- Deciphering Reactivity and Selectivity Patterns in Aliphatic C-H Bond Oxygenation of Cyclopentane and Cyclohexane Derivatives
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A kinetic, product, and computational study on the reactions of the cumyloxyl radical with monosubstituted cyclopentanes and cyclohexanes has been carried out. HAT rates, site-selectivities for C-H bond oxidation, and DFT computations provide quantitative information and theoretical models to explain the observed patterns. Cyclopentanes functionalize predominantly at C-1, and tertiary C-H bond activation barriers decrease on going from methyl- and tert-butylcyclopentane to phenylcyclopentane, in line with the computed C-H BDEs. With cyclohexanes, the relative importance of HAT from C-1 decreases on going from methyl- and phenylcyclohexane to ethyl-, isopropyl-, and tert-butylcyclohexane. Deactivation is also observed at C-2 with site-selectivity that progressively shifts to C-3 and C-4 with increasing substituent steric bulk. The site-selectivities observed in the corresponding oxidations promoted by ethyl(trifluoromethyl)dioxirane support this mechanistic picture. Comparison of these results with those obtained previously for C-H bond azidation and functionalizations promoted by the PINO radical of phenyl and tert-butylcyclohexane, together with new calculations, provides a mechanistic framework for understanding C-H bond functionalization of cycloalkanes. The nature of the HAT reagent, C-H bond strengths, and torsional effects are important determinants of site-selectivity, with the latter effects that play a major role in the reactions of oxygen-centered HAT reagents with monosubstituted cyclohexanes.
- Martin, Teo,Galeotti, Marco,Salamone, Michela,Liu, Fengjiao,Yu, Yanmin,Duan, Meng,Houk,Bietti, Massimo
-
supporting information
p. 9925 - 9937
(2021/06/30)
-
- ETHERS AND ESTERS OF 1-SUBSTITUTED CYCLOALKANOLS FOR USE AS AROMA CHEMICALS
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The present invention relates to the use of an ether or an ester of a 1 -substituted cycloalkanol or of mixtures of two or more ethers or esters of 1 -substituted cycloalkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof as aroma chemicals; to the use thereof for modifying the scent character of a fragranced composition; to an aroma chemical composition containing an ether or an ester of a 1 -substituted cycloalkanol or of mixtures of two or more ethers or esters of 1 -substituted cycloalkanols or of a stereoisomer thereof or of a mixture of two or more stereoisomers thereof; and to a method of preparing a fragranced composition or for modifying the scent character of a fragranced composition. The invention further relates to specific ethers or esters of 1 -substituted cycloalkanols.
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- Palladium-Catalyzed C(sp3)?H Arylation of Primary Amines Using a Catalytic Alkyl Acetal to Form a Transient Directing Group
-
C?H Functionalization of amines is a prominent challenge due to the strong complexation of amines to transition metal catalysts, and therefore typically requires derivatization at nitrogen with a directing group. Transient directing groups (TDGs) permit C?H functionalization in a single operation, without needing these additional steps for directing group installation and removal. Here we report a palladium catalyzed γ-C?H arylation of amines using catalytic amounts of alkyl acetals as transient activators (e.g. commercially available (2,2-dimethoxyethoxy)benzene). This simple additive enables arylation of amines with a wide range of aryl iodides. Key structural features of the novel TDG are examined, demonstrating an important role for the masked carbonyl and ether functionalities. Detailed kinetic (RPKA) and mechanistic investigations determine the order in all reagents, and identify cyclopalladation as the turnover limiting step. Finally, the discovery of an unprecedented off-cycle free-amine directed ?-cyclopalladation of the arylation product is reported.
- St John-Campbell, Sahra,Ou, Alex K.,Bull, James A.
-
supporting information
p. 17838 - 17843
(2018/11/23)
-
- Inexpensive and rapid hydrogenation catalyst from CuSO4/CoCl2 — Chemoselective reduction of alkenes and alkynes in the presence of benzyl protecting groups
-
The simple reduction of a number of alkenes and alkynes was performed with a typical reaction time of 20 min using a copper-cobalt catalytic system. The reduction did not cleave benzyl protecting groups which are usually vulnerable to catalytic hydrogenation reactions. The catalyst can be prepared in situ by reduction of the inexpensive precursor salts CuSO4 and CoCl2 with NaBH4. Sodium borohydride was also used as an easily handled hydrogen source for the catalytic reductions. No pressure, heating or inert atmosphere is required and purification/catalyst removal is achieved using extraction procedures, making this approach simple and efficient.
- Ficker, Mario,Svenningsen, S?ren W.,Larribeau, Thomas,Christensen, J?rn B.
-
supporting information
p. 1125 - 1129
(2018/02/21)
-
- Colloid and nanosized catalysts in organic synthesis: XI. Hydrogenation of alkynes catalyzed by nickel nanoparticles
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The reaction of alkynes with hydrogen under atmospheric pressure in the presence of nickel nanoparticles as a catalyst led to the exhaustive hydrogenation of the triple bond.
- Popov, Yu. V.,Mokhov,Nebykov
-
-
- Application of Pd Nanoparticles Supported on Mesoporous Hollow Silica Nanospheres for the Efficient and Selective Semihydrogenation of Alkynes
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Herein, the preparation of a heterogeneous catalyst consisting of 1-2 nm sized Pd nanoparticles supported on amino-functionalized mesoporous hollow silica nanospheres and its use for the semihydrogenation of mono- And disubstituted alkynes is reported. By utilizing this Pd nanocatalyst together with the green poisoning agent DMSO, high yields of the desired alkenes could be achieved, while suppressing the degree of over-reduction to alkanes. To our delight, the Pd nanocatalyst displayed remarkable chemoselectivity towards the alkyne moiety, allowing the transformation to be carried out in the presence of other reducible functionalities, such as halogens, carbonyl, and nitro groups.
- Verho, Oscar,Zheng, Haoquan,Gustafson, Karl P. J.,Nagendiran, Anuja,Zou, Xiaodong,B?ckvall, Jan-E.
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p. 773 - 778
(2016/03/05)
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- One-pot room-temperature conversion of cyclohexane to adipic acid by ozone and UV light
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Nitric acid oxidation of cyclohexane accounts for ~95% of the worldwide adipic acid production and is also responsible for ~5 to 8% of the annual worldwide anthropogenic emission of the ozone-depleting greenhouse gas nitrous oxide (N2O). Here we report a N2O-free process for adipic acid synthesis.Treatment of neat cyclohexane, cyclohexanol, or cyclohexanone with ozone at room temperature and 1 atmosphere of pressure affords adipic acid as a solid precipitate. Addition of acidic water or exposure to ultraviolet (UV) light irradiation (or a combination of both) dramatically enhances the oxidative conversion of cyclohexane to adipic acid.
- Hwang, Kuo Chu,Sagadevan, Arunachalam
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p. 1495 - 1498
(2015/02/19)
-
- Selective activation of secondary C-H bonds by an iron catalyst: Insights into possibilities created by the use of a carboxyl-containing bipyridine ligand
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In this work, we report the discovery of a carboxyl-containing iron catalyst 1 (FeII-DCBPY, DCBPY = 2,2′-bipyridine-4,4′- dicarboxylic acid), which could activate the C-H bonds of cycloalkanes with high secondary (2°) C-H bond selectivity. A turnover number (TN) of 11.8 and a 30% yield (based on the H2O2 oxidant) were achieved during the catalytic oxidation of cyclohexane by 1 under irradiation with visible light. For the transformation of cycloalkanes and bicyclic decalins with both 2° and tertiary (3°) C-H bonds, 1 always preferred to oxidise the 2° C-H bonds to the corresponding ketone and alcohol products; the 2°/3° ratio ranged between 78/22 and >99/1 across 7 examples. 18O isotope labelling experiments, ESR experiments, a PPh3 method and the catalase method were used to characterize the reaction process during the oxidation. The success of 1 showed that, in addition to using a bulky catalyst, high 2° C-H bond selectivity could also be achieved using a less bulky molecular iron complex as the catalyst.
- Cheng, Shi,Li, Jing,Yu, Xiaoxiao,Chen, Chuncheng,Ji, Hongwei,Ma, Wanhong,Zhao, Jincai
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p. 3267 - 3273
(2013/10/01)
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- Highly selective hydrogenation of multiple carbon-carbon bonds promoted by nickel(0) nanoparticles
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A new method for the highly stereoselective cis semihydrogenation of internal alkynes, semihydrogenation of terminal alkynes, reduction of dienes to alkenes, and reduction of alkynes and alkenes to alkanes is described based on in situ generated both Ni(0) nanoparticles and molecular hydrogen.
- Alonso, Francisco,Osante, I?aki,Yus, Miguel
-
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- Photolysis of 1-alkylcycloalkanols in the presence of (diacetoxyiodo) benzene and I2. Intramolecular selectivity in the β-scission reactions of the intermediate 1-alkylcycloalkoxyl radicals
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The C-C β-scission reactions of 1-alkylcycloalkoxyl radicals, generated photochemically by visible light irradiation of CH2Cl 2 solutions containing the parent 1-alkylcycloalkanols, (diacetoxy)-iodobenzene (DIB), and I2, have been investigated through the analysis of the reaction products. The 1-alkylcycloalkoxyl radicals undergo competition between ring opening and C-alkyl bond cleavage as a function of ring size and of the nature of the alkyl substituent. With the 1-propylcycloheptoxyl, 1-propylcyclooctoxyl, and 1-phenylcyclooctoxyl radicals, formation of products deriving from an intramolecular 1,5-hydrogen atom abstraction reaction from the cycloalkane ring has also been observed. The results are discussed in terms of release of ring strain associated to ring opening, stability of the alkyl radical formed by C-alkyl cleavage, and with cycloheptoxyl and cyclooctoxyl radicals, also in terms of the possibility of achieving a favorable geometry for intramolecular hydrogen atom abstraction.
- Antunes, Carla S. Aureliano,Bietti, Massimo,Lanzalunga, Osvaldo,Salamone, Michela
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p. 5281 - 5289
(2007/10/03)
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- Development of a continuous-flow system for catalysis with palladium(0) particles
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Heterogeneous catalysis for organic synthesis under continuous-flow conditions becomes possible by a new reactor-based approach. Continuous-flow reactors with a monolithic glass/polymer composite interior are loaded with palladium particles by ion exchange followed by reduction. When incorporated into a continuous-flow setup (PASSflow) this reactor allows the transfer-hydrogenation of alkenes, alkynes, nitro-substituted aromatic compounds and benzyl ethers in the flow-through mode. In addition, the activity of the catalysts is well suited to achieve Suzuki, Sonogashira and Heck cross-coupling reactions in the absence of phosphanes or any other ligands, resulting in a greatly simplified purification. As an extension to this concept a bifunctional support was prepared inside the reactor consisting of Pd particles and an ion-exchange group (hydroxide form). In the Suzuki-Miyaura reaction the reactor serves as a base for immobilisation and activation of the boronic acid as boronate and as a catalyst for promoting the C-C coupling reaction under continuous-flow conditions. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Solodenko, Wladimir,Wen, Hongliang,Leue, Stefanie,Stuhlmann, Friedrich,Sourkouni-Argirusi, Georgia,Jas, Gerhard,Schoenfeld, Hagen,Kunz, Ulrich,Kirschning, Andreas
-
p. 3601 - 3610
(2007/10/03)
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- Tandem cross-metathesis/hydrogenation/cyclization reactions by using compatible catalysts
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(Matrix presented) A one-pot tandem cross-metathesis/hydrogenation/cyclization procedure was achieved at room temperature, under 1 atm of hydrogen, in the presence of a ruthenium catalyst and PtO2 showing the compatibility of the two catalysts. This tandem reaction allows the synthesis of substituted lactones and lactols from acrylic acid and acrolein, respectively, in the presence of unsaturated alcohols.
- Cossy, Janine,Bargiggia, Frederic,BouzBouz, Samir
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p. 459 - 462
(2007/10/03)
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- Process for preparing acrylate compound
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An acrylate compound of formula (4): 1is produced by allowing an acrylic acid compound of formula (1): 2to react with an unsaturated compound of formula (2) or (3): 3In formulae (1) through (4), R1 and R2 are H or F, R3 is H, F, or an alkyl, alkenyl, fluoroalkyl or fluoroalkenyl group, R4 and R5 are H, halogen, or an alkyl, alkenyl, halogenated alkyl or halogenated alkenyl group; and X and Y are an unsubstituted or substituted hydrocarbon group, and dashed line - - - - - means that X and Y may be bonded together to form a cyclic structure.
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-
-
- Method for producing carboxylic acid tertiary alkyl ester
-
A carboxylic acid tertiary alkyl ester (Chemical formula 1) of high purity is obtained at a high yield ratio, by continually adding an esterification agent possessing a monovalent acid group, which agent is ester-interchangeable with a tertiary alcohol, to a mixed fluid of a carboxylic acid and a tertiary alcohol: R1(COOR2)n??(1)
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- Selective liquid-phase semihydrogenation of functionalized acetylenes and propargylic alcohols with silica-supported bimetallic palladium-copper catalysts
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Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated. Silica-supported, bimetallic palladium-copper catalysts were prepared in solution under mild conditions by reacting lithium di(4-tolyl)cuprate with palladium acetate in the presence of silica particles. Small bimetallic palladium-copper particles were deposited on the silica surface as confirmed with TEM-EDAX and EXAFS. The new material has been applied as catalyst in the liquid-phase semihydrogenation of mono- and disubstituted alkynes and showed high selectivity toward the cis-alkenes. The influence of addition of quinoline or potassium hydroxide to the semihydrogenation reaction mixture and the effects of exposure of the catalyst to air before use have been investigated.
- Spee,Boersma,Meijer,Slagt,Van Koten,Geus
-
p. 1647 - 1656
(2007/10/03)
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- Electrochemical alkyl transfer reactions of trialkylborane to carbonyl compounds by use of copper sacrificial anode
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Alkyl groups in trialkylboranes were successfully transferred to carbonyl compounds in the presence of the platinum cathode and copper anode by electrochemical method. The new, mild electrochemical alkyl transfer reaction produced various substituted alcohols in good yields.
- Choi, Jung Hoon,Youm, Jong Sung,Cho, Cheon-Gyu,Czae, Myung-Zoon,Hwang, Book Kee,Kim, Jung Sung
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p. 4835 - 4838
(2007/10/03)
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- Hydrogenation of alkynes with hydrated nickel chloride, lithium and a catalytic amount of naphthalene
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The reaction of alkynes with a mixture of nickel (II) chloride dihydrate, an excess of lithium powder and a catalytic amount of naphthalene (8 mol%) in THF at room temperature, leads to the formation of the corresponding alkanes. The incorporation of deuterium oxide into the nickel salt complex yields deuterated hydrocarbons. The process can be applied to functionalised alkynes as well as to transform alkynes into alkenes depending on the amount of the nickel salt and/or reaction times.
- Alonso, Francisco,Yus, Miguel
-
p. 149 - 152
(2007/10/03)
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- Arene-catalysed lithiation of triflates and triflamides under Barbier-type conditions: An indirect transformation of alcohols and amines into organolithium compounds
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The reaction of alkyl triflates 1 or benzyl triflamides 3 with an excess of lithium powder and a catalytic amount of naphthalene (4 mol%) in the presence of different electrophiles [Me3SiCl, Pr(i)CHO, Bu(t)CHO, PhCHO, 4-MeOC6H4-CHO, CH3(CH2)6CHO, Et2CO, (CH2)5CO, (c-C3H5)2CO, PhCOMe, 4-MeC6H4COPh, PhCh=NPh, n-C8H7CON(CH2)4] in THF at temperature ranging between -78 and 0°C leads, after hydrolysis with water, to the corresponding condensation products 2. When α,β-unsaturated carbonyl compounds are used as electrophilic compounds 1,2- (3-cyclohexenone) or 1,4-addition (cinnamaldehyde or benzylideneacetone) takes place depending on the electrophile used.
- Alonso, Emma,Ramon, Diego J.,Yus, Miguel
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p. 14341 - 14348
(2007/10/03)
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- Alkylation-annulation of halo esters with organometallic reagent/SmI2 couple leading to cycloalkanols: A facile cyclopropanol synthesis from a 3-halo ester
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Transformation of a 3-halo ester to cyclopropanols has been accomplished in excellent yields under mild conditions employing a coupled reagent of samarium(II) diiodide with organometallic reagents. 5- and 6-Halo esters were also transformed into cyclopentanols and cyclohexanols, respectively, in low to moderate yields. The reaction with a 4-halo ester gave 2,2-disubstituted tetrahydrofuran as a major product that resulted from double alkylation followed by cyclization; a substituted cyclobutanol was formed in poor yield.
- Fukuzawa, Shin-Ichi,Furuya, Hideki,Tsuchimoto, Teruhisa
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p. 1953 - 1960
(2007/10/03)
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- Arene-catalysed reductive desulfonylation and desulfinylation reactions: New routes for alkyllithiums
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The reactions of alkyl phenyl sulfones (1) with an excess of lithium powder and a catalytic amount of naphthalene (8 mol %) in the presence of a carbonyl compound or chlorotrimethylsilane (Barbier-type conditions) in THF at temperatures ranging between -78 and 20°C leads, after hydrolysis, to the expected products (2) arising from the corresponding alkyllithium generated in situ. When the same methodology is applied to sulfolene (3) or different alkyl phenyl sulfoxides (6), cyclic sulfinates 5 or products 2 are, respectively, obtained, the yields being, in general modest.
- Alonso, Emma,Guijarro, David,Yus, Miguel
-
p. 2699 - 2708
(2007/10/02)
-
- Selective generation of free radicals from epoxides using a transition-metal radical. A powerful new tool for organic synthesis
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Bis(cyclopentadienyl)titanium(III) chloride reacts with epoxides by initial C-O homolysis. The regiochemistry of the opening is determined by the relative stabilities of the radicals. Depending on the reaction partners, these radicals undergo intramolecular (hex-5-enyl cyclization) or intermolecular additions to olefins. The resultant radicals are efficiently scavenged by a second equivalent of Ti(III) to afford the corresponding Ti(IV) derivative. Treatment of this intermediate with electrophiles such as H+ or halogens provides a route to functionalized cyclopentanes and other useful products. The radical initially formed from an epoxide can also be trapped by H-atom donors such as 1,4-cyclohexadiene or tert-butyl thiol, resulting in an overall reduction of the epoxide. In the absence of a H-atom donor or an olefin, this radical is trapped by Ti(III), resulting in a β-oxido-Ti organometallic species which undergoes facile elimination to give an olefin. The reaction conditions are remarkably mild and are applicable to very sensitive substrates.
- RajanBabu,Nugent, William A.
-
p. 986 - 997
(2007/10/02)
-
- Direct transformation of dialkyl sulfates into alkyllithium reagents by a naphthalene-catalysed lithiation
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The lithiation of primary and secondary dialkyl sufates with an excess of lithium powder in the presence of a catalytic amount of naphthalene (4 mol %) in THF at -78°C leads to the corresponding alkyllithium reagents (1:2 molar ratio) which react with different electrophiles, mainly carbonyl compounds, to yield after hydrolysis, the expected coupling products. This methodology represents an indirect way to transform alcohols into organolithium compounds through the corresponding dialkyl sulfates. When the same procedure is applied to five or six member cyclic sulfates (derived from 1,2- or 1,3-diols) only products arising from a β- or γ-elimination process (giving olefins or cyclopropanes), respectively, are obtained.
- Guijarro, David,Guillena, Gabricia,Mancheno, Balbino,Yus, Miguel
-
p. 3427 - 3436
(2007/10/02)
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- Naphthalene-catalysed lithiation of dialkyl sulfates: A new route for organolithium reagents
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The lithiation of primary and secondary dialkyl sulfates with an excess of lithium powder in the presence of a catalytic amount of naphthalene at -78°C leads to the corresponding alkyl-lithium reagents (1:2 molar ratio), which react with different electrophiles, mainly carbonyl compounds, to yield the expected coupling products. This methodology represents an indirect way for transforming alcohols into organolithium compounds through the corresponding dialkyl sulfates.
- Guijarro,Mancheno,Yus
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p. 5597 - 5600
(2007/10/02)
-
- GRIGNARD REAGENTS AS POWDERS : PREPARATION AND REACTIVITY
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The TDA-1 chelating agent is able to complex Grignard reagents.This complexation leads to powders.The preparation is general and the complexes "RMgX/TDA-1" are easily prepared from every type of Grignard reagents.These solids are stable under nitrogen and can be titrated and used as Grignard reagents.The study of their chemical reactivity shows a behaviour comparable to that of conventional Grignard reagents, the rate of reactions however being decreased.Selective addition onto a mixture of aldehyde and ketone is possible.Interestingly the reactions can be performed in hydrocarbon solvents (toluene, light petroleum, cyclohexane).
- Boudin, Alain,Cerveau, Genevieve,Chuit, Claude,Corriu, Robert J.P.,Reye, Catherine
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p. 171 - 180
(2007/10/02)
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- Amphiphilic Reactions by Means of Exceptionally Bulky Organoaluminum Reagents. Rational Approach for Obtaining Unusual Equatorial, Anti-Cram, and 1,4 Selectivity in Carbonyl Alkylation
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Exceptionally bulky, oxygenophilic organoaluminum reagents, methylaluminum bis(2,6-di-tert-4-alkylphenoxide) (MAD and MAT), have been successfully utilized for stereoselective activation of carbonyl moiety.Combination of MAD or MAT with carbon nucleophiles such as organolithiums or Grignard reagents generates a new amphiphilic reaction system in which the alkylation may be interpreted as the nucleophilic addition of a reactive organometallic compound to an electrophilically activated carbonyl substrate in order to account for the regio- and stereochemical consequences.In contrast to the ordinary alkylations, the amphilic alkylation disclosed herein would be categorized into the new, yet unexplored class of alkylation that exhibits high chemoselectivity to carbonyl compounds, and more significantly it allows excellent equatorial and anti-Cram selectivity in carbonyl alkylations, hitherto difficult by the existing methodologies.Further, unusual conjugate addition of organolithium reagents to α,β-unsaturated carbonyl compounds has been accomplished by using the amphiphilic reaction system.
- Maruoka, Keiji,Itoh, Takayuki,Sakurai, Minoru,Nonoshita, Katsumasa,Yamamoto, Hisashi
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p. 3588 - 3597
(2007/10/02)
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- THE PREPARATION OF LITHIUM ORGANOCUPRATES FROM VARIOUS Cu(I) SALTS
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Various Cu(I) salts have been tested as precursors for organocuprates in side-by-side comparisons under controlled conditions.CuCN and CuBr*SMe2 appear to be superior to CuI, CuBr, and CuCl.CuSCN and CuOTf are also good precursors in some circumstances.
- Bertz, Steven H.,Gibson, Charles P.,Dabbagh, Gary
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p. 4251 - 4254
(2007/10/02)
-
- ORGANOCERIUM REAGENTS FROM IODINE ACTIVATED CERIUM METAL AND ORGANIC IODIDES: THEIR REACTIONS WITH CARBONYL COMPOUNDS
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Cerium metal activated by a trace of iodine reacted smoothly with alkyl, allyl, and aryl iodides to give the corresponding organocerium reagents.The reaction of the organocerium reagents thus prepared in situ with carbonyl compounds gave not only Grignard-type adducts but also reduction and reductive coupling products.
- Fukuzawa, Shin-ichi,Fujinami, Tatsuo,Sakai, Shizuyoshi
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p. 179 - 186
(2007/10/02)
-
- AZO ANIONS IN SYNTHESIS. USE OF TRITYL- AND DIPHENYL-4-PYRIDYLMETHYLHYDRAZONES FOR REDUCTIVE C-C BOND FORMATION.
-
The lithium salts of trityl- and diphenyl-4-pyridylmethyl-hydrazones of both aldehydes and ketones react with electrophiles (alkyl halides, aldehydes, ketones, crotonates) at low temperature to form C-trapped azo compounds; these intermediates decompose homolytically with loss of nitrogen below room temperature and can be diverted in a synthetically useful way to alkanes, alkenes, alcohols or saturated esters.
- Baldwin, Jack E.,Adlington, Robert M.,Bottaro, Jeffrey C.,Kolhe, Jayant N.,Newington, Ian M.,Perry, Matthew W. D.
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p. 4235 - 4246
(2007/10/02)
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- REGIOSELECTIVE REDUCTIVE ELIMINATION OF ARYLOXYMETHYLETHYNYLCARBINOLS - SYNTHESIS OF ARYLOXYMETHYLALLENES
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Exclusive formation of allenes and alkenols during the reduction of aryloxymethylethynylcarbinols and ethynylcarbinols respectively, with lithium aluminiumhydride, is being reported.
- Rajamannar, T.,Balasubramanian, K. K.
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p. 3777 - 3780
(2007/10/02)
-
- Studies on the Occurrence of Hydrogen Transfer, 74. Electroreductive Hydrogenation Using Raney-Nickel-Powder as a Cathode
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Cathodically pretreated Raney-nickel-powder with a potential of -900 to -1000 mV (vs SCE) shows a positive potential shift of 200 to 300 mV in the presence of a hydrogen acceptor (coumarine or 1-ethinylcyclohexanol (1)).Pyridine and quinoline do not have any strong influence on the potential but retard the hydrogenation of coumarine.Acetylene derivatives as 1-ethinylcyclohexanol are hydrogenated in two steps applying a potential down to -1050 mV.At -1150 mV the selectivity is lost.With Raney-nickel-powder pretreated with pyridine or hydrogensulfide the two-step selectivity of the hydrogenation of 1 is preserved applying also a potential of -1200 mV. - Keywords: Heterogenous Hydrogenation Electrocatalysis, Electroreductive Hydrogenation, Raney-Nickel-Powder
- Horner, L.,Franz, Ch.
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p. 808 - 813
(2007/10/02)
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- ACTIVATION DE REACTIONS PAR LES POLYOXYDES D'ETHYLENE III. REDUCTIONS PAR L'EUTECTIQUE SODIUM-POTASSIUM
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Polyethylene oxides are efficient phase transfer catalysts which promote the reduction of CC, C=C bonds as well as aromatic substrates by the Na-K eutectic.Yields and general conditions of the reaction give it a generally useful synthetic value.
- Gaude, Didier,Goaller, Raymond Le,Luche, Jean-Louis,Pierre, Jean-Louis
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p. 5897 - 5898
(2007/10/02)
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- SEMIHYDROGENATION OF ACETYLENES; MODIFIED LINDLAR CATALYST
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The effect of doping Lindlar catalyst with different metal salts (shown in Table 1) on selectivity, during semihydrogenation of some acetylenes to the corresponding olefins, has been studied.Lindlar catalyst modified with MnCl2 has been found to be more selective and reproducible.
- Rajaram, J.,Narula, A. P. S.,Chawla, H. P. S.,Dev, Sukh
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p. 2315 - 2322
(2007/10/02)
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- N,N'-Bis(1-cyclohexyl-1-ethyl)-p-phenylenediamine, and rubber compounds containing the same
-
N,N'-Bis(1-cyclohexyl-1-ethyl)-p-phenylenediamine is disclosed as a novel compound, useful as an antidegradant for organic materials, such as rubber. Vulcanized or vulcanizable rubber compounds containing minor amounts of this compound show excellent resistance to ozone attack, under static or dynamic exposure.
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- Some studies on the solvolysis of 1-chloro-1-alkyl cycloalkanes
-
The effect of the bulk of the sidechain on the rate of solvolysis of 1-alkyl cyclopentyl, cyclohexyl, and cycloheptyl chlorides has been studied.With the exception of the t-butyl systems, the ratio of solvolysis rates for the three ring systems falls in a given series.The slower rate of solvolysis in the six-membered ring system may be due to an extra activation energy contribution caused by the conversion of a neutral chair form to the twist boat or half chair conformation, prior to the actual solvolysis.In the case of five- and seven-membered ring systems the formation of an intermediate carbonium ion is sterically favoured (I-strain or eclipsing interaction) consistent with earlier findings.The faster rate of solvolysis of 1-t-butylcycloalkyl chlorides is likely due to a rearrangement reaction where alkyl participation enhances the rate of solvolysis.
- Ranganayakulu, K.,Vasumathi Devi, M.,Balaji Rao, R.,Rajeswari, K.
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p. 1484 - 1489
(2007/10/02)
-