6380-21-8Relevant articles and documents
Ruthenium Removal Using Silica-Supported Aromatic Isocyanides
Gregg, Zackary R.,Glickert, Elise,Xu, Ruoshui,Diver, Steven T.
supporting information, (2021/05/13)
New silica gel scavengers containing aromatic isocyanides have been synthesized and evaluated for Ru removal. A thiol-ene click reaction was used to attach the isocyanide precursor to a thiol-containing siloxane. Conventional methods for grafting to silica gel at elevated temperature resulted in significant hydrolysis of the isocyanide. A novel cleavage reaction was developed to quantitate the amount of surface-loaded isocyanide. Binding by the new materials was comparatively evaluated for a variety or Ru carbene catalysts. The optimal conditions were extended to two ring-closing metatheses (RCM). The residual Ru was determined by inductively coupled plasma mass spectrometry (ICP-MS). For facile RCM reactions, the UV data agreed with the ICP-MS results. However, more difficult RCM did not correlate well with the UV data. This was interpreted in terms of varying extent of catalyst decomposition. In all cases, isocyanide scavenger reagents were found to be superior to commonly used, silica gel-based metal scavengers.
Bioinspired Selective Synthesis of Heterodimer 8-5′ or 8- O-4′ Neolignan Analogs
Dong, Kui,Zhao, Chuang-Yuan,Wang, Xiao-Ju,Wu, Li-Zhu,Liu, Qiang
supporting information, p. 2816 - 2820 (2021/04/13)
The bioinspired synthesis of heterodimer neolignan analogs is reported by single-electron oxidation of both alkenyl phenols and phenols individually, followed by a combination of the resultant radicals. This oxidative radical cross-coupling strategy can afford heterodimer 8-5′ or 8-O-4′ neolignan analogs selectively with the use of air as the terminal oxidant and copper acetate as the catalyst at room temperature.
Cascade Claisen and Meinwald Rearrangement for One-Pot Divergent Synthesis of Benzofurans and 2 H-Chromenes
Song, Liyan,Su, Qian,Lin, Xi,Du, Zhihui,Xu, Huiyou,Ouyang, Ming-An,Yao, Hongliang,Tong, Rongbiao
, p. 3004 - 3009 (2020/04/20)
A new cascade approach has been developed for the one-pot four-step divergent synthesis of polysubstituted benzofurans and 2H-chromenes, featuring a novel cascade aromatic Claisen rearrangement/Meinwald rearrangement/dehydrative or oxidative cyclization. This new method was demonstrated with 39 examples tolerating different substitutions at an epoxide, allylic ether, and aromatic ring, and we showcased its utility with the first total synthesis of natural product liparacid A in seven steps.
Hydrophilic (ν6-Arene)-Ruthenium(II) Complexes with P-OH ligands as catalysts for the isomerization of allylbenzenes and C-H bond arylation reactions in water
González-Fernández, Rebeca,Crochet, Pascale,Cadierno, Victorio
, p. 3696 - 3706 (2019/10/11)
Half-sandwich ruthenium(II) complexes containing ν6-coordinated 3-phenylpropanol and phosphinous-acid-type ligands, namely, [RuCl2(ν6-C6H5CH2CH2CH2OH){P(OH)R2}] (R = Me (2a), Ph (2b), 4-C6H4CF3 (2c), 4-C6H4OMe (2d), OMe (2e), OEt (2f), and OPh (2g), have been synthesized in 44-88% yield by reacting [RuCl2{ν6:κ1(O)-C6H5CH2CH2CH2OH}] (1) with the appropriate pentavalent phosphorus oxide R2P(═O)H. The structure of [RuCl2(ν6-C6H5CH2CH2CH2OH){P(OH)Me2}] (2a) was unequivocally confirmed by X-ray diffraction methods. Compounds 2a-g proved to be catalytically active in the isomerization of allylbenzenes into the corresponding (1-propenyl)benzene derivatives employing water as the sole reaction solvent, with [RuCl2(ν6-C6H5CH2CH2CH2OH){P(OH)(OPh)2}] (2g) showing the best performance and a broad substrate scope (73-93% isolated yields with E/Z ratios around 90:10 employing 1 mol % of 2g and 3 mol % of K2CO3, and performing the catalytic reactions at 80 °C for 4-24 h). The results herein presented show for the first time the utility of phosphinous acids as auxiliary ligands for metal-catalyzed olefin isomerization processes, reactions in which a cooperative role for the P - OH unit is proposed. On the other hand, the utility of complexes 2a-g as catalysts for ortho-arylation reactions of 2-phenylpyridine in water is also briefly discussed.
Selective Synthesis of Primary Anilines from NH3 and Cyclohexanones by Utilizing Preferential Adsorption of Styrene on the Pd Nanoparticle Surface
Koizumi, Yu,Jin, Xiongjie,Yatabe, Takafumi,Miyazaki, Ray,Hasegawa, Jun-ya,Nozaki, Kyoko,Mizuno, Noritaka,Yamaguchi, Kazuya
supporting information, p. 10893 - 10897 (2019/07/12)
Dehydrogenative aromatization is one of the attractive alternative methods for directly synthesizing primary anilines from NH3 and cyclohexanones. However, the selective synthesis of primary anilines is quite difficult because the desired primary aniline products and the cyclohexanone substrates readily undergo condensation affording the corresponding imines (i.e., N-cyclohexylidene-anilines), followed by hydrogenation to produce N-cyclohexylanilines as the major products. In this study, primary anilines were selectively synthesized in the presence of supported Pd nanoparticle catalysts (e.g., Pd/HAP, HAP=hydroxyapatite, Ca10(PO4)6(OH)2) by utilizing competitive adsorption unique to heterogeneous catalysis; in other words, when styrene was used as a hydrogen acceptor, which preferentially adsorbs on the Pd nanoparticle surface in the presence of N-cyclohexylidene-anilines, various structurally diverse primary anilines were selectively synthesized from readily accessible NH3 and cyclohexanones. The Pd/HAP catalyst was reused several times though its catalytic performance gradually declined.
Synthesis of Benzofuranones via Palladium-Catalyzed Intramolecular Alkoxycarbonylation of Alkenylphenols
Hirschbeck, Vera,Fleischer, Ivana
supporting information, p. 2854 - 2857 (2018/02/06)
Herein, a new catalytic system to synthesize benzofuranones is reported. A palladium-catalyzed intramolecular alkoxycarbonylation is employed to generate 3-substituted-benzofuran-2(3H)-ones from alkenylphenols under mild reaction conditions, linked to an ex situ formation of CO from N-formylsaccharin. The carefully chosen catalytic system enables an efficient reaction with a novel functional group tolerance, despite the high polymerization tendency of the starting material.
Conformational Control of Initiation Rate in Hoveyda-Grubbs Precatalysts
Gregg, Zackary R.,Griffiths, Justin R.,Diver, Steven T.
supporting information, p. 1526 - 1533 (2018/06/04)
When the coordinating isopropyl ether of the Hoveyda precatalyst is replaced by a cyclohexyl ether, it is possible to control the substituent's conformation in either the equatorial or axial position. A stereodivergent synthesis of axial and equatorial cyclohexyl vinyl ethers provided access to new ruthenium metathesis precatalysts by carbene exchange. The conformational disposition of the coordinating aryl ether was found to have a significant effect on the reactivity of the precatalyst in alkene metathesis. The synthesis of four new Ru carbene complexes is reported, featuring either the 1,3-bis(2,4,6-trimethylphenyl)dihydroimidazolylidene (H2IMes) or the 1,3-bis(2,6-diisopropylphenyl)dihydroimidazolylidene (SIPr) N-heterocyclic carbene ligand. The conformational isomers in the SIPr series were structurally characterized. Performance testing of all new precatalysts in three different ring-closing metatheses and an alkene cross metathesis illustrated superior performance by the precatalysts bearing axial coordinating ethers. Initiation rates with butyl vinyl ether were also measured, providing a useful comparison to existing Hoveyda-type metathesis precatalysts. Use of conformational control of the coordinating ether substituent provides a new way to modulate reactivity in this important class of alkene metathesis precatalysts.
A General Strategy for Open-Flask Alkene Isomerization by Ruthenium Hydride Complexes with Non-Redox Metal Salts
Lv, Zhanao,Chen, Zhuqi,Hu, Yue,Zheng, Wenrui,Wang, Haibin,Mo, Wanling,Yin, Guochuan
, p. 3849 - 3859 (2017/09/18)
A homogenous metal hydride (M?H) catalyst for isomerization normally requires rigorous air-free techniques. Here, we demonstrate a highly efficient protocol in which simple non-redox metal ions as Lewis acids can promote olefin isomerization dramatically with a commercially available RuH2(CO)(PPh3)3 complex in an open-flask system. Isomerization can be accomplished within a short time, and a satisfactory selectivity for different types of unsaturated compounds can be obtained. Meanwhile, an excellent turnover number up to 17208 was achieved under air, and open-flask gram-scale experiments further demonstrated the efficiency of the RuH2(CO)(PPh3)3/non-redox-metals system. We used FTIR spectroscopy, GC–MS, NMR spectroscopy and kinetics studies to evidence that in the sluggish RuH2(CO)(PPh3)3 catalyst, bloated PPh3 ligands cause steric hindrance for the coordination of the free alkene. Alternatively, the addition of non-redox metal ions could induce the dissociation of the PPh3 ligand to offer unoccupied coordination sites for the alkene and to form the Mg-bridged adduct OC?Ru?H2?Mg2+ as the highly active species, which benefited the isomerization significantly through the metal hydride addition–elimination pathway. Finally, this strategy was demonstrated as an impactful approach for hydride catalysts of other transition metals such as Os.
Chelating carbene ligand precursors and their use in the synthesis of metathesis catalysts
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Page/Page column 9, (2016/12/22)
Chelating ligand precursors for the preparation of olefin methathesis catalysts are disclosed. The resulting catalysts are air stable monomeric species capable of promoting various methathesis reactions efficiently, which can be recovered from the reaction mixture and reused. Internal olefin compounds, specifically beta-substituted styrenes, are used as ligand precursors. Compared to terminal olefin compounds such as unsubstituted styrenes, the beta-substituted styrenes are easier and less costly to prepare, and more stable since they are less prone to spontaneous polymerization. Methods of preparing chelating-carbene methathesis catalysts without the use of CuCl are disclosed. This eliminates the need for CuCl by replacing it with organic acids, mineral acids, mild oxidants or even water, resulting in high yields of Hoveyda-type methathesis catalysts. The invention provides an efficient method for preparing chelating-carbene metathesis catalysts by reacting a suitable ruthenium complex in high concentrations of the ligand precursors followed by crystallization from an organic solvent.
One-Step Synthesis of Substituted Benzofurans from ortho- Alkenylphenols via Palladium-Catalyzed C=H Functionalization
Yang, Dejun,Zhu, Yifei,Yang, Na,Jiang, Qiangqiang,Liu, Renhua
supporting information, p. 1731 - 1735 (2016/06/09)
A dehydrogenative oxygenation of C(sp2)=H bonds with intramolecular phenolic hydroxy groups has been developed, which provides a straightforward and concise access to structurally diversely benzofurans from ortho-alkenylphenols. The reaction is catalyzed by palladium on carbon (Pd/C) without any oxidants and sacrificing hydrogen acceptors.
