7642-09-3Relevant academic research and scientific papers
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.
Allylnickel(II) complexes of bulky 5-substituted-2-iminopyrrolyl ligands
Cruz, Tiago F. C.,Gomes, Pedro T.,Lopes, Patrícia S.
, (2021/08/05)
The optimized reaction between [Ni(COD)2] (COD = 1,5-cyclooctadiene) and ligand precursor 5-(2,4,6-triisopropylphenyl)-2-[N-(2,6-diisopropylphenyl)-formimino]-1H-pyrrole yielded the η3-cyclooctenyl-Ni(II) complex [Ni{κ2N,N’-5-(2,4,6-iPr3C6H2)-NC4H2-2-C(H) = N(2,6-iPr2C6H3)}(η3-C8H13)] 1. Subsequently, the η3-allyl complexes [Ni{κ2N,N’-5-R-NC4H2-2-C(H)=N(2,6-iPr2C6H3)}(η3-C3H5)] (R = 3,5-(CF3)2C6H3 (2a), 2,6-Me2C6H3 (2b), 2,4,6-iPr3C6H2 (2c) and CPh3 (2d)) were prepared in good yields via metathesis of [Ni(η3-C3H5)(μ-Br)]2 with the respective potassium 5-R-2-[N-(2,6-diisopropylphenyl)formimino]pyrrolyl salt (KLa-d). Complexes 1 and 2a-d were characterized by NMR spectroscopy, elemental analysis and complex 2d further analyzed by single crystal X-ray diffraction. Addition of excess pyridine to solutions of complexes 2a-d led to the observation of a fluxional process that, according to VT-NMR experiments, corresponds to a pyridine-assisted cis–trans isomerization process occurring in these complexes, via a η3-η1-η3 haptotropic shift of the allyl ligand, with ΔG? values in range of 9.5–17.3 kcal mol?1. Additionally, complexes 2a-d, when activated by B(C6F5)3, slowly catalyzed the isomerization of hex-1-ene to mixtures of internal olefins.
Mechanism of Z-Selective Hydroalkylation of Terminal Alkynes
Lalic, Gojko,Lee, Mitchell T.
supporting information, p. 16663 - 16672 (2021/10/21)
This paper describes a detailed mechanistic study of the silver-catalyzed Z-selective hydroalkylation of terminal alkynes. Considering the established mechanistic paradigms for Z-selective hydroalkylation of alkynes, we explored a mechanism based on the radical carbometalation of alkynes. Experimental results have provided strong evidence against the initially proposed radical mechanism and have led us to propose a new mechanism for the Z-selective hydroalkylation of alkynes based on boronate formation and a 1,2-metalate shift. The new mechanism provides a rationale for the excellent Z-selectivity observed in the reaction. A series of stoichiometric experiments has probed the feasibility of the proposed elementary steps and revealed an additional role of the silver catalyst in the protodeboration of an intermediate. Finally, a series of kinetic measurements, KIE experiments, and competition experiments allowed us to identify the turnover limiting step and the resting state of the catalyst. We believe that the results of this study will be useful in the further exploration and development of related transformations of alkynes.
Bis(phosphine)hydridorhodacarborane Derivatives of 1,1′-Bis(ortho-carborane) and Their Catalysis of Alkene Isomerization and the Hydrosilylation of Acetophenone
Chan, Antony P. Y.,Parkinson, John A.,Rosair, Georgina M.,Welch, Alan J.
supporting information, (2020/02/04)
Deprotonation of [7-(1′-closo-1′,2′-C2B10H11)-nido-7,8-C2B9H11]- and reaction with [Rh(PPh3)3Cl] results in isomerization of the metalated cage and the formation of [8-(1′-closo-1′,2′-C2B10H11)-2-H-2,2-(PPh3)2-closo-2,1,8-RhC2B9H10] (1). Similarly, deprotonation/metalation of [8′-(7-nido-7,8-C2B9H11)-2′-(p-cymene)-closo-2′,1′,8′-RuC2B9H10]- and [8′-(7-nido-7,8-C2B9H11)-2′-Cp*-closo-2′,1′,8′-CoC2B9H10]- affords [8-{8′-2′-(p-cymene)-closo-2′,1′,8′-RuC2B9H10}-2-H-2,2-(PPh3)2-closo-2,1,8-RhC2B9H10] (2) and [8-(8′-2′-Cp*-closo-2′,1′,8′-CoC2B9H10)-2-H-2,2-(PPh3)2-closo-2,1,8-RhC2B9H10] (3), respectively, as diastereoisomeric mixtures. The performances of compounds 1-3 as catalysts in the isomerization of 1-hexene and in the hydrosilylation of acetophenone are compared with those of the known single-cage species [3-H-3,3-(PPh3)2-closo-3,1,2-RhC2B9H11] (I) and [2-H-2,2-(PPh3)2-closo-2,1,12-RhC2B9H11] (V), the last two compounds also being the subjects of 103Rh NMR spectroscopic studies, the first such investigations of rhodacarboranes. In alkene isomerization all the 2,1,8-or 2,1,12-RhC2B9 species (1-3, V) outperform the 3,1,2-RhC2B9 compound I, while for hydrosilylation the single-cage compounds I and V are better catalysts than the double-cage species 1-3.
Monohydride-Dichloro Rhodium(III) Complexes with Chiral Diphosphine Ligands as Catalysts for Asymmetric Hydrogenation of Olefinic Substrates
Higashida, Kosuke,Brüning, Fabian,Tsujimoto, Nagataka,Higashihara, Kenya,Nagae, Haruki,Togni, Antonio,Mashima, Kazushi
, p. 8749 - 8759 (2020/07/04)
We report full details of the synthesis and characterization of monohydride-dichloro rhodium(III) complexes bearing chiral diphosphine ligands, such as (S)-BINAP, (S)-DM-SEGPHOS, and (S)-DTBM-SEGPHOS, producing cationic triply chloride bridged dinuclear rhodium(III) complexes (1 a: (S)-BINAP; 1 b: (S)-DM-SEGPHOS) and a neutral mononuclear monohydride-dichloro rhodium(III) complex (1 c: (S)-DTBM-SEGPHOS) in high yield and high purity. Their solid state structure and solution behavior were determined by crystallographic studies as well as full spectral data, including DOSY NMR spectroscopy. Among these three complexes, 1 c has a rigid pocket surrounded by two chloride atoms bound to the rhodium atom together with one tBu group of (S)-DTBM-SEGPHOS for fitting to simple olefins without any coordinating functional groups. Complex 1 c exhibited superior catalytic activity and enantioselectivity for asymmetric hydrogenation of exo-olefins and olefinic substrates. The catalytic activity of 1 c was compared with that of well-demonstrated dihydride species derived in situ from rhodium(I) precursors such as [Rh(cod)Cl]2 and [Rh(cod)2]+[BF4]? upon mixing with (S)-DTBM-SEGPHOS under dihydrogen.
Novel nickel nanoparticles stabilized by imidazolium-amidinate ligands for selective hydrogenation of alkynes
López-Vinasco, Angela M.,Martínez-Prieto, Luis M.,Asensio, Juan M.,Lecante, Pierre,Chaudret, Bruno,Cámpora, Juan,Van Leeuwen, Piet W. N. M.
, p. 342 - 350 (2020/02/04)
The main challenge in the hydrogenation of alkynes into (E)- or (Z)-alkenes is to control the selective formation of the alkene, avoiding the over-reduction to the corresponding alkane. In addition, the preparation of recoverable and reusable catalysts is of high interest. In this work, we report novel nickel nanoparticles (Ni NPs) stabilized by three different imidazolium-amidinate ligands (ICy·(Ar)NCN; L1: Ar = p-tol, L2: Ar = p-anisyl and L3: Ar = p-ClC6H4). The as-prepared Ni NPs were fully characterized by (HR)-TEM, XRD, WASX, XPS and VSM. The nanocatalysts are active in the hydrogenation of various substrates. They present a remarkable selectivity in the hydrogenation of alkynes towards (Z)-alkenes, particularly in the hydrogenation of 3-hexyne into (Z)-3-hexene under mild reaction conditions (room temperature, 3% mol Ni and 1 bar H2). The catalytic behaviour of Ni NPs was influenced by the electron donor/acceptor groups (-Me, -OMe, -Cl) in the N-aryl substituents of the amidinate moiety of the ligands. Due to the magnetic character of the Ni NPs, recycling experiments were successfully performed after decantation in the presence of an external magnet, which allowed us to recover and reuse these catalysts at least 3 times preserving both activity and chemoselectivity.
Potassium Yttrium Ate Complexes: Synergistic Effect Enabled Reversible H2 Activation and Catalytic Hydrogenation
Zhai, Dan-Dan,Du, Hui-Zhen,Zhang, Xiang-Yu,Liu, Yu-Feng,Guan, Bing-Tao
, p. 8766 - 8771 (2019/09/30)
A potassium yttrium benzyl ate complex was generated simply by mixing an yttrium amide and potassium benzyl. The benzyl ate complex could undergo peripheral deprotonation to produce a cyclometalated complex or hydrogenation to give a hydride ate complex. The latter hydride ate complex features a (KH)2 structure protected by two yttrium amide complexes. The synergistic effect between potassium hydride and the amide ligand enables the complex to deprotonate a methyl C-H bond. The combination of intramolecular deprotonation of the hydride ate complex and hydrogenation of the cyclometalated complex constitutes a reversible H2 activation process. Using this process involving formal addition and elimination of H2, we accomplished the catalytic hydrogenation of alkenes, alkynes, and imines.
Selective hydrothermal reductions using geomimicry
Bockisch, Christiana,Lorance, Edward D.,Shaver, Garrett,Williams, Lynda B.,Hartnett, Hilairy E.,Shock, Everett L.,Gould, Ian R.
, p. 4159 - 4168 (2019/08/07)
Reduction of carbon-carbon π-bonds has been demonstrated using iron powder as the reductant and simple powdered nickel as the catalyst in water as the solvent at 250 °C and the saturated water vapor pressure, 40 bars. Stereochemical, kinetic and electronic probes of the mechanism suggest reaction via a conventional Horiuti-Polyani process for hydrogenation at the nickel metal surface. Selective reduction of carbon-carbon π-bonds is observed in the presence of other functional groups. The reactions use benign and Earth-abundant reagents that are at low depletion risk and take place in water as the only solvent under conditions that are characteristic of many geochemical processes.
Chain Multiplication of Fatty Acids to Precise Telechelic Polyethylene
Witt, Timo,H?u?ler, Manuel,Kulpa, Stefanie,Mecking, Stefan
supporting information, p. 7589 - 7594 (2017/06/13)
Starting from common monounsaturated fatty acids, a strategy is revealed that provides ultra-long aliphatic α,ω-difunctional building blocks by a sequence of two scalable catalytic steps that virtually double the chain length of the starting materials. The central double bond of the α,ω-dicarboxylic fatty acid self-metathesis products is shifted selectively to the statistically much-disfavored α,β-position in a catalytic dynamic isomerizing crystallization approach. “Chain doubling” by a subsequent catalytic olefin metathesis step, which overcomes the low reactivity of this substrates by using waste internal olefins as recyclable co-reagents, yields ultra-long-chain α,ω-difunctional building blocks of a precise chain length, as demonstrated up to a C48 chain. The unique nature of these structures is reflected by unrivaled melting points (Tm=120 °C) of aliphatic polyesters generated from these telechelic monomers, and by their self-assembly to polyethylene-like single crystals.
Development of silica-supported frustrated Lewis pairs: Highly active transition metal-free catalysts for the Z-selective reduction of alkynes
Szeto, Kai C.,Sahyoun, Wissam,Merle, Nicolas,Castelbou, Jessica Llop,Popoff, Nicolas,Lefebvre, Frédéric,Raynaud, Jean,Godard, Cyril,Claver, Carmen,Delevoye, Laurent,Gauvin, Régis M.,Taoufik, Mostafa
, p. 882 - 889 (2016/02/18)
Supported Lewis acid/base systems based on a triphenyl phosphine fragment and Piers' reagent (HB(C6F5)2) or BArF have been prepared and characterized. Both materials show unprecedented catalytic activity in the Z-selective hydrogenation of 3-hexyne to Z-3-hexene with a selectivity up to 87%. Other alkynes can also be hydrogenated Z-selectively, albeit with moderate yields. The activity of the supported phosphine/HB(C6F5)2 adduct is similar to the only homogeneous example reported thus far based on bridged B/N frustrated Lewis pairs under high hydrogen pressure. Importantly, this transition metal-free supported catalyst was recycled five times in the challenging selective hydrogenation of a non-polar unactivated alkyne.
