19398-88-0Relevant articles and documents
Catalytic, oxidant-free, direct olefination of alcohols using Wittig reagents
Khaskin,Milstein
supporting information, p. 9002 - 9005 (2015/05/27)
Reported here is the catalytic, acceptorless coupling of alcohols with in situ generated, non-stabilized phosphonium ylides to form olefins as major products. The reaction uses low catalyst loadings and does not require added oxidants. Hydrogenation of the product is minimized and the reaction leads to Z (aliphatic) or E (benzylic) stereospecificity.
Decene formation in ethylene trimerization reaction catalyzed by Cr-pyrrole system
Zilbershtein, Timur M.,Kardash, Vladislav A.,Suvorova, Vladlena V.,Golovko, Anatoly K.
, p. 371 - 378 (2014/03/21)
Decene formation in the ethylene trimerization reaction was studied using a chromium(III) 2-ethylhexanoate/2,5-dimethylpyrrole/triethylaluminum/ diethylaluminum chloride catalyst system. Kinetic investigations revealed that some decene formation reactions did not depend on 1-hexene concentration, because 1-hexene and catalyst may react with ethylene before dissociation of 1-hexene-catalyst complex after 1-hexene formation. The results demonstrated that decene formation is an intrinsic part of the trimerization reaction mechanism. It was also shown that a stepwise elimination mechanism for the decomposition of the chromacycloheptane intermediate cannot explain the observed product distribution. The dependencies found allow selection of appropriate conditions for low or high decene formation in the ethylene trimerization reaction.
Selective semihydrogenation of alkynes on shape-controlled palladium nanocrystals
Chung, Jooyoung,Kim, Chanhoi,Jeong, Hansaem,Yu, Taekyung,Binh, Do Huy,Jang, Jyongsik,Lee, Jaichan,Kim, B. Moon,Lim, Byungkwon
, p. 919 - 925 (2013/08/25)
A systematic study on the selective semihydrogenation of alkynes to alkenes on shape-controlled palladium (Pd) nanocrystals was performed. Pd nanocrystals with a cubic shape and thus exposed {100} facets were synthesized in an aqueous solution through the reduction of Na2PdCl4 with L-ascorbic acid in the presence of bromide ions. The Pd nanocubes were tested as catalysts for the semihydrogenation of various alkynes such as 5-decyne, 2-butyne-1,4-diol, and phenylacetylene. For all substrates, the Pd nanocubes exhibited higher alkene selectivity (>90 %) than a commercial Pd/C catalyst (75-90 %), which was attributed to a large adsorption energy of the carbon-carbon triple bond on the {100} facets of the Pd nanocubes. Our approach based on the shape control of Pd nanocrystals offers a simple and effective route to the development of a highly selective catalyst for alkyne semihydrogenation. Catalysis3: The semihydrogenation of various alkynes by Pd nanocubes was investigated. The nanocubes exhibited high alkene selectivity and complete cis-selectivity, thus surpassing the Lindlar catalyst. The shape control of Pd nanocrystals provides a simple and efficient way for generating highly selective catalysts for the semihydrogenation of alkynes.
Stabilization of long-chain intermediates in solution. octyl radicals and cations
Teodorovi?, Aleksandar V.,Badjuk, Dalibor M.,Stevanovi?, Nenad,Pavlovi?, Radoslav Z.
, p. 19 - 24 (2013/06/26)
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.
Effect of solvent and temperature on the lithium?bromine exchange of vinyl bromides: Reactions of n -butyllithium and t -butyllithium with (E)-5-bromo-5-decene
Bailey, William F.,Luderer, Mark R.,Uccello, Daniel P.,Bartelson, Ashley L.
experimental part, p. 2661 - 2666 (2010/08/19)
The outcome of reactions of (E)-5-bromo-5-decene (1), a representative vinyl bromide, with t-BuLi or n-BuLi at 0 °C and room temperature, respectively, in a variety of solvent systems has been investigated. Vinyl bromide 1 does not react with t-BuLi in pure heptane; however, the presence of even small quantities of an ether in a predominantly heptane medium resulted in virtually complete consumption of 1 at 0 °C, resulting in nearly the same distribution of products, including 60?80% of (Z)-5-decenyllithium, regardless of the solvent composition. Vinyl bromide 1 reacts slowly with n-BuLi at room temperature in a variety of ether and heptane-ether mixtures to afford a mixture of products including significant quantities of recovered starting material. The results of these experiments demonstrate that lithium?bromine exchange between a vinyl bromide and either t-BuLi or n-BuLi at temperatures significantly above ?78 °C is not an efficient method for the generation of a vinyllithium.
A selective Ru-catalyzed semireduction of alkynes to Z olefins under transfer-hydrogenation conditions
Belger, Christian,Neisius, N. Matthias,Plietker, Bernd
supporting information; experimental part, p. 12214 - 12220 (2011/03/17)
By using a readily available, air- and moisture-stable dihydrido-Ru complex, a variety of Z olefins are accessible under transfer-hydrogenation conditions with formic acid as the hydrogen source in excellent yields and Z/E selectivities. A discerning transformation: Z-Configured C=C bonds are stereoselectively formed from alkynes in the presence of a Ru catalyst with formic acid as the sole H2 source at room temperature (see scheme). A variety of functional groups are compatible with this novel procedure. Operational simplicity and the lack of overreduction products are characteristics for this unprecedented process.
TRANSITION METAL COMPLEXES
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Page/Page column 90-93, (2008/06/13)
A transition metal complex which is a bis-arylimine pyridine MXn complex, comprising a bis-arylimine pyridine ligand having the formula (I), wherein R1-R5, R7-R9, R12 and R14 are each, independently, hydrogen, optionally substituted hydrocarbyl, an inert functional group, or any two of R1-R3 and R7-R9 vicinal to one another taken together may form a ring, and R6 is hydrogen, optionally substituted hydrocarbyl, an inert functional group, or taken together with R7 or R4 to form a ring, R10 is hydrogen, optionally substituted hydrocarbyl, an inert functional group, or taken together with R9 or R4 to form a ring, R11 is hydrogen, optionally substituted hydrocarbyl, an inert functional group, or taken together with R12 or R5 to form a ring, R15 is hydrogen, optionally substituted hydrocarbyl, an inert functional group, or taken together with R14 or R5 to form a ring, provided that R13 and at least one of R12 and R14 are independently selected from optionally substituted C1-C30 alkyl, optionally substituted C4-C30 alkyloxy, halogen and optionally substituted C5-C20 aryl, or R13 taken together with R12 or R14 form a ring, or R12 taken together with R11 form a ring and R14 taken together with R15 form a ring, and provided that at least one of R12, R13 and R14 is optionally substituted C4-C30 alkyloxy; M is a transition metal atom in particular selected from Ti, V, Cr, Mn, Fe, Co, Ni, Pd, Rh, Ru, Mo, Nb, Zr, Hf, Ta, W, Re, Os, Ir or Pt; n matches the formal oxidation state of the transition metal atom M; and X is halide, optionally substituted hydrocarbyl, alkoxide, amide, or hydride. The transition metal complexes of the present invention, their complexes with non-coordinating anions and catalyst systems containing such complexes have good solubility in non-polar media and chemically inert non--polar solvents especially aromatic hydrocarbon solvents. The catalyst systems can be used for a wide range of (co-)oligomerization, polymerization and dimerization reactions.
Novel ortho-Alkoxy-Substituted Phosphorus Ylides and Their Stereoselectivity in Wittig Reactions
Jeganathan, Suruliappa,Tsukamoto, Masamitsu,Schlosser, Manfred
, p. 109 - 111 (2007/10/02)
The stereochemistry of the reactions between tris(2-methoxymethoxypheny)phosphonioethanide (1f), -butanide (2f), and -phenyl-methanide (3f) and a variety of aldehydes was investigated.Ylides having a β-unbranched aliphatic sidechain, such as 2f, and saturated straight-chain aldehydes give olefins with unprecedented cis-selectivity (cis/trans ca. 200:1).
Aspects of the hydrozirconation-isomerisation reaction
Annby, Ulf,Alvhaell, Joergen,Gronowitz, Salo,Hallberg, Anders
, p. 75 - 84 (2007/10/02)
Aspects of the hydrozirconation-isomerization of nonfunctionalised olefins are discussed.Cyclooctene and 1-methyl-1-cyclohexene were previously reported not to react with Cp2Zr(H)Cl.In the present work after treatment of the former with Cp2Zr(D)Cl, and subsequent hydrolysis, no cyclooctane could be detected.Although the olefin seemed not to have reacted, it was deduced that the corresponding cyclooctylzirconium was in fact formed, since the amount of deuterium incorporated in cyclooctane was roughly the same as the amount of zirconium deuteride used.Total scrambling of deuterium was observed.Cycloheptene and 2,2,11,11-tetramethyl-6-dodecene gave similar results. 1-Methyl-1-cyclohexene, on the other hand, was very unreactive.No evidence for deuterium incorporation in the recovered olefin (80-90percent) was obtained.When Z-5-decene was used as substrate, zirconium migration towards the terminal carbon, and cis-trans isomerisation, were slower than expected.No internal alkylzirconium derivatives could be trapped.Competing hydrogenation of 1-and Z-5-decene is favoured when a deficiency of the zirconium hydride is used.
DELVING INTO THE WITTIG REACTION - STEREOCHEMISTRY AND MECHANISM. STEREOCHEMICAL IDIOSYNCRASIES AND MECHANISTIC IMPLICATIONS
Maryanoff, Bruce E.,Reitz, Allen B.
, p. 167 - 190 (2007/10/02)
Non-stabilized triphenylphosphorus ylides bearing anionic groups can react with aldehydes to give alkene mixtures anomalously enriched in the E isomer .To explain this phenomenon, we sought to study both cis and trans oxaphosphetane (OP) intermediates at low temperature.The observation of both intermediates was achieved for the first time by the use of high-field H-1, P-31, and C-13 NMR spectroscopy in various instances.We have monitored some Wittig reactions in detail via NMR-based kinetic measurements of OP's and alkenes.In certain cases, OP's equilibrate, presumably by reaction reversal to aldehyde and ylide, to introduce a measure of thermodynamic control into the Wittig reaction.Thermodynamic control accounts for a large portion of the excess E stereoselectivity observed in going from a triphenyl to trialkyl (i.e., butyl) phosphorus ylide.Quenching experiments with HBr and the deprotonation of erythro and threo beta-hydroxyphosphonium salts are also discussed.Attempts to investigate reactions of stabilized and semi-stabilized ylides in an analogous manner were not fruitful.
