- Synergistic Activities in the Ullmann Coupling of Chloroarenes at Ambient Temperature by Pd-Supported Calcined Ferrocenated La2O3
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Novel palladium-doped nanoparticles have been explored to serve as the first metal oxide-derived heterogeneous catalyst for Ullmann reaction of chloroarenes under mild condition (34?°C). This heterogeneous catalyst exhibited high catalytic activity towards the Ullmann homocoupling of chloroarenes into a series of useful symmetrically biaryl products with good to excellent yields in the presence of ethanol and NaOH, thereby leading to green and economical Ullmann reaction. The produced nanoparticles were successfully characterized by various techniques including PXRD, XPS, HRTEM, SEM-EDS, BET, TGA techniques, elemental mapping analysis and ICP-OES. Interestingly, based on characterization and experimental data, a reasonable mechanism has been proposed. Also, the formation of aryl methyl ketone as a by-product has been further confirmed by isotopic labelling experiments that the acetyl moiety is derived from ethanol. Moreover, the catalyst was stable and could be easily reused up to 5 times under atmospheric air without suffering significant loss in catalytic activity.
- Chumkaeo, Peerapong,Poonsawat, Thinnaphat,Meechai, Titiya,Somsook, Ekasith
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- Dechlorination of pentachlorophenol and 1,2,4-trichlorobenzene using NaBH4 and NaBH4/LiCl at 125-315°C in glyme solvents
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Dechlorinations of pentachlorophenol and 1,2,4-trichlorobenzene were achieved using NaBH4 in tetraglyme at 290-315°C and by NaBH4/LiCl at 125-135°C in diglyme, triglyme or tetraglyme after premixing at room temperature.
- Yang, Cangming,Pittman Jr., Charles U.
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- A Zn4L6 Capsule with Enhanced Catalytic C?C Bond Formation Activity upon C60 Binding
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A redox-switchable self-assembled ZnII4L6 cage was synthesized that contains naphthalenediimide (NDI) motifs. Its reduction lent these NDI panels persistent radical anion character. The redox activity of this cage allows it to act as a catalyst for the oxidative coupling of different tetraaryl borates to give biaryls. The catalytic activity of the cage was enhanced following its binding of C60, which implies a mechanism that does not involve encapsulation of the substrate.
- Lu, Zhenpin,Lavendomme, Roy,Burghaus, Olaf,Nitschke, Jonathan R.
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- Kinetics and mechanism of the gas phase reaction of Cl atoms and OH radicals with bromobenzene
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Relative rate techniques were used to study the kinetics and mechanism of the reaction of Cl atoms and OH radicals with bromobenzene (C6H5Br) in 20-700 Torr of N2, O2, or air diluent at 295 ± 2 K. Using the observed rate constant ratios k(C6H5Br+Cl) /k(C2H5Cl+Cl) = 1.56 ± 0.05 and k(C6H5Br+Cl)/k(C2H6+Cl) = 0.24 ± 0.01, the C6H5Br+Cl rate constant is determined to be k(C6H5Br+Cl) = (1.32 ± 0.20) × 10-11 cm3 molecule-1 S-1 giving exclusively C6H5Cl through a displacement mechanism. Using the observed rate constant ratios k(C6H5Br+OH)/ k(C6H6 + OH) = 0.77 ± 0.06 and k(C6H5Br+OH)/k(C2H4+OH) = 0.11 ± 0.004, the C6H5Br + OH rate constant is determined to be k(C6H5Br+OH) = (9.37±2.04) × 10-13 cm3 molecule-1 s-1. The product expected from a displacement mechanism, phenol, was not observed (10% yield).
- Nakano,Kawasaki,Ponomarev,Hurley,Wallington
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- Alkane oxidation by an immobilized nickel complex catalyst: Structural and reactivity differences induced by surface-ligand density on mesoporous silica
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Immobilized nickel catalysts SBA*-L-x/Ni (L=bis(2-pyridylmethyl)(1H- 1,2,3-triazol-4-ylmethyl)amine) with various ligand densities (L content (x)=0.5, 1, 2, 4 mol % Si) have been prepared from azidopropyl-functionalized mesoporous silicas SBA-N3/sub
- Nakazawa, Jun,Hori, Tomoaki,Stack, T. Daniel P.,Hikichi, Shiro
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- Kinetic study of the reactions of chlorine atoms and Cl2·- radical anions in aqueous : Solutions. 1. Reaction with benzene
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The photolysis of NaS2O8 aqueous solutions containing Cl- ions is a clean technique for kinetic studies of the species Cl./Cl2.- in the presence and absence of added aromatic substrates. Laser and conventional flash-photolysis methods were used to study the aqueous phase reactions of chlorine atoms and Cl2.- (340 nm) radical ions in the presence and absence of benzene. A mechanism that considers the decay of Cl2.- in aqueous solutions with chloride ion concentrations from 1 x 10-4 to 0.6 M, total radical (Cl. + Cl2.-) concentrations at (0.1-1.5) x 10-5 M, and 2.5-3 pH was proposed. Kinetic computer simulations supported interpretation of the experimental data. The rate constants 6 x 109/M-sec ≤ k ≤ 1.2 x 1010/M-sec and 5/M-sec were determined for the reactions of Cl. and Cl2.-, respectively, in the aqueous phase. The organic radicals produced from these reactions showed an absorption band with maximum at 300 nm that was assigned to a Cl-cyclohexadienyl radical (Cl-CHD). The kinetic analysis of the traces supported a reversible reaction between Cl-CHD and O2. A reaction mechanism leading to the formation of chlorobenzene was proposed.
- Martire,Bertolotti,Braun,Gonzalez,Alegre,Gerones,Rosso
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- Application of a dioxo-molybdenum(VI) complex anchored on TiO2 for the photochemical oxidative decomposition of 1-chloro-4-ethylbenzene under O2
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The catalytic activity of dioxo-molybdenum(VI)- dichloro[4,4'- dicarboxylato-2,2'-bipyridine] covalently anchored through the carboxylate function to the surface of TiO2 has been tested for the oxidative degradation of 1-chloro-4- ethylbenzene in MeCN solution under argon and UV irradiation (λ = 254 nm). After 4-5 h of photochemical reaction, the Mo complex was reoxidized in the presence of O2 in the dark, and then the reaction was continued under argon. The reaction proceeds by the intermediate formation of 40-chloroacetophenone that undergoes further decomposition to chlorobenzene, plus small amounts of oxygen-containing organochlorine compounds, CO2 and H2O. Similar results were obtained for the decomposition of 4'-chloroacetophenone under the same conditions, which also gave chlorobenzene as one of the main products. The ratio of [final product]/ [Mo complex] increases during the decomposition of 1-chloro-4-ethylbenzene (up to 350-400% for 30-35 h of reaction), which provides evidence of a catalytic process. The probable photochemical reactions are discussed. Springer Science+Business Media B.V. 2011.
- Bakhtchadjian, Robert,Tsarukyan, Samvel,Barrault, Joel,Martinez, Fernando O.,Tavadyan, Levon,Castellanos, Nelson J.
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- A ligand-free copper-catalyzed decarboxylative trifluoromethylation of aryliodides with sodium trifluoroacetate using Ag2O as a promoter
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A practical and ligand-free Cu-catalyzed decarboxylative trifluoromethylation of aryl iodides with sodium trifluoroacetate using Ag 2O as a promoter was reported. A variety of trifluoromethyl- substituted aromatics are synthesized in moderate to excellent yields and with wide functional-group tolerance under relatively mild reaction conditions. Georg Thieme Verlag Stuttgart · New York.
- Li, Yaming,Chen, Tao,Wang, Huifeng,Zhang, Rong,Jin, Kun,Wang, Xiuna,Duan, Chunying
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- Oxychlorination and combustion of propene on fly-ash. Formation of chlorinated benzenes, dibenzodioxines and mono- and dibenzofurans
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Heterogenous gas phase reactions of propene on fly ash in the presence of hydrochloric acid and air between 300-580 deg C have been investigated. At mild conditions only the formation of polychlorinated C1, C2 and C3 species takes place. At the high tempe
- Jarmohamed, W.,Mulder, P.
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- CONVERSION OF DIARYLIODONIUM SALTS TO ARYL FLUORIDES
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The preparation of aryl fluorides by the reaction of diaryliodonium salts with KF is discussed.Generally, best results were obtained when the salt Ar2I(1+)*X(1-) was heated with KF in the absence of solvent.The counterion, X(1-), must be non-nucleophilic.
- Puy, Michael van der
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- Transformation of chemical contaminants by biotic and abiotic processes in water and soil
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In contrast to biological processes, which can give rise to only a limited amount of transformation because of the biostability of many persistent organic chemicals, abiotic environmental factors (solar radiation) make an appreciable contribution to the transformation of these substances in the environment. In this context, abiotic transformation of organic chemicals should be investigated with particular consideration to the dynamic and catalytic effects due primarily to the state of the molecule and its interaction with the environment. Our investigation demonstrate that selected chemical substances can be degraded and mineralized within relatively short periods if irradiated with light of wavelenghts λ ≥ 290 nm. The present investigations deals with the fate of selected s-triazines in soil and under simulated solar light in the presence of TiO2 and soil suspension.
- Mansour,Feicht
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- CIDNP Studies of the Thermal Decomposition of Arylazo Aryl Sulfones
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1H and 13C-CIDNP spectra were obtained during the thermal decomposition of several arylazo aryl sulfones (Ar-N=N-SO2-Ar') in tetrachloroethylene or 1,1,2,2-tetrachloroethane at 100 deg C.An enhanced absorption from the C1 of the starting material, azo sulfone, was observed; this indicates that the decomposition of azo sulfone proceeds by means of one-bond fission.The formation of sulfones (ArSO2Ar') and sulfinic esters (ArO(SO)Ar') as recombination products in a solvent cage was established from the signs of polarization (enhanced absorption or emission).
- Yoshida, Masato,Furuta, Naoki,Kobayashi, Michio
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- Formation of complex organochlorine species in water due to cavitation
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Sonication at 900 kHz was carried out on aqueous solutions of chloroform in the concentration range 25 to 500 mg/L. The formation of chlorinated hydrocarbons was detected by means of GC/MS analyses. For instance, carbon tetrachloride, chlorinated ethanes, and chlorinated ethenes were formed after 10 min of sonication. The greatest concentration of any product was 6 mg/L. Sonication of aqueous chloroform with phenol present produced chlorophenols, and with benzene present produced phenol, chlorobenzene and chlorophenols. These results are significant for the evaluation of sonication as a method of eliminating chlorinated organic compounds from water. They also have significance in supporting the notion that some complex organochlorines may be formed naturally in the environment. Some chloroform and methyl chloride are produced in nature and could react with other organic compounds to form more complex organochlorines through natural processes which have an action similar to cavitation, e.g. waterfalls and breaking waves.
- Kruus, Peeter,Beutel, Lise,Aranda, Rocio,Penchuk, Jaan,Otson, Rein
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- Photocatalytic degradation of ciprofloxacin by synthesized TiO2 nanoparticles on montmorillonite: Effect of operation parameters and artificial neural network modeling
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TiO2/MMT nanocomposite was synthesized and characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray fluorescence (XRF) and Brunauer-Emmett-Teller (BET) techniques. The average size of TiO2 nanoparticles was decreased from 60-80 nm to 40-60 nm through the immobilization on MMT. The main influential factors such as the TiO2/MMT dose, ciprofloxacin (CIP) concentration, pH of the solution, UV light regions, reusability of the catalyst and electrical energy determination were studied. The addition of radical scavengers (e.g. chloride, iodide, sulfate and bicarbonate) and enhancers (e.g. hydrogen peroxide, potassium iodate and peroxydisulfate) on the degradation efficiency was studied. The predicted data from the designed artificial neural network model were found to be in a good agreement with the experimental data (R2 = 0.9864). The main intermediates of CIP degradation were determined by GC-Mass spectrometry.
- Hassani, Aydin,Khataee, Alireza,Karaca, Semra
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- Catalytic alkane oxidation by homogeneous and silica-supported cobalt(II) complex catalysts with a triazoly group-containing tetradentate ligand
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Homogeneous and heterogeneous cobalt complex catalysts with bis(pyridylmethyl)(triazolylmethyl)amine ligand were prepared. Although simple cobalt salts catalyze cyclohexane oxidation with mCPBA, the cyclohexane selectivity increases upon coordination of tetradentate ligands. In the heterogeneous catalysis, the yield and selectivity of cyclohexanol are improved with an increase in the ligand density on the silica support due to the suppression of metal leaching.
- Nakazawa, Jun,Yata, Akinori,Hori, Tomoaki,Stack, T. Daniel P.,Naruta, Yoshinori,Hikichi, Shiro
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- SUBSTITUTIVE AROMATIC FLUORINATION WITH CHLORINE PENTAFLUORIDE
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In contrast to limited substitutive fluorination of aromatics with halogen fluorides such as ClF, ClF3, BrF3 and IF5, fluorination is the predominant reaction path with ClF5.Under non-catalytic liquid phase conditions, benzene was converted to fluorobenzene (54percent yield) and chlorobenzene (37percent yield), respectively.For a heterocyclic substrate, i.e. 2,4,6-trifluoropyrimidine, sunstitutive fluorination predominated over chlorination.Three possible fluorination mechanisms are discussed.A transition complex of ClF5 with benzene is favored.Enhanced exchange fluorination of CCl4 was effected with ClF5 (CF2Cl2 >> CFCl3 > CF3Cl) as compared with ClF3 (CFCl3 >> CF2Cl2)
- Boudakian, Max M.,Hyde, Gene A.
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- Liquid-Phase Hydrogenation of Halobenzenes in the Presence of Palladium-Containing Nanodiamonds
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Abstract: The catalytic activity of palladium-containing nanodiamonds (Pd/ND) is studied in the model reaction of liquid-phase hydrodehalogenation of monohalobenzenes (chlorobenzene, bromobenzene, and iodobenzene) and ortho-, meta-, and para-isomers of dichlorobenzene under mild conditions (Т = 45°С, (Formula presented.)?= 1 atm). The obtained results are compared with the catalytic behavior of the palladium-containing activated carbon (Pd/C) under identical conditions. It is found that catalyst Pd/ND is more active than Pd/C and is more stable against the poisonous effect of hydrogen halide forming during the reaction. Study of the effect of HCl and NaOH additives on the catalyst activity shows that, in the presence of HCl, poisoning of the catalyst occurs: the rate of reaction decreases; in the presence of NaOH, the catalyst activity grows; the rate of reaction increases as a result of hydrogen chloride neutralization by an alkali. For both catalysts the rate of reaction decreases in the sequence Cl > Br > I for monohalobenzenes and in the sequence para- > ortho- > meta-isomer in the case of dichlorobenzenes. The obtained dependences are explained using the quantum-chemical modeling of substrates of model reactions.
- Kalmykov,Magdalinova,Klyuev
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- Oxidative radical arylation of anilines with arylhydrazines and dioxygen from air
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Substituted 2-aminobiphenyls have been prepared from arylhydrazine hydrochlorides and anilines in biphasic radical arylation reactions with dioxygen from air as a most simple and readily available oxidant. Under optimized conditions, the free amino functionality of the aniline leads to high ortho:meta regioselectivities, now even for anilines bearing a donor substituent in the para position. Finally, the mild and metal-free new access to aminobiphenyls was shown to be applicable on a gram scale.
- Hofmann, Josefa,Jasch, Hannelore,Heinrich, Markus R.
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- Dehalogenation of organic compounds. 4. Dechlorination of pentachlorophenol and 1,2,4-trichlorobenzene with transition metal-promoted alkoxyborohydrides
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Metal-promoted NaBH4 and NaBH2(OCH2CH2OCH2)2 dechlorinations were carried out on the aromatic chloro compounds pentachlorophenol and 1,2,4-trichlorobenzene. The best results were obtained by dropwise addition of NiCl2 in solution to NaBH2(OCH2CH2OCH3)2 and the substrate in THF solutions.
- Tabaei,H.,Pittman Jr.
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- Molecule-induced homolysis of N-hydroxyphthalimide (NHPI) by peracids and dioxirane. A new, simple, selective aerobic radical epoxidation of alkenes
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Evidences are reported concerning the molecule-induced homolysis of NHPI by peracids and dioxirane; their combination can be utilized for the aerobic free-radical epoxidation of alkenes with selectivity quite different from the well-known epoxidation by peracids.
- Minisci, Francesco,Gambarotti, Cristian,Pierini, Monica,Porta, Ombretta,Punta, Carlo,Recupero, Francesco,Lucarini, Marco,Mugnaini, Veronica
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- The influence of acid treatment of carbon nanofibers on the activity of palladium catalysts in the liquid-phase hydrodechlorination of dichlorobenzene
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Palladium catalysts on the basis of acid treated carbon nanofibers (CNF) were studied. Using physico-chemical methods of investigation (low-temperature nitrogen adsorption-desorption, FTIR spectroscopy and Boehm titration) it has been shown that under the action of HCl and HNO3 there take place a reduction in the specific surface area and the volume of pores and an increase of the concentration of surface functional groups. This has a substantial influence on the adsorptive properties of CNF, the dispersion of palladium and the catalytic activity in the liquid-phase hydrodechlorination of 1,2-dichlorobenzene. The reaction rate was observed to be the highest in the presence of Pd/CNF-HCl. Treatment of CNF by HCl gives the highest dispersion of palladium on the external surface of CNF. There is also an increase in the adsorption capacity for 1,2-dichlorobenzene and a decreased adsorption of the solvents on the surface of the acid-modified CNF.
- Netskina,Komova,Tayban,Oderova,Mukha,Kuvshinov,Simagina
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- Hazardous air pollutants formation from reactions of raw meal organics in cement kilns
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Thermally induced chlorination, condensation, and formation reactions of raw meal organic surrogates were investigated on different types of surfaces. The System for Thermal Diagnostic Studies provided a powerful tool to study these reactions under defined reaction conditions, which were related to typical conditions in the preheater zone of cement kiln. Experiments were conducted with benzene and benzene/myristic acid (C6H6/C13H27COOH) mixtures in a quartz reactor containing different chlorinating catalysts/reagents over a temperature range of 300-500°C. Reaction products were trapped in-line and analyzed by GC-MS. A mixture of chlorides of calcium, potassium, aluminium and iron was highly effective for chlorination/condensation reactions of benzene and benzene/myristic acid mix at temperatures above 300°C. The same behavior was observed only when calcium chloride and potassium chloride were used as chlorinating catalyst/reagent. This result showed that transition metal chlorides like FeCl3 are not necessary for chlorination/condensation of organics under post-combustion conditions. Methylene chloride was the major chlorinated product followed by chloroform and various other C1, C2 and C6 chlorinated products. Yields of chlorinated aliphatics were highest at 400°C for both benzene and benzene/myristic acid mix. C6 products were mainly mono- to hexa-chlorinated benzenes with trace amounts of chlorinated phenols. The major chlorinated products observed in this study (i.e., methylene chloride, chloroform, chloroethanes and monochlorobenzene) were also present as major chlorinated hydrocarbons in the cement kiln field emission data.
- Sidhu, Sukh,Kasti, Nabil,Edwards, Phil,Dellinger, Barry
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- Surface structure of bulk nickel catalysts, active in the gas-phase hydrodechlorination reaction of aromatics
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Several bulk nickel catalysts obtained from different procedures have been structurally characterized using BET, XRD, SEM, TPR and TPD techniques. XRD and SEM clearly show diffentiated crystalline morphologies on the oxidized and reduced nickel phases obtained from the three catalysts studied, in agreement with the BET surface areas. TPR and TPD results show the reducibility behaviour, and that mainly atomic hydrogen chemisorbs onto the catalysts with the better crystallized and larger nickel crystallites. The catalytic activities depicted by this study for the hydrodechlorination reaction of ortho-dichlorobenzene show that all the bulk nickel catalysts tested yield conversions and selectivities towards benzene of >80% at temperatures >493 K. Also, the catalysts with larger octahedral crystallites showed higher TOF values and selectivities toward benzene than those with poorly crystallized structures at any reaction temperature in the range 523-393 K. The behaviour is interpreted in terms of a structure-sensitive reaction. Also, a reversible/irreversible temperature-dependent mechanism of nickel chloride formation is proposed.
- Estelle, Joaquim,Ruz, Javier,Cesteros, Yolanda,Fernandez, Rosa,Salagre, Pilar,Medina, Francisco,Sueiras, Jesus-Eduardo
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- Synthesis and spectral properties of iron(III) tetra-tert-butylphthalocyanine complexes
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Two tetra-tert-butylphthalocyanine complexes of iron(III) were synthesized in high yields from the phthalocyanine ligand and iron(III) salts; the oxidation state of iron was confirmed by M?ssbauer and EPR spectroscopy. The existence of an acid–base equilibrium during spectrophotometric titration was revealed. The ButPcFeCl complex catalyzed chlorination of benzene.
- Burtsev, Ivan D.,Dubinina, Tatiana V.,Platonova, Yana B.,Kosov, Anton D.,Pankratov, Denis A.,Tomilova, Larisa G.
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- Reaction of Phenylchlorocarbene in Oxygen-Doped Matrices
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Irradiation of phenylchlorodiazirine at 10 K matrix isolated in argon gives phenylchlorocarbene.The carbene was characterized by IR, UV, and trapping with HCl.Warming an argon matrix containing O2 and the carbene to 35 K caused reaction to give the corresponding carbonyl oxide.The yellow-green (λmax 400nm) carbonyl oxide was characterized by IR, Uv, and 18O2 labeling.Photolysis of the carbonyl oxide with visible light gave the corresponding dioxirane, benzoyl chloride, and ozone.The dioxirane, which showed only absorption tailing into the visible, was characterized by IR, 18O2 labeling, and subsequent photochemistry.Irradiation of the dioxirane (λ>/=420 nm) gave mainly phenyl chloroformate and a small amount of chlorobenzene and CO2.Possible mechanism for the novel spin-forbidden O2 addition are discussed.
- Ganzer, Georg A.,Sheridan, Robert S.,Liu, Michael T. H.
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- Kinetics and mechanism of the reaction of Cl atoms with nitrobenzene
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The kinetics and mechanism of the reaction of Cl atoms with nitrobenzene in 10-700 torr of N2, or air, at 296 K were studied using smog chamber/FTIR methods. The reaction of Cl atoms with nitrobenzene proceeded with a rate constant of 9.3 × 10-13 cc/molecule-sec to give C6H5Cl and NO2 products in essentially 100% yield. The UV-visible spectrum of nitrobenzene was measured. The dominant atmospheric fate of nitrobenzene was photolysis, which occurred at a rate of 3 × 10-5/sec for a solar zenith angle of 25° representative of a typical summer day at 40°N.
- Froosig,Nielsen,Bilde,Wallington,Orlando,Tyndall
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- Reactions of diphenyl ether with chlorine and bromine atoms around 750 K - Relevance for gas-phase 'dioxin' formation
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The title reactions have been studied to scrutinize rate data recently inferred for the two reverse steps - reaction of phenoxy radicals with chlorobenzene and bromobenzene which were at variance with commonly accepted model values. Both with chlorine and bromine atoms, splitting to halobenzene and phenoxy radical was found to occur in competition with abstraction of o-, m-, p-hydrogen atoms. On this basis, the displacements of Cl and Br from the benzene ring by phenoxy radicals must have activation energies above 20 kcal/mol, and are therefore slow. As a consequence, formation of 'dioxins' from halogenated phenols, in (slow) combustion, should proceed by combination of two (halo)phenoxy radicals rather than by displacement of (ortho-)halogen in a halophenol molecule.
- Wiater, Izabela,Louw, Robert
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- DEHALOGENATION OF CHLOROARENES WITH SODIUM DIHYHDRIDOBIS(2-METHOXYETHOXO)ALUMINATE IN THE PRESENCE OF TRANSITION METAL COMPOUNDS
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Dehalogenation of low-chlorinated arenes such as p-dichlorobenzene of chlorobenzene with the title hydride is accelerated in the presence of transition metal species formed in situ from the corresponding 2,4-pentanedionates.Their efficiency decreases in the order: Co = Ni = Pd> Cu >> Mn > Fe which results from the changes of their activity and stability.The dehalogenation is well described by a kinetic model consisting of the set of dehalogenation steps which are first order in the chloroarene combined with the catalyst deactivation which is second order in the transition metal compound.
- Vcelak, Jaroslav,Hetflejs, Jiri
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- The importance of copper placement in chiral catalysts supported on heteropolyanions: Lacunary vs external exchanged
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Lacunary [PCuW11O39]5? species modified with chiral bis(oxazoline) leads to very poor results as catalyst in the enantioselective cyclopropanation, in contrast with the Cu-bis(oxazoline) complex exchanged on the Keggin [PW12O40]3? species. The incomplete neutralization and/or exchange of the Keggin species produces a loss in symmetry that leads to spectra in solid phase (IR and NMR) similar to those obtained for the lacunary species. The symmetry is averaged in solution, but additional characterization methods are necessary to determine the true nature of the solid heteropolyanionic species. These results demonstrate that the efficiency of copper-bis(oxazoline) complexes is related to its placement in an external exchange position, whereas the copper included in the heteropolyanion structure is not active for cyclopropanation reactions.
- Fraile, José M.,Mansilla, Daniela S.,Mayoral, José A.,Torviso, M. Rosario
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- Rate Constants for Hydrogen Atom Attack on Some Chlorinated Benzenes at High Temperatures
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Hydrogen atoms from the decomposition of hexamethylethane were reacted with chlorobenzene, o-dichlorobenzene, p-dichlorobenzene, and 1,2,3-trichlorobenzene in the presence of toluene or 1,3,5-trimethylbenzene in single-pulse shock tube experiments.Using the rate expression for the displacement of the methyl group from the methylated aromatics as standards we find k(H + C6H5Cl -> C6H6 + Cl) = (2.2E10) exp(-4531/T) L/(mol*s), k(H + o-C6H4Cl2 -> C6H5Cl + Cl) = (9.2E10) exp(-5196/T) L/(mol*s), k(H + p-C6H4Cl2 -> C6H5Cl + Cl) = (4.6E10) exp(-4541/T) L/(mol*s), k(H + 1,2,3-C6H3Cl3 -> o-C6H4Cl + Cl) = (1.9E10) exp(-2954/T) L/(mol*s), and k(H + 1,2,3-C6H3Cl3 -> m-C6H4Cl + Cl) = (3.7E9) exp(-1856/T) L/(mol*s) at temperatures of 1050-1150 K and pressures between 2.5 and 3.2 atm.In this temperature range the relative rate constants on a per-chlorine basis for the five processes are 1:1.15:1.05:1.8:2.4.The absolute uncertainty in the rate expressions are of the order of 8 kJ in the activation energy and a factor of 2.5 in the A factor.The relative rate constants have an uncertainty of no more than a factor of 1.1.Rate expressions for the reverse chlorination process have been calculated to be k(Cl + C6H6 -> C6H5Cl + H) = (4.7E10) exp(-13453/T) L/(mol*s), k(Cl + C6H5Cl -> o-C6H4Cl2 + H) = (2.9E10) exp(-15075/T) L/(mol*s), and k(Cl + C6H5Cl -> p-C6H4Cl2 + H) = (8.8E9) exp(-13614/T) L/mol*s.
- Cui, J. P.,He, Y. Z.,Tsang, W.
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- Iron-mediated desulphurization approach: synthesis of cyanamides and their conversions
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The iron-mediated efficient multi-component method has been demonstrated for the synthesis of substituted cyanamides from isothiocyanates under mild reaction conditions. Subsequent nucleophilic addition and desulfurization are involved in this proposed synthetic methodology. All the reactions are rapid, facile, and accomplished at room temperature. A variety of substrates readily underwent the optimized reaction conditions to provide their respective target products in good to excellent yields. Furthermore, we have confirmed that no other by-products could be identified during our experimental reaction process. Graphical abstract: Iron-mediated efficient multi-component method has been demonstrated for the synthesis of substituted cyanamides from isothiocyanates under mild reaction conditions. Subsequent nucleophilic addition and desulfurization are involved in this proposed synthetic methodology.[Figure not available: see fulltext.].
- Nannapaneni, Madhavi,Pendem, Venkata Bhavanarushi,Tamminana, Ramana
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- Research on the decomposition kinetics and thermal hazards of aniline diazonium salt
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Diazotization reaction, strong exothermic characteristics and thermal instability of diazonium salts make the production process high risk. To research thermal hazards of aniline diazonium salt, dynamic experiments are carried out by the differential scanning calorimeter (DSC) to obtain thermodynamic parameters. Moreover, the kinetic parameters are analyzed by Advanced Kinetics and Technology Solutions (AKTS) software. Finally, the GC-MS and UV spectrum are used to further study the decomposition mechanism of the aniline diazonium salt. The results indicate that aniline diazonium salt is very easy to decompose. When the heating rate is 2 K/min, the onset decomposition temperature is only 27.21 ℃ (Tonset). The apparent activation energy of the decomposition process calculated by Friedman and Ozawa methods are respectively 98-85 kJ/mol and 110-100 kJ/mol. Under the ideal adiabatic conditions (φ = 1), the initial temperatures of TMRad for 24 h is only 6.2 ℃ (TD24), which is predicted by the AKTS software. The decomposition process of aniline diazonium salt is inconsistent with a single reaction mechanism.
- Du, Lei,Wang, Ben,Xie, Chuanxin,Yuan, Yucan
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- Homogeneous oxidation of C–H bonds with m-CPBA catalysed by a Co/Fe system: mechanistic insights from the point of view of the oxidant
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Oxidations of C–H bonds with m-chloroperoxybenzoic acid (m-CPBA) catalyzed by transition metal complexes are known to proceed through a number of routes, from the non-selective free radical to selective concerted and metal-mediated ones. However, there is a lack of understanding of the m-CPBA oxidative behavior, reaction mechanisms and factors that trigger its activity. An experimental and theoretical investigation of sp3 C–H bond oxidation with m-CPBA in the presence of the heterometallic pre-catalyst [CoIII4FeIII2O(Sae)8]·4DMF·H2O (1) (H2Sae = salicylidene-2-ethanolamine) and HNO3 promoter has been performed herein. The catalytic system 1/HNO3/m-CPBA allows mild hydroxylation of tertiary C–H bonds with 99% retention of stereoconfiguration of model alkane substrates, supported by high TOFs up to 2 s?1 (for cis-1,2-dimethylcyclohexane) and TONs up to 1.4 × 104 (at 50 °C). The catalytic effect of 1 is seen at the ppm level, while 1000 ppm (0.1 mol%) loading allows 1000-fold increase of the initial reaction rate up to 9 × 10?5 M s?1. The reaction mechanism was investigated by means of combined kinetic studies (including isotope effects), isotopic labeling (18O2, H218O, D2O), ESI-MS spectroscopy and DFT theoretical studies. The results suggest that the main oxidation pathway proceeds through a concerted mechanism involving a cobalt-peroxo C–H attacking species or via a cobalt–oxyl species (rebound process), rather than a free-radical pathway. Remarkably, the Co(iii) catalyst does not change its oxidation state during the most energetically favored pathway, consistent with a metal–ligand cooperativity. The chlorobenzene radical is responsible for H abstraction in the non-selective side route, which is efficiently suppressed by the acidic promoter. Finally, signs for slow direct oxygen exchange between m-CPBA and water in the presence of a proton or a metal complex are found, suggesting that the results of 18O-tests should be treated cautiously when m-CPBA is used as the oxidant.
- Kuznetsov, Maxim L.,Nesterov, Dmytro S.,Nesterova, Oksana V.,Pombeiro, Armando J. L.,Shul'pin, Georgiy B.
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p. 282 - 299
(2022/01/19)
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- Silk?Fibroin-Supported Palladium Catalyst for Suzuki-Miyaura and Ullmann Coupling Reactions of Aryl Chlorides
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Recently, we have reported the preparation of a silk fibroin-supported Palladium catalyst (Pd/SF) and its use in the Suzuki-Miyaura cross-coupling of aryl iodides. Since its synthetic applicability and structural features are still far from being fully ex
- Albano, Gianluigi,Farinola, Gianluca M.,Giannini, Cinzia,Musio, Roberta,Omenetto, Fiorenzo G.,Rizzo, Giorgio,Sibillano, Teresa
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supporting information
(2022/02/03)
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- Efficient Pd(ii)-catalyzed regioselectiveortho-halogenation of arylcyanamides
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Regioselectiveortho-halogenation of arylcyanamides using a Pd(ii) catalyst has been established under mild reaction conditions. Either electron-donating or electron-withdrawing groups readily carried out the reaction and produced final products in moderate to good yields. Based on the experimental work, we have confirmed that this method does not undergo a free radical mechanism. Furthermore, we have also attempted this method for practical utility purposes.
- Alam, M. Mujahid,Boddapati, S. N. M.,Bollikolla, Hari Babu,Gugulothu, Sailaja,Tamminana, Ramana,Varala, Ravi
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supporting information
p. 17176 - 17182
(2021/10/04)
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- Photoredox-catalyzed reduction of halogenated arenes in water by amphiphilic polymeric nanoparticles
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The use of organic photoredox catalysts provides new ways to perform metal-free reactions controlled by light. While these reactions are usually performed in organic media, the application of these catalysts at ambient temperatures in aqueous media is of considerable interest. We here compare the activity of two established organic photoredox catalysts, one based on 10-phenylphenothiazine (PTH) and one based on an acridinium dye (ACR), in the light-activated dehalogenation of aromatic halides in pure water. Both PTH and ACR were covalently attached to amphiphilic polymers that are designed to form polymeric nanoparticles with hydrodynamic diameter DH ranging between 5 and 11 nm in aqueous solution. Due to the hydrophobic side groups that furnish the interior of these nanoparticles after hydrophobic collapse, water-insoluble reagents can gather within the nanoparticles at high local catalyst and substrate concentrations. We evaluated six different amphiphilic polymeric nanoparticles to assess the effect of polymer length, catalyst loading and nature of the catalyst (PTH or ACR) in the dechlorination of a range of aromatic chlorides. In addition, we investigate the selectivity of both catalysts for reducing different types of aryl-halogen bonds present in one molecule, as well as the activity of the catalysts for C-C cross-coupling reactions. We find that all polymer-based catalysts show high activity for the reduction of electron-poor aromatic compounds. For electron-rich compounds, the ACR-based catalyst is more effective than PTH. In the selective dehalogenation reactions, the order of bond stability is C-Cl > C-Br > C-I irrespective of the catalyst applied. All in all, both water-compatible systems show good activity in water, with ACR-based catalysts being slightly more efficient for more resilient substrates.
- Eisenreich, Fabian,Kuster, Tom H. R.,Palmans, Anja R. A.,van Krimpen, David
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supporting information
(2021/10/05)
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- The graphite-catalyzed: ipso -functionalization of arylboronic acids in an aqueous medium: metal-free access to phenols, anilines, nitroarenes, and haloarenes
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An efficient, metal-free, and sustainable strategy has been described for the ipso-functionalization of phenylboronic acids using air as an oxidant in an aqueous medium. A range of carbon materials has been tested as carbocatalysts. To our surprise, graphite was found to be the best catalyst in terms of the turnover frequency. A broad range of valuable substituted aromatic compounds, i.e., phenols, anilines, nitroarenes, and haloarenes, has been prepared via the functionalization of the C-B bond into C-N, C-O, and many other C-X bonds. The vital role of the aromatic π-conjugation system of graphite in this protocol has been established and was observed via numerous analytic techniques. The heterogeneous nature of graphite facilitates the high recyclability of the carbocatalyst. This effective and easy system provides a multipurpose approach for the production of valuable substituted aromatic compounds without using any metals, ligands, bases, or harsh oxidants.
- Badgoti, Ranveer Singh,Dandia, Anshu,Parewa, Vijay,Rathore, Kuldeep S.,Saini, Pratibha,Sharma, Ruchi
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p. 18040 - 18049
(2021/05/29)
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- METAL ORGANIC INTERACTIONS AT HYDROTHERMAL CONDITIONS
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Oxidizing a first aromatic compound in the presence of a metal salt to yield a second aromatic compound includes combining the first aromatic compound, the metal salt, and water to yield an aqueous mixture, and heating the aqueous mixture at a temperature exceeding 200° C. to yield a reaction product that includes the second aromatic compound.
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Paragraph 0043-0046
(2021/07/31)
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- New insight into the electrochemical reduction of different aryldiazonium salts in aqueous solutions
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Electrochemical reduction of different aryldiazonium salts in aqueous solution was studied in this work and it is shown that the aryldiazonium salts are converted to the corresponding aryl radical and aryl anion. The results of this research indicate that the reduction of aryldiazonium salts takes place in two single-electron steps. Our data show that when the substituted group on the phenyl ring is H, Cl, OH, NO2, OCH3or SO3?, the corresponding diazonium salt shows poor adsorption characteristics, but when the substituted group is methyl, the corresponding diazonium salt shows strong adsorption characteristics. In the latter case, the voltammogram exhibits three cathodic peaks. In addition, the effect of various substitutions on the aryldiazonium reduction was studied by Hammett's method. The data are show that with increasing electron withdrawing capacity of the substituent, the reduction of corresponding diazonium salt becomes easier.
- Goljani, Hamed,Nematollahi, Davood,Sepehrmansourie, Hassan,Tavakkoli, Zahra,Zolfigol, Mohammad Ali
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p. 25811 - 25815
(2021/08/09)
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- Aliphatic C–H hydroxylation activity and durability of a nickel complex catalyst according to the molecular structure of the bis(oxazoline) ligands
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Applicability of the oxazoline-based compounds, bis(2-oxazolynyl)methane (BOX) and 2,6-bis(2-oxazolynyl)pyridine (PyBOX), as supporting ligands of nickel(II) complexes for the catalysis of aliphatic C–H hydroxylation with m-CPBA (meta-chloroperoxybenzoic acid) was explored. Substituent groups at the fourth and fifth positions of oxazoline rings and the bridgehead carbon atom of the BOX derivatives affected the catalytic performances toward cyclohexane hydroxylation. Presence of dioxygen led to a reduced catalytic performance of the nickel complexes, except in the case of a fully substituted BOX ligand complex.
- Hikichi, Shiro,Izumi, Takashi,Matsuba, Naki,Nakazawa, Jun
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- Exploiting a silver-bismuth hybrid material as heterogeneous noble metal catalyst for decarboxylations and decarboxylative deuterations of carboxylic acids under batch and continuous flow conditions
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Herein, we report novel catalytic methodologies for protodecarboxylations and decarboxylative deuterations of carboxylic acids utilizing a silver-containing hybrid material as a heterogeneous noble metal catalyst. After an initial batch method development, a chemically intensified continuous flow process was established in a simple packed-bed system which enabled gram-scale protodecarboxlyations without detectable structural degradation of the catalyst. The scope and applicability of the batch and flow processes were demonstrated through decarboxylations of a diverse set of aromatic carboxylic acids. Catalytic decarboxylative deuterations were achieved on the basis of the reaction conditions developed for the protodecarboxylations using D2O as a readily available deuterium source.
- ?tv?s, Sándor B.,Fül?p, Ferenc,Kónya, Zoltán,Kukovecz, ákos,Márton, András,Mészáros, Rebeka,Pálinkó, István,Szabados, Márton,Varga, Gábor
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p. 4685 - 4696
(2021/07/12)
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- CO2-activated NaClO-5H2O enabled smooth oxygen transfer to iodoarene: A highly practical synthesis of iodosylarene
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A safe, rapid, and environmentally friendly synthesis of iodosylarene (ArIO) has been developed using NaClO under a carbon dioxide (CO2) atmosphere. Exposure of iodoarene to NaClO-5H2O in acetonitrile under CO2 (1 atm) resulted in the clean formation of ArIO within 10 minutes in high yield. The absence of a base in this method enables the direct use of in-situ-generated iodosylarene not only for a variety of oxidative transformations (synthesis of sulfilimine, pentavalent bismuth, benzyne adduct, etc.), but also for the synthesis of iodonium ylide and imino-λ3-iodane in one pot.
- Miyamoto, Kazunori,Watanabe, Yuichiro,Takagi, Taisei,Okada, Tomohide,Toyama, Takashi,Imamura, Shinji,Uchiyama, Masanobu
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supporting information
(2021/05/27)
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- Chromoselective Synthesis of Sulfonyl Chlorides and Sulfonamides with Potassium Poly(heptazine imide) Photocatalyst
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Among external stimuli used to promote a chemical reaction, photocatalysis possesses a unique one—light. Photons are traceless reagents that provide an exclusive opportunity to alter chemoselectivity of the photocatalytic reaction varying the color of incident light. This strategy may be implemented by using a sensitizer capable to activate a specific reaction pathway depending on the excitation light. Herein, we use potassium poly(heptazine imide) (K-PHI), a type of carbon nitride, to generate selectively three different products from S-arylthioacetates simply varying the excitation light and otherwise identical conditions. Namely, arylchlorides are produced under UV/purple, sulfonyl chlorides with blue/white, and diaryldisulfides at green to red light. A combination of the negatively charged polyanion, highly positive potential of the valence band, presence of intraband states, ability to sensitize singlet oxygen, and multi-electron transfer is shown to enable this chromoselective conversion of thioacetates.
- Antonietti, Markus,Guldi, Dirk M.,Markushyna, Yevheniia,Savateev, Aleksandr,Schü?lbauer, Christoph M.,Ullrich, Tobias
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supporting information
p. 20543 - 20550
(2021/08/12)
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- Controllable synthesis of ultrasmall Pd nanocatalysts templated by supramolecular coordination cages for highly efficient reductive dehalogenation
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Supported ultrasmall noble metal nanocatalysts (UNMNs) are one of the most important classes of solid materials for heterogeneous catalysis. Herein, a simple and efficient supramolecular coordination cage (SCC) template-strategy has been developed to synthesize UNMNs with controllable size and size distribution. A series of SCCs, including M2L4, M4L2, M6L4 and M12L24, with well-defined sizes and shapes as well as different numbers of Pd ions were designed and synthesized as templates. Subsequently, the corresponding Pd nanocatalysts M2&at;CMC, M4&at;CMC, M6&at;CMC and M12&at;CMC were prepared by an impregnation-reduction method on carboxymethylcellulose (CMC) hydrogel supports. It was found that the employment of SCCs as templates could not only significantly reduce the aggregation tendency of Pd nanoparticles but also play an important role in regulating their size and size distribution. For example, the analysis of the catalyst size distribution indicated that the greater the number of Pd ions the cage possesses, the bigger the size of the catalyst. Moreover, with the decrease of the concentration of the template, the size of the Pd nanocatalyst also decreased obviously. Particularly, the resultant catalyst with a nano-Pd loading as high as 12.63percent could still maintain a narrow size distribution. Furthermore, the as-prepared Pd nanocatalyst could serve as a highly efficient polychlorinated biphenyl (PCB) degrader both in a stirred vessel and a continuous flow reactor because of its excellent catalytic efficiency in the reductive dehalogenation reaction under mild conditions. In a word, the SCC template-strategy employed in this study provides new guidelines for the preparation of size-controllable UNMNs on a variety of supports, along with high noble metal loading and catalytic activity. This journal is
- Jiang, Wei-Ling,Peng, Zhiyong,Shen, Ji-Chuang,Shi, Xueliang,Wu, Gui-Yuan,Yang, Hai-Bo,Yin, Guang-Qiang
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supporting information
p. 12097 - 12105
(2020/07/09)
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- Silylation of Aryl Chlorides by Bimetallic Catalysis of Palladium and Gold on Alloy Nanoparticles
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Supported palladium-gold alloy-catalyzed cross-coupling of aryl chlorides and hydrosilanes enabled the selective formation of aryl-silicon bonds. Whereas a monometallic palladium catalyst predominantly promoted the hydrodechlorination of aryl chlorides and gold nanoparticles showed no catalytic activity, gold-rich palladium-gold alloy nanoparticles efficiently catalyzed the title reaction to give arylsilanes with high selectivity. A wide array of aryl chlorides and hydrosilanes participated in the heterogeneously-catalyzed reaction to furnish the corresponding arylsilanes in 34–80% yields. A detailed mechanistic investigation revealed that palladium and gold atoms on the surface of alloy nanoparticles independently functioned as active sites for the formation of aryl nucleophiles and silyl electrophiles, respectively, which indicates that palladium and gold atoms on alloy nanoparticles work together to enable the selective formation of aryl-silicon bonds. (Figure presented.).
- Miura, Hiroki,Masaki, Yosuke,Fukuta, Yohei,Shishido, Tetsuya
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supporting information
p. 2642 - 2650
(2020/04/22)
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- Tailorable carbazolyl cyanobenzene-based photocatalysts for visible light-induced reduction of aryl halides
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Herein, a series of carbazolyl cyanobenzene (CCB)-based organic photocatalysts with a broad range of photoredox capabilities were designed and synthesized, allowing precise control of the photocatalytic reactivity for the controllable reduction of aryl halides via a metal-free process. The screened-out CCB (5CzBN), a metal-free, low-cost, scalable and sustainable photocatalyst with both strong oxidative and reductive ability, exhibits superior performance for both dehalogenation and C[sbnd]C bond-forming arylation reactions.
- Ou, Wei,Zou, Ru,Han, Mengting,Yu, Lei,Su, Chenliang
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supporting information
p. 1899 - 1902
(2019/12/27)
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- Oxidative Photochlorination of Electron-Rich Arenes via in situ Bromination
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Electron-rich arenes are oxidatively photochlorinated in the presence of catalytic amounts of bromide ions, visible light, and 4CzIPN as organic photoredox catalyst. The substrates are brominated in situ in a first photoredox-catalyzed oxidation step, followed by a photocatalyzed ipso-chlorination, yielding the target compounds in high ortho/para regioselectivity. Dioxygen serves as a green and convenient terminal oxidant. The use of aqueous hydrochloric acid as the chloride source reduces the amount of saline by-products.
- Düsel, Simon Josef Siegfried,K?nig, Burkhard
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supporting information
p. 1491 - 1495
(2019/04/30)
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- Deep compositional understanding of TBA: AlCl3 ionic liquid for its applications
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Chloroaluminate ionic liquids (ILs) have been immensely used as homogeneous catalyst in Friedel-Crafts reaction. We have recently synthesized chloroaluminate ILs by reacting aluminium chloride with a hydrophobic neutral ligand i.e. tributylamine (TBA:AlCl3). The current study elaborates on the investigations of the composition of the ionic liquids at various stages of their formation. The ionic liquids were synthesized using various mole ratios of tributyl amine and aluminium chloride in range of 1:1 to 1:2.3, in presence of an aromatic solvent in a one pot reaction. Various characterization techniques like Mass spectrometry, 27Al Nuclear Magnetic Resonance, 31P Nuclear Magnetic Resonance and Fourier Transform Infrared spectroscopy were used to elucidate the formation of various moieties of the TBA:AlCl3 Ionic Liquid. This study also elaborates on the investigations of the cationic and anionic moieties and their structure-property relationship for various applications. Various Friedel-Crafts reaction of industrial importance were performed using the ionic liquid having (Al2Cl7)?moiety to assess its performance and compared with conventional processes. The synthesized products were characterised by sophisticated analytical techniques like 1H NMR, 13C NMR, FTIR, GC–MS, GC-FID, to name a few. This class of ionic liquids also have importance in various electrochemical applications like aluminium deposition and aluminium batteries.
- Bhakthavatsalam, Vishnupriya,Chandra, Sudeshna,Choudhury, Rudra Prosad,Lande, Sharad V.,Pradhan, Jeevan,Sakhalkar, Mangesh
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- The Electronic Properties of Ni(PNN) Pincer Complexes Modulate Activity in Catalytic Hydrodehalogenation Reactions
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Three chloronickel(II) complexes of PNN- pincer ligands with pyrazolyl and diphenylphosphino donors appended to different arms of diarylamido anchors were prepared and fully characterized. The three derivatives (1-OMe, 1-Me, 1-CF3) differ only by the identity of the para-aryl substituent on the pyrazolyl arm with 1-OMe being 310 mV easier to oxidize than 1-CF3. All three complexes are competent catalysts for hydrodehalogenation reactions of 1-bromooctane and a variety of aryl halides in dimethylacetamide using NaBH4 as both base and hydride source. Comparative studies using diverse substrates showed that catalytic activity correlates with electron donor properties; 1-OMe was superior to the other two. Deuterium labeling studies verified NaBD4 as the deuteride source and excluded solvent-assisted radical pathways.
- Wang, Denan,Gardinier, James R.
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p. 4425 - 4434
(2020/10/19)
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- Effects of Ligand Substitution on the Optical and Electrochemical Properties of (Pyridinedipyrrolide)zirconium Photosensitizers
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A series of seven bis(pyridinedipyrrolide)zirconium complexes, Zr(R1PDPR2)2, where [R1PDPR2]2- is the doubly deprotonated form of [2,6-bis(5-R1-3-R2-1H-pyrrol-2-yl)pyridine], were prepared and characterized in solution by NMR, UV/vis absorption, and emission spectroscopy and cyclic voltammetry. The molecular structures were determined by single-crystal X-ray crystallography. All complexes exhibit remarkably long emission lifetimes (τ = 190-576 μs) with high quantum efficiencies (φPL = 0.10-0.38) upon excitation with visible light in a benzene solution. The substituents on the pyrrolide rings were shown to have significant effects on the photoluminescence and electrochemical properties of these compounds. The R2 substituents (R2 = H, Me, Ph, or C6F5) show only limited effects on the absorption and emission profiles of the complexes but allow systematic tuning of the ground- and excited-state redox potentials over a range of almost 600 mV. The R1 substituents (R1 = H, Me, Ph, or 2,4,6-Me3Ph) influence both the optical and electrochemical properties through electronic effects. Additionally, the R1 substituents have profound consequences for the structural flexibility and overall stability of the compounds. Distortions of the Zr(PDP)2 core from idealized D2d symmetry in the solid state can be traced to the steric profiles of the R1 substituents and correlate with the observed Stokes shifts for each compound. The complex with the smallest ligand system, Zr(HPDPH)2, coordinates two additional solvent molecules in a tetrahydrofuran (THF) solution, which allowed the isolation of photoluminescent, eight-coordinate Zr(HPDPH)2(THF)2. The photoredox catalytic dehalogenation of aryl iodides and aryl chlorides using the most reducing derivative, Zr(MePDPMe)2, highlights the potential of Zr(PDP)2 photosensitizers to promote challenging reductive transformations under mild conditions upon excitation with green light.
- Belldina, Anne M.,Leary, Dylan C.,Milsmann, Carsten,Petersen, Jeffrey L.,Zhang, Yu
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supporting information
p. 14716 - 14730
(2020/11/02)
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- Microwave-Assisted Decarbonylation of Biomass-Derived Aldehydes using Pd-Doped Hydrotalcites
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Catalytic decarbonylation is an underexplored strategy for deoxygenation of biomass-derived aldehydes owing to a lack of low-cost and robust heterogeneous catalysts that can operate in benign solvents. A family of Pd-functionalized hydrotalcites (Pd-HTs) were synthesized, characterized, and applied to the decarbonylation of furfural, 5-hydroxymethylfurfural (HMF), and aromatic and aliphatic aldehydes under microwave conditions. This catalytic system delivered enhanced decarbonylation yields and turnover frequencies, even at a low Pd loading (0.5 mol %). Furfural decarbonylation was optimized in a benign solvent (ethanol) compatible with biomass processing; HMF selectively afforded an excellent yield (93 %) of furfuryl alcohol without humin formation; however, a longer reaction favored the formation of furan through tandem alcohol dehydrogenation and decarbonylation. Yields of the substituted benzaldehydes (37–99 %) were proportional to the calculated Mulliken charge of the carbonyl carbon. Activity and selectivity reflected loading-dependent Pd speciation. Continuous-flow testing of the best Pd-HT catalyst delivered good stability over 16 h on stream, with near-quantitative conversion of HMF.
- An, Nan,Ainembabazi, Diana,Reid, Christopher,Samudrala, Kavya,Wilson, Karen,Lee, Adam F.,Voutchkova-Kostal, Adelina
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p. 312 - 320
(2019/11/13)
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- Synthesis of thioethers, arenes and arylated benzoxazoles by transformation of the C(aryl)-C bond of aryl alcohols
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Transformation of aryl alcohols into high-value functionalized aromatic compounds by selective cleavage and functionalization of the C(aryl)-C(OH) bond is of crucial importance, but very challenging by far. Herein, for the first time, we report a novel and versatile strategy for activation and functionalization of C(aryl)-C(OH) bonds by the cooperation of oxygenation and decarboxylative functionalization. A diverse range of aryl alcohol substrates were employed as arylation reagents via the cleavage of C(aryl)-C(OH) bonds and effectively converted into corresponding thioether, arene, and arylated benzoxazole products in excellent yields, in a Cu based catalytic system using O2 as the oxidant. This study offers a new way for aryl alcohol conversion and potentially offers a new opportunity to produce high-value functionalized aromatics from renewable feedstocks such as lignin which features abundant C(aryl)-C(OH) bonds in its linkages.
- Chen, Bingfeng,Han, Buxing,Liu, Mingyang,Meng, Qinglei,Song, Jinliang,Zhang, Pei,Zhang, Zhanrong
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p. 7634 - 7640
(2020/08/14)
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- Visible-Light-Induced Ni-Catalyzed Radical Borylation of Chloroarenes
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A highly selective and general photoinduced C-Cl borylation protocol that employs [Ni(IMes)2] (IMes = 1,3-dimesitylimidazoline-2-ylidene) for the radical borylation of chloroarenes is reported. This photoinduced system operates with visible light (400 nm) and achieves borylation of a wide range of chloroarenes with B2pin2 at room temperature in excellent yields and with high selectivity, thereby demonstrating its broad utility and functional group tolerance. Mechanistic investigations suggest that the borylation reactions proceed via a radical process. EPR studies demonstrate that [Ni(IMes)2] undergoes very fast chlorine atom abstraction from aryl chlorides to give [NiI(IMes)2Cl] and aryl radicals. Control experiments indicate that light promotes the reaction of [NiI(IMes)2Cl] with aryl chlorides generating additional aryl radicals and [NiII(IMes)2Cl2]. The aryl radicals react with an anionic sp2-sp3 diborane [B2pin2(OMe)]- formed from B2pin2 and KOMe to yield the corresponding borylation product and the [Bpin(OMe)]?- radical anion, which reduces [NiII(IMes)2Cl2] under irradiation to regenerate [NiI(IMes)2Cl] and [Ni(IMes)2] for the next catalytic cycle.
- Tian, Ya-Ming,Guo, Xiao-Ning,Krummenacher, Ivo,Wu, Zhu,Nitsch, J?rn,Braunschweig, Holger,Radius, Udo,Marder, Todd B.
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supporting information
p. 18231 - 18242
(2020/11/02)
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- Practical Transition-Metal-Free Protodeboronation of Arylboronic Acids in Aqueous Sodium Hypochlorite
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A concise and practical method was developed for the protodeboronation of arylboronic acids under mild conditions in aqueous NaClO at 100 °C. The strategy is low-cost, transition-metal-free, and base-free.
- Li, Minxin,Tang, Yanling,Gao, Jinchun,Rao, Gaoxiong,Mao, Zewei
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p. 2039 - 2042
(2020/10/21)
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- Direct Stereoselective β-Arylation of Enol Ethers by a Decarboxylative Heck-Type Reaction
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Despite remarkable advances to promote regio- and stereoselective decarboxylative arylation of inactivated olefins with benzoic acid derivatives, methodologies involving hetero-substituted alkenes are still lacking. Herein, PdII-catalyzed decarboxylative Heck coupling of α-alkoxyacrylates with (hetero)aryl carboxylic acids for the stereocontrolled production of (Z)-β-heteroarylated vinyl ethers is reported. This methodology offers a rational and step-economical route to the synthesis of attractive β-arylated α-alkoxy α,β-unsaturated carboxylates family which emerged as a relevant class of building blocks with different applications. Mechanistically, whereas electron rich benzoic acids undergo a PdII-catalyzed decarboxylation, electron-deficient substrates proceed through silver(I)-mediated decarboxylation, explaining thus the formation of stereoisomers (E) and (Z) of β-arylated vinyl ethers in presence of these latter.
- Hachem, Mahmoud,Hoarau, Christophe,Schneider, Cédric
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- A Nickel-Doped Dehydrobenzoannulene-Based Two-Dimensional Covalent Organic Framework for the Reductive Cleavage of Inert Aryl C-S Bonds
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The development of metalated covalent organic frameworks (COFs) is useful for generating recyclable catalytic systems for practical applications. Herein, we report the synthesis, characterization, and catalytic properties of an azine-linked two-dimensional (2D) COF containing nickel-doped dehydrobenzoannulene (DBA) units. We demonstrate that Ni-DBA-2D-COF can be used to reductively cleave the aryl C-S bonds of several organosulfur compounds utilizing dimethylethylsilane as the reducing agent. The Ni-DBA-2D-COF catalytic system displays excellent recyclability and good yields. This work highlights a rare example of utilizing metalated DBA complexes to perform catalytic transformations.
- Haug, W. Karl,McGrier, Psaras L.,Morman, Blake T.,Thomas, Christine M.,Wolfson, Eric R.
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supporting information
p. 5521 - 5525
(2020/04/09)
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- Continuous flow synthesis of aryl aldehydes by Pd-catalyzed formylation of phenol-derived aryl fluorosulfonates using syngas
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This communication describes the palladium-catalyzed reductive carbonylation of aryl fluorosulfonates (ArOSO2F) using syngas as an inexpensive and sustainable source of carbon monoxide and hydrogen. The conversion of phenols to aryl fluorosulfonates can be conveniently achieved by employing the inexpensive commodity chemical sulfuryl fluoride (SO2F2) and base. The developed continuous flow formylation protocol requires relatively low loadings for palladium acetate (1.25 mol%) and ligand (2.5 mol%). Good to excellent yields of aryl aldehydes were obtained within 45 min for substrates containing electron withdrawing substituents, and 2 h for substrates containing electron donating substituents. The optimal reaction conditions were identified as 120 °C temperature and 20 bar pressure in dimethyl sulfoxide (DMSO) as solvent. DMSO was crucial in suppressing Pd black formation and enhancing reaction rate and selectivity. This journal is
- Hanselmann, Paul,Hone, Christopher A.,Hu, Guixian,K?ckinger, Manuel,Kappe, C. Oliver
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p. 22449 - 22453
(2020/07/03)
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- Visible Light-Induced α-C(sp3)-H Acetalization of Saturated Heterocycles Catalyzed by a Dimeric Gold Complex
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Saturated heterocyclic acetals are useful fragments in organic synthesis and other fields. Herein, C(sp3)-H dehydrogenative cross-couplings of ethers, tetrahydrothiophenes, and pyrrolidines were achieved under visible light irradiation by using iodobenzene and an in situ-formed gold complex. The broad functional group compatibility and substrate scope indicate that our strategy is a promising way to synthesize acetal analogues. The method was successfully applied in late-stage modifications of bioactive molecules. Gram scale syntheses and mechanistic studies are also presented.
- Si, Xiaojia,Zhang, Lumin,Wu, Zuozuo,Rudolph, Matthias,Asiri, Abdullah M.,Hashmi, A. Stephen K.
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supporting information
p. 5844 - 5849
(2020/08/12)
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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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- Multiphase Hydrodechlorination of 1,3,5-Trichlorobenzene on Palladium Catalysts Supported on Alumina: Effect of the Support Properties and Modification by Heteropoly Acid Based on Silicon and Tungsten
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Abstract: Catalytic systems 2 wt % Pd/Al2O3 were prepared using noncalcined boehmite (NC) and two types of alumina support: one was prepared by the calcination of boehmite at 600°C (C) and the other produced by Engelhard (E). To prepare 2 wt % Pd/HPC–Al2O3 samples, these supports were modified by impregnation by a heteropoly compound (HPC) (20 wt % Н8[Si(W2O7)6] ? 6Н2О). The effect of the Al2O3 structure and its modification by the heteropoly compound on the physicochemical properties, activity, selectivity and stability of catalysts in the reaction of multiphase hydrodechlorination of 1,3,5-trichlorobenzene (TCB) was studied. All catalysts showed activity in the considered reaction with the predominant formation of benzene but were deactivated in the reaction medium. Modification by the heteropoly compound resulted in increased stability and was especially effective for catalyst supported on Al2O3(E). The method of scanning electron microscopy (SEM) was used to determine the morphological differences of supports. According to the data of transmission electron microscopy, all catalysts contained palladium in the form of particles less than 20 nm in size. The particle size and width of the size distribution increases in the series Pd/Al2O3(NC) 2O3(C) 2O3(E). Modification by the heteropoly compound was favorable for the decrease in the size of palladium particles. The method of temperature-programmed reduction with hydrogen (TPR-H2) showed that all catalysts included in their composition palladium hydride along with more strongly surface-bound metal forms that are reduced at elevated temperatures, and their content decreases after modification by the heteropoly compound and increases after catalytic tests. According to diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the deposition of a heteropoly compound leads to a change in the type of Lewis acid sites on the alumina surface and in the electronic state of palladium. According to the results of infrared spectroscopic studies of adsorbed CO, the relatively large particles of Pd0 are the main form on the surface of nonmodified catalysts. The catalysts modified by the heteropoly compound contain single Pd+ and Pd2+ cations, and the fraction of Pd0 is substantially smaller. The specific features of the Lewis acidity of the catalyst surface determine the possibility of 1,3,5-trichlorobenzene adsorption and activation on the support and the spillover of hydrogen from Pd0. An increase in the catalyst stability as a result of support modification by the heteropoly compound can be explained by the appearance of new active sites in the interaction of palladium with the heteropoly compound or its thermal decomposition products.
- Golubina,Lokteva,Gurbanova,Kharlanov,Egorova,Lipatova,Vlaskin,Shkol’nikov
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p. 297 - 314
(2019/06/24)
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- Catalytic hydrodebromination of aryl bromides by cobalt tetra-butyl porphyrin complexes with EtOH
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Hydrodebromination of aryl bromides catalyzed by electron rich and sterically unhindered cobalt 5,10,15,20-tetrabutylporphyrin was achieved at mild conditions in good yields employing EtOH as the hydrogen source. The catalytic efficiency was enhanced compared with previously reported by cobalt tetra-aryl porphyrin catalysts. A revised mechanism of single electron transfer was proposed.
- Chen, Chen,Zuo, Huiping,Chan, Kin Shing
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p. 510 - 517
(2019/01/04)
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- Hydrogen bonding promoted simple and clean photo-induced reduction of C-X bond with isopropanol
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We herein report a simple and clean photo-induced metal-free reduction of C-X bond under an atmosphere of air at room temperature. Isopropanol is used as both the reducing reagent and solvent. Various functional groups (acids, esters, alcohols, anilines, phenols, indoles, pyridines, cyano and trifluoromethyl groups) and other heterocyclic compounds are tolerated. Different organic halides (including C-I, C-Br and C-Cl bonds) can be dehalogenated with moderate to excellent yields. Polyhalides are also reduced chemoselectively and efficiently. DFT calculation suggests a six-membered ring transition state via C-X H-O hydrogen bonding to decrease the activation energy.
- Cao, Dawei,Yan, Chaoxian,Zhou, Panpan,Zeng, Huiying,Li, Chao-Jun
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supporting information
p. 767 - 770
(2019/01/21)
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- Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation
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The dehalogenation-arylation and the hydrodehalogenation of various types of organic halides are selectively realized using AgF and visible light without any organic additives under mild conditions. Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h-1. This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.
- Wu, Wenli,Cui, Enxin,Zhang, Yun,Zhang, Chen,Zhu, Feng,Tung, Chen-Ho,Wang, Yifeng
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p. 6335 - 6341
(2019/07/04)
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- Competing dehalogenation versus borylation of aryl iodides and bromides under transition-metal-free basic conditions
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In this work, selectivity-controllable base-promoted transition-metal-free borylation and dehalogenation of aryl halides are described. Under the conditions of borylation, the dehalogenation which emerges as a competitive side reaction has been well-controlled by carefully controlling the borylation conditions. On the other hand, the dehalogenation using benzaldehyde as a hydrogen source has also been accomplished. The applications of direct radical borylation and dehalogenation of aryl halides demonstrate their synthetic practicability in pharmaceutical-oriented organic synthesis. Based on the experimental evidences, the tBuOK/1,10-Phen-triggered radical nature of both competitive reactions has been revealed.
- Niu, Yi-Jie,Sui, Guo-Hui,Zheng, Hong-Xing,Shan, Xiang-Huan,Tie, Lin,Fu, Jia-Le,Qu, Jian-Ping,Kang, Yan-Biao
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p. 10805 - 10813
(2019/09/30)
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- Transition-State Interactions in a Promiscuous Enzyme: Sulfate and Phosphate Monoester Hydrolysis by Pseudomonas aeruginosa Arylsulfatase
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Pseudomonas aeruginosa arylsulfatase (PAS) hydrolyzes sulfate and, promiscuously, phosphate monoesters. Enzyme-catalyzed sulfate transfer is crucial to a wide variety of biological processes, but detailed studies of the mechanistic contributions to its catalysis are lacking. We present linear free energy relationships (LFERs) and kinetic isotope effects (KIEs) of PAS and analyses of active site mutants that suggest a key role for leaving group (LG) stabilization. In LFERs PASWT has a much less negative Br?nsted coefficient (βleaving groupobs-Enz = 0.33) than the uncatalyzed reaction (βleaving groupobs = 1.81). This situation is diminished when cationic active site groups are exchanged for alanine. The considerable degree of bond breaking during the transition state (TS) is evidenced by an 18Obridge KIE of 1.0088. LFER and KIE data for several active site mutants point to leaving group stabilization by active site K375, in cooperation with H211. 15N KIEs and the increased sensitivity to leaving group ability of the sulfatase activity in neat D2O (βleaving groupH-D = +0.06) suggest that the mechanism for S-Obridge bond fission shifts, with decreasing leaving group ability, from charge compensation via Lewis acid interactions toward direct proton donation. 18Ononbridge KIEs indicate that the TS for PAS-catalyzed sulfate monoester hydrolysis has a significantly more associative character compared to the uncatalyzed reaction, while PAS-catalyzed phosphate monoester hydrolysis does not show this shift. This difference in enzyme-catalyzed TSs appears to be the major factor favoring specificity toward sulfate over phosphate esters by this promiscuous hydrolase, since other features are either too similar (uncatalyzed TS) or inherently favor phosphate (charge).
- Van Loo, Bert,Berry, Ryan,Boonyuen, Usa,Mohamed, Mark F.,Golicnik, Marko,Hengge, AlVan C.,Hollfelder, Florian
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p. 1363 - 1378
(2019/03/11)
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- Chiral fluorescent compound based on cyclophane alkane framework and preparation method and application of compound
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The invention relates to a chiral fluorescent compound based on a cyclophane alkane framework and a preparation method and application of the compound. By using the rigid framework structure of cyclophane alkane, the chirality of the cyclophane alkane can be well kept under the excitation state, and accordingly high asymmetry factors are obtained. By changing R2 and R3 substituent groups, the luminescence section, CPL intensity and luminescence intensity can be regulated and controlled. By changing R1 substituent groups, a thermal-activation delayed fluorescence material is obtained. Phenazinemolecules based on the cyclophane alkane have a good circularly polarized luminescence characteristic and have potential application in the aspects of 3D optical display, information storage and transmission, confidential information recording, optoelectronic devices and even asymmetry photochemical synthesis.
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Paragraph 0061-0080
(2019/11/14)
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- Method for synthesizing dichlorobenzene
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The invention provides a method for synthesizing dichlorobenzene, and the method comprises the following steps: taking trichlorobenzene as a substrate, adding dimethyl sulfoxide (DMSO), an aqueous solution of M(OH)n and a catalyst to form a mixture; stirring and heating the mixture; and contacting hydrogen with the mixture and heating for reaction to obtain the dichlorobenzene; the pH value of theaqueous solution of M(OH)n is great than 7, M is an alkali metal or alkaline earth metal, and n is a positive integer; and the catalyst is a metal catalyst or a metal supported catalyst.
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Paragraph 0061-0080
(2019/11/14)
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- Nickel-catalysed C–O bond reduction of 2,4,6-triaryloxy-1,3,5-triazines in 2-methyltetrahydrofuran
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A nickel-catalysed reduction of phenol derivatives activated by 2,4,6-trichloro-1,3,5-triazine (TCT) in ecofriendly 2-methyltetrahydrofuran (2-MeTHF) is described. The phenol-TCT derivatives were readily prepared using grinding method in short time without further purification. This catalytic system allowed the facile C–O cleavage of phenol-TCT derivatives under mild reaction conditions with high efficiency and good functional group tolerance. Gram-scale reaction was also achieved. Particularly, sequential functionalization of phenol-TCT derivatives followed by C–O bond reduction could also be realized, affording the high value-added products in moderate to good yields.
- Wang, Yaoyao,Shen, Jun,Chen, Qun,Wang, Liang,He, Mingyang
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p. 409 - 412
(2018/10/02)
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- Hydro/deutero deamination of arylazo sulfones under metal and (photo)catalyst-free conditions
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Hydrodeaminated and monodeuterated aromatics were obtained via a visible-light driven reaction of arylazo sulfones. Deuteration occurs efficiently in deuterated media such as isopropanol-d8 or in THF-d8/water mixtures and exhibits a high tolerance to the nature and the position of the aromatic substituents.
- Amin, Hawraz I.M.,Raviola, Carlotta,Amin, Ahmed A.,Mannucci, Barbara,Protti, Stefano,Fagnoni, Maurizio
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- On/Off O2 Switchable Photocatalytic Oxidative and Protodecarboxylation of Carboxylic Acids
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Photoredox catalysis in recent years has manifested a powerful branch of science in organic synthesis. Although merging photoredox and metal catalysts has been a widely used method, switchable heterogeneous photoredox catalysis has rarely been considered. Herein, we open a new window to use a switchable heterogeneous photoredox catalyst which could be turned on/off by changing a simple stimulus (O2) for two opponent reactions, namely, oxidative and protodecarboxylation. Using this strategy, we demonstrate that Au@ZnO core-shell nanoparticles could be used as a switchable photocatalyst which has good catalytic activity to absorb visible light due to the localized surface plasmon resonance effect of gold, can decarboxylate a wide range of aromatic and aliphatic carboxylic acids, have multiple reusability, and are a reasonable candidate for synthesizing both aldehydes/ketones and alkane/arenes in a large-scale set up. Some biologically active molecules are also shown via examples of the direct oxidative and protodecarboxylation which widely provided pharmaceutical agents.
- Bazyar, Zahra,Hosseini-Sarvari, Mona
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p. 13503 - 13515
(2019/10/11)
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- Decarbonylation of Aromatic Aldehydes and Dehalogenation of Aryl Halides Using Maghemite-Supported Palladium Catalyst
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A facile decarbonylation reaction of a variety of aromatic and heteroaromatic aldehydes using maghemite-supported palladium catalyst has been developed. The magnetic properties of catalyst facilitated an easy and efficient recovery of the catalyst from the reaction mixture using an external magnet. It was found that the catalyst could be reused up to four consecutive catalytic runs without a significant change in activity. In addition, the catalyst was also very effective in the dehalogenation of aryl halides. This is the first report on efficient utilization of directly immobilized Pd on maghemite in decarbonylation and dehalogenation reactions.
- Ajda?i?, Vladimir,Nikoli?, Andrea,Simi?, Stefan,Manojlovi?, Dragan,Stojanovi?, Zoran,Nikodinovic-Runic, Jasmina,Opsenica, Igor M.
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p. 119 - 126
(2017/12/27)
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- Mechanochemical Activation of Zinc and Application to Negishi Cross-Coupling
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A form independent activation of zinc, concomitant generation of organozinc species and engagement in a Negishi cross-coupling reaction via mechanochemical methods is reported. The reported method exhibits a broad substrate scope for both C(sp3)–C(sp2) and C(sp2)–C(sp2) couplings and is tolerant to many important functional groups. The method may offer broad reaching opportunities for the in situ generation organometallic compounds from base metals and their concomitant engagement in synthetic reactions via mechanochemical methods.
- Cao, Qun,Howard, Joseph L.,Wheatley, Emilie,Browne, Duncan L.
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p. 11339 - 11343
(2018/08/28)
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- An Additive-Free, Base-Catalyzed Protodesilylation of Organosilanes
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We report an additive-free, base-catalyzed C-, N-, O-, and S-Si bond cleavage of various organosilanes in mild conditions. The novel catalyst system exhibits high efficiency and good functional group compatibility, providing the corresponding products in good to excellent yields with low catalyst loadings. Overall, this transition-metal-free process may offer a convenient and general alternative to current employing excess bases, strong acids, or metal-catalyzed systems for the protodesilylation of organosilanes.
- Yao, Wubing,Li, Rongrong,Jiang, Huajiang,Han, Deman
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p. 2250 - 2255
(2018/02/23)
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- Selective Hydrogenations and Dechlorinations in Water Mediated by Anionic Surfactant-Stabilized Pd Nanoparticles
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We report a facile, inexpensive, and green method for the preparation of Pd nanoparticles in aqueous medium stabilized by anionic sulfonated surfactants sodium 1-dodecanesulfonate 1a, sodium dodecylbenzenesulfonate 1b, dioctyl sulfosuccinate sodium salt 1c, and poly(ethylene glycol) 4-nonylphenyl-3-sulfopropyl ether potassium salt 1d simply obtained by stirring aqueous solutions of Pd(OAc)2 with the commercial anionic surfactants further treated under hydrogen atmosphere for variable amounts of time. The aqueous Pd nanoparticle solutions were tested in the selective hydrogenation reactions of aryl-alcohols, -aldehydes, and -ketones, leading to complete conversion to the deoxygenated products even in the absence of strong Br?nsted acids in the reduction of aromatic aldehydes and ketones, in the controlled semihydrogenation of alkynes leading to alkenes, and in the efficient hydrodechlorination of aromatic substrates. In all cases, the micellar media were crucial for stabilizing the metal nanoparticles, dissolving substrates, steering product selectivity, and enabling recycling. What is interesting is also that a benchmark catalyst like Pd/C can often be surpassed in activity and/or selectivity in the reactions tested by simply switching to the appropriate commercially available surfactant, thereby providing an easy to use, flexible, and practical catalytic system capable of efficiently addressing a variety of synthetically significant hydrogenation reactions.
- La Sorella, Giorgio,Sperni, Laura,Canton, Patrizia,Coletti, Lisa,Fabris, Fabrizio,Strukul, Giorgio,Scarso, Alessandro
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supporting information
p. 7438 - 7446
(2018/05/29)
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- A Predictive Model for the Decarboxylation of Silver Benzoate Complexes Relevant to Decarboxylative Coupling Reactions
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Decarboxylative coupling reactions offer an attractive route to generate functionalized arenes from simple and readily available carboxylic acid coupling partners, yet they are underutilized due to limitations in the scope of carboxylic acid coupling partner. Here we report that the field effect parameter (F) has a substantial influence on the rate of decarboxylation of well-defined silver benzoate complexes. This finding provides the opportunity to surpass current substrate limitations associated with decarboxylation and to enable widespread utilization of decarboxylative coupling reactions.
- Crovak, Robert A.,Hoover, Jessica M.
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p. 2434 - 2437
(2018/02/28)
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- Mechanistic Study on Aryl-Exchange Reaction of Diaryl-λ3-iodane with Aryl Iodide
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Because of its hyper-leaving ability, as well as its strong oxidizing ability, diaryl(triflato)-λ3-iodane transfers one of the aryl groups to iodoarenes simply upon gentle heating (>85 °C) in nonpolar solvents. We have performed an in-depth mechanistic study of this unusual aryl transfer reaction. A combination of experimental (product analysis, kinetic study, and substituent effects) and density functional theoretical approaches revealed that the reaction proceeds through a concerted bimolecular transition state, in which ipso-carbon binds loosely to both iodine centers. We also evaluated electronic effects on the thermodynamic stability of diaryl-λ3-iodanes.
- Masumoto, Yui,Miyamoto, Kazunori,Iuchi, Takuto,Ochiai, Masahito,Hirano, Keiichi,Saito, Tatsuo,Wang, Chao,Uchiyama, Masanobu
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p. 289 - 295
(2018/02/19)
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