- Structure-Activity Relationships of Cyclopropene Compounds, Inhibitors of Pheromone Biosynthesis in Bombyx mori
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According to the synthetic route for 11,12-methylenehexadec-11-enoic acid [10-(2-butyl-1-cyclopropenyl)decanoic acid] and the amide, their related cyclopropene compounds, which possessed a propene ring at the 7,8-, 9,10-, or 13,14-position in a C16 chain and the 11,12-position in a C14 or C18 chain, were synthesized via the corresponding 1-alkyl-1,2,2-tribromocyclopropane. Their activities as biosynthetic inhibitors of bombykol [(10E, 12Z)-10,12-hexadecadien-1-ol; sex pheromone of the silkworm moth Bombyx mori L.] were measured with virgin female silkworm moths in vivo. The 7,8-methylene compounds were inactive even at the dose of 10 μg/gland, but other compounds at 1 μg/gland inhibited the conversion of [16,16,16-2H3]hexadecanoic acid to bombykol to some extent. Each amide showed stronger inhibitory activity than the corresponding acid, and the 11,12-methylene amide with a C16 chain was the strongest (I50 = 0.016 μg/gland) among the tested compounds. Furthermore, experiments comparing the incorporation of [1-14C]hexadecanoic acid into bombykol and another alcohol component in the pheromone gland, (Z)-11-hexadecen-1-ol, suggested that the Δ11-desaturation was blocked by 9,10- and 11,12-methylene compounds and the subsequent Δ10,-12-desaturation by 11,12- and 13,14-methylene compounds.
- Ando, Tetsu,Ohno, Ryuta,Ikemoto, Kazuhisa,Yamamoto, Masanobu
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- Br?nsted Acid-Catalyzed Enantioselective Iodocycloetherification Enabled by Triphenylphosphine Selenide Cocatalysis
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Enantioselective iodocycloetherifications can be conducted using sterically highly demanding BINOL-based phosphoric acid diesters as catalyst. To achieve highly enantioselective reactions, cocatalysis by triphenylphosphine selenide is necessary. With coca
- Daniliuc, Constantin G.,Guria, Sudip,Hennecke, Ulrich
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- Metal-free regioselective hydrobromination of alkynes through CH/CBr activation
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A metal-free regioselective hydrobromination of alkynes has been developed to provide the Markovnikov-type vinyl bromides in good yields using dibromomethane/N,N-dimethylaniline as in-situ 'HBr' source. This protocol also represents an elegant example of the activation of sp2 CH and CBr bonds in one pot, in which 'HBr' is generated and transferred under mild metal-free conditions. D-incorporated experiments were employed to investigate the reaction mechanism and a plausible reaction path was proposed.
- Chen, Xiuling,Chen, Tieqiao,Xiang, Yuqiang,Zhou, Yongbo,Han, Daoqing,Han, Li-Biao,Yin, Shuang-Feng
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supporting information
p. 4572 - 4575
(2014/12/10)
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- Iridium-catalyzed enantioselective hydrogenation of alkenylboronic esters
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Choose the right ligand: An iridium complex derived from a phosphino-imidazoline ligand is a highly efficient catalyst for the asymmetric hydrogenation of terminal vinyl boronic esters (see scheme). On the other hand, trisubstituted alkenyl-boronates can
- Ganic, Adnan,Pfaltz, Andreas
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supporting information; experimental part
p. 6724 - 6728
(2012/07/28)
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- Ruthenium-catalyzed transformation of aryl and alkenyl triflates to halides
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Aryl triflates were transformed to aryl bromides/iodides simply by treating them with LiBr/NaI and [Cp*Ru(MeCN)3]OTf. The ruthenium complex also catalyzed the transformation of alkenyl sulfonates and phosphates to alkenyl halides under mild conditions. Aryl and alkenyl triflates undergo oxidative addition to a ruthenium(II) complex to form η'1- arylruthenium and 1-ruthenacyclopropene intermediates, respectively, which are transformed to the corresponding halides.
- Imazaki, Yusuke,Shirakawa, Eiji,Ueno, Ryota,Hayashi, Tamio
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supporting information
p. 14760 - 14763
(2012/11/07)
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- α-Selective Ni-catalyzed hydroalumination of aryl- and alkyl-substituted terminal alkynes: Practical syntheses of internal vinyl aluminums, halides, or boronates
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A method for Ni-catalyzed hydroalumination of terminal alkynes, leading to the formation of α-vinylaluminum isomers efficiently (>98% conv in 2-12 h) and with high selectivity (95% to >98% α), is described. Catalytic α-selective hydroalumination reactions proceed in the presence of a reagent (diisobutylaluminum hydride; dibal-H) and 3.0 mol % metal complex (Ni(dppp)Cl2) that are commercially available and inexpensive. Under the same conditions, but with Ni(PPh3)2Cl2, hydroalumination becomes highly β-selective, and, unlike uncatalyzed transformations with dibal-H, generates little or no alkynylaluminum byproducts. All hydrometalation reactions are reliable, operationally simple, and practical and afford an assortment of vinylaluminums that are otherwise not easily accessible. The derived α-vinyl halides and boronates can be synthesized through direct treatment with the appropriate electrophiles [e.g., Br 2 and methoxy(pinacolato)boron, respectively]. Ni-catalyzed hydroaluminations can be performed with as little as 0.1 mol % catalyst and on gram scale with equally high efficiency and selectivity.
- Gao, Fang,Hoveyda, Amir H.
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supporting information; experimental part
p. 10961 - 10963
(2010/09/17)
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- Ruthenium-catalyzed transformation of alkenyl triflates to alkenyl halides
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In the presence of a ruthenium catalyst, alkenyl triflates were found to be transformed to the corresponding bromides, chlorides and iodides simply by treatment with a lithium halide (1.2 equiv.). The Royal Society of Chemistry 2009.
- Shirakawa, Eiji,Imazaki, Yusuke,Hayashi, Tamio
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supporting information; experimental part
p. 5088 - 5090
(2009/12/08)
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- Rh-catalyzed enantioselective hydrogenation of vinyl boronates for the construction of secondary boronic esters
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Rh-catalyzed hydrogenation of prochiral vinyl boronates occurs in an enantioselective fashion in the presence of the chiral ligand Walphos 1. This transformation provides access to chiral secondary organoboronates that are not available from alkene hydrob
- Moran, Wesley J.,Morken, James P.
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p. 2413 - 2415
(2007/10/03)
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- Fe(III) halides as effective catalysts in carbon-carbon bond formation: Synthesis of 1,5-dihalo-1,4-dienes, αβ-unsaturated ketones, and cyclic ethers
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(Chemical Equation Presented). Iron(III) halides have proven to be excellent catalysts in the coupling of acetylenes and aldehydes. When terminal acetylenes were used the main products obtained were 1,5-dihalo-1,4-dienes with (E,Z)-stereochemistry contaminated in some cases with (E)-α,β- unsaturated ketones. The former carbonyl derivatives were the sole products isolated when nonterminal aromatic alkynes were used. When homopropargylic alcohols were used, a Prins-type cyclization occurred yielding 2-alkyl-4-halo-5,6-dihydro-2H-pyrans. In addition, anhydrous ferric halides are also shown to be excellent catalysts for the standard Prins cyclization with homoallylic alcohols. Isolation of an intermediate acetal, calculations, and alkyne hydration studies provide substantiation of a proposed mechanism.
- Miranda, Pedro O.,Diaz, David D.,Padron, Juan I.,Ramirez, Miguel A.,Martin, Victor S.
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- Stable ethylene inhibiting compounds and methods for their preparation
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A method to inhibit the ethylene response in plants with cyclopropene compounds by first generating stable cyclopropane precursor compounds and then converting these compounds to the gaseous cyclopropene antagonist compound by use of a reducing or nucleophilic agent.
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- Methods of blocking an ethylene response in plants using cyclopropene derivatives
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Methods of applying C5-20cyclopropene derivatives and compositions thereof to block ethylene receptors in plants are disclosed. One such method comprises applying to the plant an effective ethylene response-inhibiting amount of cyclopropene derivatives or compositions thereof. Also disclosed are methods of inhibiting abscission in plants, methods of prolonging the life of cut flowers, methods of inhibiting ripening of picked fruits, and methods of inhibiting ripening of picked vegetables.
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- Methods of blocking an ethylene response in plants using cyclopropene derivatives
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Methods of applying cyclopropene derivatives and compositions thereof to block ethylene receptors in plants are disclosed. One such method comprises applying to the plant an effective ethylene response-inhibiting amount of cyclopropene derivatives or compositions thereof. Also disclosed are methods of inhibiting abscission in plants, methods of prolonging the life of cut flowers, methods of inhibiting ripening of picked fruits, and methods of inhibiting ripening of picked vegetables.
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- A tripartite asymmetric allylboration - Silicon tethered alkene ring closing metathesis - In situ ring opening protocol for the regiospecific generation of functionalized (E)-disubstituted homoallylic alcohols
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Molybdenum carbene 6 catalyzed ring closing metathesis of (alkenyl)silyl ethers of homochiral allylic alcohols to afford 1,2-oxasilines which were elaborated in situ to give (E)-4-alkyl-1,2-disubstituted 3-buten-1-ol and (Z)-4-alkyl-4-silyl-1,2-disubstituted 3-buten-1-ol derivatives as single geometric isomers.
- Ahmed, Mahmood,Barrett, Anthony G. M.,Beall, Jennifer C.,Braddock, D. Christopher,Flack, Kevin,Gibson, Vernon C.,Procopiou, Panayiotis A.,Salter, Matthew M.
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p. 3219 - 3232
(2007/10/03)
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- Bromide assisted addition of hydrogen bromide to alkynes and allenes
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The addition of 0.1 M quaternary ammonium bromide to a solution of 20% trifluoroacetic acid in methylene chloride causes a large rate increase in the reaction of non-conjugated alkynes. The initial vinyl bromide product reacts further to provide a mixture of isomeric vinyl bromides and dibromides. At high salt concentrations however, the secondary reactions are prevented and only the initial vinyl bromide is found. In contrast to the corresponding addition to alkenes, the predominant mechanism is proposed to involve a one-step, concerted, nucleophilic attack by halide ion upon an acid-alkyne π-complex which produces the vinyl halide directly. A minor path involving syn addition is also seen. At all salt concentrations, allenes produce significant amounts of rearrangement products suggesting the significant involvement of a cationic mechanism.
- Weiss, Hilton M.,Touchette, Kim M.
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p. 1523 - 1528
(2007/10/03)
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- DIOLS AS EFFECTIVE COCATALYSTS IN THE PHASE TRANSFER CATALYZED PREPARATION OF 1-ALKYNES FROM 1,2-DIHALIDES
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Bis-tertiary diols accelerate bis-eliminations of HX from 1,2-dihalides in the presence of an onium salt as phase transfer catalyst and potassium hydroxyde as base.PEG 400 catalyzes the same elimination, but isomerizations from 1-alkyne to mixtures with the 2-alkyne and the 1,2-diene occur easily.
- Dehmlow, Eckehard V.,Thieser, Rainer,Sasson, Yoel,Neumann, Ronny
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p. 3569 - 3574
(2007/10/02)
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- Polyfunctionalized N-Tensides. VII. Substitution and Elimination in the Reaction of 1,2-Dihalogenoalkanes with Amines
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1,2-Dichloroalkanes, 1,2-Dibromoalkanes and mixtures of 1-bromo-2-chloroalkanes and 1-chloro-2-bromoalkanes react with primary or secondary amines and give both elimination and substitution products, often in a nearly 1:1 proportion.The elimination products are the cis and trans-1-halo-1-alkenes, the 2-halo-1-alkenes, the 1,3- and 2,4-dienes and the 1-alkenes.The main substitution products are the 1,2-bis-aminoalkanes.Physical dates, 1H-n.m.r.-spectra,surface tension values and CMC-dates are given.
- Beger, J.,Meerbote, E.
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- POLY(STYRYLMETHYLTHIOL) AS AN EFFICIENT DEBROMINATING REAGENT OF 1,2-DIBROMIDES
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Dibromides are readily debrominated by means of poly(styrylmethyl thiolate) with formation of the respective olefins.The polymeric reagent with a high content of sulphhydryl groups can be easily prepared from chloromethylated polystyrene; it extends possibilities of protection-deprotection reactions of the double bond.
- Janout, Vaclav,Cefelin, Pavel
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p. 3913 - 3916
(2007/10/02)
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- ORGANIC SYNTHESIS USING HALOBORATION REACTION. I. A SIMPLE AND SELECTIVE SYNTHESIS OF 2-BROMO- AND 2-IODO-1-ALKENES
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B-bromo- or B-iodo-9-borabicyclononane reacts readily with 1-alkynes.Such haloboration reactions proceed through the Markovnikov addition of the X-B moiety to CC bonds and cis fashion.The bromoboration reaction occours chemoselectively at terminal CC bonds but not at internal CC, terminal and internal C=C bonds.The protonolysis of haloboration products with acetic acid gives corresponding 2-bromo- or 2-iodo-1-alkenes in excellent yields.
- Hara, Shoji,Dojo, Hidetaka,Takinami, Satoru,Suzuki, Akira
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p. 731 - 734
(2007/10/02)
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- Application of Phase Transfer Catalysis, 14.- Preparation of Alkynes from Halides with Solid Potassium tert-Butoxide and Crown Ether
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Preparatively very simple and mild HX eliminations with solid potassium tert-butoxide in petroleum ether in the presence of catalytic amounts of crown-6 are described. 1,2-Dihalides (from alkenes) and 1,1-dihalides (from aldehydes) yield 1-alkynes; internal geminal dihalides (from symmetric ketones) give internal alkynes in excellent yields. 2,2-Dihalides (from methyl ketones) yield homogeneous 1-alkynes only if the 3-position is blocked. (E)-Haloalkenes lead also to alkynes in a syn-elimination process.
- Dehmlow, Eckehard V.,Lissel, Manfred
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