- Efficient synthesis of 7-, 8- and 9-membered cyclic allyltitanium compounds and their stereoselective addition reaction with aldehydes and imines
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Reaction of 7-, 8- and 9-membered cyclic allylic compounds 2 with (η2propene)Ti(O-i-Pr)2 (1) via an oxidative addition pathway provides the corresponding allylic titanium compounds, which, in turn, react with aldehydes and imines stereoselectively, thus providing an efficient and stereoselective method for synthesizing cycloalkenes having a side chain at the allylic position.
- Hikichi, Shinichi,Gao, Yuan,Sato, Fumie
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Read Online
- Addition of dihalocarbenes to corannulene. A fullerene-type reaction
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Dihalocarbenes (:CCl2, :CBr2, and :CI2) add preferentially to one of the radial double bonds of corannulene, rather than to the rim. These cyclopropanations strongly resemble the additions of dihalocarbenes to fullerenes, which likewise occur at 6:6-double bonds, destroy the cyclic conjugation in two adjacent benzene rings, and give 'closed' adducts. An explanation is offered for the abnormally high reactivity of the interior carbon atoms of corannulene. (C) 2000 Elsevier Science Ltd.
- Preda,Scott
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Read Online
- The Chemistry of 5-Oxodihydroisoxazoles. XIII. Reactions of the Imino Carbene Derived from Photolysis of Ethyl 5-Oxo-2-phenyl-2,5-dihydroisoxazole-4-carboxylate
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Photolysis of ethyl 5-oxo-2-phenyl-2,5-dihydroisoxazole-4-carboxylate at 300 nm in acetonitrile gives a carbene which is captured efficiently by bromide, chloride, acetate and cyanate, and less efficiently by iodide, thiocyanate, cyclohexene and tetrahydr
- Ang, Kiah H.,Prager, Rolf H.,Williams, Craig M.
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Read Online
- Cu-catalyzed asymmetric addition of sp2-hybridized zirconium nucleophiles to racemic allyl bromides
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Alkenylzirconium nucleophiles made in situ by the hydrozirconation of terminal alkynes undergo dynamic kinetic asymmetric allylic alkenylation with racemic allyl bromides to give enantioenriched products.
- Sidera, Mireia,Fletcher, Stephen P.
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Read Online
- Photochemical Organocatalytic Benzylation of Allylic C–H Bonds
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We report a radical-based organocatalytic method for the direct benzylation of allylic C–H bonds. The process uses nonfunctionalized allylic substrates and readily available benzyl radical precursors and is driven by visible light. Crucial was the identification of a dithiophosphoric acid that performs two distinct catalytic roles, sequentially acting as a catalytic donor for the formation of photoactive electron donor–acceptor (EDA) complexes and then as a hydrogen atom abstractor. By mastering these orthogonal radical generation paths, the organic catalyst enables the formation of benzylic and allylic radicals, respectively, to then govern their selective coupling. The protocol was also used to design a three-component radical process, which increased the synthetic potential of the chemistry.
- Le Saux, Emilien,Melchiorre, Paolo,Zanini, Margherita
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supporting information
p. 1113 - 1118
(2022/02/05)
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- Cu-Catalyzed Oxidative Allylic C-H Arylation of Inexpensive Alkenes with (Hetero)Aryl Boronic Acids
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Herein, we present a regioselective Cu-catalyzed oxidative allylic C(sp3)-H arylation by radical relay using a broad range of heteroaryl boronic acids with inexpensive and readily available unactivated terminal and internal olefins. This C(sp2)-C(sp3) allyl coupling has the advantage of using cheap, abundant, and nontoxic Cu2O without the need to use prefunctionalized alkenes, thus offering an alternative method to allylic arylation reactions that employ more traditional coupling partners with preinstalled leaving groups (LGs) at the allylic position.
- Pal, Suman,Cotard, Marine,Gérardin, Baptiste,Hoarau, Christophe,Schneider, Cédric
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supporting information
p. 3130 - 3135
(2021/05/05)
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- Direct cross-coupling between alkenes and tetrahydrofuran with a platinum-loaded titanium oxide photocatalyst
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A Pt-loaded TiO2 photocatalyst successfully catalyzed the direct cross-coupling between various alkenes and tetrahydrofuran (THF) without any additional oxidizing agent. The reaction between cyclohexene and THF gave three cross-coupling products, namely, 2-cyclohexyltetrahydrofuran (A), 2-(cyclohex-2-en-1-yl)tetrahydrofuran (B) and 2-(cyclohex-1-en-1-yl)tetrahydrofuran (C), along with gaseous hydrogen. The mechanistic study revealed that these products were formed through different individual mechanisms: successive addition of two radical species, a 2-tetrahydrofuranyl radical and a hydrogen radical, to the double bond of cyclohexene for A, coupling of a 3-cyclohexenyl radical and a 2-tetrahydrofuranyl radical for B, and 2-tetrahydrofuranyl radical addition and hydrogen radical elimination at the double bond of cyclohexene for C. Among these three mechanisms, those for B and C are dehydrogenative. In this photocatalytic reaction system, since the cyclohexene molecule has enough reactivity, due to the localized π electron density, the Pt nanoparticles loaded on the TiO2 function not as a metal catalyst but as an electron receiver to enhance the charge separation, although the dehydrogenative cross-coupling of benzene with THF requires Pd metal catalysis.
- Tyagi, Akanksha,Yamamoto, Akira,Yamamoto, Muneaki,Yoshida, Tomoko,Yoshida, Hisao
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p. 2546 - 2556
(2018/06/01)
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- Metal-organic framework composites with luminescent pincer platinum(II) complexes: 3MMLCT emission and photoinduced dehydrogenation catalysis
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Pincer platinum(ii) complexes are well documented to exhibit weak intermolecular interactions in the solid state and 77 K glassy solutions, leading to emissive triplet metal-metal-to-ligand charge transfer (3MMLCT) excited states that often vanish in dilute solutions. In this work, metal-organic framework (MOF) materials are introduced to provide a "solid solution" environment for easy access to 3MMLCT excited states of pincer platinum(ii) complexes. Phosphorescent composites PtII@MOFs (1-4) with matrix-dependent monomers and oligomer emission properties were obtained. These PtII@MOFs are efficient catalysts for photoinduced dehydrogenation reactions.
- Sun, Chun-Yi,To, Wai-Pong,Hung, Faan-Fung,Wang, Xin-Long,Su, Zhong-Min,Che, Chi-Ming
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p. 2357 - 2364
(2018/03/05)
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- Cobalt-catalyzed oxidative esterification of allylic/benzylic C(sp3)–H bonds
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A protocol for the cobalt-catalyzed oxidative esterification of allylic/benzylic C(sp3)–H bonds with carboxylic acids was developed in this work. Mechanistic studies revealed that C(sp3)–H bond activation in the hydrocarbon was the turnover-limiting step and the in-situ formed [Co(III)]Ot-Bu did not engage in hydrogen atom abstraction (HAA) of a C–H bond. This protocol was successfully incorporated into a synthetic pathway to β-damascenone that avoided the use of NBS.
- Ren, Tian-Lu,Xu, Bao-Hua,Mahmood, Sajid,Sun, Ming-Xue,Zhang, Suo-Jiang
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supporting information
p. 2943 - 2948
(2017/04/26)
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- Oxidation of aliphatic and aromatic C[sbnd]H bonds by t-BuOOH catalyzed by μ-nitrido diiron phthalocyanine
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Low temperature selective transformation of alkanes to useful products continues to be an important challenge in chemistry and industry. μ-Nitrido diiron phthalocyanines in combination with H2O2 have been recently identified as powerful oxidation catalysts for these challenging reactions due to the formation of ultra-high valent diiron oxo species PcFe(IV)μNFe(IV)[dbnd]O(Pc+[rad]). This very strong two-electron oxidizing species is generated from peroxo complex PcFe(IV)μNFe(III)[sbnd]O[sbnd]O[sbnd]R(Pc) (R[dbnd]H in the case of H2O2) via heterolytic O[sbnd]O bond cleavage. Therein we show that the evolution of the peroxo diiron complex depends on the peroxide structure. Using tBuOOH we have demonstrated the formation of an one-electron oxidizing PcFe(IV)μNFe(IV)[dbnd]O(Pc) and tBuO[rad] radical via homolytic O[sbnd]O cleavage of the peroxocomplex. The reactivity of the μ-nitrido diiron tetra-t-butylphthalocyanine ? tBuOOH catalytic system was investigated in the oxidation of different C[sbnd]H bonds in alkanes, olefins, aromatic and alkylaromatic compounds. The main products of cyclohexane oxidation were cyclohexanone and cyclohexanol whereas bicyclohexyl was formed in minor amounts even in the presence of O2 and tBuOOH. Under optimal conditions, the turnover numbers of almost 5300 have been achieved.
- Kudrik, Evgeny V.,Sorokin, Alexander B.
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p. 499 - 505
(2016/12/16)
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- Deciphering Photoluminescence Dynamics and Reactivity of the Luminescent Metal-Metal-Bonded Excited State of a Binuclear Gold(I) Phosphine Complex Containing Open Coordination Sites
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Luminescent metal complexes having open coordination sites hold promise in the design of sensory materials and photocatalysts. As a prototype example, [Au2(dcpm)2)]2+ (dcpm = bis(dicyclohexylphosphanyl) is known for its intriguing environmental sensitive photoluminescence. By integrating a range of complementary ultrafast time-resolved spectroscopy to interrogate the excited state dynamics, this study uncovers that the events occurring in extremely rapid timescales and which are modulated strongly by environmental conditions play a pivotal role in the luminescence behavior and photochemical outcomes. Formed independent of the phase and solvent property within 0.15 ps, the metal-metal bonded 35dσ6pσ state is highly reactive possessing strong propensity toward increasing coordination number at AuI center, and with 510 ps lifetime in dichloromethane is able to mediate light induced C-X bond cleavage.
- Ma, Chensheng,Chan, Chris Tsz-Leung,To, Wai-Pong,Kwok, Wai-Ming,Che, Chi-Ming
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supporting information
p. 13888 - 13893
(2015/09/28)
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- Iron-catalyzed allylic arylation of olefins via C(sp3)-H activation under mild conditions
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An aryl Grignard reagent in the presence of mesityl iodide converts an allylic C-H bond of a cycloalkene or an allylbenzene derivative into a C-C bond in the presence of a catalytic amount of Fe(acac)3 and a diphosphine ligand at 0 C. The stereo- and regioselectivity of the reaction, together with deuterium labeling experiments, suggest that C-H bond activation is the slow step in the catalytic cycle preceding the formation of an allyliron intermediate.
- Sekine, Masaki,Ilies, Laurean,Nakamura, Eiichi
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supporting information
p. 714 - 717
(2013/04/10)
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- Novel reactivity of N-bridged diiron phthalocyanine in the activation of C-H bonds: Hydroacylation of olefins as an example of the efficient formation of C-C bonds
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Bridge over troubled iron: An N-bridged diiron tetra-tert- butylphthalocyanine complex, usually employed for oxidation reactions, also catalyzes the addition of acetaldehyde to olefins (see scheme) to provide methylketones with a high selectivity (up to 92%) and high turnover numbers (3600-5700). Copyright
- Alvarez, Leonardo X.,Kudrik, Evgeny V.,Sorokin, Alexander B.
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supporting information; experimental part
p. 9298 - 9301
(2011/10/09)
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- PROCESS FOR PRODUCTION OF CYCLIC OLEFINS
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Disclosed is a method for producing a cyclic olefin compound having two or more cyclohexene rings per molecule via intramolecular dehydration of an alicyclic alcohol having two or more hydroxylated cyclohexane rings per molecule. The method includes the step (i) of heating the alicyclic alcohol at a temperature of 130°C to 230°C and a pressure greater than 20 Torr in an organic solvent in the presence of a dehydration catalyst, to carry out dehydration of the alicyclic alcohol while distilling off by-product water, which dehydration catalyst is liquid or soluble in a liquid reaction mixture under the reaction conditions; and the subsequent step (ii) of heating the resulting reaction mixture at a temperature of 50°C to 220°C and a pressure of 200 Torr or less to recover the cyclic olefin compound as a distillate. According to the method, side reactions such as isomerization are suppressed, and high-purity cyclic olefin compounds with less impurities can be simply and efficiently obtained in high yields.
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Page/Page column 18-19
(2009/01/24)
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- Lanthanum metal-assisted deoxygenative coupling of alcohols
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It was found that the deoxygenative coupling of alcohols efficiently proceeded by treatment with lanthanum metal and chlorotrimethylsilane in the presence of a catalytic amount of iodine. This coupling reaction was accelerated by the addition of a catalytic amount of copper(I) iodide.
- Nishino, Toshiki,Nishiyama, Yutaka,Sonoda, Noboru
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p. 3689 - 3691
(2007/10/03)
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- Palladium( 0) -catalyzed phenoxycarbonylation of allylic carbonates
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Phenoxycarbonylation of various allylic carbonates under various conditions in tetrahydrofuran is described. The nature and ratio of the products formed are dependent on the presence of water, carbon monoxide pressure and addition of various inorganic halides. The formation of a product arising from dimerization of the allylic carbonate is discussed.
- Goux, Catherine,Lhoste, Paul,Sinou, Denis,Masdeu, Anna
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p. 139 - 143
(2007/10/03)
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- Nitrosonium Ion Promoted Iodination and 1,2-Iodofunctionalization of Cyclohexene
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The promoting influence of NO+BF4- on the addition of I2 or 'I+Nu-' couples to cyclohexene (1) in the presence of O2 is described. 1-Acetoxy-2-iodocyclohexane is obtained in 89percent isolated yield from the reaction of I2, 1 and CH3COOH in CH2Cl2, and the corresponding methoxy- and acetamido-substituted iodocyclohexanes are obtained in 96 and 92percent yield, when methanol and acetonitrile, respectively, are added.Applications of the method to the synthesis of cis-1,2-cyclohexanediol (Woodward reaction) and bis(2-iodocyclohexyl) ether is described.
- Radner, Finn
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p. 902 - 907
(2007/10/02)
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- ROLE OF THE ACETYLACETONYL RADICAL IN THE SENSITIZED PHOTOPRODUCTION OF BIS(ACETONYLACTONATO)COPPER(II)
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Benzophenone-sensitized photoproduction of Cu(acac)2 generated the acetylacetonyl radical (acac.) which could be trapped as acetylacetone by hydrogen as well as by a H-atom-donating agent, or as the corresponding nitroxide with 2-nitroso-2-methylpropane,
- Cow, Yuan L.,Buono,-Core, Gonzalo E.
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p. 1234 - 1239
(2007/10/02)
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- Photochemical Hydroxymethylation of Alicyclic and Aliphatic Alkenes Induced by a EuIII/EuII Photoredox System in Methanol
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The photoirradiation of a methanol solution of EuCl3 and alkenes such as cyclohexene, cyclooctene, cyclododecene, and tetramethylene afforded (hydroxymethyl)alkane.The dihydro dimer of alkene,hydrogen, and ethylene glycol are also formed.Reactions proceed via a radical mechanism induced by hydrogen atoms and hydroxymethyl radicals, which are produced by a photoredoc reaction of EuIII/EuII in methanol.
- Ishida, Akito,Yamashita, Shinya,Toki, Susumu,Takamuku, Setsuo
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p. 1195 - 1200
(2007/10/02)
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- LIGHT-MEDIATED TRANSFORMATIONS OF OLEFINS INTO ALCOHOLS: REACTIONS OF HYDROXYL RADICALS WITH CYCLOALKENES
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Reactions of hydroxyl radicals, generated by photodecomposition of hydrogen peroxide in acetonitrile, with a wide variety of cycloalkenes have been examined.The results show that the major reaction is the addition of hydroxyl radicals to the less substituted end of the double bond, furnishing the secondary alcohols.The reactivity pattern and the observed regio- and stereoselectivity clearly reveal that the steric parameters associated with the substrates play a dominant role in directing the addition reactions.More importantly, this study led to the development of a new methodology for the facile conversions of olefins essentially into secondary alcohols, and includes a few examples which demonstrate the potential of the method.
- Sonawane, H. R.,Nanjundiah, B. S.,Kelkar, R. G.
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p. 6673 - 6682
(2007/10/02)
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- (Phosphine)carbonylnitrosylacylcobaltate Complexes as Acyl Transfer Reagents. Acylation of Allylic Halides, Conjugated Enones, and Quinones
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The complex Co(NO)(CO)2(PPh3) is an air stable, easily handled crystalline solid, prepared from Co2(CO)8, sodium nitrite, and triphenylphosphine without isolation of the volatile intermediate Co(NO)(CO)3.Treatment of this complex with organolithium reagents at -40 deg C generated unstable acylate complexes - which readily transferred the acyl group to allylic halides to produce β,γ-unsaturated ketones, to conjugated ketones to produce 1,4-dicarbonyl compounds, and to quinones to form 4-acylcyclohexadienones.
- Hegedus, Louis S.,Perry, Robert J.
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p. 4955 - 4960
(2007/10/02)
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- Stereochemical Aspects of Aldehyde Additions to Cyclohex-2-enylstannanes
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Cyclohex-2-enylation of aldehydes, mediated with boron trifluoride etherate, involves γ-equatorial approach of the presumed aldehyde-Lewis acid adduct (RCHO-BF3), irrespective of starting stannane stereochemistry.Marginal threo selectivity characterizes homoallyl alcohol formation from benzaldehyde, whereas alkanals react with high erythro selectivity, so that 1-(1'-hydroxyalkyl)cyclohex-2-enes in this diastereomeric form are available based on allyltin chemistry.
- Young, David,Kitching, William
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p. 1767 - 1777
(2007/10/02)
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- The use of insoluble benzoylated polystyrene beads (polymeric benzophenone) in photochemical reactions
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Friedel-Crafts benzoylation of 2percent-divinylbenzene (DVB) cross-linked polystyrene beads yielded insoluble polymeric analogs of benzophenone which were used as sensitizers in the photocycloaddition of cyclohexene to maleic anhydride and in the E-Z isomerization of (E)-1,3-pentadiene and methyl (E)-2,2-dimethyl-3,5-hexadienoate.In the first reaction, the use of polymer-anchored sensitizers resulted in the separation of polymer-attached by-product by simple filtration, although the yield of photoadducts was less than three quarters of that obtained when using benzophenone itself, and the recovered polymers could not be reused.In the photoisomerizations, the compositions of the photostationary states reached when using the polymeric sensitizers (now reusable) were shown to depend on the degree of functionalization of the polymers via steric hindrance to the energy transfer process.Intrapolymerically sensitized E-Z photoisomerization was also demonstrated on a polymer containing benzophenone and diene units.Photooxidation of secondary alcohols (isopropanol, cyclohexanol) to ketones and photooxygenation of 2,3-dimethyl-2-butene to 2,3-dimethyl-3-buten-2-yl hydroperoxide (in the presence of oxygen) were other reactions for which polymeric benzophenones could be used.
- Bourdelande, Jose Luis,Font, Josep,Sanchez-Ferrando, Francisco
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p. 1007 - 1016
(2007/10/02)
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- Electron-transfer Processes: Metal Salt Catalysed Oxidation of Olefins by Peroxydisulphate
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The reaction of simple olefins (oct-1-ene, oct-2-ene, cyclohexene, cycloheptene) with peroxydisulphate has been investigated under several conditions: (i) in aqueous medium and catalysis by AgI, FeII, and CuII; (ii) in acetic madium and catalysis by CuII, FeIII; (iii) in the presence of traps of nucleophilic alkyl radicals (protonated heteroaromatic bases and 1,4-benzoquinone either in water or in acetic acid).The catalyst and the radical trap govern the selectivity and allow a variety of new synthetic achievements.Evidence for a unified initial mechanism of electron transfer with formation of a radical cation from the olefin is reported to explain all the results.In water the radical cation gives a β-hydroxyalkyl radical, which, depending on the nature of the catalyst and the trap, can give the corresponding saturated alcohol by hydrogen abstraction, the products of CuII oxidation, or β-hydroxyalkylation of the heteroaromatic compound or 1,4-benzoquinone.In acetic acid the radical cation gives a β-acetoxyalkyl radical, which is oxidized to the corresponding allylic acetate by copper(II) acetate or trapped by the heteroaromatic base.
- Arnoldi, Claudio,Citterio, Attilio,Minisci, Francesco
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p. 531 - 542
(2007/10/02)
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- ALLYLSILANES FROM ALLYLCHLORIDES AND SILYLCUPRATES
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The beneficial effects of copper (I) salts on the reactions of cyclohex-2-enyl chlorides and 3,4-epoxycyclohexene with phenyldimethylsilyllithium are reported.
- Laycock, Bronwyn,Kitching, William,Wickham, Geoffrey
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p. 5785 - 5788
(2007/10/02)
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- PHOTOCYCLOADDITION OF CYCLOHEXENE AND MALEIC ANHYDRIDE SENSITIZED BY INSOLUBLE BENZOYLATED POLYSTYRENE
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Friedel-Crafts benzoylation of styrene - 2percent DVB copolymer beads yielded insoluble benzoylated polystyrene which was successfully used as sensitizer in the photocycloaddition of cyclohexene with maleic anhydride.
- Bourdelande, J. L.,Font, J.,Sanchez-Ferrando, F.
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p. 3805 - 3808
(2007/10/02)
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- Heterocyclic Polyfluoro-compounds. Part 32. Photochemical Reactions of 3-Chlorotetrafluoro- and 3,5-Dichlorotrifluoro-pyridines with Olefins, and their Photoreduction
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Ethylene reacts photochemically with 3-chlorotetrafluoropyridine to yield 3-(2-chloroethyl)tetrafluoropyridine, and cyclo-pentene and -hexene yield the corresponding 3-cycloalkyltetrafluoropyridines.Photochemical reaction of cyclohexene with 3,5-dichlorotrifluoropyridine yields 3-chloro-5-cyclohexyltrifluoropyridine.The chlorine in 3-chlorotetrafluoropyridine, and one of the chlorines in 3,5-dichlorotrifluoropyridine, is readily reduced photochemically in solvents such as ethanol, diethyl ether, or acetone.
- Barlow, Michael G.,Haszeldine, Robert N.,Langridge, John R.
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p. 2520 - 2522
(2007/10/02)
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- Preparation of 1,5-Dienes by Photolysis of η3-Allylpalladium Complexes
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1,5-Dienes are formed in good yields when dilute solutions of η3-allylpalladium complexes in acetonitrile are irradiated at 366 nm.
- Muzart, Jacques,Pete, Jean-Pierre
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p. 257 - 258
(2007/10/02)
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- Photochemistry of Cycloalkenes. 9. Photodimerization of Cyclohexene
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The photodimerization of cyclohexene has been restudied.Either direct or triplet-sensitized irradiation produced a stereoisomeric mixture of dimers 6-8, respectively, as primary products with the cis,trans isomer 7 predominating.The direct-irradiation process was complicated by the accompanying formation of the radical-derived products 3-5.Dimerization is interpreted in terms of initial light-induced cis-trans isomerization of cyclohexene, followed by a nonstereospecific ground-states + 2a>addition of trans-cyclohexene to the cis isomer.By contrast, cycloheptene showed little tendency to undergo photodimerization; attempted p-xylene-sensitized dimerization afforded instead principally the sensitizer-olefin adducts 10 and 11.Comparison is made with the copper(I) triflate catalyzed photodimerization of cyclohexene and cycloheptene.
- Kropp, Paul J.,Snyder, John J.,Rawlings, Peter C.,Fravel, Harold G.
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p. 4471 - 4474
(2007/10/02)
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