- EFFECT OF AN EXTERNAL MAGNETIC FIELD ON PHOTOLYSIS OF AQUEOUS SOLUTIONS OF CYCLOHEXANONE
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The effect of an external magnetic field on the ratio of the yields of the basic products of photolysis of aqueous solutions of cyclohexanone was investigated by high-resolution NMR spectroscopy.It was shown that the magnetic field does not significantly affect the yield of the products of the reaction with a 0.2 M concentration of the starting ketone, the yield of 5-hexenal decreases, and the yield of caproic acid and the rate of photolysis increase below 0.02 M.The observed effects are explained by association of cyclohexanone with involvement of the HFI mechanism from the theory of "radical pairs".
- Skakovskii, E. D.,Ogorodnikova, M. M.,Tychinskaya, L. Yu.,Chuiko, V. A.,Rykov, S. V.
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Read Online
- Cerium(IV) Carboxylate Photocatalyst for Catalytic Radical Formation from Carboxylic Acids: Decarboxylative Oxygenation of Aliphatic Carboxylic Acids and Lactonization of Aromatic Carboxylic Acids
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We found that in situ generated cerium(IV) carboxylate generated by mixing the precursor Ce(OtBu)4 with the corresponding carboxylic acids served as efficient photocatalysts for the direct formation of carboxyl radicals from carboxylic acids under blue light-emitting diodes (blue LEDs) irradiation and air, resulting in catalytic decarboxylative oxygenation of aliphatic carboxylic acids to give C-O bond-forming products such as aldehydes and ketones. Control experiments revealed that hexanuclear Ce(IV) carboxylate clusters initially formed in the reaction mixture and the ligand-to-metal charge transfer nature of the Ce(IV) carboxylate clusters was responsible for the high catalytic performance to transform the carboxylate ligands to the carboxyl radical. In addition, the Ce(IV) carboxylate cluster catalyzed direct lactonization of 2-isopropylbenzoic acid to produce the corresponding peroxy lactone and ?3-lactone via intramolecular 1,5-hydrogen atom transfer (1,5-HAT).
- Hirosawa, Keishi,Mashima, Kazushi,Satoh, Tetsuya,Shinohara, Koichi,Shirase, Satoru,Tamaki, Sota,Tsurugi, Hayato
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supporting information
(2020/03/25)
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- Catalytic Generation and Use of Ketyl Radical from Unactivated Aliphatic Carbonyl Compounds
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Generation of a ketyl radical from unactivated aliphatic carbonyl compounds is an important strategy in organic synthesis. Herein, catalytic generation and use of a ketyl radical for the reductive coupling of aliphatic carbonyl compounds and styrenes by organic photoredox catalysis is described. The method is applicable to both aliphatic ketones and aldehydes to afford the corresponding tertiary and secondary alcohols in continuous flow and batch. Preliminary mechanistic investigation suggests the catalytic formation of a ketyl radical intermediate.
- Seo, Hyowon,Jamison, Timothy F.
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supporting information
p. 10159 - 10163
(2019/12/24)
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- Synthesis, characterization and catalytic performance in cyclohexane transformation by Bi2O3/MCM-41 nanocomposite materials
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The nanoparticles of Bi2O3 supported on mesoporous MCM-41 were prepared in a simple way and were well characterized. The oxidation of cyclohexane to cyclohexanol and cyclohexanone under 1 atmospheric pressure of air in the absence of any solvent and reducing agents with Bi2O3/MCM-41 nanocomposites were considered. These nanoparticles of Bi2O3 supported on mesoporous MCM-41 were found to be the very effective catalysts for cyclohexane oxidation with air in a temperature range of 280–370 ?C. The influences of reaction temperature, the loading amount of Bi2O3 and space velocity on the oxidation of cyclohexane were also studied, and optimized conditions were investigated.
- Mozaffari, Majid,Ebadi, Amin
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p. 1643 - 1651
(2017/11/20)
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- Applications of a high performance platinum nanocatalyst for the oxidation of alcohols in water
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Nanoparticles of platinum (NP-Pt), have been synthesized by supporting high nuclearity anionic carbonyl cluster (Chini cluster) on a water soluble anion exchanger, and the performance of this material, 1, as an oxidation catalyst for alcohols in water has been studied. The E-factor for the synthesis of NP-Pt by this method has been calculated and compared with that of other NP-Pt recently reported in the literature. With 1 as a catalyst, oxidations of a variety of primary and secondary alcohols by dioxygen are achieved and high turnover numbers and selectivities are obtained. The performances of 1 in the oxidation of benzyl alcohol and 1-phenylethanol are compared with those of three other platinum catalysts. These are platinum nanoparticles 2 prepared by the hydrogen reduction of [PtCl6]2- supported on the same water soluble polymer, 5% Pt on carbon, and 5% Pt on alumina, designated as 3 and 4, respectively. 1 has been found to be considerably more active than 2-4 and also other reported water soluble platinum nanocatalysts. After many turnovers (~1000 and ~165 for benzyl alcohol and 1-phenyl ethanol, respectively) partial deactivation (~ 40%) is observed, but the deactivated catalyst can be fully regenerated by treatment with dihydrogen. The TEM data of fresh, deactivated and regenerated 1 show a correlation between the particle size and activity. A mechanism consistent with this and other experimental observations including XPS data is proposed.
- Maity, Prasenjit,Gopinath, Chinnakonda S.,Bhaduri, Sumit,Lahiri, Goutam Kumar
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experimental part
p. 554 - 561
(2010/04/23)
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- Facile photochemical transformation of alkyl aryl selenides to the corresponding carbonyl compounds by molecular oxygen: Use of selenides as masked carbonyl groups
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(Chemical Equation Presented) Alkyl aryl selenides with and without functional groups on the alkyl group were transformed efficiently into the corresponding carbonyl compounds, particulary primary alkyl aryl selenides in good yields, by a simple photolysis in the presence of air or oxygen. This transformation can be conducted without protection of functional groups. The yield of carbonyl compounds was much affected by the solvent viscosity, reaction temperature, concentration of dissolved oxygen in the solvents, wavelength of light, and structure of the aryl substituents. The present study indicates that aryl selenides can be considered as a masked carbonyl group that can be easily converted to a carbonyl group by very mild reaction conditions even in the presence of various unprotected functional groups. Therefore, this functional group transformation can be used as an important tool in organic synthesis due to its simplicity and mild reaction condition.
- Hyugano, Takeshi,Liu, Suyou,Ouchi, Akihiko
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supporting information; scheme or table
p. 8861 - 8866
(2009/04/05)
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- Synthesis of fused piperidinones through a radical-ionic cascade
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(Chemical Equation Presented) Azabicyclo[4.3.0]nonanes were assembled, from chiral allylsilanes possessing an oxime moiety, using a stereocontrolled formal [2 + 2 + 2] radical-ionic process. The cascade involves the addition of an α-iodoester to the less substituted end of the enoxime which is then followed by a 5-exo-trig cyclization onto the aldoxime function, producing an alkoxyaminyl radical species which finally lactamizes to afford the titled piperidinone. High levels of stereoinduction were observed, demonstrating the ability of a silicon group located at the allylic position to efficiently control the stereochemistry of the two newly created stereogenic centers. When the radical cascade was extended to ketoximes, the resulting sterically hindered alkoxyaminyl radical did not react further with the initiator Et3B to produce the expected nucleophilic amidoborane complex. In sharp contrast, this long-lived radical recombined with the initial α-stabilized ester radical to produce a cyclopentane incorporating two ester fragments.
- Godineau, Edouard,Schenk, Kurt,Landais, Yannick
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supporting information; experimental part
p. 6983 - 6993
(2009/05/09)
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- A stereocontrolled access to ring-fused piperidines through a formal [2+2+2] process
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(Chemical Equation Presented) A formal [2+2+2] process has been devised that allows the stereocontrolled formation of ring-fused piperidines from allylsilanes possessing an oxime moiety. The cascade involves an intermolecular radical addition of an α-iodoacetate onto an allylsilane double bond, which is followed by a 5-exo-trig cyclization onto an oxime and is completed by the formation of the amide bond by nucleophilic attack of the amine onto the ester function.
- Godineau, Edouard,Schaefer, Christian,Landais, Yannick
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p. 4871 - 4874
(2007/10/03)
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- Erbium(III) triflate: A valuable catalyst for the rearrangement of epoxides to aldehydes and ketones
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Rearrangement of epoxides is performed with erbium triflate as catalyst. In contrast to most proposed catalysts for this re-action, erbium triflate works well with both aromatic and aliphatic epoxides.
- Procopio, Antonio,Dalpozzo, Renato,De Nino, Antonio,Nardi, Monica,Sindona, Giovanni,Tagarelli, Antonio
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p. 2633 - 2635
(2007/10/03)
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- Polyfluorinated quaternary ammonium salts of polyoxometalate anions: Fluorous biphasic oxidation catalysis with and without fluorous solvents
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[Matrix presented] Polyfluorinated quaternary ammonium cations, [CF 3(CF2)7(CH2)3] 3CH3N+ (RFN+), were synthesized and used as countercations for the [WZnM2(H 2O)2(ZnW9O34)2] 12- (M = Mn(II), Zn(II)) polyoxometalate. The (RFN +)12[WZnM2(H20)2 (ZnW9O34)2] compounds were fluorous biphasic catalysts for alcohol and alkenol oxidation, and alkene epoxidation with aqueous hydrogen peroxide. Reaction protocols with or without a fluorous solvent were tested. The catalytic activity and selectivity was affected by both the hydrophobicity of the solvent and the substrate.
- Maayan, Galia,Fish, Richard H.,Neumann, Ronny
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p. 3547 - 3550
(2007/10/03)
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- Radical cyclization in heterocycle synthesis. Part 13: Sulfanyl radical addition-cyclization of oxime ethers and hydrazones connected with alkenes for synthesis of cyclic β-amino acids
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A combination of sulfanyl radical addition-cyclization of the oxime ethers and hydrazones connected with alkenes and subsequent conversion of a phenylsulfanylmethyl group to a carboxyl group provides a novel method for the construction of the cyclic β-amino acids. Upon treatment with thiophenol in the presence of AIBN, the oxime ethers and hydrazones smoothly underwent sulfanyl radical addition-cyclization to give the 2-(phenylsulfanylmethyl)cycloalkylamine. This method was successfully applied to the practical synthesis of 2-aminocyclopentanecarboxylic acid and 4-amino-3-pyrrolidinecarboxylic acid.
- Miyata, Okiko,Muroya, Kanami,Kobayashi, Tomoko,Yamanaka, Rina,Kajisa, Seiko,Koide, Junko,Naito, Takeaki
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p. 4459 - 4479
(2007/10/03)
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- Arrhenius parameters for the reaction HO2 + cyclohexane between 673 and 773 K, and for H atom transfer in cyclohexylperoxy radicals
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The addition of cyclohexane (CHX) to O2 + tetramethylbutane (TMB) mixtures at 673-773 K in aged boric-acid-coated Pyrex vessels was studied to obtain kinetic data for the reaction of HO2 radicals with CHX. The contribution by OH radi
- Walker,Handford-Styring
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p. 2043 - 2052
(2007/10/03)
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- Catalytic partial oxidation of cyclohexane in a single-gauze reactor
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C6H12 catalytic partial oxidation in a single-gauze reactor produced ~ 85% selectivity to olefins and oxygenates at 25% C6H12 conversion and 100% oxygen conversion, with cyclohexene and 5-hexenal as the dominant products. Experiments were performed with a 90% platinum-10% rhodium single gauze (~ 90-μm wire diameter) at C6H12/O2 molar ratios of 0.4-5, flow rates of 1-3 std L/min, preheat temperatures of 100°-300°C, N2 dilution from 5% to the air composition, and 1.2-2 atm. The C6H12/O2 ratio was the most important variable for operation of the single-gauze reactor because temperatures, reactant conversions, and product selectivities all changed significantly as C6H12/O2 was varied. Low dilution favored olefin production while high dilution suppressed the homogeneous reactions necessary for oxygenate formation. Oxygenates were also favored by high flow rates and low inlet temperatures. Higher reactor pressures (≤ 2 atm) increased the yield of cyclohexene and 5-hexenal and allowed complete oxygen conversion. Cyclohexanone was produced with 5% selectivity at C6H12/O2 ~ 4. Reaction pathways for C6H12 partial oxidation were hypothesized, and the products were consistent with the proposed surface-assisted gas-phase sequences.
- O'Connor,Schmidt
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p. 245 - 256
(2007/10/03)
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- A Tandem Amino-Cope Rearrangement/Enamine Alkylation Reaction
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Thermally induced [3,3]-sigmatropic rearrangement of 3-amino-1,5-diene substrates occurs to give the corresponding enamine products in high yield and with excellent trans:cis enamine selectivity. The enamine produced during the amino-Cope rearrangement has been directly derivatized, representing the first report of a tandem amino-Cope rearrangemenl/enamine alkylation reaction. The potential of this novel synthetic strategy is outlined.
- Allin, Steven M.,Button, Martin A. C.,Shuttleworth, Stephen J.
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p. 725 - 727
(2007/10/03)
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- Generation of Acyl Radicals from 2-Naphthyl Thioesters
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A series of S-2-naphthyl thioesters were synthesized from the corresponding carboxylic acids or acid chlorides.Irradiation of these thioesters in the presence of a hydrogen source (i.e., 1,4-cyclohexadiene) generated the corresponding aldehydes.In this fashion, primary, secondary, tertiary, and aryl carboxylic acids were converted to the aldehydes in high yields.Intramolecular radical cyclization reactions support the hypothesis that the reaction proceeds via the formation of acyl radicals.The formation of aldehydes was not perturbed by possible Norrish Type II reactions.
- Penn, John H.,Liu, Fang
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p. 2608 - 2612
(2007/10/02)
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- PHOTOCHEMISTRY OF AQUEOUS SOLUTIONS OF CYCLOHEXANONE
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From the temperature and concentration dependence of the yields of the products from photochemical reactions in aqueous solutions of cyclohexanone (studied by GLC and NMR) and from the appearance of magnetic and spin effects in these reactions (investigated by NMR spectroscopy) it was possible to determine the reaction mechanisms and the roles of association of the ketone molecules and the conformations of the obtained triplet biradicals. It was established that abstraction of a hydrogen atom from the water molecule by the excited molecule of the substrate with the formation of 1,3-cyclohexanediol occurred in addition to α-cleavage of the initial ketone. The respective ketene and 5-hexenal are formed with the participation of various configurations of the intermediate triplet biradical.
- Skakovskii, E. D.,Ogorodnikova, M. M.,Tychinskaya, L. Yu.,Rykov, S. V.
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p. 1109 - 1114
(2007/10/02)
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- Lithiation and Isomerization of Allylic Amines as a General Route to Enamines and Their Carbonyl Derivatives
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lithium, readily prepared by the lithiation of allyldiphenylamine with n-butyllithium in THF, undergoes alkylation either with organic halides or with carbonyl or azomethine derivatives to yield enamines, which can be converted by protons or other electrophiles into aldehydes or into five-membered heterocycles; lithiation of such allyldiarylamines with other reagents leads principally to isomerisation to enamines (with lithium diisopropylamide) or to carbenoid intermediates (tert-butyllithium and potassium tert-butoxide).
- Eisch, John J.,Shah, Jamshed H.
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p. 2955 - 2957
(2007/10/02)
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- One-Flask, Regiospecific Conversions of Allylic Alcohols into Two-Carbon-Extended, Conjugated Dienoate Esters. Use of a New Sulfinyl Orthoester
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Sixteen differently substituted primary and secondary allylic alcohols are shown to react with sulfinyl orthoacetate 1 at 100 deg C sequentially via a sigmatropic rearrangement and then a β-elimination of benzenesulfenic acid to form conjugated dienoate esters 5-13 in 45-95percent yields.This one-flask, intramolecular carbon-carbon bond-forming process represents a simple and convenient method for regiospecific γ-attachment of a two-carbon (ethoxycarbonyl)methylene unit via the synthetic equivalent of an SN2' process.Two examples are given in which rationally designed dienoates 20 and 24, prepared via this one-flask process and carrying a pendant alkene unit, undergo intramolecular 2+4 cycloaddition producing bicyclic cyclohexenes 21 and 25.
- Posner, Gary H.,Crouch, R. David,Kinter, Chris M.,Carry, Jean-Christophe
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p. 6981 - 6987
(2007/10/02)
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- Oxidative Grob Fragmentation of γ-Tributylstannyl Alcohols with a Combination of Iodosylbenzene, Dicyclohexylcarbodiimide, and Boron Trifluoride
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Exposure of cyclic γ-stannyl alcohols, prepared from cyclic vinyl ketones, to a combination of iodosylbenzene, dicyclohexylcarbodiimide, and boron trifluoride-diethyl ether in dichlorometane undergoes an oxidative Grob fragmentation to give unsaturated carbonyl compounds.The dicyclohexylcarbodiimide in this reaction apparently activates iodosylbenzene and decreases Lewis acidity of boron trifluoride.The fact that the iodine(III)-mediated Grob fragmentation proceeds stereospecifically suggests the fragmentation is concerted.The fragmentation, combined with conjugate addition of (tributylstannyl)lithium and reduction or alkylation, offers an efficient procedure for the reductive and alkylative ring opening of cyclic vinyl ketones.Since cis-benzyl ether 36, after quenching of the reaction mixture with aqueous NH4Cl, afforded the chlorostannane 37, the reaction mechanism involving the formation of iodine(III) species 32 with two oxygen ligands at iodine proposed.
- Ochiai, Masahito,Ukita, Tatsuzo,Iwaki, Shigeru,Nagao, Yoshimitsu,Fujita, Eiichi
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p. 4832 - 4840
(2007/10/02)
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- SUBSTITUENT DIRECTED OXIDATIVE CYCLIZATION WITH CETYLTRIMETHYLAMMONIUM PERMANGANATE: A GENERAL APPROACH TO THE SYNTHESIS OF γ- AND δ-LACTONES
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Treatment of primary, secondary or tertiary γ- and δ-hydroxyolefins with cetyltrimethylammonium permanganate gives good yields of γ- and δ-lactones by oxidative cyclization, with loss of one carbon.
- Rathore, Rajendra,Vankar, Padma S.,Chandrasekaran, S.
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p. 4079 - 4082
(2007/10/02)
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- INTRAMOLECULAR DIELS-ALDER REACTIONS OF ETHYL 2,4,9-DECATRIENOATE AND 2,4,10-UNDECATRIEONATE
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The title compounds undergo intramolecular Diels-Alder reactions at 180 deg C to give ester-substituted hydrindane and decalin ring systems, with trans/cis ratios of 43:57 and 50:50, respectively.
- Lin, Yi-Tsong,Houk, K. N.
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p. 2517 - 2520
(2007/10/02)
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- Intramolecular Trapping of Alkyl- and Arylrhodium Hydride Intermediates in the Decarbonylation of Aldehydes by Chlorotris(triphenylphosphine)rhodium
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The reaction of 5-hexenal with RhCl(PPh3)3 (1) or 2 (5) gives some cyclopentane.The reaction of 2-allylbenzaldehyde with 5 gives a good yield of indan.These cyclization reactions to give cyclopentanes, and other reactions of Δ4-enals to give cyclopropanes, reveal the presence of intermediate alkyl- and arylrhodium hydride complexes on the pathway for decarbonylation of aldehydes.The formation of nortricyclene from endo-5-norbornene-2-carboxaldehyde shows that the alkylrhodium hydride must be formed with retention of stereochemistry at the α-carbon of the aldehyde.
- Kampmeier, J. A.,Harris, S. H.,Mergelsberg, I
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p. 621 - 625
(2007/10/02)
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- 1,4-Fragmentation of γ-Tributylstannyl Alcohols by a Hypervalent Organoiodine Compound: a New Synthesis of Unsaturated Carbonyl Compounds
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1,4-Fragmentation of γ-tributylstannyl alcohols using iodosylbenzene, boron trifluoride-diethyl ether, and dicyclohexylcarbodiimide produces unsaturated carbonyl compounds; the fragmentation, combined with conjugate addition of tributylstannyl-lithium and reduction or alkylation, offers an efficient procedure for the reductive and alkylative ring opening of cyclic vinyl ketones.
- Ochiai, Masahito,Ukita, Tatsuzo,Nagao, Yoshimitsu,Fujita, Eiichi
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p. 1007 - 1008
(2007/10/02)
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- Organic Chemistry by Infrared Lasers. 4. Laser-Induced Reactions of γ-Unsaturated Alcohols
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The laser-induced chemistry of 3-buten-1-ol (1), 3-butyn-1-ol (2), 3,4-pentadien-1-ol (3), 2-isopropenyl-5-methylcyclohexanol (l-isopulegol; 4), and 1,5-hexadien-3-ol (5) is described.Retro-ene reactions occur in all cases, though with compound 5 a competitive oxy-Cope reaction is also observed.The reactions are generally clean and give rise to conversions in the range of 48-78 percent after 300-500 pulses.In these reactions between 2-10 photons are absorbed per molecule per pulse, and in some instances as much as 40 percent conversion is obtained after five pulses.The laser-induced chemistry seems to follow the known thermal chemistries of these systems.
- Madison, Stephen A.,Chen, Ruth,Keehn, Philip M.
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p. 1336 - 1340
(2007/10/02)
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- Intramolecular Addition of Alkoxy Radicals. Part 4. Reductive Cyclisation of Olefinic Hydroperoxides
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Pent-4-enyl hydroperoxide reacts with reducing salts (FeX2, TiCl3) to afford tetrahydrofurfuryl compounds (halides or dimers) in high yield from the selective cyclisation of the pent-4-enyloxy radical.Analogous behaviour is observed for photolysis although the yields of cyclic products are lower.The photolysis of hex-5-enyl hydroperoxide does not yield cyclic products but these are observed when this hydroperoxide is reduced by FeCl2.It is suggested that metallic salts are able to complex the alkoxyl radicals thereby making them more electrophilic and hence more prone to cyclise.
- Taillez, Bernard,Bertrand, Michele Paula,Surzur, Jean-Marie
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p. 547 - 554
(2007/10/02)
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- Photoreduction of Cyclic α-Fluoroketones
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Irradiation of the α-fluoroketones 1a and 6a in i-PrOH selectively affords the parent ketone 1b and 6b, respectively.It is concluded that in this solvent heterolytic C-F bond cleavage of the radical -formed by electron transfer to the excited fluoroketone- is a faster process than the subsequent protonation by the cation radical of the solvent.In cyclohexane 1b and 6b are only formed a minor amounts, the fluorinated RH-reduction product 4 now being the major product from 1a.In non-reducing solvents as t-BuOH or benzene 2-fluorocyclohexanone (1a) exhibits a similar behavior as cyclohexanone (1b) on excitation.The quantum yields for α-cleavage are alike for both compounds, but oxetane formation with 2-methylpropene as olefinic component occurs much more readily with 1a than with 1b.
- Reinholdt, Karin,Margaretha, Paul
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p. 2534 - 2539
(2007/10/02)
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- Cope Rearrangements of Donor Substituted 1,5-Hexadienes
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Alkoxy, alkylthio, and dialkylamino groups in position 3 of 1,5-hexadiene and in position 2 of 3,3-dimethyl-1,5-hexadiene have rather small effects on the Cope rearrangement (maximum rate acceleration by a factor of 60; maximum ΔEa = 5,5 kcal/mol = 23 kJ/mol).The pattern of substituent effects is more consistent with a diradicaloid mechanism than with a concerted sigmatropic rearrangement.
- Dollinger, Michael,Henning, Wolfgang,Kirmse, Wolfgang
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p. 2309 - 2325
(2007/10/02)
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- Process for producing lactones from unsaturated carbonyl compounds
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A method for producing an alkyl substituted lactone including the steps of alkylating an unsaturated ketone with a C1 -C12 alkyl organometallic reagent such as a Grignard reagent or an alkali metal alkyl, to form an unsaturated alcohol, and oxidatively cleaving the unsaturated alcohol to form the lactone, and recovering the lactone.
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- Hg(63P1) Photosensitization of Cyclohexanone. Role of Triplet Biradical Intermediates
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Hg(63P1) photosensitization of cyclohexanone results in the formation of pent-l-ene, cyclopentane and hex-5-enal, just as observed in the direct photolysis.As the pressure of added SF6 or Ar bath gas is increased, both the total product quantum yield and that of the hydrocarbon products decrease, while that of hex-5-enal increases.A comprehensive mechanism, differing in detail from those previously proposed, is now formulated to account quantitatively for the experimental observations.Two sequentially formed, energy randomized, vibrationally excited triplet biradicals are believed to be the important intermediates that lead to product formation.Thus α-C-C bond cleavage of triplet cyclohexanone yields an acyl-alkyl biradical. 3B*, that can give rise to both hex-5-enal and also, by loss of CO, to the penta-l.5-diyl biradical, 3PD*, the precursor of the hydrocarbon products.Rate constants for intersystem crossing of the two biradicals are deduced along with that for the fragmentation of 3B*.An RRKM treatment of this decomposition suggests that the observed rate constant is best fitted using a biradical excitation energy calculated by assuming a heat of formation for 3B greater than the value computed by conventional methods, which neglect electronic interaction.In addition, relative rate constants are obtained for the intramolecular disproportionation and cyclisation of 1B and 1PD when both vibrationally excited and thermalized.It is concluded that the critical energy for ring closure of 1PD is greater than that for isomerization to pent-l-ene.
- Baulch, D. L.,Lenney, Colburn P. W.,Montague, D. C.
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p. 1803 - 1812
(2007/10/02)
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- Acyl Radicals: the Relationship between Electron Spin Resonance Spectra, Structure, and Stability in a Family of ?-Radicals
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A series of saturated and unsaturated acyl radicals, RC.=O, have been generated in fluid solution, principally by the photolysis of di-t-butyl peroxide in the presence of the corresponding aldehyde.Most of th acyl radicals show well-resolved hyperfine splittings, and the values of a(Hβ( correlate with the n.m.r. coupling constants 3J(CHCHO) in the parent aldehyde.It is concluded that the acyl radicals and the corresponding aldehydes have similar structures.
- Davies, Alwyn G.,Sutcliffe, Roger
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p. 819 - 824
(2007/10/02)
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- Homologation of Carbonyl Compounds to Aldehydes with Lithium Bis(ethylenedioxyboryl)methide
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Tris(ethylenedioxyboryl)methane reacts with methyllithium at -78 deg C in THF to form lithium bis(ethylenedioxyboryl)methide, which reacts with aldehydes and ketones to form 1-alkene-1-boronic esters.These need not be isolated for efficient oxidation by sodium perborate to the homologated aldehydes, which are easily purified.Systematic investigation of the reaction conditions to optimize yields at each step was undertaken.Possibly hazardous 2:1 aldehyde-hydrogen peroxide adducts were found to form under neutral conditions with dilute (5percent) hydrogen peroxide.Hydrogenperoxide was also found to cause some carbon-carbon bond cleavage during oxidation of alkeneboronic acids.Both problems were avoided by the use of sodium perborate instead.Reaction of lithium bis(ethylenedioxyboryl)methide with benzoyl chloride or methyl benzoate followed by hydrolysis was found to yield acetophenone.A significant error in one previous description of the synthesis of the key starting material, tris(dimethoxyboryl)methane, is noted.
- Matteson, Donald S.,Moody, Robert J.
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p. 1091 - 1095
(2007/10/02)
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- Process for synthesizing zearalanone and related compounds
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This invention provides a new synthesis for zearalanone and for related compounds having more or fewer carbon atoms in the non-aromatic ring than does zearalanone, which related compounds and zearalanone are represented by the formula SPC1 Wherein X is an integer having a value from 2 to 6 inclusive and Y is an integer having a value from 2 to 8 inclusive. It also provides for new methods of making compounds useful in the synthesis of zearalanone and related compounds. The new compounds useful as intermediates are 2,7-octadienoic acid; methyl 2,7-octadienoate; sodium ethyl 6-(4-pentenyl)-β-dihydroresorcylate; ethyl 6-(4-pentenyl)-β-dihydroresorcylate; sodium methyl 6-(4-pentenyl)-β-dihydroresorcylate; methyl 6-(4-pentenyl)-β-dihydroresorcylate; methyl 3-bromo-6-(4-pentenyl)-β-dihydroresorcylate; methyl 6-(4-pentenyl)-β-resorcylate; ethyl 6-(4-pentenyl)-β-resorcylate; ethyl 6-(4-pentenyl)-β-resorcylate dibenzyl ether; and 4-penten-2-yl 6-(4-pentenyl)-β-resorcylate dibenzyl ether.
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