- 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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- The effect of Al2O3 and ionic liquids in palladium catalyzed arylation of cyclohexene. Interaction of Hg(0) with immobilized palladium
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Three-component systems containing Pd(OAc)2, Al2O3, and an IL (IL = ionic liquid) were applied in the Heck arylation of cyclohexene. The highest productivity and selectivity to 4-phenylcyclohexene was noted in reaction catalyzed by Pd/Al2O3 in the presence of a small amount of an IL, dimethyldidodecylammonium lactate (C). The addition of Al2O3 alone to the reaction catalyzed by soluble precursors, PdCl2(PhCN)2 or Pd(OAc)2 and IL, remarkably increased conversion to 4-phenylcyclohexene. Hg(0) inhibited the reaction catalyzed by Pd/Al2O3 by formation of Pd-Hg amalgam immobilized on Al2O3. SEM/EDX studies of Pd/Al2O3 performed after treatment with Hg(0) showed that the IL modified the surface properties of Pd/Al2O3.
- Wirwis,Gil,Pernak,Trzeciak
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p. 188 - 195
(2015/11/23)
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- Mechanistic insights into Br?nsted acid-induced nucleophilic substitution of aliphatic imidazole carbamate with halide ions
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Herein we report interesting reactivity of imidazole carbamate towards nucleophilic substitution with halide ions under Br?nsted acidic conditions. Depending upon reaction conditions, halide ions could readily attack the carboxyl position and trigger decarboxylative alkyl halide formation. Alternatively, halide ions were also found to competitively undergo nucleophilic acyl substitution, which ultimately results in the generation of carbonate dimerization product.
- Saputra, Mirza A.,Forgey, Rashel L.,Henry, Jeffrey L.,Kartika, Rendy
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p. 1392 - 1396
(2015/03/04)
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- A mild method for eliminating alkyl ethers to alkenes
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A method for the conversion of methyl ethers into alkenes is described. In a one-step and mild procedure, both conjugated and isolated cyclic alkenes are accessible in mostly good yields using triflic anhydride in combination with triethylamine. This elimination procedure can also be applied to ethyl and benzyl ethers.
- Lindner, Stephanie,Braese, Stefan
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p. 29439 - 29442
(2014/08/05)
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- Achieving vinylic selectivity in Mizoroki-heck reaction of cyclic olefins
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In Heck reactions of cyclic olefins, the products usually have aryl groups that end up at the allylic and/or homoallylic position. We herein report new selectivity that adds aryl groups to the vinylic position. Cyclic olefins of various ring size worked well. The desired isomers were produced by palladium-hydride-catalyzed isomerization of the initial products. Thus, a specific catalyst must be used so that it can perform two jobs under one set of reaction conditions. Copyright
- Wu, Xiaojin,Lu, Yunpeng,Hirao, Hajime,Zhou, Jianrong
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supporting information
p. 6014 - 6020
(2013/06/26)
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- Copper-catalyzed alkene arylation with diaryliodonium salts
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Alkenes and arenes represent two classes of feedstock compounds whose union has fundamental importance to synthetic organic chemistry. We report a new approach to alkene arylation using diaryliodonium salts and Cu catalysis. Using a range of simple alkenes, we have shown that the product outcomes differ significantly from those commonly obtained by the Heck reaction. We have used these insights to develop a number of new tandem and cascade reactions that transform readily available alkenes into complex arylated products that may have broad applications in chemical synthesis.
- Phipps, Robert J.,McMurray, Lindsay,Ritter, Stefanie,Duong, Hung A.,Gaunt, Matthew J.
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supporting information; experimental part
p. 10773 - 10776
(2012/08/07)
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- Selective heck arylation of cyclohexene with homogeneous and heterogeneous palladium catalysts
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Palladium catalysts containing Pd(II) supported on Al2O 3 and alumina-based mixed oxides, Al2O3- ZrO2, Al2O3-CeO2, and Al 2O3-Fe2O3, are very effective in the Heck coupling of iodobenzene with cyclohexene in DMF solution. The best results, up to 81% of monoarylated products with a selectivity to 4-phenylcyclohexene (3) close to 90% were obtained with KOH as a base. The catalytic activity of palladium supported on aluminabased oxides was compared with that of homogeneous precursors, such as Pd(OAc)2 and PdCl 2(PhCN)2, used in [Bu4N]Br as the reaction medium. Under such conditions homogeneous systems were more selective and produced up to 60% of monoarylated products with a selectivity to 3 close to 60%. Copyright
- Mieczynska, Ewa,Trzeciak, Anna M.
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scheme or table
p. 2166 - 2177
(2010/08/04)
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- Complete study of the pyrolysis and gasification of scrap tires in a pilot plant reactor
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The pyrolysis and gasification of tires was investigated in a pilot plant reactor provided with a system for condensation of semivolatile matter. The study comprised experiments at 450°, 750°, and 1000°C both in nitrogen and 10% oxygen atmospheres. In the gas phase, only methane and benzene yields increased with temperature until 1000°C. In the liquids, the main components were styrene, limonene, and isoprene. The solid fraction (including soot) increased with temperature. Zinc content of the char decreased with increasing temperature. Analysis of the surface area of the solids showed that the area was similar in all cases to that of a commercial carbon black. The higher surface of the soot with respect to the chars was observed. The results coincided with published findings, i.e., kinetic severity function values would produce 0.2% of methane at 450°C and 4.5% at 750°-1000°C.
- Conesa, Juan A.,Martin-Gullon,Font,Jauhiainen
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p. 3189 - 3194
(2008/12/21)
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- Oxygen-promoted Pd(II) catalysis for the coupling of organoboron compounds and olefins
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(Matrix presented) Reported herein is a mild and efficient Pd(ll) catalysis, leading to the formation of carbon-carbon bonds between a broad spectrum of organoboron compounds and alkenes. Molecular oxygen was employed to reoxidize the resultant Pd(0) species back to Pd(ll) during catalytic cycles. This oxygen protocol promoted the desired Pd(ll) catalysis, whereas it retarded competing Pd(0) catalytic pathways such as Heck or Suzuki couplings.
- Jung, Young Chun,Mishra, Rajesh Kumar,Yoon, Cheol Hwan,Jung, Kyung Woon
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p. 2231 - 2234
(2007/10/03)
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- Heck reactions in hydrothermal, sub-critical water: Water density as an important reaction variable
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Heck coupling reactions of iodobenzene and cyclohexene in sub-critical water illustrate the importance of water density as a reaction variable. Altering the water density from 0.03 to 0.84 g/mL and the reaction pressure from 30 to greater than 213 bar at 225°C changed both product and isomer yields. The multiple physical effects of water density were also explored by the addition of ionic salts. Changing the isothermal state of the liquid water, measurably altered coupling reaction pathways suggesting that changes in solvent-solute interactions can influence transition states favoring some configurations and disfavoring others.
- Gron, Liz U,LaCroix, Jeanna E,Higgins, Cortney J,Steelman, Karen L,Tinsley, Amanda S
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p. 8555 - 8557
(2007/10/03)
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- Synthesis of alkenylboronates via palladium-catalyzed borylation of alkenyl triflates (or Iodides) with pinacolborane
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Various alkenyl iodides and triflates were borylated with pinacolborane in the presence of Et3N and a catalytic amount of PdCl2(dppf) and AsPh3 to afford the corresponding alkenylboronates in good yields.
- Murata, Miki,Oyama, Takashi,Watanabe, Shinji,Masuda, Yuzuru
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p. 778 - 780
(2007/10/03)
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- Highly selective palladium-catalyzed Heck reactions of aryl bromides with cycloalkenes
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Formula presented The influence of palladium catalysts and reaction conditions on the selectivity of Heck reactions of aryl bromides with cyclohexene and cyclopentene has been investigated. It is shown that the addition of DMSO as a cosolvent leads to improved selectivities of nonconjugated aryl olefins. On the other hand, high selectivities for conjugated arylcyclopentenes have been obtained with the catalytic system DMA/Na2-CO3/Pd2(dba) 3·dba/PCy3.
- Hartung, Christian G.,Koehler, Klaus,Beller, Matthias
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p. 709 - 711
(2008/02/11)
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- Catalytic electrochemical reduction of 1,2-dibromocyclohexane derivatives at carbon electrodes modified with cobalt porphyrin siloxane films
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The electrochemical reduction of trans-1,2-dibromocylohexanes is catalyzed effectively by Co(II) porphyrins at potentials ≥ 1 V positive of the uncatalyzed case. With siloxane films on carbon electrodes containing a specially designed, diethylene glycol spacered Co-porphyrin, high catalytic currents are observed. Preparative current yields of 65% on a mmol scale are obtained with average calculated catalyst turnover numbers of ca. 5000.
- Demel, Roswitha,Doetterl, Eleonore,Merz, Andreas
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p. 1038 - 1042
(2007/10/03)
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- Enantioselective preparation of 4-substituted cyclohexenes by radical fragmentation of sulfoxides
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(equation presented) Radical fragmentation of o-bromophenyl sulfoxides is reported. Starting from enantiomerically pure material, 4-substituted cyclohexene derivatives have been prepared with enantiomeric excesses between 70% and 86%. The key step of the process is a diastereoselective abstraction of a hydrogen atom by the initial aryl radical. The highest enantiomeric exesses have been obtained in the presence of aluminum Lewis acids.
- Imboden, Christoph,Villar, Felix,Renaud, Philippe
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p. 873 - 875
(2008/02/09)
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- Cyclization and fluorination of 5-hexenols with boron trifluoride etherate. Stereoselective synthesis of (optically active) fluorinated cyclohexane derivatives by cyclization of ω-pentenyl pentadienol tricarbonyl iron complexes
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Monofluorinated cyclohexane derivatives are obtained by treatment of ω-pentenyl pentadienol tricarbonyl iron complexes with boron trifluoride etherate. The reaction is stereoselective, so that optically active fluorocyclohexanes can be obtained from readily available enantiomerically pure starting complexes. This fluorocyclization reaction with the cheap reagent BF3.Et2O is not restricted to transition-metal coordinated substrates, working also with simple ω-pentenyl benzylic alcohols.
- Franck-Neumann, Michel,Geoffroy, Philippe,Hanss, David
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p. 8487 - 8490
(2007/10/03)
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- Tailoring aqueous solvents for organic reactions: Heck coupling reactions in high temperature water
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High temperature water is demonstrated to be an effective solvent for Heck coupling reactions of aromatic halides with cyclic alkenes without the addition of co-solvents or specialized ligands. Reactions in the presence of LiCl and quaternary ammonium salts indicate that the reaction takes place in the aqueous phase.
- Gron,Tinsley
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p. 227 - 230
(2007/10/03)
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- Dehydration of α-silylalcohols in the reductive conversion of esters and ketones into alkenes
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The conversion of esters and ketones into easily dehydrated α-silylated alcohols, and protodesilylation of the resultant vinylsilanes, gives alkenes under relatively mild acidic conditions.
- Chenede, Alain,Abd.Rahman, Noorsaadah,Fleming, Ian
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p. 2381 - 2382
(2007/10/03)
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- Fluorination of secondary and primary alcohols by thermal decomposition of electrochemically generated alkoxy triphenylphosphonium tetrafluoroborates
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Replacement of hydroxyl groups in secondary and primary alcohols (1) with a fluorine atom arising from tetrafluoroborate anion has been performed by the electrochemical formation of alkoxy triphenylphosphonium tetrafluoroborates (2) from 1, followed by their thermal decomposition. The procedure is quite simple, involving: (1) constant-current electrolysis of a mixture of 1, Ph3P, and Ph3PH·BF4 in CH2Cl2 in an undivided cell; (2) refluxing a tetrahydrofuran or dioxane solution of the residue afforded by evaporation of the solvent in vacuo after the electrolysis. Cyclic secondary alcohols such as 3β-hydroxy steroids and 2-adamantanol are transformed into the corresponding fluorides in satisfactory yields when the geometry of the leaving group in 2 is suitable for the substitution or an elimination process for 2 to give an alkene is stereochemically forbidden. The fluorination of steroidal alcohols and 4-phenyl-1-cyclohexanol proceeded with complete inversion, demonstrating that a fluorine atom from the tetrafluoroborate anion attacks from the side opposite to the phosphonium moiety in 2 via an SN2 mechanism rather than an SN1 mechanism. The fluorination of acyclic secondary and primary alcohols was performed by the present method in reasonable yields, although the reaction for the latter required more forcing conditions, such as refluxing in dioxane.
- Maeda, Hatsuo,Koide, Takashi,Matsumoto, Sayaka,Ohmori, Hidenobu
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p. 1480 - 1483
(2007/10/03)
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- Stepwise Reduction of Acetals to the Corresponding Hydrocarbons. A Mild and Effective Transformation via Carbinyl Bromides
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Stepwise reduction of two alkoxy groups in acetal was effected by the action of triethylsilane along with acetyl bromide and SnBr2 and then of tributyltinhydride (or lithium aluminium hydride) providing methyl or methylene compounds in good yields under very mild conditions.
- Oriyama, Takeshi,Ichimura, Yuichi,Koga, Gen
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p. 2581 - 2582
(2007/10/02)
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- Reactions of Azo and Azoxy Sulphones with Transition Metal Complexes. Part 7. Arylation of Olefins with Arylazoxy Aryl Sulphones Catalysed by a Palladium(0) Phosphine Complex
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The arylation of acyclic and cyclic olefins by arylazoxy aryl sulphones has been investigated in the presence of a palladium(0) catalyst in benzene.Both of the aryl groups of the arylazoxy aryl sulphones are found to participate in the arylation.Two equivalents of aryl-substituted olefins were obtained when the reactions were carried out at 80 deg C, whereas one equivalent of olefin was arylated at 120 deg C.A plausible catalytic cycle involving a diarylpalladium(II) species is proposed.
- Kamigata, Nobumasa,Fukushima, Takamasa,Satoh, Akira,Kameyama, Masayuki
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p. 549 - 553
(2007/10/02)
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- Regioselective Palladium-Catalyzed Tandem α-Arylation/Isomerization of Cyclic Enamides
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Palladium-catalyzed reactions of aryl iodides with the cyclic enamides 1-(methoxycarbonyl)-1,4,5,6-tetrahydropyridine (1), 1-formyl-1,4,5,6-tetrahydropyridine (2), and 1-formyl-2-pyrroline (3) result in regioselective α-arylation, with concomitant isomerization of the double bond into conjugation with the nitrogen atom.The new enamides 1-(methoxycarbonyl)-2-aryl-1,2,3,4-tetrahydropyridines (4), 1-formyl-2-aryl-1,2,3,4-tetrahydropyridines (5), and 1-formyl-5-phenyl-2-pyrroline (6a) were isolated in various yields.The migration of the double bond is affected (a) by an amino group in the ortho position of the aryl iodide; (b) by the presence of silver salts; and (c) partly by a 4-methyl group in the tetrahydropyridine ring.In these cases the allylic compounds 2-aryl-1,2,5,6-tetrahydropyridines (10a,b and 13) are formed.
- Nilsson, Kristina,Hallberg, Anders
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p. 2464 - 2470
(2007/10/02)
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- Cyclic Olefins by Anodic Oxidation of β-(Trimethylsilyl)carboxylic Acids. - β-(Trimethylsilyl)acrylic Acid Derivatives as Acetylene Equivalents in Diels-Alder Reactions
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Trimethylsilyl-substituted dienophiles 1, 2, and 4 react with dienes 6-14 in 66-100percent yields to give β-trimethylsilyl-substituted carboxylic acids 15-25, some of which are hydrogenated to 26-31.These are decarboxylated-desilylated to cyclic olefins 35-47 by Non-Kolbe electrolysis in 45-91percent yields.The dienophiles 1, 2, and 4 are thus suitable acetylene equivalents for Diels-Alder reactions.
- Hermeling, Dieter,Schaefer, Hans J.
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p. 1151 - 1158
(2007/10/02)
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- Palladium(0)-Catalyzed Arylation of Olefins by Arylamines and an Alkyl Nitrite
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Various olefins were arylated by the combination of arylamines and tert-butyl nitrite under palladium catalysis in the presence of acid such as monochloroacetic or acetic.The reaction proceeded in good yields without serious effects from substituents on either the olefinic substrates or the arylamines, including 3-aminopyridine.
- Kikukawa, Kiyoshi,Maemura, Koji,Kiseki, Yasuyuki,Wada, Fumio,Matsuda, Tsutomu,Giam, Choo S.
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p. 4885 - 4888
(2007/10/02)
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