- Structure and Unprecedented Reactivity of a Mononuclear Nonheme Cobalt(III) Iodosylbenzene Complex
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A mononuclear nonheme cobalt(III) iodosylbenzene complex, [CoIII(TQA)(OIPh)(OH)]2+ (1), is synthesized and characterized structurally and spectroscopically. While 1 is a sluggish oxidant in oxidation reactions, it becomes a competent oxidant in oxygen atom transfer reactions, such as olefin epoxidation, in the presence of a small amount of proton. More interestingly, 1 shows a nucleophilic reactivity in aldehyde deformylation reaction, demonstrating that 1 has an amphoteric reactivity. Another interesting observation is that 1 can be used as an oxygen atom donor in the generation of high-valent metal-oxo complexes. To our knowledge, we present the first crystal structure of a CoIII iodosylbenzene complex and the unprecedented reactivity of metal-iodosylarene adduct.
- Fukuzumi, Shunichi,Kim, Kyung Ha,Lee, Yong-Min,Nam, Wonwoo,Seo, Mi Sook,Shearer, Jason,Yang, Jindou
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- Selective isomerization of aryl substituted epoxides to aldehydes via iron Lewis acid catalysis
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The iron Lewis acid [(η5-C5H5)Fe(CO)2(THF)]+BF4- (2) catalyzes the ring opening isomerization of aryl substituted epoxides (1) to aldehydes (3) in excellent yield.
- Picione, John,Mahmood, Syed J.,Gill, Andy,Hilliard, Marion,Hossain, M. Mahmun
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- Mechanism of Alkene Epoxidation by a Cytochrome P-450 Model. Effect of Additives
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Alcohols and styrene change the kinetics and the mechanism of alkene epoxidation by the mono-oxygenase model (tetra-p-tolylporphinato)manganese(III) acetate-sodium hypochlorite.
- Razenberg, Johannes A. S. J.,Nolte, Roeland J. M.,Drenth, Wiendelt
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- REGIOSELECTIVITY OF OLEFIN OXIDATION BY IODOSOBENZENE CATALYZED BY METALLOPORPHYRINS: CONTROL BY THE CATALYST
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The regioselectivity of the oxidation of three monosubstituted olefins, 6-phenoxyhex-1-ene, hex-1-ene and styrene, by iodosobenzene in the presence of various Fe-, Mn- or Cr-tetraaryl-porphyrins, was studied.It was found that, besides epoxides, known products from such systems, allylic alcohols and aldehydes were formed, the latter not being derived from the corresponding epoxides.The relative importance of these reactions greatly depends upon both the metal and porphyrin constituents of the catalyst.More particularly, the competition between epoxidation and allylic hydroxylation can be efficiently controlled by non bonded interactions between the olefin and porphyrin substituents.No hydroxylation of the aromatic rings and no oxidative dealkylation of the ether function was detected.
- Mansuy, Daniel,Leclaire, Jacques,Fontecave, Marc,Dansette, Patrick
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- Catalytic Hydrogenation of Styrene Oxide with Cationic Rhodium Complexes
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Catalytic hydrogenation of styrene oxide with cationic rhodium complexes was investigated to develop its selective conversion into the specific alcohol. β-Phenylethyl alcohol and phenylacetaldehyde were rather selectively produced without either α-phenylethyl alcohol or acetophenone through a selective antinormal fission of the epoxide ring.The catalytic activity and selectivity were found to depend strongly on the ligand, the activity for the formation of alcohol decreasing in the order, PEt3 > PMe3 PPh3 >> diphos.The highest yield, achieved by the PEt3 complex, reached as high as 82percent after 8 h of reaction.A possible mechanism was proposed to explain the selective formation of β-phenylethyl alcohol and the role of water as a cocatalyst in the catalytic hydrogenation.
- Fujitsu, Hiroshi,Shirahama, Shinichi,Matsumura, Eiichi,Takeshita, Kenjiro,Mochida, Isao
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- New pathway for heterogenization of molecular catalysts by non-covalent interactions with carbon nanoreactors
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A novel approach to heterogenization of catalytic molecules is demonstrated using the nanoscale graphitic step edges inside hollow graphitized carbon nanofibers (GNFs). The presence of the fullerene C60 moiety within a fullerene-salen CuII complex is essential for anchoring the catalyst within the GNF nanoreactor as demonstrated by comparison to the analogous catalyst complex without the fullerene group. The presence of the catalyst at the step edges of the GNFs is confirmed by high-resolution transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) with ultraviolet/visible (UV/vis) spectroscopy, demonstrating only negligible (ca. 3%) desorption of the fullerene-salen CuII complex from the GNFs into solution under typical reaction conditions. The catalyst immobilized in GNFs shows good catalytic activity and selectivity toward styrene epoxidation, comparable to the analogous catalyst in solution. Moreover, the fullerene-salen CuII complex in GNFs demonstrates excellent stability and recyclability because it can be readily separated from the reaction mixture and employed in multiple reaction cycles with minimal loss of activity, which is highly advantageous compared to catalysts not stabilized by the graphitic step edges that desorb rapidly from GNFs.
- Lebedeva, Maria A.,Chamberlain, Thomas W.,Schr?der, Martin,Khlobystov, Andrei N.
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- Controlled release of encapsulated bioactive volatiles by rupture of the capsule wall through the light-induced generation of a gas
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The encapsulation of photolabile 2-oxoacetates in core-shell microcapsules allows the light-induced, controlled release of bioactive compounds. On irradiation with UVA light these compounds degrade to generate an overpressure of gas inside the capsules, which expands or breaks the capsule wall. Headspace measurements confirmed the light-induced formation of CO and CO2 and the successful release of the bioactive compound, while optical microscopy demonstrated the formation of gas bubbles, the cleavage of the capsule wall, and the leakage of the oil phase out of the capsule. The efficiency of the delivery system depends on the structure of the 2-oxoacetate, the quantity used with respect to the thickness of the capsule wall, and the intensity of the irradiating UVA light.
- Paret, Nicolas,Trachsel, Alain,Berthier, Damien L.,Herrmann, Andreas
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- Convenient method for the transformation of epoxide to aldehyde and acetonide mediated by Cr-PLM
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Chromium-pillared montmorillonite (Cr-PLM) could be synthesized and efficiently utilized for styrene oxide transformations. The target aldehyde product could be quantitatively achieved from the isomerization of styrene oxide by using 10 wt% of Cr-PLM under reflux temperature for 15 min. The acetonide product could be achieved in excellent yield from the reaction of styrene oxide and acetone by using 10 wt% of Cr-PLM under room temperature for 20 min. The catalyst could be recovered and reused at least five times without loss of activity.
- Chareonsiriwat, Laddawan,Chavasiri, Warinthorn
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- Enhanced iron(III) corrole-catalyzed oxidations with iodobenzene diacetate: Synthetic and mechanistic investigations
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The electron-deficient iron(III) corrole complex catalyzes the efficient oxidation of hydrocarbons using PhI(OAc)2 as an mild oxygen source. The catalyst stability against degradation was much enhanced owing to the mild oxidizing ability of PhI(OAc)2. Excellent selectivity and high catalytic efficiency (with up to 1400 TON) have been achieved in alkene epoxidations. This promising oxygen transfer process is mechanistically rationalized in terms of a putative high-valent iron(V)-oxo species as the active oxidant.
- Chen, Tse-Hong,Kwong, Ka Wai,Carver, Aaron,Luo, Weilong,Zhang, Rui
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- Synthesis, structural studies and catalytic activity of a series of dioxidomolybdenum(VI)-thiosemicarbazone complexes
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Reaction of the thiosemicarbazone ligands, [4-(p-bromophenyl)thiosemicarbazone of salicylaldehyde (H2L1), 4-(p-X-phenyl)thiosemicarbazone of o-vanillin {X = F (H2L2), X = Cl (H2L3) and X = OMe (H2L4)}, 4-(p-bromophenyl)thiosemicarbazone of 5-bromosalicylaldehyde (H2L5), and 4-(p-chlorophenyl)thiosemicarbazone of o-hydroxynaphthaldehyde (H2L6)] with [MoO2(acac)2] afforded a series of new oxidomolybdenum(VI) complexes [Mo(VI)O2L1–6(solv)] (1–6) {where solv (solvent) = DMSO (1, 3, 5 & 6) and H2O (2 & 4)}. The molecular structures of 2 and 3 were determined by X-ray crystallography, demonstrating the dibasic tridentate behavior of ligands. The cyclic voltammogram pattern is similar for 1–6, which includes two irreversible reduction processes within the potential window ?0.71 to ?0.66 V and ?0.92 to ?0.85 V corresponding to the metal centered reduction from Mo(VI)/Mo(V) and Mo(V)/Mo(IV) respectively. Catalytic potential of 1–6 was tested for the oxidation of styrene and cyclohexene. The effect of various parameters such as the amount of catalyst, oxidant, NaHCO3, and solvent was checked to optimize the conditions for the best performance of the catalyst. 100% product selectivity for the formation of cyclohexene oxide from cyclohexene and ～98–99% product selectivity for the oxidation of styrene to styrene oxide was observed.
- Roy, Satabdi,Saswati,Lima, Sudhir,Dhaka, Sarita,Maurya, Mannar R.,Acharyya, Rama,Eagle, Cassandra,Dinda, Rupam
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- On the Mechanism of the Ruthenium-catalyzed β-methylation of Alcohols with Methanol
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Selective β-methylation of alcohols with methanol has been recently described using a catalytic system comprising the ruthenium pincer complex [RuH(CO)(BH4)(HN(C2H4PPh2)2)]-(Ru-MACHO-BH) 1 and alcoholate bases as co-catalysts. Here we present a detailed mechanistic analysis for the mono-methylation of 1-phenyl-propane-1-ol 2 a as prototypical example. Several experimentally observed intermediates were localized as stable minima on the DFT-derived energy surface of the entire reaction network. The ruthenium complex [Ru(H)2(CO)(HN(C2H4PPh2)2)] I was inferred as the active species catalyzing the de-hydrogenation/re-hydrogenation of substrates and intermediates (“hydrogen borrowing”). The hydrogen-bonded alcohol adduct of this complex was identified as the lowest lying intermediate (TDI). The C?C bond formation results from a base-catalyzed aldol reaction comprising the transition state with the highest energy (TDTS). Experimentally determined Gibbs free activation barriers of 26.1 kcal/mol and 26.0 kcal/mol in methanol and toluene as solvents, respectively, are reflected well by the computed energy span of the complex reaction network (29.2 kcal/mol).
- Kaithal, Akash,Schmitz, Marc,H?lscher, Markus,Leitner, Walter
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- Natural Abundance 2H Nuclear Magnetic Resonance Study of the Origin of 2-Phenylethanol and 2-Phenylethyl Acetate
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The site-specific natural abundance deuterium distribution of 2-phenylethanol (1) and 2-phenylethyl acetate (2) obtained through a variety of methods has been determined by 2H NMR spectroscopy.This technique provided a means of distinguishing between "natural" materials isolated from natural sources or obtained by biodegradation of L-phenylalanine and other products of petrochemical origin or obtained from natural L-phenylalanine through nonenzymic controlled chemical processes.Keywords: SNIF-NMR; aromas; 2-phenylethanol; 2-phenylethyl acetate; authentication
- Fronza, Giovanni,Fuganti, Claudio,Grasselli, Piero,Servi, Stefano,Zucchi, Gioia,et al.
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- Synthesis of aldehydes from oxiranes using silica gel as reagent
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The rearrangement of some 2-aryl monosubstituted and 2-aryl, 2-methyl disubstituted oxiranes to aldehydes using silica gel in very mild conditions is reported.
- Lemini,Ordonez,Perez-Flores,Cruz-Almanza
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- Nanoporous alumino- and borosilicate-mediated Meinwald rearrangement of epoxides
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Nanoporous alumino- and borosilicate materials, produced using an evaporation-induced self-assembly approach (EISA), efficiently catalyse the Meinwald rearrangement of epoxides in dimethyl carbonate (DMC) to produce the corresponding carbonyl compounds in high yield and excellent selectivity.
- Davies, Thomas E.,Kondrat, Simon A.,Nowicka, Ewa,Kean, Joseline L.,Harris, Christopher M.,Socci, Joseph M.,Apperley, David C.,Taylor, Stuart H.,Graham, Andrew E.
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- Co2+-exchanged MOR and 5A zeolites as efficient solid catalysts for the epoxidation of styrene with air
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Selective oxidation of alkenes with air to corresponding epoxides was performed over simple ion-exchanged Co-MOR and Co-5A. Among all transition metal ions-exchanged M-zeolites, both Co-MOR and Co-5A exhibited the highest activity at 363 K. Notably, for the epoxidation of styrene, α-pinene, α-methyl styrene and cyclooctene, Co-MOR obtained higher conversions than Co-5A, in agreement with the difference of pore sizes of both zeolitic materials. Recycling and control tests showed high durability of Co-MOR as a heterogeneous catalyst in our catalytic system.
- Zhou,Tang,Lu,Wei,Li,Xia
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- Three New Polyoxoniobates Functioning as Different Oxidation Catalysts
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Three new multifunctional isopolyniobates based on {Nb24O72}, namely, [Cu(en)2]9.75[Cu(en)2(H2O)]4[KNb24O72H9.25]2·36.5H2O (1), [Cu(en)2][Cu(en)2(H2O)]12[Cu(en)2(H2O)2]3[KNb24O72H7(H2O)2]2·99H2O (2), and [K(H2O)4][Cu(en)2(H2O)2]5[Cu(en)2(H2O)]8.25[Cu(en)2]2[K0.5Nb24O72H7.75]2·115.31H2O (3) (en = ethylenediamine), were obtained and characterized by IR, powder X-ray diffraction, single-crystal diffraction analysis, etc. Single-crystal analyses of the three compounds shows that all their clusters exhibit the same bowl-shaped structure, while the different transition metal complexes (TMCs) make compounds 1-3 show three entirely different packing structures. The catalytic properties of the three compounds as catalysts for Rhodamine B (RhB) photocatalytic degradation, styrene oxidation, and oxygen evolution reaction (OER) have been assessed, and all the compounds have good catalytic effects on the three different catalytic processes.
- Cui, Xiao-Bing,Li, Guanghua,Zhang, Ting-Ting
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- A Methylidene Group in the Phosphonic Acid Analogue of Phenylalanine Reverses the Enantiopreference of Binding to Phenylalanine Ammonia-Lyases
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Aromatic amino acid ammonia-lyases and aromatic amino acid 2,3-aminomutases contain the post-translationally formed prosthetic 3,5-dihydro-4-methylidene-5H-imidazol-5-one (MIO) group. MIO enzymes catalyze the stereoselective synthesis of α- or β-amino acid enantiomers, making these chemical processes environmentally friendly and affordable. Characterization of novel inhibitors enables structural understanding of enzyme mechanism and recognizes promising herbicide candidates as well. The present study found that both enantiomers of the aminophosphonic acid analogue of the natural substrate phenylalanine and a novel derivative bearing a methylidene at the β-position inhibited phenylalanine ammonia-lyases (PAL), representing MIO enzymes. X-ray methods unambiguously determined the absolute configuration of all tested enantiomers during their synthesis. Enzyme kinetic measurements revealed the enantiomer of the methylidene-substituted substrate analogue as being a mirror image relation to the natural l-phenylalanine as the strongest inhibitor. Isothermal titration calorimetry (ITC) confirmed the binding constants and provided a detailed analysis of the thermodynamic driving forces of ligand binding. Molecular docking suggested that binding of the (R)- and (S)-enantiomers is possible by a mirror image packing. (Figure presented.).
- Bata, Zsófia,Qian, Renzhe,Roller, Alexander,Horak, Jeannie,Bencze, László Csaba,Paizs, Csaba,Hammerschmidt, Friedrich,Vértessy, Beáta G.,Poppe, László
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- Different morphologies of silver nanoparticles as catalysts for the selective oxidation of styrene in the gas phase
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Silver nanoparticles of different morphologies were prepared using the polyol process and then dispersed on α-alumina. Catalysts were tested for the selective oxidation of styrene in the gas phase. Activity and selectivity were strongly dependent on the morphology of the silver nanoparticles.
- Chimentao,Kirm,Medina,Rodriguez,Cesteros,Salagre,Sueiras
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- A Convenient Synthesis of Aldehydes by Rearrangement of Cyclic Epoxides with Lithium Bromide on Alumina
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Epoxides can be converted effectively to aldehydes by rearrangement with lithium bromide supported on alumina.In the case of the alicyclic epoxides, ring contracted cycloalkanecarbaldehydes can be formed.The conversion is achieved by gas-phase reaction or in toluene as solvent.
- Suga, Hisashi,Miyake, Hajimu
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- First catalysis by corrole metal complexes: Epoxidation, hydroxylation, and cyclopropanation
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The first ever application of corroles shows that their metal complexes are good catalysts, almost as potent as the corresponding metalloporphyrins in the oxygenation of hydrocarbons by iodosylbenzene and superior for the cyclopropanation of olefins by carbenoids.
- Gross, Zeev,Simkhovich, Liliya,Galili, Nitsa
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- One-Pot Synthesis of N-tert-Butylsulfinylimines and Homoallylamine Derivatives from Epoxides
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The reaction of epoxides with tert-butanesulfinamide in the presence of a Lewis acid, such as erbium triflate or boron trifluoride–diethyl ether, in THF as solvent, under microwave or thermal activation, produces N-tert-butylsulfinylimines in reasonable yields. Aromatic and gem-disubstituted and trisubstituted alkyl epoxides performed better than mono-alkyl-substituted compounds. After imine formation, a subsequent indium-promoted allylation can be carried out in the same reaction flask in a single synthetic operation leading to homoallylamine derivatives with generally high yields.
- Lahosa, Alejandro,Foubelo, Francisco,Yus, Miguel
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- Productive asymmetric styrene epoxidation based on a next generation electroenzymatic methodology
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We have established a novel and scalable methodology for the productive coupling of redox enzymes to reductive electrochemical cofactor regeneration relying on efficient mass transfer of the cofactor to the electron-delivering cathode. Proof of concept is
- Ruinatscha, Reto,Dusny, Christian,Buehler, Katja,Schmid, Andreas
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- Organosilyl Iron Carbonyl Complexes: Synthesis and Reactivity towards Alkynes and Nitriles
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The di-iron complex 2, readily obtained from Fe(CO)5 and Ph2SiH2 under photochemical conditions, react with the alkynes to yield the new mono- and bi-metallic complexes (R = Ph, Me, or Et) and ; the former complexes convert nitriles into aldehydes via disylilated enamines.
- Corriu, Robert J. P.,Moreau, Joel J. E.
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- Kinetics and mechanism of oxidation of neutral α-amino acids by sodium N-chloro-p-toluenesulfon-amide in acid medium
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Kinetics of oxidation of α-amino acids, glycine, valine, alanine, and phenylalanine, by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) has been investigated in HClO4 medium at 30°C. The rate shows first-order dependence on both CAT and amino acid concentrations and an inverse first-order on [H+]. The variation of ionic strength and the addition of p-toluenesulfonamide and Cl- ion had no effect on the reaction rate. Decrease of dielectric constant of the medium by increasing the MeOH content decreased the rate. Rate studies in D2O medium showed the inverse solvent-isotope effect of kD(2)O/kH(2)O = 0.50. Proton-inventory studies were carried out using H2O-D2O mixtures. The activation parameters have been computed. The proposed mechanism and the derived rate law are consistent with the observed kinetic data. An isokinetic relationship is observed with β = 323 K, indicating enthalpy as a controlling factor. The rate of oxidation increases in the following order: Gly Val Phe Ala.
- Rangappa,Manjunathaswamy,Raghavendra,Made Gowda
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- Oxidation of alcohols by iodine in the presence of nitroxyl radicals generated electrochemically
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Oxidation of primary and secondary alcohols in the two-phase system of methylene chloride-aqueous solution of sodium hydrocarbonate in the presence of the mediator system of potassium iodide-nitroxyl radical was studied. It is supposed that under these co
- Kagan,Kashparova,Zhukova,Kashparov
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- Two inorganic–organic hybrids based on a polyoxometalate: Structures, characterizations, and epoxidation of olefins
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Two new inorganic–organic hybrids, [Co3(bpdo)6(H2O)4Cl2][SiW12O40]·H2O (Co-SiW) and [Ni3(bpdo)6(H2O)4Cl2][SiW12O40]·H2O (Ni-SiW) (bpdo?=?4,4′-bis(pyridine-N-oxide)), were synthesized from the Keggin-type [SiW12O40] anion and Co(II) and Ni(II) under hydrothermal conditions, respectively, and characterized by elemental analyses, powder XRD, IR spectra, and single-crystal X-ray diffraction. The structural analysis indicates that the 1D chain is constructed from a POM-based half-cage as a secondary building block linked by bridging bpdo ligands. The zigzag chains further stack into a three-dimensional body with channels. The 3D network structure with amphiphilic cavities is shaped by electrostatic interactions through the planes, which has potential to allow molecules such as styrene and H2O2 ingress and egress. Both of the hybrids demonstrated catalytic activity for epoxidation of olefins, which was examined using styrene and aqueous hydrogen peroxide (30%) as oxidant in acetonitrile, along with Co-SiW and Ni-SiW in a heterogeneous manner at 60?°C. Moreover, the conversion of epoxidation reaction in a heterogeneous manner is close to that of homogeneous catalysis, while being conveniently recovered and steadily reused without change of catalyst structure after epoxidation reactions.
- Shi, Zhuolin,Mei, Chongzhen,Niu, Guiqin,Han, Qiuxia
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- Epoxidation of alkenes with aqueous hydrogen peroxide and quaternary ammonium bicarbonate catalysts
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A range of solid and liquid catalysts containing bicarbonate anions were synthesised and tested for the epoxidation of alkenes with aqueous hydrogen peroxide. The combination of bicarbonate anions and quaternary ammonium cations opens up for new catalytic systems that can help to overcome challenges with catalyst separation and reuse. Graphical Abstract: [Figure not available: see fulltext.]
- Mielby, Jerrik,Kegnaes, Soren
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- Hydrogen peroxide dependent monooxygenations by tricking the substrate recognition of cytochrome P450BSβ
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(Figure Presented) Trick or treat: Cytochrome P450BSβ was transformed into a monooxygenase suitable for practical use by employing a simple substrate trick. The substrate specificity of P450BSβ was altered drastically by a decoy molecule, while its intrinsic advantage, the use of hydrogen peroxide, was retained. The catalytic activities and the enantioselectivity of the H2O2-P450BSβ system are highly dependent on the structure of the decoy molecule.
- Shoji, Osami,Fujishiro, Takashi,Nakajima, Hiroshi,Kim, Misa,Nagano, Shingo,Shiro, Yoshitsugu,Watanabe, Yoshihito
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- Novelties of combustion synthesized and functionalized solid superacid catalysts in selective isomerization of styrene oxide to 2-phenyl acetaldehyde
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Combustion synthesis leads to very interesting characteristics to inorganic oxides which could be further modified to render them catalytic properties. Several new approaches were studied to make a novel superacidic sulfated zirconia called fuel lean sulfated zirconia (FLSZ), by combustion synthesis. FLSZ was fully characterized and used in a reaction of industrial relevance. The isomerization of styrene oxide to 2-phenyl acetaldehyde was studied by using several solid acid catalysts. 2-Phenyl acetaldehyde finds applications in the synthesis of fine chemicals, intermediates, speciality chemicals, flavors and fragrances. Among various catalysts studied FLSZ was found to give the best activity and selectivity to 2-phenyl acetaldehyde at 100 °C using cyclohexane as a solvent. Process parameters were optimized by conducting a systematic investigation. The kinetics of the reaction was also studied. The catalyst is robust, recyclable and found to be highly active and selective. The overall process is 100% atom economical, green and clean.
- Yadav, Ganapati D.,Gawade, Bapu A.
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- KINETICS AND MECHANISM OF THE OXIDATION OF α-AMINO ACIDS BY N-BROMOACETAMIDE
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The kinetics of the oxidation of eight α-amino acids by N-bromoacetamide have been studied in aqueous perchloric acid solution.The main products of the oxidation are the corresponding carbonyl compounds.The reaction is of first order with respect to the oxidant and the amino acid.The rate of oxidation decreases linearly with an increase in hydrogen ion concentration.The rate is decreased by the addition of acetamide.The oxidation of deuteriated glycine indicated the absence of a primary kinetic isotope effect.The reaction rate has been determined at different temperatures and activation parameters have been caculated.Hypobromous acid has been postulated as the reactive oxidizing species.A rate-determining reaction of the neutral amino acid and hypobromous acid to give an N-bromo derivative has been proposed.The slow step is followed by a fast decomposition of the N-bromo derivative to yield the ultimate product.
- Bishnoi, Mangi Lal,Banerji, Kalyan K.
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- 4,6-Diacetyl Resorcinol Based Vanadium(V) Complexes: Reactivity and Catalytic Applications
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Four ONO donor ligands are isolated from the condensation of 4,6-diacetyl resorcinol with isonicotinoyl hydrazide (H2dar-inh, I), nicotinoyl hydrazide (H2dar-nah, II), benzoyl hydrazide (H2dar-bhz, III), and 2-furoyl hydrazide (H2dar-fah, IV) on refluxing in MeOH. The reaction of in situ generated aqueous K[H2VVO4] with ligands I–IV at neutral pH gives complexes [K(H2O)2][VO2(dar-inh)] (1), [K(H2O)2][VO2(dar-nah)] (2), [K(H2O)2][VO2(dar-bhz)] (3), and [K(H2O)2][VO2(dar-fah)] (4), respectively. The reaction of [VIVO(acac)2] (acac = acetylacetonato) with these ligands (I–IV) under aerobic conditions in methanol yields oxidomethoxidovanadium(V) complexes [VO(OMe)(MeOH)(dar-inh)] (5), [VO(OMe)(MeOH)(dar-nah)] (6), [VO(OMe)(MeOH)(dar-bhz)] (7), and [VO(OMe)(MeOH)(dar-fah)] (8). All the isolated complexes are characterized by elemental, thermal, electrochemical, and spectroscopic techniques [FTIR, UV/Vis, NMR (1H, 13C and 51V NMR)], and single-crystal X-ray diffraction analysis (for 1, 6, 7, and 8). X-ray analysis confirms the coordination of the ligands through Ophenolate, Nazomethine, and Oenolate to the metal center. In the molecular structure of [K(H2O)(EtOH)][VVO2(dar-inh)] (abbreviated as 1a where one molecule of water is replaced by EtOH), water molecules act as bridges between two K+ ions and the complex shows a dimeric structure due to the presence of electrostatic interactions between V=O oxygen atoms with K+ ions. These complexes are active catalysts for the oxidative bromination of thymol in the presence of KBr, HClO4, and H2O2 and give 2-bromothymol, 4-bromothymol, and 2,4-dibromothymol as major products. Complexes 1–4 were also tested as catalysts for the epoxidation of various alkenes (namely styrene, cyclohexene, cis-cyclooctene, 1-hexene, 1-octene, cyclohexenone, and trans-stilbene) with H2O2 in the presence of NaHCO3 as promoter, giving the corresponding epoxides selectively.
- Maurya, Mannar R.,Jangra, Nancy,Avecilla, Fernando,Correia, Isabel
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- Simple green dehydration in biphasic medium: Application to the synthesis of phenylacetaldehyde
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A highly efficient, simple and versatile acid catalyst is proposed for the selective acid dehydration of 1-phenylethan-1,2-diol to phenylacetaldehyde in water-CPME biphasic media under microwave irradiation. A high stability and recyclability of the catalyst is also observed under the investigated conditions.
- Le Guenic, Sarah,Ceballos, Claire,Len, Christophe
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- Catalytic Oxidation of Styrene in the Presence of Square Planar Cobalt(III) Complexes of Polyanionic Chelating Ligands
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Styrene has been catalytically oxidised in the presence of iodosoarenes and square planar cobalt(III) complexes of polyanionic chelating (PAC) ligands; possible intermediates in these oxygen atom transfer reactions include cobalt(V)-oxo complexes.
- Collins, Terrence J.,Ozaki, Shigeko,Richmond, Thomas G.
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- Controlled light-induced release of volatile aldehydes and ketones by photofragmentation of 2-oxo-(2-phenyl)acetates
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The light-induced controlled release of fragrances from photolabile 2-oxo-(2-phenyl)acetates via Norrish Type II photofragmentation was evaluated by irradiation of the precursors in different solvents and on cotton in a typical fabric softener application. The desired photooxidation was found to work efficiently in water-based systems, and it tolerates the presence of oxygen. The formation of a certain amount of alcohol besides the desired aldehyde or ketone was attributed to further reaction of the photochemically released carbonyl compound, rather than to ester hydrolysis in an aqueous environment. Schweizerische Chemische Gesellschaft.
- Levrand, Barbara,Herrmann, Andreas
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- Chemical conversion of α-amino acids into α-keto acids by 4,5-epoxy-2-decenal
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The comparative formation of phenylalanine and phenylpyruvic acid in the reaction of 4,5-epoxy-2-decenal with phenylalanine was studied to determine whether epoyalkenals may also degrade amino acids without producing their decarboxylation. Both compounds were produced in the reaction to an extent that depended on the reaction pH, the amount of lipid oxidation product, and the reaction time and temperature. The optimum pH was 3 for producing both carbonyl derivatives, and the amount of both compounds increased linearly with the amount of epoxyalkenal present in the reaction mixture. In addition, phenylpyruvic acid was produced to a higher extent than phenylacetaldehyde at 37°C. However, at 60°C the degradation of phenylpyruvic acid was observed and phenylacetaldehyde was usually found to a higher extent than the α-keto acid in the overnight-incubated reaction mixtures. The degradation of phenylpyruvic acid produced benzaldehyde and phenylacetaldehyde. All these results suggest that epoxyalkenals can not only degrade amino acids by a Strecker-type mechanism but convert them into their corresponding α-keto acids. This new reaction may be an alternative chemical route for the formation in foods of α-keto acids, which can later participate in the generation of important amino acid-derived flavor compounds.
- Zamora, Rosario,Navarro, Jose L.,Gallardo, Emerenciana,Hidalgo, Francisco J.
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- Synthesis of meta-substituted monodentate phosphinite ligands and implication in hydroformylation ?
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Abstract: Synthesis of meta-substituted phosphinite ligands 3,3′-(methoxyphosphanediyl)bis(N,N- diethylaniline) (4a) and methoxybis(3-methoxyphenyl)phosphane (4b), in high yields, has been demonstrated. Typical phosphorus chemical shift between 110–120 ppm, appearance of methoxy protons and corresponding carbon, as well as ESI-MS spectra unambiguously confirmed the existence of phosphinite ligands 4a and 4b. To demonstrate the synthetic usefulness of 4a and 4b, these ligands were tested in the rhodium catalyzed hydroformylation of 1-octene. The diethylamine substituted ligand 4a was found to be highly active, whereas 4b was less reactive but revealed slightly better regioselectivity of 62% under optimized conditions. Additionally, 4a and 4b were found to catalyze the hydroformylation of styrene, 1-undecenol and 1,1-disubstituted functional olefin, methyl methacrylate. Both the ligands displayed excellent conversion of styrene, and 4b revealed an excellent branch selectivity of 75%. Although 1-undecenol proved to be amenable to hydroformylation (85–90% conversion to aldehyde), both the ligands failed to discriminate between the linear and branched products. Substrate methyl methacrylate proved to be highly challenging and reduced conversion (between 33–42%) was observed under optimized conditions. Ligand 4a was found to be highly selective towards linear aldehyde (81% linear selectivity). Graphical Abstract: Synopsis Two step synthetic protocol to access meta-substituted monodentate phosphinite ligands 3,3′-(methoxyphosphanediyl)bis(N,N-diethylaniline) (4a) and methoxybis(3-methoxyphenyl)phosphane (4b) has been developed and the ligands have been fully characterized. Apart from catalyzing the hydroformylation of benchmark substrates 1-octene and styrene, 4a and 4b were found to catalyze the hydroformylation of 1-undecenol, a functional olefin and a highly challenging 1,1-disubstituted functional olefin methyl methacrylate. [Figure not available: see fulltext.].
- Deshmukh, Satej S,Gaikwad, Shahaji R,Pandey, Swechchha,Mali, Pramod S,Chikkali, Samir H
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- Rapid and efficient protic ionic liquid-mediated pinacol rearrangements under microwave irradiation
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Several protic ionic liquids were tested as potential mediators for pinacol rearrangements employing microwave irradiation. Using hydrobenzoin as a model substrate, the optimal conditions were found to be heating at 80°C for 5 min using H2SO4:triethylamine as the ionic liquid. A key feature of this reaction was to keep the microwave power low (20 W) to avoid ionic liquid degradation. Application of these conditions to triphenylethylene glycol gave rearrangement products in high yield and purity, while phenylethylene glycol and styrene oxide gave pinacol products that underwent a cascade aldol condensation. These conditions represent an efficient means by which pinacol rearrangements can be carried out while avoiding the use of strong Bronsted acids, high temperatures and extended reaction times. The Royal Society of Chemistry.
- Henderson, Luke C.,Byrne, Nolene
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- Flash Photolytic Decarbonylation and Ring-Opening of 2-(N-(Pentafluorophenyl)amino)-3-phenylcyclopropenone. Isomerization of the Resulting Ynamine to a Ketenimine, Hydration of the Ketenimine, and Hydrolysis of the Enamine Produced by Ring-Opening
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Flash photolysis of 2-(N-(pentafluorophenyl)amino)-3-phenylcyclopropenone, 4, in aqueous solution was found to produce N-(pentafluorophenyl)phenylethynamine, 3, by the expected photodecarbonylation reaction and also 2-phenyl-3-(N-(pentafluorophenyl)amino)acrylic acid, 5, by an apparently unprecedented photochemical ring-opening process. The ynamine underwent rapid isomerization to N-(pentafluorophenyl)phenylketenimine, 9, by an acid-catalyzed route that involves rate- determining proton transfer to the β-carbon atom of the ynamine and also by a base-catalyzed route involving equilibrium ionization of the N-H bond of the ynamine to give an ynamide ion followed by rate-determining β-carbon protonation of this ion. Saturation of the base catalysis allowed determination of the acidity constant of the ynamine; the result, pQa = 10.23, makes this amine a remarkably strong nitrogen acid. Hydration of the ketenimine 9 gave N-(pentafluorophenyl)phenylacetamide, 6, as the ultimate product produced by this reaction route, and hydrolysis of the aminoacrylic acid 5 gave pentafluoroaniline, 7, and 2-phenylformylacetic acid, 10, which underwent decarboxylation to phenylacetaldehyde, 8, as the ultimate products of this route.
- Chiang,Grant,Guo,Kresge,Paine
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- Intensification and economic and ecological assessment of a biocatalytic oxyfunctionalization process
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Bio-based processes are commonly accepted to be environmentally preferable to chemical alternatives. Reasons include high selectivities, the avoidance of heavy metals, and mild reaction conditions. However, ecological benefits and economic viability have to be verified in each case. Oxygenases are a very attractive enzyme class, allowing selective oxyfunctionalization by introduction of molecular oxygen into hydrocarbons at optical purities unparalleled by traditional chemical methods. Here, styrene monooxygenase from Pseudomonas sp. strain VLB120 was used in recombinant Escherichia coli for the production of enantiopure (S)-styrene oxide from styrene. Substrate and product toxicity was attenuated using a two-liquid phase system with bis(2-ethylhexyl)phthalate as organic carrier solvent. By maintaining previously reported productivities for a longer time period, product concentrations were doubled to 36.3 g L tot-1 making it one of the most productive biocatalytic oxyfunctionalization processes. This biotransformation was incorporated along with an appropriate upstream and downstream processing into a complete process scheme and compared with chemical process alternatives. Ecological assessment showed the bioprocess to be superior to two chemical process alternatives and slightly inferior to the third one, with solvent use being the most critical factor. However, the bioprocess performed best in terms of production costs ($10.2 kg-1). This study underlines the importance of a detailed ecological and economic assessment of bioprocesses to verify their sustainability and to identify weak points with respect to environmental and/or economical sustainability.
- Kuhn, Daniel,Kholiq, Muhammad Abdul,Heinzle, Elmar,Buehler, Bruno,Schmid, Andreas
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- Intermolecular Electrophilic Addition of Epoxides to Alkenes: [3+2] Cycloadditions Catalyzed by Lewis Acids
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Described are the first examples of intermolecular electrophilic additions of epoxides to alkenes, which proceed through a classic cationic mechanism initiated by epoxide C–O bond cleavage. Treatment of styrene oxides and either styrenes or dienes with a variety of Lewis-acidic triflate salts generates tetrahydrofurans as products of [3+2] cycloaddition in moderate to good yields (up to 71 %). Careful choice of catalyst and reaction conditions favors the desired intermolecular reaction over epoxide degradation without requiring additional reagents or additives. The reaction proceeds diastereoselectively and provides only one regioisomer of the product. Additional highlights include inexpensive precursors, mild conditions, short reaction times, low catalyst loading, and scalability.
- Shuler, William G.,Combee, Logan A.,Falk, Isaac D.,Hilinski, Michael K.
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- Highly efficient Meinwald rearrangement reactions of epoxides catalyzed by copper tetrafluoroborate
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Epoxides undergo a highly efficient and selective rearrangement in the presence of catalytic quantities of copper tetrafluoroborate to give carbonyl compounds in excellent yields. The low toxicity and ease of handling of this reagent make it an attractive alternative to the more corrosive Lewis acids frequently employed.
- Robinson, Mathew W.C.,Pillinger, Kathryn S.,Graham, Andrew E.
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- Oxidation of L-phenylalanine by diperiodatoargentate(III) in aqueous alkaline medium. A Mechanistic approach
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The kinetics of oxidation of L-phenylalanine (L-Phe) by diperiodatoargentate(III) (DPA) in alkaline medium at a constant ionic strength of 0.25 mol/dm-3 has been studied spectrophotometrically. The reaction between DPA and L-phenylalanine in alkaline medium exhibits 1: 1 stoichiometry (L-phenylalanine: DPA). The reaction shows first order in [DPA] and has less than unit order dependence each in both [L-Phe] and [Alkali] and retarding effect of [IO 4 - ] under the reaction conditions. The active species of DPA is understood to be as monoperiodatoargentate(III) (MPA). The reaction is shown to proceed via a MPA-L-Phe complex, which decomposes in a rate-determining step to give intermediates followed by a fast step to give the products. The products were identified by spot and spectroscopic studies. The reaction constants involved in the different steps of the mechanisms were calculated. The activation parameters with respect to slow step of the mechanism were computed and discussed. The thermodynamic quantities were also determined for the reaction.
- Lamani,Veeresh,Nandibewoor
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- Palladium-catalyzed anti-Markovnikov oxidative acetalization of activated olefins with iron(iii) sulphate as the reoxidant
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This paper discloses the efficient palladium-catalyzed anti-Markovnikov oxidative acetalization of activated terminal olefins with iron(iii) sulfate as the reoxidant. This methodology requires mild reaction conditions and shows high regioselectivity toward anti-Markovnikov products and compatibility with a wide range of functional groups. Iron(iii) sulphate was the sole reoxidant used in this method. Various olefins like vinylarenes, aryl-allylethers, aryl or benzyl acrylates and homoallylic alcohols all reacted well providing anti-Markovnikov acetals, some of which represent orthogonally functionalized 1,3- and 1,4-dioxygenated compounds.
- Fernandes, Rodney A.,Kumar, Praveen,Yadav, Sandhya S.
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p. 427 - 443
(2022/01/20)
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- Direct synthesis of 1,3-dithiolanes from terminal alkynes: Via visible light photoredox catalysis
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A visible light-mediated, metal-free, regioselective dihydrothionation of terminal aromatic as well as heteroaromatic alkynes has been achieved using Eosin Y as a photoredox catalyst at room temperature. The protocol gives direct access to different 1,3-dithiolanes under neutral and mild reaction conditions without the use of any base or additives. The electron-donating, electron-withdrawing and electron-deactivating groups tolerated the photocatalytic reaction conditions. The control experiments, cyclic voltammetry, and Stern-Volmer experiment were carried out to gain an insight into the mechanistic pathway. The protocol proved to be scalable at the gram level and also for practicality the deprotection of 1,3-dithiolanes has been demonstrated. The method uses clean energy under sustainable conditions. This journal is
- Bhat, Ramakrishna G.,Dharpure, Pankaj D.,Khade, Vikas V.,Thube, Archana S.
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supporting information
p. 1315 - 1319
(2022/02/21)
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- One-Pot Bioelectrocatalytic Conversion of Chemically Inert Hydrocarbons to Imines
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Petroleum hydrocarbons are our major energy source and an important feedstock for the chemical industry. With the exception of combustion, the deep conversion of chemically inert hydrocarbons to more valuable chemicals is of considerable interest. However, two challenges hinder this conversion. One is the regioselective activation of inert carbon-hydrogen (C-H) bonds. The other is designing a pathway to realize this complicated conversion. In response to the two challenges, a multistep bioelectrocatalytic system was developed to realize the one-pot deep conversion from heptane to N-heptylhepan-1-imine under mild conditions. First, in this enzymatic cascade, a bioelectrocatalytic C-H bond oxyfunctionalization step based on alkane hydroxylase (alkB) was applied to regioselectively convert heptane to 1-heptanol. By integrating subsequent alcohol oxidation and bioelectrocatalytic reductive amination steps based on an engineered choline oxidase (AcCO6) and a reductive aminase (NfRedAm), the generated 1-heptanol was successfully converted to N-heptylhepan-1-imine. The electrochemical architecture provided sufficient electrons to drive the bioelectrocatalytic C-H bond oxyfunctionalization and reductive amination steps with neutral red (NR) as electron mediator. The highest concentration of N-heptylhepan-1-imine achieved was 0.67 mM with a Faradaic efficiency of 45% for C-H bond oxyfunctionalization and 70% for reductive amination. Hexane, octane, and ethylbenzene were also successfully converted to the corresponding imines. Via regioselective C-H bond oxyfunctionalization, intermediate oxidation, and reductive amination, the bioelectrocatalytic hydrocarbon deep conversion system successfully realized the challenging conversion from inert hydrocarbons to imines that would have been impossible by using organic synthesis methods and provided a new methodology for the comprehensive conversion and utilization of inert hydrocarbons.
- Chen, Hui,Tang, Tianhua,Malapit, Christian A.,Lee, Yoo Seok,Prater, Matthew B.,Weliwatte, N. Samali,Minteer, Shelley D.
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supporting information
p. 4047 - 4056
(2022/02/10)
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- Controlled reduction of activated primary and secondary amides into aldehydes with diisobutylaluminum hydride
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A practical method is disclosed for the reduction of activated primary and secondary amides into aldehydes using diisobutylaluminum hydride (DIBAL-H) in toluene. A wide range of aryl and alkyl N-Boc, N,N-diBoc and N-tosyl amides were converted into the corresponding aldehydes in good to excellent yields. Reduction susceptible functional groups such as nitro, cyano, alkene and alkyne groups were found to be stable. Broad substrate scope, functional group compatibility and quick conversions are the salient features of this methodology.
- Azeez, Sadaf,Kandasamy, Jeyakumar,Sabiah, Shahulhameed,Sureshbabu, Popuri
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supporting information
p. 2048 - 2053
(2022/03/31)
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- Copper-Photocatalyzed Hydrosilylation of Alkynes and Alkenes under Continuous Flow
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Herein, the photocatalytic hydrosilylation of alkynes and alkenes under continuous flow conditions is described. By using 0.2 mol % of the developed [Cu(dmp)(XantphosTEPD)]PF6 under blue LEDs irradiation, a large panel of alkenes and alkynes was hydrosilylated in good to excellent yields with a large functional group tolerance. The mechanism of the reaction was studied, and a plausible scenario was suggested.
- Zhong, Mingbing,Pannecoucke, Xavier,Jubault, Philippe,Poisson, Thomas
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p. 11818 - 11822
(2021/07/10)
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- Samarium-based Grignard-type addition of organohalides to carbonyl compounds under catalysis of CuI
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Grignard-type additions were readily achieved under the mediation of CuI (10 mol%) and samarium (2 equiv.) by employing various organohalides,e.g.benzyl, aryl, heterocyclic and aliphatic halides (Cl, Br or I), and diverse carbonyl compounds (e.g.carbonic esters, carboxylic esters, acid anhydrides, acyl chlorides, ketones, aldehydes, propylene epoxides and formamides) to afford alcohols, ketones and aldehydes, respectively, with high efficiency and chemoselectivity, in which the organosamarium intermediate might be involved.
- Liu, Chen,Liu, Yongjun,Qi, Yan,Song, Bin,Wang, Liang,Xiao, Shuhuan
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supporting information
p. 6169 - 6172
(2021/06/30)
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- Structural elucidation, DFT calculations and catalytic activity of dioxomolybdenum(VI) complexes with N–N donor ligand: Role of halogen atom coordinated to the molybdenum centre
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Two new isostructural mononuclear dioxomolybdenum(VI) complexes of the formula MoO2X2L [where, X = Cl (1), Br (2)] have been synthesized with a N–N donor 2-(3-methyl-5-phenyl pyrazol-1-yl) benzthiazole ligand (L). The reaction is carried out in open air and the MoVO3+ centre in the precursor molecule, MoOX3L undergoes spontaneous aerial oxidation, leading to the formation of molybdenum(VI) complexes 1 and 2. The complexes are characterized by a wide range of spectroscopic techniques (IR, UV–Vis and 1H NMR) and elemental analyses. Crystal structures of the ligand and complexes 1 and 2 have been determined by single crystal X-ray diffraction which reveal a distorted octahedral geometry around the molybdenum(VI) centre in both the complexes. The ligand and the complexes build up fascinating supramolecular assembly via several non-covalent interactions including hydrogen bonding, C–H···π and π···π interactions. Further, a detailed study of Hirshfeld surface analysis and fingerprint plots of complexes 1 and 2 are presented for understanding the intermolecular interactions involved in building self-assembled frameworks. Supportive DFT and TD-DFT calculations have also been carried out. Electrochemical properties of the complexes have been examined by cyclic voltammetry. Catalytic performance of the synthesized complexes has been evaluated for the oxidation of different olefins in the presence of hydrogen peroxide.
- Roy, Malini,Biswal, Debanjana,Pramanik, Nikhil Ranjan,Drew, Michael G.B.,Paul, Suvendu,Kachhap, Payal,Haldar, Chanchal,Chakrabarti, Syamal
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- Oxygen atom transfer catalysis by dioxidomolybdenum(VI) complexes of pyridyl aminophenolate ligands
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A series of new cationic dioxidomolybdenum(VI) complexes [MoO2(Ln)]PF6 (2–5) with the tripodal tetradentate pyridyl aminophenolate ligands HL2-HL5 have been synthesized and characterized. Ligands HLs
- Kamal Hossain, Md,Schachner, J?rg A.,Haukka, Matti,Richmond, Michael G.,M?sch-Zanetti, Nadia C.,Lehtonen, Ari,Nordlander, Ebbe
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- Structural and Biochemical Studies Enlighten the Unspecific Peroxygenase from Hypoxylon sp. EC38 as an Efficient Oxidative Biocatalyst
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Unspecific peroxygenases (UPOs) are glycosylated fungal enzymes that can selectively oxidize C-H bonds. UPOs employ hydrogen peroxide as the oxygen donor and reductant. With such an easy-to-handle cosubstrate and without the need for a reducing agent, UPOs are emerging as convenient oxidative biocatalysts. Here, an unspecific peroxygenase from Hypoxylon sp. EC38 (HspUPO) was identified in an activity-based screen of six putative peroxygenase enzymes that were heterologously expressed in Pichia pastoris. The enzyme was found to tolerate selected organic solvents such as acetonitrile and acetone. HspUPO is a versatile catalyst performing various reactions, such as the oxidation of prim- and sec-alcohols, epoxidations, and hydroxylations. Semipreparative biotransformations were demonstrated for the nonenantioselective oxidation of racemic 1-phenylethanol rac-1b (TON = 13 000), giving the product with 88% isolated yield, and the oxidation of indole 6a to give indigo 6b (TON = 2800) with 98% isolated yield. HspUPO features a compact and rigid three-dimensional conformation that wraps around the heme and defines a funnel-shaped tunnel that leads to the heme iron from the protein surface. The tunnel extends along a distance of about 12 ? with a fairly constant diameter in its innermost segment. Its surface comprises both hydrophobic and hydrophilic groups for dealing with substrates of variable polarities. The structural investigation of several protein-ligand complexes revealed that the active site of HspUPO is accessible to molecules of varying bulkiness with minimal or no conformational changes, explaining the relatively broad substrate scope of the enzyme. With its convenient expression system, robust operational properties, relatively small size, well-defined structural features, and diverse reaction scope, HspUPO is an exploitable candidate for peroxygenase-based biocatalysis.
- Ebner, Katharina,Glieder, Anton,Kroutil, Wolfgang,Mattevi, Andrea,Rinnofner, Claudia,Rotilio, Laura,Swoboda, Alexander
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p. 11511 - 11525
(2021/09/22)
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- Manganese-catalysed divergent silylation of alkenes
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Transition-metal-catalysed, redox-neutral dehydrosilylation of alkenes is a long-standing challenge in organic synthesis, with current methods suffering from low selectivity and narrow scope. In this study, we report a general and simple method for the manganese-catalysed dehydrosilylation and hydrosilylation of alkenes, with Mn2(CO)10 as a catalyst precursor, by using a ligand-tuned metalloradical reactivity strategy. This enables versatility and controllable selectivity with a 1:1 ratio of alkenes and silanes, and the synthetic robustness and practicality of this method are demonstrated using complex alkenes and light olefins. The selectivity of the reaction has been studied using density functional theory calculations, showing the use of an iPrPNP ligand to favour dehydrosilylation, while a JackiePhos ligand favours hydrosilylation. The reaction is redox-neutral and atom-economical, exhibits a broad substrate scope and excellent functional group tolerance, and is suitable for various synthetic applications on a gram scale. [Figure not available: see fulltext.].
- Dong, Jie,Yuan, Xiang-Ai,Yan, Zhongfei,Mu, Liying,Ma, Junyang,Zhu, Chengjian,Xie, Jin
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p. 182 - 190
(2020/12/17)
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- Enhancing the activity, selectivity, and recyclability of Rh/PPh3 system-catalyzed hydroformylation reactions through the development of a PPh3-derived quasi-porous organic cage as a ligand
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In contrast to heterogeneous network frameworks (e.g., covalent organic frameworks and metal-organic frameworks) and porous organic polymers, porous organic cages (POCs) are soluble molecules in common organic solvents that provide significant potential for homogeneous catalysis. Herein, we report a triphenylphosphine-derived quasi-porous organic cage (denoted as POC-DICP) as an efficient organic molecular cage ligand for Rh/PPh3 system-catalyzed homogeneous hydroformylation reactions. POC-DICP not only displays enhanced hydroformylation selectivity (aldehyde selectivity as high as 97% and a linear-to-branch ratio as high as 1.89) but can also be recovered and reused via a simple precipitation method in homogeneous reaction systems. We speculate that the reason for the high activity and good selectivity is the favorable geometry (cone angle = 123.88°) and electronic effect (P site is relatively electron-deficient) of POC-DICP, which were also demonstrated by density functional theory calculations and X-ray absorption fine-structure characterization.
- Wang, Wenlong,Li, Cunyao,Zhang, Heng,Zhang, Jiangwei,Lu, Lanlu,Jiang, Zheng,Cui, Lifeng,Liu, Hongguang,Yan, Li,Ding, Yunjie
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p. 1216 - 1226
(2021/03/06)
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- Manganese vacancy-confined single-atom Ag in cryptomelane nanorods for efficient Wacker oxidation of styrene derivatives
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Single-atom catalysts provide a pathway to elucidate the nature of catalytically active sites. However, keeping them stabilized during operation proves to be challenging. Herein, we employ cryptomelane-type octahedral molecular sieve nanorods featuring abundant manganese vacancy defects as a support, to periodically anchor single-atom Ag. The doped Ag atoms with tetrahedral coordination are found to locate at cation substitution sites rather than being supported on the catalyst surface, thus effectively tuning the electronic structure of adjacent manganese atoms. The resulting unique Ag-O-MnOx unit functions as the active site. Its turnover frequency reaches 1038 h-1, one order of magnitude higher than for previously reported catalysts, with 90% selectivity for anti-Markovnikov phenylacetaldehyde. Mechanistic studies reveal that the activation of styrene on the ensemble site of Ag-O-MnOx is significantly promoted, which can accelerate the oxidation of styrene and, in particular, the rate-determining step of forming the epoxide intermediate. Such an extraordinary electronic promotion can be extended to other single-atom catalysts and paves the way for their practical applications.
- Yang, Hongling,Zhang, Xun,Yu, Yi,Chen, Zheng,Liu, Qinggang,Li, Yang,Cheong, Weng-Chon,Qi, Dongdong,Zhuang, Zewen,Peng, Qing,Chen, Xin,Xiao, Hai,Chen, Chen,Li, Yadong
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p. 6099 - 6106
(2021/05/17)
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- Nonheme manganese(III) complexes for various olefin epoxidation: Synthesis, characterization and catalytic activity
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Three mononuclear imine-based non-heme manganese(III) complexes with tetradentate ligands which have two deprotonated phenolate moieties, ([(X2saloph)Mn(OAc)(H2O)], 1a for X = Cl, 1b for X = H, and 1c for X = CH3, saloph = N,N-o-phenylenebis(salicylidenaminato)), were synthesized and characterized by 1H NMR, 13C NMR, ESI-Mass and elemental analysis. MnIII complexes catalysed efficiently various olefin epoxidation reactions with meta-chloroperbenzoic acid (MCPBA) under the mild condition. MnIII complexes 1a and 1c with the electron-withdrawing group -Cl and electron-donating group –CH3 showed little substituent effect on the epoxidation reactions. Product analysis, Hammett study and competition experiments with cis- and trans-2-octene suggested that MnIV = O, MnV = O, and MnIII-OOC(O)R species might be key oxidants in the epoxidation reaction under this catalytic system. In addition, the use of PPAA as a mechanistic probe demonstrated that Mn-acylperoxo intermediate (MnIII-OOC(O)R) 2 generated from the reaction of peracid with manganese complexes underwent both the heterolysis and the homolysis to produce MnV = O (3) or MnIV = O species (4). Moreover, the MnIII-OOC(O)R 2 species could react directly with the easy-to-oxidize substrate to give epoxide, whereas the species 2 might not be competent to the difficult-to-oxidize substrate for the epoxidation reaction.
- Lee, Sojeong,Park, Soyoung,Lee, Myoung Mi,Lee, Jiyoung,Kim, Cheal
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- Proton Switch in the Secondary Coordination Sphere to Control Catalytic Events at the Metal Center: Biomimetic Oxo Transfer Chemistry of Nickel Amidate Complex
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High-valent metal-oxo species are key intermediates for the oxygen atom transfer step in the catalytic cycles of many metalloenzymes. While the redox-active metal centers of such enzymes are typically supported by anionic amino acid side chains or porphyrin rings, peptide backbones might function as strong electron-donating ligands to stabilize high oxidation states. To test the feasibility of this idea in synthetic settings, we have prepared a nickel(II) complex of new amido multidentate ligand. The mononuclear nickel complex of this N5 ligand catalyzes epoxidation reactions of a wide range of olefins by using mCPBA as a terminal oxidant. Notably, a remarkably high catalytic efficiency and selectivity were observed for terminal olefin substrates. We found that protonation of the secondary coordination sphere serves as the entry point to the catalytic cycle, in which high-valent nickel species is subsequently formed to carry out oxo-transfer reactions. A conceptually parallel process might allow metalloenzymes to control the catalytic cycle in the primary coordination sphere by using proton switch in the secondary coordination sphere.
- Kim, Soohyung,Jeong, Ha Young,Kim, Seonghan,Kim, Hongsik,Lee, Sojeong,Cho, Jaeheung,Kim, Cheal,Lee, Dongwhan
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supporting information
p. 4700 - 4708
(2021/02/12)
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- Enthalpy-Entropy Compensation Effect in Oxidation Reactions by Manganese(IV)-Oxo Porphyrins and Nonheme Iron(IV)-Oxo Models
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"Enthalpy-Entropy Compensation Effect"(EECE) is ubiquitous in chemical reactions; however, such an EECE has been rarely explored in biomimetic oxidation reactions. In this study, six manganese(IV)-oxo complexes bearing electron-rich and -deficient porphyrins are synthesized and investigated in various oxidation reactions, such as hydrogen atom transfer (HAT), oxygen atom transfer (OAT), and electron-transfer (ET) reactions. First, all of the six Mn(IV)-oxo porphyrins are highly reactive in the HAT, OAT, and ET reactions. Interestingly, we have observed a reversed reactivity in the HAT and OAT reactions by the electron-rich and -deficient Mn(IV)-oxo porphyrins, depending on reaction temperatures, but not in the ET reactions; the electron-rich Mn(IV)-oxo porphyrins are more reactive than the electron-deficient Mn(IV)-oxo porphyrins at high temperature (e.g., 0 °C), whereas at low temperature (e.g., -60 °C), the electron-deficient Mn(IV)-oxo porphyrins are more reactive than the electron-rich Mn(IV)-oxo porphyrins. Such a reversed reactivity between the electron-rich and -deficient Mn(IV)-oxo porphyrins depending on reaction temperatures is rationalized with EECE; that is, the lower is the activation enthalpy, the more negative is the activation entropy, and vice versa. Interestingly, a unified linear correlation between the activation enthalpies and the activation entropies is observed in the HAT and OAT reactions of the Mn(IV)-oxo porphyrins. Moreover, from the previously reported HAT reactions of nonheme Fe(IV)-oxo complexes, a linear correlation between the activation enthalpies and the activation entropies is also observed. To the best of our knowledge, we report the first detailed mechanistic study of EECE in the oxidation reactions by synthetic high-valent metal-oxo complexes.
- Guo, Mian,Zhang, Jisheng,Zhang, Lina,Lee, Yong-Min,Fukuzumi, Shunichi,Nam, Wonwoo
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supporting information
p. 18559 - 18570
(2021/11/22)
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- Catalytic study of the copper-based magnetic nanocatalyst on the aerobic oxidation of alcohols in water
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A copper-based magnetic nanocatalyst has been prepared by co-precipitation method and characterized by FESEM, EDS, TEM, XRD, XRF, ICP–OES, FTIR, and BET analysis. This new nanocatalyst displays a good activity toward the aerobic oxidation of a wide range of alcohols in water. Moreover, it is recyclable up to five following runs by simple filtration without any significant loss of its catalytic activity.
- Dehkordi, S. Saeid Saei,Albadi, Jalal,Jafari, Abbas Ali,Samimi, Heshmat Allah
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p. 2527 - 2538
(2021/03/24)
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- Method for preparing carbonyl compound by oxidizing alcohol
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The invention provides a method for preparing aldehyde or ketone by alcohol oxidation. Iron nitrate hydrate (Fe (NO) is used as a solvent. 3 )3 · 992 O). 4 - Hydroxyl -2, 2, 6, 6 - tetramethylpiperidine oxide (4 - OH-TEMPO) and carboxylic acid are catalysts, and the alcohol is oxidized to aldehydes or ketones with oxygen or air as an oxidizing agent. Compared with the prior art, water serves as a solvent, so that the pollution-free halogenated hydrocarbon or strong carcinogenic sodium nitrite (NaNO) is avoided. 2 The method is green and environment-friendly, the cost is greatly reduced, and the method is a method suitable for industrial production.
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Paragraph 0031
(2021/09/08)
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- Visible-light photocatalytic selective oxidation of C(sp3)-H bonds by anion-cation dual-metal-site nanoscale localized carbon nitride
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Selective oxidation of C(sp3)-H bonds to carbonyl groups by abstracting H with a photoinduced highly active oxygen radical is an effective method used to give high value products. Here, we report a heterogeneous photocatalytic alkanes C-H bonds oxidation method under the irradiation of visible light (λ= 425 nm) at ambient temperature using an anion-cation dual-metal-site modulated carbon nitride. The optimized cation (C) of Fe3+or Ni2+, with an anion (A) of phosphotungstate (PW123?) constitutes the nanoscale dual-metal-site (DMS). With a Fe-PW12dual-metal-site as a model (FePW), we demonstrate a A-C DMS nanoscale localized carbon nitride (A-C/g-C3N4) exhibiting a highly enhanced photocatalytic activity with a high product yield (86% conversion), selectivity (up to 99%), and a wide functional group tolerance (52 examples). The carbon nitride performs the roles of both the visible light response, and improves the selectivity for the oxidation of C(sp3)-H bonds to carbonyl groups, along with the function of A-C DMS in promoting product yield. Mechanistic studies indicate that this reaction follows a radical pathway catalyzed by a photogenerated electron and hole on A-C/g-C3N4that is mediated by thetBuO˙ andtBuOO˙ radicals. Notably, a 10 g scale reaction was successfully achieved for alkane photocatalytic oxidation to the corresponding product with a good yield (80% conversion), and high selectivity (95%) under natural sunlight at ambient temperature. In addition, this A-C/g-C3N4photocatalyst is highly robust and can be reused at least six times and the activity is maintained.
- Duan, Limei,Li, Peihe,Li, Wanfei,Liu, Jinghai,Liu, Ying,Liu, Zhifei,Lu, Ye,Sarina, Sarina,Wang, Jinghui,Wang, Yin,Wang, Yingying,Zhu, Huaiyong
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p. 4429 - 4438
(2021/07/12)
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- Introduction of a trinuclear manganese(iii) catalyst on the surface of magnetic cellulose as an eco-benign, efficient and reusable novel heterogeneous catalyst for the multi-component synthesis of new derivatives of xanthene
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In this work, the new trinuclear manganese catalyst defined as Fe3O4@NFC@NNSM-Mn(iii) was successfully manufactured and fully characterized by different techniques, including FT-IR, XRD, TEM, SEM, EDX, VSM, and ICP analysis. There have been reports of the use of magnetic catalysts for the synthesis of xanthine derivatives. The critical potential interest in the present method include short reaction time, high yields, recyclability of the catalyst, easy workup, and the ability to sustain a variety of functional groups, which give economical as well as ecological rewards. Also, the synthesized catalyst was used as a recyclable trinuclear catalyst in alcohol oxidation reactions at 40 °C. The magnetic catalyst activity of Fe3O4@NFC@NNSM-Mn(iii) could be attributed to the synergistic effects of the catalyst Fe3O4@NFC@NNS-Mn(iii) with melamine. Employing a sustainable and safe low temperature, using an eco-friendly solvent, no need to use any additive, and long-term stability and magnetic recyclability of the catalyst for at least six successive runs are the advantages of the current protocol towards green chemistry. This protocol is a benign, environmentally friendly method for heterocycle synthesis. This journal is
- Ghamari Kargar, Pouya,Bagherzade, Ghodsieh,Eshghi, Hossein
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p. 4339 - 4355
(2021/02/03)
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- Robust, highly active, and stable supported Co(ii) nanoparticles on magnetic cellulose nanofiber-functionalized for the multi-component reactions of piperidines and alcohol oxidation
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The new recyclable cobalt three-core magnetic catalyst obtained by anchoring a Schiff base ligand sector and cellulose nanofiber slings on MNP (Fe3O4) was prepared and named as MNP@CNF@ATSM-Co(ii). Separately, MNPs and CNF have adsorbent properties of great interest. In this way, this catalyst was designed to synthesize piperidine derivatives under solvent-free conditions and alcohol oxidation reactions in EtOH as the solvent. It should be noted that this catalyst is environmentally safe and does not need an external base. This MNPs@CNF@ATSM-Co(ii) separable catalyst has been evaluated using various characterization techniques such as FT-IR, XRD, FE-SEM, EDX, EDS, ICP, TGA, DLS, HRTEM, and VSM. The catalyst was compatible with a variety of benzyl alcohols, benzaldehydes, and amines derivatives, and gave complimentary coupling products with sufficient interest for all of them. The synergistic performance of Co (trinuclear) in the catalyst was demonstrated and its different homologs such as MNPs, MNPs@CNF, MNPs@CNF@ATS-Co(ii), and MNPs@CNF@ATSM-Co(ii) were separately synthesized and applied to a model reaction, and then their catalytic activity was investigated. Also, the performance of these components for the oxidation reaction of alcohols was evaluated. The advantages of the current protocol include the use of a sustainable and safe low temperature, eco-friendly solvent no additive, and long-term stability and magnetic recyclability of the catalyst for at least five successive runs, thus following green chemistry principles. This protocol is a benign and environment-friendly method for oxidation and heterocycle synthesis. This powerful super-magnetic catalyst can use its three arms to advance the reactions, displaying its power for multi-component reactions and oxidation.
- Bagherzade, Ghodsieh,Ghamari Kargar, Pouya
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p. 23192 - 23206
(2021/07/13)
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- MeOTf/KI-catalyzed efficient synthesis of 2-arylnaphthalenesviacyclodimerization of styrene oxides
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The MeOTf/KI-catalyzed synthesis of 2-arylnaphthalene derivatives from aryl ethylene oxides in alcohol under ambient conditions is described. The present protocol has a higher atom efficiency and wider substrate applicability with excellent yields. The reaction proceeded using the aryl ethylene oxides to give 2-arylnaphthalenes either in homo-coupling or in cross-coupling. The reaction could also be carried out at the gram scale in minutes.
- Chen, Chao,Xi, Chanjuan,Zhang, Zeyu,Zou, Song
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supporting information
p. 8559 - 8565
(2021/10/20)
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- Coupling of phenylacetaldehyde and styrene oxide with biorenewable alkenes in eco-friendly solvents
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Acidic cesium salt of tungstophosphoric heteropoly acid, Cs2.5H0.5PW12O40 (CsPW), is an excellent solid acid catalyst for the reaction of phenylacetaldehyde with biorenewable monoterpenic alkenes: limonene, α-terpineol, α-pinene and β-pinene. Simultaneously with a conventional oxonium-ene cyclization to give an oxabicyclo[3.3.1]nonene compound, phenylacetaldehyde undergoes Friedel-Crafts alkylation by the monoterpenes resulting in a new product with an unusual fused tetracyclic structure, obtained in ca. 80 % yield. A combined yield for both products was up to 95 %. Styrene oxide can be also used as a starting material for these reactions to give the same products in up to 85 % combined yield. A novel one-pot tandem process thus developed involves the isomerization of styrene oxide into phenylacetaldehyde and cycloaddition of the latter to the monoterpene, with both steps being catalyzed by CsPW. The reactions were performed in green solvents diethylcarbonate or anisole, which have high sustainability ranks in modern solvent selection guides, comparable to those of ethanol and water.
- Cotta, Rafaela F.,Martins, Rafael A.,da Silva Rocha, Kelly A.,Kozhevnikova, Elena F.,Kozhevnikov, Ivan V.,Gusevskaya, Elena V.
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p. 254 - 260
(2020/06/21)
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- High-Level Production of Phenylacetaldehyde using Fusion-Tagged Styrene Oxide Isomerase
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An order-of-magnitude improvement in the production of phenylacetaldehyde to 3.37 M (405 g L?1) from the enzymatic isomerisation of styrene oxide was achieved. A small ubiquitin-related modifier (SUMO) tag increases the productivity of the whole-cell biocatalytic system by enhancing the expression of active membrane-bound styrene oxide isomerase (SOI) while retaining enzyme catalytic efficiency and broad natural substrate scope. The isomerisation was performed by using Escherichia coli expressing SUMO-tagged SOI in an organic-aqueous biphasic system to yield 96% of phenylacetaldehyde. (Figure presented.).
- Choo, Joel P. S.,Kammerer, Richard A.,Li, Xiaodan,Li, Zhi
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p. 1714 - 1721
(2021/02/12)
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- Metal-free and mild photo-thermal synergism in ionic liquids for lignin Cα-Cβbond cleavage to provide aldehydes
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Direct cleavage of the C-C bond in lignin linkages is a promising route to afford value-added aromatics, which, however, usually involves metal-based catalysts and harsh conditions. Here, a photo-thermal strategy is reported to deconstruct the Cα-Cβ bond in lignin β-O-4 and β-1 interlinkages in the ionic liquid [BMim][NTf2]. It was found that the synergism of UV light and heating could trigger the Norrish type I reaction by inducing the cleavage of the Cα-Cβ bond and afford aromatic aldehydes through a free radical route in modest yields. Meanwhile, [BMim][NTf2] could interact with lignin moieties and stabilize the intermediates, which significantly contribute to the Cα-OH protonation and accelerate lignin interunit linkage breakage. In this unique route, the Cα-Cβ bond could be cleaved at 50 °C under UV light irradiation without the presence of a metal. Further comparison with photochemical or thermochemical alone strategies demonstrates that the photo-thermal route offers a significant improvement in the Cα-Cβ bond cleavage reactivity. Alkali lignin could also be degraded into aromatic monomers in [BMim][NTf2] using the protocol. Given the necessity of biomass upgradation, this work may provide a green and unique technology to boost the inert C-C bond cleavage upon photo-thermal synergism under metal-free and mild conditions that may underpin future advances in photo-thermal transformation and renewable energy production.
- Kang, Ying,Li, Minjie,Lu, Xingmei,Xin, Jiayu,Xu, Junli,Yang, Yongqing,Yao, Xiaoqian,Zhang, Suojiang,Zhou, Qing
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supporting information
p. 5524 - 5534
(2021/08/16)
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- Reaction pathways and deactivation mechanisms of isostructural Cr and Fe MIL-101 during liquid-phase styrene oxidation by hydrogen peroxide
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Isostructural Cr and Fe nanoporous MIL-101, synthesized without mineralizing agents, are investigated for styrene oxidation utilizing aqueous hydrogen peroxide to yield valuable oxygenates for chemical synthesis applications. Styrene conversion rates and oxygenate product distributions both depend on metal identity, as MIL-101(Fe) is more reactive for total styrene oxidation and is more pathway selective, preferring aldehyde (benzaldehyde) formation at the α-carbon to the aromatic ring, where MIL-101(Cr) sustains epoxide (styrene oxide) production at the same α-carbon. These pathways often involve hydrogen peroxide derived radical intermediates (O, -HOO, -HO-) and metallocycle transition states. We postulate that the higher reactivity of one of these surface intermediates, Fe(iv)O relative to Cr(iv)O, leads to higher styrene oxidation rates for MIL-101(Fe), while higher electrophilicity of Cr(iii)-OOH intermediates translates to the higher styrene oxide selectivity observed for MIL-101(Cr). Secondary styrene oxide and benzaldehyde conversions are observed over both analogs, but the former is more prevalent over MIL-101(Fe) due to higher Lewis/Br?nsted acid site density and strength compared to MIL-101(Cr). Recyclability experiments combined with characterization via XRD, SEM/EDXS, and FT-IR and UV-vis spectroscopies show that the nature of MIL-101(Fe) sites does not change significantly with each cycle, whereas MIL-101(Cr) suffers from metal leaching, which impacts styrene conversion rates and product distribution. Both catalysts require active site regeneration, though MIL-101(Fe) sites are more susceptible to reactivation, even under mild conditions. Finally, examination of styrene conversion for three unique synthesized phases of MIL-101(Cr) rationalizes that nodal defects are largely responsible for observed reactivity and selectivity but predispose the framework to metal leaching as a predominant deactivation mechanism.
- Sarazen, Michele L.,Yang, Rachel A.
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p. 5282 - 5296
(2021/08/16)
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- Evaluation of the protolytic equilibria and catalytic activity of sugar-based Schiff base ligands with VO2+ and MoO22+ cations in sulfoxidation and epoxidation reactions
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Based on the two anomeric methyl 3-amino-2,3-dideoxy-D-arabino-hexopyranosides ten new sugar-modified Schiff base ligands have been synthesized after monocondensation reaction with five o-hydroxyaromatic aldehydes, i.e. salicylaldehyde and its five para-s
- Chylewska, Agnieszka,D?browska, Aleksandra,Karman, Marta,Madejska, Katarzyna,Romanowski, Grzegorz
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- Photocatalytic one-pot multidirectional N-alkylation over Pt/D-TiO2/Ti3C2: Ti3C2-based short-range directional charge transmission
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Visible-light-induced one-pot, multistep, and chemoselectivity adjustable reactions highlight the economical, sustainable, and green process. Herein, we report Pt nanoparticles dispersed on S and N co-doped titanium dioxide/titanium carbide (MXene) (3%Pt/
- Jiang, Heyan,Sheng, Meilin,Li, Yue,Kong, Shuzhen,Bian, Fengxia
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- Two C=C Bond Participation in Annulation to Pyridines Based on DMF as the Nonadjacent N and C Atom Donors
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Two C=C bond participation in annulation to pyridines using N,N-dimethylformamide (DMF) as the N1 and C4 synthons has been carried out. In this reaction, DMF contributed one N atom and one C atom to two disconnected positions of pyridine ring, with no need for an additional nitrogen source. Two C=C bonds in two molecules of substituted styrenes offered four carbon atoms in the presence of iodine and persulfate. With the optimized conditions in hand, both symmetric and unsymmetric diaryl-substituted pyridines were obtained in useful yields. On the basis of relevant literature and a series of control experimental results, a possible mechanism was proposed in this work, which may demonstrate how DMF provides both N1 and C4 sources.
- Su, Miao-Dong,Liu, Hai-Ping,Cao, Zhong-Zhong,Liu, Yufeng,Li, Hui,Nie, Zhi-Wen,Yang, Tong-Lin,Luo, Wei-Ping,Liu, Qiang,Guo, Can-Cheng
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p. 13446 - 13453
(2021/10/12)
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- Catalytic alcohol oxidation using cationic Schiff base manganeseIII complexes with flexible diamino bridge
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Four Schiff base manganese(III) complexes with derivatives of [(R,R)-N,N’-bis(salicy1idene)-1,2-cyclohexanediaminato)] including substituents on salicylaldehyde such as 3-methoxy, 3,5-di-tert-butyl and 3,5-chloro were synthesized and characterized using a combination of IR, UV–Vis, and HR ESI-MS techniques. The catalytic activity of these complexes was tested in the oxidation of 1-phenylethanol to acetophenone, revealing very good performances for all of the four manganese complexes. The catalytic reactions were carried out in the presence of tert-butyl hydroperoxide (TBHP) as oxidant and imidazole as co-catalyst. Complex Mn-4, bearing electron withdrawing [(R,R)-N,N’-bis(3,5-di-chloro-salicylidene)-1,2-cyclohexanediaminato)] ligand was found to be the most stable of the tested Mn(III) complexes and was selected for the oxidation of several primary and secondary alcohols.
- Kakavand, Meysam,Mastrorilli, Piero,Mesto, Ernesto,Neshat, Abdollah,Osanlou, Farzane,Schingaro, Emanuela,Todisco, Stefano
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- Liquid-phase oxidation of olefins with rare hydronium ion salt of dinuclear dioxido-vanadium(V) complexes and comparative catalytic studies with analogous copper complexes
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Homogeneous liquid-phase oxidation of a number of aromatic and aliphatic olefins was examined using dinuclear anionic vanadium dioxido complexes [(VO2)2(salLH)]? (1) and [(VO2)2(NsalLH)]? (2) and dinuclear copper complexes [(CuCl)2(salLH)]? (3) and [(CuCl)2(NsalLH)]? (4) (reaction of carbohydrazide with salicylaldehyde and 4-diethylamino salicylaldehyde afforded Schiff-base ligands [salLH4] and [NsalLH4], respectively). Anionic vanadium and copper complexes 1, 2, 3, and 4 were isolated in the form of their hydronium ion salt, which is rare. The molecular structure of the hydronium ion salt of anionic dinuclear vanadium dioxido complex [(VO2)2(salLH)]? (1) was established through single-crystal X-ray analysis. The chemical and structural properties were studied using Fourier transform infrared (FT-IR), ultraviolet–visible (UV–Vis), 1H and 13C nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), electron paramagnetic resonance (EPR) spectroscopy, and thermogravimetric analysis (TGA). In the presence of hydrogen peroxide, both dinuclear vanadium dioxido complexes were applied for the oxidation of a series of aromatic and aliphatic alkenes. High catalytic activity and efficiency were achieved using catalysts 1 and 2 in the oxidation of olefins. Alkenes with electron-donating groups make the oxidation processes easy. Thus, in general, aromatic olefins show better substrate conversion in comparison to the aliphatic olefins. Under optimized reaction conditions, both copper catalysts 3 and 4 fail to compete with the activity shown by their vanadium counterparts. Irrespective of olefins, metal (vanadium or copper) complexes of the ligand [salLH4] (I) show better substrate conversion(%) compared with the metal complexes of the ligand [NsalLH4] (II).
- Maurya, Abhishek,Haldar, Chanchal
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- Biochemical and Metabolic Insights into Hyoscyamine Dehydrogenase
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Hyoscyamine, a member of the class of compounds known as tropane alkaloids (TAs), is clinically used as an anticholinergic drug. Previous research has predicted that hyoscyamine is produced via the reduction of hyoscyamine aldehyde. In this study, we identified a root-expressed gene from Atropa belladonna, named AbHDH, which encodes a hyoscyamine dehydrogenase involved in the formation of hyoscyamine. Enzymatic assays indicated that AbHDH was able to not only reduce hyoscyamine aldehyde to produce hyoscyamine but also oxidize hyoscyamine to form hyoscyamine aldehyde under different conditions. To elucidate its catalytic mechanism, the crystal structure of AbHDH at a 2.4-? resolution was also determined. Overexpression of AbHDH significantly enhanced the biosynthesis of hyoscyamine and the production of anisodamine and scopolamine in root cultures of A. belladonna. However, suppression of AbHDH using RNAi technology did not reduce the production of hyoscyamine, anisodamine, or scopolamine, though it did increase the accumulation of hyoscyamine aldehyde. In summary, this study provided timely biochemical and metabolic insights into hyoscyamine dehydrogenase, pointing to an alternative, promising way to produce pharmaceutical TAs via metabolic engineering in planta.
- Qiu, Fei,Yan, Yijun,Zeng, Junlan,Huang, Jian-Ping,Zeng, Lingjiang,Zhong, Wei,Lan, Xiaozhong,Chen, Min,Huang, Sheng-Xiong,Liao, Zhihua
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p. 2912 - 2924
(2021/03/15)
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- Selective palladium nanoparticles-catalyzed hydrogenolysis of industrially targeted epoxides in water
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Palladium nanoparticles, with core sizes of ca. 2.5 nm, were easily synthesized by chemical reduction of Na2PdCl4 in the presence of hydroxyethylammonium salts and proved to be efficient for the selective hydrogenolysis of various aromatic, alkylphenyl, aliphatic epoxides in water as green solvent. Capping agents of the metal species were screened to define the most suitable micellar nanoreactors on two target substrates of industrial interest, epoxystyrene and 7,8-epoxy-2-methoxy-2,6-dimethyloctane. In our conditions, the hydrogenolysis of epoxystyrene proved to be pH-dependent, producing either the diol under acidic conditions, or the sweet-smelling 2-phenylethanol in the presence of a base. Promisingly, 7,8-epoxy-2-methoxy-2,6-dimethyloctane was completely and selectively hydrogenated into Florsantol, a sandalwood odorant at a multigram scale (40 g and up to 175g). A general mechanism for the palladium nanoparticles-catalyzed hydrogenolysis of terminal epoxides was proposed according to steric and electronic properties and finely corroborated with deuterium labelling experiments.
- Duval, Marion,Deboos, Victor,Hallonet, Agnès,Sagorin, Gilles,Denicourt-Nowicki, Audrey,Roucoux, Alain
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p. 261 - 268
(2021/03/22)
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- B(C6F5)3-catalyzed tandem protonation/deuteration and reduction of: In situ -formed enamines
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A highly efficient B(C6F5)3-catalyzed tandem protonation/deuteration and reduction of in situ-formed enamines in the presence of water and pinacolborane was developed. Regioselective β-deuteration of tertiary amines was achieved with high chemo- and regioselectivity. D2O was used as a readily available and cheap source of deuterium. Mechanistic studies indicated that B(C6F5)3 could activate water to promote the protonation and reduction of enamines. This journal is
- Wu, Rongpei,Gao, Ke
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supporting information
p. 4032 - 4036
(2021/05/19)
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- Aryl C-F bond functionalization preparation method
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The invention relates to the technical field of organic compound synthesis, in particular to an aryl C-F bond functionalization preparation method. A fluorobenzene compound and a nucleophilic reagent react under the action of a composite catalyst, wherein the composite catalyst is formed by mixing a visible light catalyst and a metal catalyst. The photocatalyst is adopted, the reaction process is safe and controllable, and operation in the preparation and production process is simplified; a purple LED is used as a reaction energy source and is green and environment-friendly, the energy utilization rate is high, and conversion from light energy to chemical energy can be efficiently realized; in the reaction, a simple nucleophilic reagent is used for attacking free radical cation species generated under a visible light catalysis condition, so that a target product with an extremely wide range is efficiently and greenly prepared; the operation steps are simplified, and the reaction route is shortened; and moreover, the forward reaction rate is high, and the production efficiency is remarkably improved.
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Paragraph 0048-0053
(2021/09/29)
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- H4SiW12O40-catalyzed cyclization of epoxides/aldehydes and sulfonyl hydrazides: An efficient synthesis of 3,4-disubstituted 1H-pyrazoles
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A simple and efficient method for the synthesis of pyrazoles through a silicotungstic acid (H4SiW12O40)-catalyzed cyclization of epoxides/aldehydes and sulfonyl hydrazides has been developed. Various epoxides/aldehydes were smoothly reacted with sulfonyl hydrazides to furnish regioselectivity 3,4-disubstituted 1H-pyrazoles. The application of such an earth-abundant, readily accessible, and nontoxic catalyst provides a green approach for the construction of 3,4-disubstituted 1H-pyrazoles. A plausible reaction mechanism has been proposed on the basis of control experiments, GC-MS and DFT calculations.
- Cheng, Mengyuan,Cheng, Yuanyuan,Gao, Xiaofei,Li, Ke,Lin, Xiaoling,Liu, Yufeng,Xie, Xuanjie,Yang, Guoping
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supporting information
(2021/09/06)
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- One-pot, oxidative and selective conversion of benzylic silyl and tetrahydropyranyl ethers to gem-dichlorides using trichloroisocyanuric acid and triphenylphosphine as an efficient and neutral system
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A one-pot and oxidative method is described for the first time for the conversion of benzylic trimethylsilyl (TMS) and tetrahydropyranyl (THP) ethers to gem-dichlorides using trichloroisocyanuric acid (TCCA) and triphenylphosphine (PPh3) in neutral media. Various theses substrates containing electron withdrawing or donating groups can be efficiently converted to their corresponding gem-dichlorides in good to excellent yields. The present method shows a high degree of chemoselectivity, and due to its one-pot nature is in accordance with green chemistry.
- Khadem Moghaddam, Roqayeh,Aghapour, Ghasem
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p. 398 - 406
(2020/11/19)
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- Electronic Asymmetry of an Annelated Pyridyl-Mesoionic Carbene Scaffold: Application in Pd(II)-Catalyzed Wacker-Type Oxidation of Olefins
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The two donor modules of an annelated pyridyl-mesoionic carbene ligand (aPmic) have different σ- and π-bonding characteristics leading to its electronic asymmetry. A Pd(II) complex 1 featuring aPmic catalyzes the oxidation of a wide range of terminal olefins to the corresponding methyl ketones in good to excellent yields in acetonitrile. The catalytic reaction is proposed to proceed via syn-peroxypalladation and a subsequent rate-limiting 1,2-hydride shift, which is supported by kinetic studies. The electronic asymmetry of aPmic renders a well-defined coordination sphere at Pd. The favored arrangement of reactants on the metal center features an olefin trans to the pyridyl module and a tbutylperoxide trans to the carbene. This arrangement gains added stability by the π-delocalization paved by the compatible orbitals on Pd, the pyridyl module, and the olefin that is perpendicular to the Pd(aPmic) plane. The π-interactions are absent in an alternate arrangement wherein the olefin is trans to the carbene. Density functional theory studies reveal the matching orbital overlaps responsible for the preferred arrangement over the other. This work provides an orbital description for the electronic asymmetry of aPmic.
- Bera, Jitendra K.,Dutta, Indranil,Kunnikuruvan, Sooraj,Reshi, Noor U Din,Saha, Sayantani,Yadav, Suman
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p. 11385 - 11393
(2020/11/23)
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- Efficient Synthesis of Phenylacetate and 2-Phenylethanol by Modular Cascade Biocatalysis
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The green and sustainable synthesis of chemicals from renewable feedstocks by a biotransformation approach has gained increasing attention in recent years. In this work, we developed enzymatic cascades to efficiently convert l-phenylalanine into 2-phenylethanol (2-PE) and phenylacetic acid (PAA), l-tyrosine into tyrosol (p-hydroxyphenylethanol, p-HPE) and p-hydroxyphenylacetic acid (p-HPAA). The enzymatic cascade was cast into an aromatic aldehyde formation module, followed by an aldehyde reduction module, or aldehyde oxidation module, to achieve one-pot biotransformation by using recombinant Escherichia coli. Biotransformation of 50 mM l-Phe produced 6.76 g/L PAA with more than 99 % conversion and 5.95 g/L of 2-PE with 97 % conversion. The bioconversion efficiencies of p-HPAA and p-HPE from l-Tyr reached to 88 and 94 %, respectively. In addition, m-fluoro-phenylalanine was further employed as an unnatural aromatic amino acid substrate to obtain m-fluoro-phenylacetic acid; '96 % conversion was achieved. Our results thus demonstrated high-yielding and potential industrial synthesis of above aromatic compounds by one-pot cascade biocatalysis.
- Mao, Zuoxi,Liu, Lijun,Zhang, Yang,Yuan, Jifeng
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p. 2676 - 2679
(2020/06/03)
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- Impact of Phenolic Compounds in Strecker Aldehyde Formation in Wine Model Systems: Target and Untargeted Analysis
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The Strecker degradation of phenylalanine has been studied in a phenolic compound/phenylalanine wine model system. Six phenolic compounds (3,4-dihydroxybenzoic acid, gallic acid, caffeic acid, ferulic acid, catechin, and epicatechin) were compared in the formation of phenylacetaldehyde when in the presence of glucose or methylglyoxal (MG). The addition of glucose reduced the formation of Strecker aldehyde, independently of the phenolic compound. The addition of MG, on the other hand, increased phenylacetaldehyde formation for hydroxybenzoic acids and decreased phenylacetaldehyde formation for flavan-3-ols, confirming their capacity to trap the dicarbonyl compound. As a target phenolic compound, catechin was chosen to perform kinetic studies to further understand the reaction intermediates involved in the mechanism of phenylacetaldehyde formation, in particular, catechin o-quinone and catechin-MG adduct. The addition of glucose and MG increased the consumption of catechin, while a reduction in the respective o-quinone was observed, suggesting that these substrates have an impact in other reactions involving catechin. In that regard, for the first time, it was demonstrated that the catechin-MG adduct was capable of oxidizing and forming a new o-quinone, contributing to wine instability promoted by oxidation reactions.
- Martins, S. I. F. S.,Monforte, A. R.,Silva Ferreira, A. C.
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p. 10281 - 10286
(2020/10/26)
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- In situ replacement of Cu-DEN: An approach for preparing a more noble metal nanocatalyst for catalytic use
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The advantage of dendritic monodisperse macromolecules' dual templating ability was useful in the formation of silica-supported copper nanoparticles Cun@SiO2NPs. This was acquired by the initial synthesis of a silica framework (G4-PAMAM-NH2-SiO2) as a mes
- Onisuru, Oluwatayo Racheal,Oseghale, Charles O.,Meijboom, Reinout
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p. 20322 - 20333
(2020/12/21)
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- Syntheses, characterization and properties of two new dodeca-niobates presenting unprecedented features
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Two new dodeca-niobate materials, K3[Nb2O2][H7SiNb12O40]·16H2O (1) and [Cu(en)2]9[(VNb12V1.69Nb0.31O42en0.3
- Cui, Xiao-Bing,Lin, Po-Han,Yu, Gui-Yang,Zhang, Ting-Ting,Zhang, Xiao
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p. 6495 - 6503
(2020/06/03)
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- Epoxidation of Alkenes with Molecular Oxygen as the Oxidant in the Presence of Nano-Al 2O 3
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The nano-Al 2O 3-promoted epoxidation of alkenes with molecular oxygen as the oxidant has been developed, providing an efficient route to a variety of epoxides in moderate to excellent yields. The environmentally friendly and efficient nano-Al 2O 3catalyst could be easily recovered and reused five times without significant loss of activity.
- Zhou, Xuan,Wang, Qiong,Xiong, Wenfang,Wang, Lu,Ye, Rongkai,Xiang, Ge,Qi, Chaorong,Hu, Jianqiang
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supporting information
p. 1789 - 1794
(2020/09/18)
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- Cu(ii)Cl2containing bispyridine-based porous organic polymer support preparedviaalkyne-azide cycloaddition as a heterogeneous catalyst for oxidation of various olefins
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A new type of porous organic polymer (POP) based heterogeneous catalystCu-POPwas prepared by immobilizing Cu(ii)Cl2into bpy containing POP preparedviaalkyne-azide cycloaddition. This new catalyst showed efficient catalytic activities and outstanding reusability. Remarkably, one batch ofCu-POPwas continuously used for all olefins without losing its activity by simply washing.
- Choi, Hye Min,Lee, Suk Joong,Yoon, Jongho
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supporting information
p. 9149 - 9152
(2020/06/17)
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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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- Magnetically recoverable porphyrin-based nanocatalysts for the effective oxidation of olefins with hydrogen peroxide: A comparative study
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In this paper, preparation, characterization and catalytic applications of metalloporphyrin-based magnetic nanocatalysts were investigated. meso-Tetrakis(4-carboxyphenyl)porphyrinatoiron(iii) chloride (Fe(TCPP)Cl) and meso-tetrakis(4-carboxyphenyl)porphyrinatomanganese(iii) acetate (Mn(TCPP)OAc) were separately immobilized onto the surface of amine functionalized magnetic nanoparticles (Fe3O4/SiO2/NH2) via covalent attachment. The obtained nanocatalysts were characterized using FT-IR and UV-Vis and atomic absorption spectroscopy, X-ray powder diffraction (XRD), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The catalytic efficiency of Fe3O4/SiO2/NH2-Fe(TCPP)Cl and Fe3O4/SiO2/NH2-Mn(TCPP)OAc for the green oxidation of alkenes with H2O2 was investigated in a comparative manner. The Mn-porphyrin based magnetic nanocatalyst shows higher catalytic efficiency compared to the Fe-porphyrin. In addition, the prepared magnetic nanocatalyst exhibited excellent reusability and could be reused at least five times without significant leaching or loss of activity. This journal is
- Rayati, Saeed,Moradi, Dana,Nejabat, Fatemeh
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p. 19385 - 19392
(2020/11/23)
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- Solvent-free, microwave assisted oxidation of alcohols with 4-hydroxypyridinium chlorochromate functionalized silica gel
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4-Hydroxypyridinium chlorochromate functionalized silica gel was found to be an efficient and reusable oxidant for the very fast oxidation of primary and secondary alcohols to the corresponding carbonyl compounds under solventfree conditions and microwave irradiation in excellent yields.
- AHMADI, Sayed Ali,GHALEHBANDI, Shermineh Sadat,GHAZANFARI, Dadkhoda,SHEIKHHOSSEINI, Enayatollah
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p. 283 - 289
(2020/10/06)
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- Heterogeneous photocatalytic anaerobic oxidation of alcohols to ketones by Pt-mediated hole oxidation
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We report a platinum nanocluster/graphitic carbon nitride (Pt/g-C3N4) composite solid catalyst with a photocatalytic anaerobic oxidation function for highly active and selective transformation of alcohols to ketones. The desirable products were successfully obtained in good to excellent yields from various functionalized alcohols at room temperature, including unactivated alcohols. Mechanistic studies indicated that the reaction could proceed through a Pt-mediated hole oxidation initiating an α-alcohol radical intermediate followed by a two-electron oxidation pathway. The merit of this strategy offers a general approach towards green and sustainable organic synthetic chemistry.
- Sun, Danhui,Li, Peihe,Wang, Xia,Wang, Yingying,Wang, Jinghui,Wang, Yin,Lu, Ye,Duan, Limei,Sarina, Sarina,Zhu, Huaiyong,Liu, Jinghai
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supporting information
p. 11847 - 11850
(2020/10/13)
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