- PARTIAL HYDROGENATION OF ACETYLENES ON MODIFIED NICKEL BORIDE CATALYSTS.
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It is shown that Ni-B catalysts modified with a small amount of copper(II) salt have a hgher selectivity than palladium and modified Raney nickel catalysts for partial hydrogenation of phenylacetylene, 1-heptyne, 1-ethynylcyclohexene, and propargyl alcoho
- Nitta,Imanaka,Teranishi
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- Promoting Role of Iron Series Elements Modification on Palladium/Nitrogen Doped Carbon for the Semihydrogenation of Phenylacetylene
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In this work, an effective and versatile modification approach of palladium (Pd)/nitrogen doped carbon by iron series element for the semihydrogenation of phenylacetylene is presented. Pd and iron series element M (M=Fe, Co or Ni) particles were co-reduce
- Zhang, Wei,Wu, Wei,Long, Yu,Qin, Jiaheng,Wang, Fushan,Ma, Jiantai
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- Defect-site promoted surface reorganization in nanocrystalline ceria for the low-temperature activation of ethylbenzene
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Defect-site enriched nanocrystalline ceria prepared by an alcoholysis method favors oxidative dehydrogenation of ethylbenzene using nitrous oxide with high conversion and selectivity at much lower temperatures compared to ceria samples prepared by other c
- Murugan,Ramaswamy
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- Oxorhenium-catalyzed deoxydehydration of glycols and epoxides
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The conversion of renewable cellulosic biomass into hydrocarbons has attracted significant attention with a growing demand of sustainability. MeReO3 catalyzes the deoxydehydration (DODH) of glycols and epoxides to alkenes by primary and secondary alcohols (5-nonanol, 3-octanol, 1-butanol) in the benzene solvent. The product yield range from moderate to excellent.
- Davis, Jacqkis,Srivastava, Radhey S.
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- The reactivity of ketyl and alkyl radicals in reactions with carbonyl compounds
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A parabolic model of bimolecular radical reactions was used for analysis of the hydrogen transfer reactions of ketyl radicals: >C+OH + R1COR2 → >C=O + R1R2C+OH. The parameters describing the reactivity of the reagents were calculated from the experimental data. The parameters that characterize the reactions of ketyl and alkyl radicals as hydrogen donors with olefins and with carbonyl compounds were obtained: >C+OH + R1CH=CH2 → >C=O + R1C+ HCH3; >R1CH=CH2 + R2C+HCH2R3 → R2C+HCH3 + R2CH=CHR3. These parameters were used to calculate the activation energies of these transformations. The kinetic parameters of reactions of hydrogen abstraction by free radicals and molecules (aldehydes, ketones, and quinones) from the C-H and O-H bonds were compared.
- Denisov
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- Mercury in Organic Chemistry. 25. Rhodium(I)-Catalyzed Alkenylation of Arylmercurials
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Arylmercurials and vinyl halides are catalytically cross-coupled to aryl olefins in fair to good yields by 10percent ClRh(PPh3)3.This reaction appears to proceed through an arylvinylrhodium(III) intermediate.
- Larock, R. C.,Narayanan, K.,Hershberger, S. S.
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- Practical iron-catalyzed dehalogenation of aryl halides
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An operationally simple iron-catalyzed hydrodehalogenation of aryl halides has been developed with 1 mol% Fe(acac)3 and commercial t-BuMgCl as reductant. The mild reaction conditions (THF, 0 °C, 1.5 h) effect rapid chemoselective dehalogenation of (hetero)aryl halides (I, Br, Cl) and tolerate F, Cl, OR, SR, CN, CO2R, and vinyl groups.
- Czaplik, Waldemar Maximilian,Grupe, Sabine,Mayer, Matthias,Wangelin, Axel Jacobi Von
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- An ionic compound containing Ru(III)-complex cation and phosphotungstate anion as the efficient and recyclable catalyst for clean aerobic oxidation of alcohols
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A novel ionic compound (3, [RuCl4(L)2] 3PW12O40) containing the Ru(III)-complex cation and α-Keggin-type phosphotungstate anion was synthesized and proven to be the efficient catalyst for aerobic oxidations of alcohols free of base and nitroxyl radical. Specially, 3 could be reused at least five runs without obvious activity loss. The stability of 3 was dramatically improved due to the incorporation of [PW12O40]3 - as the counter-anions, leading to its available recyclability.
- Wang, Sa-Sa,Zhang, Jing,Zhou, Cheng-Liang,Vo-Thanh, Giang,Liu, Ye
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- Facile Styrene Formation from Ethylene and a Phenylplatinum(II) Complex Leading to an Observable Platinum(II) Hydride
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A new 2-(di-tert-butylphosphanyl)benzenesulfonate-supported phenylplatinum(II) complex instantaneously but reversibly binds ethylene at room temperature. Direct and rapid styrene formation at room temperature via insertion of the PtII-bound ethylene into the PtII-Ph fragment followed by β-hydride elimination results in the formation of a solution-stable PtII-H complex. The PtII-H fragment is resistant toward protonolysis by acetic acid. Oxidation of the PtII-H fragment by excess CuII(OTf)2 leads to an inorganic PtII complex incapable of C-H activation.
- Pal, Shrinwantu,Kusumoto, Shuhei,Nozaki, Kyoko
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- Thermal Ring-Splitting Reactions of Diarylcyclobutanes: Significance of Steric Effects on Orbital Interactions in Transition States and Biradical Intermediates
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Regiochemistry and rectivities in the thermal ring-splitting reactions of diarylcyclobutanes (1-5) have been studied and shown to depend on the stable conformations and rotational mobilities of the aryl substituents.The reactions of 1 and 2 result in a regiospecific symmetric cleavage to give indene or styrene along with significant isomerization of 2 to 3.In the cases of 3-5 both the symmetric and unsymmetric cleavages competitively occur with decreasing symmetric-to-unsymmetric ratios with an increase in methyl substitution.The olefin products from 4 are mixtures of cis- and trans-2-butene, cis- and trans-β-methylstyrene, and trans-stilbene.Thermochemical analyses combined with product analyses indicate that the symetric cleavage of 1 and the unsymmetric cleavage of 3 proceed with a concerted mechanism, whereas 1,4-biradicals are involved in the other reactions.Structure-reactivity relationships of the present reactions are discussed in terms of mixing of the ?* character in a bonding MO by specific ?-?* interactions, depending on the conformational situations of the aryl groups and in terms of the steric effects which destabilize 1,4-biradicals as well as transition states of the biradical fragmentation to the olefins.
- Yasuda, Masahide,Yoshida, Kouhei,Shima, Kensuke,Pac, Chyongjin,Yanagida, Shozo
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- Nickel-catalyzed Kumada reaction of tosylalkanes with Grignard reagents to produce alkenes and modified arylketones
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Open a new door: The first example of alkene synthesis from alkyl electrophiles with Grignard reagents using the Kumada cross-coupling reaction strategy is reported. This method opens a new door for the Kumada cross-coupling reaction, allowing alkenes to be prepared from the reaction of tosylalkanes with Grignard reagents. Copyright
- Wu, Ji-Cheng,Gong, Lu-Bing,Xia, Yuanzhi,Song, Ren-Jie,Xie, Ye-Xiang,Li, Jin-Heng
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- New Ruthenium-Molybdenum and -Tungsten Heterodinuclear Complexes with trans-Styryl Ligand
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New styryl ruthenium-molybdenum and -tungsten complexes Cp(CO)3M-Ru (trans-styryl)(CO)(PPh3)2 have been prepared by the metathetical reactions of Ru(trans-styryl)Cl(CO)(PPh3)2 with Na.The reactions of 2 with CO and with PMe3
- Fukuoka, Atsushi,Ohashi, Nobutoshi,Komiya, Sanshiro
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- A Gas-phase Anionic Analog of the Wittig Reaction. An Ion Cyclotron Resonance Study of the Gas-phase Ion Chemistry of Silyl Carbanions
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Gas-phase ion-molecule reactions of a variety of fluorosilyl carbanions with compounds containing double bonds to oxygen, X=O, have been examined using pulsed ion cyclotron resonance spectroscopy.The predominant reaction channel observed for species not containing acidic hydrogen is a Wittig-like process involving Si-O bond formation and elimination of X=CH2 species.The gas-phase acidity of F3Si(CH3) has been determined and those of F2Si(CH3)2 and FSi(CH3)3 have been estimated.From the fluoride transfer reactions of F3SiCH2- the fluoride affinity of F2Si=CH2 has been estimated and limits on the ? bond strength in this silaethene obtained.Potential analytical applications of the Wittig reactivity have been discussed.
- Campanaro, A.,Marvin, C. H.,Morehouse, S. P.,McMahon, T. B.
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- Palladium-catalyzed convenient one-pot synthesis of multi-substituted 2-pyrones via transesterification and alkenylation of enynoates
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An efficient one-pot protocol for the synthesis of multi-substituted 2-pyrone derivatives from internal alkynes and unactivated alkenes is reported. The methodology involves difunctionalization of internal alkynes by using Pd(II) as a catalyst alongwith X-Phos as ligand via 6-endo transesterification and subsequent alkenylation pathway. Notable features include simple and easily available starting materials, including a range of unactivated alkenes, reduced synthetic steps and mild reaction conditions with high efficiency.
- Pathare, Ramdas S.,Sharma, Shivani,Gopal, Kandasamy,Sawant, Devesh M.,Pardasani, Ram T.
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- Amine hemilability enables boron to mechanistically resemble either hydride or proton
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Tetracoordinate MIDA (N-methyliminodiacetic acid) boronates have found broad utility in chemical synthesis. Here, we describe mechanistic insights into the migratory aptitude of the MIDA boryl group in boron transfer processes, and show that the hemilabil
- Lee, C. Frank,Diaz, Diego B.,Holownia, Aleksandra,Kaldas, Sherif J.,Liew, Sean K.,Garrett, Graham E.,Dudding, Travis,Yudin, Andrei K.
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- Atomic layer deposition of aluminium on anatase: A solid acid catalyst with remarkable performances for alcohol dehydration
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Here we reported the synthesis of Al sites with ultra-high dispersion on anatase by an atomic layer deposition (ALD) method (ALD-Al/TiO2), which exhibits Br?nsted acidity and satisfactory activity in the dehydration of alcohols, a key step in the deoxygenation of biomass. More importantly, the ALD-Al/TiO2 catalyst has good stability, which is sintering-resistant and gives constant catalytic performances after treatments at high temperature.
- Song, Yingji,Xu, Shaodan,Ling, Fei,Tian, Panpan,Ye, Tao,Yu, Deqing,Chu, Xuefeng,Lin, Yingzi,Yang, Xiaotian,Tang, Junhong
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- Stereospecific rhenium catalyzed desulfurization of thiiranes
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Methyltrioxorhenium catalyzes the efficient and stereospecific desulfurization of thiiranes by triphenylphosphine at room temperature, moreso when MTO has been pretreated with hydrogen sulfide, with a Re(v) species as the active form of the catalyst.
- Jacob, Josemon,Espenson, James H.
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- Readily recyclable catalysts of zeolite nanoparticles linked with polymer chains
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Aggregates of zeolite nanoparticles were linked together with polypropylene oxide or polydimethylsiloxane polymer chains, and were used as catalysts for liquid-phase reactions. The polymer-linked catalysts showed high catalytic activity in esterification of acetic acid with 1-propanol and hydrolysis of ethyl acetate, and were readily separated from reaction mixtures by decantation. Moreover, the linkage with the polymer chains enhanced shape selectivity in esterification of acetic acid with cyclohexanol and dehydration of 1-phenylethanol because of passivating the external acid sites of the zeolite with the polymer.
- Okamoto, Masaki,Watanabe, Satoshi,Nitta, Junya
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- The Dehalogenation of vic-Dihaloalkanes to Alkenes with Sodium Trithiocarbonate or Sodium Dithiocarbonate in the Presence of Phase-Transfer Catalysts
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The reductive dehalogenation of vic-dihaloalkanes with aqueous sodium trithiocarbonate or sodium dithiocarbonate in the presence of a phase-transfer catalyst gave the corresponding alkenes in high yields under mild conditions.
- Sugawara, Akira,Nakamura, Atsushi,Araki, Akitoshi,Sato, Ryu
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- Liquid-phase dehydration of 1-phenylethanol to styrene over sulfonated D-glucose catalyst
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Dehydration of 1-phenylethanol to produce styrene has been studied in liquid phase without any solvent with carbon-based solid acid catalysts prepared in one step from renewable resources like d-glucose for the first time. The carbon-based catalyst shows
- Hasan, Zubair,Hwang, Jin-Soo,Jhung, Sung Hwa
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- Phosphine and N-heterocyclic carbene ligands on Pt(II) shift selectivity from ethylene hydrophenylation toward benzene vinylation
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Abstract A series of Pt(II) complexes of the type ([(L～L)Pt(L′)(Ph)][BAr′4] (L～L = 1,2-bis(dimethylphosphino)ethane, 1,2-bis(diphenylphosphino)ethane, (N-pyrrolyl)2P(CH2)2P(N-pyrrolyl)2, 1,3-bis(diphe
- Brosnahan, Anna M.,Talbot, Austin,McKeown, Bradley A.,Kalman, Steven E.,Gunnoe, T. Brent,Ess, Daniel H.,Sabat, Michal
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- A stable well-defined copper hydride cluster consolidated with hemilabile phosphines
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Copper hydrides are very useful in hydrogenation reactions. We report a stable Stryker-type copper hydride reagent protected by hemilabile phosphines: [Cu8H6(dppy)6](OTf)2(Cu8-H, dppy = diphenylphosphino-2-pyridine). The metal core of this cluster has a bicapped octahedral configuration, and the copper-bound hydrides each triply bridges over a triangular face of the octahedron. This cluster is attractive due to its facile preparation and excellent stability under ambient conditions. The comparable activity and selectivity both in the stoichiometric and catalytic reactions makeCu8-Ha promising alternative to Stryker's reagent.
- Yuan, Shang-Fu,Luyang, Heng-Wang,Lei, Zhen,Wan, Xian-Kai,Li, Jiao-Jiao,Wang, Quan-Ming
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- Pyrolysis of Ethylbenzene
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The pyrolysis of ethylbenzene has been studied using a static reactor.At low conversion hydrogen and styrene are the major products together with methane, toluene, ethylene, ethane and benzene plus traces of higher molecular-weight hydrocarbons.The pyroly
- Brooks, C. Terence,Peacock, Stanley J.,Reuben, Bryan G.
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- Domino Methylenation/Hydrogenation of Aldehydes and Ketones by Combining Matsubara's Reagent and Wilkinson's Catalyst
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The methylenation/hydrogenation cascade reaction of aldehydes or ketones through a domino process involving two ensuing steps in a single pot is realized. The compatibility of Matsubara's reagent and Wilkinson's complex give a combination that allows, under dihydrogen, the transformation of a carbonyl function into a methyl group. This new method is suitable to introduce an ethyl motif from aromatic and aliphatic aldehydes with total chemoselectivity and total retention of α-stereochemical purity. The developed procedure is also extended to the introduction of methyl groups from ketones.
- Maazaoui, Radhouan,Pin-Nó, María,Gervais, Kevin,Abderrahim, Raoudha,Ferreira, Franck,Perez-Luna, Alejandro,Chemla, Fabrice,Jackowski, Olivier
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- Catalytic reactions of samarium(II) iodide
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A system for in situ regeneration of SmI2 from SmI3 is described which allows the annulation of ketones to γ-lactones, the deoxygenation of oxiranes to olefins and radical π-cyclization to be conducted with 10 mole % SmI2.
- Corey,Zheng, Guo Zhu
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- Measurement of Deuterium Kinetic Isotope Effects in Organic and Biochemical Reactions by Natural Abundance Deuterium NMR Spectroscopy
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Natural abundance deuterium NMR spectroscopy is a powerful and convenient tool for the estimation of deuterium kinetic isotope effects in organic reactions, obviating in many cases the preparation of isotopically enriched reactants for such measurements.Determinations of the primary or secondary kinetic isotope effects for a broad variety of reaction types are described to illustrate this technique.
- Pascal, Robert A. Jr.,Baum, Mary W.,Wagner, Carol K.,Rodgers, Lauren R.,Huang, Ded-Shih
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- β-Cyclodextrin as a Molecular Reaction Vessel: Reactions of Included Phenylmethyldiazirine
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Phenylmethyldiazirine forms a stable, solid complex with β-cyclodextrin.The diazirine was decomposed by pyrolysis or irradiation of the complex, and the reaction products were analyzed.The major volatile products consist of the isomeric 1,2-diphenyl-1-methylcyclopropanes.Under photolytic conditions a significant amount of styrene also is formed.The selectivity for trans isomer formation is 10 times greater from the CD complex than from the neat state.Carbene insertion products with β-cyclodextrin are formed under both reaction conditions.The product distributions are explained by cage and shape-selective effects exerted by β-cyclodextrin.
- Abelt, Christopher J.,Pleier, Jennifer M.
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- Alkene Formation through Condensation of Phenylmethanesulphonyl Fluoride with Carbonyl Compounds
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Arylmethanesulphonyl fluorides condense with aromatic, aliphatic and conjugated aldehydes and ketones in the presence of potassium carbonate and a crown ether to give aryl-substituted alkenes in satisfactory to modest yields.
- Kagabu, Shinzo,Hara, Kenji,Takahashi, Junko
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- Reduction of Organic Halides with Diethyl Phosphonate and Triethylamine
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Reduction of organic halides with diethyl phosphonate and triethylamine is surveyed.
- Hirao, Toshikazu,Kohno, Shuichiro,Ohshiro, Yoshiki,Agawa, Toshio
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- Catalytic activity of iron-substituted polyoxotungstates in the oxidation of aromatic compounds with hydrogen peroxide
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The tetrabutylammonium (TBA) salts of Keggin-type polyoxotungstates of the general formula [XW11FeIII(H2O)O39] n-, where X = P, B or Si, were evaluated as catalysts in the oxidation, under mild conditions, of ethylbenzene, cumene, p-cymene and sec-butylbenzene with aqueous H2O2 in CH3CN at 80 °C. The influence of various factors, such as the substrate/catalyst molar ratio, the amount of oxidant added or the reaction time, was investigated in a systematic way. Generally, the system exhibited moderate conversion, with good selectivity towards the corresponding acetophenone and hydroperoxide. In order to understand the reaction pathways, the oxidation of several products and presumed intermediates was also carried out in the presence of TBA 4[PW11Fe(H2O)O39]?2H 2O. Under the conditions used, the oxidation of styrene and styrene derivatives gave rise mainly to carbon-carbon double-bond cleavage, affording the corresponding products in very high yields (81-87%). Possible reaction pathways are presented.
- Estrada, Ana C.,Simoes, Mario M. Q.,Santos, Isabel C. M. S.,Neves, M. Graca P. M. S.,Cavaleiro, Jose A. S.,Cavaleiro, Ana M. V.
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- CARBONYLATIVE CROSS-COUPLING REACTION OF ARYL IODIDES WITH ALKYLALUMINUMS BY PALLADIUM COMPLEX CATALYSIS
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Secondary and/or tertiary alcohols and unsymmetrical ketones have been obtained in moderate to good yields by palladium-catalyzed (5 molpercent) carbonylative coupling of aryl iodides with alkylaluminum compounds under very mild conditions (20-50 deg C, 1 atm of carbon monoxide).The type of th reaction product depended on the aluminum reagent employed.While the selective formation of secondary alcohols was observed in the reaction with i-Bu3Al, the use of Et3Al led to a mixture of a ketone and two alcoholic products.With Et2AlCl predominantly unsymmetrical ketones were produced.In all cases, formation of directly cross-coupled products was not observed.DME and benzene can be used as solvents, but THF is unsuitable.Nickel catalysts were found to be ineffective for this reaction.
- Wakita, Yoshiaki,Yasunaga, Tomoyuki,Kojima, Masaharu
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- Hydrophobic aluminosilicate zeolites as highly efficient catalysts for the dehydration of alcohols
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Efficient dehydration of alcohols to olefins, acting as a control step in the upgrading of phenolic biofuel into alkane fuels, is an important topic in biomass conversion. Here, we report the design and synthesis of hydrophobic aluminosilicate ZSM-5 zeolites by an organosilane-modification approach (ZSM-5-OS). Water-droplet contact angle tests confirm the formation of hydrophobic surface after the modification. Interestingly, the obtained ZSM-5-OS catalysts exhibit excellent catalytic properties in dehydration of various alcohols into the corresponding olefins in water solvent. The approach reported in this work would be potentially important for developing more efficient catalysts for biomass conversion in the future.
- Xu, Shaodan,Sheng, Huadong,Ye, Tao,Hu, Dan,Liao, Shangfu
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- Protophilic versus Silicophilic Reactions in β-Substituted Silanes
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Reactivity in β-eliminations mediated by nucleophilic attack at silicon has been measured as a function of nucleophile, leaving group, and α-substituent; in some instances competition between protophilic and silicophilic reactions is observed.
- Jones, Steven L.,Stirling, Charles J. M.
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- Mechanistic Studies of Single-Step Styrene Production Catalyzed by Rh Complexes with Diimine Ligands: An Evaluation of the Role of Ligands and Induction Period
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Studies of catalytic benzene alkenylation using different diimine ligated Rh(I) acetate complexes and Cu(OAc)2 as the oxidant revealed statistically identical results in terms of activity and product selectivity. Under ethylene pressure, two representative diimine ligated rhodium(I) acetate complexes were demonstrated to exchange the diimine ligand with ethylene rapidly to form [Rh(μ-OAc)(??2-C2H4)2]2 and free diimine. Thus, it was concluded that diimine ligands are not likely coordinated to the active Rh catalysts under catalytic conditions. At 150 °C under catalytic conditions using commercial Cu(OAc)2 as the oxidant, [Rh(μ-OAc)(??2-C2H4)2]2 undergoes rapid decomposition to form catalytically inactive and insoluble Rh species, followed by gradual dissolution of the insoluble Rh to form the soluble Rh, which is active for styrene production. Thus, the observed induction period under some conditions is likely due to the formation of insoluble Rh (rapid), followed by redissolution of the Rh (slow). The Rh decomposition process can be suppressed and the catalytically active Rh species maintained by using soluble Cu(II) oxidants or Cu(OAc)2 that has been preheated. In such cases, an induction period is not observed.
- Zhu, Weihao,Luo, Zhongwen,Chen, Junqi,Liu, Chang,Yang, Lu,Dickie, Diane A.,Liu, Naiming,Zhang, Sen,Davis, Robert J.,Gunnoe, T. Brent
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- A Cp-based Molybdenum Catalyst for the Deoxydehydration of Biomass-derived Diols
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Dioxo-molybdenum complexes have been reported as catalysts for the deoxydehydration (DODH) of diols and polyols. Here, we report on the DODH of diols using [Cp*MoO2]2O as catalyst (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl). The DODH reaction was optimized using 2 mol % of [Cp*MoO2]2O, 1.1 equiv. of PPh3 as reductant, and anisole as solvent. Aliphatic vicinal diols are converted to the corresponding olefins by [Cp*MoO2]2O in up to 65 % yield (representing over 30 turnovers per catalyst) and 91 % olefin selectivity, which rivals the performance of other Mo-based DODH catalysts. Remarkably, cis-1,2-cyclohexanediol, which is known as quite a challenging substrate for DODH catalysis, is converted to 30 % of 1-cyclohexene under optimized reaction conditions. Overall, the mass balances (up to 79 %) and TONs per Mo achievable with [Cp*MoO2]2O are amongst the highest reported for molecular Mo-based DODH catalysts. A number of experiments aimed at providing insight in the reaction mechanism of [Cp*MoO2]2O have led to the proposal of a catalytic pathway in which the [Cp*MoO2]2O catalyst reacts with the diol substrate to form a putative nonsymmetric dimeric diolate species, which is reduced in the next step at only one of its Mo-centers before extrusion of the olefin product.
- Li, Jing,Lutz, Martin,Klein Gebbink, Robertus J. M.
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- Dichloropalladium(II): An Effective Catalyst for Cross-Coupling of secondary and Primary Alkyl Grignard and Alkylzinc Reagents with Organic Halides
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Several phosphine-palladium and -nickel complexes were examined for their catalytic activity in the reaction of sec-butylmagnesium chloride with bromobenzene, (E)-β-bromostyrene, 4-bromoanisole, and 2-bromotoluene.Dichloropalladium(II) was found to be by far the most active and selective catalyst to give the corresponding sec-butyl derivatives in high yields with no byproducts.The palladium-dppf complex was also found highly effective in catalyzing the reaction of n-butylmagnesium chloride and sec- and n- butylzinc chloride with organic bromides to give the corresponding cross-coupling products in high yields.The structure of PdCl2(dppf) has been determined by an X-ray diffraction study.It is proposed that the high efficiency of PdCl2(dppf) catalyst can be ascribed to its large P-Pd-P angle and small Cl-Pd-Cl angle.
- Hayashi, Tamio,Konishi, Mitsuo,Kobori, Yuji,Kumada, Makoto,Higuchi, Taiichi,Hirotsu, Ken
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- Selective Semi-Hydrogenation of Terminal Alkynes Promoted by Bimetallic Cu-Pd Nanoparticles
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The selective semi-hydrogenation of terminal alkynes was efficiently performed, under mild reaction conditions (H 2 balloon, 110 °C), promoted by a bimetallic nanocatalyst composed of copper and palladium nanoparticles (5:1 weight ratio) supported on mesostructured silica (MCM-48). The Cu-PdNPS@MCM-48 catalyst, which demonstrated to be highly chemoselective towards the alkyne functionality, is readily prepared from commercial materials and can be recovered and reused after thermal treatment followed by reduction under H 2 atmosphere.
- Buxaderas, Eduardo,Volpe, María Alicia,Radivoy, Gabriel
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- Para-hydrogen-induced polarization in rhodium complex-catalyzed hydrogenation reactions
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The homogeneous hydrogenation of PhCCH catalyzed by RhClL3, Rh(COD)L2+, and Rh(COD)dppe+ (L=PPh3; COD=1,5-cyclooctadiene; dppe=1,2-bis(diphenylphosphino)ethane) has been investigated using para-hydrogen-induced polarization (PHIP) which shows that in accord with earlier studies, for RhClL3 the addition of H2 is reversible, whereas for Rh(COD)(dppe)+ and Rh(COD)L2+, H2 addition in hydrogenation catalysis is irreversible.
- Kirss, Rein U.,Eisenberg, Richard
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- Electrochemically supported deoxygenation of epoxides into alkenes in aqueous solution
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An efficient synthesis of alkenes from epoxides in a mixture of saturated aqueous NH4Br and tetrahydrofuran (8:1) has been developed in an undivided cell fitted with a pair of zinc electrodes, and it is proposed that the reaction is mediated by Zn(0) with a hierarchically organized nanostructure.
- Huang, Jing-Mei,Lin, Zhi-Quan,Chen, Dong-Song
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- Minimizing side reactions in chemoenzymatic dynamic kinetic resolution: Organometallic and material strategies
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Chemoenzymatic dynamic kinetic resolution (DKR) of rac-1-phenyl ethanol into R-1-phenylethanol acetate was investigated with emphasis on the minimization of side reactions. The organometallic hydrogen transfer (racemization) catalyst was varied, and this
- Pollock, Ciara L.,Fox, Kevin J.,Lacroix, Sophie D.,McDonagh, James,Marr, Patricia C.,Nethercott, Alanna M.,Pennycook, Annie,Qian, Shimeng,Robinson, Linda,Saunders, Graham C.,Marr, Andrew C.
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- An evaluation of phosphine and carbene adducts of phosphite- and phosphinite-based palladacycles in the coupling of alkyl bromides with aryl boronic acids
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A range of palladacyclic catalysts and their phosphine and carbene adducts were tested in the Suzuki coupling of an alkyl bromide with phenylboronic acid and showed modest activity in some cases. Unlike with aryl halide substrates it appears that there is no particular benefit in the use of palladacycles as the palladium source. Initial data indicate that the rate determining step is not the oxidative addition of the alkyl halide substrate, but rather lies later in the catalytic cycle.
- Bedford, Robin B.,Betham, Michael,Coles, Simon J.,Frost, Robert M.,Hursthouse, Michael B.
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- Photoredox Catalyzed Sulfonylation of Multisubstituted Allenes with Ru(bpy)3Cl2 or Rhodamine B
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A highly regio- and stereoselective sulfonylation of allenes was developed that provided direct access to α, β-substituted unsaturated sulfone. By means of visible-light photoredox catalysis, the free radicals produced by p-toluenesulfonic acid reacted with multisubstituted allenes to obtain Markovnikov-type vinyl sulfones with Ru(bpy)3Cl2 or Rhodamine B as photocatalyst. The yield of this reaction could reach up to 91%. A series of unsaturated sulfones would be used for further transformation to some valuable compounds.
- Chen, Jingyun,Chen, Shufang,Jiang, Jun,Lu, Qianqian,Shi, Liyang,Xu, Zekun,Yimei, Zhao
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supporting information
(2021/11/09)
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- Selective C(sp3)?N Bond Cleavage of N,N-Dialkyl Tertiary Amines with the Loss of a Large Alkyl Group via an SN1 Pathway
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Polar disconnection of the C(sp3)?N bond of N,N-dialkyl-substituted tertiary amines via ammonium species conventionally favored the loss of the smaller alkyl group by an SN2 displacement, while selective C(sp3)?N bond cleavage by cutting off the larger alkyl group is still underdeveloped. Herein, we present a novel Pd0-catalyzed [2+2+1] annulation, proceeding through an alkyne-directed palladacycle formation and consecutive diamination with a tertiary hydroxylamine by cleaving its N?O bond and one C(sp3)?N bond, for the rapid assembly of tricyclic indoles in a single-step transformation. Noteworthy, experimental results indicated that large tert-butyl and benzyl groups were selectively cleaved via an SN1 pathway, in the presence of a smaller alkyl group (Me, Et, iPr). Under the guidance of this new finding, tricyclic indoles bearing a removable alkyl group could be exclusively obtained by using a (α-methyl)benzyl/benzyl or tert-butyl/2-(methoxycarbonyl)ethyl mixed amino source.
- Bai, Lu,Li, Linqiang,Liu, Mengtian,Luan, Xinjun,Wu, Jiaoyu
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supporting information
(2021/12/01)
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- Oxidative Alkenylation of Arenes Using Supported Rh Materials: Evidence that Active Catalysts are Formed by Rh Leaching
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This work focuses on the synthesis of supported Rh materials and study of their efficacy as pre-catalysts for the oxidative alkenylation of arenes. Rhodium particles supported on silica (Rh/SiO2; ～3.6 wt% Rh) and on nitrogen-doped carbon (Rh/NC
- Luo, Zhongwen,Whitcomb, Colby A.,Kaylor, Nicholas,Zhang, Yulu,Zhang, Sen,Davis, Robert J.,Gunnoe, T. Brent
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p. 260 - 270
(2020/12/01)
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- Heterogeneously Catalyzed Selective Decarbonylation of Aldehydes by CeO2-Supported Highly Dispersed Non-Electron-Rich Ni(0) Nanospecies
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Aldehyde decarbonylation has been extensively investigated, primarily using noble-metal catalysts; however, nonprecious-base-metal-catalyzed aldehyde decarbonylation has been hardly reported. We have established an efficient selective aldehyde decarbonylation reaction with a broad substrate scope and functional group tolerance utilizing a heterogeneous Ni(0) nanospecies catalyst supported on CeO2. The high catalytic performance is attributable to the highly dispersed and non-electron-rich Ni(0) nanospecies, which possibly suppress a side reaction producing esters and adsorbed CO-derived inhibition of the catalytic turnover, according to detailed catalyst characterization and kinetic evaluation.
- Matsuyama, Takehiro,Yatabe, Takafumi,Yabe, Tomohiro,Yamaguchi, Kazuya
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p. 13745 - 13751
(2021/11/17)
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- Method for preparing 1-cyclopropylnaphthalene
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The invention belongs to the technical field of organic synthesis, and particularly discloses a method for preparing 1-cyclopropylnaphthalene. According to the method disclosed by the invention, 1-naphthylacetophenone is adopted as a raw material, and 1-cyclopropylnaphthalene can be simply and conveniently synthesized through reduction, dehydration, cyclization and reductive dehalogenation. The method has the advantages of cheap and easily available raw materials, no need of precious metals or dangerous organic metal reagents, low raw material cost, convenient production, environmental protection and safety, and is very suitable for industrial production. The method disclosed by the invention has the advantages of high yield in each step, few byproducts and easiness in purification.
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Paragraph 0044-0046; 0050-0051; 0056-0058; 0061; 0064; ...
(2021/07/09)
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- Recoverable palladium-catalyzed carbon-carbon bond forming reactions under thermomorphic mode: Stille and suzuki-miyaura reactions
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The reaction of [PdCl2(CH3CN)2] and bis-4,40-(RfCH2OCH2)-2,2'-bpy (1a-d), where Rf = n- C11F23 (a), n-C10F21 (b), n-C9F19 (c) and n-C8F17 (d), respectively, in the presence of dichloromethane (CH2Cl2) resulted in the synthesis of Pd complex, [PdCl2[4,4'-bis-(RfCH2OCH2)-2,2'-bpy] (2a-d). The Pd-catalyzed Stille arylations of vinyl tributyltin with aryl halides were selected to demonstrate the feasibility of recycling usage with 2a as the catalyst using NMP (N-methyl-2-pyrrolidone) as the solvent at 120-150 °C. Additionally, recycling and electronic effect studies of 2a-c were also carried out for Suzuki-Miyaura reaction of phenylboronic acid derivatives, 4-X-C6H4-B(OH)2, (X = H or Ph) with aryl halide, 4-Y-C6H4-Z, (Y = CN, H or OCH3; Z = I or Br) in dimethylformamide (DMF) at 135-150 °C. At the end of each cycle, the product mixtures were cooled to lower temperature (e.g., -10 °C), and then catalysts were recovered by decantation with Pd leaching less than 1%. The products were quantified by gas chromatography/mass spectrometry (GC/MS) analysis or by the isolated yield. The complex 2a-catalyzed Stille reaction of aryl iodides with vinyl tributyltin have good recycling results for a total of 8 times, with a high yield within short period of time (1-3 h). Similarly, 2a-c-catalyzed Suzuki-Miyaura reactions also have good recycling results. The electronic effect studies from substituents in both Stille and Suzuki-Miyaura coupling reactions showed that electron withdrawing groups speed up the reaction rate. To our knowledge, this is the first example of recoverable fluorous long-chained Pd-catalyzed Stille reactions under the thermomorphic mode.
- Chan, Ka Long,Chiu, Chiao-Fan,Elakkat, Vijayanath,Lu, Norman,Shen, Chia-Rui,Su, Han-Chang,Tessema, Eskedar,Tsai, Zong-Lin
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- Indene formation upon borane-induced cyclization of arylallenes, 1,1-carboboration, and retro-hydroboration
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We herein report the reaction of arylallenes with tris(pentafluorophenyl)borane that yields pentafluorophenyl substituted indenes. The tris(pentafluorophenyl)borane induces the cyclization of the allene and transfers a pentafluorophenyl ring in the course of this reaction. A Hammett plot analysis and DFT computations indicate a 1,1-carboboration to be the C-C bond-forming step.
- Hasenbeck, Max,Wech, Felix,Averdunk, Arthur,Becker, Jonathan,Gellrich, Urs
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supporting information
p. 5518 - 5521
(2021/06/12)
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- Copper-Catalyzed Sulfonylation of Cyclobutanone Oxime Esters with Sulfonyl Hydrazides
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A copper-catalyzed radical cross-coupling of cyclobutanone oxime esters with sulfonyl hydrazides has been developed. The copper-based catalytic system proved crucial for cleavage of the C-C bond of cyclobutanone oximes and for selective C-S bond-formation involving persistent sulfonyl-metal radical intermediates. This protocol is distinguished by the low-cost catalytic system, which does not require ligand, base, or toxic cyanide salt, and by the use of readily accessible starting materials, as well as broad substrate scope, providing an efficient approach to various diversely substituted cyano-containing sulfones.
- Dong, Bingbing,Lu, Jiansha,Bao, Honghao,Zhang, Yuanyuan,Liu, Yingguo,Leng, Yuting
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supporting information
p. 3769 - 3776
(2021/07/14)
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- Electrochemistry enabled selective vicinal fluorosulfenylation and fluorosulfoxidation of alkenes
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Both sulfur and fluorine play important roles in organic synthesis, the life science, and materials science. The direct incorporation of these elements into organic scaffolds with precise control of the oxidation states of sulfur moieties is of great significance. Herein, we report the highly selective electrochemical vicinal fluorosulfenylation and fluorosulfoxidation reactions of alkenes, which were enabled by the unique ability of electrochemistry to dial in the potentials on demand. Preliminary mechanistic investigations revealed that the fluorosulfenylation reaction proceeded through a radical-polar crossover mechanism involving a key episulfonium ion intermediate. Subsequent electrochemical oxidation of fluorosulfides to fluorosulfoxides were readily achieved under a higher applied potential with the adventitious H2O in the reaction mixture.
- Jiang, Yimin,Shi, Zhaojiang,Wu, Jinnan,Wu, Shaofen,Ye, Keyin,Yu, Yi,Yuan, Yaofeng
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supporting information
(2021/11/17)
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- Palladium nanoparticlesin situsynthesized onCyclea barbatapectin as a heterogeneous catalyst for Heck coupling in water, the reduction of nitrophenols and alkynes
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This study develops an effective method for thein situsynthesis of palladium nanoparticles (PdNPs) usingCyclea barbatapectin as a green reducing and stabilizing reagent. The PdNP@pectin nanocomposite was well characterized by analysis techniques such as UV-vis, FTIR, EDX, XRD, SEM, HR-TEM and STEM-mapping. Crystalline PdNPs were found to be distributed in the size range of 1-25 nm with the highest frequency of 6-12 nm. PdNP@pectin exhibited excellent recyclable catalysis activity for the Heck coupling reaction in water medium. The kinetics and recyclability of nanoparticles were investigated for the catalytic reduction ofo-,m- andp-nitrophenol. The result showed a good catalysis efficiency with five successful recycles without compromising much. In particular, the nanocomposite was used as a catalyst for the conversion of alkynes intocis-alkenes with KOH/DMF as a hydrogenation source. The reaction was also utilized effectively for the synthesis of sex pheromones, includingPlutella xylostella((Z)-11-hexadecen-1-yl acetate) andCylas formicarius((Z)-3-dodecen-1-yl(E)-2-butenoate) with the total yields of 70% and 68%, respectively. Therefore, PdNPs supported onC. barbatapectin are promising catalysis materials for application in various fields.
- Le, Van-Dung,Le, T. Cam-Huong,Chau, Van-Trung,Le, T. Ngoc-Duyen,Dang, Chi-Hien,Vo, T. To-Nguyen,Nguyen, Trinh Duy,Nguyen, Thanh-Danh
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p. 4746 - 4755
(2021/03/22)
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- Preparation of Recyclable and Versatile Porous Poly(aryl thioether)s by Reversible Pd-Catalyzed C–S/C–S Metathesis
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Porous organic materials (polymers and COFs) have shown a number of promising properties; however, the lability of their linkages often limits their robustness and can hamper downstream industrial application. Inspired by the outstanding chemical, mechanical, and thermal resistance of the 1D polymer poly(phenylene sulfide) (PPS), we have designed a new family of porous poly(aryl thioether)s, synthesized via a mild Pd-catalyzed C–S/C–S metathesis-based method, that merges the attractive features common to porous polymers and PPS in a single material. In addition, the method is highly modular, allowing to easily introduce application-oriented functionalities in the materials for a series of environmentally relevant applications including metal capture, metal sensing, and heterogeneous catalysis. Moreover, despite their extreme chemical resistance, the polymers can be easily recycled to recover the original monomers, offering an attractive perspective for their sustainable use. In a broader context, these results clearly demonstrate the untapped potential of emerging single-bond metathesis reactions in the preparation of new, recyclable materials.
- Morandi, Bill,Rivero-Crespo, Miguel A.,Toupalas, Georgios
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supporting information
p. 21331 - 21339
(2021/12/17)
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- Selective continuous flow phenylacetylene hydrogenation over Pd-biogenic calcium carbonate
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CaCO3 obtained from Sporosarcina pasteurii isolated from agricultural soils has been employed as catalytic support for Pd that was subsequently loaded on CaCO3 by wet impregnation with a metal loading of 0.5 wt.% using Palladium acet
- Chaparro, Sandra,Martinez, José J.,Rojas, Hugo A.,Pineda, Antonio,Luque, Rafael
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p. 181 - 186
(2020/04/23)
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- Water-hydrogen-supplying iridium catalytic alkyne semi-reduction selective synthesis method Process for trans-olefines
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The method comprises the following steps: DPPE, COD, a catalyst, water and alkyne are subjected to reduction reaction of alkyne in an organic solvent, and cis-olefin is generated by reaction under nitrogen protection. The ligand DPPE, the catalyst, the water and the alkyne are subjected to a reduction reaction of alkyne in an organic solvent, and a trans-olefin is generated by the reaction under nitrogen protection. The reactor for the reduction reaction is a sealed pressure-resistant reactor, the temperature of the reduction reaction is 100 - 130 °C, and the reduction reaction time is 20 - 48h. The amount of the catalyst used is 5 - 20% of the molar amount of alkyne, and the amount of water is 10 - 50 times of the molar amount of alkyne. The ligand is used in an amount 0.2 - 5 times the molar amount of catalyst. The catalyst system disclosed by the invention has extremely high chemical reaction and stereoselectivity, and cis or trans olefinic products can be synthesized at high yield. The catalytic system has strong universality on substrates, and alkynes containing various functional groups can efficiently carry out high-selectivity reduction reaction.
- -
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Paragraph 0123-0126
(2021/09/29)
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- Method for selectively synthesizing cis-trans-olefin by catalytic alkyne semi-reduction through water-hydrogen-supplying palladium
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The method comprises the following steps: TEOA, NaOAc, a catalyst, water and alkyne are subjected to a reduction reaction of alkyne in an organic solvent to react to form cis-olefin. Ligand t-Bu2 PCl, The catalyst, water and the alkyne are subjected to a reduction reaction of alkyne in an organic solvent to react to form a trans-olefin. The reactor for the reduction reaction is a sealed pressure-resistant reactor, the temperature of the reduction reaction is 120 - 150 °C, and the reduction reaction time is 20 - 40h. The amount of the catalyst used is 5 - 20% of the molar amount of alkyne, and the amount of water is 10 - 50 times of the molar amount of alkyne. The ligand is used in an amount 2-5 times the molar amount of catalyst. In the invention, the catalyst system has extremely high chemical reaction and stereoselectivity, and cis or trans olefinic products can be synthesized at high yield. The catalytic system has strong universality on substrates, and alkynes containing various functional groups can efficiently carry out high-selectivity reduction reaction.
- -
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Paragraph 0120; 0133-0136
(2021/10/30)
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- Mild and efficient desulfurization of thiiranes with MoCl5/Zn system
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Desulfurization of a variety of thiiranes to alkenes occurs chemoselectively in high yields upon treatment with MoCl5/Zn system under mild conditions. The new methodology demonstrates high functional group tolerance toward chloro, bromo, fluoro, methoxy, ester, ether and keto groups.
- Lee, Yeong Jin,Shin, Jeong Won,Yoo, Byung Woo
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- Clean protocol for deoxygenation of epoxides to alkenes: Via catalytic hydrogenation using gold
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The epoxidation of olefin as a strategy to protect carbon-carbon double bonds is a well-known procedure in organic synthesis, however the reverse reaction, deprotection/deoxygenation of epoxides is much less developed, despite its potential utility for the synthesis of substituted olefins. Here, we disclose a clean protocol for the selective deprotection of epoxides, by combining commercially available organophosphorus ligands and gold nanoparticles (Au NP). Besides being successfully applied in the deoxygenation of epoxides, the discovered catalytic system also enables the selective reduction N-oxides and sulfoxides using molecular hydrogen as reductant. The Au NP catalyst combined with triethylphosphite P(OEt)3 is remarkably more reactive than solely Au NPs. The method is not only a complementary Au-catalyzed reductive reaction under mild conditions, but also an effective procedure for selective reductions of a wide range of valuable molecules that would be either synthetically inconvenient or even difficult to access by alternative synthetic protocols or by using classical transition metal catalysts. This journal is
- Fiorio, Jhonatan L.,Rossi, Liane M.
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p. 312 - 318
(2021/01/29)
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- Effect of relative percentage of acid and base sites on the side-chain alkylation of toluene with methanol
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K3PO4/NaX catalysts were prepared by loading potassium phosphate on NaX zeolite, and the catalytic performance was studied for the side-chain alkylation of toluene with methanol to styrene and ethylbenzene. Combined with the characte
- Li, Huijun,Wang, Bin,Wen, Yueli,Hao, Chunyao,Liu, Yuhua,Huang, Wei
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p. 12703 - 12709
(2021/04/14)
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- Mild olefin formationviabio-inspired vitamin B12photocatalysis
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Dehydrohalogenation, or elimination of hydrogen-halide equivalents, remains one of the simplest methods for the installation of the biologically-important olefin functionality. However, this transformation often requires harsh, strongly-basic conditions, rare noble metals, or both, limiting its applicability in the synthesis of complex molecules. Nature has pursued a complementary approach in the novel vitamin B12-dependent photoreceptor CarH, where photolysis of a cobalt-carbon bond leads to selective olefin formation under mild, physiologically-relevant conditions. Herein we report a light-driven B12-based catalytic system that leverages this reactivity to convert alkyl electrophiles to olefins under incredibly mild conditions using only earth abundant elements. Further, this process exhibits a high level of regioselectivity, producing terminal olefins in moderate to excellent yield and exceptional selectivity. Finally, we are able to access a hitherto-unknown transformation, remote elimination, using two cobalt catalysts in tandem to produce subterminal olefins with excellent regioselectivity. Together, we show vitamin B12to be a powerful platform for developing mild olefin-forming reactions.
- Bam, Radha,Pollatos, Alexandros S.,Moser, Austin J.,West, Julian G.
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p. 1736 - 1744
(2021/02/22)
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- Iridium(i) complexes bearing hemilabile coumarin-functionalised N-heterocyclic carbene ligands with application as alkyne hydrosilylation catalysts
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A set of iridium(i) complexes of formula IrCl(κC,η2-IRCouR′)(cod) or IrCl(κC, η2-BzIRCouR′)(cod) (cod = 1,5-cyclooctadiene; Cou = coumarin; I = imidazolin-2-carbene; BzI = benzimidazolin-2-carbene) have beeen prepared from the corresponding azolium salt and [Ir(μ-OMe)(cod)]2 in THF at room temperature. The crystalline structures of 4b and 5b show a distorted trigonal bipyramidal configuration in the solid state with a coordinated coumarin moiety. In contrast, an equilibrium between this pentacoordinated structure and the related square planar isomer is observed in solution as a consequence of the hemilability of the pyrone ring. Characterization of both species by NMR was achieved at the low and high temperature limits, respectively. In addition, the thermodynamic parameters of the equilibrium, ΔHR and ΔSR, were obtained by VT 1H NMR spectroscopy and fall in the range 22-33 kJ mol-1 and 72-113 J mol-1 K-1, respectively. Carbonylation of IrCl(κC,η2-BzITolCou7,8-Me2)(cod) resulted in the formation of a bis-CO derivative showing no hemilabile behaviour. The newly synthesised complexes efficiently catalyze the hydrosilylation of alkynes at room temperature with a preference for the β-(Z) vinylsilane isomer.
- ?zdemir, Ismail,Alici, Bülent,Castarlenas, Ricardo,Karata?, Mert Olgun,Pérez-Torrente, Jesús J.,Passarelli, Vincenzo
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p. 11206 - 11215
(2021/08/24)
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- Switchable Chemoselectivity of Reactive Intermediates Formation and Their Direct Use in A Flow Microreactor
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A chemoselectivity switchable microflow reaction was developed to generate reactive and unstable intermediates. The switchable chemoselectivity of this reaction enables a selection for one of two different intermediates, an aryllithium or a benzyl lithium, at will from the same starting material. Starting from bromo-substituted styrenes, the aryllithium intermediates were converted to the substituted styrenes, whereas the benzyl lithium intermediates were engaged in an anionic polymerization. These chemoselectivity-switchable reactions can be integrated to produce polymers that cannot be formed during typical polymerization reactions.
- Ashikari, Yosuke,Tamaki, Takashi,Kawaguchi, Tomoko,Furusawa, Mai,Yonekura, Yuya,Ishikawa, Susumu,Takahashi, Yusuke,Aizawa, Yoko,Nagaki, Aiichiro
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supporting information
p. 16107 - 16111
(2021/10/12)
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- Application of tungsten oxide supported monatomic catalyst in preparation of aromatic compound by hydrogenolysis of lignin
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The invention provides application of a tungsten oxide supported monatomic catalyst in preparation of aromatic compounds by hydrogenolysis of lignin. According to the method, various beta-O-4 model molecules, organic lignin, lignosulfonate and alkali lignin are taken as raw materials, and high-selectivity cracking of aryl ether bonds is realized in a hydrogen atmosphere at the temperature of 150-240 DEG C and the pressure of 0.7-3.0 MPa to obtain the aromatic compound. Compared with the prior art, the method has the advantages that when renewable natural biomass is used as the raw material and different lignin is used as the raw material for conversion, the highest yield of the aromatic bio-oil is 72%. Raw materials are cheap and wide in source; inorganic acid and alkali are not needed, and generation of a large amount of alkali liquor in traditional lignin catalysis is avoided; the method has the characteristics of cheap tungsten-based catalyst, green reaction process, atom economy and the like, and also has the characteristics of mild reaction conditions, high activity and selectivity, environment-friendly reaction process and the like.
- -
-
Paragraph 0044-0051
(2021/05/22)
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- Enhancing lignin depolymerizationviaa dithionite-assisted organosolv fractionation of birch sawdust
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Sodium dithionite is utilized as a reducing agent in the organosolv fractionation of lignocellulose to concomitantly produce cellulosic pulp and promote the reductive conversion of lignin into phenolic monomers. Reactions with model compounds highlight the role of sodium dithionite with respect to the reductive cleavage of β-O-4 bonds in lignin and the consequent formation of phenolic monomers.
- Brienza, Filippo,Van Aelst, Korneel,Thielemans, Karel,Sels, Bert F.,Debecker, Damien P.,Cybulska, Iwona
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supporting information
p. 3268 - 3276
(2021/05/21)
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- Polymerization of Allenes by Using an Iron(II) β-Diketiminate Pre-Catalyst to Generate High Mn Polymers
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Herein, we report an iron(II)-catalyzed polymerization of arylallenes. This reaction proceeds rapidly at room temperature in the presence of a hydride co-catalyst to generate polymers of weight up to Mn=189 000 Da. We have determined the polymer structure and chain length for a range of monomers through a combination of NMR, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) analysis. Mechanistically, we postulate that the co-catalyst does not react to form an iron(II) hydride in situ, but instead the chain growth is proceeding via a reactive Fe(III) species. We have also performed kinetic and isotopic experiments to further our understanding. The formation of a highly unusual 1,3-substituted cyclobutane side-product is also investigated.
- Durand, Derek J.,Webster, Ruth L.,Woof, Callum R.
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supporting information
p. 12335 - 12340
(2021/07/19)
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- Synthesis and structure of thienyl Fischer carbene complexes of PtIIfor application in alkyne hydrosilylation
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Transmetallation of group 6 thienylene Fischer carbene complexes to PtIIprecursors yielded new examples of neutral platinum(ii) bisethoxycarbene complexes with either 2-thienyl (T) or 5-thieno[2,3-b]thienylene (TT) carbene substituents. The use
- Lamprecht, Zandria,Malan, Frederick P.,Lotz, Simon,Bezuidenhout, Daniela I.
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p. 6220 - 6230
(2021/04/16)
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- Electrocatalytic ethylbenzene valorization using a polyoxometalate@covalent triazine framework with water as the oxygen source
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Ethylbenzene (EB) oxidation is an important transformation in the chemical industry. Herein, PMo10V2@CTF, a noble metal free electrocatalyst, was used to promote the oxidative upgrading of EB. Under ambient conditions, 65% of EB was converted to three value-added products using water as the oxygen source yielding a total Faraday efficiency of 90.4%. This excellent performance is ascribed to the homogeneous dispersion of PMo10V2and its dual role in the electrocatalytic process.
- Chi, Yingnan,Dong, Jing,Geng, Weijie,Hu, Changwen,Li, Zhen,Liu, Chengpeng
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supporting information
p. 7430 - 7433
(2021/08/03)
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- Single step production of styrene from benzene by alkenylation over palladium-anchored thermal defect rich graphitic carbon nitride catalyst
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Styrene is a widely used monomer in polymer industries for the manufacturing of plastics, rubbers and resins. The commercial styrene production process suffers from disadvantages such as requiring multiple steps, catalyst deactivation, high energy consump
- Avasthi, Kalpana,Bohre, Ashish,Jerman, Ivo,Kova?, Janez,Likozar, Bla?,Ter?an, Janvit
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- Dehydrogenative alcohol coupling and one-pot cross metathesis/dehydrogenative coupling reactions of alcohols using Hoveyda-Grubbs catalysts
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In this study,in situformed ruthenium hydride species that were generated from Grubbs type catalysts are used as efficient catalysts for dehydrogenative alcohol coupling and sequential cross-metathesis/dehydrogenative coupling reactions. The selectivity of Grubbs first generation catalysts (G1) in dehydrogenative alcohol coupling reactions can be tuned for the ester formation in the presence of weak bases, while the selectivity can be switched to the β-alkylated alcohol formation using strong bases. The performance of Hoveyda-Grubbs 2nd generation catalyst (HG2) was improved in the presence of tricyclohexylphosphine for the selective synthesis of ester derivatives with weak and strong bases in quantitative yields. Allyl alcohol was used as self and cross-metathesis substrate for the HG2 catalyzed sequential cross-metathesis/dehydrogenative alcohol coupling reactions to obtain γ-butyrolactone and long-chain ester derivatives in quantitative yields.
- ?zer, Halenur,Arslan, Dilan,?ztürk, Bengi ?zgün
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p. 5992 - 6000
(2021/04/12)
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- Electron-Catalyzed Aminocarbonylation: Synthesis of α,β-Unsaturated Amides from Alkenyl Iodides, CO, and Amines
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Aminocarbonylation of alkenyl iodides with CO and amines proceeded under heating to produce α,β-unsaturated amides in good yields (23 examples, 71% average yield). This catalyst-free method exhibited good functional-group tolerance, and open a straightforward access to functionalized acrylamides, as illustrated by the synthesis of Ilepcimide. A hybrid radical/ionic mechanism involving chain electron transfer is proposed for this transformation.
- Picard, Baptiste,Fukuyama, Takahide,Bando, Takanobu,Hyodo, Mamoru,Ryu, Ilhyong
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supporting information
p. 9505 - 9509
(2021/12/09)
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- Selective Construction of C?C and C=C Bonds by Manganese Catalyzed Coupling of Alcohols with Phosphorus Ylides
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Herein, we report the manganese catalyzed coupling of alcohols with phosphorus ylides. The selectivity in the coupling of primary alcohols with phosphorus ylides to form carbon-carbon single (C?C) and carbon-carbon double (C=C) bonds can be controlled by the ligands. In the conversion of more challenging secondary alcohols with phosphorus ylides the selectivity towards the formation of C?C vs. C=C bonds can be controlled by the reaction conditions, namely the amount of base. The scope and limitations of the coupling reactions were thoroughly evaluated by the conversion of 21 alcohols and 15 ylides. Notably, compared to existing methods, which are based on precious metal complexes as catalysts, the present catalytic system is based on earth abundant manganese catalysts. The reaction can also be performed in a sequential one-pot reaction generating the phosphorus ylide in situ followed manganese catalyzed C?C and C=C bond formation. Mechanistic studies suggest that the C?C bond was generated via a borrowing hydrogen pathway and the C=C bond formation followed an acceptorless dehydrogenative coupling pathway. (Figure presented.).
- Liu, Xin,Werner, Thomas
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supporting information
p. 1096 - 1104
(2020/12/31)
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- Photochemical Strategy for Carbon Isotope Exchange with CO2
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A photocatalytic approach for carbon isotope exchange is reported. Utilizing [13C]CO2 and [14C]CO2 as primary C1 sources, this protocol allows the insertion of the desired carbon isotope into phenyl acetic acids without the need for structural modifications or prefunctionalization in one single step. The exceptionally mild conditions required for this traceless transformation are in stark contrast with those for previous methods requiring the use of harsh thermal conditions.
- Babin, Victor,Talbot, Alex,Labiche, Alexandre,Destro, Gianluca,Del Vecchio, Antonio,Elmore, Charles S.,Taran, Frédéric,Sallustrau, Antoine,Audisio, Davide
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p. 2968 - 2976
(2021/03/09)
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- Room temperature depolymerization of lignin using a protic and metal based ionic liquid system: an efficient method of catalytic conversion and value addition
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Lignin is one of the most abundant biopolymer which can be utilized to synthesize various chemicalsviaits depolymerization. However, depolymerization of lignin generally occurs under very harsh conditions. Herein, we report the efficient depolymerization of ligninviadissolution in a mixed ionic liquid system: ethyl ammonium nitrate (EAN) + prolinium tetrachloromanganate(ii) [Pro]2[MnCl4] at 35 °C and under atmospheric pressure conditions. The high dissolution of lignin in ethyl ammonium nitrate provided a large number of H-bonding sites leading to the cracking of lignin and subsequent oxidative conversion by [Pro]2[MnCl4]viathe formation of metal-oxo bonding between Mn and lignin molecules. The extracted yield of vanillin was found to be 18-20% on lignin weight basisviaGC-MS analysis. The depolymerization of lignin was confirmed by SEM, FT-IR and PXRD analysis. Since lignin contains UV-absorbing functional groups, the regenerated biomass after the recovery of the depolymerized products was further utilized to synthesize a UV-shielding material. The constructed films from such a material exhibited a high SPF value of 22 and were found to be very effective by limiting the UV degradation of rhodamine B thus making the lignin valorization process economically viable and environmentally sustainable.
- Mehta, Mohit J.,Kulshrestha, Akshay,Sharma, Shweta,Kumar, Arvind
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p. 1240 - 1247
(2021/02/26)
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- Rhodium-Catalyzed Regioselective Hydroformylation of Alkynes to α,β-Unsaturated Aldehydes Using Formic Acid
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A rhodium-catalyzed hydroformylation of alkynes with formic acid was developed. The method provides α,β-unsaturated aldehydes in high yield and E-selectivity without the need to handle toxic CO gas.
- Fan, Chao,Hou, Jing,Chen, Yu-Jia,Ding, Kui-Ling,Zhou, Qi-Lin
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supporting information
p. 2074 - 2077
(2021/04/05)
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- The effect of viscosity on the coupling and hydrogen-abstraction reaction between transient and persistent radicals
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The effect of viscosity on the radical termination reaction between a transient radical and a persistent radical undergoing a coupling reaction (Coup) or hydrogen abstraction (Abst) was examined. In a non-viscous solvent, such as benzene (bulk viscosity bulk 99% Coup/Abst selectivity, but Coup/Abst decreased as the viscosity increased (89/11 in PEG400 at 25 °C [bulk = 84 mPa s]). While bulk viscosity is a good parameter to predict the Coup/Abst selectivity in each solvent, microviscosity is the more general parameter. Poly(methyl methacrylate) (PMMA)-end radicals had a more significant viscosity effect than polystyrene (PSt)-end radicals, and the Coup/Abst ratio of the former dropped to 50/50 in highly viscous media (bulk = 3980 mPa s), while the latter maintained high Coup/ Abst selectivity (84/16). These results, together with the low thermal stability of dormant PMMA-TEMPO species compared with that of PSt-TEMPO species, are attributed to the limitation of the nitroxide-mediated radical polymerization of MMA. While both organotellurium and bromine compounds were used as precursors of radicals, the former was superior to the latter for the clean generation of radical species.
- Li, Xiaopei,Kato, Tatsuhisa,Nakamura, Yasuyuki,Yamago, Shigeru
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p. 966 - 972
(2021/04/29)
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- 16-Electron Nickel(0)-Olefin Complexes in Low-Temperature C(sp2)-C(sp3) Kumada Cross-Couplings
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Investigations into the mechanism of the low-temperature C(sp2)-C(sp3) Kumada cross-coupling catalyzed by highly reduced nickel-olefin-lithium complexes revealed that 16-electron tris(olefin)nickel(0) complexes are competent catalysts for this transformation. A survey of various nickel(0)-olefin complexes identified Ni(nor)3as an active catalyst, with performance comparable to that of the previously described Ni-olefin-lithium precatalyst. We demonstrate that Ni(nor)3, however, is unable to undergo oxidative addition to the corresponding C(sp2)-Br bond at low temperatures (a nickel(0)-alkylmagnesium complex. We demonstrate that this unique heterobimetallic complex is now primed for reactivity, thus cleaving the C(sp2)-Br bond and ultimately delivering the C(sp2)-C(sp3) bond in high yields.
- Lutz, Sigrid,Nattmann, Lukas,N?thling, Nils,Cornella, Josep
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supporting information
p. 2220 - 2230
(2021/05/07)
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- Norrish type II reactions of acyl azolium salts
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The photochemical reactivity of acyl azolium salts derived from aliphatic carboxylic acids has been investigated. These species, which serve as models for intermediates generated in N-heterocyclic carbene (NHC) organocatalysis, undergo Norrish type II elimination reactions under irradiation with UVA light in analogy to structurally related aromatic ketones. Moreover, efficient Norrish-Yang cyclization was observed from an adamantyl-substituted derivative. These results further demonstrate the ability of NHCs to influence the absorption properties and photochemical reactivity of carbonyl groups during a catalytic cycle.
- Hopkinson, Matthew N.,Mavroskoufis, Andreas,Rieck, Arielle
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- KO-t-Bu Catalyzed Thiolation of β-(Hetero)arylethyl Ethers via MeOH Elimination/hydrothiolation
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Herein, we describe a KO-t-Bu catalyzed thiolation of β-(hetero)arylethyl ethers through MeOH elimination to form (hetero)arylalkenes followed by anti-Markovnikov hydrothiolation to afford linear thioethers. The system works well with a variety of β-(hetero)arylethyl ethers, including electron-deficient, electron-neutral, electron-rich, and branched substrates and a range of aliphatic and aromatic thiols.
- Shigeno, Masanori,Shishido, Yoshiteru,Hayashi, Kazutoshi,Nozawa-Kumada, Kanako,Kondo, Yoshinori
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supporting information
p. 3932 - 3935
(2021/08/24)
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- Beyond Takai's Olefination Reagent: Persistent Dehalogenation Emerges in a Chromium(III)-μ3-Methylidyne Complex
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Reaction of CHI3 with six equivalents of CrCl2 in THF at low temperatures affords [Cr3Cl3(μ2-Cl)3(μ3-CH)(thf)6] as the first isolable high-yield CrIII μ3-methylidyne complex. Substitution of the terminal chlorido ligands via salt metathesis with alkali-metal cyclopentadienides generates isostructural half-sandwich chromium(III)-μ3-methylidynes [CpR3Cr3(μ2-Cl)3(μ3-CH)] (CpR=C5H5, C5Me5, C5H4SiMe3). Side and decomposition products of the Cl/CpR exchange reactions were identified and structurally characterized for [Cr4(μ2-Cl)4(μ2-I)2(μ4-O)(thf)4] and [(η5-C5H4SiMe3)CrCl(μ2-Cl)2Li(thf)2]. The Cl/CpR exchange drastically changed the ambient-temperature effective magnetic moment μeff from 9.30/9.11 μB (solution/solid) to 3.63/4.32 μB (CpR=C5Me5). Reactions of [Cr3Cl3(μ2-Cl)3(μ3-CH)(thf)6] with aldehydes and ketones produce intricate mixtures of species through oxy/methylidyne exchange, which were partially identified as radical recombination products through GC/MS analysis and 1H NMR spectroscopy.
- Anwander, Reiner,Langmann, Jan,Maichle-M?ssmer, C?cilia,Scherer, Wolfgang,Trzmiel, Simon,Werner, Daniel
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p. 20049 - 20054
(2021/08/06)
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- Cascade Reductive Friedel-Crafts Alkylation Catalyzed by Robust Iridium(III) Hydride Complexes Containing a Protic Triazolylidene Ligand
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The synthesis of complex molecules like active pharmaceutical ingredients typically requires multiple single-step reactions, in series or in a modular fashion, with laborious purification and potentially unstable intermediates. Cascade processes offer attractive synthetic remediation as they reduce time, energy, and waste associated with multistep syntheses. For example, triarylmethanes are traditionally prepared via several synthetic steps, and only a handful of cascade routes are known with limitations due to high catalyst loadings. Here, we present an expedient catalytic cascade process to produce triarylmethanes. For this purpose, we have developed a bifunctional iridium system as the efficient catalyst to build heterotriaryl synthons via reductive Friedel-Crafts alkylation from ketones, arenes, and hydrogen. The catalytically active species were generated in situ from a robust triazolyl iridium(III) hydride complex and acid and is composed of a metal-bound hydride and a proximal ligand-bound proton for reversible dihydrogen release. These complexes catalyze the direct hydrogenation of ketones at slow rates followed by dehydration. Appropriate adjustment of the conditions successfully intercepts this dehydration and leads instead to efficient C-C coupling and Friedel-Crafts alkylation. The scope of this cascade process includes a variety of carbonyl substrates such as aldehydes, (alkyl)(aryl)ketones, and diaryl ketones as precursor electrophiles with arenes and heteroarenes for Friedel-Crafts coupling. The reported method has been validated in a swift one-step synthesis of the core structure of a potent antibacterial agent. Excellent yields and exquisite selectivities were achieved for this cascade process with unprecedentedly low iridium loadings (0.02 mol %). Moreover, the catalytic activity of the protic system is significantly higher than that of an N-methylated analogue, confirming the benefit of the Ir-H/N-H hydride-proton system for high catalytic performance.
- Albrecht, Martin,Alshakova, Iryna D.
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p. 8999 - 9007
(2021/07/31)
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- Self-Assembled Open Porous Nanoparticle Superstructures
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Imparting porosity to inorganic nanoparticle assemblies to build up self-assembled open porous nanoparticle superstructures represents one of the most challenging issues and will reshape the property and application scope of traditional inorganic nanoparticle solids. Herein, we discovered how to engineer open pores into diverse ordered nanoparticle superstructures via their inclusion-induced assembly within 1D nanotubes, akin to the molecular host-guest complexation. The open porous structure of self-assembled composites is generated from nonclose-packing of nanoparticles in 1D confined space. Tuning the size ratios of the tube-to-nanoparticle enables the structural modulation of these porous nanoparticle superstructures, with symmetries such as C1, zigzag, C2, C4, and C5. Moreover, when the internal surface of the nanotubes is blocked by molecular additives, the nanoparticles would switch their assembly pathway and self-assemble on the external surface of the nanotubes without the formation of porous nanoparticle assemblies. We also show that the open porous nanoparticle superstructures can be ideal candidate for catalysis with accelerated reaction rates.
- Liu, Rongjuan,Wei, Jingjing,Wei, Yanze,Yang, Zhijie,Zhang, Fenghua
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supporting information
(2021/08/20)
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- Site-Selective Acceptorless Dehydrogenation of Aliphatics Enabled by Organophotoredox/Cobalt Dual Catalysis
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The value of catalytic dehydrogenation of aliphatics (CDA) in organic synthesis has remained largely underexplored. Known homogeneous CDA systems often require the use of sacrificial hydrogen acceptors (or oxidants), precious metal catalysts, and harsh reaction conditions, thus limiting most existing methods to dehydrogenation of non- or low-functionalized alkanes. Here we describe a visible-light-driven, dual-catalyst system consisting of inexpensive organophotoredox and base-metal catalysts for room-temperature, acceptorless-CDA (Al-CDA). Initiated by photoexited 2-chloroanthraquinone, the process involves H atom transfer (HAT) of aliphatics to form alkyl radicals, which then react with cobaloxime to produce olefins and H2. This operationally simple method enables direct dehydrogenation of readily available chemical feedstocks to diversely functionalized olefins. For example, we demonstrate, for the first time, the oxidant-free desaturation of thioethers and amides to alkenyl sulfides and enamides, respectively. Moreover, the system's exceptional site selectivity and functional group tolerance are illustrated by late-stage dehydrogenation and synthesis of 14 biologically relevant molecules and pharmaceutical ingredients. Mechanistic studies have revealed a dual HAT process and provided insights into the origin of reactivity and site selectivity.
- Zhou, Min-Jie,Zhang, Lei,Liu, Guixia,Xu, Chen,Huang, Zheng
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supporting information
p. 16470 - 16485
(2021/10/20)
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- Poisoning effect of N-containing compounds on performance of Raney nickel in transfer hydrogenation
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The effect of amines, imines and heterocycle compounds on conversion has been studied in transfer hydrogenation of camphor and 2-PrOH catalyzed by Raney nickel. Small amount (5 mol% to nickel) of N-containing compound significantly decreases catalyst activity. It has been shown that the poisoning effect mostly depends on molecular size of amines and heterocyclic compounds. For aniline and cyclohexylamine the dependence of camphor conversion on poison/nickel ratio was obtained. Additionally, benzaldehyde, cinnamaldehyde demonstrated higher reactivity compared corresponding imines under transfer hydrogenation conditions. Obtained data explain low activity of nickel-based catalysts when N-containing compounds are presented in reaction mixture.
- Martyanov, Oleg N.,Philippov, Alexey A.
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- Radical induced disproportionation of alcohols assisted by iodide under acidic conditions
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The disproportionation of alcohols without an additional reductant and oxidant to simultaneously form alkanes and aldehydes/ketones represents an atom-economical transformation. However, only limited methodologies have been reported, and they suffer from a narrow substrate scope or harsh reaction conditions. Herein, we report that alcohol disproportionation can proceed with high efficiency catalyzed by iodide under acidic conditions. This method exhibits high functional group tolerance including aryl alcohol derivatives with both electron-withdrawing and electron-donating groups, furan ring alcohol derivatives, allyl alcohol derivatives, and dihydric alcohols. Under the optimized reaction conditions, a 49% yield of 5-methyl furfural and a 49% yield of 2,5-diformylfuran were obtained simultaneously from 5-hydroxymethylfurfural. An initial mechanistic study suggested that the hydrogen transfer during this redox disproportionation occurred through the inter-transformation of HI and I2. Radical intermediates were involved during this reaction.
- Huang, Yang,Jiang, Haiwei,Li, Teng,Peng, Yang,Rong, Nianxin,Shi, Hexian,Yang, Weiran
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supporting information
p. 8108 - 8115
(2021/10/29)
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- Olefination via Cu-Mediated Dehydroacylation of Unstrained Ketones
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The dehydroacylation of ketones to olefins is realized under mild conditions, which exhibits a unique reaction pathway involving aromatization-driven C-C cleavage to remove the acyl moiety, followed by Cu-mediated oxidative elimination to form an alkene between the α and β carbons. The newly adopted N′-methylpicolinohydrazonamide (MPHA) reagent is key to enable efficient cleavage of ketone C-C bonds at room temperature. Diverse alkyl- and aryl-substituted olefins, dienes, and special alkenes are generated with broad functional group tolerance. Strategic applications of this method are also demonstrated.
- Dong, Guangbin,Xu, Yan,Zhou, Xukai
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supporting information
p. 20042 - 20048
(2021/12/03)
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- An Iron-Based Dehydration Catalyst for Selective Formation of Styrene
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We report the synthesis and crystal structure of [Fe(OTf)2(FOX)] (A). This robust iron(II) complex was successfully applied as a homogeneous catalyst for the dehydration of 1-phenylethanol to styrene. Even at low catalyst loadings and moderate reaction temperatures,A showed a high catalytic efficiency. It was found to selectively activate the benzylic alcohol group of 1-phenylethanol. This is challenging since the vinyl system of styrene is highly reactive. In contrast to most of the other dehydration processes, the use of a Br?nsted acid was not necessary. Furthermore, mechanistic insights into this E1-type transformation and its competing SN1-type side reactions are reported. [Fe(cHexOH)(OTf)(FOX)][OTf] (B), an alcohol adduct ofA, [Fe(H2O)2(FOX)][OTf]2(C), the completely hydrated derivative ofA, and [μ-O{Fe(OTf)(FOX)}2][OTf]2(D), a dinuclear oxidation product ofA, were also characterized and are discussed.
- Brennessel, William W.,Jones, William D.,Nachtigall, Olaf,Vanderweide, Andrew I.
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p. 10885 - 10891
(2021/09/14)
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- Method for preparing olefine aldehyde by catalyzing terminal alkyne or terminal conjugated eneyne and diphosphine ligand used in method
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The invention discloses a method for preparing olefine aldehyde by catalyzing terminal alkyne or terminal conjugated eneyne and a diphosphine ligand used in the method. According to the invention, indole-substituted phosphoramidite diphosphine ligand which is stable in air and insensitive to light is synthesized by utilizing a continuous one-pot method, and the indole-substituted phosphoramidite diphosphine ligand and a rhodium catalyst are used for jointly catalyzing to successfully achieve a hydroformylation reaction of aromatic terminal alkyne and terminal conjugated eneyne under the condition of synthesis gas for the first time, so that an olefine aldehyde structure compound can be rapidly and massively prepared, and particularly, a polyolefine aldehyde structure compound which is more difficult to synthesize in the prior art can be easily prepared and synthesized, and a novel method is provided for synthesis and modification of drug molecules, intermediates and chemical products.
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Paragraph 0121-0124
(2021/05/29)
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- Preparation method of Nysted reagent
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The invention provides a preparation method of a Nysted reagent, which comprises the following steps: adding zinc scraps into an organic solvent, stirring, then adding a catalyst and dibromomethane, and reacting to obtain the Nysted reagent after the reaction is finished. According to the method, zinc powder is replaced with the zinc scraps, the step of activating the zinc powder in the zinc powder preparation process is omitted, emission of three wastes is reduced, the production cost is reduced, the production safety is improved, and the method is more suitable for industrial production and application. The method has the advantages of simple catalyst preparation, low cost, ultrahigh reaction activity, low reaction temperature, almost no need of heating, high safety and controllability.
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Paragraph 0025; 0034-0035
(2021/06/02)
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- Selective Rhodium-Catalyzed Hydroformylation of Terminal Arylalkynes and Conjugated Enynes to (Poly)enals Enabled by a π-Acceptor Biphosphoramidite Ligand
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The hydroformylation of terminal arylalkynes and enynes offers a straightforward synthetic route to the valuable (poly)enals. However, the hydroformylation of terminal alkynes has remained a long-standing challenge. Herein, an efficient and selective Rh-catalyzed hydroformylation of terminal arylalkynes and conjugated enynes has been achieved by using a new stable biphosphoramidite ligand with strong π-acceptor capacity, which affords various important E-(poly)enals in good yields with excellent chemo- and regioselectivity at low temperatures and low syngas pressures.
- Zhao, Jiangui,Zheng, Xueli,Tao, Shaokun,Zhu, Yuxin,Yi, Jiwei,Tang, Songbai,Li, Ruixiang,Chen, Hua,Fu, Haiyan,Yuan, Maolin
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supporting information
p. 6067 - 6072
(2021/08/16)
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- Visible-Light-Mediated Divergent Silylfunctionalization of Alkenes
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1,2-Silylfunctionalization of alkenes is an efficient way to construct highly functionalized silicon-containing compounds. However, examples of 1,2-silylfunctionalization of alkenes using readily available hydrosilanes are limited. Herein, we present a visible-light-mediated divergent 1,2-silylfunctionalization of alkenes using hydrosilane under ambient conditions. A series of β-Alkoxy, β-Alkylthio, β-hydroxy, and β-indolyl silanes was obtained in good to excellent yields. Moreover, vinylsilanes were successfully prepared in the absence of an additional nucleophile.
- Zheng, Ming,Hou, Jing,Hua, Li-Li,Tang, Wan-Ying,Zhan, Le-Wu,Li, Bin-Dong
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supporting information
p. 5128 - 5132
(2021/07/20)
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- Direct Nucleophilic Substitution of Alcohols Using an Immobilized Oxovanadium Catalyst
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Direct nucleophilic substitution of alcohols with thiols or carbon nucleophiles was achieved using a mesoporous silica-supported oxovanadium catalyst (VMPS4). Benzyl and allyl alcohols were compatible in this reaction under mild conditions, affording the products in high yields. The VMPS4 catalyst showed excellent chemoselectivity toward alcohols in the presence of acid-labile functional groups, which is in contrast to that observed for the commonly used Lewis acid catalysts, which exhibit poor selectivity. The VMPS4 catalyst could be recycled by simple centrifugation, and the catalytic activity was maintained over seven cycles.
- Nishio, Tomoya,Yoshioka, Shin,Hasegawa, Kai,Yahata, Kenzo,Kanomata, Kyohei,Akai, Shuji
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supporting information
p. 4417 - 4422
(2021/07/16)
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