- Fabrication of Ni3N nanorods anchored on N-doped carbon for selective semi-hydrogenation of alkynes
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Nickel is a highly active catalyst for the semi-hydrogenation of alkynes. However, the low selectivity of the alkene product caused by the over-hydrogenation reaction on Ni has hindered its practical applications. In this work, we report a new nickel nitride (Ni3N)-catalyzed semi-hydrogenation of alkynes to the corresponding alkenes. The Ni3N nanorods were facilely fabricated via a direct pyrolysis of the solid mixture of nickel acetate tetrahydrate and melamine (Mlm). The Ni3N phase in the optimum catalyst (Ni3N/NC-6/5-550) is shown to be effective and stable in the semi-hydrogenation of alkynes, with a high yield and good selectivity for alkenes (Z/E ratios up to >99/1). Both terminal and internal alkynes bearing a broad scope of functional groups are readily converted into alkenes with good chemo- and stereoselectivity. Notably, it was found that the over-hydrogenation can be markedly suppressed even at high conversion of alkyne. Density functional theory (DFT) calculations reveal that the low interaction between the alkene product and the Ni3N might plays a critical role in the selectivity enhancement.
- Shi, Xiaozhen,Wen, Xin,Nie, Shilin,Dong, Jie,Li, Jingde,Shi, Yongqing,Zhang, Huiling,Bai, Guoyi
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- Diastereoselectivity in the boron aldol reaction of α-alkoxy and α,β-bis-alkoxy methyl ketones
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In this work, using DFT calculations, we investigated the 1,4 and 1,5 asymmetric induction in boron enolate aldol reactions of α-alkoxy and α,β-bisalkoxy methyl ketones. We evaluated the steric influence of alkyl substituents at the α position and the stereoelectronic influence of the oxygen protecting groups at the α and β positions. Theoretical calculations revealed the origins of the 1,4 asymmetric induction in terms of the nature of the β-substituent. The synergistic effect between the α,β-syn and α,β-anti-bisalkoxy stereocenters was elucidated. In the presence of the β-alkoxy center, the reaction proceeds through the Goodman-Paton 1,5-stereoinduction model, experiencing a minor influence of the α-alkoxy center.
- Fernandes, Alessandra A. G.,Leonarczyk, Ives A.,Ferreira, Marco A. B.,Dias, Luiz Carlos
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supporting information
p. 3167 - 3180
(2019/03/26)
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- Monitoring Hydrogenation Reactions using Benchtop 2D NMR with Extraordinary Sensitivity and Spectral Resolution
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Low-field benchtop nuclear magnetic resonance (BT-NMR) spectrometers with Halbach magnets are being increasingly used in science and industry as cost-efficient tools for the monitoring of chemical reactions, including hydrogenation. However, their use of
- Go?owicz, Dariusz,Kazimierczuk, Krzysztof,Urbańczyk, Mateusz,Ratajczyk, Tomasz
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p. 196 - 200
(2019/04/26)
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- Selective Semihydrogenation of Alkynes Catalyzed by Pd Nanoparticles Immobilized on Heteroatom-Doped Hierarchical Porous Carbon Derived from Bamboo Shoots
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Highly dispersed palladium nanoparticles (Pd NPs) immobilized on heteroatom-doped hierarchical porous carbon supports (N,O-carbon) with large specific surface areas are synthesized by a wet chemical reduction method. The N,O-carbon derived from naturally abundant bamboo shoots is fabricated by a tandem hydrothermal–carbonization process without assistance of any templates, chemical activation reagents, or exogenous N or O sources in a simple and ecofriendly manner. The prepared Pd/N,O-carbon catalyst shows extremely high activity and excellent chemoselectivity for semihydrogenation of a broad range of alkynes to versatile and valuable alkenes under ambient conditions. The catalyst can be readily recovered for successive reuse with negligible loss in activity and selectivity, and is also applicable for practical gram-scale reactions.
- Ji, Guijie,Duan, Yanan,Zhang, Shaochun,Fei, Benhua,Chen, Xiufang,Yang, Yong
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p. 3427 - 3434
(2017/09/15)
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- Ru(ii)-Pheox-catalyzed Si-H insertion reaction: construction of enantioenriched carbon and silicon centers
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We established a highly enantioselective Si-H insertion reaction to construct chiral centers at the carbon and silicon atoms, using a Ru(ii)-pheox catalyst. The catalytic asymmetric Si-H insertion reaction of α-methyl-α-diazoesters proceeded smoothly with excellent stereoinduction at both the neighboring carbon and silicon atoms (up to 99% yield and 99% ee).
- Nakagawa, Yoko,Chanthamath, Soda,Fujisawa, Ikuhide,Shibatomi, Kazutaka,Iwasa, Seiji
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supporting information
p. 3753 - 3756
(2017/04/03)
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- Design of Core-Pd/Shell-Ag Nanocomposite Catalyst for Selective Semihydrogenation of Alkynes
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We designed core-Pd/shell-Ag nanocomposite catalyst (Pd@Ag) for highly selective semihydrogenation of alkynes. The construction of the core-shell nanocomposite enables a significant improvement in the low activity of Ag NPs for the selective semihydrogenation of alkynes because hydrogen is supplied from the core-Pd NPs to the shell-Ag NPs in a synergistic manner. Simultaneously, coating the core-Pd NPs with shell-Ag NPs results in efficient suppression of overhydrogenation of alkenes by the Pd NPs. This complementary action of core-Pd and shell-Ag provides high chemoselectivity toward a wide range of alkenes with high Z-selectivity under mild reaction conditions (room temperature and 1 atm H2). Moreover, Pd@Ag can be easily separated from the reaction mixture and is reusable without loss of catalytic activity or selectivity.
- Mitsudome, Takato,Urayama, Teppei,Yamazaki, Kenji,Maehara, Yosuke,Yamasaki, Jun,Gohara, Kazutoshi,Maeno, Zen,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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supporting information
p. 666 - 670
(2016/02/18)
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- Rhodium(II)-catalyzed c-h functionalization of electron-deficient methyl groups
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Enantioselective C-H functionalization of relatively electron-deficient methyl sites was achieved with the combination of 2,2,2-trichloroethyl aryldiazoacetates and tetrakis(triarylcyclopropanecarboxylate) dirhodium catalysts. The substrate scope of the transformation was relatively broad, and C-H functionalization products were furnished with excellent levels of enantioselectivity. As a strategic reaction, crotonate derivatives give 1,6-dicarbonyl compounds, which are useful for further diversification.
- Fu, Liangbing,Guptill, David M.,Davies, Huw M. L.
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supporting information
p. 5761 - 5764
(2016/06/08)
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- NOVEL TRICYCLIC COMPOUNDS
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The invention provides compounds of Formula (I) pharmaceutically acceptable salts, pro-drugs, biologically active metabolites, stereoisomers and isomers thereof wherein the variable are defined herein. The compounds of the invention are useful for treating immunological and oncological conditions.
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Paragraph 0533-0535
(2013/03/28)
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- Highly enantioselective cyclopropenation reaction of 1-alkynes with α-alkyl-α-diazoesters catalyzed by dirhodium(II) carboxylates
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Two rhodium(II) ions work together: [Rh2(S-tbpttl)4] is an exceptionally effective catalyst for enantioselective cyclopropenation reactions of 1-alkynes with α-alkyl-α-diazoacetates (see scheme). Cyclopropenation is preferred over alkene formation through a 1,2-hydride shift. Copyright
- Goto, Takayuki,Takeda, Koji,Shimada, Naoyuki,Nambu, Hisanori,Anada, Masahiro,Shiro, Motoo,Ando, Kaori,Hashimoto, Shunichi
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supporting information; experimental part
p. 6803 - 6808
(2011/08/21)
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- Rh-catalyzed intermolecular cyclopropanation with α-alkyl-α- diazoesters: Catalyst-dependent chemo- and diastereoselectivity
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(Chemical Equation Presented) A Rh-catalyzed procedure for the cyclopropanation of alkenes with α-alkyl-α-diazoesters is described. With dirhodium tetraoctanoate, the predominant pathway is β-hydride elimination. While a number of sterically demanding carboxylate ligands serve to avoid β-hydride elimination, it was found that triphenylacetate (TPA) also imparts high diastereoselectivity.
- Panne, Patricia,DeAngelis, Andrew,Fox, Joseph M.
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body text
p. 2987 - 2989
(2009/04/18)
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- Rh-catalyzed formation of dioxolanes from α-alkyl diazoesters: Diastereoselective cycloadditions of carbonyl ylides with selectivity over β-hydride elimination
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(Chemical Equation Presented) Described here is a diastereoselective Rh-catalyzed method for the preparation of dioxolanes from α-alkyl- α-diazoesters. This represents the first general method for generating carbonyl ylides from α-diazoesters that possess β-hydrogens, as such diazo compounds typically give rise to alkenes via β-hydride elimination. Subsequent cycloaddition with aromatic aldehydes gives tetrasubstituted dioxolanes with unusually high diastereoselectivity. A model is set forth to explain the diastereoselectivity of the cycloaddition.
- DeAngelis, Andrew,Panne, Patricia,Yap, Glenn P. A.,Fox, Joseph M.
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p. 1435 - 1439
(2008/09/17)
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- Virtually complete E-selective α,β-unsaturated ester synthesis by Hg(OTf)2-catalyzed hydration of sec-ethoxyalkynyl acetate
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The reaction of alkyl-substituted sec-ethoxyalkynyl acetates with water catalyzed by Hg(OTf)2 afforded α,β-unsaturated esters in excellent yield with high catalytic turnover up to 1000 times under very mild reaction conditions with virtually complete E-selectivity, superior even to that of the HWE reaction.
- Nishizawa, Mugio,Hirakawa, Hiroko,Nakagawa, Yuki,Yamamoto, Hirofumi,Namba, Kosuke,Imagawa, Hiroshi
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p. 5577 - 5580
(2008/09/17)
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- Cobalt Catalysed Carbonylation of Organic Halides under Solid-Liquid Phase Transfer Conditions
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Organic halides are carbonylated under solid liquid phase transfer conditions using Co-(CO)4 as catalyst under Co (1 atmosphere) at 25 deg C to afford corresponding esters in good yields.No Carbonylation is effected in absence of phase transfer agent (PTA).The striking example is the carbonylation of ethyl haloacetate to diethyl malonate, an important organic intermediate.The parameters such as concentration of PTA, and catalyst and temperature are optimised.
- Kantam, M.Lakshmi,Reddy, N.Prabhakar,Choudary, B.M.
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p. 2631 - 2640
(2007/10/02)
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- Synthetic and Biological Studies of Compactin and Related Compounds. 3. Synthesis of the Hexalin Portion of Compactin
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Several synthons for the hexalin moiety of compactin (1) have been prepared, and a procedure for production of the key alcohol 5 in enantiomerically homogeneous form is presented.Diels-Alder reaction of ethyl (Z)-crotonate and Danishefsky's diene affords cycloadduct 6 (78percent).Hydride reduction followed by silylation of the resulting primary alcohol gives enone 8 (72percent).Two-step cyclohexene annelation furnishes enone 11 (42-55percent), which is elaborated to diene 21 by using a modification of the Shapiro olefin synthesis (three steps, 60percent).Dithiane hydrolysis followed by L-Selectride (Aldrich) reduction of the resulting ketone affords axial alcohol 28.Compound 28 possesses the correct relative stereochemistry at the four contiguous asymmetric carbon atoms in the hexalin portion of 1, and the synthesis is suitable for large-scale preparation (ten steps, 10-14 percent, no isomer separations).Functional group manipulations give synthons 36-39.Acid-catalyzed dehydration of allylic alcohol 19 affords diene isomer 20 (11:1).A simple procedure for the preparation of large quantities of ethyl (Z)-crotonate is also presented.
- Rosen, Terry,Taschner, Michael J.,Thomas, James A.,Heathcock, Clayton H.
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p. 1190 - 1201
(2007/10/02)
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- SYNTHESIS AND BIOLOGICAL ACTIVITY OF THE HEXALIN MOIETY OF COMPACTIN (ML-236B)
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Alcohols 14 and 21 and the derived half-glutarate esters 15 and 22 have been prepared and evaluated as inhibitors of HMG CoA reductase.Compound 14, the hexalin moiety of the natural fungal metabolite compactin (ML-236B) and compound 21, its isomeric diene, have essentially no inhibitory properties.Compound 15 and 22 show definite activity, although several orders of magnitude lower than that shown by compactin.
- Heathcock, Clayton H.,Taschner, Michael J.,Rosen, Terry,Thomas, James A.,Hadley, Cheri R.,Popjak, George
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p. 4747 - 4750
(2007/10/02)
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- SUBSTITUTION NUCLEOPHILE VINYLIQUE PAR LE REACTIF DE REFORMATSKY CATALYSSE PAR DES COMPLEXES DU NICKEL ET DU PALLADIUM ZEROVALENTS. SYNTHESE D'ESTERS β,γ-ETHYLENIQUES
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Zerovalent complexes of palladium and nickel catalyse vinylic nucleophilic substitution by the Reformatsky reagent giving β,γ-ethylenic esters.Formation of a ?-vinylpalladium complex is the rate-determining step of the reaction.
- Fauvarque, J.F.,Jutand, A.
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p. 109 - 114
(2007/10/02)
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- A Comparison of the Effects of Steric Crowding at Phosphorus on the Steric Course of Wittig Reactions of Stabilised and Semistabilised Ylides
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The cis-trans ratio of the alkenes formed in Wittig reactions of semistabilised ylides (derived from benzyltriarylphosphonium salts in ethanolic sodium ethoxide) with benzaldehyde, acetaldehyde or trimethylacetaldehyde increases as steric crowding at phosphorus increases.In contrast, the cis-trans ratio of the unsaturated esters formed in the related reactions of the stabilised ethoxycarbonylmethylene ylides decreases as steric crowding at phosphorus increases.The relevance of these results to recent proposals for the mechanism of the Wittig reaction is considered. - Keywords: Alkene cis-trans Ratio, Reaction Mechanism
- Allen, David W.
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p. 1455 - 1458
(2007/10/02)
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- The Chemistry of Heteroarylphosphorus Compounds, Part 14 Effects of Heteroaryl Substituents at Phosphorus on the Steric Course of Wittig Reactions of Semistabilised and Stabilised Ylides
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The cis-trans ratio of the stilbenes formed in Wittig reactions of semistabilised ylides (derived from benzyltri(hetero)arylphosphonium salts in ethanolic ethoxide) with benzaldehyde decreases markedly in the series 2-furyl > 2-thienyl > phenyl > 1-methylpyrrol-2-yl.The 2-furyl group favours a greater proportion of the cis-isomer than m-trifluoromethylphenyl, whereas the 1-methylpyrrol-2-yl group favours a greater proportion of the trans isomer than p-methoxyphenyl.Similarly, in Wittig reactions of carbonyl-stabilised ylides with benzaldehyde and acetaldehyde, the presence at phosphorus of 2-furyl groups results in a significant increase in the proportion of the cis-alkene compared to that formed from the related triphenylphosphonium ylide.These results are discussed in terms of both betaine and cycloaddition mechanisms for the Wittig reaction.Also discussed is their relevance to recent proposals concerning the eliminaton of alkene from the intermediate oxaphosphetan. - Keywords: Alkene cis-trans Ratio, Betaine Mechanism, Cycloaddition Mechanism
- Allen, David W.,Ward, Helen
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p. 754 - 757
(2007/10/02)
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