- A synergistic effect in the combination of H2O2, FeAPO-5 and NaBr for selective oxidation of benzyl alcohols
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The H2O2/FeAPO-5/NaBr combination has been found to be active in the oxidation of benzyl alcohols. The remarkably different activity results obtained with the H2O2/FeAPO-5/NaBr, the H 2O2/FeAPO-5 and the H2O2/NaBr confirm the existence of a strongly synergistic effect in the ternary reaction system of H2O2, FeAPO-5 and NaBr, leading to a significantly enhanced conversion of benzyl alcohols under mild reaction conditions.
- Qi, Lin,Qi, Xingyi,Wang, Jing,Zheng, Liwei
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- Aromatic stacking interactions govern catalysis in aryl-alcohol oxidase
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Aryl-alcohol oxidase (AAO, EC 1.1.3.7) generates H2O2 for lignin degradation at the expense of benzylic and other π system-containing primary alcohols, which are oxidized to the corresponding aldehydes. Ligand diffusion studies on Pleurotus eryngii AAO showed a T-shaped stacking interaction between the Tyr92 side chain and the alcohol substrate at the catalytically competent position for concerted hydride and proton transfers. Bi-substrate kinetics analysis revealed that reactions with 3-chloro- or 3-fluorobenzyl alcohols (halogen substituents) proceed via a ping-pong mechanism. However, mono- and dimethoxylated substituents (in 4-methoxybenzyl and 3,4-dimethoxybenzyl alcohols) altered the mechanism and a ternary complex was formed. Electron-withdrawing substituents resulted in lower quantum mechanics stacking energies between aldehyde and the tyrosine side chain, contributing to product release, in agreement with the ping-pong mechanism observed in 3-chloro- and 3-fluorobenzyl alcohol kinetics analysis. In contrast, the higher stacking energies when electron donor substituents are present result in reaction of O2 with the flavin through a ternary complex, in agreement with the kinetics of methoxylated alcohols. The contribution of Tyr92 to the AAO reaction mechanism was investigated by calculation of stacking interaction energies and site-directed mutagenesis. Replacement of Tyr92 by phenylalanine does not alter the AAO kinetic constants (on 4-methoxybenzyl alcohol), most probably because the stacking interaction is still possible. However, introduction of a tryptophan residue at this position strongly reduced the affinity for the substrate (i.e. the pre-steady state Kd and steady-state Km increase by 150-fold and 75-fold, respectively), and therefore the steady-state catalytic efficiency, suggesting that proper stacking is impossible with this bulky residue. The above results confirm the role of Tyr92 in substrate binding, thus governing the kinetic mechanism in AAO.
- Ferreira, Patricia,Hernández-Ortega, Aitor,Lucas, Fátima,Carro, Juan,Herguedas, Beatriz,Borrelli, Kenneth W.,Guallar, Victor,Martínez, Angel T.,Medina, Milagros
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- Natural heterogeneous catalysis with immobilised oxidase biocatalysts
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The generation of immobilised oxidase biocatalysts allowing multifunctional oxidation of valuable chemicals using molecular oxygen is described. Engineered galactose oxidase (GOase) variants M1and M3-5, an engineered choline oxidase (AcCO6) and monoamine oxidase (MAO-N D9) displayed long-term stability and reusability over several weeks when covalently attached on a solid support, outperforming their free counterparts in terms of stability (more than 20 fold), resistance to heat at 60 °C, and tolerance to neat organic solvents such as hexane and toluene. These robust heterogenous oxidation catalysts can be recovered after each reaction and be reused multiple times for the oxidation of different substrates.
- Angelastro, Antonio,Baldwin, Christopher,Birmingham, William R.,Cosgrove, Sebastian C.,Flitsch, Sabine L.,Heath, Rachel S.,Mattey, Ashley P.,Ramsden, Jeremy I.,Sangster, Jack J.,Turner, Nicholas J.
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- Lead-free perovskite Cs3Bi2Br9 heterojunctions for highly efficient and selective photocatalysis under mild conditions
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Lead halide perovskites possess excellent photoelectric properties and are promising for photocatalysis. However, the toxicity of lead in these perovskites has hindered their application. We designed a stable, lead-free heterojunction to enhance the photocatalytic efficiency of the perovskite. A production rate of 1465 μmol/g/h for the selective oxidation of benzyl alcohol was achieved, which was the highest among all inorganic catalysts without zero-valent metal cocatalyst in the atmosphere at room temperature. In addition, the heterojunction degraded 74.7% of 10 ppm 2-mercaptobenzothiazole within 10 min, and achieving a final degradation rate exceeding 99.9% in 20 min, which is the best degradation efficiency among all reported studies. Detailed optical characterisation proved that the high efficiency stems from band matching and charge transfer between Cs3Bi2Br9 and TiO2. This result will inspire the design of additional lead-free perovskites for photocatalysis.
- He, Jing-Hui,Li, Lanxin,Lu, Jian-Mei,Sun, Qimeng,Wang, Jia,Wei, Jialiang,Ye, Wen
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- An aerobic oxidation of alcohols into carbonyl synthons using bipyridyl-cinchona based palladium catalyst
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We have reported an aerobic oxidation of primary and secondary alcohols to respective aldehydes and ketones using a bipyridyl-cinchona alkaloid based palladium catalytic system (PdAc-5) using oxygen at moderate pressure. ThePdAc-5catalyst was analysed using SEM, EDAX, and XPS analysis. The above catalytic system is used in experiments for different oxidation systems which include different solvents, additives, and bases which are cheap, robust, non-toxic, and commercially available on the industrial bench. The obtained products are quite appreciable in both yield and selectivity (70-85%). In addition, numerous important studies, such as comparisons with various commercial catalysts, solvent systems, mixture of solvents, and catalyst mole%, were conducted usingPdAc-5. The synthetic strategy of oxidation of alcohol into carbonyl compounds was well established and all the products were analysed using1H NMR,13CNMR and GC-mass analyses.
- Cheedarala, Ravi Kumar,Chidambaram, Ramasamy R.,Siva, Ayyanar,Song, Jung Il
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p. 32942 - 32954
(2021/12/02)
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- Combining photo-redox and enzyme catalysis for the synthesis of 4H-pyrimido[2,1-b] benzothiazole derivatives in one pot
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A novel strategy combining visible-light and enzyme catalysis in one pot for the synthesis of 4H-pyrimido[2,1-b] benzothiazole derivatives from alcohols is described for the first time. Fourteen 4H-pyrimido[2,1-b] benzothiazole derivatives were prepared with yields of up to 98% under mild reaction conditions by a simple operation. The photoorgano catalyst rose Bengal (rB) was employed to oxyfunctionalise alcohols to aldehydes. Compared with aldehydes, alcohols with more stable properties and lower cost, thus we used photocatalysis to oxidize alcohols into aldehydes. Next, the enzyme was used to further catalyze the reaction of Biginelli to produce the target product of 4H-pyrimidine [2,1-b] benzothiazole. Experimental results show that this method provides a more efficient and eco-friendly strategy for the synthesis of 4H-pyrimido[2,1-b] benzothiazole derivatives.
- Yu, Yuan,Lu, Wei-Fan,Yang, Zeng-Jie,Wang, Na,Yu, Xiao-Qi
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supporting information
(2020/12/25)
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- MOFs assembled from C 3symmetric ligands: Structure, iodine capture and role as bifunctional catalysts towards the oxidation-Knoevenagel cascade reaction
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Three new NiII/CoII-metal organic frameworks were self-assembled by the reaction of C3 symmetric 1,3,5-tribenzoic acid (H3BTC) and 2,4,6-tris(4-pyridyl)-1,3,5-triazine (4-TPT) ligands and NiII/CoII salts under solvothermal conditions. Isomorphous MOF1 and MOF2 exhibit a 3D pillar-layer framework based on binuclear M2(OH)(COO)2 units connected by tritopic BTC3- and 4-TPT ligands with a novel (3,5)-connected topology net. MOF3 displays a 3-fold interpenetrated 3D network exhibiting a (3,4)-connected topology net. The porous MOF3 can reversibly take up I2. The activated MOFs contain both Lewis acid (NiII center) and basic (uncoordinated pyridyl or carboxylic groups) sites, and act as bifunctional acid-base catalysts. The catalytic measurements demonstrate that the activated MOF3 exhibits good activities for benzyl alcohol oxidation and the Knoevenagel reaction and can be recycled and reused for at least four cycles without losing its structural integrity and high catalytic activity. Thus, the catalytic properties for the oxidation-Knoevenagel cascade reaction have also been studied.
- Zhang, Ying-Ying,Liu, Qing,Zhang, Lin-Yan,Bao, Yu-Mei,Tan, Jing-Yi,Zhang, Na,Zhang, Jian-Yong,Liu, Zhen-Jiang
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supporting information
p. 647 - 659
(2021/01/28)
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- Radical Decarboxylative Carbometalation of Benzoic Acids: A Solution to Aromatic Decarboxylative Fluorination
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Abundant aromatic carboxylic acids exist in great structural diversity from nature and synthesis. To date, the synthetically valuable decarboxylative functionalization of benzoic acids is realized mainly by transition-metal-catalyzed decarboxylative cross couplings. However, the high activation barrier for thermal decarboxylative carbometalation that often requires 140 °C reaction temperature limits both the substrate scope as well as the scope of suitable reactions that can sustain such conditions. Numerous reactions, for example, decarboxylative fluorination that is well developed for aliphatic carboxylic acids, are out of reach for the aromatic counterparts with current reaction chemistry. Here, we report a conceptually different approach through a low-barrier photoinduced ligand to metal charge transfer (LMCT)-enabled radical decarboxylative carbometalation strategy, which generates a putative high-valent arylcopper(III) complex, from which versatile facile reductive eliminations can occur. We demonstrate the suitability of our new approach to address previously unrealized general decarboxylative fluorination of benzoic acids.
- Xu, Peng,López-Rojas, Priscila,Ritter, Tobias
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supporting information
p. 5349 - 5354
(2021/05/05)
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- Selective oxidation of alkenes to carbonyls under mild conditions
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Herein, a practical and sustainable method for the synthesis of aldehydes, ketones, and carboxylic acids from an inexpensive olefinic feedstock is described. This transformation features very sustainable and mild conditions and utilizes commercially available and inexpensive tetrahydrofuran as the additive, molecular oxygen as the sole oxidant and water as the solvent. A wide range of substituted alkenes were found to be compatible, providing the corresponding carbonyl compounds in moderate-to-good yields. The control experiments demonstrated that a radical mechanism is responsible for the oxidation reaction.
- Huo, Jie,Xiong, Daokai,Xu, Jun,Yue, Xiaoguang,Zhang, Pengfei,Zhang, Yilan
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supporting information
p. 5549 - 5555
(2021/08/16)
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- Aryl aldiketone and synthesis method thereof
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The invention discloses an aryl aldehyde ketone and a synthesis method thereof, wherein an aryl aldehyde is synthesized from cheap olefin as a raw material. A commercially available inexpensive olefin is used as a raw material, ether is used as an additive, molecular oxygen serves as a sole oxidizing agent, water is used as a solvent, and the aldehyde and ketone are synthesized by column chromatography under a photocatalytic condition. The invention has the advantages of mild reaction conditions, green and environmental protection, simple experimental operation, good reaction selectivity, high product yield and the like.
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Paragraph 0017
(2021/09/26)
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- Visible-Light-Driven Oxidative Cleavage of Alkenes Using Water-Soluble CdSe Quantum Dots
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The oxidative cleavage of C=C bonds is an important chemical reaction, which is a popular reaction in the photocatalytic field. However, high catalyst-loading and low turnover number (TON) are general shortcomings in reported visible-light-driven reactions. Herein, the direct oxidative cleavage of C=C bonds through water-soluble CdSe quantum dots (QDs) is described under visible-light irradiation at room temperature with high TON (up to 3.7×104). Under the same conditions, water-soluble CdSe QDs could also oxidize sulfides to sulfoxides with 51–84 % yields and TONs up to 3.4×104. The key features of this photocatalytic protocol include high TONs, wide substrates scope, low catalyst loadings, simple and mild reaction conditions, and molecular O2 as the oxidant.
- Li, Jianing,Zhao, Jingnan,Ma, Cunfei,Yu, Zongyi,Zhu, Hongfei,Yun, Lei,Meng, Qingwei
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p. 4985 - 4992
(2021/10/16)
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- Nitrosoarene-Catalyzed HFIP-Assisted Transformation of Arylmethyl Halides to Aromatic Carbonyls under Aerobic Conditions
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A rare metal-free nucleophilic nitrosoarene catalysis accompanied by highly hydrogen-bond-donor (HBD) solvent, 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP), organocatalytically converts arylmethyl halides to aromatic carbonyls. This protocol offers an effective means to access a diverse array of aromatic carbonyls with good chemoselectivity under mild reaction conditions. The activation of arylmethyl halides by HFIP to generate stable carbocation and autoxidation of in situ generated hydroxylamine to nitrosoarene in the presence of atmospheric O2 are the keys to success.
- Pradhan, Suman,Sharma, Vishali,Chatterjee, Indranil
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supporting information
p. 6148 - 6152
(2021/08/03)
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- Chemoselective Cross-Coupling between Two Different and Unactivated C(aryl)-O Bonds Enabled by Chromium Catalysis
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We report here the first example of cross-coupling between two different and unactivated C(aryl)-O bonds with chromium catalysis. The combination of a low-cost Cr(II) salt, 4,4′-di-tert-butyl-2,2′-dipyridyl (dtbpy) as the ligand, and magnesium as the reductant shows high reactivity in promoting the reductive cross-coupling of aryl methyl ether derivatives with aryl esters by cleavage and coupling of two different C(aryl)-O bonds under mild conditions. The formation of active low-valent Cr species by reduction of CrCl2 with Mg can be considered, which prefers to initially activate the C(aryl)-O bond of phenyl methyl ether with the chelation help of dtbpy and an o-imine auxiliary. The subsequent consecutive reduction, second C(aryl)-O activation, and reductive elimination allow for the achievement of selective cross-coupling of C(aryl)-O/C(aryl)-O bonds.
- Tang, Jinghua,Liu, Liu Leo,Yang, Shangru,Cong, Xuefeng,Luo, Meiming,Zeng, Xiaoming
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supporting information
p. 7715 - 7720
(2020/05/20)
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- Cerium(IV) Carboxylate Photocatalyst for Catalytic Radical Formation from Carboxylic Acids: Decarboxylative Oxygenation of Aliphatic Carboxylic Acids and Lactonization of Aromatic Carboxylic Acids
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We found that in situ generated cerium(IV) carboxylate generated by mixing the precursor Ce(OtBu)4 with the corresponding carboxylic acids served as efficient photocatalysts for the direct formation of carboxyl radicals from carboxylic acids under blue light-emitting diodes (blue LEDs) irradiation and air, resulting in catalytic decarboxylative oxygenation of aliphatic carboxylic acids to give C-O bond-forming products such as aldehydes and ketones. Control experiments revealed that hexanuclear Ce(IV) carboxylate clusters initially formed in the reaction mixture and the ligand-to-metal charge transfer nature of the Ce(IV) carboxylate clusters was responsible for the high catalytic performance to transform the carboxylate ligands to the carboxyl radical. In addition, the Ce(IV) carboxylate cluster catalyzed direct lactonization of 2-isopropylbenzoic acid to produce the corresponding peroxy lactone and ?3-lactone via intramolecular 1,5-hydrogen atom transfer (1,5-HAT).
- Hirosawa, Keishi,Mashima, Kazushi,Satoh, Tetsuya,Shinohara, Koichi,Shirase, Satoru,Tamaki, Sota,Tsurugi, Hayato
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supporting information
(2020/03/25)
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- A one-pot synthesis of benzimidazoles via aerobic oxidative condensation of benzyl alcohols with o-phenylenediamines catalyzed by [MIMPs]+Cl-/NaNO2/TEMPO
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The ionic liquid 1-methyl-3-(3-sulfopropyl)imidazolium chloride ([MIMPs]+Cl-) in combination with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and sodium nitrite (NaNO2) as a catalytic system demonstrates high efficiency in the one-pot two-step aerobic oxidative condensation of benzyl alcohols with 1,2-phenylenediamines to give benzimidazoles. Various benzimidazoles are obtained in good to excellent yields by this strategy.
- Geng, Zhenzhen,Zhang, Hong-Yu,Yin, Guohui,Zhang, Yuecheng,Zhao, Jiquan
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p. 557 - 565
(2020/03/30)
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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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- Heterogeneous carbon nitride photocatalyst for C-C bond oxidative cleavage of vicinal diols in aerobic micellar medium
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A green and efficient visible-light promoted aerobic oxidative C-C bond cleavage of vicinal diols in micellar medium has been developed. This protocol used graphitic carbon nitride with nitrogen vacancies (CN620) as a metal-free recyclable photocatalyst and CTAB as surfactant in water. Control experiments and the ESR results indicated that superoxide radicals and valence band holes played an important role in the reaction. Further isotope experiments suggested both a β-scission/HAT pathway and an oxidation/hydrolysis/dehydration pathway for the reaction, which is different from previous reports. The semiconductor/micellar catalyst system can be recycled at least 10 times without a significant reduction in activity. Furthermore, this reaction could be carried out under solar light irradiation and was applicable to large-scale reactions with similar results.
- Chen, Jiayang,Chen, Shengjun,Dong, Xinyu,Hong, Mei,Ni, Bangqing,Niu, Tengfei,Zhang, Tianhao
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supporting information
p. 5042 - 5049
(2020/08/25)
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- Oxidative C-S Bond Cleavage of Benzyl Thiols Enabled by Visible-Light-Mediated Silver(II) Complexes
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The oxidative cleavage reaction of the C-S bond using singlet oxygen is challenging because of its uncontrollable nature. We have developed a novel method for the singlet-oxygen-mediated selective C-S bond cleavage reaction using silver(II)-ligand complexes. Visible-light-induced silver catalysis enables the controlled oxidative cleavage of benzyl thiols to afford carbonyl compounds, such as aldehydes or ketones, which are important synthetic components.
- Hong, Boseok,Aganda, Kim Christopher C.,Lee, Anna
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supporting information
p. 4395 - 4399
(2020/06/05)
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- Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas
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The reductive carbonylation of aryl iodides to aryl aldehydes possesses broad application prospects. We present an efficient and facile Rh-based catalytic system composed of the commercially available Rh salt RhCl3·3H2O, PPh3 as phosphine ligand, and Et3N as the base, for the synthesis of arylaldehydes via the reductive carbonylation of aryl iodides with CO and H2 under relatively mild conditions with a broad substrate range affording the products in good to excellent yields. Systematic investigations were carried out to study the experimental parameters. We explored the optimal ratio of Rh salt and PPh3 ligand, substrate scope, carbonyl source and hydrogen source, and the reaction mechanism. Particularly, a scaled-up experiment indicated that the catalytic method could find valuable applications in industrial productions. The low gas pressure, cheap ligand and low metal dosage could significantly improve the practicability in both chemical researches and industrial applications.
- Chen, Suqing,Liu, Zhenghui,Mu, Tiancheng,Wang, Peng,Yan, Zhenzhong,Yu, Dongkun,Zhao, Xinhui
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p. 645 - 656
(2020/05/14)
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- Iodobenzene-catalyzed oxidative cleavage of olefins to carbonyl compounds
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A metal-free approach for the oxidative cleavage of carbon–carbon double bonds of olefins to carbonyl compounds was established by using oxidant m-CPBA and non-metallic organocatalyst PhI in toluene/H2O. A broad scope of aromatic olefins was used. All the reactions proceeded smoothly at 35 °C in short reaction time to furnish the respective mono- and double carbonyl compounds selectively in moderate to good yields.
- Du, Lele,Wang, Zechao,Wu, Junliang
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supporting information
(2020/07/20)
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- A Versatile Metalloporphyrinic Framework Platform for Highly Efficient Bioinspired, Photo- and Asymmetric Catalysis
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Even though numerous bioinspired catalysts have been developed, there remain huge gaps between the artificial and natural catalysts, because it is very difficult to imitate simultaneously the complicated constituents, structures, and synergistic effect of enzymes. We report herein a versatile metalloporphyrinic framework platform, which exhibits high efficiency in bioinspired catalysis, photocatalysis, and asymmetric catalysis. The catalytic properties are highly dependent on the tunable constituents and their cooperation, and are significantly superior to the corresponding molecular catalyst systems which lack the synergistic effects. Since there are numerous functional moieties that can readily be incorporated into the metalloporphyrinic framework platform, a myriad of applications can be simply realized by embedding different functional moieties.
- He, Wei-Long,Zhao, Min,Wu, Chuan-De
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supporting information
p. 168 - 172
(2018/12/05)
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- Oxygen-vacancies-engaged efficient carrier utilization for the photocatalytic coupling reaction
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Defects can greatly optimize the solar light harvesting capability and electronic structure of oxide materials. However, it remains challenging to achieve a defect engineering strategy under mild conditions. Meanwhile, the simultaneous exploitation of photogenerated holes (h+) and electrons (e?) to promote both photooxidation and photoreduction in a coupled system has rarely been reported. For the first time, we reveal an oxygen-vacancies-mediated photocatalytic strategy in which the electrons and holes are fully utilized for nitrobenzene reduction coupled with benzyl alcohol oxidation. The oxygen vacancies (OVs) generated in situ on the surface of TiO2 greatly extend light absorption into the visible region and promote the photogenerated electron transport for efficient photocatalysis. The experimental and theoretical results together indicate that chemisorption on the TiO2 surface decreases the oxidation potential of benzyl alcohol and causes an upward shift in its HOMO, which facilitates the oxidation reaction of benzyl alcohol to benzaldehyde. The in situ generated surface OVs also act as a bridge to enable the trapping and transferring of the photoinduced electrons to the nitrobenzene. This work provides a new perspective of utilizing the chemisorption between the reactant and catalyst to achieve a defect engineering strategy for synergetic photocatalysis.
- Yang, Xue,Tao, Huilin,Leow, Wan Ru,Li, Jingjun,Tan, Yanxi,Zhang, Yongfan,Zhang, Teng,Chen, Xiaodong,Gao, Shuiying,Cao, Rong
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p. 116 - 125
(2019/04/08)
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- Efficient and selective oxidation of alcohols in water employing palladium supported nanomagnetic Fe3O4@hyperbranched polyethylenimine (Fe3O4@HPEI.Pd) as a new organic–inorganic hybrid nanocatalyst
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Palladium immobilized magnetic nanoFe3O4@hyperbranched polyethylenimine (Fe3O4@HPEI.Pd) was prepared according to a simple and cost effective pathway and it was employed as a new efficient and selective organic–inorganic hybrid nanocatalyst for the aqueous oxidation of primary and secondary alcohols to their corresponding products in good yields applying oxone (potassium hydrogen monopersulfate) and H2O2 as an oxidant at room temperature. Moreover, the catalytic system was reused at least 13 times without significant loss of activity. The complete characterization of this efficient nanocatalyst was investigated by FTIR, UV–Vis, TEM, SEM, XRD, TGA, VSM, ICP and EDX techniques.
- Ramazani, Ali,Khoobi, Mehdi,Sadri, Fariba,Tarasi, Roghayeh,Shafiee, Abbas,Aghahosseini, Hamideh,Joo, Sang Woo
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- Novel nanomagnetic Ag/β-Ag2WO4/CoFe2O4 as a highly efficient photocatalyst under visible light irradiation
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A visible light-driven magnetic Ag/β-Ag2WO4/CoFe2O4 nanophotocatalyst is successfully prepared using a facial method and characterized via FT-IR, XRD, SEM, EDS, VSM, DRS, BET, TEM, XPS and PL analysis. The obtained CoFe2O4 nanoparticles and Ag/β-Ag2WO4/CoFe2O4 nanocomposite exhibit a flower-like morphology and average diameter of 35 and 43 nm, respectively. The Ag/β-Ag2WO4/CoFe2O4 nanocomposite exhibits a two-fold enhancement in photocatalytic activity toward the oxidation of primary alcohols under visible light irradiation compared to that of CoFe2O4 and Ag/β-Ag2WO4. The photocatalytic efficiency of the CoFe2O4 and Ag/β-Ag2WO4 nanoparticles is 43% and 51%, respectively, whereas for Ag/β-Ag2WO4/CoFe2O4 it is 85%. This enhancement in photocatalytic activity is attributed to the effective separation of electron-hole pairs. The trapping experiment shows that OH and h+ are the main species involved in the photocatalytic activity of the Ag/β-Ag2WO4/CoFe2O4 nanocomposite system. This robust and high-performance magnetic photocatalyst is recovered easily with a permanent magnet and can be reused five times without significant changes in its efficiency. Also, a radical chain mechanism is proposed.
- Ghobadifard, Mahdieh,Mohebbi, Sajjad
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p. 9530 - 9542
(2018/06/18)
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- Mechanistic Insights into Aerobic Oxidative Methyl Esterification of Primary Alcohols with Heterogeneous PdBiTe Catalysts
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Aerobic oxidative methyl esterification of primary alcohols is an important chemical transformation that converts a nucleophile (alcohol) into a versatile electrophile (methyl ester). We recently discovered a heterogeneous PdBiTe/C catalyst that exhibits the highest activity yet reported for this transformation. Bi and Te serve as synergistic promoters that enhance both the rate and yield of the reactions relative to reactions employing Pd alone or Pd in combination with Bi or with Te as the sole promoter. Here, we report a mechanistic study of the oxidative methyl esterification of benzyl alcohol and 1-octanol to provide insights into the overall multistep transformation as well as the role of the Bi and Te in the reaction. The catalytic rates of the oxidative esterification of benzyl alcohol and octanol with Pd, PdBi, PdTe, and PdBiTe catalysts exhibit a saturation dependence on [alcohol] and [K2CO3] and a first-order dependence on pO2. Hammett studies of benzyl alcohol oxidation reveal opposing electronic trends for initial rates of oxidation of alcohol to aldehyde (negative ? value) and the oxidation of aldehyde to methyl ester (positive ? value). These data and complementary kinetic isotope effect data support a Langmuir-Hinshelwood mechanism in which a surface-bound alkoxide or hemiacetal intermediate undergoes rate-limiting β-hydride elimination. Molecular oxygen participates in this process, as revealed by a first-order dependence on pO2. X-ray photoelectron and X-ray absorption spectroscopic methods show that the promoters undergo oxidation in preference to Pd, maintaining the Pd surface in the active metallic state and preventing inhibition by surface Pd-oxide formation. Collectively, these results provide valuable insights into the synergistic benefits of multiple promoters in heterogeneous catalytic oxidation reactions.
- Mannel, David S.,King, Jesaiah,Preger, Yuliya,Ahmed, Maaz S.,Root, Thatcher W.,Stahl, Shannon S.
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p. 1038 - 1047
(2018/02/14)
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- Highly Productive Oxidative Biocatalysis in Continuous Flow by Enhancing the Aqueous Equilibrium Solubility of Oxygen
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We report a simple, mild, and synthetically clean approach to accelerate the rate of enzymatic oxidation reactions by a factor of up to 100 when compared to conventional batch gas/liquid systems. Biocatalytic decomposition of H2O2 is used to produce a soluble source of O2 directly in reaction media, thereby enabling the concentration of aqueous O2 to be increased beyond equilibrium solubility under safe and practical conditions. To best exploit this method, a novel flow reactor was developed to maximize productivity (g product L?1 h?1). This scalable benchtop method provides a distinct advantage over conventional bio-oxidation in that no pressurized gas or specialist equipment is employed. The method is general across different oxidase enzymes and compatible with a variety of functional groups. These results culminate in record space-time yields for bio-oxidation.
- Chapman, Michael R.,Cosgrove, Sebastian C.,Turner, Nicholas J.,Kapur, Nikil,Blacker, A. John
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supporting information
p. 10535 - 10539
(2018/08/17)
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- Oxidation of Alcohols to Carbonyl Compounds Catalyzed by Oxo-Bridged Dinuclear Cerium Complexes with Pentadentate Schiff-Base Ligands under a Dioxygen Atmosphere
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Ionic mononuclear and neutral dinuclear complexes of cerium(III) 3-L1-3-L9 bearing a series of dianionic pentadentate Schiff-base ligands were synthesized, characterized, and used as catalysts for N-oxyl radical-free aerobic alcohol oxidation. Reactions of Ce(NO3)3·6H2O with o-tert-butyl-substituted sterically hindered ligands NH(CH2CH2-Rfnet=CHC6H2-3-(tBu)-5-R2-2-OH)2 (for L1H2, R2 = tBu; for L2H2, R2 = OMe; and for L3H2, R2 = H) in the presence of triethylamine afforded the corresponding anionic cerium complexes [HNEt3][Ce(L1-3)(NO3)2] (3-L1-3-L3), whereas complexation with sterically less hindered ligands, such as NH(CH2CH2N=CHC6H2-3-R1-5-R2-2-OH)2 (for L4H2, R1 = OMe and R2 = H; for L5H2, R1 = H and R2 = tBu; for L6H2, R1 = H and R2 = OMe; for L7H2, R1 = H and R2 = H; for L8H2, R1 = H and R2 = NO2; and for L9H2, R1 = tBu and R2 = NO2), afforded neutral dinuclear complexes [Ce(L4-9)(NO3)]2 (3-L4-3-L9). Among these newly prepared complexes, complex 3-L1 was selected as the best catalyst for oxidizing primary and secondary alcohols under a dioxygen atmosphere without any N-oxyl radicals such as TEMPO to produce the corresponding carbonyl compounds, where the oxo-bridged dinuclear complex worked as a catalyst while maintaining its dinuclear skeleton during the catalytic cycle. In addition, an intramolecular redox process between the two cerium centers through the bridging oxygen atom played a key role in forming the ligand phenoxide radical-mediated TEMPO-free alcohol oxidation reaction.
- Shirase, Satoru,Shinohara, Koichi,Tsurugi, Hayato,Mashima, Kazushi
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p. 6939 - 6947
(2018/06/25)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by benzimidazolium dichromate - A kinetic and mechanistic aspects
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The oxidation of a number of para- and meta-substituted benzyl alcohols by benzimidazolium dichromate (BIDC), in dimethyl sulphoxide, leads to the formation of the corresponding benzaldehydes. The reaction is first order with respect to each BIDC and alcohol. The reaction is catalyzed by hydrogen ions and the dependence has the form kobs = a + b[H+]. The oxidation of [1,1-2H2]benzyl alcohol exhibited the presence of a substantial kinetic isotope effect. The rates of the oxidation of meta-substituted benzyl alcohols correlated best with Taft's σ1 and σR0 constants. The para-substituted compounds exhibited excellent correlation with σ1 and σRBA values. The polar reaction constants are negative. The rate of oxidation of benzyl alcohol was determined in nineteen organic solvents. An analysis of the solvent effect by multiparametric equations indicated the greater importance of the cation-solvating power of the solvents. Suitable mechanisms have been discussed.
- Kumar, Pravesh,Panday, Dinesh,Kothari, Seema
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p. 1207 - 1215
(2020/06/27)
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- Rhodium-Catalyzed Formylation of Aryl Halides with CO2 and H2
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The reductive formylation of aryl iodides/bromides to aryl aldehydes using CO2/H2 is presented for the first time. It was realized over a catalytic system composed of RhI3 or RhI3/Pd(dppp)Cl2 (dppp = 1,3-bis(diphenyphosphino)propane) and PPh3 in the presence of Ac2O/Et3N at 100 °C, affording aromatic aldehydes in good to excellent yields, together with good functional-group tolerance and broad substrate scope. The reaction proceeds through three cascade steps, involving HCOOH formation, CO release, and formylation of aryl halides.
- Liu, Zhenghui,Yang, Zhenzhen,Yu, Bo,Yu, Xiaoxiao,Zhang, Hongye,Zhao, Yanfei,Yang, Peng,Liu, Zhimin
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supporting information
p. 5130 - 5134
(2018/09/13)
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- Sodium copper chlorophyllin catalyzed chemoselective oxidation of benzylic alcohols and diarylmethanes in water
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We report the highly efficient and chemoselective oxidation of benzylic alcohols catalyzed by sodium copper chlorophyllin in water, producing corresponding arylcarbonyl compounds. Importantly, the catalytic system exhibits a wide substrate scope and high functional group tolerance. Moreover, secondary alcohols and even diarylmethanes were smoothly oxidized to the desired aryl ketones with excellent yields.
- Liu, Shi-juan,Zhang, Miao,Lu, Rong,Li, Xiu-ying,Che, Guang-bo
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- Selective aerobic oxidation of halides and amines with an inorganic-ligand supported zinc catalyst
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A practical, efficient and environmentally benign catalytic protocol for the oxidative cross-coupling reaction of halides with amines, oxidative self-coupling of amines and oxidation of halides was developed with inorganic-ligand supported ZnPOM (NH4)4[ZnMo6O18(OH)6] using molecular oxygen. This method mainly utilizes an inorganic polymolybdate ligand to support the Zn2+ ion, avoiding the use of complicated organic ligands.
- Wang, Jingjing,Zhai, Yongyan,Wang, Ying,Yu, Han,Zhao, Wenshu,Wei, Yongge
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supporting information
p. 13323 - 13327
(2018/10/15)
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- Visible-Light-Driven Photocatalytic Oxidation of Organic Chlorides Using Air and an Inorganic-Ligand Supported Nickel-Catalyst Without Photosensitizers
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Engineering photoredox-triggered chemical transformation via visible light has been an emerging area in organic synthesis. However, most of the well-established photocatalysts are based upon either transition metal complexes involved with noble metals and organic ligands or photosensitive organic dyes, the development of pure inorganic molecular photocatalysts that could provide better stability and durability is greatly retarded. Herein we discover that the Anderson polyoxometalate (POM) Na4[NiMo6O18(OH)6] (1), which consists of pure inorganic framework built from a central NiII core supported by six MoVIO6 inorganic scaffold/ligands, can be used as a powerful photocatalyst. Upon irradiation with visible light (>400 nm), the compound can catalyze, in high efficiency, a wide range of reactions, including the oxidative cross-coupling reaction of chlorides with amines, as well as oxidation of chlorides using molecular oxygen, affording various imines, aldehydes, and ketones, respectively in high selectivity and good yields. Owing to the robust inorganic framework, this catalyst exhibits excellent stability during the catalysis and reusability with little loss of the catalytic activity, thus providing an alternative without use of complicated organic ligands and expensive noble metal-based photosensitizers.
- Yu, Han,Wang, Jingjing,Zhai, Yongyan,Zhang, Mengqi,Ru, Shi,Han, Sheng,Wei, Yongge
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p. 4274 - 4279
(2018/09/10)
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- Method for preparing m-fluorobenzaldehyde from m-fluorotoluene through continuous oxidation
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The invention provides a method for preparing m-fluorobenzaldehyde from m-fluorotoluene through continuous oxidation and belongs to the technical field of an organic synthesis process. The method is a technology for preparing m-fluorobenzaldehyde from m-fluorotoluene through continuous oxidation in a tubular reactor by adopting an m-fluorotoluene compound as a raw material, one or more metal ion complexes of cobalt, molybdenum and bromine as a catalyst, hydrogen peroxide as an oxidant and acetic acid as a solvent. The method has the advantages of mild conditions, short reaction time and high raw material utilization rate, can effectively control a reaction process, is safe and stable, realizes continuous operation and has high production efficiency.
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Paragraph 0028; 0030; 0032; 0034; 0036; 0038; 0040-0042
(2017/08/29)
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- Dual Catalysis for the Aerobic Oxidation of Benzyl Alcohols – Nitric Acid and Fluorinated Alcohol
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Benzyl alcohols were oxidized with oxygen to aldehydes in excellent yields with high selectivities at room temperature. Dual catalysis was operative with HNO3as the oxidant and precursor of the nitrogen oxides and with the use of 1,1,1,3,3,3-hexafluoro-2-propanol as a template catalyst and solvent. Fluorinated alcohols also increased the selectivity by inhibiting further oxidation to benzoic acids. Activation of nitric acid catalyzed aerobic oxidation by the fluorinated solvent made the use of 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) or a metal catalyst superfluous.
- Mo?ina, ?tefan,Stavber, Stojan,Iskra, Jernej
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supporting information
p. 448 - 452
(2017/02/05)
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- Visible-light-driven selective oxidation of alcohols using a dye-sensitized TiO2-polyoxometalate catalyst
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This study demonstrated a dye-sensitized TiO2-polyoxometalate system (denoted TiO2-(PW12-TH)8, where PW12?=?PW12O403? and TH?=?thionine) for selective oxidation of alcohols under visible light. The results showed that various substituted alcohols were transformed into their corresponding aldehydes with high selectivity. Due to more efficient electrons transfer, large surface area, and enhanced visible light absorption, the photocatalytic activity of TiO2-(PW12-TH)8 was superior to any other dye-sensitized system reported to date. The response in the photocurrent-time curves over several on/off cycles of intermittent irradiation showed good reproducibility. The photocurrent response of TiO2-(PW12-TH)8 was much higher than that of TiO2/TH (physical mixture of TiO2 and TH), SiO2-(PW12-TH)8 or P25-(PW12-TH)8 (P25?=?Degussa P25), attributed to the more efficient transfer and longer lifetime of photoexcited electrons. This photocatalytic process confirmed that efficient electron transfer during photocatalytic oxidation plays a vital role in determining the reaction conversion and obtaining good selectivity. Electron paramagnetic resonance (EPR) spectra and radical scavenging experiments proved that superoxide radicals and electrons were the main reactive species in the proposed system, the absence of hydroxyl radicals and holes is demonstrated to be the key of high reaction selectivity.
- Yang, Xue,Zhao, Hui,Feng, Jifei,Chen, Yanning,Gao, Shuiying,Cao, Rong
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- H3PW12O40/mpg-C3N4 as an efficient and reusable bifunctional catalyst in one-pot oxidation-Knoevenagel condensation tandem reaction
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A single-site bifunctional catalyst for the oxidation-Knoevenagel condensation tandem reaction was prepared by the immobilization of phosphotungstic acid (HPW) on mesoporous graphitic carbon nitride (mpg-C3N4) via electrostatic interaction (HPW/mpg-C3N4). The results of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), solid-state 31P nuclear magnetic resonance (solid-state 31P NMR), zeta potentials, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) demonstrated that HPW was successfully immobilized on the protonated mpg-C3N4 by electrostatic interaction. The acid amounts of the catalysts were determined by NH3 temperature programmed desorption (NH3-TPD). The textural properties and morphology of HPW/mpg-C3N4 were characterized by N2 adsorption-desorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). 30% HPW/mpg-C3N4 shows the best catalytic performance in the tandem reaction with 98.4% benzyl alcohol conversion and 96.2% selectivity to benzylidene malononitrile. The excellent catalytic performance of 30% HPW/mpg-C3N4 in the tandem reaction is due to the good catalytic performance of HPW in the oxidation and Knoevenagel condensation, respectively. Furthermore, protonated mpg-C3N4 not only acts as a support to facilitate good dispersion of HPW but also promotes the Knoevenagel condensation reaction effectively. Moreover, the HPW/mpg-C3N4 catalyst could be recycled easily without significant loss of catalytic activity.
- Wang, Hefang,Wang, Cunyue,Yang, Yongfang,Zhao, Meng,Wang, Yanji
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p. 405 - 417
(2017/08/14)
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- Enhancement of the Oxidizing Power of an Oxoammonium Salt by Electronic Modification of a Distal Group
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The multigram preparation and characterization of a novel TEMPO-based oxoammonium salt, 2,2,6,6-tetramethyl-4-(2,2,2-trifluoroacetamido)-1-oxopiperidinium tetrafluoroborate (5), and its corresponding nitroxide (4) are reported. The solubility profile of 5 in solvents commonly used for alcohol oxidations differs substantially from that of Bobbitt's salt, 4-acetamido-2,2,6,6-tetramethyl-1-oxopiperidinium tetrafluoroborate (1). The rates of oxidation of a representative series of primary, secondary, and benzylic alcohols by 1 and 5 in acetonitrile solvent at room temperature have been determined, and oxoammonium salt 5 has been found to oxidize alcohols more rapidly than does 1. The rate of oxidation of meta- and para-substituted benzylic alcohols by either 1 or 5 displays a strong linear correlation to Hammett parameters (r > 0.99) with slopes (ρ) of -2.7 and -2.8, respectively, indicating that the rate-limiting step in the oxidations involves hydride abstraction from the carbinol carbon of the alcohol substrate.
- Lambert, Kyle M.,Stempel, Zachary D.,Kiendzior, Sadie M.,Bartelson, Ashley L.,Bailey, William F.
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p. 11440 - 11446
(2017/11/10)
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- Ligandless Palladium-Catalyzed Reductive Carbonylation of Aryl Iodides under Ambient Conditions
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Ligandless palladium-catalyzed reductive carbonylation of aryl iodides for the synthesis of aromatic aldehydes has been developed. This carbonylation process proceeded effectively even under ambient temperature and pressure. In addition, this method enables successive reductive carbonylation of diiodobenzenes to furnish dialdehydes in satisfactory yields. Finally, the nature of the active catalytic species is discussed.
- Han, Wei,Liu, Binbin,Chen, Junjie,Zhou, Qing
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supporting information
p. 835 - 840
(2017/04/06)
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- Highly selective copper-catalyzed oxidation of benzyl alcohols to aromatic aldehydes in water at room temperature
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Water-soluble 2N2O–Cu(II) complexes were synthesized and used for the catalytic oxidation of benzylic alcohols to the corresponding aldehydes in pure water resulting in high yields of up to 94%. Importantly, the catalytic system exhibits a wide substrate scope, high functional group tolerance and can be reused directly for subsequent reaction cycles. Using this catalytic system, the product 4-methylbenzaldehyde can be produced on a multi-gram scale and in the complete absence of any organic solvent, surfactant or phase transfer reagent. Copyright
- Wu, Jianglong,Liu, Yan,Ma, Xiaowei,Liu, Ping,Gu, Chengzhi,Dai, Bin
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p. 577 - 580
(2016/07/16)
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- Combined production method for substituted benzaldehyde, substituted benzyl alcohol and substituted benzoic acid
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The invention discloses a combined production method for substituted benzaldehyde, substituted benzyl alcohol and substituted benzoic acid. The method comprises the following steps: (1) oxidation: a step of continuously introducing substituted toluene, a catalyst and oxygen-contained gas into an oxidation reactor and carrying out reaction so as to obtain oxidation reaction liquid; (2) hydrolyzation: a step of allowing the oxidation reaction liquid to continuously enter a hydrolysis reactor, and continuously adding water into the hydrolysis reactor and carrying out reaction so as to obtain a hydrolysis reaction mixture; (3) liquid-liquid layering: a step of layering the hydrolysis reaction mixture so as to obtain an oil phase and an aqueous phase; and (4) separation of products: a step of subjecting the oil phase to distillation so as to respectively obtain incompletely-reacted substituted toluene, substituted benzyl alcohol and substituted benzaldehyde, and subjecting the aqueous phase to cooling, crystallizing and filtering so as to obtain filtrate and substituted benzoic acid. The combined production method provided by the invention has the advantages of high raw material conversion rate, few by-products, good selectivity of target products, greenness and environmental protection.
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Paragraph 0085; 0086
(2017/01/31)
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- Exploring the synthetic applicability of a new carboxylic acid reductase from Segniliparus rotundus DSM 44985
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A new carboxylic acid reductase (CAR) gene from Segniliparus rotundus DSM 44985 was overexpressed in Escherichia coli. The recombinant enzyme exhibited high activity toward a variety of aromatic and aliphatic carboxylic acids. Especially, it effectively reduced 4-hydroxybenzoic acid (8a) and 4-nitrobenzoic acid (19a), toward which the known Nocardia CAR exhibited no or little activity. The recombinant E. coli cells co-expressing the Segniliparus CAR and Nocardia PPTase genes catalyzed the reductions of vanillic acid (20a) and 3,4-dihydroxyphenylacetic acid (25a) to give vanillyl alcohol (20c) and 3-hydroxytyrosol (25c) with high yield, respectively. The endogenous aldehyde reductases of E. coli should be responsible for the further reduction of the produced aldehydes. These results demonstrated that Segniliparus CAR was a useful addition to the biocatalyst tool-box for the reduction of carboxylic acids and might find applications in the synthesis of valuable bio-based chemicals from renewable resources.
- Duan, Yitao,Yao, Peiyuan,Chen, Xi,Liu, Xiangtao,Zhang, Rui,Feng, Jinhui,Wu, Qiaqing,Zhu, Dunming
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- One-pot, selective and mild conversion of benzylic alcohols to gem -dichlorides using chlorodiphenylphosphine and 2,3-dichloro-5,6-dicyanobenzoquinone as a new and neutral system
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A mild and one-pot conversion of benzylic alcohols to their corresponding gem-dichlorides is reported for the first time using chlorodiphenylphosphine (ClPPh2) and 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) in dichloromethane under neutral conditions and at room temperature. The present method can be efficiently used for preparation of gem-dichlorides even in the presence of some other functional groups with excellent chemoselectivity.
- Aghapour, Ghasem,Mohamadian, Samaneh
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p. 520 - 527
(2015/05/20)
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- Aerobic oxidation of alcohols by copper(I)/benzoxazine ligand/TEMPO under mild and base-free conditions
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A novel benzoxazine ligand with an imidazole moiety was synthesized. This ligand in combination with Cu(OTf) and TEMPO efficiently catalyzed aerobic oxidation of active primary alcohols and also showed good to excellent activity in the oxidation of secondary alcohols under mild and base-free conditions.
- Zhang,Huang,Lü,Cao,Zhao
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p. 1965 - 1972
(2015/10/12)
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- Green and Efficient: Iron-Catalyzed Selective Oxidation of Olefins to Carbonyls with O2
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A mild and operationally simple iron-catalyzed protocol for the selective aerobic oxidation of aromatic olefins to carbonyl compounds is described. Catalyzed by a Fe(III) species bearing a pyridine bisimidazoline ligand at 1 atm of O2, α- and β-substituted styrenes were cleaved to afford benzaldehydes and aromatic ketones generally in high yields with excellent chemoselectivity and very good functional group tolerance, including those containing radical-sensitive groups. With α-halo-substituted styrenes, the oxidation took place with concomitant halide migration to afford α-halo acetophenones. Various observations have been made, pointing to a mechanism in which both molecular oxygen and the olefinic substrate coordinate to the iron center, leading to the formation of a dioxetane intermediate, which collapses to give the carbonyl product. (Chemical Equation).
- Gonzalez-De-Castro, Angela,Xiao, Jianliang
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supporting information
p. 8206 - 8218
(2015/07/15)
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- Aldehydes and ketones formation: Copper-catalyzed aerobic oxidative decarboxylation of phenylacetic acids and α-hydroxyphenylacetic acids
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Aromatic aldehydes or ketones from copper catalyzed aerobic oxidative decarboxylation of phenylacetic acids and α-hydroxyphenylacetic acids have been synthesized. This reaction combined decarboxylation, dioxygen activation, and C-H bond oxidation steps in a one-pot protocol with molecular oxygen as the sole terminal oxidant. This reaction represents a novel decarboxylation of an sp3-hybridized carbon and the use of a benzylic carboxylic acid as a source of carbonyl compounds.
- Feng, Qiang,Song, Qiuling
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p. 1867 - 1871
(2014/03/21)
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- Aerobic oxidation of alcohols by using a completely metal-free catalytic system
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A metal-free reaction system of air, NH4NO3(cat), 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)(cat), and H +(cat) is introduced as a simple, safe, inexpensive, efficient and chemoselective mediator for aerobic oxidation of various primary and secondary benzyl and alkyl alcohols, including those bearing oxidizable heteroatoms (N, S, O) to the corresponding aldehydes or ketones. Air oxygen under slight overpressure plays the role of the terminal oxidant, which is catalytically activated by redox cycles of nitrogen oxides released from a catalytic amount of NH4NO3 and cocatalyzed by TEMPO (nitroxyl radical compound), under acidic conditions, which are essential for an overall activation of the reaction system. The synthetic value of this reaction system and its green chemical profile was illustrated by a 10 g scale-up experiment, performed in an open-air system by using a renewable and reusable polymer-supported form of TEMPO (OXYNITROXS100). The reaction solvent was recovered by distillation under atmospheric pressure, and the pure final product was isolated under reduced pressure; the acid activators (HCl or H 2SO4) were recovered as ammonium salts. A metal-free reaction system of air/NH4NO3(cat)/TEMPO (cat)/H+(cat) is introduced as a simple, safe, inexpensive, efficient and chemoselective mediator for aerobic oxidation of various primary and secondary benzyl, alkyl and allyl alcohols, including those bearing oxidizable heteroatoms (N, S, O) to the corresponding aldehydes or ketones. Copyright
- Prebil, Rok,Stavber, Gaj,Stavber, Stojan
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supporting information
p. 395 - 402
(2014/01/23)
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- Heterocycle-substituted tetrazole ligands for copper-catalysed aerobic oxidation of alcohols
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An efficient copper-catalysed aerobic oxidation of alcohols has been established, which employed heterocycle-substituted tetrazoles as ligands. The commercially available (S)-5-(pyrrolidin-2-yl)-1H-tetrazole proved as the best ligand for this oxidation. Under optimized conditions, the substrate scope was broadened. A plausible mechanism was also proposed.
- Liu, Yangyang,Xie, Aming,Li, Junjian,Xu, Xiao,Dong, Wei,Wang, Boliang
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p. 9791 - 9796
(2015/01/09)
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- Aerobic Oxidation of Alcohols by Using a Completely Metal-Free Catalytic System
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A metal-free reaction system of air, NH4NO3(cat), 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)(cat), and H+(cat) is introduced as a simple, safe, inexpensive, efficient and chemoselective mediator for aerobic oxidation of various primary and secondary benzyl and alkyl alcohols, including those bearing oxidizable heteroatoms (N, S, O) to the corresponding aldehydes or ketones. Air oxygen under slight overpressure plays the role of the terminal oxidant, which is catalytically activated by redox cycles of nitrogen oxides released from a catalytic amount of NH4NO3 and cocatalyzed by TEMPO (nitroxyl radical compound), under acidic conditions, which are essential for an overall activation of the reaction system. The synthetic value of this reaction system and its green chemical profile was illustrated by a 10 g scale-up experiment, performed in an open-air system by using a renewable and reusable polymer-supported form of TEMPO (OXYNITROXS100). The reaction solvent was recovered by distillation under atmospheric pressure, and the pure final product was isolated under reduced pressure; the acid activators (HCl or H2SO4) were recovered as ammonium salts.
- Prebil, Rok,Stavber, Gaj,Stavber, Stojan
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supporting information
p. 395 - 402
(2015/10/05)
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- Magnetic CoFe2O4 nanoparticles as an efficient catalyst for the oxidation of alcohols to carbonyl compounds in the presence of oxone as an oxidant
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Magnetically nano-CoFe2O4 efficiently catalyzes oxidation of primary and secondary benzylic and aliphatic alcohols to give the corresponding carbonyl products in good yields. The reactions were carried out in an aqueous medium at room temperature in the presence of oxone (potassium hydrogen monopersulfate) as an oxidant. In addition, the catalysts could be reused up to 6 runs without significant loss of activities. Catalyst was characterized by SEM, XRD and IR.
- Sadri, Fariba,Ramazani, Ali,Massoudi, Abdolhossain,Khoobi, Mehdi,Azizkhani, Vahid,Tarasi, Roghayeh,Dolatyari, Leila,Min, Bong-Ki
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p. 2029 - 2032
(2014/09/17)
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- Mild, efficient oxidation of alcohols to aldehydes and ketones with periodic acid catalyzed by sym-collidinium chlorochromate (S-COCC) and DFT studies, HOMO-LUMO and MEPs mappings of products
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A facile sym-collidinium chlorochromate (S-COCC) catalyzed (2 mol%) oxidations of alcohols to aldehydes or ketones using 1 equiv of H5IO6 as oxidant in acetonitril at room temperature with excellent yields is described. A mild and efficient method has been optimized for S-COCC catalyst by considering the effect of various parameters such as the reaction time, the amount of catalyst and the reusability of the catalyst after several runs without modification. Furthermore, over oxidation of aldehydes to carboxylic acids is not observed by this method. Theoretical calculations on the compounds were carried out at the B3LYP/6-31G level. The geometry optimization, atomic charges, isotropic shielding value (σiso), thermodynamic parameters, frontier molecular orbitals (FMOs) and molecular electrostatic potentials (MEPs) were discussed.
- Shiri, Lotfi,Sheikh, Davood,Sheikhi, Masoome
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p. 825 - 834
(2015/06/30)
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