7433-78-5Relevant articles and documents
Mechanistic study of the rhodium(I)-catalyzed hydroboration reaction
Evans, David A.,Fu, Gregory C.,Anderson, Benjamin A.
, p. 6679 - 6685 (1992)
The objective of this study has been to elucidate the mechanism of the rhodium(I)-catalyzed hydroboration process. Evidence that the reaction proceeds through a multistep pathway analogous to that of transition metal catalyzed olefin hydrogenation is presented. Deuterium labeling experiments reveal reversible elementary steps in the catalytic cycle; the level of reversibility is found to be substrate-dependent. Catalyst contamination through contact with adventitious oxidants has a pronounced effect on the reaction and appears to be the source of reported disparities involving product regioselection and deuterium labeling experiments.
Phenylthioacetylene as a Source of Stereodefined Trisubstituted Alkenes
Creton, Isabelle,Marek, Ilane,Brasseur, Denis,Jestin, Jean-Luc,Normant, Jean-F.
, p. 6873 - 6876 (1994)
A 1,2-metal-ate rearrangement leads to stereodefined trisubstituted alkenes, as single isomers, in an easy and straightforward one-pot procedure.
A simple and efficientin situgenerated copper nanocatalyst for stereoselective semihydrogenation of alkynes
Park, Byoung Yong,Lim, Taeho,Han, Min Su
supporting information, p. 6891 - 6894 (2021/07/19)
Development of a simple, effective, and practical method for (Z)-selective semihydrogenation of alkynes has been considered necessary for easy-to-access applications at organic laboratory scales. Herein, (Z)-selective semihydrogenation of alkynes was achieved using a copper nanocatalyst which was generatedin situsimply by adding ammonia borane to an ethanol solution of copper sulfate. Different types of alkynes including aryl-aryl, aryl-alkyl, and aliphatic alkynes were selectively reduced to (Z)-alkenes affording up to 99% isolated yield. The semihydrogenation of terminal alkynes to alkenes and gram-scale applications were also reported. In addition to eliminating catalyst preparation, the proposed approach is simple and practical and serves as a suitable alternative method to the conventional Lindlar catalyst.
Dinuclear cobalt complex-catalyzed stereodivergent semireduction of alkynes: Switchable selectivities controlled by H2O
Chen, Ke,Zhu, Hongdan,Li, Yuling,Peng, Qian,Guo, Yinlong,Wang, Xiaoming
, p. 13696 - 13705 (2021/11/16)
Catalytic semireduction of internal alkynes to alkenes is very important for organic synthesis. Although great success has been achieved in this area, switchable Z/E stereoselectivity based on a single catalyst for the semireduction of internal alkynes is a longstanding challenge due to the multichemo- and stereoselectivity, especially based on less-expensive earth-abundant metals. Herein, we describe a switchable semireduction of alkynes to (Z)- or (E)-alkenes catalyzed by a dinuclear cobalt complex supported by a macrocyclic bis pyridyl diimine (PDI) ligand. It was found that cis-reduction of the alkyne occurs first and the Z-E alkene stereoisomerization process is formally controlled by the amount of H2O, since the concentration of H2O may influence the catalytic activity of the catalyst for isomerization. Therefore, this protocol provides a facile way to switch to either the (Z)- or (E)-olefin isomer in a single transformation by adjusting the amount of water.
SYNTHESIS OF PHEROMONE DERIVATIVES VIA Z-SELECTIVE OLEFIN METATHESIS
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Paragraph 0222; 0232, (2021/12/28)
Disclosed herein are methods for synthesizing fatty olefin metathesis products of high Z-isomeric purity from olefin feedstocks of low Z-isomeric purity. The methods include contacting a contacting an olefin metathesis reaction partner, such as acylated alkenol or an alkenal acetal, with an internal olefin in the presence of a Z-selective metathesis catalyst to form the fatty olefin metathesis product. In various embodiments, the fatty olefin metathesis products are insect pheromones. Pheromone compositions and methods of using them are also described.
Enantiopure 2,9-Dideuterodecane – Preparation and Proof of Enantiopurity
Christoffers, Jens,Eru?ar, Gülsera,Fsadni, Miriam H.,Golding, Bernard T.,Mitschke, Nico,Roberts, Amy R.,Sadeghi, Majid M.,Wilkes, Heinz
, p. 3854 - 3863 (2021/08/24)
(R,R)- and (S,S)-(2,9-2H2)-n-Decane were prepared regio- and stereospecifically in 25–26 % yield over five steps from commercially available enantiopure (R)- and (S)-propylene oxide, respectively. The synthetic procedure involved nucleophilic displacement of (R)- and (S)-4-toluenesulfonic acid 1-methyl-4-pentenyl ester with LiAlD4 to furnish the respective (5-2H)-1-hexenes. Subsequent olefin metathesis and reduction of the double bond furnished the title compounds. The optical purity of (R,R)- and (S,S)-(2,9-2H2)-n-decane could not be determined by chromatography or polarimetry. Therefore, (R,R)- and (R,S)-(5-2H)-3-hydroxy-2-hexanone were prepared from their respective hexenes by Wacker oxidation, followed by enantioselective α-hydroxylation. The enantiopurity could then be determined by NMR spectroscopy because the stereospecifically deuterated hydroxyketones showed separated signals for the subterminal carbon atom (C-5) in the 13C NMR spectrum.
Cationic Tungsten Imido Alkylidene N-Heterocyclic Carbene Complexes That Contain Bulky Ligands
Buchmeiser, Michael R.,Frey, Wolfgang,Musso, Janis V.,Schowner, Roman
, p. 3145 - 3157 (2021/09/30)
Neutral and cationic tungsten imido alkylidene complexes of the general formulas W(NtBu)(CHR1)(OR2)Cl(NHC), W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl2(NHC), [W(NtBu)(CHR1)(OR2)(NHC)][B(ArF)4] and [W(N-2,6-bis(2,4,6-tri-iPr-C6H4)phenyl)(CHR1)Cl(NHC)][B(ArF)4] (R1= CMe3, CMe2Ph; R2= sterically demanding alkoxide; B(ArF)4= tetrakis(3,5-(CF3)2-C6H3)borate; NHC = N-heterocyclic carbene) were prepared. Two electronically different NHCs, namely 1,3-dimethylimidazol-2-ylidene (IMe) and 1,3-dimethyl-4,5-dichloroimidazol-2-ylidene (IMeCl), as well as a variety of terphenolates and a chiral biphenolate were employed.Z-selective homometathesis (HM) of unfunctionalized olefins was achieved with a selectivity of up to 90% and decent turnover numbers (TON) of up to 480 in the HM of 1-dodecene. Additionally, the reactivity of the cationic tungstentert-butylimido complexes in the reaction with vinyltrimethylsilane and ethylene was investigated, which yielded the corresponding silyl-alkylidene complex and, for the first time, a fully characterized cationic tungsten(IV) NHC ethylene complex.
Synthesis and Immobilization of Metal Nanoparticles Using Photoactive Polymer-Decorated Zeolite L Crystals and Their Application in Catalysis
Wissing, Maren,Niehues, Maximilian,Ravoo, Bart Jan,Studer, Armido
supporting information, p. 2245 - 2253 (2020/05/05)
A facile route to generate Au and Pd nanoparticles (NPs) on zeolite L crystals decorated with photoactive polymer brushes is described. The polymers used in this approach serve a dual role: Upon irradiation with UV light, they release highly reducing ketyl radicals in a Norrish-Type-I reaction. These radicals serve as one electron donors to reduce metal salts to the corresponding metal NPs. At the same time the polymer shell stabilizes the in situ generated metal NPs. It is shown that the zeolite-polymer-NP composites can be used as recyclable catalysts for the oxidation of benzylic alcohols to aldehydes and the stereoselective semihydrogenation of alkynes to Z-alkenes. The polymer shell in these hybrid catalysts protects the NPs from aggregation and also alters their catalytic properties. (Figure presented.).
Palladium nanoparticles stabilized by novel choline-based ionic liquids in glycerol applied in hydrogenation reactions
Garg, Garima,Foltran, Stéphanie,Favier, Isabelle,Pla, Daniel,Medina-González, Yaocihuatl,Gómez, Montserrat
, p. 69 - 75 (2019/02/16)
Palladium nanoparticles stabilized by choline-based ionic liquids in glycerol were prepared from Pd(II) precursors by simply heating at 80 °C under argon; in this process, the water present in the ionic liquid was found to be responsible for the reduction of Pd(II) into zero-valent palladium species. Palladium nanoparticles were fully characterized in both liquid phase and solid state. The as-prepared metal nanoparticles exhibited remarkable catalytic activity in hydrogenation processes for a significant variety of functional groups (alkenes, alkynes, nitro derivatives, benzaldehydes, aromatic ketones).
Aqueous phase semihydrogenation of alkynes over Ni-Fe bimetallic catalysts
Awasthi, Mahendra K.,Barman, Sudipta Roy,Behrens, Silke,Rai, Rohit K.,Singh, Sanjay K.,Singh, Vipin K.
, p. 4968 - 4980 (2020/08/19)
Bimetallic Ni-Fe catalysts (Ni/Fe, 1?:?1, 1?:?3, and 3?:?1) are synthesized and explored for their catalytic activity in semihydrogenation of internal alkynes using H2 gas in water-ethanol solution. Our findings revealed that over the Ni1Fe3 catalyst a high diastereoselectivity for Z-alkenes with a high conversion for a wide range of internal alkynes can be achieved at moderate reaction temperature (40 °C). Notably, the selectivity for the Z-alkenes is enhanced in the presence of n-butyl amine as an additive. Deuterium labeling experiments evidenced that H2 gas becomes dissociated homolytically over the catalyst surface to hydrogenate alkynes to alkenes. Synthesized catalysts were successfully characterized by HR-TEM, SEM, XPS, EDS, P-XRD and H2-TPD.
