- Miscibility and hydrogen bonding in blends of poly(ethylene oxide) and kraft lignin
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Polymer blending is a convenient method to develop products with desirable properties. Through specific intermolecular interactions favorable polymer blending can occur, and composite materials with desirable properties can be produced. In this study we h
- Kadla, John F.,Kubo, Satoshi
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- Supramolecular assembly and transfer hydrogenation catalysis with ruthenium(II) complexes of 2,6-di(1H-pyrazol-3-yl)pyridine derivatives
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Two new tridentate ligands 2,6-bis(5-ethyl-1H-pyrazol-3-yl)pyridine and 2,6-bis(5-benzamido-1H-pyrazol-3-yl)pyridine, have been synthesized. These ligands have been used in a new series of six complexes of formula "RuCl2(PPh3)2
- Roberts, Thomas D.,Halcrow, Malcolm A.
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- Nickel-Catalyzed Enantioselective Hydroboration of Vinylarenes
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The enantioselective hydroboration of vinylarenes catalyzed by a chiral, nonracemic nickel catalyst is presented as a facile method for generating chiral benzylic boronate esters. Various vinylarenes react with bis(pinacolato)diboron (B2pin2) in the presence of MeOH as a hydride source to form chiral boronate esters in up to 92% yield with up to 94% ee. The use of anhydrous Me4NF to activate B2pin2 is crucial for ensuring fast transmetalation to achieve high enantioselectivities.
- Tran, Hai N.,Stanley, Levi M.
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supporting information
p. 395 - 399
(2021/12/27)
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- Photoacid-Enabled Synthesis of Indanes via Formal [3 + 2] Cycloaddition of Benzyl Alcohols with Olefins
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An environmentally friendly and highly diastereoselective method for synthesizing indanes has been developed via a metastable-state photoacid system containing catalytic protonated merocyanine (MEH). Under visible-light irradiation, MEH yields a metastable spiro structure and liberated protons, which facilitates the formation of carbocations from benzyl alcohols, thus delivering diverse molecules in the presence of various nucleophiles. Mainly, a variety of indanes could be easily obtained from benzyl alcohols and olefins, and water is the only byproduct.
- Yang, Biao,Dong, Kui,Li, Xiang-Sheng,Wu, Li-Zhu,Liu, Qiang
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supporting information
p. 2040 - 2044
(2022/03/17)
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- Ambient-pressure highly active hydrogenation of ketones and aldehydes catalyzed by a metal-ligand bifunctional iridium catalyst under base-free conditions in water
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A green, efficient, and high active catalytic system for the hydrogenation of ketones and aldehydes to produce corresponding alcohols under atmospheric-pressure H2 gas and ambient temperature conditions was developed by a water-soluble metal–ligand bifunctional catalyst [Cp*Ir(2,2′-bpyO)(OH)][Na] in water without addition of a base. The catalyst exhibited high activity for the hydrogenation of ketones and aldehydes. Furthermore, it was worth noting that many readily reducible or labile functional groups in the same molecule, such as cyan, nitro, and ester groups, remained unchanged. Interestingly, the unsaturated aldehydes can be also selectively hydrogenated to give corresponding unsaturated alcohols with remaining C=C bond in good yields. In addition, this reaction could be extended to gram levels and has a large potential of wide application in future industrial.
- Wang, Rongzhou,Yue, Yuancheng,Qi, Jipeng,Liu, Shiyuan,Song, Ao,Zhuo, Shuping,Xing, Ling-Bao
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- Alkylation of monomeric, dimeric, and polymeric lignin models through carbon-hydrogen activation using Ru-catalyzed Murai reaction
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In this study, we have assessed directed carbon-hydrogen activation (CHA) for alkylation of monomeric, dimeric, and polymeric lignin models using Murai's catalyst [RuH2(CO)(PPh3)3]. Based on related work from our laboratory showing that isolated organosolv lignin bears benzylic directing groups ideal for CHA reactions, this approach could offer new methodology for the valorization of biorefinery lignin. Monomeric and dimeric models bearing a keto group at the benzylic position undergo Ru-catalyzed alkylation in good to excellent yield. Similarly, models bearing a benzylic OH group also undergo alkylation via a tandem oxidation/alkylation process enabled by the Ru catalyst. Polymeric models show low levels of functionalization as a result of the poor solubility of the starting polymer. With unsymmetrical models, functionalization occurs first at the least sterically hindered ortho-site, but a subsequent alkylation, leading to disubstituted products can occur at the more sterically hindered site, leading to hexasubstituted arenes. The reaction shows sensitivity to free phenolic OH groups, which appears to reduce the yield in some reactions, and is also a contributing factor to the low yields observed with polymeric lignin models. Combining CHA methodology with lignin isolation technology able to introduce appropriate directing groups for catalytic functionalization will form the basis for improved conversion of lignin to high value chemical products.
- Zuleta, Ernesto C.,Bozell, Joseph J.
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- Highly efficient Meerwein-Ponndorf-Verley reductions over a robust zirconium-organoboronic acid hybrid
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The Meerwein-Ponndorf-Verley (MPV) reaction is an attractive approach to selectively reduce carbonyl groups, and the design of advanced catalysts is the key for these kinds of interesting reactions. Herein, we fabricated a novel zirconium organoborate using 1,4-benzenediboronic acid (BDB) as the precursor for MPV reduction. The prepared Zr-BDB had excellent catalytic performance for the MPV reduction of various biomass-derived carbonyl compounds (i.e., levulinate esters, aldehydes and ketones). More importantly, the number of borate groups on the ligands significantly affected the catalytic activity of the Zr-organic ligand hybrids, owing to the activation role of borate groups on hydroxyl groups in the hydrogen source. Detailed investigations revealed that the excellent performance of Zr-BDB was contributed by the synergetic effect of Zr4+and borate. Notably, this is the first work to enhance the activity of Zr-based catalysts in MPV reactions using borate groups.
- Song, Jinliang,Hua, Manli,Huang, Xin,Visa, Aurelia,Wu, Tianbin,Fan, Honglei,Hou, Minqiang,Zhang, Zhaofu,Han, Buxing
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p. 1259 - 1265
(2021/02/26)
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- Selective Carbon-Carbon Bond Amination with Redox-Active Aminating Reagents: A Direct Approach to Anilines?
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Amines are among the most fundamental motifs in chemical synthesis, and the introduction of amine building blocks via selective C—C bond cleavage allows the construction of nitrogen compounds from simple hydrocarbons through direct skeleton modification. Herein, we report a novel method for the preparation of anilines from alkylarenes via Schmidt-type rearrangement using redox-active amination reagents, which are easily prepared from hydroxylamine. Primary amines and secondary amines were prepared from corresponding alkylarenes or benzyl alcohols under mild conditions. Good compatibility and valuable applications of the transformation were also displayed.
- Qiu, Xu,Wang, Yachong,Su, Lingyu,Jin, Rui,Song, Song,Qin, Qixue,Li, Junhua,Zong, Baoning,Jiao, Ning
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supporting information
p. 3011 - 3016
(2021/09/13)
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- Sequential Cleavage of Lignin Systems by Nitrogen Monoxide and Hydrazine
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The cleavage of representative lignin systems has been achieved in a metal-free two-step sequence first employing nitrogen monoxide for oxidation followed by hydrazine for reductive C?O bond scission. In combining nitrogen monoxide and lignin, the newly developed valorization strategy shows the particular feature of starting from two waste materials, and it further exploits the attractive conditions of a Wolff-Kishner reduction for C?O bond cleavage for the first time. (Figure presented.).
- Altmann, Lisa-Marie,Heinrich, Markus R.,Hofmann, Dagmar,Hofmann, Laura Elena,Prusko, Lea
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supporting information
(2020/03/27)
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- A facile and highly efficient transfer hydrogenation of ketones and aldehydes catalyzed by palladium nanoparticles supported on mesoporous graphitic carbon nitride
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A novel transfer hydrogenation methodology for the reduction of ketones (14 examples) and benzaldehyde derivatives (12 examples) to the corresponding alcohols using Pd nanoparticles supported on mesoporous graphitic carbon nitride (mpg-C3N4/Pd) as a reusable catalyst and ammonia borane as a safe hydrogen source in an aqueous solution MeOH/H2O (v/v = 1/1) is described. The catalytic hydrogenation reactions were conducted in a commercially available high-pressure glass tube at room temperature, and the corresponding alcohols were obtained in high yields in 2–5 min. Moreover, the presented transfer hydrogenation protocol shows partial halogen selectivity with bromo-, fluoro-, and chloro-substituted carbonyl analogs. In addition, the present catalyst can be reused up to five times without losing its efficiency, and scaling-up the reaction enables α-methylbenzyl alcohol to be produced in 90% isolated yield.
- Ni?anc?, Bilal,Da?alan, Ziya
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- Hydrothermal Liquefaction of α-O-4 Aryl Ether Linkages in Lignin
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By using lignin model compounds with relevant key characteristic structural features, the reaction pathways of α-O-4 aryl ether linkages under hydrothermal conditions are elucidated. Experimental results and computational modeling suggest that the α-O-4 linkages in lignin undergo catalyzed hydrolysis and elimination to give phenolic and alkenylbenzene derivatives as major products in subcritical water. The decreased relative permittivity of water at these high temperatures and pressures facilitates the elimination reactions. The alkyl group on the α-carbon and the methoxy groups on the phenyl rings both have positive effects on the rate of conversion of α-O-4 linkages in native lignin.
- Lui, Matthew Y.,Chan, Bun,Yuen, Alexander K. L.,Masters, Anthony F.,Maschmeyer, Thomas
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p. 2002 - 2006
(2020/03/05)
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- Monodisperse CuPt alloy nanoparticles assembled on reduced graphene oxide as catalysts in the transfer hydrogenation of various functional organic groups
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We present herein a new nanocatalyst, namely binary CuPt alloy nanoparticles (NPs) supported on reduced graphene oxide (CuPt-rGO), as a highly active heterogeneous catalyst for the transfer hydrogenation (TH) protocol that is demonstrated to be applicable over the reduction of various unsaturated organic compounds (olefins, aldehydes/ketones and nitroarenes) in aqueous solutions at room temperature. CuPt alloy NPs were synthesized by the co-reduction of metal (II) acetylacetonates by borane-tert-butylamine (BTB) complex in hot oleylamine (OAm) solution and then assembled on reduced graphene oxide (rGO) via ultrasonic-assisted liquid phase self-assembly method. The structure of yielded CuPt NPs and CuPt-rGO nanocatalyst were characterized by TEM, XRD and ICP-MS. The activity of Cu7Pt3-rGO nanocatalysts were then tested for the THs that were conducted in a commercially available high-pressure tube using water as sole solvent and ammonia borane as a hydrogen donor at room temperature. The presented catalytic TH protocol was successfully applied over nitroarenes, olefines and aldehydes/ketones, and all the tested compounds were converted to corresponding reduction products with the yields reaching up to 99% under ambient conditions. Moreover, the Cu7Pt3-rGO nanocatalyst was also reusable in the TH by providing 99% yield after five consecutive runs in TH of nitrobenzene as an example.
- Ganjehyan, Khadijeh,Ni?anc?, Bilal,Sevim, Melike,Da?tan, Arif,Metin, ?nder
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- Stepwise degradation of hydroxyl compounds to aldehydes: Via successive C-C bond cleavage
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Stepwise degradation of hydroxyl compounds to aldehydes via successive cleavage of C-C bonds was achieved by using a bimetallic catalytic system (PdCl2 + CuCl) without any ligands and additives. The broad applicability is expanded to a diverse range of aromatic, aliphatic, primary and secondary alcohols, as well as lignin model compounds.
- Liu, Mingyang,Zhang, Zhanrong,Shen, Xiaojun,Liu, Huizhen,Zhang, Pei,Chen, Bingfeng,Han, Buxing
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supporting information
p. 925 - 928
(2019/01/24)
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- Hydrosilylation of carbonyl and carboxyl groups catalysed by Mn(i) complexes bearing triazole ligands
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Manganese(i) complexes bearing triazole ligands are reported as catalysts for the hydrosilylation of carbonyl and carboxyl compounds. The desired reaction proceeds readily at 80 °C within 3 hours at catalyst loadings as low as 0.25 to 1 mol%. Hence, good to excellent yields of alcohols could be obtained for a wide range of substrates including ketones, esters, and carboxylic acids illustrating the versatility of the metal/ligand combination.
- Martínez-Ferraté, Oriol,Chatterjee, Basujit,Werlé, Christophe,Leitner, Walter
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p. 6370 - 6378
(2019/11/20)
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- Nitrogen Dioxide Catalyzed Aerobic Oxidative Cleavage of C(OH)–C Bonds of Secondary Alcohols to Produce Acids
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Stable organic nitroxyl radicals are an important class of catalysts for oxidation reactions, but their wide applications are hindered by their steric hinderance, high cost, complex operation, and separation procedures. Herein, NO2 in DMSO is shown to effectively catalyze the aerobic oxidative cleavage of C(OH)?C bonds to form a carboxylic group, and NO2 was generated in situ by decomposition of nitrates. A diverse range of secondary alcohols were selectively converted into acids in excellent yields in this transition-metal-free system without any additives. Preliminary results also indicate its applicability to depolymerize recalcitrant macromolecular lignin. Detail studies revealed that NO2 from nitrates promoted the reaction, and NO2 served as hydrogen acceptor and radical initiator for the tandem oxidative reaction.
- Liu, Mingyang,Zhang, Zhanrong,Song, Jinliang,Liu, Shuaishuai,Liu, Huizhen,Han, Buxing
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supporting information
p. 17393 - 17398
(2019/11/11)
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- Selective C-O Bond Cleavage of Lignin Systems and Polymers Enabled by Sequential Palladium-Catalyzed Aerobic Oxidation and Visible-Light Photoredox Catalysis
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Lignin, which is a highly cross-linked and irregular biopolymer, is nature's most abundant source of aromatic compounds and constitutes an attractive renewable resource for the production of aromatic commodity chemicals. Herein, we demonstrate a practical and operationally simple two-step degradation approach involving Pd-catalyzed aerobic oxidation and visible-light photoredox-catalyzed reductive fragmentation for the chemoselective cleavage of the β-O-4 linkage - the predominant linkage in lignin - for the generation of lower-molecular-weight aromatic building blocks. The developed strategy affords the β-O-4 bond cleaved products with high chemoselectivity and in high yields, is amenable to continuous flow processing, operates at ambient temperature and pressure, and is moisture- and oxygen-tolerant.
- Magallanes, Gabriel,K?rk?s, Markus D.,Bosque, Irene,Lee, Sudarat,Maldonado, Stephen,Stephenson, Corey R. J.
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p. 2252 - 2260
(2019/02/19)
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- Heterogenization of cobalt nanoparticles on hollow carbon capsules: Lab-in-capsule for catalytic transfer hydrogenation of carbonyl compounds
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Incorporation of cobalt nanoparticles (Co NPs) in porous iron oxide nanospheres (Fe3O4 NSs) templated, glucose derived hollow carbon capsules (HCCs), with an objective to achieve activity and stability simultaneously, facilitates higher catalytic activity of Co NPs in transfer hydrogenation of ketones and aldehydes. A variety of ketones and aldehydes are hydrogenated successfully with excellent yields and high turnover number (TON). This system constitutes one of the most general, heterogeneous, highly stable catalyst, which does not require additives for activation and employs mild reaction conditions. Other significant advantages are low Co content (0.38 mol%) for a catalytic hydrogenation reaction, functional-group tolerance, inexpensive, environmentally benign nature and reusability.
- Kumar, Basuvaraj Suresh,Amali, Arlin Jose,Pitchumani, Kasi
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p. 153 - 161
(2018/03/01)
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- Aminotriazole Mn(I) Complexes as Effective Catalysts for Transfer Hydrogenation of Ketones
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A catalytic system based on complexes comprising abundant and cheap manganese together with readily available aminotriazole ligands is reported. The new Mn(I) complexes are catalytically competent in transfer hydrogenation of ketones with 2-propanol as hydrogen source. The reaction proceeds under mild conditions at 80 °C for 20 h with 3 % of catalyst loading using either KOtBu or NaOH as base. Good to excellent yields were obtained for a wide substrate scope with broad functional group tolerance. The obtained results by varying the substitution pattern of the ligand are consistent with an out-sphere mechanism for the H-transfer.
- Martínez-Ferraté, Oriol,Werlé, Christophe,Franciò, Giancarlo,Leitner, Walter
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p. 4514 - 4518
(2018/10/20)
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- Aryl appended neutral and cationic half-sandwich ruthenium(II)-NHC complexes: Synthesis, characterisation and catalytic applications
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Half-sandwich ruthenium(ii) complexes 1-6 bearing imidazolylidene and pyridyl-imidazolylidene ligands have been synthesised in good yields and were characterised on the basis of spectral and analytical evidence. In addition, the structures of the complexes 1-4 were unambiguously established through single crystal X-ray analysis. Transmetalation of the ligands followed by complexation with ruthenium precursors yielded the air and moisture stable complexes. The crystal structures of these complexes exhibited piano-stool geometries with η6-coordination of the p-cymene or hexamethylbenzene moieties. These complexes exhibited catalytic activity in the transfer hydrogenation of carbonyls in an alkaline medium using 2-propanol as the hydrogen source. The effect of variations in the catalyst structure on the transfer hydrogenation and stability was investigated in detail, and theoretical calculations were employed to understand the mechanism of the catalytic activity. The neutral ruthenium-NHC complexes 1 and 2 showed the efficiency of ca. 100% at a catalyst loading of ca. 2 mol% within 2 h of the reaction in 2-propanol, whereas quantitative yields were obtained in the presence of cationic ruthenium-NHC complexes 3-6 within 1 h at a low catalyst loading of ca. 0.5 mol%, thereby demonstrating their robustness for the transfer hydrogenation of the aromatic ketones.
- Viji, Mambattakkara,Tyagi, Nidhi,Naithani, Neeraj,Ramaiah, Danaboyina
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p. 12736 - 12745
(2017/11/06)
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- Selective Oxidation of Aromatic Olefins Catalyzed by Copper(II) Complex in Micellar Media
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Abstract: The selective oxidation of aromatic olefins 1,2-dimethoxy-4-vinylbenzene (DEVB) and 2-methoxy-4-vinylphenol (MOVP) by H2O2 into 1-(3,4-dime-thoxyphenyl)ethanol (MVA) and 1-(4-hydroxy-3-methoxyphenyl)ethanol (HMOPE) catalyzed by copper(II) complex CuL (L = 6,8,15,17-tetramethyl-7,16-dihydrodibenzo-1,4,8,11-tetraazacyclotetradecine) were achieved in cationic surfactant cetyl trimethylammonium bromide (CTAB), anionic surfactant sodium dodecyl benzene sulfonate (SDBS) and nonionic surfactant Triton X-100 (TX-100) micellar media, respectively. Micelle showed great influence on both reaction rate and selectivity of product. Aromatic olefins could be oxidized into corresponding aromatic ketones in aqueous solution, but into secondary alcohols in micellar media. The combination of TEMPO and CuL/H2O2 resulted in relatively fast reaction rate and S > 96% selectivity of aromatic ketones. The reaction rate constants, k1, k2 and k3 for three oxidation reactions pathways: olefin to ketone, olefin to alcohol and alcohol to ketone were obtained, respectively. The kinetic study indicated that the CuL catalyzed oxidation of olefins by H2O2 to alcohols was a relatively rapid and major reaction and ketone was generated by the direct oxidation of olefins, not by further oxidation of alcohol in micellar media. Graphical Abstract: [Figure not available: see fulltext.].
- Li, Xiao-Hong,Mi, Chun,Liao, Xiao-Hong,Meng, Xiang-Guang
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p. 2508 - 2514
(2017/09/06)
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- Efficient and recyclable Ru(II) arene thioamide catalysts for transfer hydrogenation of ketones: Influence of substituent on catalytic outcome
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Six cationic ruthenium(II) arene thioamide complexes with the general molecular formula [Ru(η6-p-cymene)(PPh3)(L)]+ [where, L = pyridine-2-thioamide and its derivatives] have been successfully synthesized from the reaction of [Ru(η6-p-cymene)Cl2]2 with chelating thioamide ligands and PPh3 in methanol in 1:2 M ratio respectively. All the complexes were isolated as their BPh4?salts and were fully characterized by analytical and spectral (FT-IR, UV-Vis and1H-NMR) methods. The solid-state structure of one of the complexes, [Ru(η6-p-cymene)(PPh3)(L4)]BPh4 (4) (L4 = N-(2, 4, 6-Trimethylphenyl)pyridine-2-thiocarboxamide) has been established by X-ray single crystal diffraction which indicates a pseudo-octahedral (piano-stool) coordination geometry is present in the complex. The ruthenium(II) complexes have been examined for the transfer hydrogenation of various aromatic, heterocycle and cyclic ketones. The formation of ruthenium(II) hydride is confirmed by 1H- NMR and is proposed as the catalytic intermediate in this reaction. Under the optimized conditions, these ruthenium complexes served as excellent catalyst precursors which smoothly reduce the ketones with conversion up to 100%. The influence of other variables on the transfer hydrogenation reaction such as solvent, base, temperature, time, catalyst loading and substrate scope is also reported. Furthermore, the catalyst could be easily recovered and reused at least three times without obvious loss of conversions.
- Kanchanadevi, Appukutti,Ramesh, Rengan,Semeril, David
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- Selective acetylation of primary alcohols by ethyl acetate
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A KOtBu and ethyl acetate mediated efficient methodology has been developed for the acetylation of primary and secondary alcohols where ethyl acetate is the source of acetyl group. The reaction is fast, mild, efficient, and highly selective towards the primary alcohols.
- Singha, Raju,Ray, Jayanta K.
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supporting information
p. 5395 - 5398
(2016/11/11)
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- Highly selective direct azidation of alcohols over a heterogeneous povidone-phosphotungstic solid acid catalyst
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A simple protocol for the selective azidation of alcohols is developed using a solid acid hybrid of a povidone and phosphotungstic acid (PVP-PWA) using azidotrimethylsilane as an azide source at room temperature. In a broad substrate scope, various activated as well as unactivated benzylic and diphenyl alcohols were treated smoothly with TMS-N3 to selectively produce only azide products with excellent yields in a very short reaction time of 2 h. FT-IR confirmed the stability of the catalyst with retention of the Keggins structure after the reaction. Recycling experiments demonstrated the reusability of the PVP-PWA (3?:?1) several times without losing its original activity.
- Kamble, Sumit,More, Sagar,Rode, Chandrashekhar
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supporting information
p. 10240 - 10245
(2016/12/06)
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- SYNTHESIS OF AMIDES AND AMINES FROM ALDEHYDES OR KETONES BY HETEROGENEOUS METAL CATALYSIS
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This invention concerns the first mild and efficient synthesis of primary amines and amides from aldehydes or ketones using a heterogeneous metal catalystand amine donor. The initial heterogeneous metal- catalyzed reaction between the carbonyl and the amine donor components is followed up with the addition of a suitable acylating agent component in one-pot. Hence, the present invention provides a novel catalytic one-pot three-component synthesis of amides. Moreover, the integration of enzyme catalysis allows for eco-friendly one-pot co-catalytic synthesis ofamides from aldehyde and ketone substrates, respectively. The process can be applied to the co-catalytic one-pot three-component synthesis of capsaicin and its analogues from vanillin or vanillyl alcohol. It can also be applied for asymmetric synthesis. In the present invention, a novel co-catalytic reductive amination/dynamic kinetic resolution (dkr) relay sequence for the asymmetric synthesis of optically active amides from ketones is disclosed. Moreover, implementation of a catalytic reductive amination/kinetic resolution (kr) relay sequence produces the corresponding optically active amide product and optical active primary amine product with the opposite stereochemistry from the starting ketones.
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Page/Page column 22
(2016/07/05)
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- Stable and easily handled FeIII catalysts for hydrosilylation of ketones and aldehydes
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The amine-bis(phenolate) iron(III)-catalysed reduction of ketones and aldehydes to the corresponding secondary and primary alcohols by a consecutive hydrosilylation/hydrolysis process is reported. The amine-bis(phenolate) iron(III) catalyst is easily accessible, stable towards moisture and air and has a broad substrate scope.
- Zhu, Kailong,Shaver, Michael P.,Thomas, Stephen P.
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supporting information
p. 2119 - 2123
(2015/03/31)
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- Using fluorogenic probes for the investigation of selective biomass degradation by fungi
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A library of fifteen commercially purchased and synthetic fluorogenic probes was employed for the investigation of biomass degradation using extracts of white-rot fungi. These probes were selected or designed to mimic the dominant linkages in celluloses, hemicelluloses, and lignin, the three most abundant polymers found in biomass. The results show that white-rot fungi display a high preference for cleaving mannose- and glucose-based probes, which mimic hemicelluloses. Low degrees of cleavages were noted for xylose- and cellobiose-based probes. No cleavages were observed for probes that mimic the linkages in lignin. Overall, these discoveries prove that it is possible to employ fungi for selective degradation or release of hemicelluloses from biomass.
- Zhang, Qian,Peng, Xinrui,Grilley, Michelle,Takemoto, Jon Y.,Chang, Cheng-Wei Tom
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p. 1918 - 1925
(2015/03/18)
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- A Highly Active and Easily Accessible Cobalt Catalyst for Selective Hydrogenation of C=O Bonds
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The substitution of high-price noble metals such as Ir, Ru, Rh, Pd, and Pt by earth-abundant, inexpensive metals like Co is an attractive goal in (homogeneous) catalysis. Only two examples of Co catalysts, showing efficient C=O bond hydrogenation rates, are described. Here, we report on a novel, easy-to-synthesize Co catalyst family. Catalyst activation takes place via addition of 2 equiv of a metal base to the cobalt dichlorido precatalysts. Aldehydes and ketones of different types (dialkyl, aryl-alkyl, diaryl) are hydrogenated quantitatively under mild conditions partially with catalyst loadings as low as 0.25 mol%. A comparison of the most active Co catalyst with an Ir catalyst stabilized by the same ligand indicates the superiority of Co. Unique selectivity toward C=O bonds in the presence of C=C bonds has been observed. This selectivity is opposite to that of existing Co catalysts and surprising because of the directing influence of a hydroxyl group in C=C bond hydrogenation.
- R?sler, Sina,Obenauf, Johannes,Kempe, Rhett
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supporting information
p. 7998 - 8001
(2015/07/08)
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- One-pot synthesis of indene derivatives by CF3SO 3H-promoted reactions of benzylic alcohols and 1,3-dicarbonyl compounds
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An efficient and convenient one-pot synthesis of indene derivatives was achieved in moderate to high yields by the CF3SO3H promoted coupling/cyclization reaction of benzylic alcohols and 1,3-dicarbonyls for the first time. For the reactions of methoxy- or methyl-substituted diarylmethanols with 1,3-dicarbonyls, 2 equiv of CF3SO3H was needed to reach the best results; but for the reactions of methoxy-substituted arylethanols with 1,3-dicarbonyls, 0.6 equiv of CF 3SO3H at lower temperatures was capable of promoting the reaction finished.
- Zhang, Wei,Zhang, Wenxue,Dai, Yisi,Zhu, Haizhen
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supporting information
p. 1747 - 1750
(2013/03/28)
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- Ruthenium(II) half-sandwich complexes containing thioamides: Synthesis, structures and catalytic transfer hydrogenation of ketones
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A new family of cationic half-sandwich complexes of the type [(η6-cymene)Ru(PPh3)(L)]+ (L = bidentate monoanionic thioamide) have been synthesized and isolated as their tetraphenylborate salts. All the synthesized ruthenium(II) arene complexes are air stable and are fully characterized by elemental analysis, spectral and X-ray diffraction methods. In chloroform solution all the complexes exhibit characteristic metal to ligand charge transfer (MLCT) absorptions and ligand based transitions. Molecular structure of the complexes 2, 3 and 4 has been determined by single crystal X-ray crystallography indicates that the thioamide ligands are coordinated to ruthenium as a bidentate O, S donor and a typical piano stool geometry was observed around ruthenium(II) metal center. Complexes 1-5 were tested as catalysts in the transfer hydrogenation of aliphatic and aromatic ketones to secondary alcohols in the presence of 2-propanol/KOH. Further, the influence of base, reaction temperature and catalyst loading in this reaction was also evaluated to find out the most active catalyst.
- Pandiarajan, Devaraj,Ramesh, Rengan
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- Half-sandwich ruthenium(ii) picolyl-nhc complexes: Synthesis, characterization, and catalytic activity in transfer hydrogenation reactions
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Pentamethylcyclopentadienyl ruthenium(II) complexes with picolyl-functionalized N-heterocyclic carbenes [(η5-C 5Me5)-Ru(L)(CH3CN)][PF6] (L = 3-methyl-1-(2-picolyl)imidazol-2-ylidene (1a), 3-isopropyl-1-(2-picolyl) imidazol-2-ylidene (1b), 3-phenyl-1-(2-picolyl)imidazol-2-ylidene (1c), 3-mesityl-1-(2-picolyl)imidazol-2-ylidene (1d), 3-methyl-1-(2-picolyl) benzoimidazol-2-ylidene (1e), 3-methyl-1-(2-picolyl)-4,5-dichloroimidazol-2- ylidene (1f)) have been synthesized and characterized. Compounds 1a,b were recrystallized as BAr4 F salts (anion BAr4 F- = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate), giving 2a,b. X-ray crystal structures of the acetonitrile adduct 2a and the dioxygen compound 2b are also reported. Furthermore, carbonyl derivatives 3a-f have been prepared, characterized, and used to study the donor properties of the picolylcarbene ligands(l) via infrared spectroscopy. Compounds 1a-f show catalytic activity in transfer hydrogenation of ketones. Notably, complex 1a was found to be a very efficient and versatile catalyst toward transfer hydrogenation of a wide range of ketones and imines.
- Fernandez, Francys E.,Puerta, M. Carmen,Valerga, Pedro
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experimental part
p. 5793 - 5802
(2012/01/14)
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- An efficient and transition metal free protocol for the transfer hydrogenation of ketones as a continuous flow process
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We report the efficient reduction of a selection of ketones to the corresponding secondary alcohols using only catalytic amounts of LiOtBu in iPrOH facilitated by using a continuous flow reactor.
- Sedelmeier, Joerg,Ley, Steven V.,Baxendale, Ian R.
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experimental part
p. 683 - 685
(2010/04/23)
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- Fast transfer hydrogenation using a highly active orthometalated heterocyclic carbene ruthenium catalyst
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The free carbene 1,3,4-triphenyl-4,5-dihydro-1H-1,2,4-triazol-5-ylidene reacts with trans,cis-RuHCl(PPh3)2(ampy) (ampy = 2-(aminomethyl)pyridine) affording an orthometalated N-heterocyclic carbene complex characterized by an X-ray di
- Baratta, Walter,Schütz, Jan,Herdtweck, Eberhardt,Herrmann, Wolfgang A.,Rigo, Pierluigi
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p. 5570 - 5575
(2007/10/03)
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- Method for preparing a benzylic-type ether
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The invention concerns a method for preparing a benzylic-type ether from an aromatic compound. The inventive method for preparing a benzylic-type ether from an aromatic compound is characterised in that it consists in: in a first step, acylating an aromatic compound by reacting said aromatic compound with an acylating agent, in the presence of an efficient amount of zeolite or a Friedel-Crafts catalyst leading to a ketonic compound; in a second step, reducing the carbonyl group into carbinol leading to a benzylic alcohol; in a third step, etherifying the hydroxyl group, by reacting the benzylic alcohol with another alcohol, in the presence of an efficient amount of zeolite.
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- Process for the preparation of 1-(3,4-dimethoxyphenyl)ethanol
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The subject of our invention is the process for the preparation of the 1-(3,4-dimethoxyphenyl)ethanol of formula (I), by the reduction of 3,4-dimethoxyacetophenone of formula (II), characterized in that the carbonyl group of the 3,4-dimethoxyacetophenone
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Page column 3-4
(2008/06/13)
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- Effect of pH on the mechanism of OClO· oxidation of aromatic compounds
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Contrary to previous reports, the reaction mechanism of chlorine dioxide (OClOC·) with benzyl alcohols involves both radical cation and benzyl radical mechanisms dependent on pH. The primary reaction product between OClOC· and 1-(3,4-dimethoxy-phenyl) ethanol at pH 8 is 3,4-dimethoxyacetophenone. At pH 4 no acetophenone was observed; the majority of the degradation products were chlorinated and aromatic ring-oxidized compounds. A primary kinetic isotope effect (kH/kD = 2.05) was observed in the reaction of OClOC· with 1-(3,4-dimethoxy-phenyl)-(1-2H) ethanol at pH 8, but was absent at pH 4 (kH/kD ≈ 1). Similarly, the corresponding methyl ether (4-(1-methoxy)ethyl-1,2-dimethoxybenzene) was substantially less reactive at pH > 6. On the basis of these results, competing pH-dependent reaction mechanisms have been proposed, where at high pH OClOC· reacts with benzyl alcohols via a OClOC·-benzyl alcohol complex.
- Svenson, Doug,Kadla, John F.,Chang, Hou-Min,Jameel, Hasan
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p. 761 - 766
(2007/10/03)
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- Structure-activity relationship of piperine and its synthetic analogues for their inhibitory potentials of rat hepatic microsomal constitutive and inducible cytochrome P450 activities
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Inhibitors of drug metabolism have important implications in pharmaco- toxicology and agriculture. We have reported earlier that piperine, a major alkaloid of black and long peppers inhibits both constitutive and inducible cytochrome P450 (CYP)-dependent drug metabolising enzymes. In the present study, an attempt has been made to prepare several novel synthetic analogues so as to relate various modifications in the parent molecule to the inhibition of CYP activities. Two types of mono-oxygenase reactions arylhydrocarbon hydroxylase (AHH) and 7-methoxycoumarin-O-demethylase (MOCD) have been studied. Inhibition studies were investigated in rat microsomal fraction prepared from untreated, 3MC- and PB- treated rat liver in vitro. Modifications were introduced into the piperine molecule: (i) in the phenyl nucleus, (ii) in the side chain and (iii) in the basic moiety. Thus, 38 compounds have been subjected to such studies, and simultaneously an attempt has also been made to arrive at the structure-activity relationship of synthetic analogues. In general, most of the inhibitory potential of the parent molecule is lost with modification in either of the three components of piperine. Saturation of the side chain resulted in significantly enhanced inhibition of CYP while modifications in the phenyl and basic moieties in few analogues offered maximal selectivity in inhibiting either constitutive or inducible CYP activities. Thus few novel analogues as CYP inactivators have been synthesized which may have important consequences in pharmacokinetics and bioavailability of drugs. (C) 2000 Elsevier Science Ltd.
- Koul, Surrinder,Koul, Jawahir L.,Taneja, Subhash C.,Dhar, Kanaya L.,Jamwal, Deshvir S.,Singh, Kuldeep,Reen, Rashmeet K.,Singh, Jaswant
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p. 251 - 268
(2007/10/03)
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- A Reinvestigation of the Meerwein-Ponndorf-Verley Reduction: A Highly Efficient Variation Using Zirconium Catalysts
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A new variation of the Meerwein-Ponndorf-Verley reduction based on mechanistic considerations is presented.Under optimized conditions 1-(4-dimethylaminophenyl)ethanol was used as the reducing alcohol (2-4 equiv.), Zr(O-tBu)4 as the catalyst (0.2 equiv.), and toluene or cyclohexane as the solvent.Aldehydes and ketones (if not extremely sterically hindered) were reduced to the corresponding alcohols at room temperature mostly within 2-4 h in essentially quantitative yield. α,β-Unsaturated carbonyl compounds cleanly react in a 1,2-mode to afford the corresponding allylic alcohols. - Key Words: Reductions / Meerwein-Ponndorf-Verley reaction / Catalysis / Zirconium tetra-tert-butoxide / β-Hydride shift / Kinetics
- Knauer, Birgit,Krohn, Karsten
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p. 677 - 684
(2007/10/02)
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- Spectroscopic and Molecular Mechanics Calculations of Discrimination between Enantiomers Possessing an Electron Rich Aromatic Group Directly Attached to the Chiral Carbon Atom with Optically Pure Benzoyl Derivatives
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The discrimination between enantiomers that have a chiral centre directly attached to the electron rich aromatic ring by interactions with optically pure electron deficient aromatic compounds was studied by 1H NMR and molecular mechanics calculations.The enantiomeric spectroscopic discrimination is due to formation of non-bonding interactions which lead to the formation of diastereoisomeric complexes.The calculated HOMO energy values for electron rich racemic compounds and LUMO values for electron poor resolving agents are in good agreement with the observed chemicalshift differences between enantiomers by 1H NMR.Exceptions to these observations are seen for compounds which possess groups that are in a position to sterically push apart the complexation components and thus decrease the binding energy and diminish the enantiomeric discrimination.The discrimination strongly depends on concentration of the components in the solution, their ratio, temperature and the polarity of the media.Polar racemic compounds show the smallest enantiomeric discrimination by increasing the polarity of the media.For good enantiomeric discrimination both chiral centres must be rigidly bound to the aromatic rings.If the chiral centre is separated from the aromatic ring by flexible bonds the enantiomeric recognition fails despite the formation of strong non-bonding interactions.The binding energies calculated by AMBER and MM + force fields are relatively weak (ca. 2 kcal mol-1) suggesting that only a small portion of the molecules in solution are incorporated into the complexes.Our attempt to provide evidence for selective binding of only one enantiomer to the template molecule was unsuccessful.Neverthelessour results support the formation of inter-exchangeable diastereomeric complexes.Although it might be argued that two sets of signals should also be obtained for the template molecule, all our 1H NMR spectra show only one set of signals for the optically pure template and two sets of signals for the racemic component in their chloroform solutions.Despite low binding energies enantiomeric discrimination with strong electron accepting resolving agents can be achieved in as low as 0.01 mol dm-3 chloroform solution.
- Jursic, Branko S.
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p. 961 - 970
(2007/10/02)
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- DEOXYGENATION OF ALDEHYDES AND KETONES WITH SODIUM CYANOBOROHYDRIDE
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Treatment of hydroxy-substituted aromatic aldehydes and ketones with sodium cyanoborohydride yields the corresponding methylene compounds under conditions which favor intermediate carbonium ion formation.
- Elliger, Carl A.
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p. 1315 - 1324
(2007/10/02)
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- Formation and Stability of Ring-Substituted 1-Phenylethyl Carbocations
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The solvolysis of 1-phenylethyl derivatives with electron-donating 4-substituents in 50:50 trifluoroethanol:water(v:v) occurs at a rate that is independent of azide concentration but gives yields of the corresponding azide adducts of up to 98percent by trapping a carbocation intermediate.Rate constants for reactions of the cations with solvent range from 2 x 103 s-1 (4-Me2N) to 4 x 109 s-1 (4-Me), assuming a diffusion-controlled rate constant of 5 x 109 M-1 s-1 for their reactions with azide and thiol anions.Correlation of the rate constants following the Yukawa-Tsuno treatment gives ρn = 2.5, ρr = 5.2, and r+ = 2.1 for the reaction with trifluoroethanol, and ρn = 2.7, ρr = 4.9, and r+ = 1.8 for the reaction with water.The reverse reaction, acid-catalyzed cleavage of substituted 1-phenylethyl alcohols to give the corresponding carbocation, follows ρn = -4.9, ρr = -4.4, and r+ = 0.9.This gives values of ρn = -7.6, ρr = -9.3, and r+ = 1.2 for formation of the cations at equilibrium.There is an imbalance in the development of resonance delocalization, analogous to the "nitroalkane anomaly", that is consistent with a dependence of the fraction of maximal resonance delocalization on the fraction of rehybridization or C-X bond cleavage.Solvent effects on carbocation stability in aqueous-organic mixtures are relatively small.They depend mainly on the nucleophilicity of the solvent components and a specific solvent effect of trifluoroethanol on the reactivity of hydroxylic nucleophiles, including trifluoroethanol itself.The "ionizing power" of the solvent has only a small effect on cation stability, and there is little effect of the concentration or nature of added salts.
- Richard, John P.,Rothenberg, Marc E.,Jencks, William P.
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p. 1361 - 1372
(2007/10/02)
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- Studies on the chemical constituents of rutaceous plants. XLIX. Development of a versatile method for the synthesis of antitumor-active benzo[c]phenanthridine alkaloids. (1). Preparation of various 2,4-bisaryl-4-oxobutyronitriles and 2,4-bisaryl-4-oxobutyramides
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For the sake of establishment of a versatile synthetic method for benzo[c]phenanthridine alkaloids, improvement of the Robinson synthetic method was examined. Thirteen chalcones (7a-m) were prepared by condensation of two acetophenone derivatives (15 and 16) with eleven benzaldehyde derivatives (19a-k) as fundamental starting materials. Hydrocyanation of these chalcones (7a-1) except one (7m) gave the corresponding 2,4-bisaryl-4-oxobutyronitriles (8a-1). Eleven 2,4-bisaryl-4-oxobutyramides (9a-k) were also prepared.
- Ishii,Ishikawa,Deushi,et al.
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p. 3024 - 3038
(2007/10/02)
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