- Electrochemical Proton Reduction over Nickel Foam for Z-Stereoselective Semihydrogenation/deuteration of Functionalized Alkynes
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Selective reduction strategies based on abundant-metal catalysts are very important in the production of chemicals. In this paper, a method for the electrochemical semihydrogenation and semideuteration of alkynes to form Z-alkenes was developed, using a simple nickel foam as catalyst and H3O+ or D3O+ as sources of hydrogen or deuterium. Good yields and excellent stereoselectivities (Z/E up to 20 : 1) were obtained under very mild reaction conditions. The reaction proceeded with terminal and nonterminal alkynes, and also with alkynes containing easily reducible functional groups, such as carbonyl groups, as well as aryl chlorides, bromides, and even iodides. The nickel-foam electrocatalyst could be recycled up to 14 times without any change in its catalytic properties.
- Valiente, Alejandro,Martínez-Pardo, Pablo,Kaur, Gurpreet,Johansson, Magnus J.,Martín-Matute, Belén
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- Synthesis of α-diazoesters from α-hydrazonoesters: Utilization of α-hydrazonoesters and α-diazoesters for convenient interconversion
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We have developed a novel method to synthesize α-diazoesters from α-hydrazonoesters with a catalytic amount of Cu(OAc)2 in acetonitrile. When the reaction was carried out under an argon atmosphere, the reaction stopped halfway, suggesting that this reaction required oxygen to reoxidize the catalyst. Since hydrazonoesters can be obtained by reduction of α-diazoesters with P(n-Bu)3 in diisopropyl ether, these 2 compounds are mutually interconvertible with ease. Whereas α-diazoesters are unstable and unsuitable for storage, hydrazonoesters are more stable, especially crystalline hydrazonoesters. Thus, hydrazonoesters, which are suitable for long-term storage, could be conveniently used as precursors for α-diazoesters.
- Yasui, Eiko,Ishimine, Kanako,Nitanai, Sohta,Hatakeyama, Nanami,Nagumo, Shinji
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- A Straightforward, Purification-Free Procedure for the Synthesis of Ando and Still-Gennari Type Phosphonates
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Z-Selective Still-Gennari and Ando modifications of the typically E-selective Horner-Wadsworth-Emmons reaction are highly valuable synthetic tools in organic chemistry. These procedures are based on application of bis(2,2,2-trifluoroethyl) phosphonates or diaryl phosphonates, respectively, for the olefination of carbonyl groups. In our research, we present an improved, straightforward, purificationfree procedure for the synthesis of these reagents. The key step of our procedure is the reaction of phosphonic dichlorides with the appropriate sodium alkoxides, which results in 52-97% isolated yields of the desired products on a gram scale. The whole three-step process is performed in one pot. Most importantly, the product is obtained in over 95% purity after simple extraction, avoiding column chromatography and distillation. Moreover, we present the synthesis of a novel Still-Gennari type reagent, bis(1,1,1,3,3,3-hexafluoroisopropyl) phosphonates, which may exhibit improved Z-selectivity in Still-Gennari olefinations.
- Janicki, Ignacy,Kie?basiński, Piotr
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p. 378 - 382
(2021/10/21)
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- Z-Selective phosphine promoted 1,4-reduction of ynoates and propynoic amides in the presence of water
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Phosphine-mediated reductions of substituted propynoic esters and amides in the presence of water yield the partially reduced α,β-unsaturated esters and amides with highZ-selectivity. The competitivein situ ZtoE-isomerization of the product in some cases lowers theZtoEratios of the isolated α,β-unsaturated carbonyl products. Reaction time and the amounts of phosphine and water in the reaction mixture are the key experimental factors which control the selectivity by preventing or reducing the rates ofZ- toE-product isomerization. Close reaction monitoring enables isolation of theZ-alkenes with high selectivities. The computational results suggest that the reactions could be highlyZ-selective owing to the stereoselective formation of theE-P-hydroxyphosphorane intermediate.
- Drikermann, Denis,Kupfer, Stephan,Seifert, Fabian,Steinmetzer, Johannes,Vilotijevic, Ivan,Zi, You
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supporting information
p. 6092 - 6097
(2021/07/21)
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- Controlling Enantioselectivity and Diastereoselectivity in Radical Cascade Cyclization for Construction of Bicyclic Structures
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Radical cascade cyclization reactions are highly attractive synthetic tools for the construction of polycyclic molecules in organic synthesis. While it has been successfully implemented in diastereoselective synthesis of natural products and other complex compounds, radical cascade cyclization faces a major challenge of controlling enantioselectivity. As the first application of metalloradical catalysis (MRC) for controlling enantioselectivity as well as diastereoselectivity in radical cascade cyclization, we herein report the development of a Co(II)-based catalytic system for asymmetric radical bicyclization of 1,6-enynes with diazo compounds. Through the fine-tuning of D2-symmetric chiral amidoporphyrins as the supporting ligands, the Co(II)-catalyzed radical cascade process, which proceeds in a single operation under mild conditions, enables asymmetric construction of multisubstituted cyclopropane-fused tetrahydrofurans bearing three contiguous stereogenic centers, including two all-carbon quaternary centers, in high yields with excellent stereoselectivities. Combined computational and experimental studies have shed light on the underlying stepwise radical mechanism for this new Co(II)-based cascade bicyclization that involves the relay of several Co-supported C-centered radical intermediates, including α-, β-, γ-, and ?-metalloalkyl radicals. The resulting enantioenriched cyclopropane-fused tetrahydrofurans that contain a trisubstituted vinyl group at the bridgehead, as showcased in several stereospecific transformations, may serve as useful intermediates for stereoselective organic synthesis. The successful demonstration of this new asymmetric radical process via Co(II)-MRC points out a potentially general approach for controlling enantioselectivity as well as diastereoselectivity in synthetically attractive radical cascade reactions.
- Lee, Wan-Chen Cindy,Mckillop, Alexander M.,Wang, Duo-Sheng,Zhang, Congzhe,Zhang, X. Peter
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supporting information
p. 11130 - 11140
(2021/07/31)
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- Heteroleptic Copper-Based Complexes for Energy-Transfer Processes: E → Z Isomerization and Tandem Photocatalytic Sequences
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Energy-transfer processes involving copper complexes are rare. Using an optimized heteroleptic copper complex, Cu(bphen)(XantPhos)BF4, photosensitized E → Z isomerization of olefins is demonstrated. The XantPhos ligand afforded sensitizers with improved catalyst stability, while the bphen ligand lengthened the excited-state lifetime. A series of 25 di- and trisubstituted alkenes underwent photoisomerization, including macrocycles and 1,3-enynes. Cu(bphen)(XantPhos)BF4 could also be employed in a tandem ATRA/photoisomerization process employing arylsulfonyl chlorides, an example of photoisomerization with halide-substituted olefins.
- Cruché, Corentin,Neiderer, William,Collins, Shawn K.
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p. 8829 - 8836
(2021/07/28)
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- Heterogeneous Isomerization for Stereoselective Alkyne Hydrogenation to trans-Alkene Mediated by Frustrated Hydrogen Atoms
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Stereoselective production of alkenes from the alkyne hydrogenation plays a crucial role in the chemical industry. However, for heterogeneous metal catalysts, the olefins in cis-configuration are usually dominant in the products due to the most important and common Horiuti-Polanyi mechanism involved over the metal surface. In this work, through combined theoretical and experimental investigations, we demonstrate a novel isomerization mechanism mediated by the frustrated hydrogen atoms via the H2 dissociation at the defect on solid surface, which can lead to the switch in selectivity from the cis-configuration to trans-configuration without overhydrogenation. The defective Rh2S3 with exposing facet of (110) exhibits outstanding performance as a heterogeneous metal catalyst for stereoselective production of trans-olefins. With the frustrated hydrogen atoms at spatially separated high-valence Rh sites, the isolated hydrogen mediated cis-to-trans isomerization of olefins can be effectively conducted and the overhydrogenation can be completely inhibited. Furthermore, the bifunctional Rh-S/Pd nanosheets have been synthesized through the surface modification of Pd nanosheets with rhodium and sulfide. With the selective semihydrogenation of alkynes into cis-olefins catalyzed by the small surface PdSx ensembles, the bifunctional Rh-S/Pd nanosheets exhibit excellent activity and stereoselectivity in the one-pot alkyne hydrogenation into trans-olefin, which surpasses the most reported homogeneous and heterogeneous catalysts.
- Zhang, Weijie,Qin, Ruixuan,Fu, Gang,Zheng, Nanfeng
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supporting information
p. 15882 - 15890
(2021/10/02)
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- Synthesis of new adamantyl-imine palladium(II) complexes and their application in Mizoroki-Heck and Suzuki-Miyaura C[sbnd]C cross-coupling reactions
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Improving carbon–carbon cross-coupling reactions is an ongoing process and finding the most versatile and stable catalyst precursors has been of great interest. Ligand design has been proven to be important since it is responsible for providing electron density and steric saturation around the metal centre, thus contributing towards the stereo-electronic properties. The adamantyl moiety has been used to generate highly bulky and electron-rich ligands for application in palladium-catalysed cross-coupling reactions. Accordingly, we have prepared some Schiff-base adamantyl ligands (L1-L3) and complexed them with [PdCl2(MeCN)2] to afford the (pre)catalysts C1-C3, which were successfully applied in Mizoroki-Heck and Suzuki-Miyaura carbon–carbon cross-coupling reactions. The cross-coupling reaction products were obtained in good yields using 0.5 mol % Pd catalyst loading. C2 and C3 showed remarkable activity in the Mizoroki-Heck coupling reactions involving substrates with substituents on the olefin and aryl halide (including 4-Cl, 4-CH3, -CO2Me and -CO2Et). We also, observed that the Suzuki-Miyaura cross-coupling system was active towards challenging activated and deactivated aryl chlorides, with to up 70% conversions recorded. The mercury poisoning tests conducted revealed that the catalysts act as homogenous molecular active species in the Mizoroki-Heck reactions and act as both homogenous and heterogeneous catalysts in the Suzuki-Miyaura cross-coupling reactions.
- Makhubela, Banothile C. E.,Matsheku, Asanda C.,Maumela, Munaka C.
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- Donor-acceptor fluorophores as efficient energy transfer photocatalysts for [2 + 2] photodimerization
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Mild [2 + 2] photodimerization of enone substrates was induced by donor-acceptor fluorophores. Enone substrates were activated efficiently for anti-head to head dimerizations with a high yield (up to 83%) and high selectivity. The adjustable excited state potential also allows donor-acceptor fluorophores to be used for isomerization of the above substrates, confirming the potential of donor-acceptor fluorophores as energy transfer photocatalysts.
- Chen, Feng,Chen, Hao,Liu, Xue-Fen,Luo, Shu-Ping,Ren, Chen-Chao,Wu, Qing-An,Xu, Liang-Xuan,Yu, Xiao-Cong
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supporting information
p. 3707 - 3716
(2020/06/03)
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- Rational design of triplet sensitizers for the transfer of excited state photochemistry from UV to visible
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Time Dependent Density Functional Theory has been used to assist the design and synthesis of a series thioxanthone triplet sensitizers. Calculated energies of the triplet excited state (ET) informed both the type and position of auxochromes placed on the thioxanthone core, enabling fine-tuning of the UV-vis absorptions and associated triplet energies. The calculated results were highly consistent with experimental observation in both the order of the λmax and ET values. The synthesized compounds were then evaluated for their efficacies as triplet sensitizers in a variety of UV and visible light preparative photochemical reactions. The results of this study exceeded expectations; in particular [2 + 2] cycloaddition chemistry that had previously been sensitized in the UV was found to undergo cycloaddition at 455 nm (blue) with a 2- to 9-fold increase in productivity (g/h) relative to input power. This study demonstrates the ability of powerful modern computational methods to aid in the design of successful and productive triplet sensitized photochemical reactions.
- Booker-Milburn, Kevin,Elliott, Luke D.,George, Michael W.,Kayal, Surajit
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supporting information
p. 14947 - 14956
(2020/10/13)
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- Rh-Catalyzed Direct Carboxylation of Alkenyl C?H Bonds of Alkenylpyrazoles
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The Rh-catalyzed direct carboxylation of alkenyl C?H bonds was achieved by using pyrazole as a removable directing group. In the presence of 5 mol% RhCl3 ? 3H2O, 6 mol% P(Mes)3, and 2 equiv. of AlMe2(OMe), the alkenyl C?H bond of various alkenylpyrazoles was directly carboxylated in good yields under CO2 atmosphere. Furthermore, several useful transformations of the pyrazole moiety of the product were achieved to afford synthetically useful carboxylic acid derivatives in good yields.
- Saitou, Takanobu,Jin, Yushu,Isobe, Kotaro,Suga, Takuya,Takaya, Jun,Iwasawa, Nobuharu
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p. 1941 - 1944
(2020/06/10)
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- 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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- Transfer semihydrogenation of alkynes catalyzed by imidazo[1,5-a]pyrid-3-ylidenepd complexes: Positive effects of electronic and steric features on N-heterocyclic carbene ligands
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To investigate the catalytic utility of the imidazo[1,5-a]pyrid-3-ylidene (IPC) ligand, Pd-catalyzed transfer semihydrogenation of alkynes with formic acid as a hydrogen source was conducted. The steric bulkiness of the substituent on N2 affected the configuration of the π-allyl moiety of the precatalyst of IPC-Pd-π-allyl complexes and the robustness of the catalytic process. The catalytic activities of IPC-Pd complexes were clearly higher than those of conventional NHC-Pd complexes.
- Mizuno, Takahiro,Murai, Toshiaki,Shibahara, Fumitoshi,Shibata, Yoshifuru
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p. 332 - 337
(2020/04/27)
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- Pd Nanoparticles and Aminopolymers Confined in Hollow Silica Spheres as Efficient and Reusable Heterogeneous Catalysts for Semihydrogenation of Alkynes
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A yolk-shell nanostructured composite composed of Pd nanoparticles (NPs) and aminopolymers, poly(ethylenimine) (PEI), confined in hollow silica spheres which act as an efficient and stable heterogeneous catalyst for semihydrogenation of alkynes is reported herein. The yolk-shell nanostructured Pd-PEI-silica composite catalysts (Pd+PEI@HSS), consisting of Pd NPs core ca. 5-9 nm in diameter and a porous silica shell ca. 30-50 nm in shell thickness, are fabricated by a facile one-pot method using linear- or branched-type PEI (Mw = 1,800-2,500) as an organic template. On the basis of comprehensive structural analyses by FE-SEM, TEM, N2 physisorption, IR, TG, and Pd K-edge XAFS, we show that metal Pd NPs and PEI molecules are encapsulated in the hollow silica sphere with a size of ca. 100-160 nm. The Pd+PEI@HSS composite shows an activity at near room temperature in the liquid-phase hydrogenation of diphenylacetylene to selectively produce cis-stilbene with 95% yield, which outperforms those of the previously reported Pd/PEI and Lindlar catalysts. Interestingly, the catalyst encapsulating linear-type PEI provides a markedly high alkene selectivity in the semihydrogenation of phenylacetylene to produce styrene owing to the strong poisoning effect of linear PEI, which is clearly revealed by an isotope study using H2/D2/acetylene (or ethylene) gases. The catalyst synthesized with optimum silica shell thickness can be easily recovered and recycled without any loss of palladium species and PEI and retaining high activities and selectivities over multiple cycles owing to the ability of the protective effect of silica shell, rendering this material an efficient and stable catalyst for semihydrogenation of alkynes.
- Kuwahara, Yasutaka,Kango, Hiroto,Yamashita, Hiromi
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p. 1993 - 2006
(2019/02/19)
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- Pyrimidopteridine N-Oxide Organic Photoredox Catalysts: Characterization, Application and Non-Covalent Interaction in Solid State
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Herein we report the photo- and electrochemical characterization of pyrimidopteridine N-oxide-based heterocycles. The potential of their application as organic photoredox catalysts is showcased in the photomediated contra-thermodynamic E→Z isomerization of cinnamic acid derivatives and oxidative cyclization of 2-phenyl benzoic acid to benzocoumarin using molecular oxygen as a mild oxidant. Furthermore, unprecedented intermolecular non-covalent n–π-hole interactions in solid state are discussed based on crystallographic and theoretical data.
- Hauptmann, Richy,Petrosyan, Andranik,Fennel, Franziska,Argüello Cordero, Miguel A.,Surkus, Annette-E.,Pospech, Jola
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supporting information
p. 4325 - 4329
(2019/03/29)
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- Carbocation Lewis Acid TrBF4-Catalyzed 1,2-Hydride Migration: Approaches to (Z)-α,β-Unsaturated Esters and α-Branched β-Ketocarbonyls
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Carbocation Lewis acid TrBF4-catalyzed 1,2-hydride migration of α-alkyldiazoacetates themselves or in situ-generated cross-coupling adducts of aldehydes and α-alkyldiazoacetates has been developed, affording (Z)-α,β-unsaturated esters and α-branched β-ketocarbonyls, respectively, in good yields and with high regioselectivities.
- Duan, Depeng,Liu, Yongjun,Lv, Jian,Shang, Wansong
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supporting information
(2019/10/08)
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- Phosphetane oxides as redox cycling catalysts in the catalytic wittig reaction at room temperature
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Recently, phosphorus redox cycling has gained significant importance for a number of transformations originally requiring the use of stoichiometric amounts of phosphorus reagents. While these methodologies have several benefits, high catalyst loadings (≥10 mol percent) and harsh reaction conditions (T ≥ 100 °C) often limit their versatility and applicability. Herein, we report differently substituted phosphetane oxides as efficient catalysts for the catalytic Wittig reaction. The phosphetane scaffold is easy to modify, and a number of catalysts can be obtained in a simple two-step synthesis. The activity in the Wittig reaction significantly surpasses previously reported phospholane-based catalysts and the reaction can be conducted with catalyst loadings as low as 1.0 mol percent even at room temperature. Furthermore, a Br?nsted acid additive is no longer required to achieve high yields at these mild conditions. A methyl-substituted phosphetane oxide was employed to synthesize 25 different alkenes with yields of up to 97percent. The methodology has a good functional group tolerance and the reaction can be performed starting with alkyl chlorides, bromides, or iodides. Additionally, it was possible to use poly(methylhydrosiloxane) as the terminal reductant in the catalytic Wittig reaction employing 2-MeTHF as a renewable solvent. The intermediates of the Wittig reaction were analyzed by 31P NMR spectroscopy, and in situ NMR experiments confirmed phosphane oxide as the resting state of the catalyst. Further kinetic investigations revealed a striking influence of the base on the rate of phosphane oxide reduction.
- Longwitz, Lars,Spannenberg, Anke,Werner, Thomas
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p. 9237 - 9244
(2019/10/08)
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- Cobalt catalyzed stereodivergent semi-hydrogenation of alkynes using H2O as the hydrogen source
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Cobalt-catalyzed stereodivergent semi-hydrogenation of internal alkynes to alkenes is developed. The reaction proceeded through transfer hydrogenation under mild conditions using a base metal CoI2 as the catalyst, and H2O/MeOH as the hydrogen source with Zn as the reductant. The E/Z-selectivity of the product could be switched by changing the solvent and by inclusion/exclusion of a bidentate phosphine ligand (dppe). This method provides a simple and cost effective pathway for the synthesis of 1,2-dideuterioalkenes.
- Li, Kangkui,Khan, Ruhima,Zhang, Xuexin,Gao, Yang,Zhou, Yongyun,Tan, Heng,Chen, Jingchao,Fan, Baomin
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supporting information
p. 5663 - 5666
(2019/05/21)
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- The Catalytic Asymmetric Mukaiyama–Michael Reaction of Silyl Ketene Acetals with α,β-Unsaturated Methyl Esters
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α,β-Unsaturated esters are readily available but challenging substrates to activate in asymmetric catalysis. We now describe an efficient, general, and highly enantioselective Mukaiyama–Michael reaction of silyl ketene acetals with α,β-unsaturated methyl esters that is catalyzed by a silylium imidodiphosphorimidate (IDPi) Lewis acid.
- Gatzenmeier, Tim,Kaib, Philip S. J.,Lingnau, Julia B.,Goddard, Richard,List, Benjamin
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supporting information
p. 2464 - 2468
(2018/02/06)
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- COBALT COMPLEXES, PROCESS FOR PREPARATION AND USE THEREOF
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The present invention discloses a cobalt compound of formula (I), a process for the preparation and use thereof. The present invention further relates to a pharmaceutical composition and a method inhibition of Tau Aggregation in a subject in need thereof using compound of formula (I).
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Page/Page column 15; 16
(2019/01/06)
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- Lewis acid-mediated reactions of donor-acceptor cyclopropanes with diazo esters
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The reactions of diazo esters with 2-arylcyclopropane-1,1-dicarboxylates, the represen- tatives of donor-acceptor cyclopropanes (DACs), mediated by Sc(OTf)3, SnCl4, and GaCl3 proceeded with nitrogen elimination to give the
- Novikov,Borisov,Tomilov, Yu. V.
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p. 265 - 273
(2018/05/15)
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- Phosphine-free cobalt pincer complex catalyzed: Z -selective semi-hydrogenation of unbiased alkynes
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Herein, we report a novel, molecularly defined NNN-type cobalt pincer complex catalyzed transfer semi-hydrogenation of unbiased alkynes to Z-selective alkenes. This unified process is highly stereo- and chemo-selective and exhibits a broad scope as well as wide functional group tolerance. Ammonia-borane (AB), a bench-stable substrate with high gravimetric hydrogen capacity, was used as a safe and practical transfer hydrogenating source.
- Landge, Vinod G.,Pitchaimani, Jayaraman,Midya, Siba P.,Subaramanian, Murugan,Madhu, Vedichi,Balaraman, Ekambaram
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p. 428 - 433
(2018/02/07)
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- Heck and oxidative boron Heck reactions employing Pd(II) supported amphiphilized polyethyleneimine-functionalized MCM-41 (MCM-41@aPEI-Pd) as an efficient and recyclable nanocatalyst
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A novel nanocatalyst was developed based on covalent surface functionalization of MCM-41 with polyethyleneimine (PEI) using [3-(2,3-Epoxypropoxy)propyl] trimethoxysilane (EPO) as a cross-linker. Amine functional groups on the surface of MCM-41 were then conjugated with iodododecane to render an amphiphilic property to the catalyst. Palladium (II) was finally immobilized onto the MCM-41@PEI-dodecane and the resulted MCM-41@aPEI-Pd nanocatalyst was characterized by FT-IR, TEM, ICP-AES and XPS. Our designed nanocatalyst with a distinguished core-shell structure and Pd2+ ions as catalytic centers was explored as an efficient and recyclable catalyst for Heck and oxidative boron Heck coupling reactions. In Heck coupling reaction, the catalytic activity of MCM-41@aPEI-Pd in the presence of triethylamine as base led to very high yields and selectivity. Meanwhile, the MCM-41@aPEI-Pd as the first semi-heterogeneous palladium catalyst was examined in the C-4 regioselective arylation of coumarin via the direct C-H activation and the moderate to excellent yields were obtained toward different functional groups. Leaching test indicated the high stability of palladium on the surface of MCM-41@aPEI-Pd as it could be recycled for several runs without significant loss of its catalytic activity.
- Motevalizadeh, Seyed Farshad,Alipour, Masoumeh,Ashori, Fatemeh,Samzadeh-Kermani, Alireza,Hamadi, Hosein,Ganjali, Mohammad Reza,Aghahosseini, Hamideh,Ramazani, Ali,Khoobi, Mehdi,Gholibegloo, Elham
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- Light Mediated Preparation of Palladium Nanoparticles as Catalysts for Alkyne cis-Semihydrogenation
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A bisacylphosphine oxide photoinitiator was used for the light mediated preparation of palladium nanoparticles (PdNPs) with a small diameter of 2.8 nm. All starting materials are commercially available, and PdNP synthesis is experimentally very easy to conduct. The PdNP-hybrid material was applied as catalyst for the semihydrogenation of various internal alkynes to provide the corresponding alkenes in excellent yields (up to 99%) and Z-selectivities (Z/E ratios up to 99/1).
- M?sing, Florian,Nüsse, Harald,Klingauf, Jürgen,Studer, Armido
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supporting information
p. 2658 - 2661
(2017/05/24)
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- Controlled hydrogenation of diphenylacetylene using alkylammonium formate
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A simple and straightforward semihydrogenation of alkyne to alkene with triethanolamine and formic acid in the presence of PdCl2 has been described. Although hydrogenation using formic acid as a hydrogenation source has been used in combination with amines previously, few reports are available concerning the associated reactivity. We demonstrated that reactivity changes depending on the type of amine used in the hydrogenation. Further, this reaction requires no strict time control, making it a useful tool in organic synthesis.
- Suzuki, Hideyuki,Satoh, Ikkyu,Nishioka, Hiromi,Takeuchi, Yasuo
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supporting information
p. 3834 - 3837
(2017/09/15)
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- Stereoselective and Site-Specific Allylic Alkylation of Amino Acids and Small Peptides via a Pd/Cu Dual Catalysis
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We report a stereoselective and site-specific allylic alkylation of Schiff base activated amino acids and small peptides via a Pd/Cu dual catalysis. A range of noncoded α,α-dialkyl α-amino acids were easily synthesized in high yields and with excellent enantioselectivities (up to >99% ee). Furthermore, a direct and highly stereoselective synthesis of small peptides with enantiopure α-alkyl or α,α-dialkyl α-amino acids residues incorporated at specific sites was accomplished using this dual catalyst system.
- Huo, Xiaohong,He, Rui,Fu, Jingke,Zhang, Jiacheng,Yang, Guoqiang,Zhang, Wanbin
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supporting information
p. 9819 - 9822
(2017/08/02)
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- Thermally induced N-S bond insertion reaction of diazo compounds with: N -sulfenylsuccinimides: Synthesis of sulfides and mechanism studies
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A metal-free gem-functionalization reaction of diazo compounds with N-sulfenylsuccinimides via a formal N-S bond insertion process has been reported. The transformation features mild reaction conditions, broad substrate scope and functional group tolerance, offering an efficient approach to sulfide synthesis in moderate to high yields. In addition, the mechanism studies indicate the formation of free carbene under thermal conditions followed by ylide generation, then N-S bond cleavage and C-N bond formation occurred in sequence to give the sulfide products.
- Zhang, Xiaolu,Zheng, Yang,Qiu, Lihua,Xu, Xinfang
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supporting information
p. 70 - 76
(2017/12/27)
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- Ligand-free nickel-catalyzed semihydrogenation of alkynes with sodium borohydride: A highly efficient and selective process for: Cis -alkenes under ambient conditions
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We report a low-cost and efficient catalytic system, involving in situ generated ligand-free Ni NPs, methanol and sodium borohydride, for the semihydrogenation of alkynes under ambient conditions. This catalytic system exhibits remarkably high activity, satisfactory cis-selectivity for internal alkynes, good stability and general applicability.
- Wen, Xin,Shi, Xiaozhen,Qiao, Xianliang,Wu, Zhilei,Bai, Guoyi
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supporting information
p. 5372 - 5375
(2017/07/06)
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- Copper(i)-catalysed transfer hydrogenations with ammonia borane
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Highly Z-selective alkyne transfer semihydrogenations and conjugate transfer hydrogenations of enoates can be effected by employing a readily available and air-stable copper(i)/N-heterocyclic carbene (NHC) complex, [IPrCuOH]. As an easy to handle and potentially recyclable H2 source, ammonia borane (H3NBH3) is used.
- Korytiaková, Eva,Thiel, Niklas O.,Pape, Felix,Teichert, Johannes F.
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supporting information
p. 732 - 735
(2017/01/13)
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- Combining visible light catalysis and transfer hydrogenation for in situ efficient and selective semihydrogenation of alkynes under ambient conditions
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By combining visible light catalysis and transfer hydrogenation, we are able to convert a series of alkynes to their corresponding alkenes in high chemical yields. Then the visible light catalytic transfer hydrogenation reaction can couple photoisomerization to produce E-alkenes or Z-alkenes exclusively depending on the aryl or alkyl substituted alkynes.
- Zhong, Jian-Ji,Liu, Qiang,Wu, Cheng-Juan,Meng, Qing-Yuan,Gao, Xue-Wang,Li, Zhi-Jun,Chen, Bin,Tung, Chen-Ho,Wu, Li-Zhu
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supporting information
p. 1800 - 1803
(2016/02/05)
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- Using non-covalent interactions to direct regioselective 2+2 photocycloaddition within a macrocyclic cavitand
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The relative orientation of guests within ternary inclusion complexes is governed by the host-guest and guest-guest supramolecular interactions. Selectivity in 2+2 photocycloaddition between two alkenes included within a macrocyclic cavitand (γ-cyclodextrin) can be controlled using non-covalent interactions. In this manuscript, we report cavitand-mediated control of regioselectivity between alkyl cinnamates using non-covalent interactions. Using this method, we have shown that regioselectivity can be switched completely from a head-to-head dimer to a head-to-tail dimer. The reactions were also stereoselective in most cases. Stoichiometry experiments were performed to explore relative stabilities of the complexes, which indicate that the ternary complex is more stable than others. Selectivity in the photocycloaddition reaction was also applied retrospectively to deduce intermolecular orientations. Time-dependent conversion study we performed indicates that the observed reactivity of alkenes is representative of the intermolecular orientations in the bulk of the complex medium. Experimental observations and computational studies were used to qualitatively understand the complex structures, and relative magnitudes of the weak interactions. The reactions of complexes were studied in slurry form, and the extent of reaction control suggests a solid-state-like behavior.
- Nguyen, Nga,Clements, Aspen Rae,Pattabiraman, Mahesh
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p. 2433 - 2443
(2016/03/19)
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- Copper-catalyzed oxidative olefination of thiols using sulfones and phosphorous ylides
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Copper-catalyzed one-pot conversion of thiols to olefins was conducted under aerobic conditions. Thiols were oxidized to generate thioaldehydes, which reacted with sulfones or phosphorous ylides to form the corresponding olefins. The formation of thiosulfonates and phosphorous sulfides confirms that these olefination protocols proceed via thioaldehyde-sulfone and thioaldehyde-ylide adducts.
- Shyam, Pranab K.,Lee, Chan,Jang, Hye-Young
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supporting information
p. 1824 - 1827
(2015/07/15)
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- Phospholane-catalyzed wittig reaction
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We identified 2-phenylisophosphindoline 2-oxide as a suitable and potentially tunable catalyst for the catalytic Wittig reaction of aldehydes with activated organohalides. This catalyst was obtained by a straightforward two-step synthesis. Trimethoxysilane proved to be an efficient reducing agent for the in situ generation and regeneration of the catalyst from the corresponding phosphane oxide. Sodium carbonate was identified as a suitable base for the transformation. It is noteworthy that the particle size of the sodium carbonate had a tremendous effect on the outcome of the reaction. Under the optimized reaction conditions, 23 aldehydes were converted into the corresponding alkenes in high isolated yields of up to 88%. Moreover, an asymmetric catalytic Wittig reaction was performed for the desymmetrization of a prochiral diketone.
- Werner, Thomas,Hoffmann, Marcel,Deshmukh, Sunetra
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p. 3286 - 3295
(2015/05/20)
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- Scope and Limitation of the Microwave-Assisted Catalytic Wittig Reaction
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We have developed a microwave-assisted catalytic Wittig reaction. In this paper, we give full account of the scope and limitations of this reaction. A screening of various commercially available phosphine oxides as precatalysts revealed Bu3P=O to be the most promising candidate. We tested 10 silanes for the in situ reduction of the phosphine oxide to generate Bu3P as the actual catalyst. Different epoxides were tested as masked bases. In this context, cyclohexene oxide as well as butylene oxide proved to be suitable. The reaction could be carried out at 125 C, but higher yields and E/Z selectivities were obtained at 150 °C. Under the optimised reaction conditions, more than 40 examples for the conversion of various aldehydes into the corresponding alkenes are reported. The products were obtained in yields of up to 88 with high E selectivities. Moreover, we also describe the further screening of several chiral phosphines as catalysts for the microwave-assisted enantioselective catalytic Wittig reaction. The scope and limitations of the microwave-assisted catalytic Wittig reaction have been evaluated with respect to the catalyst, silane, solvent, reaction conditions, and substrates.
- Hoffmann, Marcel,Deshmukh, Sunetra,Werner, Thomas
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p. 4532 - 4543
(2015/07/27)
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- A water-soluble palladium-salen catalyst modified by pyridinium salt showing higher reactivity and recoverability for Heck coupling reaction
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A novel and water-soluble palladium-salen catalyst modified by pyridinium salt was synthesized and characterized by NMR, HRMS, FT-IR, ICP, elemental analysis and UVvis spectroscopy. The catalyst can efficiently catalyze the Heck reaction between aryl halides and olefins. The reaction using 0.5 mol% cat-alyst can achieve 98.3% conversion with 99% selectivity. The catalytic activity of catalyst modified bypyridinium salt is higher than that of un-modified one. Furthermore, the catalyst can be easily separatedfrom reaction system by water wash and subsequently recycled for six runs without significant loss ofactivity and selectivity.
- Yuan, Linghua,Xu, Yun,Hu, Xingbang,Yang, Guoqiang,Wu, Youting
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- A water-soluble palladium-salen catalyst modified by pyridinium salt showing higher reactivity and recoverability for Heck coupling reaction
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A novel and water-soluble palladium-salen catalyst modified by pyridinium salt was synthesized and characterized by NMR, HRMS, FT-IR, ICP, elemental analysis and UV-vis spectroscopy. The catalyst can efficiently catalyze the Heck reaction between aryl halides and olefins. The reaction using 0.5 mol% catalyst can achieve 98.3% conversion with 99% selectivity. The catalytic activity of catalyst modified by pyridinium salt is higher than that of un-modified one. Furthermore, the catalyst can be easily separated from reaction system by water wash and subsequently recycled for six runs without significant loss of activity and selectivity.
- Yuan, Linghua,Xu, Yun,Hu, Xingbang,Yang, Guoqiang,Wu, Youting
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- Convenient transfer semihydrogenation methodology for alkynes using a PdII-NHC precatalyst
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A convenient and easy-to-use protocol for the Z-selective transfer semihydrogenation of alkynes was developed, using ammonium formate as the hydrogen source and the easily prepared and commercially available, highly stable complex PdCl(η3-C3H5)(IMes) (1) as the (pre)catalyst. Combined with triphenyl posphine as an additional ligand, this system provides a robust catalytic synthetic method that shows little to no over-reduction or isomerization after full substrate conversion. The system allows the direct use of solvents and reagents, as received from the supplier without drying or purification, thus providing a practical method for semihydrogenation of a broad range of alkynes. The mechanism behind these high and enhanced selectivities was determined through a set of kinetic experiments.
- Drost, Ruben M.,Bouwens, Tessel,Van Leest, Nicolaas P.,De Bruin, Bas,Elsevier, Cornelis J.
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p. 1349 - 1357
(2014/05/20)
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- Mild synthesis of mesoporous silica supported ruthenium nanoparticles as heterogeneous catalysts in oxidative Wittig coupling reactions
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A new efficient approach for the in situ synthesis of anchored ruthenium nanoparticles (RuNP) in three different kinds of mesoporous silica materials, MCM-41, SBA-15 and HMS, has been developed. Solids have been synthesized under very mild conditions from RuCl3·H2O salt reduced in one hour at room temperature in the mesoporous silicas previously grafted with aminopropyltriethoxysilane (APTES). Well-dispersed ruthenium nanoparticles, with an average size of 3 nm, anchored into the silica network by the APTES were obtained. These materials, with a molar ratio of Si/Ru = 40, were found to be catalytically active and selective in the alcohol oxidation-Wittig olefination. Interestingly, while the reaction occurs from the alcohol, control experiments suggest that the aldehyde (the common Wittig substrate) is not involved. The Royal Society of Chemistry.
- Carrillo, Adela I.,Schmidt, Luciana C.,Marin, M. Luisa,Scaiano, Juan C.
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supporting information
p. 435 - 440
(2014/02/14)
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- Stereoselective iron-catalyzed alkyne hydrogenation in ionic liquids
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Iron(0) nanoparticles in ionic liquids (ILs) have been shown to catalyse the semi-hydrogenation of alkynes. In the presence of a nitrile-functionalised IL or acetonitrile, stereoselective formation of (Z)-alkenes was observed. The biphasic solvent system allowed facile separation and re-use of the catalyst. The Royal Society of Chemistry 2014.
- Gieshoff, Tim N.,Welther, Alice,Kessler, Michael T.,Prechtl, Martin H.G.,Jacobi Von Wangelin, Axel
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supporting information
p. 2261 - 2264
(2014/03/21)
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- Green semi-hydrogenation of alkynes by Pd@borate monolith catalysts under continuous flow
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Palladium nanoparticles were immobilized onto an unconventional polymeric borate macroporous monolith and the resulting mesoreactor (i.d. 3 mm, length 25 mm) used in liquid-phase catalytic semi-hydrogenation reaction of substituted alkynes under continuous flow. The catalytic system showed excellent efficiency, both in terms of activity and selectivity, and long-term stability under mild reaction conditions (methanol, room temperature, 1.5 bar H2 max), with no need of additives. Particularly, the leaf alcohol cis-3-hexen-1-ol was for the first time obtained with selectivity comparable to that of the industrial batch process. The performance of the catalyst is discussed and compared with those of the analogous batch and industrial processes.
- Liguori, Francesca,Barbaro, Pierluigi
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p. 212 - 220
(2014/01/17)
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- METHODS FOR PHOSPHINE OXIDE REDUCTION IN CATALYTIC WITTIG REACTIONS
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A method for increasing the rate of phosphine oxide reduction, preferably during a Wittig reaction comprising use of an acid additive is provided. A room temperature catalytic Wittig reaction (CWR) the rate of reduction of the phosphine oxide is increased due to the addition of the acid additive is described. Furthermore, the extension of the CWR to semi-stabilized and non-stabilized ylides has been accomplished by utilization of a masked base and/or ylide-tuning.
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Page/Page column 34; 35
(2014/09/29)
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- First Microwave-Assisted Catalytic Wittig Reaction
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We introduce a novel catalytic Wittig reaction based on an inexpensive and readily available phosphane oxide as a precatalyst. The performance of the reaction under microwave irradiation led to significantly improved yields and reaction rates relative to those obtained under conventional heating. Moreover, herein we enclose the first example of the asymmetric catalytic Wittig reaction based on a chiral phosphane as the catalyst.
- Werner, Thomas,Hoffmann, Marcel,Deshmukh, Sunetra
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supporting information
p. 6873 - 6876
(2016/02/19)
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- Stabilized wittig olefination for bioconjugation
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Stabilized Wittig olefination holds great potential as a bioconjugation reaction. We demonstrate that the reaction of stabilized phosphorus ylides (or phosphonium salts) with aryl aldehydes is sufficiently robust to be used for live cell affinity isolation and fluorescence tagging of a protein, FKBP12.
- Lum, Kenneth M.,Xavier, Vanessa J.,Ong, Michelle J.-H.,Johannes, Charles W.,Chan, Kok-Ping
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supporting information
p. 11188 - 11190
(2013/11/19)
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- Photodimerization of hydrophobic guests within a water-soluble nanocapsule
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Conducting reactions in environmentally benign conditions is one of the major objectives of "green chemistry." In this context, developing ways to conduct reactions in water seems obvious. In this report, we present our results on photodimerization of sel
- Parthasarathy, Anand,Samanta, Shampa R.,Ramamurthy
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- Part I: The development of the catalytic wittig reaction
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We have developed the first catalytic (in phosphane) Wittig reaction (CWR). The utilization of an organosilane was pivotal for success as it allowed for the chemoselective reduction of a phosphane oxide. Protocol optimization evaluated the phosphane oxide precatalyst structure, loading, organosilane, temperature, solvent, and base. These studies demonstrated that to maintain viable catalytic performance it was necessary to employ cyclic phosphane oxide precatalysts of type 1. Initial substrate studies utilized sodium carbonate as a base, and further experimentation identified N,N-diisopropylethylamine (DIPEA) as a soluble alternative. The use of DIPEA improved the ease of use, broadened the substrate scope, and decreased the precatalyst loading. The optimized protocols were compatible with alkyl, aryl, and heterocyclic (furyl, indolyl, pyridyl, pyrrolyl, and thienyl) aldehydes to produce both di- and trisubstituted olefins in moderate-to-high yields (60-96 %) by using a precatalyst loading of 4-10 mol %. Kinetic E/Z selectivity was generally 66:34; complete E selectivity for disubstituted α,β-unsaturated products was achieved through a phosphane-mediated isomerization event. The CWR was applied to the synthesis of 54, a known precursor to the anti-Alzheimer drug donepezil hydrochloride, on a multigram scale (12.2 g, 74 % yield). In addition, to our knowledge, the described CWR is the only transition-/heavy-metal-free catalytic olefination process, excluding proton-catalyzed elimination reactions. A point of difference: By utilizing an organosilane to chemoselectively reduce a phosphane oxide precatalyst to a phosphane (see scheme), the first catalytic (in phosphane) Wittig reaction has been developed. The methodology has been applied to the synthesis of 22 disubstituted and 24 trisubstituted olefins, including a multigram synthesis of a precursor to the anti-Alzheimer drug donepezil hydrochloride.
- O'Brien, Christopher J.,Nixon, Zachary S.,Holohan, Andrew J.,Kunkel, Stephen R.,Tellez, Jennifer L.,Doonan, Bryan J.,Coyle, Emma E.,Lavigne, Florie,Kang, Lauren J.,Przeworski, Katherine C.
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p. 15281 - 15289
(2013/11/06)
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- Breaking the ring through a room temperature catalytic wittig reaction
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One ring no longer rules them all: Employment of 2.5-10 mol % of 4-nitrobenzoic acid with phenylsilane led to the development of a room temperature catalytic Wittig reaction (see scheme). Moreover, these enhanced reduction conditions also facilitated the use of acyclic phosphine oxides as catalysts for the first time. A series of alkenes were produced in moderate to high yield and selectivity. Copyright
- O'Brien, Christopher J.,Lavigne, Florie,Coyle, Emma E.,Holohan, Andrew J.,Doonan, Bryan J.
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supporting information
p. 5854 - 5858
(2013/06/27)
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- Palladium chloride catalyzed photochemical Heck reaction
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PdCl2 catalyzed carbon-carbon bond formation (Heck reaction) between substituted aryl halides and olefins was carried out without a ligand, under irradiation with UV-visible light. The results demonstrated that UV-visible light accelerated the rate of the reaction, leading to an excellent yield of corresponding products. The recovered palladium nanoparticles could be thermally recycled several times. PdCl2 gave excellent conversion up to the fifth addition of substrate.
- Waghmode, Suresh B.,Arbuj, Sudhir S.,Wani, Bina N.,Gopinath
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supporting information
p. 348 - 351
(2013/06/04)
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- Calix[4]arene based 1,3,4-oxadiazole and thiadiazole derivatives: Design, synthesis, and biological evaluation
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In the present investigation, we describe some novel calixarene based heterocyclic compounds (5a-5i) in which 1,3,4-oxadiazole and 1,3,4-thiadiazole derivatives have been coupled with 5,11,17,23-tetra-tert-butyl-25,27- bis(chlorocarbonyl-methoxy)-26,28-dihydroxy calix[4]arene. All the newly synthesized calixarene based heterocyclic compounds have been characterized by elemental analysis and various spectroscopic methods like FTIR, 1H NMR, 13C NMR, and FAB-MS. All the final scaffolds have been subjected to antioxidant activity, in vitro antimicrobial screening against two gram (+ve) bacteria (S. aureus, S. pyogenes), two gram (-ve) bacteria (E. coli, P. aeruginosa) and two fungal strains (C. albicans, A. clavatus) and also have been screened for their antitubercular activity against Mycobacterium tuberculosis H37Rv.
- Patel, Manishkumar B.,Modi, Nishith R.,Raval, Jignesh P.,Menon, Shobhana K.
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body text
p. 1785 - 1794
(2012/04/23)
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- Unequivocal experimental evidence for a unified lithium salt-free wittig reaction mechanism for all phosphonium ylide types: Reactions with β-heteroatom-substituted aldehydes are consistently selective for cis-oxaphosphetane-derived products
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The true course of the lithium salt-free Wittig reaction has long been a contentious issue in organic chemistry. Herein we report an experimental effect that is common to the Wittig reactions of all of the three major phosphonium ylide classes (non-stabilized, semi-stabilized, and stabilized): there is consistently increased selectivity for cis-oxaphosphetane and its derived products (Z-alkene and erythro-β-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the β-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde. The discovery of an effect that is common to reactions of all ylide types strongly argues for the operation of a common mechanism in all Li salt-free Wittig reactions. In addition, the results are shown to be most easily explained by the [2+2] cycloaddition mechanism proposed by Vedejs and co-workers as supplemented by Aggarwal, Harvey, and co-workers, thus providing strong confirmatory evidence in support of that mechanism. Notably, a cooperative effect of ortho-substituents in the case of semi-stabilized ylides is confirmed and is accommodated by the cycloaddition mechanism. The effect is also shown to operate in reactions of triphenylphosphine-derived ylides and has previously been observed for reactions under aqueous conditions, thus for the first time providing evidence that kinetic control is in operation in both of these cases.
- Byrne, Peter A.,Gilheany, Declan G.
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p. 9225 - 9239
(2012/07/14)
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- Novel photolabile diblock copolymers bearing truxillic acid derivative junctions
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Amphiphilic diblock copolymers, poly(ethylene glycol)-block-poly(acrylate), bearing truxillic acid derivatives at the junction point between the two blocks are described. The truxillic acid junction can be selectively cut by UV light, leading to a disassembly of the nano-objects made by self-assembly of the amphiphilic copolymers in water.
- Yang, Hong,Jia, Lin,Wang, Zhifei,Di-Cicco, Aurelie,Levy, Daniel,Keller, Patrick
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scheme or table
p. 159 - 165
(2012/01/30)
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