- Regioselective carbon-carbon bond formation in titanium mediated reaction of ethylmagnesium bromide with allylic alcohols and allylic ethers
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In the presence of Ti(Oi-Pr)4 reaction of EtMgBr with allylic alcohols and allylic ethers affords the products of formal SN2′ substitution of hydroxy or alkoxy groups with ethyl groups in moderate to good yields and excellent regiose
- Kulinkovich,Epstein,Isakov,Khmel'nitskaya
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- Tergal Gland Secretion of the Rove Beetle Aleochara pseudochrysorrhoa (Staphylinidae: Aleocharinae): Chemical Composition and Biological Roles
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Aleochara pseudochrysorrhoa has a glandular complex known as the tergal gland. Generally, the tergal gland secretion (TGS) has been described to have defensive function, but some reports point to a possible secondary function of this complex. For example, the TGS of the related species A. curtula has been demonstrated to possess an important role in intraspecies communication. In this work, we describe the chemical composition of the TGS of A. pseudochrysorrhoa males and females. Eleven compounds were identified based on GC/MS and GC-FT-IR analyses, retention indexes and derivatization products. Furthermore, a brief study regarding the biological function of the TGS in mating behavior is provided, in which the stimulation of male grasping response reaction by female TGS proved to be dependent on concentration.
- da Silva, Maycon R.,Vidal, Diogo M.,Figueiredo, Leonardo,Bandeira, Pamela T.,Bergmann, Jan,Zarbin, Paulo H. G.
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- OLEFIN METATHESIS CATALYSTS
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This invention relates generally to metathesis catalysts and the use of such catalysts in the metathesis of olefins and olefin compounds, more particularly, in the use of such catalysts in Z and E selective olefin metathesis reactions. The invention has utility in the fields of organometallics and organic synthesis.
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Page/Page column 83; 84; 85
(2017/07/06)
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- Fast-initiating, ruthenium-based catalysts for improved activity in highly E-selective cross metathesis
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Ruthenium-based olefin metathesis catalysts bearing dithiolate ligands have been recently employed to generate olefins with high E-selectivity (>99% E) but have been limited by low to moderate yields. In this report, 1H NMR studies reveal that a major contributing factor to this low activity is the extremely low initiation rates of these catalysts with trans olefins. Introducing a 2-isopropoxy-3-phenylbenzylidene ligand in place of the conventional 2-isopropoxybenzylidene ligand resulted in catalysts that initiate rapidly under reaction conditions. As a result, reactions were completed in significantly less time and delivered higher yields than those in previous reports while maintaining high stereoselectivity (>99% E).
- Ahmed, Tonia S.,Grubbs, Robert H.
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supporting information
p. 1532 - 1537
(2017/02/10)
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- High Trans Kinetic Selectivity in Ruthenium-Based Olefin Cross-Metathesis through Stereoretention
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The first kinetically controlled, highly trans-selective (>98%) olefin cross-metathesis reaction is demonstrated using Ru-based catalysts. Reactions with either trans or cis olefins afford products with highly trans or cis stereochemistry, respectively. This E-selective olefin cross-metathesis is shown to occur between two trans olefins and between a trans olefin and a terminal olefin. Additionally, new stereoretentive catalysts have been synthesized for improved reactivity. (Chemical Equation Presented).
- Johns, Adam M.,Ahmed, Tonia S.,Jackson, Bradford W.,Grubbs, Robert H.,Pederson, Richard L.
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supporting information
p. 772 - 775
(2016/03/01)
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- Stabilization of long-chain intermediates in solution. octyl radicals and cations
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The rearrangements of 1-octyl, 1-decyl and 1-tridecyl intermediates obtained from thermal lead(IV) acetate (LTA) decarboxylation of nonanoic, undecanoic and tetradecanoic acid were investigated experimentally through analysis and distribution of the products. The relationships between 1,5-, 1,6- and possibly existing 1,7-homolytic hydrogen transfer in 1-octyl-radical, as well as successive 1,2-hydride shift in corresponding cation have been computed via Monte-Carlo method. Taking into account that ratios of 1,5-/1,6-homolytic rearrangements in 1-octyl- and 1-tridecyl radical are approximately the same, the simulation shows very low involvement of 1,7-hydrogen rearrangement (1,5-/1,6-/1,7-hydrogen rearrangement = 85:31:1) in 1-octyl radical.
- Teodorovi?, Aleksandar V.,Badjuk, Dalibor M.,Stevanovi?, Nenad,Pavlovi?, Radoslav Z.
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- Treasures from the Free Radical Renaissance Period - Miscellaneous hexenyl radical kinetic data
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Rate constant data and Arrhenius parameters have been determined for a series of substituted hexenyl radicals of differing electronic and steric demand. Electron-withdrawing groups (CF3, CO2Et) directly attached to the radical centre slighly accelerate 5-exo ring-closure (k cis + ktrans ~ 2.1 × 105 s -1 at 25°) relative to donating groups (OMe; 1.6 × 10 5 s-1 at 25°). Sterically demanding groups (tert-Bu), as expected, slow the cyclization process (1 × 105 s -1). These observations are consistent with subtle changes in activation energy for 5-exo ring-closure. Interestingly, the nature of the solvent would appear to have a significant influence on this chemistry with the cis/trans stereoselectivity sometimes improved as the solvent polarity is increased. Except for the system containing the CF3 (electron-withdrawing) group which displays an increase in the cyclization/capture rate constant (kc/kH), a general decrease in the kc/kH ratio as solvent polarity is increased is noted; these changes have been speculated to arise mainly from changes in kH in the various solvents employed.
- Beckwith, Athelstan L. J.,Schiesser, Carl H.
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p. 1736 - 1743
(2011/05/03)
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- Synthesis and transformations of metallacycles 26. Cp2ZrCl2-catalyzed cycloalumination of substituted allenes with Et3Al
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Catalytic cycloalumination of 1-alkyl(phenyl)alleres with triethylaluminum (5 mol.% of Cp2ZrCl2 as the catalyst, -20 °C, 4 h, hexane) afforded methylene- and alkyl(benzyl)idene-substituted alumacyclopentanes.
- Khafizova,Ibragimov,Gil'fanova,Khalilov,Dzhemilev
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p. 2188 - 2192
(2007/10/03)
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- Substrate specificity of regiospecific desaturation of aliphatic compounds by a mutant Rhodococcus strain.
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Substrate specificity of cis-desaturation of alipahtic compounds by resting cells of a mutant, Rhodococcus sp. strain KSM-MT66, was examined. Among substrates tested, the rhodococcal cells were able to convert n-alkanes (C13-C19), 1-chloroalkanes (C16 and C18), ethyl fatty acids (C14-C17) and alkyl (C1-C4) esters of palmitic acid to their corresponding unsaturated products of cis configuration. The products from n-alkanes and 1-chloroalkanes had a double bond mainly at the 9th carbon from their terminal methyl groups, and the products from acyl fatty acids had a double bond mainly at the 6th carbon from their carbonyl carbons.
- Koike,Takaiwa,Kimura,Inoue,Ito
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p. 1064 - 1066
(2007/10/03)
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- Vinylic Organoboranes. 9. A General Stereospecific Synthesis of (Z)- and (E)-Disubstituted Alkenes via Organoboranes
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A general and stereospecific synthesis of (Z)-disubstituted alkenes using mono- and dihaloboranes is presented.The hydridation of dialkylhaloboranes in the presence of 1-alkynes provides the corresponding dialkylvinylboranes (1), representing the first general synthesis of such derivatives.Treatment with iodine in the presence of sodium methoxide induces the migration of one of the alkyl groups from boron to the adjacent carbon, followed by a rapid deiodoboronation to afford (Z)-disubstituted alkenes (2) in high yields.Similarly, the hydroboration of 1-alkynes with alkyl bromoboranes (R1BHBr*SMe2, 4) followed by iodination in the presence of sodium methoxide in methanol affords (Z)-disubstituted alkenes (2) in good yields.Both procedures constitute a general one-pot synthesis of (Z)- disubstituted alkenes from an alkene and 1-alkyne.A simple synthesis of Muscalure (7), the sex pheromone of the housefly (Musca domestica), is achieved in good yields.An alternative general stereospecific synthesis of (Z)- and (E)-disubstituted alkenes based on alkenylboronic esters is also described.
- Brown, Herbert C.,Basavaiah, Deevi,Kulkarni, Surendra U.,Bhat, Narayan G.,Prasad, J. V. N. Vara
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p. 239 - 246
(2007/10/02)
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- A General and Stereospecific Synthesis of Cis Alkenes via Stepwise Hydroboration: A Simple Synthesis of Muscalure, the Sex Pheromone of the Housefly (Musca domestica)
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Base-induced iodination of the vinylborane intermediates, conveniently obtained via hydroboration of 1-alkynes with alkylbromoboranes (RBHBr*SMe2) provides cis-disubstituted alkenes in good yields.Muscalure, the insect pheromone of the housefly (Musca domestica), has been prepared in 59percent yield.
- Brown, Herbert C.,Basavaiah, D.
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p. 3806 - 3808
(2007/10/02)
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