with Pd-C.
- Liu, Jih-Hua,Kovacic, Peter
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- Dissociative electron transfer to dihaloalkanes. electrochemical reduction of 1,3-dihaloadamantanes, 1,4-dihalobicyclo[2.2.2]octanes, and 1,3-dihalobicyclo[1.1.1]pentanes
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The electrochemical reductive cleavage of the title compounds was investigated by means of cyclic voltammetry and electrolysis. The reaction is a two-electron process that yields competitively ring closure (or fragmentation) products and the monohalide resulting from the expulsion of the best leaving halide ion. Product selection occurs at the level of the carbanion resulting from the reduction of the one-electron reductive cleavage radical. In the formation of the latter, electron transfer and bond breaking are concerted; thus, the anion radical is not involved as an intermediate. The variations in the reduction potential observed in the three series of compounds can be rationalized, by application of the dissociative electron-transfer theory, as related variations of the bond dissociation energy of the first carbon-halogen bond to be cleaved. In the adamantane and bicyclopentane series, these are mainly the result of through-space-bonded interactions in the one-electron reductive cleavage radical and, to a lesser extent, in the starting dihalide itself, while through-bond interactions appear to prevail in the bicyclooctane series.
- Adcock, William,Clark, Christopher I.,Houmam, Abdelaziz,Krstic, Alexander R.,Pinson, Jean,Savéant, Jean-Michel,Taylor, Dennis K.,Taylor, Julian F.
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- Reverse reactivity in hydroxylation of adamantane and epoxidation of cyclohexene catalyzed by the mononuclear ruthenium-oxo complexes with 6-substituted tripodal polypyridine ligands
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The electronic character of the ruthenium complexes with tripodal polypyridine ligands, which is controlled by the substituted groups at pyridine 6-position, gives rise to differences in the reactivity for the ruthenium catalyzed hydroxylation of adamantane and epoxidation of cyclohexene with PhIO as an oxidant; Ru complexes containing electron-withdrawing groups (1, 3, and 5) promote the epoxidation, while those containing electron-donating groups (2, 4, and 6) promote the hydroxylation.
- Jitsukawa, Koichiro,Oka, Yoshiyuki,Einaga, Hisahiko,Masuda, Hideki
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- Hydrogen-atom and oxygen-atom transfer reactivities of iron(
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A series of iron(ii) complexes with the general formula [FeII(L2-Qn)(L)]n+ (n = 1, L = F?, Cl?; n = 2, L = NCMe, H2O) have been isolated and characterized. The X-ray crystallographic data reveals that
- Banerjee, Sridhar,Haukka, Matti,Hossain, Md. Kamal,Huelsmann, Ricardo Dagnoni,Martendal, Edmar,Munshi, Sandip,Nordlander, Ebbe,Paine, Tapan K.,Peralta, Rosely,Singh, Reena,Sinha, Arup,Valiati, Andrei Felipe,Wendt, Ola F.,Xavier, Fernando,Yiga, Solomon
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supporting information
p. 870 - 884
(2022/02/01)
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- Direct Hydrodecarboxylation of Aliphatic Carboxylic Acids: Metal- and Light-Free
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A mild and inexpensive method for direct hydrodecarboxylation of aliphatic carboxylic acids has been developed. The reaction does not require metals, light, or catalysts, rendering the protocol operationally simple, easy to scale, and more sustainable. Crucially, no additional H atom source is required in most cases, while a broad substrate scope and functional group tolerance are observed.
- Burns, David J.,Lee, Ai-Lan,McLean, Euan B.,Mooney, David T.
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supporting information
p. 686 - 691
(2022/01/28)
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- RUTHENIUM COMPLEX AND PRODUCTION METHOD THEREOF, CATALYST, AND PRODUCTION METHOD OF OXYGEN-CONTAINING COMPOUND
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PROBLEM TO BE SOLVED: To provide a ruthenium complex that is particularly useful as a catalyst for oxidizing a substrate having a carbon-hydrogen bond. SOLUTION: The ruthenium complex represented by the general formula (i) or a cis conformer thereof is provided. In the general formula (i), R1 represents H, a phenyl group or a substituted phenyl group; R2 represents H, a phenyl group or an alkyl group; L1 represents halogen or water molecule; L2 represents triphenylphosphine, pyridine, imidazole or dimethylsulfoxide; X represents halogen; and n represents 1 or 2. SELECTED DRAWING: None COPYRIGHT: (C)2021,JPO&INPIT
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Paragraph 0086-0097
(2021/01/29)
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- KF-Promoted copper-catalyzed highly efficient and selective oxidation of methane and other alkanes with a dramatic additive effect
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Highly efficient oxidation of methane to methyl trifluoroacetate mediated by CuCl/KF/K2S2O8in trifluoroacetic acid (TFA) and trifluoroacetic anhydride (TFAA) is described. The additive effect has been systematically evaluated and potassium fluoride (KF) was identified as the most effective promoter among the salts screened. KF is conjectured to exhibit the salt effect to promote the [SO4˙]?radical to escape the solvent cage based on control experiments. Cyclohexane and adamantane could also be efficiently oxidized into benzene or corresponding trifluoroacetates.
- Chen, Wei,Chen, Xiaoyan,Fan, Wu,Li, Suhua,Liu, Luyao
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p. 4962 - 4968
(2021/07/26)
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- Cationic nickel(II) pyridinophane complexes: Synthesis, structures and catalytic activities for C-H oxidation
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A series of nickel(II) pyridinophane complexes were synthesized and characterized by X-ray crystallographic analysis. Their IR spectra supported the existence of mononuclear nickel(II) complexes in solution. Furthermore, we conducted catalytic CH oxidation of cyclooctane with nickel(II) pyridinophanes as the catalysts. The activity of nickel(II) pyridinophanes was affected by steric hindrance around the nitrogen atoms.
- Nishimura, Tsubasa,Ando, Yuki,Shinokubo, Hiroshi,Miyake, Yoshihiro
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supporting information
p. 1049 - 1052
(2021/05/19)
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- Catalytic Highly Regioselective C-H Oxygenation Using Water as the Oxygen Source: Preparation of 17O/18O-Isotope-Labeled Compounds
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We found that the oxygen atom of water is activated to iodosylbenzene derivatives via reversible hydrolysis of PhI(OOCR)2 and can be used to the oxygen source for ruthenium(bpga)-catalyzed site-selective C-H oxygenation. Ru(bpga)/PhI(OOCR)2/H2O system, sterically less bulky methinic and methylenic C-H bonds in various compounds can be converted to desired oxygen functional groups in a site-selective manner. Using this method, oxygen-isotope labeled compounds such as d-[3-17O/18O]-mannose can be prepared in a multigram scale.
- Doiuchi, Daiki,Uchida, Tatsuya
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supporting information
p. 7301 - 7305
(2021/10/01)
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- Photo-tunable oxidation of toluene and its derivatives catalyzed by TBATB
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In this report, tetrabutylammonium tribromide (TBATB) was introduced as an efficient visible light active catalyst to carry out the aerobic oxidation of toluene, its derivatives, and some of methyl arenes to benzaldehydes, benzoic acids and ketones in good to high yields. All the oxidation reactions were performed under mild conditions using oxygen as a green oxidant, a catalytic amount of TBATB under blue (460 nm), royal blue (430 nm), and violet LED (400 nm) irradiation. It was found that the reactions selectivity was significantly affected by changing the solvent (from CH3CN to EtOAc) and LED wavelength (from blue to violet). In the following, our mechanistic studies revealed that the visible light oxidation of toluenes and methyl arenes over TBATB could be following a benzyl peroxy radical intermediate.
- Mardani, Atefeh,Kazemi, Foad,Kaboudin, Babak
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- Bimodal Evans-Polanyi Relationships in Hydrogen Atom Transfer from C(sp3)-H Bonds to the Cumyloxyl Radical. A Combined Time-Resolved Kinetic and Computational Study
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The applicability of the Evans-Polanyi (EP) relationship to HAT reactions from C(sp3)-H bonds to the cumyloxyl radical (CumO?) has been investigated. A consistent set of rate constants, kH, for HAT from the C-H bonds of 56 substrates to CumO?, spanning a range of more than 4 orders of magnitude, has been measured under identical experimental conditions. A corresponding set of consistent gas-phase C-H bond dissociation enthalpies (BDEs) spanning 27 kcal mol-1 has been calculated using the (RO)CBS-QB3 method. The log kH′ vs C-H BDE plot shows two distinct EP relationships, one for substrates bearing benzylic and allylic C-H bonds (unsaturated group) and the other one, with a steeper slope, for saturated hydrocarbons, alcohols, ethers, diols, amines, and carbamates (saturated group), in line with the bimodal behavior observed previously in theoretical studies of reactions promoted by other HAT reagents. The parallel use of BDFEs instead of BDEs allows the transformation of this correlation into a linear free energy relationship, analyzed within the framework of the Marcus theory. The ΔG?HAT vs ΔG°HAT plot shows again distinct behaviors for the two groups. A good fit to the Marcus equation is observed only for the saturated group, with λ = 58 kcal mol-1, indicating that with the unsaturated group λ must increase with increasing driving force. Taken together these results provide a qualitative connection between Bernasconi's principle of nonperfect synchronization and Marcus theory and suggest that the observed bimodal behavior is a general feature in the reactions of oxygen-based HAT reagents with C(sp3)-H donors.
- Bietti, Massimo,Dilabio, Gino A.,Galeotti, Marco,Groff, Benjamin D.,Mayer, James M.,Romero-Montalvo, Eduardo,Salamone, Michela,Van Santen, Jeffrey A.
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supporting information
p. 11759 - 11776
(2021/08/20)
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- Revisiting Alkane Hydroxylation with m-CPBA (m-Chloroperbenzoic Acid) Catalyzed by Nickel(II) Complexes
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Mechanistic studies are performed on the alkane hydroxylation with m-CPBA (m-chloroperbenzoic acid) catalyzed by nickel(II) complexes, NiII(L). In the oxidation of cycloalkanes, NiII(TPA) acts as an efficient catalyst with a high yield and a high alcohol selectivity. In the oxidation of adamantane, the tertiary carbon is predominantly oxidized. The reaction rate shows first-order dependence on [substrate] and [NiII(L)] but is independent on [m-CPBA]; vobs=k2[substrate][NiII(L)]. The reaction exhibited a relatively large kinetic deuterium isotope effect (KIE) of 6.7, demonstrating that the hydrogen atom abstraction is involved in the rate-limiting step of the catalytic cycle. Furthermore, NiII(L) supported by related tetradentate ligands exhibit apparently different catalytic activity, suggesting contribution of the NiII(L) in the catalytic cycle. Based on the kinetic analysis and the significant effects of O2 and CCl4 on the product distribution pattern, possible contributions of (L)NiII?O. and the aroyloxyl radical as the reactive oxidants are discussed.
- Itoh, Mayu,Itoh, Shinobu,Kubo, Minoru,Morimoto, Yuma,Shinke, Tomoya,Sugimoto, Hideki,Wada, Takuma,Yanagisawa, Sachiko
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p. 14730 - 14737
(2021/09/29)
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- Enhancing Chemo- And Stereoselectivity in C-H Bond Oxygenation with H2O2by Nonheme High-Spin Iron Catalysts- And Role of Lewis Acid and Multimetal Centers
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Spin states of iron often direct the selectivity in oxidation catalysis by iron complexes using hydrogen peroxide (H2O2) on an oxidant. While low-spin iron(III) hydroperoxides display stereoselective C-H bond hydroxylation, the reactions are nonstereoselective with high-spin iron(II) catalysts. The catalytic studies with a series of high-spin iron(II) complexes of N4 ligands with H2O2 and Sc3+ reported here reveal that the Lewis acid promotes catalytic C-H bond hydroxylation with high chemo- and stereoselectivity. This reactivity pattern is observed with iron(II) complexes containing two cis-labile sites. The enhanced selectivity for C-H bond hydroxylation catalyzed by the high-spin iron(II) complexes in the presence of Sc3+ parallels that of the low-spin iron catalysts. Furthermore, the introduction of multimetal centers enhances the activity and selectivity of the iron catalyst. The study provides insights into the development of peroxide-dependent bioinspired catalysts for the selective oxygenation of C-H bonds without the restriction of using iron complexes of strong-field ligands.
- Das, Abhishek,Jana, Rahul Dev,Paine, Tapan Kanti
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supporting information
p. 5969 - 5979
(2021/05/04)
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- Reduced Amino Acid Schiff Base-Iron(III) Complexes Catalyzing Oxidation of Cyclohexane with Hydrogen Peroxide
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The reduced amino acid Schiff base ligands have been prepared and were coordinated with ferric chloride to generate the iron(III) complexes. The ligands and complexes have been characterized using FT-IR, UV-vis, elemental analysis, ICP-AES analysis, mass spectra etc. After the structural characterization, these complexes were applied for the oxidation of cyclohexane using hydrogen peroxide as the oxidant under mild conditions. The activity tests showed that the L-phenylalanine-derived reduced Schiff base iron(III) complex(Ph?FeCl) afforded the highest yield of cyclohexanol and cyclohexanone(total yield up to 23.2 %). Notably, the Ph?FeCl complex catalyzes the reaction via a heterogeneous approach, allowing the complex to be separated and recycled conveniently after the oxidation reaction. Besides, the Ph?FeCl catalyst can also be extended for the selective oxidation of other alkanes and aromatics into alcohols, ketones and phenols etc. Finally, the reaction mechanism of cyclohexane oxidation on the iron(III) complex was proposed as well by the free radical inhibitors and EPR study of active intermediates.
- Zheng, Anna,Zhou, Qingqing,Ding, Bingjie,Li, Difan,Zhang, Tong,Hou, Zhenshan
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p. 3385 - 3395
(2021/08/23)
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- Aqueous Microdroplets Capture Elusive Carbocations
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Carbocations are short-lived reactive intermediates in many organic and biological reactions that are difficult to observe. This field sprung to life with the discovery by Olah that a superacidic solution allowed the successful capture and nuclear magnetic resonance characterization of transient carbocations. We report here that water microdroplets can directly capture the fleeting carbocation from a reaction aliquot followed by its desorption to the gas phase for mass spectrometric detection. This was accomplished by employing desorption electrospray ionization mass spectrometry to detect a variety of short-lived carbocations (average lifetime ranges from nanoseconds to picoseconds) obtained from different reactions (e.g., elimination, substitution, and oxidation). Solvent-dependent studies revealed that aqueous microdroplets outperform organic microdroplets in the capture of carbocations. We provide a mechanistic insight demonstrating the survival of the reactive carbocation in a positively charged aqueous microdroplet and its subsequent ejection to the gas phase for mass spectrometric analysis.
- Kumar, Anubhav,Mondal, Supratim,Banerjee, Shibdas
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supporting information
p. 2459 - 2463
(2021/02/16)
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- Selective Aerobic Oxidation of Secondary C (sp3)-H Bonds with NHPI/CAN Catalytic System
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Abstract: The direct aerobic oxidation of secondarty C(sp3)-H bonds was achieved in the presence of N-hydroxyphthalimide (NHPI) and cerium ammonium nitrate (CAN) under mild conditions. Various benzylic methylenes could be oxidized to carbonyl compounds in satisfied selectivity while saturated cyclic alkanes could be further oxidized to the corresponding lactones with the catalytic system. Remarkably, 25% of isochroman was converted to corresponding ketone with a selectivity of 96%. The reaction was initiated by hydrogen atom abstraction from NHPI by cerium and nitrates under oxygen atmosphere to form PINO radicals. 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) addition experiments showed that the oxidation proceeded via a complex radical chain mechanism and an ion pathway. Graphic Abstract: [Figure not available: see fulltext.]
- Wang, Lingyao,Zhang, Yuanbin,Yuan, Haoran,Du, Renfeng,Yao, Jia,Li, Haoran
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p. 1663 - 1669
(2020/10/21)
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- Gold-Catalyzed Direct C(sp3)?H Acetoxylation of Saturated Hydrocarbons
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In this communication we report our studies towards the development of a gold-catalyzed direct acetoxylation of C(sp3)?H bonds. We achieve this through the use of the hypervalent iodine reagent PhI(OAc)2 in combination with a simple gold salt (HAuBr4) as the catalyst. Through a comparison of the reactivities of cyclooctane and adamantane we judge the reaction to proceed via hydride transfer. This is further substantiated through computational studies of the relative energies for the anions, radicals and cations derived from C?H bond cleavage of cyclooctane and adamantane relevant to the C?H cleaving step.
- Jo, Tae Geun,Klein, Johannes E. M. N.
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p. 4087 - 4091
(2021/08/25)
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- A General Method for Photocatalytic Decarboxylative Hydroxylation of Carboxylic Acids
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A general and practical method for decarboxylative hydroxylation of carboxylic acids was developed through visible light-induced photocatalysis using molecular oxygen as the green oxidant. The addition of NaBH4 to in situ reduce the unstable peroxyl radical intermediate much broadened the substrate scope. Different sp3 carbon-bearing carboxylic acids were successfully employed as substrates, including phenylacetic acid-type substrates, as well as aliphatic carboxylic acids. This transformation worked smoothly on primary, secondary, and tertiary carboxylic acids.
- Khan, Shah Nawaz,Zaman, Muhammad Kashif,Li, Ruining,Sun, Zhankui
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p. 5019 - 5026
(2020/05/01)
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- Phenylene-bridged bis(benzimidazolium) (BBIm2+): a dicationic organic photoredox catalyst
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A dicationic photoredox catalyst composed of phenylene-bridged bis(benzimidazolium) (BBIm2+) was designed, synthesised and demonstrated to promote the photochemical decarboxylative hydroxylation and dimerisation of carboxylic acids. The catalytic activity of BBIm2+ was higher than that for a monocation analogue, suggesting that the dicationic nature of BBIm2+ plays a key role in these decarboxylative reactions. The rate constant for the decay of the triplet-triplet absorption of the excited BBIm2+ increased with increasing concentration of the carboxylate anion with a saturated dependence, suggesting that photoinduced electron transfer occurs within the ion pair complex composed of the triplet excited state of BBIm2+ and a carboxylate anion.
- Kodama, Takuya,Kubo, Maiko,Shinji, Wataru,Ohkubo, Kei,Tobisu, Mamoru
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p. 12109 - 12117
(2020/11/27)
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- Robust Mn(iii): N -pyridylporphyrin-based biomimetic catalysts for hydrocarbon oxidations: heterogenization on non-functionalized silica gel versus chloropropyl-functionalized silica gel
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Two classes of heterogenized biomimetic catalysts were prepared and characterized for hydrocarbon oxidations: (1) by covalent anchorage of the three Mn(iii) meso-tetrakis(2-, 3-, or 4-pyridyl)porphyrin isomers by in situ alkylation with chloropropyl-functionalized silica gel (Sil-Cl) to yield Sil-Cl/MnPY (Y = 1, 2, 3) materials, and (2) by electrostatic immobilization of the three Mn(iii) meso-tetrakis(N-methylpyridinium-2, 3, or 4-yl)porphyrin isomers (MnPY, Y = 4, 5, 6) on non-modified silica gel (SiO2) to yield SiO2/MnPY (Y = 4, 5, 6) materials. Silica gel used was of column chromatography grade and Mn porphyrin loadings were deliberately kept at a low level (0.3% w/w). These resulting materials were explored as catalysts for iodosylbenzene (PhIO) oxidation of cyclohexane, n-heptane, and adamantane to yield the corresponding alcohols and ketones; the oxidation of cyclohexanol to cyclohexanone was also investigated. The heterogenized catalysts exhibited higher efficiency and selectivity than the corresponding Mn porphyrins under homogeneous conditions. Recycling studies were consistent with low leaching/destruction of the supported Mn porphyrins. The Sil-Cl/MnPY catalysts were more efficient and more selective than SiO2/MnPY ones; alcohol selectivity may be associated with hydrophobic silica surface modification reminiscent of biological cytochrome P450 oxidations. The use of widespread, column chromatography, amorphous silica yielded Sil-Cl/MnPY or SiO2/MnPY catalysts considerably more efficient than the corresponding, previously reported materials with mesoporous Santa Barbara Amorphous No 15 (SBA-15) silica. Among the materials studied, in situ derivatization of Mn(iii) 2-N-pyridylporphyrin by covalent immobilization on Sil-Cl to yield Sil-Cl/MnP1 showed the best catalytic performance with high stability against oxidative destruction and reusability/recyclability.
- Pinto, Victor Hugo A.,Falc?o, Nathália K. S. M.,Mariz-Silva, Bárbara,Fonseca, Maria Gardennia,Rebou?as, Júlio S.
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supporting information
p. 16404 - 16418
(2020/12/03)
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- Catalytic oxyfunctionalization of saturated hydrocarbons by non-heme oxo-bridged diiron(III) complexes: role of acetic acid on oxidation reaction
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Oxo-bridged diiron(III) complexes [Fe2O(L1)2(H2O)2](ClO4)4 (1) and [Fe2O(L2)2(H2O)2](ClO4)4 (2), where L1 and L2 are tetradentate N-donor N,N′-bis(2-pyridylmethyl)-1,2-cyclohexanediamine and N,N′-bis(2-pyridylmethyl)ethane-1,2-diamine respectively, have been isolated as synthetic models of non-heme iron oxygenases and characterized by physicochemical and spectroscopic methods. Both the complexes have been studied as catalysts for the oxyfunctionalization of saturated hydrocarbons using green hydrogen peroxide (H2O2) as oxidant under mild conditions. The selectivity (A/K) and regioselectivity (3°/2°) in oxidative C–H functionalization of alkanes suggests the involvement of metal-based intermediate in the oxygenation reaction. The catalytic efficiency is found to be strongly dependent on the presence of acetic acid. Remarkable increase in conversion and selectivity favoring the formation of alcohols in the oxidation of cyclohexane and cyclooctane and exclusive hydroxylation of adamantane with drastic enhancement of regioselectivity has been achieved by the addition of acetic acid in the presence of H2O2.
- Agarwalla, Uday Sankar
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p. 583 - 588
(2020/07/14)
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- Iron(III) 5,15-diazaporphyrin catalysts for the direct oxidation of C(sp3)-H bonds
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5,15-Diazaporphyrins are porphyrin analogues with imine-type sp2-hybridized nitrogen atoms at the meso-positions. Even though these compounds are more electron-deficient than regular porphyrins, the use of iron diazaporphyrins as catalysts has not been reported. Herein, we disclose the synthesis, structure, and electronic properties of iron(III) 5,15-diazaporphyrins. We evaluate their structures and electronic natures by X-ray analysis and electrochemical analyses. We also demonstrate that chloroiron(III) 5,15-diazaporphyrins exhibit high catalytic activity in the direct oxidation of alkanes due to their intrinsic electron-deficient nature. On the basis of stoichiometric reactions of iron(III) diazaporphyrin with iodosylbenzene as an oxidant, it was possible to demonstrate the existence of an iodosylbenzene-iron diazaporphyrin adduct reaction intermediate that serves as a reservoir to generate oxo-iron species.
- Ikeue, Takahisa,Miyake, Yoshihiro,Nishimura, Tsubasa,Shinokubo, Hiroshi,Shoji, Osami
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supporting information
p. 15751 - 15756
(2020/11/20)
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- Non-Heme-Type Ruthenium Catalyzed Chemo- and Site-Selective C?H Oxidation
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Herein, we developed a Ru(II)(BPGA) complex that could be used to catalyze chemo- and site-selective C?H oxidation. The described ruthenium complex was designed by replacing one pyridyl group on tris(2-pyridylmethyl)amine with an electron-donating amide ligand that was critical for promoting this type of reaction. More importantly, higher reactivities and better chemo-, and site-selectivities were observed for reactions using the cis-ruthenium complex rather than the trans-one. This reaction could be used to convert sterically less hindered methyne and/or methylene C?H bonds of a various organic substrates, including natural products, into valuable alcohol or ketone products.
- Doiuchi, Daiki,Nakamura, Tatsuya,Hayashi, Hiroki,Uchida, Tatsuya
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supporting information
p. 762 - 765
(2020/03/05)
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- Effect of Ligand Fields on the Reactivity of O2-Activating Iron(II)-Benzilate Complexes of Neutral N5 Donor Ligands
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Three new iron(II)-benzilate complexes [(N4Py)FeII(benzilate)]ClO4 (1), [(N4PyMe2)FeII(benzilate)]ClO4 (2) and [(N4PyMe4)FeII(benzilate)]ClO4 (3) of neutral pentadentate nitrogen donor ligands have been isolated and characterized to study their dioxygen reactivity. Single-crystal X-ray structures reveal a mononuclear six-coordinate iron(II) center in each case, where benzilate binds to the iron center in monodentate mode via one carboxylate oxygen. Introduction of methyl groups in the 6-positions of the pyridine rings makes the N4PyMe2 and N4PyMe4 ligand fields weaker compared to that of the parent N4Py ligand. All the complexes (1–3) react with dioxygen to decarboxylate the coordinated benzilate to benzophenone quantitatively. The decarboxylation is faster for the complex of the more sterically hindered ligand and follows the order 3>2>1. The complexes display oxygen atom transfer reactivity to thioanisole and also exhibit hydrogen atom transfer reactions with substrates containing weak C?H bonds. Based on interception studies with external substrates, labelling experiments and Hammett analysis, a nucleophilic iron(II)-hydroperoxo species is proposed to form upon two-electron reductive activation of dioxygen by each iron(II)-benzilate complex. The nucleophilic oxidants are converted to the corresponding electrophilic iron(IV)-oxo oxidant upon treatment with a protic acid. The high-spin iron(II)-benzilate complex with the weakest ligand field results in the formation of a more reactive iron-oxygen oxidant.
- Bhattacharya, Shrabanti,Paine, Tapan Kanti,Singh, Reena
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- Oxoiron(v) mediated selective electrochemical oxygenation of unactivated C-H and CC bonds using water as the oxygen source
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An efficient electrochemical method for the selective oxidation of C-H bonds of unactivated alkanes (BDE ≤97 kcal mol-1) and CC bonds of alkenes using a biomimetic iron complex, [(bTAML)FeIII-OH2]-, as the redox mediator in an undivided electrochemical cell with inexpensive carbon and nickel electrodes is reported. The O-atom of water remains the source of O-incorporation in the product formed after oxidation. The products formed upon oxidation of C-H bonds display very high regioselectivity (75:1, 3°:2° for adamantane) and stereo-retention (RC ~99% for cyclohexane derivatives). The substrate scope includes natural products such as cedryl acetate and ambroxide. For alkenes, epoxides were obtained as the sole product. Mechanistic studies show the involvement of a high-valent oxoiron(v) species, [(bTAML)FeV(O)]- formed via PCET (overall 2H+/2e-) from [(bTAML)FeIII-OH2]- in CPE at 0.80 V (vs. Ag/AgNO3). Moreover, electrokinetic studies for the oxidation of C-H bonds indicate a second-order reaction with the C-H abstraction by oxoiron(v) being the rate-determining step.
- Chandra, Bittu,Gupta, Sayam Sen,Hellan, K. M.,Pattanayak, Santanu
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p. 11877 - 11885
(2020/11/18)
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- Mechanism of Ni-catalyzed oxidations of unactivated C(sp3)-H Bonds
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The Ni-catalyzed oxidation of unactivated alkanes, including the oxidation of polyethylenes, by meta-chloroperbenzoic acid (mCPBA) occur with high turnover numbers under mild conditions, but the mechanism of such transformations has been a subject of debate. Putative, high-valent nickel-oxo or nickel-oxyl intermediates have been proposed to cleave the C-H bond, but several studies on such complexes have not provided strong evidence to support such reactivity toward unactivated C(sp3)-H bonds. We report mechanistic investigations of Ni-catalyzed oxidations of unactivated C-H bonds by mCPBA. The lack of an effect of ligands, the formation of carbon-centered radicals with long lifetimes, and the decomposition of mCPBA in the presence of Ni complexes suggest that the reaction occurs through free alkyl radicals. Selectivity on model substrates and deuterium-labeling experiments imply that the m-chlorobenzoyloxy radical derived from mCPBA cleaves C-H bonds in the alkane to form an alkyl radical, which subsequently reacts with mCPBA to afford the alcohol product and regenerate the aroyloxy radical. This free-radical chain mechanism shows that Ni does not cleave the C(sp3)-H bonds as previously proposed; rather, it catalyzes the decomposition of mCPBA to form the aroyloxy radical.
- Qiu, Yehao,Hartwig, John F.
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supporting information
p. 19239 - 19248
(2020/11/13)
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- C–H functionalization of alkanes, bactericidal and antiproliferative studies of a gold(III)-phenanthroline complex
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This research article demonstrates the synthesis, structural characterization, C–H functionalization, bactericidal activity and anti-proliferative studies of a mononuclear Au(III) complex, [Au(phen)Cl2]NO3 (1) [phen = 1,10-phenanthroline]. X-ray structural analysis of 1 reveals that the Au(III) complex crystallises in a monoclinic system with P21/c space group and adopts a perfect square planar geometry. The Au(III) complex has been evaluated as an efficient catalytic system towards C–H activation of a series of alkane molecules in presence of TBHP. The catalyst exhibits moderate to excellent reactivity with good selectivity toward aldehyde or ketone when aryl alkanes are used, and ketone is formed when cyclic alkanes are tested. This catalytic reaction recommends the involvement of freely diffusing hydroxyl radicals rather than metal-based oxidant for this course of catalysis. The cytotoxic activity of the Au(III) complex have been investigated against the A549 human lung cancer cell line that induces apoptosis mode of cell death and loss of mitochondrial membrane potential are prominent characteristics as an anti cancer drug as well as antibacterial activity against Staphylococcus aureus.
- Al-Hunaiti, Afnan,Balakrishnan, Gowdhami,Biswas, Bhaskar,Dey, Dhananjay,Dharumadurai, Dhanasekaran,Gopal, Vinothini,Perumalsamy, Balaji,Ramasamy, Thirumurugan
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- Selective oxygenation of unactivated C-H bonds by dioxygen: Via the autocatalytic formation of oxoiron(v) species
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Selective catalytic oxygenation of unactivated C-H bonds for a series of substrates by dioxygen using iron complexes was performed without the use of a co-reductant. Mechanistic studies indicate that the reaction proceeded via the autocatalytic formation of an oxoiron(v) intermediate, which brings high regioselectivity and stereoretention.
- Chandra, Bittu,De, Puja,Sen Gupta, Sayam
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supporting information
p. 8484 - 8487
(2020/08/13)
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- Ionic liquid-stabilized vanadium oxo-clusters catalyzing alkane oxidation by regulating oligovanadates
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Alkane oxidation under mild conditions occupies an important position in the chemical industry. Herein, we have designed a novel class of ionic liquid ([TBA][Pic])-stabilized vanadium oxo-clusters (TBA = tetrabutylammonium; Pic = picolinate ions), in which the molar ratio of the IL to V atoms can be tuned facilely to obtain V-OC?IL-0.5, V-OC?IL-1 and V-OC?IL-2, respectively. The as-synthesized vanadium oxo-clusters have been characterized by elemental analysis, FT-IR, UV-vis, XRD, TGA, EPR, NMR and MS. These vanadium oxo-clusters were catalytically active for catalyzing the oxidation of cyclohexane with H2O2 as an oxidant. In particular, the oxo-cluster V-OC?IL-1 (where IL/V is 1.0) can provide an approximately 30% total yield of KA oil (cyclohexanol and cyclohexanone) without adding any co-catalyst at 50 °C within 1.0 h. Moreover, the present vanadium oxo-cluster was recyclable owing to the modification of the IL and it can also be extended to the oxidation of the sp2 hybrid aromatic ring. The further characterization results demonstrated that the oligovanadate anions were strongly dependent on the molar ratio of the IL to V atoms. The vanadium oxo-clusters with the appropriate molar ratio of IL/V could exist in the form of a trimer and a dimer due to the presence of the TBA cation and the coordination of picolinate. Notably, the oligovanadate anions are highly active species for the C-H oxidation but the mononuclear vanadate afforded a very poor activity according to the activity assessment and the identification of vanadium species from the 51V NMR spectra and MS spectra. The annihilation reaction of free radicals and EPR characterization suggested that the vanadium oxo-clusters operated via a mechanism of the HO radical in the oxidation reaction.
- Ding, Bingjie,Gong, Xueqing,Hou, Zhenshan,Li, Difan,Yao, Yefeng,Zhang, Ran,Zheng, Anna,Zhou, Qingqing
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p. 7601 - 7612
(2020/11/27)
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- Highly selective tetrahydropyranylation/dehydropyranylation of alcohols and phenols using porous phenolsulfonic acid-formaldehyde resin catalyst under solvent-free condition
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An efficient protocol for solvent-free chemoselective tetrahydropyranylation/depyranylation of alcohols and phenols is reported herein using mesoporous Phenolsulfonic Acid Formaldehyde Resins as a heterogeneous acid catalyst. The catalyst successfully performed chemoselective protection and deprotection reactions of a wide range of substrates ranging from primary to secondary and tertiary alcohols and also phenols. The reactions were carried out at ambient temperature under solvent-free condition (SolFC) which resulted in high yields within a very short time. FT-IR, TEM, SEM, EDS and TG-DSC analysis techniques were employed to characterize the synthesized polymeric catalyst. The chemoselective nature of our method was confirmed using 13C DEPT-135 NMR studies. The polymer catalyst was found to be recoverable even after 10th catalytic cycle without much depreciation in its activity. The heterogeneity of the catalyst was verified by hot filtration method. Good yield, energy and cost- effective method, solvent-free protocol, mild reaction conditions, no inert atmosphere, metal-free heterogeneous polymer catalyst and excellent recoverability of the catalyst are notable milestones of the reported protocol.
- Rajkumari, Kalyani,Laskar, Ikbal Bahar,Kumari, Anupama,Kalita, Bandita,Rokhum, Lalthazuala
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- Efficient alkane hydroxylation catalysis of nickel(ii) complexes with oxazoline donor containing tripodal tetradentate ligands
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Tris(oxazolynylmethyl)amine TOAR(where R denotes the substituent groups on the fourth position of the oxazoline rings) complexes of nickel(ii) have been synthesized as catalyst precursors for alkane oxidation withmeta-chloroperoxybenzoic acid (m-CPBA). The molecular structures of acetato, nitrato,meta-chlorobenzoato and chlorido complexes with TOAMe2have been determined using X-ray crystallography. The bulkiness of the substituent groups R affects the coordination environment of the nickel(ii) centers, as has been demonstrated by comparison of the molecular structures of chlorido complexes with TOAMe2and TOAtBu. The nickel(ii)-acetato complex with TOAMe2is an efficient catalyst precursor compared with the tris(pyridylmethyl)amine (TPA) analogue. Oxazolynyl donors’ strong s-electron donating ability will enhance the catalytic activity. Catalytic reaction rates and substrate oxidizing position selectivity are controlled by the structural properties of the R of TOAR. Reaction of the acetato complex with TOAMe2andm-CPBA yields the corresponding acylperoxido species, which can be detected using spectroscopy. Kinetic studies of the decay process of the acylperoxido species suggest that the acylperoxido species is a precursor of an active species for alkane oxidation.
- Hikichi, Shiro,Horii, Sena,Nakazawa, Jun,Okamura, Masaya,Terao, Ikumi
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p. 6108 - 6118
(2020/05/25)
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- Synthesis of azolyl-substituted adamantane derivatives and their coordination compounds
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Reactions of adamantylazoles with nucleophiles (water, carbon monoxide, acetonitrile) in sulfuric acid were studied. New bifunctional adamantane derivatives containing one heterocyclic substituent and one hydroxyl or acetamide substituent were synthesized. The coordination compounds of copper(II) and zinc(II) with 1-adamantyl-1,2,4-triazole, 4-adamantylpyrazole, and 4-adamantyl-3,5-dimethylpyrazole were synthesized and structurally characterized. These complexes are first examples of coordination compounds of azolyladamantanes.
- Pavlov, D. I.,Potapov, A. S.,Sukhikh, T. S.
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p. 1953 - 1964
(2020/11/07)
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- Synthesis of Trialkylamines with Extreme Steric Hindrance and Their Decay by a Hofmann-like Elimination Reaction
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A number of amines with three bulky alkyl groups at the nitrogen, which surpass the steric crowding of triisopropylamine considerably, were prepared by using different synthetic methods. It turned out that treatment of N-chlorodialkylamines with organometallic compounds, for example, Grignard reagents, in the presence of a major excess of tetramethylenediamine offered the most effective access to the target compounds. The limits of this method were also tested. The trialkylamines underwent a dealkylation reaction, depending on the degree of steric stress, even at ambient temperature. Because olefins were formed in this transformation, it showed some similarity with the Hofmann elimination. However, the thermal decay of sterically overcrowded tertiary amines was not promoted by bases. Instead, this reaction was strongly accelerated by protic conditions and even by trace amounts of water. Reaction mechanisms, which were analyzed with the help of quantum chemical calculations, are suggested to explain the experimental results.
- Banert, Klaus,Hagedorn, Manfred,Heck, Manuel,Hertel, Raphael,Ihle, Andreas,Müller, Ioana,Pester, Tom,Shoker, Tharallah,Rablen, Paul R.
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p. 13630 - 13643
(2020/11/13)
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- Chemoselectivity of Nitroxylation of Cage Hydrocarbons
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Abstract: The composition of reaction mixtures obtained by nitroxylation of 13 cage hydrocarbons with 100% nitric acid and its mixtures with acetic acid, acetic anhydride, and methylene chloride has been studied. More reactive substrates react with lowest
- Ivleva, E. A.,Klimochkin, Yu. N.,Leonova, M. V.
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p. 1702 - 1710
(2020/12/01)
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- Highly Selective and Catalytic Oxygenations of C?H and C=C Bonds by a Mononuclear Nonheme High-Spin Iron(III)-Alkylperoxo Species
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The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [FeIII(t-BuLUrea)(OOCm)(OH2)]2+(2), generated from [FeII(t-BuLUrea)(H2O)(OTf)](OTf) (1) [t-BuLUrea=1,1′-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C?H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C?H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O?O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.
- Ghosh, Ivy,Banerjee, Sridhar,Paul, Satadal,Corona, Teresa,Paine, Tapan Kanti
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p. 12534 - 12539
(2019/08/07)
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- New copper(II) coordination compounds assembled from multifunctional pyridine-carboxylate blocks: Synthesis, structures, and catalytic activity in cycloalkane oxidation
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Two new copper(II) coordination compounds, namely a 1D coordination polymer [Cu(μ-cpna)(phen)(H2O)]n (1) and a discrete tetracopper(II) derivative [Cu(phen)2(H2O)]2[Cu2(μ-Hdppa)2(Hdppa)2] (2), were hydrothermally synthesized from copper(II) chloride as a metal source, 5-(4-carboxyphenoxy)nicotinic acid (H2cpna) or 5-(3,4-dicarboxylphenyl)picolinic acid (H3dppa) as a principal building block, and 1,10-phenanthroline (phen) as a crystallization mediator. Compounds 1 and 2 were isolated as air-stable microcrystalline solids and fully characterized by elemental and thermogravimetric analyses, IR spectroscopy, powder and single-crystal X-ray diffraction. In the solid state, the structure of 1 discloses the linear interdigitated 1D coordination polymer chains with the 2C1 topology. The crystal structure of an ionic derivative 2 shows that the mono-and dicopper(II) units are extended into the intricate 1D hydrogen-bonded chains with the SP 1-periodic net (4,4)(0,2) topology. Thermal stability and catalytic properties of 1 and 2 were also investigated. In fact, both Cu derivatives act as efficient homogeneous catalysts (catalyst precursors) for the mild oxidation of cycloalkanes by hydrogen peroxide to give the corresponding alcohols and ketones; the substrate scope and the effects of type and amount of acid promoter as well as bond-, regio-, and stereo-selectivity features were investigated.
- Zhao, Na,Li, Yu,Gu, Jinzhong,Fernandes, Tiago A.,Kirillova, Marina V.,Kirillov, Alexander M.
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supporting information
(2019/01/14)
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- Ruthenium Aqua Complexes Supported by the Kl?ui Tripodal Ligand: Synthesis, Structure, and Application in Catalytic C–H Oxidation in Water
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Water-soluble ruthenium(III) aqua complexes supported by the Kl?ui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]– (LOEt–) have been synthesized and structurally characterized, and their use as catalysts for C–H oxidation in water has been studied. The treatment of [Ru(LOEt)Cl2(MeCN)] with N-donor ligands afforded the adducts [Ru(LOEt)Cl2(L)] (L = tBuNH2 (1), pyridine (2), imidazole (3)). Refluxing [Ru(LOEt)Cl2(MeCN)] in neat tBuNH2 gave the amidine complex [Ru(LOEt)Cl2{N(H)C(Me)NHtBu}] (4). Chloride abstraction of 1–3 with AgOTs (OTs = tosylate) in 1 M p-toluenesulfonic acid afforded the water-soluble RuIII diaqua complexes [Ru(LOEt)(H2O)2(L)](OTs)2 (L= tBuNH2 (5), pyridine (6), imidazole (7)), whereas that for 4 yielded the triaqua complex [Ru(LOEt)(H2O)3](OTs)2 (8). The crystal structures of 4, 5, 7, and 8 have been determined. The reduction of 5 with Zn dust in D2O gave a diamagnetic RuII species, whereas that in MeCN led to isolation of the RuII acetonitrile complex [RuII(LOEt)(MeCN)2(tBuNH2)](PF6) (9), which has been characterized by X-ray diffraction. The RuIII aqua complexes proved to be moderately efficient catalysts for C–H bond oxidation with tert-butyl hydroperoxide in water. For example, the oxidation of ethylbenzene with tert-butyl hydroperoxide in water at room temperature in the presence of 0.1 mol-% of 8 afforded acetophenone in ca. 62 % yield.
- So, Yat-Ming,Wong, Kang-Long,Sung, Herman H. Y.,Williams, Ian D.,Leung, Wa-Hung
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p. 2368 - 2374
(2019/05/15)
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- Direct Oxidation of Csp3?H bonds using in Situ Generated Trifluoromethylated Dioxirane in Flow
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A fast, scalable, and safer Csp3?H oxidation of activated and un-activated aliphatic chains can be enabled by methyl(trifluoromethyl)dioxirane (TFDO). The continuous flow platform allows the in situ generation of TFDO gas and its rapid reactivity toward tertiary and benzylic Csp3?H bonds. The process exhibits a broad scope and good functional group compatibility (28 examples, 8–99 %). The scalability of this methodology is demonstrated on 2.5 g scale oxidation of adamantane.
- Lesieur, Mathieu,Battilocchio, Claudio,Labes, Ricardo,Jacq, Jér?me,Genicot, Christophe,Ley, Steven V.,Pasau, Patrick
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supporting information
p. 1203 - 1207
(2019/01/04)
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- 2-Iodoxybenzoic acid ditriflate: The most powerful hypervalent iodine(v) oxidant
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A ditriflate derivative of 2-iodoxybenzoic acid (IBX) was prepared by the reaction of IBX with trifluoromethanesulfonic acid and characterized by single crystal X-ray crystallography. IBX-ditriflate is the most powerful oxidant in a series of structurally similar IBX derivatives which is best illustrated by its ability to readily oxidize hydrocarbons and the oxidation resistant polyfluoroalcohols.
- Yusubov, Mekhman S.,Soldatova, Natalia S.,Postnikov, Pavel S.,Valiev, Rashid R.,Yoshimura, Akira,Wirth, Thomas,Nemykin, Victor N.,Zhdankin, Viktor V.
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supporting information
p. 7760 - 7763
(2019/07/12)
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- Synthesis, structural characterization and C–H activation property of a tetra-iron(III) cluster
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A non-heme tetra-iron cluster, [Fe4 III(μ-O)2(μ-OAc)6(2,2′-bpy)2(H2O)2](NO3 ?)(OH?) (1), [OAc = acetate; 2,2′-bpy = 2,2′-bipyridine] containing oxido- and acetato-bridges was synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray diffraction studies. X-ray crystal structure analysis of 1 revealed that tetra-iron complex was crystallized in monoclinic system with C2/c space group. Each of the Fe centres in 1 was found to exist in octahedral geometry and interconnected by oxido- and acetato-bridges. Bond valence sum (BVS) calculation recommended the existence of iron centres in +3 oxidation state. Variable temperature magnetic measurement authenticated the dominating antiferromagnetic ordering among the iron centres in the solid state of 1. This tetra-iron cluster was also evaluated as an efficient catalytic system towards the oxidation of both linear & cyclic alkanes without production of primary C–H bond oxidation products. Oxidation of secondary C–H bonds attested the formation of both the corresponding alcohols & ketones in 27–900 TONs. The tetra-iron catalytic system with Alcohol/Ketone values 0.2–1.7 indicated the involvement of freely diffusing carbon-centered radicals rather than metal based oxidant.
- Dey, Dhananjay,Patra, Moumita,Al-Hunaiti, Afnan,Yadav, Hare Ram,Al-mherat, Afrah,Arar, Sharif,Maji, Milan,Choudhury, Angshuman Roy,Biswas, Bhaskar
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p. 220 - 226
(2019/01/05)
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- Novel memantine analogue and synthesis method thereof
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The invention provides a novel memantine analogue and salts thereof. The structure of the memantine analogue is expressed as a formula I which is as shown in description. The invention also disclosesa synthesis method of the compound expressed as the formula I. The novel memantine analogue has better activity; the novel memantine analogue is more beneficial to clinical application and further development and research of the medicines.
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- A practical innovative method for highly selective oxidation of alkenes and alkanes using Fe (III) and Mn (III) porphyrins supported onto multi-wall carbon nanotubes as reusable heterogeneous catalysts
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Functionalized multi-walled carbon nanotubes were used for covalent immobilization of meso-tetrakis(4-carboxyphenyl) porphyrinatoiron (III) chloride [Fe (TCPP)Cl] and meso-tetrakis(4-carboxyphenyl) porphyrinatomanganese (III) acetate [Mn (TCPP)OAc]. The full characterization of the hybrid porphyrinic nanomaterials, by Fourier transform-infrared and UV–Vis spectroscopy, transmission electron microscopy, thermogravimetry and flame atomic absorption spectrometry is described. The oxidation of alkenes and alkanes with molecular oxygen as green oxidant in the presence of Mn- and Fe-catalysts has been studied in a comparative manner. The Fe-catalyst was shown to have higher catalytic activity compared with the Mn-catalyst. In addition, both separable solid catalysts can be recovered and reused at least 10 times along with good yields.
- Rayati, Saeed,Nafarieh, Parinaz
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- Deuterated N2Py2 Ligands: Building More Robust Non-Heme Iron Oxidation Catalysts
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Fe(N2Py2)/H2O2/AcOH catalytic systems provide powerful tools for efficient C-H and C=C bond oxidations (N2Py2 = bis-alkylamine-bis-pyridine ligand). Yet, the stability of these catalysts under the oxidizing conditions still remains a problem. The generally accepted catalyst decomposition pathway of Fe(N2Py2) complexes is through oxidative dimerization to form inactive oxo-bridged Fe2(μ-O)(N2Py2)2 dimers. Detailed ESI-MS analysis has now shown a catalyst decomposition pathway of ligand oxidation via C-H oxidation on the 2-pyridinylmethylene sites, followed by dissociation of the oxidized ligand from the iron center. By deuterating the 2-pyridinylmethylene sites of a series of N2Py2 ligands with variations on both alkylamine and pyridine fragments, providing access to the corresponding Fe(N2Py2-D4) complexes, longer catalysts lifetimes are achieved in catalytic oxidation reactions with all complexes. As a consequence, improved substrate conversions and product yields were consistently observed in both aliphatic C-H oxidations and alkene epoxidations. Kinetic and catalytic studies revealed that deuteration does not change the intrinsic reactivity and product selectivity of Fe(N2Py2) complexes. In addition, different Fe(N2Py2-D4) complexes provide different improvements in catalytic performances and lifetimes, responding to the differences in ligand rigidity and robustness of the corresponding nondeuterated N2Py2 ligands. Accordingly, these improvements are more pronounced for ligands with a more flexible bis-alkylamine backbone. These observations provide insights into the development of more robust ligands for homogeneous oxidation catalysis.
- Chen, Jianming,Klein Gebbink, Robertus J.M.
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p. 3564 - 3575
(2019/04/01)
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- Selective One-Step Aerobic Oxidation of Cyclohexane to ?-Caprolactone Mediated by N-Hydroxyphthalimide (NHPI)
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The selective one-step aerobic oxidation of cyclohexane to ?-caprolactone was achieved in the presence of N-hydroxyphthalimide (NHPI) and aldehyde under mild conditions. Remarkably, 12 % of cyclohexane was converted with a selectivity of 77 % of ?-caprolactone and 15 % of KA oil. Control experiments indicated that NHPI accelerated the oxidation of aldehydes and peroxy radicals generated from aldehydes in situ were the key intermediates in the period of CH bond activation. 2,2,6,6-Tetramethylpiperidine 1-oxyl (TEMPO) addition and a series of m-chloroperoxybenzoic acid (m-CPBA) oxidation experiments showed that the oxidation proceeded via a complex radical chain mechanism.
- Wang, Lingyao,Zhang, Yuanbin,Du, Renfeng,Yuan, Haoran,Wang, Yongtao,Yao, Jia,Li, Haoran
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p. 2260 - 2264
(2019/04/10)
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- The Role of Iodanyl Radicals as Critical Chain Carriers in Aerobic Hypervalent Iodine Chemistry
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Selective O2 utilization remains a substantial challenge in synthetic chemistry. Biological small-molecule oxidation reactions often utilize aerobically generated high-valent catalyst intermediates to effect substrate oxidation. Available synthetic methods for aerobic oxidation catalysis are largely limited to substrate functionalization chemistry by low-valent catalyst intermediates (i.e., aerobically generated Pd(II) intermediates). Motivated by the need for new chemical platforms for aerobic oxidation catalysis, we recently developed aerobic hypervalent iodine chemistry. Here, we report that in contrast to the canonical two-electron oxidation mechanisms for the oxidation of organoiodides, the developed aerobic hypervalent iodine chemistry proceeds via a radical chain mechanism initiated by the addition of aerobically generated acetoxy radicals to aryl iodides. Despite the radical chain mechanism, aerobic hypervalent iodine chemistry displays substrate tolerance similar to that observed with traditional terminal oxidants, such as peracids. We anticipate that these insights will enable new sustainable oxidation chemistry via hypervalent iodine intermediates. O2 is routinely utilized in biological catalysis to generate high-valent catalyst intermediates that engage in substrate oxidation chemistry. Analogous synthetic chemistry via aerobically generated high-valent intermediates would enable new sustainable synthetic methods but is largely unknown because of the challenges in selective O2 utilization. We have developed aerobic hypervalent iodine chemistry as a platform for coupling O2 reduction with a diverse set of substrate functionalization mechanisms. Many of the synthetic applications of hypervalent iodine reagents rely on selective two-electron oxidation-reduction chemistry. Here, we report that one-electron oxidation reactions pathways via iodanyl radical intermediates are critical in aerobic hypervalent iodine chemistry. The new appreciation for the critical role that iodanyl radicals can play in the synthesis of hypervalent iodine compounds will provide new opportunities in sustainable oxidation catalysis. Aerobic hypervalent iodine chemistry provides a strategy for coupling the one-electron chemistry of O2 with two-electron processes typical of organic synthesis. We show that in contrast to the canonical two-electron oxidation of aryl iodides, aerobic synthesis proceeds by a radical chain process initiated by the addition of aerobically generated acetoxy radicals to aryliodides to generate iodanyl radicals. Robustness analysis reveals that the developed aerobic oxidation chemistry displays substrate tolerance similar to that observed in peracid-based methods and thus holds promise as a sustainable synthetic method.
- Hyun, Sung-Min,Yuan, Mingbin,Maity, Asim,Gutierrez, Osvaldo,Powers, David C.
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supporting information
p. 2388 - 2404
(2019/09/12)
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- Synthesis, crystal structure and immobilization of a new cobalt(ii) complex with a 2,4,6-tris(2-pyridyl)-1,3,5-triazine ligand on modified magnetic nanoparticles as a catalyst for the oxidation of alkanes
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A new Co(ii) complex with formula [Co(tptz)Cl2]·2H2O (tptz = 2,4,6-tris(2-pyridyl)-1,3,5-triazine) has been synthesized and characterized by X-ray crystallography, elemental analyses and spectroscopic methods. It was then supported on modified Fe3O4 nanoparticles using tetraethylorthosilicate (TEOS) and (3-aminopropyl)trimethoxysilane (APTMS) and designated as a Fe3O4@SiO2@APTMS@complex nanocatalyst. The prepared nanocatalyst was characterized by means of FT-IR, Raman, XPS, EDX, XRD, VSM, SEM and TEM studies. The catalytic activity of the [Co(tptz)Cl2]·2H2O complex and Fe3O4@SiO2@APTMS@complex designated as catalysts A and B was used for oxidation of activated secondary alkanes such as fluorene, diphenyl methane, ethylbenzene, cyclooctane and adamantane. Observation of 39-99% conversions and 27-100% selectivities toward the corresponding ketones as well as the heterogeneity and reusability of the catalyst B seem promising.
- Azarkamanzad, Zahra,Farzaneh, Faezeh,Maghami, Mahboobeh,Simpson, Jim
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p. 12020 - 12031
(2019/08/07)
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- Iron-catalyzed oxidative functionalization of C(sp3)-H bonds under bromide-synergized mild conditions
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An efficient oxidation and functionalization of C-H bonds with an inorganic-ligand supported iron catalyst and hydrogen peroxide to prepare the corresponding ketones was achieved using the bromide ion as a promoter. Preliminary mechanistic investigations indicated that the bromide ion can bind to FeMo6 to form a supramolecular species (FeMo6·2Br), which can effectively catalyze the reaction.
- Yu, Han,Zhao, Qixin,Wei, Zheyu,Wu, Zhikang,Li, Qi,Han, Sheng,Wei, Yongge
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supporting information
p. 7840 - 7843
(2019/07/12)
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- DMSO-Triggered Complete Oxygen Transfer Leading to Accelerated Aqueous Hydrolysis of Organohalides under Mild Conditions
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Addition of DMSO is found to greatly accelerate the aqueous hydrolysis of organohalides to alcohols, providing a neutral, more efficient, milder and more economic process. Mechanistic studies using 18O-DMSO and 18O-H2O showed that, contrary to the opinion that DMSO works as a dipolar solvent to enhance water's nucleophilicity, the accelerating effect comes from a complete oxygen transfer from DMSO to organohalides through generation of ROS+Me2?X? salts through C?O bond formation, followed by O?S bond disassociative hydrolysis of ROS+Me2?X? with water. This method is applicable to a wide range of organohalides and thus may have potential for practical industrial application, owing to easy recovery of DMSO from the H2O/DMSO mixture by regular vacuum rectification.
- Liu, Haicheng,Liu, Jianping,Cheng, Xiaokai,Jia, Xiaojuan,Yu, Lei,Xu, Qing
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p. 2994 - 2998
(2019/01/04)
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- Nanoporous Na+-montmorillonite perchloric acid as an efficient and recyclable catalyst for the chemoselective protection of hydroxyl groups
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Nanoporous Na+-montmorillonite perchloric acid as a novel heterogeneous reusable solid acid catalyst was easily prepared by treatment of Na+-montmorillonite as a cheap and commercially available support with perchloric acid. The catalyst was characterized using a variety of techniques including X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), pH analysis and determination of the Hammett acidity function. The prepared reagent showed excellent catalytic activity for the chemoselective conversion of alcohols and phenols to their corresponding trimethylsilyl ethers with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) at room temperature. Deprotection of the resulting trimethylsilyl ethers can also be carried out using the same catalyst in ethanol. All reactions were performed under mild and completely heterogeneous reaction conditions in good to excellent yields. The notable advantages of this protocol are: short reaction times, high yields, availability and low cost of the reagent, easy work-up procedure and the reusability of the catalyst during a simple filtration.
- Mashhadinezhad, Maryam,Shirini, Farhad,Mamaghani, Manouchehr
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p. 2099 - 2107
(2019/01/03)
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- Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: Straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts
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Adamantyloxyamine reacts with formaldehyde to give N-(adamantyloxy)formaldimine as a room-temperature-stable compound that exists in solution in monomeric form. This product was used for reactions with α-hydroxyiminoketones leading to a new class of 2-unsubstituted imidazole 3-oxides bearing the adamantyloxy substituent at N(1). Their reactions with 2,2,4,4-tetramethylcy-clobutane-1,3-dithione or with acetic acid anhydride occurred analogously to those of 1-alkylimidazole 3-oxides to give imidazol-2-thiones and imidazol-2-ones, respectively. Treatment of 1-(adamantyloxy)imidazole 3-oxides with Raney-Ni afforded the corresponding imidazole derivatives without cleavage of the N(1)–O bond. Finally, the O-alkylation reactions of the new imidazole N-oxides with 1-bromopentane or 1-bromododecane open access to diversely substituted, non-symmetric 1,3-dialkoxyimidazolium salts. Adamantyloxyamine reacts with glyoxal and formaldehyde in the presence of hydrobromic acid yielding symmetric 1,3-di(adamantyloxy)-1H-imidazolium bromide in good yield. Deprotonation of the latter with triethylamine in the presence of elemental sulfur allows the in situ generation of the corresponding imidazol-2-ylidene, which traps elemental sulfur yielding a 1,3-dihydro-2H-imidazole-2-thione as the final product.
- Mlostoń, Grzegorz,Celeda, Ma?gorzata,Urbaniak, Katarzyna,Jasiński, Marcin,Bakhonsky, Vladyslav,Schreiner, Peter R.,Heimgartner, Heinz
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supporting information
p. 497 - 505
(2019/03/08)
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- Oxidative Deprotection of p-Methoxybenzyl Ethers via Metal-Free Photoredox Catalysis
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An efficient and greener deprotection method for p-methoxybenzyl (PMB) ethers using a metal-free visible light photoredox catalyst and air and ammonium persulfate as the terminal oxidants is presented. Various functional groups and protecting groups were tolerated in the developed method to achieve good to excellent yields in short reaction times. Significantly, the developed method was compatible with PMB ethers derived from primary, secondary, and tertiary alcohols and a gram-scale reaction. Mechanistic studies support a proposed reaction mechanism that involves single electron oxidation of the PMB ether.
- Ahn, Deok Kyun,Kang, Young Woo,Woo, Sang Kook
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p. 3612 - 3623
(2019/03/11)
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- Dehydroxymethylation of alcohols enabled by cerium photocatalysis
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Dehydroxymethylation, the direct conversion of alcohol feedstocks as alkyl synthons containing one less carbon atom, is an unconventional and underexplored strategy to exploit the ubiquity and robustness of alcohol materials. Under mild and redox-neutral reaction conditions, utilizing inexpensive cerium catalyst, the photocatalytic dehydroxymethylation platform has been furnished. Enabled by ligand-to-metal charge transfer catalysis, an alcohol functionality has been reliably transferred into nucleophilic radicals with the loss of one molecule of formaldehyde. Intriguingly, we found that the dehydroxymethylation process can be significantly promoted by the cerium catalyst, and the stabilization effect of the fragmented radicals also plays a significant role. This operationally simple protocol has enabled the direct utilization of primary alcohols as unconventional alkyl nucleophiles for radical-mediated 1,4-conjugate additions with Michael acceptors. A broad range of alcohols, from simple ethanol to complex nucleosides and steroids, have been successfully applied to this fragment coupling transformation. Furthermore, the modularity of this catalytic system has been demonstrated in diversified radical-mediated transformations including hydrogenation, amination, alkenylation, and oxidation.
- Zhang, Kaining,Chang, Liang,An, Qing,Wang, Xin,Zuo, Zhiwei
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supporting information
p. 10556 - 10564
(2019/08/20)
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- Dehydroxymethylation of Alcohols Enabled by Cerium Photocatalysis
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Dehydroxymethylation, the direct conversion of alcohol feedstocks as alkyl synthons containing one less carbon atom, is an unconventional and underexplored strategy to exploit the ubiquity and robustness of alcohol materials. Under mild and redox-neutral reaction conditions, utilizing inexpensive cerium catalyst, the photocatalytic dehydroxymethylation platform has been furnished. Enabled by ligand-to-metal charge transfer catalysis, an alcohol functionality has been reliably transferred into nucleophilic radicals with the loss of one molecule of formaldehyde. Intriguingly, we found that the dehydroxymethylation process can be significantly promoted by the cerium catalyst, and the stabilization effect of the fragmented radicals also plays a significant role. This operationally simple protocol has enabled the direct utilization of primary alcohols as unconventional alkyl nucleophiles for radical-mediated 1,4-conjugate additions with Michael acceptors. A broad range of alcohols, from simple ethanol to complex nucleosides and steroids, have been successfully applied to this fragment coupling transformation. Furthermore, the modularity of this catalytic system has been demonstrated in diversified radical-mediated transformations including hydrogenation, amination, alkenylation, and oxidation.
- Zhang, Kaining,Chang, Liang,An, Qing,Wang, Xin,Zuo, Zhiwei
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supporting information
p. 10556 - 10564
(2019/08/28)
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