- Selective Isomerization of Terminal Alkenes to (Z)-2-Alkenes Catalyzed by an Air-Stable Molybdenum(0) Complex
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Positional and stereochemical selectivity in the isomerization of terminal alkenes to internal alkenes is observed using the cis-Mo(CO)4(PPh3)2 precatalyst. A p-toluenesulfonic acid (TsOH) cocatalyst is essential for catalyst activity. Various functionalized terminal alkenes have been converted to the corresponding 2-alkenes, generally favoring the Z isomer with selectivity as high as 8:1 Z:E at high conversion. Interrogation of the catalyst initiation mechanism by 31P NMR reveals that cis-Mo(CO)4(PPh3)2 reacts with TsOH at elevated temperatures to yield a phosphine-ligated Mo hydride (MoH) species. Catalysis may proceed via 2,1-insertion of a terminal alkene into a MoH group and stereoselective β-hydride elimination to yield the (Z)-2-alkene.
- Becica, Joseph,Glaze, Owen D.,Wozniak, Derek I.,Dobereiner, Graham E.
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p. 482 - 490
(2018/02/17)
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- PROCESS FOR THE CHEMOSELECTIVE REDUCTION OF TERMINALLY SATURATED CARBOXYLIC ESTERS
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The chemoselective reduction of a carboxylic ester (I) to an alcohol by catalytic hydrogenation, in particular in the presence of a transition metal complex, more particularly in the presence of a ruthenium (II) complex is described.
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Paragraph 0066; 0067
(2015/06/10)
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- Selective reduction of dienes/polyenes using sodium borohydride/catalytic ruthenium(III) in various liquid amide aqueous mixtures
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An efficient method to effect selective reduction of several structurally diverse dienes and an unsymmetrical triene is reported. The reduction is facile at 0 °C in a liquid amide aqueous solution containing sodium borohydride in the presence of 15 mol % ruthenium(III) chloride. The chemoselectivity of the reaction is controlled by proper choice of the liquid amide solvent.
- Babler, James H.,Ziemke, David W.,Hamer, Robert M.
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p. 1754 - 1757
(2013/04/10)
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- PROCESS FOR THE CHEMOSELECTIVE REDUCTION OF TERMINALLY SATURATED CARBOXYLIC ESTERS
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The chemoselective reduction of a carboxylic ester (I) to an alcohol by catalytic hydrogenation, in particular in the presence of a transition metal complex, more particularly in the presence of a ruthenium (II) complex is described.
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Page/Page column 11; 12
(2013/12/03)
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- New selectivities from old catalysts. Occlusion of Grubbs' catalysts in PDMS to change their reactions
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This article describes new selectivities for Grubbs' first and second generation catalysts when occluded in a hydrophobic matrix of polydimethylsiloxane (PDMS). Occlusion of catalysts in mm-sized slabs of PDMS is accomplished by swelling with methylene chloride then removing the solvent under vacuum. The catalysts are homogenously dissolved in PDMS yet remain catalytically active. Many substrates that react by olefin metathesis with Grubbs' catalysts freely dissolved in methylene chloride also react by olefin isomerization with occluded catalysts. Eleven examples of substrates that exhibit dual reactivity by undergoing olefin isomerization with occluded catalysts and olefin metathesis with catalysts dissolved in methylene chloride are reported. Most of these substrates have olefins with allylic phosphine oxides, carbonyls, or ethers. Control experiments demonstrate that isomerization is occurring in the solvent by decomposition of the catalyst from a ruthenium carbene to a proposed ruthenium hydride. This work was extended by heating occluded Grubbs' first generation catalyst to 100 °C in 90% MeOH in H2O in the presence of various alkenes to transform the Grubbs' catalyst into an isomerization catalyst for unfunctionalized olefins. This work demonstrates that occlusion of organometallic catalysts in PDMS has important implications for their reactions and can be used as a method to control which reactions they catalyze.
- Brett Runge,Mwangi, Martin T.,Bowden, Ned B.
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p. 5278 - 5288
(2007/10/03)
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- A Simple, Mild Elimination of Hydrogen Halide from Primary Alkyl Bromides and Iodides
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Addition of a solution of a primary alkyl bromide or iodide and 1,8-diazabicycloundec-7-ene in tetrahydrofuran (THF) to a solution prepared from dichlorobis(triphenylphosphine)nickel, triphenylphosphine, and n-butyl-lithium in THF results in an elimination at room temperature to give, in most cases, the terminal alkene.
- Jeropoulos, Sotiris,Smith, Edward H.
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p. 1621 - 1622
(2007/10/02)
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