- Aqueous aerobic oxidation of alkyl arenes and alcohols catalyzed by copper(ii) phthalocyanine supported on three-dimensional nitrogen-doped graphene at room temperature
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Copper(ii) tetrasulfophthalocyanine supported on three-dimensional nitrogen-doped graphene-based frameworks was synthesized and introduced as a bifunctional catalyst for selective aerobic oxidation of alkyl arenes and alcohols to the corresponding carbonyl compounds. The ease of catalyst separation, high turnover, low catalyst loading and recyclability could potentially render it applicable in industrial setting. This journal is the Partner Organisations 2014.
- Mahyari, Mojtaba,Laeini, Mohammad Sadegh,Shaabani, Ahmad
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- Gold nanoparticles supported on three-dimensional nitrogen-doped graphene: An efficient catalyst for selective aerobic oxidation of hydrocarbons under mild conditions
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The development of efficient and selective aerobic oxidation of alkylarenes to form more functional compounds by heterogeneously catalysed routes still presents a great challenge in the fine chemical industry and is a major research topic. In this work, gold nanoparticles supported on three-dimensional nitrogen-doped graphene-based frameworks (Au NPs@3D-(N)GFs) were successfully synthesized and found to have an impressive performance as bifunctional catalysts (nitrogen dopant as base and gold nanoparticles as active site) in the controlled oxidation of alkylarenes. The catalyst was found to be a simple bench top, stable, recyclable and selective catalytic system for the aerobic oxidation of various types of alkylarenes into their corresponding ketones at room temperature under environmentally friendly conditions with good yields and high selectivity.
- Mahyari, Mojtaba,Laeini, Mohammad Sadegh,Shaabani, Ahmad,Kazerooni, Hanif
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- Effect of basicity on the catalytic properties of Ni-containing hydrotalcites in the aerobic oxidation of alcohol
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A series of Ni-containing hydrotalcites with different basicities have been prepared by introducing different Mg2+ contents, and characterized by XRD, SEM, TG-DTG, ICP, FTIR, Hammett analysis, DR UV–vis, XPS, etc. The effects of basicity on the catalytic performance in the selective aerobic oxidation of alcohols and the mechanism have been studied. The results showed that substituting Ni2+ in the structure by Mg2+ ions significantly increased the surface basicity of the catalysts. The surface basicity of Ni-containing hydrotalcites could accelerate the first acid-base reaction step in the oxidation and improve the catalytic activity. Varied alcohols were tested and discussed in the reaction system to verify the effect, and the results indicated that the activity of α-C[sbnd]H bond is the key factor for the benzyl alcohol derivatives, while the first base-acid reaction step may be more important for aliphatic alcohols. The comparison results between the hydrotalcites and the calcined samples showed that the type of basic site have significantly influence on the catalytic activity, and only the Br?nsted OH basic sites accelerate the oxidation. In addition, a probable mechanism for the reaction was postulated based on catalytic results, Hammett and a series of controlled experiments. The main factors affecting the catalytic oxidation of varied alcohols using molecular oxygen as the ultimate oxidant have been discussed, which may be helpful in designing more efficient catalyst.
- Zhou, Weiyou,Tao, Qianyun,Pan, Jiugao,Liu, Jie,Qian, Junfeng,He, Mingyang,Chen, Qun
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- Green oxidation of alkylaromatics using molecular oxygen over mesoporous manganese silicate catalysts
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A very green catalytic method has been introduced for the synthesis of alkylaromatic ketones by solvent-free benzylic oxidation of alkylaromatics with molecular oxygen (O2) over hexagonally mesostructured MnSBA-15 catalysts synthesized with a variety of manganese (Mn) contents using a pH-adjusting direct hydrothermal (pH-aDH) method. For example, the solvent-free oxidation of ethylbenzene (EB) over different mesoporous MnSBA-15 catalysts and uniform pore sized MnMCM-41(31) prepared by an alkaline hydrothermal method has been systematically evaluated. Washed MnSBA-15(4) (W-MnSBA-15(4)) or green mesoporous MnSBA-15(4) obtained after the removal of the non-framework octahedral Mn2O3 species deposited on the active surface of MnSBA-15(4) using a promising chemical treatment method is used for this reaction to evaluate its catalytic activity. Meanwhile the recyclability and hot-filtration experiments for this reaction have been also studied. The catalytic activities obtained from the above catalytic results prove that the W-MnSBA-15(4) has higher EB conversion and APO selectivity than the other mesoporous catalysts used in this reaction. Therefore, in order to find the optimal reaction parameters for this reaction, various reaction parameters with W-MnSBA-15(4) have been thoroughly evaluated. Using W-MnSBA-15(4), the catalytic results obtained with different oxidants used in this reaction have also been discussed clearly. The catalytic results of solvent-free benzylic oxidations with W-MnSBA-15(4) conducted with different alkylaromatic molecules have been obviously discussed. All the mesoporous catalysts used in this reaction have been characterized using several instrumental techniques to confirm them as the standard mesoporous catalysts. The plausible reaction mechanism for the solvent-free oxidation of EB has been successfully reported based on the characterization results of the catalyst and catalytic results. The ESR and UV-vis DRS results of the W-MnSBA-15 catalyst used in these reactions corroborate that the disordered octahedral divalent (Mn2+) and tetrahedral trivalent (Mn3+)-species have been successfully incorporated on the silica surface of the catalysts. Based on the catalytic results, it is noteworthy to observe that mesoporous W-MnSBA-15(4) is a highly active, green and promising heterogeneous catalyst for the selective synthesis of alkylaromatic ketones, since the catalyst produces the best catalytic activity among the other mesoporous Mn silicate catalysts. This journal is
- Assiri, Mohammed A.,Bhaumik, Asim,Ha, Chang-Sik,Selvaraj, Manickam,Subrahmanyam, Ch.
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- Diastereoselective reductive aldol reaction of enones to ketones catalyzed by halogenotin hydride
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It's in the tin: The reductive aldol reaction of enones has been established by the Bu2SnClH (cat.)/Ph2SiH2/MeOH system (see scheme). The reaction of enones with α-ketoesters or α-alkoxyketones is highly diastereoselective through a chelation-controlled mechanism. Copyright
- Shibata, Ikuya,Tsunoi, Shinji,Sakabe, Kumiko,Miyamoto, Shinji,Kato, Hirofumi,Nakajima, Hideto,Yasuda, Makoto,Baba, Akio
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- Oxidation of alcohols with hydrogen peroxide catalyzed by a new imidazolium ion based phosphotungstate complex in ionic liquid
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A new catalyst based on imidazolium and tungstate ion (tris(imidazolium)- tetrakis(diperoxotungsto)phosphate (3-)) has been synthesized and characterized by FT-IR spectroscopy. An efficient and environmentally friendly procedure is described for the catalyst recycling and easy product isolation for the oxidation of alcohols with hydrogen peroxide catalyzed by imidazolium ion-based phosphotungstate complex in ambient-temperature ionic liquid.
- Chhikara, Bhupender S.,Chandra, Ramesh,Tandon, Vibha
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- Indium hydride catalyzed chemo- and diastereoselective reductive aldol reactions
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The reductive aldol reaction of enones has been established catalyzed by Br2InOMe (cat.)-MePhSiH2 system where Br2InH acted as an active catalytic species. Addition of 1.0 equivalent of MeOH was essential for catalytic turnover. The system, Br2InOMe(cat.)- MePhSiH2-MeOH, provided highly chemoand diastereoselective reductive aldol reaction of enones with functionalized substrates such as α-bromo carbonyls, α-keto esters and α-alkoxy ketones.
- Ieki, Ryosuke,Miyamoto, Shinji,Tsunoi, Shinji,Shibata, Ikuya
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- Highly enantiomerically enriched ketone homoenolate reagents prepared by (-)-sparteine-mediated γ-deprotonation of achiral 1-alkenyl carbamates
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Homoenolate equivalents: Enantiotopos-differentiating deprotonation of achiral 1-alkenyl carbamates with the chiral base n-butyllithium/(-)-sparteine yields configurationally stable lithium homoenolate equivalents. In a subsequent syn or anti substitution (see scheme), γ-substituted O-(1-aryl-1-alkenyl) N,N-diisopropylcarbamates are formed with high enantio- and diastereoselectivity.
- Seppi, Michael,Kalkofen, Rainer,Reupohl, Jens,Froehlich, Roland,Hoppe, Dieter
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- Sonochemical fabrication of Pd/TiO2-nanotubes/Ti plate as a green catalyst for oxidation of alkylarenes and benzyl alcohols
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A facile and fast strategy has been employed to fabricate Pd nanoparticles supported on TiO2 nanotubes/Ti plate via sonochemical deposition. Microstructure studies showed the homogeneous deposition of Pd nanoparticles on the walls of TiO2 nanotubes/Ti plate. The synthesized plate was applied as a novel catalyst for the oxidation of benzyl alcohol and ethylbenzene derivatives. The results of catalytic experiments demonstrated that the modified plate was an efficient green catalyst for the oxidation of benzyl alcohols to benzoic acid derivatives in H2O. The oxidation of alkylarenes was carried out in EtOH:H2O (1:1) ended up with the formation of the corresponding ketone as the sole product. High yields and excellent selectivities were obtained for the oxidation reactions in green solvents using green oxidant. Superior catalytic activity, easy catalyst recovery, and reusability of the catalyst are some advantages of the modified PdNPs/TiO2 nanotubes/Ti plate, indicating a potential application of the catalyst in the industrial oxidation reactions.
- Keshipour, Sajjad,Faraji, Masoud,Asl, Parisa Aboozari
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- Rh-Catalyzed Coupling of Aldehydes with Allylboronates Enables Facile Access to Ketones
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We present herein a novel strategy for the preparation of ketones from aldehydes and allylic boronic esters. This reaction involves the allylation of aldehydes with allylic boronic esters and the Rh-catalyzed chain-walking of homoallylic alcohols. The key to this successful development is the protodeboronation of alkenyl borylether intermediate via a tetravalent borate anion species in the presence of KHF2 and MeOH. This approach features mild reaction conditions, broad substrate scope, and excellent functional group tolerance. Mechanistic studies also supported that the tandem allylation and chain-walking process were involved.
- Zhang, Kezhuo,Huang, Jiaxin,Zhao, Wanxiang
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supporting information
(2022/02/21)
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- Nickel-Catalyzed Reductive Acylation of Carboxylic Acids with Alkyl Halides and N-Hydroxyphthalimide Esters Enabled by Electrochemical Process
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A sustainable Ni-catalyzed reductive acylation reaction of carboxylic acids via an electrochemical pathway is presented, affording a variety of ketones as major products. The reaction proceeds at ambient temperature using unactivated alkyl halides and N-hydroxyphthalimide (NHP) esters as coupling partners, which exhibits several synthetic advantages, including mild conditions and convenience of amplification (58% yield for 6 mmol scale reaction). (Figure presented.).
- Guo, Lin,Xia, Raymond Yang,Xia, Wujiong,Yang, Chao,Zhang, Haoxiang,Zhou, Xiao
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supporting information
(2022/03/31)
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- Rhodium-Catalyzed Regioselective and Chemoselective Deoxygenative Reduction of 1,3-Diketones
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The deoxygenative reduction of carbonyl compounds has been well established. However, most protocols developed typically require harsh reaction conditions or highly reactive/toxic reagents, and the deoxygenative reduction of 1,3-diketones is rarely explored despite their importance to synthetic chemistry and materials science. We describe here a rhodium-catalyzed regioselective and chemoselective deoxygenative reduction of 1,3-diketones under mild reaction conditions. This approach exhibited exceptionally high regioselectivity toward the aliphatic carbonyl reduction over aromatic carbonyl reduction. Moreover, the reaction showed good functional group tolerance and broad substrate scope as well as great potential in the late-stage modification and synthesis of natural products and pharmaceutical skeletons. Preliminary mechanistic studies and DFT calculations revealed that this reaction involved the deoxygenation of 1,3-diketone to α, β-unsaturated ketone and its subsequent 1,4-reduction. The noticeably lower energy barrier of the aliphatic C═O insertion into [Rh]-Bpin versus the aromatic C═O insertion was responsible for the high regioselectivity in this reduction.
- Guo, Xueying,Li, Ruolin,Lin, Zhenyang,Tao, Lei,Zhang, Bing,Zhao, Wanxiang
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p. 4640 - 4647
(2022/05/02)
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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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- 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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- 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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- Synergistic Catalytic?Effect?of N-Hydroxyphthalimide/Cobalt Tetraamide Phthalocyanine and Its Application for Aerobic Oxidation of Hydrocarbons and Alcohols
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Abstract: The activation of oxygen?for?selective?oxidation?of?organic molecules, such as hydrocarbons and alcohols, remains a major catalytic?challenge. We have developed a catalytic system combining N-hydroxyphthalimide (NHPI) with cobalt tetraamide phthalocyanine [CoPc(CONH2)4] for the oxidation of hydrocarbons and alcohols at 75?°C under an oxygen atmosphere. CoPc(CONH2)4 was synthesized by trimellitic anhydride-urea method, and its structure was confirmed by FT-IR, UV–Vis and XRD. This catalyst, in synergy with NHPI/O2 system, exhibited excellent catalytic ability and high selectivity in the oxidation of hydrocarbons and alcohols. Based on the experimental results, a reasonable reaction mechanism was proposed for the oxidation of alkanes and alcohols, respectively. Graphic Abstract: Cobalt tetraamide phthalocyanine (CoPc(CONH2)4) was synthesized by a simple solid-thermal method, and the synergistic catalysis oxidation of NHPI and CoPc(CONH2)4 was studied. A synergistic catalysis system for the aerobic oxidation of hydrocarbons and alcohols by N-hydroxyphthalimide combined with cobalt tetraamide phthalocyanine has been developed.[Figure not available: see fulltext.]
- Li, Fei,Tang, Shuo,Tang, Zhilin,Ye, Lingjun,Li, Hehua,Niu, Fanfan,Sun, Xiaoling
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- Designed pincer ligand supported Co(ii)-based catalysts for dehydrogenative activation of alcohols: Studies onN-alkylation of amines, α-alkylation of ketones and synthesis of quinolines
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Base-metal catalystsCo1,Co2andCo3were synthesized from designed pincer ligandsL1,L2andL3having NNN donor atoms respectively.Co1,Co2andCo3were characterized by IR, UV-Vis. and ESI-MS spectroscopic studies. Single crystal X-ray diffraction studies were investigated to authenticate the molecular structures ofCo1andCo3. CatalystsCo1,Co2andCo3were utilized to study the dehydrogenative activation of alcohols forN-alkylation of amines, α-alkylation of ketones and synthesis of quinolines. Under optimized reaction conditions, a broad range of substrates including alcohols, anilines and ketones were exploited. A series of control experiments forN-alkylation of amines, α-alkylation of ketones and synthesis of quinolines were examined to understand the reaction pathway. ESI-MS spectral studies were investigated to characterize cobalt-alkoxide and cobalt-hydride intermediates. Reduction of styrene by evolved hydrogen gas during the reaction was investigated to authenticate the dehydrogenative nature of the catalysts. Probable reaction pathways were proposed forN-alkylation of amines, α-alkylation of ketones and synthesis of quinolines on the basis of control experiments and detection of reaction intermediates.
- Singh, Anshu,Maji, Ankur,Joshi, Mayank,Choudhury, Angshuman R.,Ghosh, Kaushik
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p. 8567 - 8587
(2021/06/30)
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- Combined Theoretical and Experimental Studies Unravel Multiple Pathways to Convergent Asymmetric Hydrogenation of Enamides
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We present a highly efficient convergent asymmetric hydrogenation of E/Z mixtures of enamides catalyzed by N,P-iridium complexes supported by mechanistic studies. It was found that reduction of the olefinic isomers (E and Z geometries) produces chiral amides with the same absolute configuration (enantioconvergent hydrogenation). This allowed the hydrogenation of a wide range of E/Z mixtures of trisubstituted enamides with excellent enantioselectivity (up to 99% ee). A detailed mechanistic study using deuterium labeling and kinetic experiments revealed two different pathways for the observed enantioconvergence. For α-aryl enamides, fast isomerization of the double bond takes place, and the overall process results in kinetic resolution of the two isomers. For α-alkyl enamides, no double bond isomerization is detected, and competition experiments suggested that substrate chelation is responsible for the enantioconvergent stereochemical outcome. DFT calculations were performed to predict the correct absolute configuration of the products and strengthen the proposed mechanism of the iridium-catalyzed isomerization pathway.
- Ahlquist, M?rten S. G.,Andersson, Pher G.,Eriksson, Lars,Krajangsri, Suppachai,Massaro, Luca,Ponra, Sudipta,Silvi, Emanuele,Singh, Thishana,Su, Hao,Yang, Jianping
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supporting information
p. 21594 - 21603
(2021/12/27)
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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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- Iridium Complexes as Efficient Catalysts for Construction of α-Substituted Ketones via Hydrogen Borrowing of Alcohols in Water
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Ketones are of great importance in synthesis, biology, and pharmaceuticals. This paper reports an iridium complexes-catalyzed cross-coupling of alcohols via hydrogen borrowing, affording a series of α-alkylated ketones in high yield (86 %–95 %) and chemoselectivities (>99 : 1). This methodology has the advantages of low catalyst loading (0.1 mol%) and environmentally benign water as the solvent. Studies have shown the amount of base has a great impact on chemoselectivities. Meanwhile, deuteration experiments show water plays an important role in accelerating the reduction of the unsaturated ketones intermediates. Remarkably, a gram-scale experiment demonstrates this methodology of iridium-catalyzed cross-coupling of alcohols has potential application in the practical synthesis of α-alkylated ketones.
- Luo, Nianhua,Zhong, Yuhong,Wen, Huiling,Shui, Hongling,Luo, Renshi
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p. 1355 - 1364
(2021/03/03)
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- Engineering the large pocket of an (S)-selective transaminase for asymmetric synthesis of (S)-1-amino-1-phenylpropane
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Amine transaminases offer an environmentally benign chiral amine asymmetric synthesis route. However, their catalytic efficiency towards bulky chiral amine asymmetric synthesis is limited by the natural geometric structure of the small pocket, representing a great challenge for industrial applications. Here, we rationally engineered the large binding pocket of an (S)-selective ?-transaminase BPTA fromParaburkholderia phymatumto relieve the inherent restriction caused by the small pocket and efficiently transform the prochiral aryl alkyl ketone 1-propiophenone with a small substituent larger than the methyl group. Based on combined molecular docking and dynamic simulation analyses, we identified a non-classical substrate conformation, located in the active site with steric hindrance and undesired interactions, to be responsible for the low catalytic efficiency. By relieving the steric barrier with W82A, we improved the specific activity by 14-times compared to WT. A p-p stacking interaction was then introduced by M78F and I284F to strengthen the binding affinity with a large binding pocket to balance the undesired interactions generated by F44. T440Q further enhanced the substrate affinity by providing a more hydrophobic and flexible environment close to the active site entry. Finally, we constructed a quadruple variant M78F/W82A/I284F/T440Q to generate the most productive substrate conformation. The 1-propiophenone catalytic efficiency of the mutant was enhanced by more than 470-times in terms ofkcat/KM, and the conversion increased from 1.3 to 94.4% compared with that of WT, without any stereoselectivity loss (ee > 99.9%). Meanwhile, the obtained mutant also showed significant activity improvements towards various aryl alkyl ketones with a small substituent larger than the methyl group ranging between 104- and 230-fold, demonstrating great potential for the efficient synthesis of enantiopure aryl alkyl amines with steric hindrance in the small binding pocket.
- Liu, He,Wang, Hualei,Wei, Dongzhi,Xie, Youyu,Xu, Feng,Xu, Xiangyang,Yang, Lin
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p. 2461 - 2470
(2021/04/22)
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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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- 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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- Fe-S Catalyst Generated in Situ from Fe(III)- And S3?--Promoted Aerobic Oxidation of Terminal Alkenes
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An iron-sulfur complex formed by the simple mixture of FeCl3 with S3?- generated in situ from K2S is developed and applied to selective aerobic oxidation of terminal alkenes. The reaction was carried out under an atmosphere of O2 (balloon) and could proceed on a gram scale, expanding the application of S3?- in organic synthesis. This study also encourages us to explore the application of an Fe-S catalyst in organic reactions.
- Ai, Jing-Jing,Huang, Cheng-Mi,Li, Jian,Liu, Bei-Bei,Rao, Weidong,Wang, Fei,Wang, Shun-Yi
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supporting information
p. 4705 - 4709
(2021/06/28)
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- Photocatalytic Stoichiometric Oxidant-Free Synthesis of Linear Unsaturated Ketones from 1,2-Disubstituted Cyclopropanols
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A one-step catalytic oxidant-free synthesis of unsaturated ketones from 1,2-disubstituted cyclopropanols is reported. Previously for this transformation, only two- and three-step protocols have been developed. The reaction proceeds under irradiation with visible light in the presence of catalytic amounts of both an acridinium photocatalyst and a cobaloxime complex. 2-Aryl-substituted cyclopropanols react giving α,β-unsaturated ketones, while dehydrogenative ring opening of 2-alkyl-substituted substrates affords mixtures of α,β- and β,γ-enones. The reaction starts with one-electron oxidation of a cyclopropanol to cyclopropyloxy radical, presumably, by the photoexcited acridinium catalyst. We also found that Co(dmgBF 2) 2(MeCN) 2complex under an air atmosphere and irradiation with blue LEDs or upon heating can serve as a hydroxycyclopropane oxidant.
- Laktsevich-Iskryk, Marharyta V.,Krech, Anastasiya V.,Zhabinskii, Vladimir N.,Khripach, Vladimir A.,Hurski, Alaksiej L.
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p. 1077 - 1086
(2020/12/14)
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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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- Isotope Effects and the Mechanism of Photoredox-Promoted [2 + 2] Cycloadditions of Enones
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13C kinetic isotope effects (KIEs) for the photoredox-promoted [2 + 2] cycloaddition of enones were determined in homocoupling and heterocoupling examples. The only significant KIEs were observed at the β carbon, indicating that Cβ-Cβ bond formation is irreversible. However, these KIEs were much lower than computational predictions, suggesting that product selectivity is determined in part by a step prior to Cβ-Cβ bond formation. The results are explained as arising from a competition between C-C bond formation and electron exchange between substrate alkenes. This idea is supported by a relatively small substituent effect on substrate selectivity. The possible rates for electron transfer and bond-forming steps are analyzed, and the competition appears plausible, particularly if the mechanism involves a complex between reduced and neutral enone molecules.
- Kuan, Kai-Yuan,Singleton, Daniel A.
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p. 6305 - 6313
(2021/05/29)
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- Rhizopus arrhizus mediated SAR studies in chemoselective biotransformation of haloketones at ambient temperature
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We have demonstrated a green chemistry approach using the fungus Rhizopus arrhizus for the reductive dehalogenation and synthesis of chiral secondary carbinols and halohydrins of pharmaceutical importance in mild, inexpensive, and environmental friendly process at ambient temperature. In the present study, we have succeeded in unravelling the relationship between the position of the substituent group in the structure of substrate and bioreduction activity of the fungus Rhizopus arrhizus. The asymmetric reduction of the carbonyl group to corresponding chiral halohydrin takes place with good yield and excellent enantiomeric excess (≥92%) when the substituent halogen is on the aromatic nucleus. However, novel results concerning reductive dehalogenation are obtained when halogen is incorporated in the alkyl side chain. Thus, the fungus Rhizopus arrhizus has great potential to bring chemoenzymatic biotransformation of halo ketones. Various influential processing parameters such as microbe selection, temperature, pH, etc. were also investigated to optimize the growth of biocatalyst.
- Salokhe, Prabha R.,Salunkhe, Rajeshri S.
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- Copper-Catalyzed Aza-Sonogashira Cross-Coupling To Form Ynimines: Development and Application to the Synthesis of Heterocycles
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Nitrogen-substituted alkynes, such as ynamines and ynamides, are versatile synthetic building blocks. Ynimines bearing additional nucleophilic and electrophilic centers relative to ynamines and ynamides are expected to have high synthetic potential. However, their chemical reactivity remains unexplored owing mainly to the lack of synthetic accessibility. We report herein a versatile copper-catalyzed synthesis of ynimines from readily available O-acetyl ketoximes and terminal alkynes. A wide range of O-acetyl ketoximes derived from diaryl ketones, aryl alkyl ketones and dialkyl ketones underwent cross-coupling with a diverse set of terminal alkynes to afford the ynimines in good to excellent yields. An unprecedented [5+1] heteroannulation reaction exploiting the reactivity of the ynimine generated in situ was subsequently developed for the synthesis of medicinally important heterocycles, including isoquinolines, azaindoles, azabenzofurans, azabenzothiophenes and carbolines.
- Lavernhe, Rémi,Torres-Ochoa, Rubén O.,Wang, Qian,Zhu, Jieping
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supporting information
p. 24028 - 24033
(2021/10/07)
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- Tunable System for Electrochemical Reduction of Ketones and Phthalimides
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Herein, we report an efficient, tunable system for electrochemical reduction of ketones and phthalimides at room temperature without the need for stoichiometric external reductants. By utilizing NaN3 as the electrolyte and graphite felt as both the cathode and the anode, we were able to selectively reduce the carbonyl groups of the substrates to alcohols, pinacols, or methylene groups by judiciously choosing the solvent and an acidic additive. The reaction conditions were compatible with a diverse array of functional groups, and phthalimides could undergo one-pot reductive cyclization to afford products with indolizidine scaffolds. Mechanistic studies showed that the reactions involved electron, proton, and hydrogen atom transfers. Importantly, an N3/HN3 cycle operated as a hydrogen atom shuttle, which was critical for reduction of the carbonyl groups to methylene groups.
- Chen, Gong,Qiao, Tianjiao,Wang, Yaxin,Zhang, Jian,Zhao, Jianyou
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supporting information
p. 3297 - 3302
(2021/10/14)
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- Chemoselective Hydrosilylation of the α,β-Site Double Bond in α,β- And α,β,γ,δ-Unsaturated Ketones Catalyzed by Macrosteric Borane Promoted by Hexafluoro-2-propanol
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The B(C6F5)3-catalyzed chemoselective hydrosilylation of α,β- and α,β,γ,δ-unsaturated ketones into the corresponding non-symmetric ketones in mild reaction conditions is developed. Nearly 55 substrates including those bearing reducible functional groups such as alkynyl, alkenyl, cyano, and aromatic heterocycles are chemoselectively hydrosilylated in good to excellent yields. Isotope-labeling studies revealed that hexafluoro-2-propanol also served as a hydrogen source in the process.
- Zhan, Xiao-Yu,Zhang, Hua,Dong, Yu,Yang, Jian,He, Shuai,Shi, Zhi-Chuan,Tang, Lei,Wang, Ji-Yu
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p. 6578 - 6592
(2020/07/17)
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- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
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Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
- Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
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supporting information
p. 21176 - 21182
(2020/09/17)
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- Synthesis method of aromatic benzyl ketone
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The invention discloses a synthesis method of aromatic benzyl ketone, which comprises the following step: by using oxygen and/or air as an oxidant, oxidizing an aromatic benzyl compound shown in a formula (I) under the action of a catalytic system to obtain aromatic benzyl ketone shown in a formula (II). The catalytic system is formed by combining ferric ions, nitrate radicals and N-hydroxyimide derivatives and does not contain heavy metal ions harmful to human bodies, wherein the molar ratio of the ferric ions to the nitrate radicals is 1: (0.5-5), and the molar ratio of the ferric ions to the N-hydroxyimide derivatives is (0.01-0.1): (0.03-0.2). The method disclosed by the invention is wide in substrate applicability and high in atom utilization rate, avoids the use of harmful heavy metals such as copper and cobalt, and has the characteristics of high efficiency, economy and environmental protection. The formulas are as follows: Ar-CH2-R (I) and Ar-CO-R (II).
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Paragraph 0038-0043
(2020/09/12)
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- A Remote ‘Imidazole’-Based Ruthenium(II) Para-Cymene Pre-catalyst for the Selective Oxidation Reaction of Alkyl Arenes and Alcohols
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Herein we disclosed the use of a remote ‘imidazole’-based precatalyst [(para-cymene)RuII(L)Cl]+, C-1 where L=2-(4-substituted-phenyl)-1H-imidazo[4,5-f][1,10] phenanthroline) for the selective oxidation of a variety of alkyl arenes/heteroarenes and alcohols to their corresponding aldehydes or ketones in presence of tert-butyl hydroperoxide (TBHP). The remote ‘imidazole’ moiety present in the complex facilitates the activation of oxidant and subsequent generation of active species via the release of para-cymene from C-1, which in-turn was less effective without the ‘imidazole’ moiety. The mechanistic features of C-1 promoted oxidation of alkyl arenes were also assessed from spectroscopic, kinetic, and few control experiments. The substrate scope for C-1 promoted oxidation reaction was assessed based on the selective oxidation of 27-different alkyl arenes/heteroarenes and 25 different alcohols to their corresponding aldehydes/ketones in moderate to good yields.
- Dutta, Manali,Bania, Kusum K.,Pratihar, Sanjay
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p. 926 - 932
(2020/03/05)
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- Light and oxygen-enabled sodium trifluoromethanesulfinate-mediated selective oxidation of C-H bonds
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Visible light-induced organic reactions are important chemical transformations in organic chemistry, and their efficiency highly depends on suitable photocatalysts. However, the commonly used photocatalysts are precious transition-metal complexes and elaborate organic dyes, which hamper large-scale production due to high cost. Here, for the first time, we report a novel strategy: light and oxygen-enabled sodium trifluoromethanesulfinate-mediated selective oxidation of C-H bonds, allowing high-value-added aromatic ketones and carboxylic acids to be easily prepared in high-to-excellent yields using readily available alkyl arenes, methyl arenes and aldehydes as materials. The mechanistic investigations showed that the treatment of inexpensive and readily available sodium trifluoromethanesulfinate with oxygen under irradiation of light could in situ form a pentacoordinate sulfide intermediate as an efficient photosensitizer. The method represents a highly efficient, economical and environmentally friendly strategy, and the light and oxygen-enabled sodium trifluoromethanesulfinate photocatalytic system represents a breakthrough in photochemistry. This journal is
- Fu, Hua,Liu, Can,Liu, Yong,Yang, Haijun,Zhu, Xianjin
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supporting information
p. 4357 - 4363
(2020/07/14)
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- Efficient Organoruthenium Catalysts for α-Alkylation of Ketones and Amide with Alcohols: Synthesis of Quinolines via Hydrogen Borrowing Strategy and their Mechanistic Studies
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A new family of phosphine free organometallic ruthenium(II) catalysts (Ru1–Ru4) supported by bidentate NN Schiff base ligands (L1–L4 where L1=N,N-dimethyl-4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazineylidene)methyl) aniline, L2=N,N-diethyl-4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazineylidene)methyl)aniline, L3=N,N-dimethyl-4-((2-phenyl-2-(pyridin-2-yl)hydrazineylidene)methyl)- aniline and L4=N,N-diethyl-4-((2-phenyl-2-(pyridin-2-yl)hydrazineylidene)methyl) aniline) was prepared and characterized. These half-sandwich complexes acted as catalysts for C?C bond formation and exhibited excellent performance in the dehydrogenative coupling of ketones and amides. In the synthesis of C–C bonds, alcohols were utilized as the alkylating agent. A broad range of substrates, including sterically hindered ketones and alcohols, were well tolerated under the optimized conditions (TON up to 47000 and TOF up to 11750 h?1). This ruthenium (II) catalysts were also active towards the dehydrogenative cyclization of o-amino benzyl alcohol for the formation of quinolines derivatives. Various polysubstituted quinolines were synthesized in moderate to excellent yields (TON up to 71000 and TOF up to 11830 h?1). Control experiments were carried out and the ruthenium hydride intermediate was characterized to support the reaction mechanism and a probable reaction pathway of dehydrogenative coupling for the C?C bond formation has been proposed.
- Maji, Ankur,Singh, Anshu,Singh, Neetu,Ghosh, Kaushik
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p. 3108 - 3125
(2020/05/18)
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- Ruthenium-Catalyzed Dehydrogenation of Alcohols with Carbodiimide via a Hydrogen Transfer Mechanism
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Ruthenium-catalyzed oxidative dehydrogenation of alcohols using carbodiimide as an efficient hydrogen acceptor has been developed. The protocol exhibits wide substrate scope with good to excellent yields. The results of the kinetic analysis indicated that the reaction mechanism includes the hydrogen transfer process and that the addition of carbodiimide is essential for the reaction system, and the resulting amidine also could react as a hydrogen acceptor.
- Sueki, Shunsuke,Matsuyama, Mizuki,Watanabe, Azumi,Kanemaki, Arata,Katakawa, Kazuaki,Anada, Masahiro
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p. 4878 - 4885
(2020/06/02)
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- A Simple Biosystem for the High-Yielding Cascade Conversion of Racemic Alcohols to Enantiopure Amines
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The amination of racemic alcohols to produce enantiopure amines is an important green chemistry reaction for pharmaceutical manufacturing, requiring simple and efficient solutions. Herein, we report the development of a cascade biotransformation to aminate racemic alcohols. This cascade utilizes an ambidextrous alcohol dehydrogenase (ADH) to oxidize a racemic alcohol, an enantioselective transaminase (TA) to convert the ketone intermediate to chiral amine, and isopropylamine to recycle PMP and NAD+ cofactors via the reversed cascade reactions. The concept was proven by using an ambidextrous CpSADH-W286A engineered from (S)-enantioselective CpSADH as the first example of evolving ambidextrous ADHs, an enantioselective BmTA, and isopropylamine. A biosystem containing isopropylamine and E. coli (CpSADH-W286A/BmTA) expressing the two enzymes was developed for the amination of racemic alcohols to produce eight useful and high-value (S)-amines in 72–99 % yield and 98–99 % ee, providing with a simple and practical solution to this type of reaction.
- Li, Zhi,Tian, Kaiyuan
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supporting information
p. 21745 - 21751
(2020/09/21)
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- Rhodium-Catalyzed Remote Isomerization of Alkenyl Alcohols to Ketones
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We develop herein an efficient rhodium-catalyzed remote isomerization of aromatic and aliphatic alkenyl alcohols into ketones. This catalytic process, with a commercially available catalyst and ligand ([RhCl(cod)]2 and Xantphos), features high efficiency, low catalyst loading, good functional group tolerance, a broad substrate scope, and no (sub)stoichiometric additive. Preliminary mechanistic studies suggest that this transformation involves an iterative dissociative β-hydride elimination-migration insertion process.
- Dong, Wenke,Yang, Hongxuan,Yang, Wen,Zhao, Wanxiang
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supporting information
(2020/02/28)
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- Method for preparing alpha-alkyl substituted ketone compound
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The invention relates to a method for preparing an alpha-alkyl substituted ketone compound, which comprises the following steps: preparing a primary alcohol compound and a secondary alcohol compound as raw materials, adding alkali; with a cyclic iridium complex as a catalyst and water as a reaction medium, heating and stirring the mixture and reacting for 10 to 24 hours under the protection of inert gas, and cooling a reaction product to room temperature after the reaction is finished; carrying out reduced pressure distillation and concentration to obtain a crude product, and carrying out column chromatography purification to obtain a series of alpha alkyl substituted ketone compounds. The method is simple to operate, available in raw materials, low in price, high in reaction efficiency and selectivity, good in adaptability to various functional groups and wide in substrate universality; since water is used as a reaction medium to meet the green and environment-friendly requirements, the method is environmentally friendly and is carried out at gram level, so that the potential of industrially synthesizing the alpha alkyl substituted ketone compound is achieved; therefore, The method has expanded application in the fields of medicines, organic synthesis and the like.
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-
Paragraph 0173-0180
(2020/12/29)
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- 1,2-Diethoxyethane catalyzed oxidative cleavage of gem-disubstituted aromatic alkenes to ketones under minimal solvent conditions
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Aerobic oxidation using pure dioxygen gas as the oxidant has attracted much attention, but its application in synthetic chemistry has been significantly hampered by the complexity of catalytic system and potential risk of high-energy dioxygen gas. By employing 1,2-diethoxyethane as a catalyst and ambient air as an oxidant, an efficient protocol for the construction of various aryl-alkyl and diaryl ketones through oxidative cleavage of gem-disubstituted aromatic alkenes under minimal solvent conditions has been achieved.
- Liu, Kai-Jian,Deng, Ji-Hui,Zeng, Tang-Yu,Chen, Xin-Jie,Huang, Ying,Cao, Zhong,Lin, Ying-Wu,He, Wei-Min
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supporting information
p. 1868 - 1872
(2020/01/31)
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- A metal-free heterogeneous photocatalyst for the selective oxidative cleavage of CC bonds in aryl olefins: via harvesting direct solar energy
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Selective cleavage of CC bonds is highly important for the synthesis of carbonyl containing fine chemicals and pharmaceuticals. Novel methodologies such as ozonolysis reactions, Lemieux-Johnson oxidation reaction etc. already exist. Parallel to these, catalytic methods using homogeneous catalysts also have been discovered. Considering the various advantages of heterogeneous catalysts such as recyclability and stability, couple of transition metal-based heterogeneous catalysts have been applied for this reaction. However, the pharmaceutical industries prefer to use metal-free catalysts (especially transition metal-free) to avoid further leaching in the final products. This is for sure a big challenge to an organic chemist and to the pharmaceutical industries. To make this feasible, a mild and efficient protocol has been developed using polymeric carbon nitrides (PCN) as metal-free heterogeneous photocatalysts to convert various olefins into the corresponding carbonyls. Later, this catalyst has been applied in the gram scale synthesis of pharmaceutical drugs using direct solar energy. Detailed mechanistic studies revealed the actual role of oxygen, the catalyst, and the light source.
- Das, Shoubhik,Hatami, Nareh,Jooss, Christian,Lange, Niklas Simon,Ronge, Emanuel,Schilling, Waldemar,Zhang, Yu
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supporting information
p. 4516 - 4522
(2020/08/10)
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- Copper-Catalyzed Oxidative Fragmentation of Alkynes with NFSI Provides Aryl Ketones
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A copper-catalyzed oxidative cleavage reaction of alkynes using NFSI and TBHP was described. Various terminal and internal alkyne substrates were employed to render quick access to aryl ketone products in moderate to good yields. NFSI not only functioned as N-centered radical precursors but also engaged in the aryl group migration. Mechanistic studies also suggested the important role of water in the title reactions.
- Chen, Hanfei,Cheng, Hao,Huang, Yifan,Jin, Chaochao,Song, Weihan,Tan, Chen,Tan, Jiajing,Tang, Lin,Yang, Fang,Zhang, Shuaifei
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supporting information
(2020/11/03)
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- Catalyst-Free Photodriven Reduction of α-Haloketones with Hantzsch Ester
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Catalyst-free dehalogenation of α-haloketones under visible light irradiation is studied. The reactions were carried out in common organic solvent. The outcomes of dechlorination are excellent in yields up to 92%, and it is also applicable to bromides, which give even higher yields. The reaction is tolerable to a broad spectrum of substrates, especially to aromatic ketones, including various aryl and hetaryl groups. There are two examples of aliphatic ketones presented in the paper, although their reactivities are not as high as that of the aromatic ketones.
- Lu, Zheng,Yang, Yong-Qing
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p. 508 - 515
(2019/01/10)
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- Ruthenium complexes with PYA pincer ligands for catalytic transfer hydrogenation of challenging substrates
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Here we highlight the potential of a series of ruthenium complexes with tridentate N,N,N pincer-type ligands featuring two pyridylidene amide (PYA) moieties in the ligand skeleton. They were successfully applied in transfer hydrogenation of ketones and C=C double bonds. Rational ligand design was key for increasing the catalytic performance in the reduction of challenging substrates such as potentially chelating acetylpyridines. The specific reaction profiles indicate catalyst poisoning via imine coordination as well as N,O-bidentate coordination of the substrate or the product. Approaches to mitigate this inhibition are presented. Furthermore, these PYA pincer ruthenium complexes accomplish the selective reduction of the C=C over C=O bond of α,β-unsaturated ketones such as benzylideneacetone, while other α,β-unsaturated ketones such as trans-chalcone predominantly underwent oxidative C=C bond cleavage.
- Melle, Philipp,Albrecht, Martin
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p. 299 - 303
(2019/07/08)
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- Novel benzene-based carbamates for ache/bche inhibition: Synthesis and ligand/structure-oriented sar study
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A series of new benzene-based derivatives was designed, synthesized and comprehensively characterized. All of the tested compounds were evaluated for their in vitro ability to potentially inhibit the acetyl-and butyrylcholinesterase enzymes. The selectivity index of individual molecules to cholinesterases was also determined. Generally, the inhibitory potency was stronger against butyryl-compared to acetylcholinesterase; however, some of the compounds showed a promising inhibition of both enzymes. In fact, two compounds (23, benzyl ethyl(1-oxo-1-phenylpropan-2-yl)carbamate and 28, benzyl (1-(3-chlorophenyl)-1-oxopropan-2-yl) (methyl)carbamate) had a very high selectivity index, while the second one (28) reached the lowest inhibitory concentration IC50 value, which corresponds quite well with galanthamine. Moreover, comparative receptor-independent and receptor-dependent structure–activity studies were conducted to explain the observed variations in inhibiting the potential of the investigated carbamate series. The principal objective of the ligand-based study was to comparatively analyze the molecular surface to gain insight into the electronic and/or steric factors that govern the ability to inhibit enzyme activities. The spatial distribution of potentially important steric and electrostatic factors was determined using the probability-guided pharmacophore mapping procedure, which is based on the iterative variable elimination method. Additionally, planar and spatial maps of the host–target interactions were created for all of the active compounds and compared with the drug molecules using the docking methodology.
- Bak, Andrzej,Kozik, Violetta,Kozakiewicz, Dariusz,Gajcy, Kamila,Strub, Daniel Jan,Swietlicka, Aleksandra,Stepankova, Sarka,Imramovsky, Ales,Polanski, Jaroslaw,Smolinski, Adam,Jampilek, Josef
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- The selective oxidation of hydrocarbons on isolated iron active sites under ambient conditions
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The N-doped carbon material supported Fe catalysts were developed for the oxidation of C-H bond of hydrocarbons to ketones and alcohols. The supported Fe catalysts were prepared by pyrolysis of [CMIM]3Fe(CN)6 ionic liquid in activated carbon. And the Fe(Ⅲ)?CN-600 showed good activity and high selectivity for the oxidation of alfa C-H bond of alkylbenzenes. The isolated Fe(Ⅲ) iron active sites should be responsible for the high activity and selectivity for the oxidation of hydrocarbons to ketones. Several ketones were obtained in good to excellent yields. Moreover, cyclohexanone can also be obtained through the oxidation of cyclohexane.
- Qi, Zhengliang,Liu, Junmei,Guo, Wanwan,Huang, Jun
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p. 946 - 955
(2020/01/08)
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- Iron-Decorated, Guanidine Functionalized Metal-Organic Framework as a Non-heme Iron-Based Enzyme Mimic System for Catalytic Oxidation of Organic Substrates
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A novel porous functionalized metal-organic framework (MOF) as a non-heme iron-based enzyme mimic system was achieved via two-step post-synthetic modification of the MIL-101(Cr)-NH2, and characterized by FT-IR, PXRD, TGA, SEM, EDS, CHN, BET surface area, and ICP-OES analyses. This new modified MOF (MIL-101(Cr)-guanidine-Fe) has been demonstrated to be a highly efficient, active, and reusable catalyst for oxidation of various organic substrates, including alcohols, alkenes and alkyl arenes at room temperature using H2O2 as an oxidant. Graphical Abstract: [Figure not available: see fulltext.].
- Shaabani, Ahmad,Mohammadian, Reza,Farhid, Hassan,Karimi Alavijeh, Masoumeh,Amini, Mostafa M.
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p. 1237 - 1249
(2019/03/13)
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- Highly active, homogeneous catalysis by polyoxometalate-assisted N-heterocyclic carbene gold(I) complexes for hydration of diphenylacetylene
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Monomeric, N-heterocyclic (NHC) carbene/carboxylato/gold(I) complex [Au(RS-pyrrld)(IPr)] (RS-Hpyrrld = RS-2-pyrrolidone-5-carboxylic acid; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) (1, 0.01 mmol) in a mixed solvent of 1,4-dioxane: water (4: 1 v/v) showed high activity in the catalysis of the hydration of diphenylacetylene to deoxybenzoin in the presence of protonic acid forms of Keggin polyoxometalates (POMs). The reaction proceeded homogeneously. The catalytic activities were superior to that of the previously reported reaction using the PPh3 derivative of gold(I) complex, [Au(RS-pyrrld)(PPh3)] (3). An important difference is that the reaction of (3) + H-PW12 proceeded in a heterogeneous/suspension system, because of the poor solubility of (3). The present catalytic systems were experimentally stable: re-addition of the substrate (1.5 mmol) to the reaction systems of (1) + H-PW12, (1) + H-SiW12, and (1) + H-AlW12, after the first 2-h reaction, revealed no loss of activity. The effect of the NHC ligand was also examined using the [Au(RS-pyrrld)(NHC)] complexes (NHC = IMes (6), BIPr (7), IF3 (8) and ItBu (9) (see Abbreviations and Scheme 1). We also isolated a novel compound, [Au(H2O)(IPr)]3[α-PW12O40] (2), in 42% yield from a 1: 3 M ratio mixture of (1) in EtOH and H-PW12 in water. Compound (2) showed almost the same catalytic activity and stability as the mixed system of (1) + H-PW12, suggesting that (2) is the actual catalyst precursor. Complexes (1), (2), and (6)-(9) were characterized by elemental analysis, IR, TG/DTA, and (1H and 13C{1H}) NMR, in addition to X-ray crystallography and 31P{1H} NMR for (2). The role of POM in the reactions, i.e., the formation of ion-pair species, was elucidated based on a study of the effects of strong protonic acids such as HBF4, HPF6 and CF3SO3H, instead of POMs, on (1). Quantum-mechanical (QM) calculations indicated that both the catalytically unsaturated species [LAu]+ and the important intermediate [LAu(C2Ph2)]+ in the catalytic cycle are energetically more stable for L = IPr than for L = PPh3, in good agreement with the experimental finding that (1) has much greater catalytic activity and stability than (3).
- Nomiya, Kenji,Murara, Yuichi,Iwasaki, Yuta,Arai, Hidekazu,Yoshida, Takuya,Chikaraishi Kasuga, Noriko,Matsubara, Toshiaki
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p. 144 - 154
(2019/03/13)
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- Electrochemical performance of ABNO for oxidation of secondary alcohols in acetonitrile solution
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The ketones was successfully prepared from secondary alcohols using 9-azabicyclo[3.3.1]nonane-N-oxyl (ABNO) as the catalyst and 2,6-lutidine as the base in acetonitrile solution. The electrochemical activity of ABNO for oxidation of 1-phenylethanol was investigated by cyclic voltammetry, in situ Fourier transform infrared spectroscopy (FTIR) and constant current electrolysis experiments. The resulting cyclic voltammetry indicated that ABNO exhibited much higher electrochemical activity when compared with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) under the similar conditions. A reasonable reaction mechanism of the electrocatalytic oxidation of 1-phenylethanol to acetophenone was proposed. In addition, a series of secondary alcohols could be converted to the corresponding ketones at room temperature in 80-95% isolated yields.
- Niu, Pengfei,Liu, Xin,Shen, Zhenlu,Li, Meichao
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- Naphthyridine-based iridium complexes: Structures and catalytic activity on alkylation of aryl ketones
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Iridium(III) complexes containing a designed ligand, 2-amino-7-(2-pyridinyl)-1,8-naphthyridine derivative, were prepared and all complexes were characterized using spectroscopic and crystallographic methods. These new Ir(III) complexes are able to act as catalysts for the C-alkylation of aryl alkyl ketones with the use of alcohols as the alkylating agent. Typically, acetophenone undergoes alkylation with methanol and ethanol to yield isobutyrophenone and butyrophenone, respectively.
- Chen, Po-Hao,Liu, Yi-Hung,Liu, Shiuh-Tzung
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p. 972 - 981
(2019/05/24)
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- Manganese PNP-pincer catalyzed isomerization of allylic/homo-allylic alcohols to ketones-activity, selectivity, efficiency
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We report the first manganese catalyzed isomerization of allylic alcohols to produce the corresponding carbonyl compounds. The ligand plays a decisive role in the efficiency of this reaction. Very high conversions could be obtained using a solvent-free reaction system. A detailed DFT study reveals a self-dehydrogenation/hydrogenation reaction mechanism which was verified by the isolation of the α,β-unsaturated ketone as intermediate and a deuterium labeling experiment. It also provided a rationale for the observed selectivity and the higher efficiency of phenyl over isopropyl substitution.
- Xia, Tian,Spiegelberg, Brian,Wei, Zhihong,Jiao, Haijun,Tin, Sergey,Hinze, Sandra,De Vries, Johannes G.
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p. 6327 - 6334
(2019/11/20)
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- Combinatorial Mutation Analysis of ω-Transaminase to Create an Engineered Variant Capable of Asymmetric Amination of Isobutyrophenone
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ω-Transaminase (ω-TA) is an important enzyme for asymmetric synthesis of chiral amines. Rapid creation of a desirable ω-TA variant, readily available for scalable process operation, is demanded and has attracted intense research efforts. In this study, we aimed to develop a quantitative mutational analysis (i. e., R-analysis) that enables prediction of combinatorial mutation outcomes and thereby provides reliable guidance of enzyme engineering through combination of already characterized mutations. To this end, we determined three mutatable active-site residues of ω-TA from Ochrobactrum anthropi (i. e., leucine 57, tryptophan 58 and valine 154) by examining activities of nine alanine-scanning mutants for seven substrate pairs. The R-analysis of the mutatable residues is based on assessment of changes in relative activities for a series of structurally analogous substrates. Using three sets of substrates (five α-keto acids, six arylalkylamines and three arylalkyl ketones), we found that combination of two point mutations display additive effects of each mutational outcome such as steric relaxation for bulky substrates or catalytic enhancement for amination of ketones. Consistent with the R-analysis-based prediction, the ω-TA variant harboring triple alanine mutations, i. e. L57A, W58A and V154A, showed high activity improvements for bulky substrates, e. g. a 3.2×104-fold activity increase for 1-phenylbutylamine. The triple mutant even enabled asymmetric amination of isobutyrophenone, carrying a branched-chain alkyl substituent to be accepted in a small binding pocket that normally shows a steric limit up to an ethyl group, with >99% ee of a resulting (S)-amine. (Figure presented.).
- Kim, Hong-Gon,Han, Sang-Woo,Shin, Jong-Shik
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p. 2594 - 2606
(2019/05/15)
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- Decarboxylative Intramolecular Arene Alkylation Using N-(Acyloxy)phthalimides, an Organic Photocatalyst, and Visible Light
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An intramolecular arene alkylation reaction has been developed using the organic photocatalyst 4CzIPN, visible light, and N-(acyloxy)phthalimides as radical precursors. Reaction conditions were optimized via high-throughput experimentation, and electron-rich and electron-deficient arenes and heteroarenes are viable reaction substrates. This reaction enables access to a diverse set of fused, partially saturated cores which are of high interest in synthetic and medicinal chemistry.
- Sherwood, Trevor C.,Xiao, Hai-Yun,Bhaskar, Roshan G.,Simmons, Eric M.,Zaretsky, Serge,Rauch, Martin P.,Knowles, Robert R.,Dhar, T. G. Murali
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p. 8360 - 8379
(2019/09/03)
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- Iron-Enabled Utilization of Air as the Terminal Oxidant Leading to Aerobic Oxidative Deoximation by Organoselenium Catalysis
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In contrast to conventional organoselenium-catalyzed oxidation reactions that require peroxide oxidants such as hydrogen peroxide, in this work we found that, addition of a low loading of iron (II) could enable the successful utilization of air as the terminal oxidant in organoselenium-catalyzed oxidative deoximation reaction of ketoximes. This led to a new mild and relatively green aerobic oxidative deoximation method. Control reactions and X-ray photoelectron spectroscopy (XPS) analysis suggest that iron is crucial in the catalytic cycle, working to prohibit the deactivation of selenium catalyst through an iron-catalyzed aerobic oxidation of low valent selenium species by air to the active high valent selenium species. Since air can be utilized as the terminal oxidant, this work may contribute to the advance of organoselenium catalysis. (Figure presented.).
- Chen, Chao,Zhang, Xu,Cao, Hongen,Wang, Fang,Yu, Lei,Xu, Qing
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p. 603 - 610
(2018/12/14)
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- Rhodium Porphyrin Catalyzed Regioselective Transfer Hydrogenolysis of C-C σ-Bonds in Cyclopropanes with iPrOH
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A new rhodium porphyrin catalyzed regioselective transfer hydrogenolysis of both activated and unactivated cyclopropanes employing iPrOH as the hydrogen source was discovered. The reaction mechanism for the C-C σ-bond activation of cyclopropanes was identified through an initial radical substitution with rhodium(II) metalloporphyrin radical to give a rhodium porphyrin alkyl, followed by hydrogenolysis with iPrOH to give the corresponding acyclic alkanes and regenerate rhodium(II) metalloporphyrin radical.
- Chen, Chen,Feng, Shiyu,Chan, Kin Shing
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p. 2582 - 2589
(2019/07/02)
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- Arylation of Aldehydes to Directly Form Ketones via Tandem Nickel Catalysis
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A nickel-catalyzed arylation of both aliphatic and aromatic aldehydes proceeds with air-stable (hetero)arylboronic acids, with an exceptionally wide substrate scope. The neutral condition tolerates acidic hydrogen and sensitive polar groups and also preserves α-stereocenters of some chiral aldehydes. Interestingly, this nickel(0) catalysis does not follow common 1,2-insertion of arylmetal species to aldehydes and β-hydrogen elimination.
- Lei, Chuanhu,Zhu, Daoyong,Tangcueco, Vicente Iii Tiu,Zhou, Jianrong Steve
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supporting information
p. 5817 - 5822
(2019/08/26)
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