- Solution Dynamics of Hybrid Anderson-Evans Polyoxometalates
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Understanding the stability and speciation of metal-oxo clusters in solution is essential for many of their applications in different areas. In particular, hybrid organic-inorganic polyoxometalates (HPOMs) have been attracting increasing attention as they combine the complementary properties of organic ligands and metal-oxygen nanoclusters. Nevertheless, the speciation and solution behavior of HPOMs have been scarcely investigated. Hence, in this work, a series of HPOMs based on the archetypical Anderson-Evans structure, δ-[MnMo6O18{(OCH2)3C-R}2]3-, with different functional groups (R = -NH2, -CH3, -NHCOCH2Cl, -NCH(2-C5H4N) {pyridine; -Pyr}, and -NHCOC9H15N2OS {biotin; -Biot}) and countercations (tetrabutylammonium {TBA}, Li, Na, and K) were synthesized, and their solution behavior was studied in detail. In aqueous solutions, decomposition of HPOMs into the free organic ligand, [MoO4]2-, and free Mn3+ was observed over time and was shown to be highly dependent on the pH, temperature, and nature of the ligand functional group but largely independent of ionic strength or the nature of the countercation. Furthermore, hydrolysis of the amide and imine bonds often present in postfunctionalized HPOMs was also observed. Hence, HPOMs were shown to exhibit highly dynamic behavior in solution, which needs to be carefully considered when designing HPOMs, particularly for biological applications.
- Salazar Marcano, David E.,Lentink, Sarah,Moussawi, Mhamad A.,Parac-Vogt, Tatjana N.
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- In situ formation of steroidal supramolecular gels designed for drug release
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In this work, a steroidal gelator containing an imine bond was synthesized, and its gelation behavior as well as a sensitivity of its gels towards acids was investigated. It was shown that the gels were acid-responsive, and that the gelator molecules could be prepared either by a conventional synthesis or directly in situ during the gel forming process. The gels prepared by both methods were studied and it was found that they had very similar macro- and microscopic properties. Furthermore, the possibility to use the gels as carriers for aromatic drugs such as 5-chloro-8-hydroxyquinoline, pyrazinecarboxamide, and antipyrine was investigated and the prepared two-component gels were studied with regard to their potential applications in drug delivery, particularly in a pH-controlled drug release.
- Bunzen, Hana,Kolehmainen, Erkki
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- Copper-catalyzed selective oxygenation of methyl and benzyl substituents in pyridine with O2
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A selective oxygenation of picolines and their derivatives has been achieved by usingasimple copper salt as a catalyst and molecular oxygen as an oxidant, where the α-position of the alkyl substituent is selectively oxidized to give the corresponding aldehydes or ketones. Addition of a catalytic amount of water enhances the catalytic activity, which could be attributed to the role of the proton donor to activate the substrates.
- Abe, Tsukasa,Tanaka, Shinji,Ogawa, Atsuko,Tamura, Masanori,Sato, Kazuhiko,Itoh, Shinobu
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- MECHANISM OF THE CATALYTIC OXIDATION OF NITROGEN-CONTAINING METHYL-SUBSTITUTED HETEROCYCLES TO HETARYL ALDEHYDES
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An interrelationship between the electronic structure of methyl derivatives of nitrogen-containing hetrocyclic compounds and the character of the interaction with the catalyst, the mechanism of heterogeneous-catalytic oxidation, and the selectivity of the process was established.
- Leitis, L. Ya.,Skolmeistere, R. A.,Shimanskaya, M. V.
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- THE ONE-POT CONVERSION OF CARBOXYLIC ACIDS TO ALDEHYDES VIA ACTIVATED SILYL CARBOXYLATES.
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The transformation of acids into aldehydes in a one-pot process is performed through the thermal decomposition of pentacoordinated silicon species.
- Corriu, R. J. P.,Lanneau, G. F.,Perrot, M.
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- Improving the reactivity of hydrazine-bearing MRI probes for: In vivo imaging of lung fibrogenesis
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Pulmonary fibrosis (PF) is the pathologic accumulation of extracellular matrix components in lung tissue that result in scarring following chronic lung injury. PF is typically diagnosed by high resolution computed tomography (HRCT) and/or invasive biopsy. However, HRCT cannot distinguish old injury from active fibrogenesis. We previously demonstrated that allysine residues on oxidized collagen represent an abundant target during lung fibrogenesis, and that magnetic resonance imaging (MRI) with a small-molecule, gadolinium-containing probe, Gd-Hyd, could specifically detect and stage fibrogenesis in a mouse model. In this work, we present an improved probe, Gd-CHyd, featuring an N,N-dialkyl hydrazine which has an order of magnitude both greater reactivity and affinity for aldehydes. In a paired study in mice with bleomycin induced lung injury we show that the improved reactivity and affinity of Gd-CHyd results in significantly higher lung-to-liver contrast, e.g. 77% higher at 45 min post injection, and slower lung clearance than Gd-Hyd. Gd-CHyd enhanced MRI is >60-fold higher in bleomycin injured mouse lungs compared to uninjured mice. Collectively, our data indicate that enhancing hydrazine reactivity and affinity towards allysine is an effective strategy to significantly improve molecular MRI probes for lung fibrogenesis.
- Akam, Eman A.,Abston, Eric,Rotile, Nicholas J.,Slattery, Hannah R.,Zhou, Iris Y.,Lanuti, Michael,Caravan, Peter
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- Synthesis of pyrrolo[1,2-: A] quinoxalines via copper or iron-catalyzed aerobic oxidative carboamination of sp3C-H bonds
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An aerobic oxidative carboamination of sp3C-H bonds with 2-(1H-pyrrol-1-yl)anilines has been developed. The oxidative carboamination processes utilized simple and readily available starting materials to produce pyrrolo[1,2-a]quinoxalines in good to moderate yields. The transformations also featured inexpensive metal catalysts (copper or iron) and a green oxidant (O2).
- Dai, Chenshu,Deng, Siqi,Zhu, Qiuhua,Tang, Xiaodong
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- The Synergy Effect in Tio2 Supported Bi-Mo Catalysts for Facile and Environmentally-Friendly Synthesis of Pyridylaldehydes from Oxidation of Picolines
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Abstract: The oxidation of picolines to pyridlaldehydes was studied over bismuth molybdate catalysts supported on TiO2. The research results showed that α-Bi2Mo3O12 was superior to β-Bi2Mo2O9 and γ-Bi2MoO6 in terms of reactivity. Further doping MoO3 to α-Bi2Mo3O12/TiO2 gave rise to increased catalytic performance, which was due to the synergy effect of α-Bi2Mo3O12 and MoO3. The effect was on one hand manifested in the intimate relationship between α-Bi2Mo3O12 and MoO3 in stabilizing the crystallographic structure of catalysts and thereafter maintaining the surface area of the catalyst, as indicated by the BET surface area and XRD analysis. Moreover, NH3-TPD analysis demonstrated the effect in modifying the surface acidity of the catalysts, and thus facilitating the substrate adsorption as the picolines are alkaline substances. Additionally, the effect between α-Bi2Mo3O12 and MoO3 rendered the modification of the electronic properties and thereafter the oxygen desorption properties and reducible properties of the catalysts, as evidenced in the H2-TPR and O2-TPD analysis.
- Dai, Liyan,Jie, Yu,Zhylko, Viachaslau
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- Convenient and eco-friendly method for the conversion of benzylic alcohols into aldehydes, ketones, and carboxylic acids using NaOCl without any additives in 1,2-dimethoxyethane
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Oxidation of benzylic alcohols to aldehydes, ketones, and carboxylic acids using NaOCl in 1,2-dimethoxyethane without any additives has been developed. 4-Methylbenzyl alcohol and diphenyl methanol were converted into the corresponding aldehyde and ketone in 97% and 92% yield, respectively. Furthermore, 4-nitrobenzyl alcohol was directly converted into the corresponding carboxylic acid in 99% yield. Georg Thieme Verlag Stuttgart · New York.
- Fukuda, Naohiro,Kajiwara, Takeshi,Katou, Tomoaki,Majima, Keisuke,Ikemoto, Tomomi
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- An Optical Resolution of Pyridyl and Bipyridylethanols and A Facile Preparation of Optically Pure Oligopyridines
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A kinetic resolution of racemic pyridyl and bipyridylethanols was performed by Candida antarctica lipase with vinyl acetate in diisopropyl ether, in which (R)-alcohol was acetylated stereoselectively, and both the acetate 2 and the remaining (S)-alcohol 1 were obtained with high enantiomeric excesses. (S)-Oligopyridylethanols, 7 and 8 were prepared by a coupling reaction of (S)-1b and (S)-1e with ethyl bipyridyl sulfoxide.
- Uenishi, Jun'ichi,Nishiwaki, Kenji,Hata, Shinichiro,Nakamura, Kaoru
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- Orthogonal Stimuli Trigger Self-Assembly and Phase Transfer of FeII4L4 Cages and Cargoes
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Two differently protected aldehydes, A and B, were demonstrated to deprotect selectively through the application of light and heat, respectively. In the presence of iron(II) and a triamine, two distinct FeII4L4 cages, 1 and 2, were thus observed to form from the deprotected A and B, respectively. The alkyl tails of B and 2 render them preferentially soluble in cyclopentane, whereas A and 1 remain in acetonitrile. The stimulus applied (either light or heat) thus determines the outcome of self-assembly and dictates whether the cage and its ferrocene cargo remain in acetonitrile, or transport into cyclopentane. Cage self-assembly and cargo transport between phases can in this fashion be programmed using orthogonal stimuli.
- McConnell, Anna J.,Haynes, Cally J. E.,Grommet, Angela B.,Aitchison, Catherine M.,Guilleme, Julia,Mikutis, Sigitas,Nitschke, Jonathan R.
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- Hydroxyl radical-mediated oxidative cleavage of CC bonds and further esterification reaction by heterogeneous semiconductor photocatalysis
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A hydroxyl radical-mediated aerobic cleavage of alkenes and further sequence esterification reaction for the preparation of carbonyl compounds have been developed by using tubular carbon nitride (TCN) as a general heterogeneous photocatalyst under an oxygen atmosphere with visible light irradiation. This protocol has an excellent substrate scope and gives the desired aldehydes, ketones and esters in moderate to high yields. Importantly, this metal-free procedure employed photogenerated hydroxyl radicals in situ as green oxidation active species, avoiding the present additional initiators. The reaction could be carried out under solar light irradiation and was applicable to large-scale reactions. Furthermore, the recyclable TCN catalyst could be used several times without a significant loss of activities.
- Hong, Mei,Jia, Rui,Miao, Hongyan,Ni, Bangqing,Niu, Tengfei,Wang, Hui
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p. 6591 - 6597
(2021/09/10)
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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 0020
(2021/09/26)
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- Method for preparing aldehyde compounds by oxidative cleavage of carbon-carbon bonds of terminal alkene compounds
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The invention discloses a method for preparing aldehyde compounds by oxidizing and breaking carbon-carbon bonds of terminal alkene compounds. The method comprises the following steps: adding an alkene-terminated compound, an additive and a nitrogen-doped mesoporous carbon-loaded monatomic catalyst into a fatty primary alcohol solvent, putting into a pressure container, sealing, introducing oxygen source gas with a certain pressure, controlling the pressure of the oxygen source gas to be 0.1-1MPa and the reaction temperature to be 80-150 DEG C, and obtaining a reaction product, namely the aldehyde compound. The nitrogen-doped mesoporous carbon-loaded monatomic catalyst adopted by the invention is high in activity, the highest separation yield of the aldehyde compound as a reaction product reaches 99%, the method is wide in application range, the reaction conditions are easy to control, the catalyst can be recycled, the post-treatment is simple, and the method is suitable for industrial production.
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Paragraph 0073-0074; 0089-0090
(2021/06/06)
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- Efficient synthesis of acrylates bearing an aryl or heteroaryl moiety: One-pot method from aromatics and heteroaromatics using formylation and the horner-wadsworth-emmons reaction
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Acrylates bearing an aryl or heteroaryl moiety were efficiently prepared by a one-pot process employing a sequence of lithiation, formylation and the Horner-Wadsworth-Emmons reaction starting from aromatic and heteroaromatic compounds. This method can efficiently introduce an acrylate moiety into aromatic and heteroaromatic compounds.
- Yasukata, Tatsuro,Matsuura, Takaharu
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p. 527 - 533
(2021/03/22)
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- PhSe(O)OH/NHPI-catalyzed oxidative deoximation reaction using air as oxidant
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A novel oxidative deoximation method was developed in this article. Compared with the reported organoselenium-catalyzed oxidative deoximation reaction, this reaction employed N-hydroxyphthalimide (NHPI) as the co-catalyst, so that the oxidative deoximation reaction could utilize air as oxidant in the green DMC solvent under mild reaction conditions. Control experiments and X-ray photoelectron spectroscopy (XPS) analysis results indicated that NHPI was essential for activating the catalytic organoselenium species. It could accelerate the activation of molecular oxygen in air to promote the reaction process. The reaction can avoid metal residues in product and is of potential application values in pharmaceutical industry due to the transition metal-free process.
- Shi, Yaocheng,Wang, Feng,Yang, Chenggen,Yu, Lei
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- Synthesis of new Zn (II) complexes for photo decomposition of organic dye pollutants, industrial wastewater and photo-oxidation of methyl arenes under visible-light
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Synthesis of new Schiff's base Zn-complexes for photo-oxidation of methyl arenes and xylenes are reported under visible light irradiation conditions. All the synthesized new ligands and Zn-complexes are thoroughly characterized with various spectral analyses and confirmed as 1:1 ratio of Zn and ligand with distorted octahedral structure. The bandgap energies of the ligands are higher than its Zn-complexes. These synthesized new Zn(II) complexes are used for the photo-fragmentation of organic dye pollutants, photodegradation of food industrial wastewater and oxidation of methyl arenes which are converted into its respective aldehydes with moderate yields under visible light irradiation. The photooxidation reaction dependency on the intensity of the visible light was also studied. With the increase in the dosage of photocatalyst, the methyl groups are oxidized to get aldehydes and mono acid products, which are also identified from LC-MS data. Finally, [Zn(PPMHT)Cl] is with better efficiency than [Zn(PTHMT)Cl] and [Zn(MIMHPT)Cl] for oxidation of methyl arenes is reported under visible-light-driven conditions.
- Ahemed, Jakeer,Bhongiri, Yadagiri,Chetti, Prabhakar,Gade, Ramesh,Kore, Ranjith,Pasha, Jakeer,Pola, Someshwar,Rao D, Venkateshwar
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- Oxidation/ MCR domino protocol for direct transformation of methyl benzene, alcohol, and nitro compounds to the corresponding tetrazole using a three-functional redox catalytic system bearing TEMPO/Co(III)-porphyrin/ Ni(II) complex
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A redox catalytic system for oxidation-reduction reactions and the domino preparation of tetrazole compounds from nitro and alcohol precursors was designed, prepared and characterized by UV–vis, GPC, TGA, XRD, EDX, XPS, VSM, FE-SEM, TEM, DLS, BET, NMR, and ICP analyses. The catalyst was prepared via several successive steps by demetalation of chlorophyll b, copolymerization with acrylated TEMPO monomers, complexation with Ni and Co metals (In two different steps), then immobilized on magnetic nanoparticles. The presence of three functional groups including TEMPO, coordinated cobalt, and coordinated nickel in the catalyst, allowed the oxidation of various types of alcohols, alkyl benzenes as well as the reduction of nitro compounds by a single catalyst. All reactions yielded up to 97 % selectivity for oxidation and reduction reactions. Next, the ability of the catalyst to successfully convert alcohol, methyl benzenes and nitro to their corresponding tetrazoles was studied.
- Mahmoudi, Boshra,Rostami, Amin,Kazemnejadi, Milad,Hamah-Ameen, Baram Ahmed
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- Iodine-imine Synergistic Promoted Povarov-Type Multicomponent Reaction for the Synthesis of 2,2′-Biquinolines and Their Application to a Copper/Ligand Catalytic System
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An efficient iodine-imine synergistic promoted Povarov-type multicomponent reaction was reported for the synthesis of a practical 2,2′-biquinoline scaffold. The tandem annulation has reconciled iodination, Kornblum oxidation, and Povarov aromatization, where the methyl group of the methyl azaarenes represents uniquely reactive input in the Povarov reaction. This method has broad substrate scope and mild conditions. Furthermore, these 2,2′-biquinoline derivatives had been directly used as bidentate ligands in metal-catalyzed reactions.
- Hu, Qi-Qi,Gao, Yan-Ting,Sun, Jia-Chen,Gao, Jing-Jing,Mu, Hong-Xiao,Li, Yi-Ming,Zheng, Ya-Nan,Yang, Kai-Rui,Zhu, Yan-Ping
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supporting information
p. 9000 - 9005
(2021/11/24)
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- A novel selective oxidative cleavage of C–C bond mediated by black nickel oxide in the presence of molecular oxygen
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A selective aerobic oxidative cleavage of C–C bond is developed with black nickel oxide (NiOx) as the catalyst. For the oxidation of 1-phenyl-1, 2-ethanediol, a 97.5% conversion in 96.7% selectivity of benzaldehyde is obtained under 0.3 MPa of O2 at 140 °C for 3 h. The relationship between the catalytic performance of NiOx and structure is discussed. It is concluded that the existence of Ni3+ should be crucial to the activity of catalyst. Moreover, the recycling experiments showed that the catalyst can retain a high activity even after being reused for five times.
- Meng, Lingwu,Li, Wei,Guo, Pengfei,Wang, Shun,Tong, Xinli
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- Visible-light-driven photochemical activity of ternary Ag/AgBr/TiO2nanotubes for oxidation C(sp3)-H and C(sp2)-H bonds
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The Ag/AgBr/TiO2 ternary component nanotube as a heterogeneous photocatalyst was used for the solvent-free oxidation of the benzylic C(sp3)-H bond to the corresponding carbonyl compound or the solvent-controlled selective oxidative cleavage of the CC double bond of styrene to benzaldehyde under visible light at room temperature. A wide variety of carbonyl compounds were successfully synthesized through the developed photocatalytic process. Several advantages such as solvent-free conditions, sans additional oxidant, simple reaction, short reaction time, and easy separation of the product promote the reaction to be green. Moreover, the Ag/AgBr/TiO2 nanotubes could be used several times without reduction in their photocatalytic activity. This journal is
- Hosseini-Sarvari, Mona,Dehghani, Abdulhamid
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p. 16776 - 16785
(2020/10/27)
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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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- Powerful and Phosphine-Free Palladium-Catalyzed Selective Formylation of Aryl Halides with Formic Acid as CO Source
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The phosphine-free palladium-based catalytic system Pd(OAC)2/DABCO has been developed for the carbonylative transformations of aryl halides with formic acid. The DABCO acts as a base as well as N-donor ligand to coordinate with metal ions and stabilize Pd-catalytic sites during the reaction process. Using DCC as the activator of formic acid and PEG as the reaction media. The aryl halides have been conveniently transformed into the corresponding aldehydes in moderate to excellent yields. Graphic Abstract: An efficient catalytic system Pd(OAc)2/ DABCO/ DCC for selective carbonylation of aryl halides with formic acid is described.[Figure not available: see fulltext.].
- Molaei, Elahe,Mohammadsaleh, Fatemeh,Niknam, Khodabakhsh
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p. 1970 - 1975
(2020/01/28)
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- Visible-light assisted of nano Ni/g-C3N4 with efficient photocatalytic activity and stability for selective aerobic C?H activation and epoxidation
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A selective, economical, and ecological protocol has been described for the oxidation of methyl arenes and their analogs to the corresponding carbonyl compounds and epoxidation reactions of alkenes with molecular oxygen (O2) or air as a green oxygen source, under mild reaction conditions. The nano Ni/g-C3N4 exhibited high photocatalytic activity, stability, and selectivity in the C?H activation of methyl arenes, methylene arenes, and epoxidation of various alkenes under visible- light irradiation without the use of an oxidizing agent and under base free conditions.
- Akrami, Zahra,Hosseini-Sarvari, Mona
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supporting information
(2020/10/13)
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- Method for preparing aromatic aldehyde ketone by catalytically oxidizing aromatic hydrocarbon side chains with nickel compound
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The invention relates to a method for preparing aromatic aldehyde ketone by catalytically oxidizing aromatic hydrocarbon side chains with a nickel compound, which comprises the following steps of: mixing a solution containing aromatic hydrocarbon with side chains and an oxidant with a nickel catalyst, and reacting to obtain the aromatic aldehyde ketone compound. Compared with the prior art, the method has the advantages of simple operation, environmental protection, cheap and easily available raw materials, mild reaction conditions, stable catalyst property, high catalytic activity, good substrate universality and the like, and has great application potential in the aspect of fine chemical intermediate synthesis.
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Paragraph 0065-0073
(2020/06/09)
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- Facile synthesis of 1,3,4-oxadiazoles via iodine promoted oxidative annulation of methyl-azaheteroarenes and hydrazides
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An oxidative sp3 C–H bond of methyl-azaheteroarenes protocol was reported for the synthesis of 1,3,4-oxadiazoles via [4 + 1] annulation with hydrazides. This protocol enables 1,3,4-oxadiazole and quinoline linked diheterocycles via selective oxidation of sp3 C–H bond of methyl-azaheteroarenes in the presence of I2-DMSO. The reaction has a broad substrate scope and good functional group tolerance for methyl-azaheteroarenes and hydrazides.
- Shang, Zhi-Hao,Sun, Ji-Na,Guo, Jiang-Shan,Sun, Yuan-Yuan,Weng, Wei-Zhao,Zhang, Zhen-Xiao,Li, Zeng-Jing,Zhu, Yan-Ping
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supporting information
(2020/01/08)
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- Oxyfunctionalization of Alkanes Based on a Tricobalt(II)-Substituted Dawson-Type Rhenium Carbonyl Derivative as Catalyst
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POM-supported metal carbonyl derivatives (PMCDs) represent a family of tremendous potential catalysts owing to their peculiar physical and chemical properties. Yet low-valence transition metal-substituted Dawson-type PMCD catalysts are uncommon. Hence, we synthesized a tricobalt-substituted PMCDs by conventional aqueous solution method, [Na(H2O)5](NH4)7[P2W15O56Co3(H2O)3(OH)3Re(CO)3]·13H2O (1), and characterized by single crystal X-ray diffraction crystallography, IR, and thermogravimetric analyses (TGA), etc. The obtained compound 1 was employed as a catalyst for the oxidation of diphenylmethane (DPM) to benzophenone, giving 96.8percent yield in the presence of tert-butyl hydroperoxide (TBHP) and pyridine. The control experiments indicate that Co metal ion plays an important role in the catalytic reactions. As a side note, the electrospray ionization mass spectrometry (ESI-MS) and UV spectroscopy showed that 1 can retain its integrity in solution, and magnetic measurements indicated that 1 exhibited a weaker ferromagnetic interaction at low temperature.
- Ma, Xinyi,Wang, Ping,Liu, Zhihao,Xin, Changhui,Wang, Siyu,Jia, Jiage,Ma, Pengtao,Niu, Jingyang,Wang, Jingping
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p. 8690 - 8698
(2020/07/03)
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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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- Polymer-incarcerated palladium-catalyzed facile: In situ carbonylation for the synthesis of aryl aldehydes and diaryl ketones using CO surrogates under ambient conditions
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In this existing work, an efficient polymer-supported palladium catalyst, a furfurylamine-functionalized Merrifield complex of palladium [Pd@(Merf-FA)], was synthesized and characterized, showing excellent catalytic activity towards in situ carbonylation reactions using carbon monoxide surrogates like formic acid and chloroform. Herein, we examined the catalytic activity of the Pd@(Merf-FA) catalyst for the formylation of aryl iodides and carbonylative Suzuki-Miyaura coupling reactions. The Pd@(Merf-FA) catalyst was systematically characterized by several techniques like HRTEM, elemental mapping, PXRD, TGA-DTA, FESEM, UV-vis, EDAX, CHN and AAS analysis. The catalyst is highly recyclable, able to be recycled up to six times without showing any significant decrease in catalytic activity. The [Pd@(Merf-FA)] catalyst proved to be more efficient compared to the corresponding homogeneous palladium catalyst. In addition, the leaching experiment of the synthesized catalyst was studied, which showed that negligible leaching of metal occurred from the polymeric support.
- Dey, Tusar Kanto,Basu, Priyanka,Riyajuddin, Sk,Ghosh, Aniruddha,Ghosh, Kaushik,Manirul Islam, Sk
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p. 9802 - 9814
(2019/07/04)
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- Metal-free nitrogen -doped carbon nanosheets: A catalyst for the direct synthesis of imines under mild conditions
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Herein, a highly stable, porous, multifunctional and metal-free catalyst was developed, which exhibited significant catalytic performance in the oxidation of amines and transfer hydrogenation of nitriles under mild conditions; this could be attributed to the presence of numerous active sites and their outstanding BET surface area. The obtained results showed that most of the yields of imines exceeded 90%, and the cycling performance of the catalyst could be at least seven runs without any decay in the reaction activity, which could be comparable to those of metal catalysts. Subsequently, a kinetic study has demonstrated that the apparent activation energy for the direct synthesis of imines from amines is 67.39 kJ mol-1, which has been performed to testify that the catalytic performances are rational. Via catalyst characterizations and experimental data, graphitic-N has been proven to be the active site of the catalyst. Hence, this study is beneficial to comprehend the mechanism of action of a metal-free N-doped carbon catalyst in the formation of imines.
- Wang, Kaizhi,Jiang, Pengbo,Yang, Ming,Ma, Ping,Qin, Jiaheng,Huang, Xiaokang,Ma, Lei,Li, Rong
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p. 2448 - 2461
(2019/05/17)
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- Switchable Bifunctional Bistate Reusable ZnO-Cu for Selective Oxidation and Reduction Reaction
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Herein we disclosed the utilization of copper loaded zinc oxide (ZnO-Cu) for its stimuli (O2/light) responsive switchable performance between its reduced (S-1) and oxidized (S-2) state for two antagonistic reactions, namely oxidation of alkyl arenes/heteroarenes to aldehydes/ketones and reduction of nitro arenes/heteroarenes to corresponding amines. The two states of the catalyst showed its switchable performance as highly active and poorly active catalyst for oxidation and reduction, and both reactions could be turned "off" and "on" by changing the stimuli (light and O2/N2). The switching efficiency between the states and their relative reactivity were found to be consistent under variety of reaction conditions and remain unaltered irrespective of oxidation-reduction (or vice versa) sequence and substrates used in the reaction. The photo catalysts (S-1 and S-2) demonstrated good catalytic activity, multiple reusability, broad substrate scope, and reasonable functional group tolerance for both the reactions and probed its quality performance in a large-scale setup. The system was used in an assisted tandem catalysis setup for the synthesis of benzyl amines utilizing both oxidation and reduction reaction by stimuli responsive switching between the states of the catalyst.
- Sarmah, Kasturi,Mukhopadhyay, Subhamoy,Maji, Tarun K.,Pratihar, Sanjay
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p. 732 - 745
(2019/01/11)
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- On/Off O2 Switchable Photocatalytic Oxidative and Protodecarboxylation of Carboxylic Acids
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Photoredox catalysis in recent years has manifested a powerful branch of science in organic synthesis. Although merging photoredox and metal catalysts has been a widely used method, switchable heterogeneous photoredox catalysis has rarely been considered. Herein, we open a new window to use a switchable heterogeneous photoredox catalyst which could be turned on/off by changing a simple stimulus (O2) for two opponent reactions, namely, oxidative and protodecarboxylation. Using this strategy, we demonstrate that Au@ZnO core-shell nanoparticles could be used as a switchable photocatalyst which has good catalytic activity to absorb visible light due to the localized surface plasmon resonance effect of gold, can decarboxylate a wide range of aromatic and aliphatic carboxylic acids, have multiple reusability, and are a reasonable candidate for synthesizing both aldehydes/ketones and alkane/arenes in a large-scale set up. Some biologically active molecules are also shown via examples of the direct oxidative and protodecarboxylation which widely provided pharmaceutical agents.
- Bazyar, Zahra,Hosseini-Sarvari, Mona
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p. 13503 - 13515
(2019/10/11)
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- Tandem Reactivity of a Self-Assembled Cage Catalyst with Endohedral Acid Groups
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Self-assembly of a carboxylic acid-containing ligand into an Fe4L6 iminopyridine cage allows endohedral positioning of the acid groups while maintaining a robust cage structure. The cage is an effective supramolecular catalyst, providing up to 1000-fold rate enhancement of acetal solvolysis. This enhanced reactivity allows a tandem deprotection/cage-to-cage interconversion that cannot be achieved with other acid catalysts. The combination of rate enhancements and sequestration of the reactive function confers both activity and selectivity on the process, mimicking enzymatic behavior.
- Holloway, Lauren R.,Bogie, Paul M.,Lyon, Yana,Ngai, Courtney,Miller, Tabitha F.,Julian, Ryan R.,Hooley, Richard J.
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supporting information
p. 8078 - 8081
(2018/06/27)
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- Preparation method for preparing 2-pyridylaldehyde by catalytic oxidation of 2-methylpyridine
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The invention discloses a preparation method for preparing 2-pyridylaldehyde by catalytic oxidation of 2-methylpyridine. The preparation method comprises the following steps of firstly adopting ammonium molybdate, sodium citrate, manganese acetate and sodium hydroxide as raw materials, preparing a composite catalyst, then adopting the 2-methylpyridine and glacial acetic acid, adding hydrogen peroxide for catalytic oxidation, dropwise adding acetic anhydride for reaction, and preparing acetic acid 2-pyridine methyl ester; then dropwise adding a sodium hydroxide solution into the acetic acid 2-pyridine methyl ester to carry out hydrolysis so as to prepare 2-pyridinemethanol; finally mixing and stirring the 2-pyridinemethanol and dichloromethane uniformly, transferring into a three-mouth flask, then adding the prepared composite catalyst and hydrogen peroxide, stirring to react for 1-3 hours at the temperature of 30-40 DEG C after the adding step is finished, cooling to room temperature after the reaction is ended, filtering, collecting filtrate, distilling at normal pressure to remove dichloromethane, then carrying out vacuum reduced-pressure distillation on residues, and collecting63-65 DEG C/1.73kPa of fractions to prepare the 2-pyridylaldehyde. The method provided by the invention is simple and environment-friendly, and the target-product yield is high.
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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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- An Improved Rapid and Mild Deoxygenation of Amine N-oxides
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An improved mild and selective method for the deoxygenation of a variety of amine N-oxides has been carried out in the presence of silica gel under mild conditions at room temperature to afford corresponding amines in relatively good yields without purification. The reaction is tolerant of a variety of functional groups such as hydroxyl, ester, acid, carbonyl, and cyano groups, as well as halogens. This method would be of great utility to synthesize various pyridines and amines easily.
- Rajesh
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p. 486 - 491
(2017/12/29)
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- Functional group transformation from amines to aldehydes via IBX oxidation
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IBX oxidation of secondary aryl amines has been applied towards their functional group transformation to aldehydes using a facile post-process with satisfactory yields. The oxidation of N-benzylmethylamine was used as a model substrate and suggested that the ratio of IBX oxidant to amine should be 2:1. Subsequently, several aryl amines were subjected to these standard conditions, which revealed that the oxidative activity depends on the electronic and steric structures of the substituent groups in the substrates. The oxidative selectivity to secondary amines was also discovered.
- Chen, Li-Xia,Huang, Yin-Hui,Cong, Hang,Tao, Zhu
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p. 661 - 667
(2018/02/28)
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- Synthesizing process of nitrogen-heterocyclic high-selectivity aldehyde
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The invention relates to a synthesizing process of nitrogen-heterocyclic high-selectivity aldehyde. The synthesizing process is characterized in that when nitrogen-heterocyclic nitrogen atoms have hydrogen atoms, pyrrole, piperidine and pyrazole are used as the initial raw materials, and the pyrrole, the piperidine and the pyrazole are allowed to have reaction with piperidine-1-formaldehyde under nitrogen atom protection to obtain required nitrogen-atom ortho-position aldehyde; when nitrogen-heterocyclic nitrogen atoms have no hydrogen atoms, pyridine and pyrimidine are used to have reaction with the piperidine-1-formaldehyde to obtain the required nitrogen-atom ortho-position aldehyde. The synthesizing process is simple to operate, few in steps and high in selectivity and is a universal method using nitrogen heterocycle to synthesize the nitrogen ortho-position aldehyde.
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Paragraph 0014; 0022; 0023; 0035; 0040; 0048; 0053
(2017/09/05)
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- Heterogeneous Sodium-Manganese Oxide Catalyzed Aerobic Oxidative Cleavage of 1,2-Diols
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The aerobic oxidative cleavage of 1,2-diols using a heterogeneous catalyst only based on earth-abundant metals manganese and sodium is reported for the first time. This reusable catalyst cleaves a variety of substrates into aldehydes or ketones with high selectivity. The reaction requires small catalytic loadings and is performed under mild conditions using ambient pressure O2 or air as the oxidant while producing water as the only by-product. Mechanistic investigations reveal a monodentate, two-electron oxidative fragmentation process involving a MnIV species. The eco-friendly, innocuous catalyst is compatible with a wide range of functional groups and conditions, making it highly competitive with classical reagents, such as periodic acid or lead tetraacetate, as a preferred method for activated 1,2-diols.
- Escande, Vincent,Lam, Chun Ho,Coish, Philip,Anastas, Paul T.
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supporting information
p. 9561 - 9565
(2017/08/01)
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- Palladium-Catalyzed Ligand-Controlled Selective Synthesis of Aldehydes and Acids from Aryl Halides and Formic Acid
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Selective synthesis is in the core of modern organic chemistry. In this communication, a novel ligand-dependent palladium-catalyzed carbonylation procedure for the divergent synthesis of aldehydes and carboxylic acids from easily available aryl halides was established. Under the same reaction conditions, the reaction pathway could be controlled by the ligands applied to give formylated and carboxylated products selectively. Sterically hindered monodentate ligands facilitated the reductive carbonylation and provided aldehydes, whereas bidentate ligands preferred the carboxylation reaction and produced carboxylic acids. A wide range of functional groups were tolerated, and the products were, in general, obtained in moderate to excellent yields.
- Wu, Fu-Peng,Peng, Jin-Bao,Meng, Ling-Shen,Qi, Xinxin,Wu, Xiao-Feng
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p. 3121 - 3124
(2017/08/29)
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- Characterization of Carboxylic Acid Reductases as Enzymes in the Toolbox for Synthetic Chemistry
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Carboxylic acid reductase enzymes (CARs) meet the demand in synthetic chemistry for a green and regiospecific route to aldehydes from their respective carboxylic acids. However, relatively few of these enzymes have been characterized. A sequence alignment with members of the ANL (Acyl-CoA synthetase/ NRPS adenylation domain/Luciferase) superfamily of enzymes shed light on CAR functional dynamics. Four unstudied enzymes were selected by using a phylogenetic analysis of known and hypothetical CARs, and for the first time, a thorough biochemical characterization was performed. Kinetic analysis of these enzymes with various substrates shows that they have a broad but similar substrate specificity. Electron-rich acids are favored, which suggests that the first step in the proposed reaction mechanism, attack by the carboxylate on the α-phosphate of adenosine triphosphate (ATP), is the step that determines the substrate specificity and reaction kinetics. The effects of pH and temperature provide a clear operational window for the use of these CARs, whereas an investigation of product inhibition by NADP+, adenosine monophosphate, and pyrophosphate indicates that the binding of substrates at the adenylation domain is ordered with ATP binding first. This study consolidates CARs as important and exciting enzymes in the toolbox for sustainable chemistry and provides specifications for their use as a biocatalyst.
- Finnigan, William,Thomas, Adam,Cromar, Holly,Gough, Ben,Snajdrova, Radka,Adams, Joseph P.,Littlechild, Jennifer A.,Harmer, Nicholas J.
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p. 1005 - 1017
(2017/03/27)
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- Synthesis method for 2-pyridylaldehyde
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The invention belongs to the field of organic chemistry and particularly relates to a synthesis method for 2-pyridylaldehyde. The method comprises the following steps of (1) adopting 2-methylpyridine as a raw material and obtaining 2-pyridine n-oxide through oxidation reaction under an acid condition; (2) synthesizing acetic acid-2-piperidinecarbonitrile by using the 2-pyridine n-oxide through acetic anhydride acylation rearrangement; (3) hydrolyzing the acetic acid-2-piperidinecarbonitrile to obtain 2-pyridinemethanol; and (4) carrying out oxidation reaction on the 2-pyridinemethanol to obtain the 2-pyridylaldehyde. The synthesis method has the advantages of being high in total yield, low in raw material price, short in reaction time, mild in condition and simple in technological operation.
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- Conversion of oxazolines to cyanomethyl esters with pyridinium hydrobromide perbromide in water
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Various aromatic and heterocyclic oxazolines were directly converted to respective cyanomethyl esters with pyridinium hydrobromide perbromide in water at room temperature.
- Sayama, Shinsei
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p. 1133 - 1142
(2017/06/13)
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- Synthesis and characterisation of cycloruthenated benzhydrazone complexes: Catalytic application to selective oxidative cleavage of olefins to aldehydes
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A simple and convenient method to synthesise new air-stable cyclometalated ruthenium(ii) complexes from the reaction of p-substituted acetophenone benzhydrazide ligands and [RuHCl(CO)(AsPh3)3] has been described. The complexes have been characterised by various methods, including elemental analysis, FT-IR, NMR (1H and 13C) and UV-vis. The molecular structures of complexes 3 and 4 have been determined by singlecrystal X-ray diffraction analysis which indicates the tridentate coordination mode of the ligand and the presence of a distorted octahedral geometry around the ruthenium ion. The complexes have been found to be a highly active catalytic system in the selective oxidative cleavage of a wide range of alkenes and alkynes in the presence of NaIO4 as an oxidant. Notably, the desired aldehyde products were obtained with high conversions and yields using 0.5 mol% catalyst loading within 30 min at room temperature. Furthermore, the influence of reaction parameters such as solvents, oxidants, temperature and catalyst loading was also investigated.
- Manikandan, Thimma Sambamoorthy,Ramesh, Rengan,Semeril, David
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p. 97107 - 97115
(2016/10/25)
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- A Convenient Palladium-Catalyzed Reductive Carbonylation of Aryl Iodides with Dual Role of Formic Acid
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Palladium-catalyzed reductive carbonylation of aryl halides represents a straightforward pathway for the synthesis of aromatic aldehydes. The known reductive carbonylation procedures either require CO gas or complexed compounds as CO sources. In this communication, we developed a palladium-catalyzed reductive carbonylation of aryl iodides with formic acid as the formyl source. As a convenient, practical, and environmental friendly methodology, no additional silane or H2 was required. A variety of aromatic aldehydes were isolated in moderate to excellent yields under mild reaction conditions. Notably, this is the first procedure on using formic acid as the formyl source. Say no to CO gas! A convenient, practical, and environmental friendly palladium-catalyzed reductive carbonylation of aryl iodides with formic acid as the formyl source has been developed (see scheme). No additional silane or H2 was required here. A variety of aromatic aldehydes were isolated in moderate to excellent yields under mild reaction conditions.
- Qi, Xinxin,Li, Chong-Liang,Wu, Xiao-Feng
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supporting information
p. 5835 - 5838
(2016/04/26)
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- N,N-Dicarboxymethyl hydrazine: An old but neglected reagent for chemoselective derivatization of carbonyl compounds
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N,N-Dicarboxymethyl hydrazine (DCMH) was found to be a chemoselective derivatization reagent of carbonyl compounds and its potential applications in organic synthesis was investigated for the first time. DCMH could be employed as a chemoselective protective reagent of aldehydes and gave the parent aldehydes in satisfactory yields. In proof-of-concept systems, DCMH could play the role of a scavenger to remove aldehydes in the presence of ketones. It was also used as a tagging reagent in the selective isolation of aldehyde from the complex mixture.
- Zhen, Maomin,Peng, Yanqing
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supporting information
p. 3443 - 3449
(2016/04/09)
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- Solvent-Free Aerobic Oxidation of Alcohols to Nitriles Catalyzed by Copper Iodide in Combination with a Quaternary Ammonium Modified TEMPO
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A catalytic system consisting of N,N-dimethyl-(4-(2,2,6,6-tetramethyl-1-oxyl-4-piperidoxyl)butyl)dodecyl ammonium bromide (TEMPO-Q), CuI and 2,2′-bipyridine was established. This catalytic system (CuI/bpy/TEMPO-Q) showed high activity and good to excellent selectivity in the oxidative conversion of various alcohols to the corresponding nitriles with molecular oxygen as terminal oxidant and aqueous ammonia as nitrogen source under solvent-free conditions. Besides, the catalytic system also offers the advantages of simplified workup procedure. This protocol thus represents a greener pathway for the synthesis of nitriles from alcohols. Graphical Abstract: TEMPO-Q, a compound with both a TEMPO and a quaternary ammonium moieties, in combination with copper iodide and 2,2′-bipyridine as a catalytic system performed well in the oxidation of alcohols to nitriles with molecular oxygen as terminal oxidant in aqueous ammonia under solvent-free conditions. The catalytic system not only offers the advantages of simplified workup procedure, but also has high activity and selectivity due to the phase transfer catalysis of TEMPO-Q[Figure not available: see fulltext.]
- Zhang, Yuecheng,Huang, Rong,Gao, Baosheng,Zhao, Jiquan
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p. 220 - 228
(2016/02/23)
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- Selective Enzymatic Transformation to Aldehydes in vivo by Fungal Carboxylate Reductase from Neurospora crassa
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The enzymatic reduction of carboxylic acids is in its infancy with only a handful of biocatalysts available to this end. We have increased the spectrum of carboxylate-reducing enzymes (CARs) with the sequence of a fungal CAR from Neurospora crassa OR74A (NcCAR). NcCAR was efficiently expressed in E. coli using an autoinduction protocol at low temperature. It was purified and characterized in vitro, revealing a broad substrate acceptance, a pH optimum at pH 5.5–6.0, a Tmof 45 °C and inhibition by the co-product pyrophosphate which can be alleviated by the addition of pyrophosphatase. The synthetic utility of NcCAR was demonstrated in a whole-cell biotransformation using the Escherichia coli K-12 MG1655 RARE strain in order to suppress overreduction to undesired alcohol. The fragrance compound piperonal was prepared from piperonylic acid (30 mM) on gram scale in 92 % isolated yield in >98% purity. This corresponds to a productivity of 1.5 g/L/h. (Figure presented.).
- Schwendenwein, Daniel,Fiume, Giuseppe,Weber, Hansj?rg,Rudroff, Florian,Winkler, Margit
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p. 3414 - 3421
(2016/11/13)
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- A new efficient phosphonium cerium nitrate oxidant for the selective oxidation of alkyl-substituted benzenes
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A straightforward and effective procedure for the preparation of 1,4- bis (triphenylphosphonium) butane cerium nitrate (BTPBCN) and its application as a selective oxidizing agent for oxidation of alkyl-substituted benzenes to their relating acylbenzenes in very good to high yields is reported.
- Heidari, Mohammad,Ershadifar, Mohammad,Hamid, Masoumeh,Badri, Rashid
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p. 944 - 947
(2016/11/22)
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- Method for directly synthesizing aldehydes from amines
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The invention discloses a method for directly synthesizing aldehydes from amines. The method comprises the following steps: mixing an oxidizer and amines in a mole ratio of (1.8-2.2):1, and heating under reflux in 120-200 times by mole of chloroform solution (on the basis of the mole of amines) to react for 6-24 hours; and after the reaction is finished, naturally cooling to room temperature, filtering to remove IBX (o-iodoxybenzoic acid) and the reduction product thereof ortho-iodosobenzoic acid, sequentially washing the filtrate with a 10% NaOH solution, a 1M hydrochloric acid solution, water and a saturated sodium chloride solution, respectively washing three times (about 10ml each time), and carrying out rotary evaporation to remove the solvent chloroform, thereby obtaining the corresponding product aldehyde. The method has the advantages of high yield, high selectivity, low cost and low energy consumption.
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Paragraph 0011
(2017/06/24)
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- Novel use of BiOCl as an efficient and selective reagent for cleavage of 2,4-dinitrophenylhydrazones to carbonyl compounds
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A novel use of bismuth oxychloride (BiOCl) as an efficient and selective catalyst for the clean cleavage of 2,4-dinitrophenylhydrazones under mild conditions is reported. The reactions proceed very smoothly, and the yields are good to excellent. Over oxidation of aldehydes to carboxylic acid and the formation of by-products were not observed. The catalyst could be recovered and reused for at least four reaction cycles without considerable loss of reactivity.
- Manesh, Abbas Amini,Azarin, Khadijeh
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p. 125 - 131
(2016/04/26)
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- Copper nanoparticles on dichromium trioxide: A highly efficient catalyst from copper chromium hydrotalcite for oxidant-free dehydrogenation of alcohols
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Stable copper(0) nanoparticles supported on chromium (Cu(0)/Cr2O3) are prepared from the composite precursor copper chromium hydrotalcite. The resulting Cu(0)/Cr2O3 catalyst is first used in the selective dehydrogenation of alcohols to aldehydes. More impressively, these dehydrogenations are performed without oxidants and yields of products are high. The stability of Cu(0)/Cr2O3 is also assessed by studying its recoverability and reusability for up to five cycles.
- Zhu, Yaoqin,Shen, Mengnan,Xia, Yonggen,Lu, Ming
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p. 152 - 156
(2015/03/30)
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- Reactivity-based dynamic covalent chemistry: Reversible binding and chirality discrimination of monoalcohols
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In an effort to develop reactivity-based dynamic covalent bonding and to expand the scope and application of the dynamic covalent chemistry, in situ-generated simple generic iminium ions were utilized for the dynamic covalent binding of monoalcohols with high affinity. Hammett analysis was conducted to manipulate the equilibrium and correlate with the reactivity of reactants. The structural features of aldehydes and secondary amines were identified, and both polar and steric effects have significant impact on the binding. In particular, the substrates which can participate in π-π and polar-π interactions are able to afford apparent equilibrium constants in the magnitude of 104 M-2, demonstrating the power of weak supramolecular forces to stabilize the dynamic covalent assembly. The generality of the assembly was validated with a series of mono secondary alcohols. To showcase the practicality of our system, chirality discrimination and ee measurement of chiral secondary alcohols were achieved.
- Zhou, Yuntao,Ye, Hebo,You, Lei
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p. 2627 - 2633
(2015/03/18)
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- Reduction of Weinreb amides to aldehydes under ambient conditions with magnesium borohydride reagents Dedicated to the memory of Professor Sheldon Shore
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Chloromagnesium dimethylaminoborohydride (ClMg+ [H3BNMe2]-, MgAB) is an analogue of the versatile lithium dialkylaminoborohydrides (LAB reagents), prepared by the reaction of dimethylamine-borane with methylmagnesium chloride. MgAB is a partial reducing agent for Weinreb amides under ambient conditions and is complementary to the commonly utilized lithium aluminum hydride (LiAlH4) and diisobutylaluminum hydride (DIBAL) reagents, while exhibiting enhanced chemoselectivity. To prevent over-reduction, the aldehyde products are readily isolated in good yields by forming the sodium bisulfite adducts. Aldehyde products can both be stored and later used as the bisulfite adducts, or can be regenerated from the bisulfite adducts by treatment with aqueous formaldehyde.
- Bailey, Christopher L.,Clary, Jacob W.,Tansakul, Chittreeya,Klabunde, Lucas,Anderson, Christopher L.,Joh, Alexander Y.,Lill, Alexander T.,Peer, Natalie,Braslau, Rebecca,Singaram, Bakthan
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supporting information
p. 706 - 709
(2015/01/30)
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