- Stepwise benzylic oxygenation via uranyl-photocatalysis
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Stepwise oxygenation at the benzylic position (1°, 2°, 3°) of aromatic molecules was comprehensively established under ambient conditions via uranyl photocatalysis to produce carboxylic acids, ketones, and alcohols, respectively. The accuracy of the stepwise oxygenation was ensured by the tunability of catalytic activity in uranyl photocatalysis, which was adjusted by solvents and additives demonstrated through Stern–Volmer analysis. Hydrogen atom transfer between the benzylic position and the uranyl catalyst facilitated oxygenation, further confirmed by kinetic studies. Considerably improved efficiency of flow operation demonstrated the potential for industrial synthetic application.
- Hu, Deqing,Jiang, Xuefeng
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supporting information
p. 124 - 129
(2022/01/19)
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- Visible light-mediated, high-efficiency oxidation of benzyl to acetophenone catalyzed by fluorescein
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An environmentally friendly aerobic oxidation of benzyl C(sp3)-H bonds to ketones via selective oxidation catalysis was developed. Fluorescein is an efficient photocatalyst with excellent chemical selectivity. The reaction has a wide substrate scope, and a successful gram-scale experiment demonstrated its potential industrial utility.
- Geng, Haoxing,Liu, Xin,Zhu, Qing
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supporting information
(2021/12/20)
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- Selective Activation of Unstrained C(O)-C Bond in Ketone Suzuki-Miyaura Coupling Reaction Enabled by Hydride-Transfer Strategy
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A Rh(I)-catalyzed ketone Suzuki-Miyaura coupling reaction of benzylacetone with arylboronic acid is developed. Selective C(O)-C bond activation, which employs aminopyridine as a temporary directing group and ethyl vinyl ketone as a hydride acceptor, occurs on the alkyl chain containing a β-position hydrogen. A series of acetophenone products were obtained in yields up to 75%.
- Zhong, Jing,Zhou, Wuxin,Yan, Xufei,Xia, Ying,Xiang, Haifeng,Zhou, Xiangge
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supporting information
p. 1372 - 1377
(2022/02/23)
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- One-Dimensional Organic Conjugated Polymers as Recyclable Heterogeneous Photocatalysts
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Organic conjugated polymers with long-range conjugation generally have strong light absorption capacity in the visible light region and impressive performance in charge transfer, which endows them great application potential in the field of opto-electronic materials. However, there are few reports on their use in photocatalytic reactions. At present, it has been reported that a variety of donor-acceptor (D?A) type organic dyes can be used in efficient organic photocatalytic transformations. We designed and synthesized one-dimensional organic conjugated polymers pPhCzBP-Th and pPhCzBP-DTh with D?A structure, and proved that they are good heterogeneous photo-redox catalysts, which can photocatalyze hydrodehalogenation reduction of α-bromoacetophenone and its derivatives. Due to the strong reducibility of the excited state, pPhCzBP-Th can also efficiently reduce α-chloroacetophenone. Furthermore, by simply wrapping the catalyst powder, high-efficient separation of products and catalysts recycling can be achieved.
- Lei, Zhexuan,Liu, Yiming,Ma, Yuguo,Mo, Yitian,Tong, Yujie
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supporting information
(2022/03/18)
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- Iron-catalyzed domino decarboxylation-oxidation of α,β-unsaturated carboxylic acids enabled aldehyde C-H methylation
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A practical and general iron-catalyzed domino decarboxylation-oxidation of α,β-unsaturated carboxylic acids enabling aldehyde C-H methylation for the synthesis of methyl ketones has been developed. This mild, operationally simple method uses ambient air as the sole oxidant and tolerates sensitive functional groups for the late-stage functionalization of complex natural-product-derived and polyfunctionalized molecules.
- Gong, Pei-Xue,Xu, Fangning,Cheng, Lu,Gong, Xu,Zhang, Jie,Gu, Wei-Jin,Han, Wei
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p. 5905 - 5908
(2021/06/18)
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- Site-Specific Oxidation of (sp3)C-C(sp3)/H Bonds by NaNO2/HCl
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A site-specific oxidation of (sp3)C-C(sp3) and (sp3)C-H bonds in aryl alkanes by the use of NaNO2/HCl was explored. The method is chemical-oxidant-free, transition-metal-free, uses water as the solvent, and proceeds under mild conditions, making it valuable and attractive to synthetic organic chemistry.
- Zhao, Jianyou,Shen, Tong,Sun, Zhihui,Wang, Nengyong,Yang, Le,Wu, Jintao,You, Huichao,Liu, Zhong-Quan
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p. 4057 - 4061
(2021/05/26)
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- Palladium-Aminopyridine Catalyzed C?H Oxygenation: Probing the Nature of Metal Based Oxidant
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A mechanistic study of direct selective oxidation of benzylic C(sp3)?H groups with peracetic acid, catalyzed by palladium complexes with tripodal amino-tris(pyriylmethyl) ligands, is presented. The oxidation of arylalkanes having secondary and tertiary benzylic C?H groups, predominantly yields, depending on the substrate and conditions, either the corresponding ketones or alcohols. One of the three 2-pyriylmethyl moieties, which is pending in the starting catalyst, apparently, facilitates the active species formation and takes part in stabilization of the high-valent Pd center in the active species, occupying the axial coordination site of palladium. The catalytic, as well as isotopic labeling experiments, in combination with ESI-MS data and DFT calculations, point out palladium oxyl species as possible catalytically active sites, operating essentially via C?H abstraction/oxygen rebound pathway. For the ketones formation, O?H abstraction/в-scission mechanism has been proposed.
- Lubov, Dmitry P.,Bryliakova, Anna A.,Samsonenko, Denis G.,Sheven, Dmitriy G.,Talsi, Evgenii P.,Bryliakov, Konstantin P.
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p. 5109 - 5120
(2021/11/10)
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- Synthesis and Catalytic Applications of Multinuclear Gold(I)-1,2,3-Triazolylidene Complexes
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A series of mono- to trinuclear gold(I) complexes (1–3) supported by oxo-functionalized 1,2,3-triazolylidenes have been prepared. All new compounds were fully characterized by means of 1H and 13C NMR spectroscopy, elemental analyses, and in the case of complexes 1 and 2 by x-ray diffraction. The catalytic performance of the new triazolylidene gold complexes was tested in several hydroelementation and cyclization processes employing a variety of alkynes as starting materials. According to the overall results, the trinuclear complex 3 displayed the highest catalytic activity in all processes, providing good to excellent yields under mild reaction conditions.
- Rendón-Nava, David,álvarez-Hernández, Alejandro,Mendoza-Espinosa, Daniel
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supporting information
p. 840 - 847
(2021/02/26)
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- Hydration of Alkynes to Ketones with an Efficient and Practical Polyoxomolybdate-based Cobalt Catalyst
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Hydration of alkynes to ketones is one of the most atom economical and universal methods for the synthesis of carbonyl compounds. However, the basic reaction usually requires organic ligand catalysts or harsh reaction conditions to insert oxygen into the C≡C bond. Here, we report an inorganic ligand supported cobalt (III) catalyst, (NH4)3[CoMo6O18(OH)6], which is supported by a central cobalt (III) mononucleus and a ring-shaped pure inorganic ligand composed of six MoVIO6 octahedrons to avoid the disadvantages of expensive and unrecyclable organic ligand catalysts or noble metal catalysts. Under mild conditions, the cobalt (III) catalyst can be used for the hydration of alkynes to ketones. The catalyst is non-toxic, green, and environment friendly. The catalyst can be recycled at least six times with high activity. According to control experiments, a reasonable mechanism is provided.
- Xie, Ya,Wang, Jingjing,Wang, Yunyun,Han, Sheng,Yu, Han
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p. 4985 - 4989
(2021/10/12)
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- Catalyst- and acid-free Markovnikov hydration of alkynes in a sustainable H2O/ethyl lactate system
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An efficient and sustainable protocol for the hydration of alkynes has been developed under metal/acid/catalyst/ligand-free conditions in a water/ethyl lactate mixture. The hydrogen-bond network in the ethyl lactate and water mixture plays a crucial and decisive role in activating the alkynes for hydration to afford the corresponding methyl ketones. This strategy gives the Markovnikov (ketone) addition product selectively over other possible products. The essential role of hydrogen bonding has been confirmed by experimental and theoretical techniques. A probable mechanism has been suggested by various control tests. The efficacy of the method has been further explored for the competent production of value-added α,β-unsaturated carbonyl compounds through the reaction of aldehydes with alkynes as ketonic surrogates. The environmentally benign hydration method takes place under mild conditions, has broad functional-group compatibility, and uses the ethyl lactate/water (1:3) medium as a “green alternative” in the absence of any hazardous, harmful, or expensive substances.
- Dandia, Anshu,Saini, Pratibha,Chithra,Vennapusa, Sivaranjana Reddy,Parewa, Vijay
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- Dual-Metal N-Heterocyclic Carbene Complex (M = Au and Pd)-Functionalized UiO-67 MOF for Alkyne Hydration-Suzuki Coupling Tandem Reaction
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Metal N-heterocyclic carbene complexes (NHC-M) have been recognized as an important class of organometallic catalysts. Herein, we demonstrate that different NHC-M (M = Au and Pd) species can be simultaneously introduced into a single metal organic framework (MOF) by direct assembly of NHC-M-decorated ligands and metal ions under solvothermal conditions. The obtained UiO-67-Au/Pd-NHBC MOF with different organometallic NHC-M species can be a highly reusable dual catalyst to sequentially promote alkyne hydration-Suzuki coupling reaction. The potential utility of this strategy is highlighted by the preparation of many more new multicatalysts of this type for various organic transformations in a sequential way.
- Dong, Ying,Li, Wen-Han,Dong, Yu-Bin
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p. 1818 - 1826
(2021/01/13)
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- Surface Coordination of Multiple Ligands Endows N-Heterocyclic Carbene-Stabilized Gold Nanoclusters with High Robustness and Surface Reactivity
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Deciphering the molecular pictures of the multi-component and non-periodic organic-inorganic interlayer is a grand technical challenge. Here we show that the atomic arrangement of hybrid surface ligands on metal nanoparticles can be precisely quantified through comprehensive characterization of a novel gold cluster, Au44(iPr2-bimy)9(PA)6Br8 (1), which features three types of ligands, namely, carbene (1,3-diisopropylbenzimidazolin-2-ylidene, iPr2-bimy), alkynyl (phenylacetylide, PA), and halide (Br), respectively. The delicately balanced stereochemical effects and bonding capabilities of the three ligands give rise to peculiar geometrical and electronic structures. Remarkably, despite its complex and highly distorted surface structure, cluster 1 exhibits unusual catalytic properties and yet it is highly stable, both chemically and thermally. Moreover, rich reactive sites on the cluster surface raise the prospect of bio-compatibility (as it can be functionalized to yield water-soluble derivatives) and bio-applications.
- Shen, Hui,Xu, Zhen,Hazer, Maryam Sabooni Asre,Wu, Qingyuan,Peng, Jian,Qin, Ruixuan,Malola, Sami,Teo, Boon K.,H?kkinen, Hannu,Zheng, Nanfeng
-
supporting information
p. 3752 - 3758
(2020/12/17)
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- One-Pot Chemoenzymatic Conversion of Alkynes to Chiral Amines
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A one-pot chemoenzymatic sequential cascade for the synthesis of chiral amines from alkynes was developed. In this integrated approach, just ppm amounts of gold catalysts enabled the conversion of alkynes to ketones (>99%) after which a transaminase was used to catalyze the production of biologically valuable chiral amines in a good yield (up to 99%) and enantiomeric excess (>99%). A preparative scale synthesis of (S)-methylbenzylamine and (S)-4-methoxy-methylbenzylamine from its alkyne form gave a yield of 59 and 92%, respectively, withee> 99%.
- Mathew, Sam,Renn, Dominik,Rueping, Magnus,Sagadevan, Arunachalam
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p. 12565 - 12569
(2021/10/21)
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- Chitosan as a chiral ligand and organocatalyst: Preparation conditions-property-catalytic performance relationships
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Chitosan is an abundant and renewable chirality source of natural origin. The effect of the preparation conditions by alkaline hydrolysis of chitin on the properties of chitosan was studied. The materials obtained were used as ligands in the ruthenium-catalysed asymmetric transfer hydrogenation of aromatic prochiral ketones and oxidative kinetic resolution of benzylic alcohols as well as organocatalysts in the Michael addition of isobutyraldehyde to N-substituted maleimides. The degrees of deacetylation of the prepared materials were determined by 1H NMR, FT-IR and UV-vis spectroscopy, the molecular weights by viscosity measurements, their crystallinity by WAXRD, and their morphology by SEM and TEM investigations. The materials were also characterized by Raman spectroscopy. The biopolymers which have molecular weights in a narrow (200-230 kDa) range and appropriate (80-95%) degrees of deacetylation were the most efficient ligands in the enantioselective transfer hydrogenation, whereas in the oxidative kinetic resolution the activity of the complexes and the stereoselectivity increased with the degree of deacetylation. The chirality of the chitosan was sufficient to obtain enantioselection in the Michael addition of isobutyraldehyde to maleimides in the aqueous phase. Interestingly, the biopolymer afforded the opposite enantiomer in excess compared to the monomer, d-glucosamine. In this reaction, good correlation between the degree of deacetylation and the catalytic activity was found. These results are novel steps in the application of this natural, biocompatible and biodegradable polymer in developing environmentally benign methods for the production of optically pure fine chemicals.
- Kolcsár, Vanessza Judit,Sz?ll?si, Gy?rgy
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p. 7652 - 7666
(2021/12/13)
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- Exploration of highly electron-rich manganese complexes in enantioselective oxidation catalysis; A focus on enantioselective benzylic oxidation
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The direct enantioselective hydroxylation of benzylic C-H bonds to form chiral benzylic alcohols represents a challenging transformation. Herein, we report on the exploration of new biologically inspired manganese and iron complexes bearing highly electron-rich aminopyridine ligands containing 4-pyrrolidinopyridine moieties ((S,S)-1, (R,R)-1, 2 and 5) in combination with chiral bis-pyrrolidine and N,N-cyclohexanediamine backbones in enantioselective oxidation catalysis with aqueous H2O2. The current manganese complexes outperform the analogous manganese complexes containing 4-dimethylaminopyridine moieties (3 and 4) in benzylic oxidation reactions in terms of alcohol yield while keeping similar ee values (～60% ee), which is attributed to the higher basicity of the 4-pyrrolidinopyridine group. A detailed investigation of different carboxylic acid additives in enantioselective benzylic oxidation provides new insights into how to rationally enhance enantioselectivities by means of proper tuning of the environment around the catalytic active site, and has resulted in the selection of Boc-l-Tert-leucine as the preferred additive. Using these optimized conditions, manganese complex 2 was shown to be effective in the enantioselective benzylic oxidation of a series of arylalkane substrates with up to 50% alcohol yield and 62% product ee. A final set of experiments also highlights the use of the new 4-pyrrolidinopyridine-based complexes in the asymmetric epoxidation of olefins (up to 98% epoxide yield and >99% ee).
- Klein Gebbink, Robertus J. M.,Li, Fanshi,Lutz, Martin,Masferrer-Rius, Eduard
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p. 7751 - 7763
(2021/12/13)
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- Rapid, chemoselective and mild oxidation protocol for alcohols and ethers with recyclable N-chloro-N-(phenylsulfonyl)benzenesulfonamide
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Chlorine is the 20th most abundant element on the earth compared to bromine, iodine, and fluorine, a sulfonimide reagent, N-chloro-N-(phenylsulfonyl)benzenesulfonamide (NCBSI) was identified as a mild and selective oxidant. Without activation, the reagent was proved to oxidize primary and secondary alcohols as well as their symmetrical and mixed ethers to corresponding aldehydes and ketones. With recoverable PS-TEMPO catalyst, selective oxidation over chlorination of primary and secondary alcohols and their ethers with electron-donating substituents was achieved. The reagent precursor of NCBSI was recovered quantitatively and can be reused for synthesizing NCBSI.
- Badani, Purav,Chaturbhuj, Ganesh,Ganwir, Prerna,Misal, Balu,Palav, Amey
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supporting information
(2021/06/03)
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- o-Quinone methide with overcrowded olefin component as a dehydridation catalyst under aerobic photoirradiation conditions
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Ano-quinone methide (o-QM) featuring an overcrowded olefinic framework is introduced, which exhibits dehydridation activity owing to its enhanced zwitterionic character, particularly through photoexcitation. The characteristics of thiso-QM enable the operation of dehydridative catalysis in the oxidation of benzylic secondary alcohols under aerobic photoirradiation conditions. An experimental analysis and density functional theory calculations provide mechanistic insights; the ground-state zwitterionic intermediate abstracts a hydride and proton simultaneously, and the active oxygen species facilitate catalyst regeneration.
- Uraguchi, Daisuke,Kato, Kohsuke,Ooi, Takashi
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p. 2778 - 2783
(2021/03/14)
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- V2O5@TiO2 Catalyzed Green and Selective Oxidation of Alcohols, Alkylbenzenes and Styrenes to Carbonyls
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The versatile application of different functional groups such as alcohols (1° and 2°), alkyl arenes, and (aryl)olefins to construct carbon-oxygen bond via oxidation is an area of intense research. Here, we report a reusable heterogeneous V2O5@TiO2 catalyzed selective oxidation of various functionalities utilizing different mild and eco-compatible oxidants under greener reaction conditions. The method was successfully applied for the alcohol oxidation, oxidative scission of styrenes, and benzylic C?H oxidation to their corresponding aldehydes and ketones. The utilization of mild and eco-friendly oxidizing reagents such as K2S2O8, H2O2 (30 % aq.), TBHP (70 % aq.), broad substrate scope, gram-scale synthesis, and catalyst recyclability are notable features of the developed protocol.
- Upadhyay, Rahul,Kumar, Shashi,Maurya, Sushil K.
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p. 3594 - 3600
(2021/07/02)
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- Ruthenium(II) Complexes Bearing Schiff Base Ligands for Efficient Acceptorless Dehydrogenation of Secondary Alcohols?
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Four ruthenium(II) complexes 1—4 [RN=CH-(2,4-(tBu)2C6H2O)]RuH(PPh3)2(CO) (R = C6H5, 1; R = 4-MeC6H4, 2; R = 4-ClC6H4, 3; R = 4-BrC6H4, 4) bearing Schiff base ligands were prepared by treating RuHClCO(PPh3)3 with RN=CH-(2,4-(tBu)2C6H2OH (L1—L4) in the presence of triethylamine. Their structures were fully characterized by elemental analysis, IR, NMR spectroscopy and X-ray crystallography. These Ru(II) complexes exhibit high catalytic performance and good functional-group compatibility in the acceptorless dehydrogenation of secondary alcohols, affording the corresponding ketones in 82%—94% yields.
- Dong, Qing,Feng, Qi,Han, Zhangang,Hao, Zhiqiang,Lin, Jin,Liu, Kang,Lu, Guo-Liang,Ma, Dongzhu
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p. 121 - 128
(2020/12/25)
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- Visible light mediated selective oxidation of alcohols and oxidative dehydrogenation of N-heterocycles using scalable and reusable La-doped NiWO4nanoparticles
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Visible light-mediated selective and efficient oxidation of various primary/secondary benzyl alcohols to aldehydes/ketones and oxidative dehydrogenation (ODH) of partially saturated heterocycles using a scalable and reusable heterogeneous photoredox catalyst in aqueous medium are described. A systematic study led to a selective synthesis of aldehydes under an argon atmosphere while the ODH of partially saturated heterocycles under an oxygen atmosphere resulted in very good to excellent yields. The methodology is atom economical and exhibits excellent tolerance towards various functional groups, and broad substrate scope. Furthermore, a one-pot procedure was developed for the sequential oxidation of benzyl alcohols and heteroaryl carbinols followed by the Pictet-Spengler cyclization and then aromatization to obtain the β-carbolines in high isolated yields. This methodology was found to be suitable for scale up and reusability. To the best of our knowledge, this is the first report on the oxidation of structurally diverse aryl carbinols and ODH of partially saturated N-heterocycles using a recyclable and heterogeneous photoredox catalyst under environmentally friendly conditions.
- Abinaya, R.,Balasubramaniam, K. K.,Baskar, B.,Divya, P.,Mani Rahulan, K.,Rahman, Abdul,Sridhar, R.,Srinath, S.
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p. 5990 - 6007
(2021/08/24)
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- Cobalt-Catalyzed Aerobic Oxidative Cleavage of Alkyl Aldehydes: Synthesis of Ketones, Esters, Amides, and α-Ketoamides
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A widely applicable approach was developed to synthesize ketones, esters, amides via the oxidative C?C bond cleavage of readily available alkyl aldehydes. Green and abundant molecular oxygen (O2) was used as the oxidant, and base metals (cobalt and copper) were used as the catalysts. This strategy can be extended to the one-pot synthesis of ketones from primary alcohols and α-ketoamides from aldehydes.
- Li, Tingting,Hammond, Gerald B.,Xu, Bo
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p. 9737 - 9741
(2021/05/31)
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- Iron-Catalyzed Wacker-type Oxidation of Olefins at Room Temperature with 1,3-Diketones or Neocuproine as Ligands**
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Herein, we describe a convenient and general method for the oxidation of olefins to ketones using either tris(dibenzoylmethanato)iron(III) [Fe(dbm)3] or a combination of iron(II) chloride and neocuproine (2,9-dimethyl-1,10-phenanthroline) as catalysts and phenylsilane (PhSiH3) as additive. All reactions proceed efficiently at room temperature using air as sole oxidant. This transformation has been applied to a variety of substrates, is operationally simple, proceeds under mild reaction conditions, and shows a high functional-group tolerance. The ketones are formed smoothly in up to 97 % yield and with 100 % regioselectivity, while the corresponding alcohols were observed as by-products. Labeling experiments showed that an incorporated hydrogen atom originates from the phenylsilane. The oxygen atom of the ketone as well as of the alcohol derives from the ambient atmosphere.
- Kataeva, Olga,Kn?lker, Hans-Joachim,Linke, Philipp,Puls, Florian
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supporting information
p. 14083 - 14090
(2021/05/24)
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- Linkage engineering mediated carriers transfer and surface reaction over carbon nitride for enhanced photocatalytic activity
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Rational tailoring of the atomic structure of photocatalysts with multiple functions to enhance the carrier transfer efficiency and surface activation of carbon nitride (C3N4) is promising and a challenge. Here, we make the first report of a facile strategy to construct amphiphilic carbon and C-O-C chain linked terminal melem units in functional carbon nitride (COCN)viacopolymerizing formaldehyde with melem. By integrating the amphiphilic carrier bridge of carbon and C-O-C chains into the framework, the photogenerated carrier mobility and activated species (superoxide radicals, singlet oxygen) as well as surface interaction are significantly improved. Consequently, the optimal tailoring of C3N4attains superior photocatalytic activity for hydrogen production (34.9 μmol h?1) and selective oxidation of sulfide to sulfoxide using air (nearly 100% conversion and selectivity after 3 h of illumination), which is about 7 times higher than that of pristine C3N4. This study provides deep insight into and strategies for the atomic tailoring of carrier transfer and surface reaction over organic-based photocatalysts.
- Chen, Peng,Li, Gen,Liu, Fei,Wang, Qian,Wang, Qiuchen,Yang, Shilian,Yin, Shuang-Feng,Zhao, Tianxiang
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p. 21732 - 21740
(2021/10/14)
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- Catalytic Aerobic Oxidation of Alkenes with Ferric Boroperoxo Porphyrin Complex; Reduction of Oxygen by Iron Porphyrin
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We herein describe the development of a mild and selective catalytic aerobic oxidation process of olefins. This catalytic aerobic oxidation reaction was designed based on experimental and spectroscopic evidence assessing the reduction of atmospheric oxygen using a ferric porphyrin complex and pinacolborane to form a ferric boroperoxo porphyrin complex as an oxidizing species. The ferric boroperoxo porphyrin complex can be utilized as an in-situ generated intermediate in the catalytic aerobic oxidation of alkenes under ambient conditions to form oxidation products that differ from those obtained using previously reported ferric porphyrin catalysis. Moreover, the mild reaction conditions allow chemoselective oxidation to be achieved.
- Kimura, Kento,Kurahashi, Takuya,Matsubara, Seijiro,Murano, Shunpei
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supporting information
p. 2493 - 2497
(2021/12/29)
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- Direct bromodeboronation of arylboronic acids with CuBr2 in water
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An efficient and practical method has been developed for the preparation of aryl bromides via the direct bromodeboronation of arylboronic acids with CuBr2 in water. This strategy provides several advantages, such as being ligand-free, base-free, high yielding, and functional group tolerant.
- Tang, Yan-Ling,Xia, Xian-Song,Gao, Jin-Chun,Li, Min-Xin,Mao, Ze-Wei
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supporting information
(2021/01/05)
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- Poly-N-bromosulfonamide-melamine as a novel brominating reagent for regioselective ipso-bromination of arylboronic acids
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A practical synthetic method for the synthesis of aryl bromide was developed through regioselective bromination of boronic acid in the presence of poly-N-bromosulfonamide-melamine (PBBSM). In this regard, a novel heterogeneous support, cross-linked poly sulfonamide-melamine, has been successfully synthesized to stabilize bromine with high surface functional group density (6.6?mmol Br+/g). The prepared reagent is a novel brominating reagent that combines the effective functions of N-bromosulfonamide, N-bromosulfonamide-melamine, and melamine groups. The structure of PBBSM was characterized using XRD, FT–IR, 1H NMR, TGA, FE-SEM, EDX, and TGA analysis. Graphic abstract: [Figure not available: see fulltext.]
- Alavinia, Sedigheh,Ghorbani-Vaghei, Ramin
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p. 1269 - 1276
(2021/08/27)
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- An efficient and practical aerobic oxidation of benzylic methylenes by recyclable: N -hydroxyimide
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An efficient and practical benzylic aerobic oxidation catalyzed by cheap and simple N-hydroxyimide organocatalyst has been achieved with high yields and broad substrate scope. The organocatalyst used can be recycled and reused by simple workup and only minute amount (1 mol% in most cases) of simple iron salt is used as promoter. Phenyl substrates with mild and strong electron-withdrawing group could also be oxygenated in high yields as well as other benzylic methylenes. Influence of substituents, gram-scale application, catalysts decay and general mechanism of this methodology has also been discussed. This journal is
- Wang, Jian,Zhang, Cheng,Ye, Xiao-Qing,Du, Wenting,Zeng, Shenxin,Xu, Jian-Hong,Yin, Hong
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p. 3003 - 3011
(2021/01/28)
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- Visible-light photocatalytic selective oxidation of C(sp3)-H bonds by anion-cation dual-metal-site nanoscale localized carbon nitride
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Selective oxidation of C(sp3)-H bonds to carbonyl groups by abstracting H with a photoinduced highly active oxygen radical is an effective method used to give high value products. Here, we report a heterogeneous photocatalytic alkanes C-H bonds oxidation method under the irradiation of visible light (λ= 425 nm) at ambient temperature using an anion-cation dual-metal-site modulated carbon nitride. The optimized cation (C) of Fe3+or Ni2+, with an anion (A) of phosphotungstate (PW123?) constitutes the nanoscale dual-metal-site (DMS). With a Fe-PW12dual-metal-site as a model (FePW), we demonstrate a A-C DMS nanoscale localized carbon nitride (A-C/g-C3N4) exhibiting a highly enhanced photocatalytic activity with a high product yield (86% conversion), selectivity (up to 99%), and a wide functional group tolerance (52 examples). The carbon nitride performs the roles of both the visible light response, and improves the selectivity for the oxidation of C(sp3)-H bonds to carbonyl groups, along with the function of A-C DMS in promoting product yield. Mechanistic studies indicate that this reaction follows a radical pathway catalyzed by a photogenerated electron and hole on A-C/g-C3N4that is mediated by thetBuO˙ andtBuOO˙ radicals. Notably, a 10 g scale reaction was successfully achieved for alkane photocatalytic oxidation to the corresponding product with a good yield (80% conversion), and high selectivity (95%) under natural sunlight at ambient temperature. In addition, this A-C/g-C3N4photocatalyst is highly robust and can be reused at least six times and the activity is maintained.
- Duan, Limei,Li, Peihe,Li, Wanfei,Liu, Jinghai,Liu, Ying,Liu, Zhifei,Lu, Ye,Sarina, Sarina,Wang, Jinghui,Wang, Yin,Wang, Yingying,Zhu, Huaiyong
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p. 4429 - 4438
(2021/07/12)
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- Efficient Aliphatic C-H Oxidation and C═C Epoxidation Catalyzed by Porous Organic Polymer-Supported Single-Site Manganese Catalysts
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Bioinspired manganese complexes have emerged over recent decades as attractive catalysts for a number of selective oxidation reactions. However, these catalysts still suffer from oxidative degradation. In the present study, we prepared a series of porous Mn-N4 catalysts in which the catalytic units are embedded in the skeleton of porous organic polymers (POPs). These POP-based manganese catalysts demonstrated high reactivity in the oxidation of aliphatic C-H bonds and the asymmetric epoxidation of olefins. Furthermore, these catalysts could be readily recycled and reused due to their heterogeneous nature. Morphological characterization revealed that the Mn-N4 complex was individually distributed over a porous polymer network. Remarkably, the nature of the single-site catalyst prevented oxidative degradation during the reaction. The present work has thus developed a successful approach for bioinspired single-site manganese catalysts in which the oxidation reaction is confined to a specific channel in an enzyme-like mode.
- Wang, Bingyang,Lin, Jin,Sun, Qiangsheng,Xia, Chungu,Sun, Wei
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p. 10964 - 10973
(2021/09/08)
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- Metal- And additive-free C-H oxygenation of alkylarenes by visible-light photoredox catalysis
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A metal- and additive-free methodology for the highly selective, photocatalyzed C-H oxygenation of alkylarenes under air to the corresponding carbonyls is presented. The process is catalyzed by an imide-acridinium that forms an extremely strong photooxidant upon visible light irradiation, which is able to activate inert alkylarenes such as toluene. Hence, this is an easy to perform, sustainable and environmentally friendly oxidation that provides valuable carbonyls from abundant, readily available compounds.
- García Manche?o, Olga,Kuhlmann, Jan H.,Pérez-Aguilar, María Carmen,Piekarski, Dariusz G.,Uygur, Mustafa
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supporting information
p. 3392 - 3399
(2021/05/21)
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- Selective electrochemical oxidation of aromatic hydrocarbons and preparation of mono/multi-carbonyl compounds
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A selective electrochemical oxidation was developed under mild condition. Various mono-carbonyl and multi-carbonyl compounds can be prepared from different aromatic hydrocarbons with moderate to excellent yield and selectivity by virtue of this electrochemical oxidation. The produced carbonyl compounds can be further transformed into α-ketoamides, homoallylic alcohols and oximes in a one-pot reaction. In particular, a series of α-ketoamides were prepared in a one-pot continuous electrolysis. Mechanistic studies showed that 2,2,2-trifluoroethan-1-ol (TFE) can interact with catalyst species and generate the corresponding hydrogen-bonding complex to enhance the electrochemical oxidation performance. [Figure not available: see fulltext.]
- Li, Zhibin,Zhang, Yan,Li, Kuiliang,Zhou, Zhenghong,Zha, Zhenggen,Wang, Zhiyong
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p. 2134 - 2141
(2021/09/29)
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- Photo-tunable oxidation of toluene and its derivatives catalyzed by TBATB
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In this report, tetrabutylammonium tribromide (TBATB) was introduced as an efficient visible light active catalyst to carry out the aerobic oxidation of toluene, its derivatives, and some of methyl arenes to benzaldehydes, benzoic acids and ketones in good to high yields. All the oxidation reactions were performed under mild conditions using oxygen as a green oxidant, a catalytic amount of TBATB under blue (460 nm), royal blue (430 nm), and violet LED (400 nm) irradiation. It was found that the reactions selectivity was significantly affected by changing the solvent (from CH3CN to EtOAc) and LED wavelength (from blue to violet). In the following, our mechanistic studies revealed that the visible light oxidation of toluenes and methyl arenes over TBATB could be following a benzyl peroxy radical intermediate.
- Mardani, Atefeh,Kazemi, Foad,Kaboudin, Babak
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- Ferric ion concentration-controlled aerobic photo-oxidation of benzylic C–H bond with high selectivity and conversion
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A Fe(III)-promoted highly selective photo-oxidation of benzylic C–H bond delivering relative carbonyl products is reported. By altering the concentration of ferric salt, methylarenes can be selectively oxidized under UV irradiation to furnish aromatic aldehydes or acids, respectively. By this protocol, the oxidation of ethylarenes provides the corresponding acetophenones. The reaction is inferred to involve divergent pathways in different concentrations of catalyst for the alternative selectivity between aldehydes and aicds. The reusable catalyst, high conversion and selectivity make this oxidation a green and economic protocol for the synthesis of aromatic carbonyl compounds.
- Bu, Hongzhong,Gu, Jiefan,Li, Yufeng,Ma, Hongfei,Wan, Yuting,Wu, Zheng-Guang,Zhang, Weijian,Zhou, Ying'ao,Zhu, Hongjun
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- HCl-Catalyzed Aerobic Oxidation of Alkylarenes to Carbonyls
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The construction of C?O bonds through C?H bond functionalization remains fundamentally challenging. Here, a practical chlorine radical-mediated aerobic oxidation of alkylarenes to carbonyls was developed. This protocol employed commercially available HCl as a hydrogen atom transfer (HAT) reagent and air as a sustainable oxidant. In addition, this process exhibited excellent functional group tolerance and a broad substrate scope without the requirement for external metal and oxidants. The mechanistic hypothesis was supported by radical trapping, 18O labeling, and control experiments.
- Ding, Ling,Liu, Yuxiu,Niu, Kaikai,Shi, Xiaodi,Song, Hongjian,Wang, Qingmin
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- Visible-Light-Driven Selective Air-Oxygenation of C?H Bond via CeCl3 Catalysis in Water
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Visible-light-induced C?H aerobic oxidation is an important chemical transformation that can be applied for the synthesis of aromatic ketones. High-cost catalysts and toxic solvents were generally needed in the present methodologies. Here, an efficient aqueous C?H aerobic oxidation protocol was reported. Through CeCl3-mediated photocatalysis, a series of aromatic ketones were produced in moderate to excellent yields. With air as the oxidant, this reaction could be performed under mild conditions in water and demonstrated high activity and functional group tolerance. This method is economical, highly efficient, and environmentally friendly, and it will provide inspiration for the development of aqueous photochemical synthesis reactions.
- Xie, Pan,Xue, Cheng,Shi, Sanshan,Du, Dongdong
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p. 2689 - 2693
(2021/05/07)
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- Selective Oxidation of Benzylic sp3C-H Bonds using Molecular Oxygen in a Continuous-Flow Microreactor
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Selective aerobic oxidation of benzylic sp3 C-H bonds to generate the corresponding ketones was achieved under continuous-flow conditions. The catalysts N-hydroxyphthalimide (NHPI) and tert-butyl nitrite (TBN) as the precursor of the radical under aerobic conditions motivated this process. Flow microreactors operating under optimized conditions enabled this oxidation with higher efficiency and a shortened reaction time of 54 s (total time was 10 min), which was improved 466 times compared with the batch parallel reaction (7.0 h). Notably, the catalyst and solvent recycling (92.6 and 94.5%) and scale-up experiments (0.87 g h-1 in 28 h) demonstrated the practicability of the protocol. The high product selectivity and functional group tolerance of the process allowed the production of ketones in yields of 41.2 to 90.3%. To reveal the versatility and applicability of this protocol, the late-stage modification of an antiepileptic drug to obtain oxcarbazepine was further conducted.
- Ma, Cunfei,Meng, Qingwei,Tang, Xiaofei,Yu, Zongyi,Yun, Lei,Zhao, Jingnan
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p. 1612 - 1618
(2021/07/21)
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- Selective Electrochemical Oxygenation of Alkylarenes to Carbonyls
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An efficient electrochemical method for benzylic C(sp3)-H bond oxidation has been developed. A variety of methylarenes, methylheteroarenes, and benzylic (hetero)methylenes could be converted into the desired aryl aldehydes and aryl ketones in moderate to excellent yields in an undivided cell, using O2 as the oxygen source and lutidinium perchlorate as an electrolyte. On the basis of cyclic voltammetry studies, 18O labeling experiments, and radical trapping experiments, a possible single-electron transfer mechanism has been proposed for the electrooxidation reaction.
- Li, Xue,Bai, Fang,Liu, Chaogan,Ma, Xiaowei,Gu, Chengzhi,Dai, Bin
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supporting information
p. 7445 - 7449
(2021/10/02)
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- Cu2O-CuO/Chitosan Composites as Heterogeneous Catalysts for Benzylic C?H Oxidation at Room Temperature
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Recently, in catalysis, chitosan has been exploited as a macrochelating ligand for metal active species due to the presence of various functional groups in its structure. Moreover, copper-based catalysts are classified as one of the most environmentally friendly catalytic systems and their use for the oxidation of alkylarene has not been established much. Therefore, in this work, the hydrothermal synthesis of copper oxide-chitosan composites as heterogeneous catalysts for the benzylic C?H oxidation of alkylarene was investigated. Characterization results reveal mixed phases of CuO and Cu2O, inferring the ability of chitosan to act as a reducing sugar under the hydrothermal condition. The pre-existing interaction between copper species and chitosan as well as the co-existence of the Cu2O and CuO structures give rise to the efficient performance of the catalysts. The synthesized composites exhibit high activity for the oxidation of fluorene to 9-fluorenone at room temperature and small catalyst loading (1 mol % of Cu, >90 % conversion and 100 % selectivity). Superior TOF was observed, and a good scope of substrates can be converted to corresponding ketones in 48–97 % yields with these copper oxide-chitosan catalysts. In addition, the catalysts can be used for up to nine cycles without significant decrease of the activity.
- Kanarat, Jurin,Bunchuay, Thanthapatra,Klysubun, Wantana,Tantirungrotechai, Jonggol
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p. 4833 - 4840
(2021/10/07)
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- Efficient aerobic oxidation of ethylbenzene accelerated by cu species in hydrotalcite
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The simply prepared CuMgAl hydrotalcite (CuMgAl-LDH) has been developed as an efficient catalyst for the aerobic oxidation of ethylbenzene to acetophenone in the presence of N-Hydroxyphthalimide (NHPI). Various alkyl arenes could be tolerated under the selected reaction conditions. The kinetic study showed that the oxidation of ethylbenzene is a first-order reaction over CuMgAl-LDH. The mechanism study indicated that CuMgAl-LDH could accelerate not only the conversion of ethylbenzene, but also the transformation of the alcohol intermediate to ketone. The positive effect of surface basicity of the catalyst on the reaction has been observed in the aerobic oxidation of the ethylbenzene.
- Dai, Xuan,Jiang, Ou,Li, Xingyan,Peng, Xinhua,Tang, Shuangling,Zheng, Xuegen
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- Oxidative Cleavage of Alkenes by O2with a Non-Heme Manganese Catalyst
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The oxidative cleavage of C═C double bonds with molecular oxygen to produce carbonyl compounds is an important transformation in chemical and pharmaceutical synthesis. In nature, enzymes containing the first-row transition metals, particularly heme and non-heme iron-dependent enzymes, readily activate O2 and oxidatively cleave C═C bonds with exquisite precision under ambient conditions. The reaction remains challenging for synthetic chemists, however. There are only a small number of known synthetic metal catalysts that allow for the oxidative cleavage of alkenes at an atmospheric pressure of O2, with very few known to catalyze the cleavage of nonactivated alkenes. In this work, we describe a light-driven, Mn-catalyzed protocol for the selective oxidation of alkenes to carbonyls under 1 atm of O2. For the first time, aromatic as well as various nonactivated aliphatic alkenes could be oxidized to afford ketones and aldehydes under clean, mild conditions with a first row, biorelevant metal catalyst. Moreover, the protocol shows a very good functional group tolerance. Mechanistic investigation suggests that Mn-oxo species, including an asymmetric, mixed-valent bis(μ-oxo)-Mn(III,IV) complex, are involved in the oxidation, and the solvent methanol participates in O2 activation that leads to the formation of the oxo species.
- Bennett, Elliot L.,Brookfield, Adam,Guan, Renpeng,Huang, Zhiliang,Mcinnes, Eric J. L.,Robertson, Craig M.,Shanmugam, Muralidharan,Xiao, Jianliang
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supporting information
p. 10005 - 10013
(2021/07/19)
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- Method for preparing carbonyl compound through oxidative cleavage of visible light excitation aqueous solution quantum dot catalytic olefin compound
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The invention provides a method for preparing carbonyl compounds through oxidative cleavage of a visible light excitation aqueous solution quantum dot catalytic olefin compound. Belong to photocatalysis synthesis technical field. To the method, an aqueous solution quantum dot is used as a photocatalyst, and an aqueous solution quantum dot activated molecular oxygen catalytic oxidation aromatic alkene compound is excited by visible light to be cracked to prepare a carbonyl compound. Low-loading capacity is used, a simple aqueous solution quantum dot is used as a catalyst, the yield of the carbonyl compound is high, TON more than ten millions are obtained. The reaction conditions are mild, water serves as a main solvent for the reaction, and the carbonyl compound can be obtained by catalytic olefin compound oxidation cracking without addition of a cocatalyst or the like. The method is simple to operate, wide in substrate range and low in cost.
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Paragraph 0033
(2021/11/10)
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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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- Decatungstate-mediated solar photooxidative cleavage of CC bonds using air as an oxidant in water
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With the increasing attention for green chemistry and sustainable development, there has been much interest in searching for greener methods and sources in organic synthesis. However, toxic additives or solvents are inevitably involved in most organic transformations. Herein, we first report the combination of direct utilization of solar energy, air as the oxidant and water as the solvent for the selective cleavage of CC double bonds in aryl olefins. Various α-methyl styrenes, diaryl alkenes as well as terminal styrenes are well tolerated in this green and sustainable strategy and furnished the desired carbonyl products in satisfactory yields. Like heterogeneous catalysis, this homogeneous catalytic system could also be reused and it retains good activity even after repeating three times. Mechanism investigations indicated that both O2- and 1O2 were involved in the reaction. Based on these results, two possible mechanisms, including the electron transfer pathway and the energy transfer pathway, were proposed.
- Du, Dongdong,Luo, Junfei,Shi, Sanshan,Xie, Pan,Xue, Cheng
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p. 5936 - 5943
(2021/08/23)
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- Photo-induced oxidative cleavage of C-C double bonds for the synthesis of biaryl methanoneviaCeCl3catalysis
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A Ce-catalyzed strategy is developed to produce biaryl methanonesviaphotooxidative cleavage of C-C double bonds at room temperature. This reaction is performed under air and demonstrates high activity as well as functional group tolerance. A synergistic Ce/ROH catalytic mechanism is also proposed based on the experimental observations. This protocol should be the first successful Ce-catalyzed photooxidation reaction of olefins with air as the oxidant, which would provide inspiration for the development of novel Ce-catalyzed photochemical synthesis processes.
- Xie, Pan,Xue, Cheng,Du, Dongdong,Shi, SanShan
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supporting information
p. 6781 - 6785
(2021/08/20)
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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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- Promoting charge separation in donor-acceptor conjugated microporous polymers: Via cyanation for the photocatalytic reductive dehalogenation of chlorides
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Conjugated microporous polymers (CMPs) have emerged as promising heterogeneous photocatalysts for organic transformations owing to their structural designability and functional versatility. However, limited by the insufficient separation of the photo-generated excitons, their photocatalytic efficiency falls far short of expectations. Herein, we demonstrate a cyanation strategy to promote charge carrier separation in CMPs by selectively incorporating carbazole and cyano groups as electron-donating and electron-withdrawing units, respectively. The resulting CMPs feature π-extended donor (D)-acceptor (A) conjugation structures endowing them with distinct semiconducting properties, in which the efficient charge separation and transfer and wide visible-light absorption are facilitated. Compared to the cyano-free counterpart, the cyano-functionalized CMPs showed superior photocatalytic efficiency as exemplified by photocatalytic reductive dehalogenation of chlorides. More prominently, full recyclability of the designed CMPs as well as catalytic activity for at least ten runs without the loss of catalytic performance in photocatalytic reductive dehalogenation of chlorides demonstrated their robustness and sustainability. This journal is
- Deng, Jiyong,Fang, Zhengjun,Lan, Donghui,Liao, Yunfeng,Liu, Qingquan,Zhang, Weijie,Zhou, Xiang
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p. 7151 - 7159
(2021/11/17)
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- An Artificial Light-Harvesting System with Tunable Fluorescence Color in Aqueous Sodium Dodecyl Sulfonate Micellar Systems for Photochemical Catalysis
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In the present work, an artificial light-harvesting system with fluorescence resonance energy transfer (FRET) is successfully fabricated in aqueous sodium dodecyl sulfonate (SDS) micellar systems. Since the tight and orderly arrangement of dodecyl in the SDS micelles is hydrophobic, tetra-(4-pyridylphenyl)ethylene (4PyTPE) can be easily encapsulated into the hydrophobic layer of SDS micelles through noncovalent interaction, which exhibits aggregation-induced emission (AIE) phenomenon and can be used as energy donor. By using amphoteric sulforhodamine 101 (SR101) fluorescent dye attached to the negatively charged surface of SDS micelles through electrostatic interaction as energy acceptor, the light-harvesting FRET process can be efficiently simulated. Through the steady-state emission spectra analysis in the micelle-mediated energy transfer from 4PyTPE to SR101, the fluorescence emission can be tuned and white light emission with CIE coordinates of (0.31, 0.29) can be successfully achieved by tuning the donor/acceptor ratio. More importantly, to better mimic natural photosynthesis, the SDS micelles with 4PyTPE and SR101 FRET system showed enhanced catalytic activity in photochemical catalysis for dehalogenation of α-bromoacetophenone in aqueous solution and the photocatalytic reaction could be extended to gram levels.
- Li, Xinglong,Wang, Ying,Song, Ao,Zhang, Minghui,Chen, Mengning,Jiang, Man,Yu, Shengsheng,Wang, Rongzhou,Xing, Lingbao
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supporting information
p. 2725 - 2730
(2021/08/03)
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- Interfacially synthesized 2D COF thin film photocatalyst: efficient photocatalyst for solar formic acid production from CO2and fine chemical synthesis
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The targeted synthesis of an efficient, visible light active, recyclable, freestanding covalent organic framework thin film photocatalyst for multi-faceted photocatalysis is the essence of the proposed work. A simple, scalable, reagent free synthesis of a thin film at the interface of 5,10,15,20-tetra-(4-aminophenyl)porphyrin, 2-vinylbenzene-1,4-dicarbaldehyde in nitrobenzene and aqueous glyoxal affords centimetre sized continuous 2D thin film with substantial stability, flexibility and efficient visible light activity. Strikingly different from the regular imine based COF, the incorporation of the glyoxal unit as a modulator helps in band gap tuning and induces flexibility within the thin film. An interplay between time and concentration helps in achieving a thin film photocatalyst with efficient photocatalytic activity for 1,4-NADH regeneration and selective formic acid formation from CO2. The optimum band edge position of the thin film photocatalyst also enables solar fine chemical synthesisviareductive dehalogenation under visible light illumination with excellent recyclability. The present work gives insight into visible light active thin film formation en route to metal-free sustainable photocatalysis.
- Yadav, Dolly,Kumar, Abhishek,Kim, Jae Young,Park, No-Joong,Baeg, Jin-Ook
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supporting information
p. 9573 - 9580
(2021/04/26)
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- The Reactivity of α-Fluoroketones with PLP Dependent Enzymes: Transaminases as Hydrodefluorinases
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A chemical method for the treatment of harmful halogenated compounds that has recently become of interest is the reductive dehalogenation of carbon-halogen bonds. In the case of a fluorine atom, this process is called hydrodefluorination. While many transition metal-based approaches now exist to reductively defluorinate aromatic fluoroarenes, the cleavage of C?F bonds in aliphatic compounds is not so well-developed. Here we propose a biocatalytic approach exploiting a promiscuous activity exhibited by transaminases (TAs). Hence, a series of α-fluoroketones have been defluorinated with excellent conversions using Chromobacterium violaceum and Arthrobacter sp. TAs under mild conditions and in aqueous medium, using a stoichiometric amount of an amine (e. g. 2-propylamine) as reagent and formally releasing its oxidized form (e. g. acetone), with ammonia and hydrogen fluoride as by-products. It is also demonstrated that this process can be performed in a regio- or stereoselective fashion.
- García-Ramos, Marina,Cuetos, Aníbal,Kroutil, Wolfgang,Grogan, Gideon,Lavandera, Iván
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p. 3967 - 3972
(2021/08/09)
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- Lewis Acidic Boranes, Lewis Bases, and Equilibrium Constants: A Reliable Scaffold for a Quantitative Lewis Acidity/Basicity Scale
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A quantitative Lewis acidity/basicity scale toward boron-centered Lewis acids has been developed based on a set of 90 experimental equilibrium constants for the reactions of triarylboranes with various O-, N-, S-, and P-centered Lewis bases in dichloromethane at 20 °C. Analysis with the linear free energy relationship log KB=LAB+LBB allows equilibrium constants, KB, to be calculated for any type of borane/Lewis base combination through the sum of two descriptors, one for Lewis acidity (LAB) and one for Lewis basicity (LBB). The resulting Lewis acidity/basicity scale is independent of fixed reference acids/bases and valid for various types of trivalent boron-centered Lewis acids. It is demonstrated that the newly developed Lewis acidity/basicity scale is easily extendable through linear relationships with quantum-chemically calculated or common physical–organic descriptors and known thermodynamic data (ΔH (Formula presented.)). Furthermore, this experimental platform can be utilized for the rational development of borane-catalyzed reactions.
- Mayer, Robert J.,Hampel, Nathalie,Ofial, Armin R.
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supporting information
p. 4070 - 4080
(2021/01/29)
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