- Radical dehydroxylative alkylation of tertiary alcohols by Ti catalysis
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Deoxygenative radical C?C bond-forming reactions of alcohols are a long-standing challenge in synthetic chemistry, and the current methods rely on multistep procedures. Herein, we report a direct dehydroxylative radical alkylation reaction of tertiary alcohols. This new protocol shows the feasibility of generating tertiary carbon radicals from alcohols and offers an approach for the facile and precise construction of all-carbon quaternary centers. The reaction proceeds with a broad substrate scope of alcohols and activated alkenes. It can tolerate a wide range of electrophilic coupling partners, including allylic carboxylates, aryl and vinyl electrophiles, and primary alkyl chlorides/bromides, making the method complementary to the cross-coupling procedures. The method is highly selective for the alkylation of tertiary alcohols, leaving secondary/primary alcohols (benzyl alcohols included) and phenols intact. The synthetic utility of the method is highlighted by its 10-g-scale reaction and the late-stage modification of complex molecules. A combination of experiments and density functional theory calculations establishes a plausible mechanism implicating a tertiary carbon radical generated via Ti-catalyzed homolysis of the C?OH bond.
- Xie, Hao,Guo, Jiandong,Wang, Yu-Quan,Wang, Ke,Guo, Peng,Su, Pei-Feng,Wang, Xiaotai,Shu, Xing-Zhong
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supporting information
p. 16787 - 16794
(2020/11/09)
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- Medium-chain fatty acids from Eugenia winzerlingii leaves causing insect settling deterrent, nematicidal, and phytotoxic effects
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Eugenia winzerlingii (Myrtaceae) is an endemic plant from the Yucatan peninsula. Its organic extracts and fractions from leaves have been tested on two phloem-feeding insects, Bemisia tabaci and Myzus persicae, on two plant parasitic nematodes, Meloidogyne incognita and Meloidogyne javanica, and phytotoxicity on Lolium perenne and Solanum lycopersicum. Results showed that both the hexane extract and the ethyl acetate extract, as well as the fractions, have strong antifeedant and nematicidal effects. Gas chromatography-mass spectrometry analyses of methylated active fractions revealed the presence of a mixture of fatty acids. Authentic standards of detected fatty acids and methyl and ethyl derivatives were tested on target organisms. The most active compounds were decanoic, undecanoic, and dodecanoic acids. Methyl and ethyl ester derivatives had lower effects in comparison with free fatty acids. Dose-response experiments showed that undecanoic acid was the most potent compound with EC50 values of 21 and 6 nmol/cm2 for M. persicae and B. tabaci, respectively, and 192 and 64 nmol for M. incognita and M. javanica, respectively. In a phytotoxicity assay, medium-chain fatty acids caused a decrease of 38-52% in root length and 50-60% in leaf length of L. perenne, but no effects were observed on S. lycopersicum. This study highlights the importance of the genus Eugenia as a source of bioactive metabolites for plant pest management.
- Cruz-Estrada, Angel,Ruiz-Sánchez, Esaú,Cristóbal-Alejo, Jairo,González-Coloma, Azucena,Andrés, María Fe,Gamboa-Angulo, Marcela
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- Transfer Hydrogenation of Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex: Scope and Mechanism
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The first general catalytic approach to effecting transfer hydrogenation (TH) of unactivated alkenes using ethanol as the hydrogen source is described. A new NCP-type pincer iridium complex (BQ-NCOP)IrHCl containing a rigid benzoquinoline backbone has been developed for efficient, mild TH of unactivated C-C multiple bonds with ethanol, forming ethyl acetate as the sole byproduct. A wide variety of alkenes, including multisubstituted alkyl alkenes, aryl alkenes, and heteroatom-substituted alkenes, as well as O- or N-containing heteroarenes and internal alkynes, are suitable substrates. Importantly, the (BQ-NCOP)Ir/EtOH system exhibits high chemoselectivity for alkene hydrogenation in the presence of reactive functional groups, such as ketones and carboxylic acids. Furthermore, the reaction with C2D5OD provides a convenient route to deuterium-labeled compounds. Detailed kinetic and mechanistic studies have revealed that monosubstituted alkenes (e.g., 1-octene, styrene) and multisubstituted alkenes (e.g., cyclooctene (COE)) exhibit fundamental mechanistic difference. The OH group of ethanol displays a normal kinetic isotope effect (KIE) in the reaction of styrene, but a substantial inverse KIE in the case of COE. The catalysis of styrene or 1-octene with relatively strong binding affinity to the Ir(I) center has (BQ-NCOP)IrI(alkene) adduct as an off-cycle catalyst resting state, and the rate law shows a positive order in EtOH, inverse first-order in styrene, and first-order in the catalyst. In contrast, the catalysis of COE has an off-cycle catalyst resting state of (BQ-NCOP)IrIII(H)[O(Et)···HO(Et)···HOEt] that features a six-membered iridacycle consisting of two hydrogen-bonds between one EtO ligand and two EtOH molecules, one of which is coordinated to the Ir(III) center. The rate law shows a negative order in EtOH, zeroth-order in COE, and first-order in the catalyst. The observed inverse KIE corresponds to an inverse equilibrium isotope effect for the pre-equilibrium formation of (BQ-NCOP)IrIII(H)(OEt) from the catalyst resting state via ethanol dissociation. Regardless of the substrate, ethanol dehydrogenation is the slow segment of the catalytic cycle, while alkene hydrogenation occurs readily following the rate-determining step, that is, β-hydride elimination of (BQ-NCOP)Ir(H)(OEt) to form (BQ-NCOP)Ir(H)2 and acetaldehyde. The latter is effectively converted to innocent ethyl acetate under the catalytic conditions, thus avoiding the catalyst poisoning via iridium-mediated decarbonylation of acetaldehyde.
- Wang, Yulei,Huang, Zhidao,Leng, Xuebing,Zhu, Huping,Liu, Guixia,Huang, Zheng
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supporting information
p. 4417 - 4429
(2018/04/05)
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- Synthesis of insoluble polystyrene-supported flavins and their catalysis in aerobic reduction of olefins
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2′,4′-p-Vinylbenzylideneriboflavin (2′,4′-PVBRFl) was prepared as a flavin-containing monomer and copolymerized with divinylbenzene and styrene or its p-substituted derivatives such as 4-acetoxystyrene, 4-vinylbenzyl alcohol, and 4-vinylbenzoic acid to give the corresponding non-functionalized and functionalized PS-DVB-supported flavins PS(H)-DVB-Fl, PS(OAc)-DVB-Fl, PS(CH2OH)-DVB-Fl, and PS(COOH)-DVB-Fl, respectively. PS(OH)-DVB-Fl was also prepared by hydrolysis of PS(OAc)-DVB-Fl under basic conditions. These novel flavin-containing insoluble polymers exhibited characteristic fluorescence in solid state, except PS(OH)-DVB-Fl, and different catalytic activities in aerobic reduction of olefins by in situ generated diimide from hydrazine depending on their pendant functional group. For example, PS(H)-DVB-Fl was found to be particularly effective for neutral hydrophobic substrates, which could be readily recovered by a simple filtration and reused more than 10 times without loss in catalytic activity. On the other hand, PS(OH)-DVB-Fl and PS(COOH)-DVB-Fl proved to be highly active for phenolic substrates known to be less reactive in the reaction with conventional non-supported flavin catalysts.
- Arakawa, Yukihiro,Kawachi, Risa,Tezuka, Yoshihiko,Minagawa, Keiji,Imada, Yasushi
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p. 1706 - 1713
(2017/04/11)
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- Hydroalkylation of Alkenes Using Alkyl Iodides and Hantzsch Ester under Palladium/Light System
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The hydroalkylation of alkenes using alkyl iodides with Hantzsch ester as a hydrogen source occurred smoothly under a Pd/light system, in a novel, tin-free Giese reaction. A chemoselective reaction at C(sp3)-I in the presence of a C(sp2)-X (X = Br or I) bond was attained, which allowed for the stepwise functionalization of two types of C-X bonds in a one-pot procedure.
- Sumino, Shuhei,Ryu, Ilhyong
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supporting information
p. 52 - 55
(2016/01/12)
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- PROCESS FOR THE CHEMOSELECTIVE REDUCTION OF TERMINALLY SATURATED CARBOXYLIC ESTERS
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The chemoselective reduction of a carboxylic ester (I) to an alcohol by catalytic hydrogenation, in particular in the presence of a transition metal complex, more particularly in the presence of a ruthenium (II) complex is described.
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Paragraph 0056-0062
(2015/06/10)
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- Pd-Catalyzed Regioselective Alkoxycarbonylation of 1-Alkenes Using a Lewis Acid [SnCl2 or Ti(OiPr)4] and a Phosphine
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The phosphine ligand mediated palladium catalyzed alkoxycarbonylation of alkenes was investigated with the objective of attaining good linear selectivity for the ester. The effect of various parameters such as solvents, additives, palladium precursors, CO pressures, and alkenes of various structural complexities were examined. The results revealed the importance of using a Lewis acid such as SnCl2 or Ti(OiPr)4 in combination with a monodentate ligand such CYTOP 292 or P(p-anisyl)3 to enhance the regioselectivity for the linear isomers in the range of 70-96%.
- Amézquita-Valencia, Manuel,Achonduh, George,Alper, Howard
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p. 6419 - 6424
(2015/06/30)
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- Borohydride-mediated radical addition reactions of organic iodides to electron-deficient alkenes
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Cyanoborohydrides are efficient reagents in the reductive addition reactions of alkyl iodides and electron-deficient olefins. In contrast to using tin reagents, the reaction took place chemoselectively at the carbon-iodine bond but not at the carbon-bromine or carbon-chlorine bond. The reaction system was successfully applied to three-component reactions, including radical carbonylation. The rate constant for the hydrogen abstraction of a primary alkyl radical from tetrabutylammonium cyanoborohydride was estimated to be 4 M-1 s-1 at 25 °C by a kinetic competition method. This value is 3 orders of magnitude smaller than that of tributyltin hydride.
- Kawamoto, Takuji,Uehara, Shohei,Hirao, Hidefumi,Fukuyama, Takahide,Matsubara, Hiroshi,Ryu, Ilhyong
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p. 3999 - 4007
(2014/05/20)
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- PROCESS FOR THE CHEMOSELECTIVE REDUCTION OF TERMINALLY SATURATED CARBOXYLIC ESTERS
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The chemoselective reduction of a carboxylic ester (I) to an alcohol by catalytic hydrogenation, in particular in the presence of a transition metal complex, more particularly in the presence of a ruthenium (II) complex is described.
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Page/Page column 11
(2013/12/03)
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- METHOD OF PRODUCING SATURATED ALKYL ESTERS/ACIDS
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Disclosed herein is the production of saturated alkyl esters or acids from furan materials. The starting compounds contain furan, ketone, and ester or acid functional groups and may be biologically-derived. The method includes hydrogenating the starting compound to form a reduced mixture. The method further includes hydrodeoxygenation of the reduced mixture to yield a saturated alkyl ester or acid. The saturated alkyl ester or acid can be unbranched or branched. The ester and acid products have a wide variety of applications and may be further processed into surfactants, solvents, and lubricants suitable for use in consumer products.
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- Flow Giese reaction using cyanoborohydride as a radical mediator
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Tin-free Giese reactions, employing primary, secondary, and tertiary alkyl iodides as radical precursors, ethyl acrylate as a radical trap, and sodium cyanoborohydride as a radical mediator, were examined in a continuous flow system. With the use of an automated flow microreactor, flow reaction conditions for the Giese reaction were quickly optimized, and it was found that a reaction temperature of 70 °C in combination with a residence time of 10-15 minutes gave good yields of the desired addition products.
- Fukuyama, Takahide,Kawamoto, Takuji,Kobayashi, Mikako,Ryu, Ilhyong
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supporting information
p. 1791 - 1796
(2013/10/22)
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- Development of microchannel reactors using polysilane-supported palladium catalytic systems in capillaries
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A new method of immobilizing Pd catalysts on the channel wall of a capillary by using polysilane with metal oxide has been developed, and applied to hydrogenation reactions. The Royal Society of Chemistry.
- Ueno, Masaharu,Suzuki, Toshie,Naito, Takeshi,Oyamada, Hidekazu,Kobayashi, Shu
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p. 1647 - 1649
(2008/12/22)
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- Tin-free giese reaction and the related radical carbonylation using Alkyl iodides and cyanoborohydrides
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Tin-free Giese reaction and the related radical carbonylation process proceeded efficiently in the presence of sodium cyanoborohydride and tetrabutylammonium cyanoborohydride. The reaction took place chemoselectively at the carbon-iodine bond but not at the carbon-bromine and carbon-chlorine bonds. The iodine atom transfer followed by hydride reduction of the resulting carbon-iodine bond is proposed as a possible mechanism.
- Ryu, Ilhyong,Uehara, Shohei,Hirao, Hidefumi,Fukuyama, Takahide
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supporting information; experimental part
p. 1005 - 1008
(2009/04/07)
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- Hydrogenation reactions using scCO2 as a solvent in microchannel reactors
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We have developed an effective microfluidic system for hydrogenation reactions in ScCO2; the reactions proceeded very rapidly (within 1 second), by making the best use of ScCO2 and utilizing the large specific interfacial area of the microchannel reactor, and high reaction productivity was attained in each channel. The Royal Society of Chemistry 2005.
- Kobayashi, Juta,Mori, Yuichiro,Kobayashi, Shu
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p. 2567 - 2568
(2007/10/03)
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- A New Coupling Reaction of Alkyl Iodides with Electron Deficient Alkenes Nickel Boride (cat.) - Borohydride Exchange Resin in Methanol
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The radical addition reaction of alkyl iodides with α,β-unsaturated esters, nitriles, and ketones proceeds in moderate to excellent yields (50-95%) using Ni(OAc)2 (0.05-0.2 equiv) - BER (3-5 equiv) in methanol in 1-9 h at room temperature or at 65°C. Nickel boride on borohydride exchange resin (BER) is a good alternative reagent to tributyltin hydride for the coupling of alkyl iodides with the electron deficient alkenes in methanol. Compared with tributyltin hydride method, this method has an advantage of simple workup, since nickel boride - BER can be removed readily by filtration.
- Sim, Tae Bo,Choi, Jaesung,Joung, Meyoung Ju,Yoon, Nung Min
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p. 2357 - 2361
(2007/10/03)
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- A new coupling reaction of alkyl iodides with α,β-unsaturated esters using Ni2B(cat.)-BER in methanol
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Alkyl iodides can be coupled with α,β-unsaturated esters using Ni2B(0.05-0.2 eq)-BER(3 eq) in methanol at room temperature. Products (68-95%) are conveniently isolated, simply filtering the resin and evaporating the excess enoates and methanol.
- Sim, Tae Bo,Choi, Jaesung,Yoon, Nung Min
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p. 3137 - 3140
(2007/10/03)
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- A New Preparation of Diorganozincs from Olefins via a Nickel Catalyzed Hydrozincation
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The reaction of olefins with diethylzinc in the presence of catalytic amounts of Ni(acac)2 provides dialkylzincs (neat, 40-50 degC, 2-6 h).These zinc reagents can be trapped by various electrophiles or used for the catalytic asymmetric addition to aldehydes (>85 percent ee).Allylic and homoallylic alcohols are especially good substrates for the reaction.
- Vettel, Stephan,Vaupel, Andrea,Knochel, Paul
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p. 1023 - 1026
(2007/10/02)
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- Desulfurization with Nickel and Cobalt Boride: Scope, Selectivity, Stereochemistry, and Deuterium-Labeling Studies
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A variety of organosulfur compounds containing alkylthio and arylthio groups underwent reductive desulfurization under notably mild conditions when treated with nickel boride, generated in situ from nickel chloride hexahydrate and sodium borohydride in methanol-THF (3:1).Phenyl, chloro, and ester groups are not reduced under these conditions, while iodo, bromo, nitrile, aldehyde, ketone, cyclopropane, and olefinic functions are reduced either completely or partially.Deuterium-labeling studies indicate that the hydrogen that is incorporated into the product originates from both the sodium borohydride and the protic solvent, suggesting the intermediacy of dihydrogen.The epimers 3α- and 3β-(phenylthio)cholestane afforded 3α- and 3β-deuteriocholestane, respectively, demonstrating that the reaction proceeds with retention of configuration.The method may thus be employed for the stereospecific preparation of deuterated products from organosulfur compounds.Arguments are presented in support of a tentative mechanism involving an oxidative addition-reductive elimination sequence via a nickel hydride intermediate.
- Back, Thomas G.,Baron, Denise L.,Yang, Kexin
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p. 2407 - 2413
(2007/10/02)
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- TRANSITION METAL COMPLEX CATALYZED CARBONYLATION OF ORGANIC HALIDES IN THE PRESENCE OF MOLECULAR SIEVES INSTEAD OF BASE
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In the presence of molecular sieves under base free conditions organic halides are successfully carbonylated under carbon monoxide pressure with water or alcohols catalyzed by Co or Pd complex to generate the corresponding carboxylic acids or esters, respectively, in good yields.
- Urata, Hisao,Hu, Nan-Xing,Maekawa, Hisayuki,Fuchikami, Takamasa
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p. 4733 - 4736
(2007/10/02)
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- REACTIONS OF ORGANIC HALIDES WITH OLEFINS UNDER Ni0-CATALYSIS. FORMAL ADDITION OF HYDROCARBONS TO CC-DOUBLE BONDS
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The reaction of various types of organic halides with electron deficient olefins under the influence of NiCl2 x 6 H2O in the presence of zinc and pyridine leads to formal addition products of hydrocarbons to CC-double bonds in good yield.
- Sustmann, Reiner,Hopp, Peter,Holl, Peter
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p. 689 - 692
(2007/10/02)
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