- Ruthenium Removal Using Silica-Supported Aromatic Isocyanides
-
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.
- Gregg, Zackary R.,Glickert, Elise,Xu, Ruoshui,Diver, Steven T.
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supporting information
(2021/05/13)
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- Bioinspired Selective Synthesis of Heterodimer 8-5′ or 8- O-4′ Neolignan Analogs
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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.
- Dong, Kui,Zhao, Chuang-Yuan,Wang, Xiao-Ju,Wu, Li-Zhu,Liu, Qiang
-
supporting information
p. 2816 - 2820
(2021/04/13)
-
- Cascade Claisen and Meinwald Rearrangement for One-Pot Divergent Synthesis of Benzofurans and 2 H-Chromenes
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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.
- Song, Liyan,Su, Qian,Lin, Xi,Du, Zhihui,Xu, Huiyou,Ouyang, Ming-An,Yao, Hongliang,Tong, Rongbiao
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p. 3004 - 3009
(2020/04/20)
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- 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
-
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.
- González-Fernández, Rebeca,Crochet, Pascale,Cadierno, Victorio
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p. 3696 - 3706
(2019/10/11)
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- Selective Synthesis of Primary Anilines from NH3 and Cyclohexanones by Utilizing Preferential Adsorption of Styrene on the Pd Nanoparticle Surface
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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.
- Koizumi, Yu,Jin, Xiongjie,Yatabe, Takafumi,Miyazaki, Ray,Hasegawa, Jun-ya,Nozaki, Kyoko,Mizuno, Noritaka,Yamaguchi, Kazuya
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supporting information
p. 10893 - 10897
(2019/07/12)
-
- Synthesis of Benzofuranones via Palladium-Catalyzed Intramolecular Alkoxycarbonylation of Alkenylphenols
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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.
- Hirschbeck, Vera,Fleischer, Ivana
-
supporting information
p. 2854 - 2857
(2018/02/06)
-
- Conformational Control of Initiation Rate in Hoveyda-Grubbs Precatalysts
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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.
- Gregg, Zackary R.,Griffiths, Justin R.,Diver, Steven T.
-
supporting information
p. 1526 - 1533
(2018/06/04)
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- A General Strategy for Open-Flask Alkene Isomerization by Ruthenium Hydride Complexes with Non-Redox Metal Salts
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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.
- Lv, Zhanao,Chen, Zhuqi,Hu, Yue,Zheng, Wenrui,Wang, Haibin,Mo, Wanling,Yin, Guochuan
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p. 3849 - 3859
(2017/09/18)
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- Chelating carbene ligand precursors and their use in the synthesis of metathesis catalysts
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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.
- -
-
Page/Page column 9
(2016/12/22)
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- One-Step Synthesis of Substituted Benzofurans from ortho- Alkenylphenols via Palladium-Catalyzed C=H Functionalization
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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.
- Yang, Dejun,Zhu, Yifei,Yang, Na,Jiang, Qiangqiang,Liu, Renhua
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supporting information
p. 1731 - 1735
(2016/06/09)
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- Alkene isomerisation catalysed by a ruthenium PNN pincer complex
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The [Ru(CO)H(PNN)] pincer complex based on a dearomatised PNN ligand (PNN: 2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) was examined for its ability to isomerise alkenes. The isomerisation reaction proceeded under mild conditions after activation of the complex with alcohols. Variable-temperature (VT) NMR experiments to investigate the role of the alcohol in the mechanism lend credence to the hypothesis that the first step involves the formation of a rearomatised alkoxide complex. In this complex, the hemilabile diethylamino side-arm can dissociate, allowing alkene binding cis to the hydride, enabling insertion of the alkene into the metal-hydride bond, whereas in the parent complex only trans binding is possible. During this study, a new uncommon Ru0 coordination complex was also characterised. The scope of the alkene isomerisation reaction was examined. The catalyst tested positive! A dearomatised ruthenium PNN (2-di-tert-butylphosphinomethyl-6-diethylaminomethylpyridine) pincer complex, [Ru(CO)H(PNN)], was evaluated as an alkene isomerisation catalyst. The isomerisation reaction was greatly accelerated by the addition of alcohols, in particular isopropanol. Isomerisation of terminal to internal alkenes took place at room temperature. A mechanism was proposed based on variable-temperature NMR spectroscopy.
- Perdriau, Sébastien,Chang, Mu-Chieh,Otten, Edwin,Heeres, Hero J.,De Vries, Johannes G.
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supporting information
p. 15434 - 15442
(2016/02/18)
-
- Endo-selective pd-catalyzed silyl methyl heck reaction
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A palladium (Pd)-catalyzed endo-selective Heck reaction of iodomethylsilyl ethers of phenols and aliphatic alkenols has been developed. Mechanistic studies reveal that this silyl methyl Heck reaction operates via a hybrid Pd-radical process and that the silicon atom is crucial for the observed endo selectivity. The obtained allylic silyloxycycles were further oxidized into (Z)-alkenyldiols.
- Parasram, Marvin,Iaroshenko, Viktor O.,Gevorgyan, Vladimir
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supporting information
p. 17926 - 17929
(2015/03/04)
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- PdI2-catalyzed regioselective cyclocarbonylation of 2-allyl phenols to dihydrocoumarins
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A simple, efficient, and regioselective synthesis of 3-methyl-3,4-dihydrocoumarins is reported. The reaction of 2-allyl phenols with synthesis gas was catalyzed by PdI2, and 1,3,5,7-tetramethyl-6-phenyl-2,4,8-trioxa-6-phosphaadamantane (L1) and 1,3,5,7-tetramethyl-6-tetradecyl-2,4,8-trioxa-6-phosphaadamantane (L2) were effective as ligands, affording good product selectivity in all cases.
- Amzquita-Valencia, Manuel,Alper, Howard
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p. 5827 - 5829
(2015/01/08)
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- Eugenol isomerization promoted by arene-ruthenium(ii) complexes in aqueous media: Influence of the pH on the catalytic activity
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The catalytic activity of the arene-ruthenium(ii) complexes [RuCl 2(η6-C6H5OCH2CH 2OH)(L)] (L = P(OMe)3 (1a), P(OEt)3 (1b), P(OiPr)3 (1c), P(OPh)3 (1d), PPh3 (1e)) in the isomerization of eugenol into isoeugenol has been evaluated. Best results in terms of activity and selectivity were observed with those catalysts containing an aliphatic P-donor ligand (1a-c). Under optimized conditions, full conversions in extremely short reaction times (5 min), and with high levels of trans-selectivity (up to 98%), could be achieved. Addition of both NaOH or H2SO4 to the aqueous media resulted in rate enhancements, suggesting two different activation pathways of the pre-catalysts. We have evidenced that sodium hydroxide promotes the release of the η6- coordinated arene ligand, while sulfuric acid favours the Ru-Cl bond dissociation and the formation of aquo-derivatives [RuCl(H2O) (η6-C6H5OCH2CH 2OH)(L)][Cl]. The Royal Society of Chemistry 2013.
- Lastra-Barreira, Beatriz,Diaz-Alvarez, Alba E.,Menendez-Rodriguez, Lucia,Crochet, Pascale
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p. 19985 - 19990
(2013/11/06)
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- Reactions of triflate esters and triflamides with an organic neutral super-electron-donor
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The bis-pyridinylidene 13 converts aliphatic and aryl triflate esters to the corresponding alcohols and phenols respectively, using DMF as solvent, generally in excellent yields. While the deprotection of aryl triflates has been seen with other reagents and by more than one mechanism, the deprotection of alkyl triflates is a new reaction. Studies with 18O labelled DMF indicate that the C-O bond stays intact and hence it is the S-O bond that cleaves, underlining that the cleavage results from the extraordinary electron donor capability of 13. Trifluoromethanesulfonamides are converted to the parent amines in like manner, representing the first cleavage of such substrates by a ground-state organic reducing reagent.
- Jolly, Phillip I.,Fleary-Roberts, Nadia,O'Sullivan, Steven,Doni, Eswararao,Zhou, Shengze,Murphy, John A.
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p. 5807 - 5810
(2012/08/28)
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- Benign catalysis with iron: Unique selectivity in catalytic isomerization reactions of olefins
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The use of noble metal catalysts in homogeneous catalysis has been well established. Due to their price and limited availability, there is growing interest in the substitution of such precious metal complexes with readily available and bio-relevant catalysts. In particular, iron is a "rising star" in catalysis. Herein, we present a general and selective iron-catalyzed monoisomerization of olefins, which allows for the selective generation of 2-olefins. Typically, common metal complexes give mixtures of various internal olefins. Both bulk-scale terminal olefins and functionalized terminal olefins give the corresponding products under mild conditions in good to excellent yields. The proposed reaction mechanism was elucidated by in situ NMR studies and supported by DFT calculations and extended X-ray absorption fine structure (EXAFS) measurements.
- Jennerjahn, Reiko,Jackstell, Ralf,Piras, Irene,Franke, Robert,Jiao, Haijun,Bauer, Matthias,Beller, Matthias
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experimental part
p. 734 - 739
(2012/06/04)
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- In situ generated bulky palladium hydride complexes as catalysts for the efficient isomerization of olefins. Selective transformation of terminal alkenes to 2-alkenes
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Application of an in situ generated bulky palladium(II) hydride catalyst obtained from a 1:1:1 mixture of Pd(dba)2, P(tBu)3, and isobutyryl chloride provides an efficient protocol for the isomerization and migration of a variety of olefins. In addition to the isomerization of (Z)- to (E)-olefins, the conjugative migration of allylbenzenes, allyl ethers, and amines was effectively achieved in near-quantitative yields and with excellent functional group tolerance. Catalyst loadings in the range of 0.5-1.0 mol % were typically applied, but even loadings as low as 0.25 mol % could be achieved when the reactions were performed under neat conditions. More interestingly, the investigated catalyst proved to be selective for converting terminal alkenes to 2-alkenes. This one-carbon migration process for monosubstituted olefins provides an alternative catalyst, which bridges the gap between the allylation and propenylation/vinylation protocols. Several substrates, including homoallylic alcohols and amines, were selectively transformed into their corresponding 2-alkenes, and examples using enantiomerically enriched substrates provided products without epimerization at the allylic stereogenic carbon centers. Finally, some mechanistic investigations were undertaken to understand the nature of the active in situ generated Pd-H catalyst. These studies revealed that the catalytic system is highly dependent on the large steric demand of the P(tBu)3 ligand. The use of an alternative ligand, cataCXium PinCy, also proved effective for generating an active catalyst, and it was demonstrated in some cases to display better selectivity for the one-carbon shifts of terminal olefins. A possible intermediate involved in the preparation of the active catalyst was characterized by its single-crystal X-ray structure, which revealed a monomeric tricoordinated palladium(II) acyl complex, bearing a chloride ligand.
- Gauthier, Delphine,Lindhardt, Anders T.,Olsen, Esben P. K.,Overgaard, Jacob,Skrydstrup, Troels
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supporting information; experimental part
p. 7998 - 8009
(2010/08/04)
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- Continuous-Flow microreactor Chemistry under High-Temperature/pressure
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High-temperature organic synthesis can be performed under continuous-flow conditions in a stainless steel microtubular flow reactor capable of achieving temperatures of 350 °C and 200 bar. Under these extreme experimental environments transformations normally performed in a high-boiling solvent at reflux temperature - or under sealed-vessel microwave conditions - can be readily converted to a flow regime by using lower boiling solvents in or near their supercritical state. Wiley-VCH Verlag GmbH & Co, KGaA.
- Razzaq, Tahseen,Glasnov, Toma N.,Kappe, C. Oliver
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supporting information; experimental part
p. 1321 - 1325
(2009/07/26)
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- Palladium(II)-catalyzed enantioselective aerobic dialkoxylation of 2-propenyl phenols: A pronounced effect of copper additives on enantioselectivity
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A direct O2-coupled Pd(II)-catalyzed enantioselective dialkoxylation of 2-propenylphenols has been developed by utilizing chiral quinoline oxazoline ligands. A detrimental effect of added copper salts on enantioselectivity was observed which is attributed to the displacement of the chiral ligand off of Pd(II). Copyright
- Zhang, Yang,Sigman, Matthew S.
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p. 3076 - 3077
(2008/04/18)
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- Ruthenium-catalyzed intramolecular cyclization of hetero-functionalized allylbenzenes
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Intramolecular addition of heterofunctionalities to C{double bond, long}C double bonds without β-hydride elimination was investigated and catalyzed by ruthenium complexes. The combination of RuCl3 · nH2O (10 mol%) and 3 equiv. of AgOTf acted as a catalyst for cyclization of 2-allylphenol (1a) to 2,3-dihydro-2-methylbenzofuran (2a) in good yield in the presence of Cu(OTf)2 as a co-catalyst and PPh3 as a ligand. This catalyst system also catalyzed the cyclization of 2-allylbenzoic acid to lactone in 91% yield. Then, a new catalyst system (RuCp*Cl2)2 (1.0 mol%)/4AgOTf/4PPh3, was found to be more active even in the absence of Cu(OTf)2. Furthermore, this catalysis was applied to asymmetric reaction of 2-allylphenol (1a). When using TolBINAP as a ligand, over 60% e.e. was achieved.
- Ohta, Tetsuo,Kataoka, Yohei,Miyoshi, Akio,Oe, Yohei,Furukawa, Isao,Ito, Yoshihiko
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p. 671 - 677
(2008/02/06)
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- Efficient allyl to propenyl isomerization in functionally diverse compounds with a thermally modified Grubbs second-generation catalyst
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Heating compounds containing C-allylic appendages in MeOH in the presence of 10 mol % of Grubbs second-generation catalyst at 0.075 M substrate concentration leads to the corresponding 2-propenyl derivatives without further conjugation in the cases of ketones, esters, and lactams. The reaction is applicable to a large variety of functionally relevant terminal olefins, including O- and N-allyl ethers.
- Hanessian, Stephen,Giroux, Simon,Larsson, Andreas
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p. 5481 - 5484
(2007/10/03)
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- Proazaphosphatrane P(RNCH2CH2)3N (R = Me, i-Pr)-catalyzed isomerization of allylaromatics, allyl phenyl sulfide, allyl phenyl sulfone, and bis-allymethylene double bond-containing compounds
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Using a proazaphosphatrane catalyst, P(RNCH2CH2) 3N (R = Me, i-Pr), allylaromatics and allyl phenyl sulfide were selectively isomerized to the corresponding vinyl isomers in yields up to > 99% in CH3CN at 40°C. Efficient transformation of allyl phenyl sulfone at ambient temperature afforded an isomerization/dimerization product in >95% yield. Conjugation of bis-allylmethylene double bond-containing compounds gave the corresponding conjugated isomers for cis,cis-9,12- octadecadienol and its methyl ether in yields up to 97%, and desilylation/conjugation products were obtained from the catalytic reaction of the trimethylsilyl ether of cis,cis-9,12-octadecadienol. The reaction mechanism is discussed based upon the 1H and 31P NMR-monitored reactions in CD3CN or CH3CN under the reaction conditions.
- Yu, Zhengkun,Yan, Shenggang,Zhang, Guangtao,He, Wei,Wang, Liandi,Li, Yu,Zeng, Fanlong
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p. 111 - 117
(2007/10/03)
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- Ring-closing metathesis for the synthesis of 2H- and 4H-chromenes
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Six 4H-chromenes were synthesized from substituted phenols using vinylstannylation and ring-closing metathesis (RCM) as key steps. In addition, a different approach involving amongst other steps, an aryl allyl isomerization and RCM afforded a set of seven 2H-chromenes from phenolic precursors.
- Van Otterlo, Willem A.L.,Ngidi, E. Lindani,Kuzvidza, Samuel,Morgans, Garreth L.,Moleele, Simon S.,De Koning, Charles B.
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p. 9996 - 10006
(2007/10/03)
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- Highly selective isomerization of allyloxyalcohols to cyclic acetals or 1-propenyloxyalcohols
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Highly selective isomerization of allyloxyalcohols either to 1-propenyl derivatives or to cyclic acetals of propanal depending on the transition metal (Ru, Rh) complex used is described together with a proposed explanation of an alternative reaction, which permits broad application of the described method.
- Urbala, Magdalena,Ku?nik, Nikodem,Krompiec, Stanis?aw,Rzepa, Józef
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p. 1203 - 1206
(2007/10/03)
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- Synthesis of coumarins by ring-closing metathesis using Grubbs' catalyst
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A novel generally applicable synthesis of coumarins from phenolic substrates utilizing ring-closing metathesis is described. This sequence involves O-allylation of phenols followed by ortho-Claisen rearrangement, subsequent based-induced isomerization affording 2-(1-propenyl)phenols, acylation with acryloyl chloride, and finally ring-closing metathesis (RCM) with Grubbs' second generation catalyst.
- Nguyen Van, Tuyen,Debenedetti, Silvia,De Kimpe, Norbert
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p. 4199 - 4201
(2007/10/03)
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- Sequential isomerization and ring-closing metathesis: Masked styryl and vinyloxyaryl groups for the synthesis of benzo-fused heterocycles
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The use of an aryl allyl ether and an arylallyl group as masked vinyl ether and 1-propenylphenyl groups for ring-closing metathesis (RCM) leading to the synthesis of benzo-fused heterocycles was demonstrated by using a ruthenium-mediated isomerization followed by a ruthenium-mediated RCM reaction. This resulted in the syntheses of a variety of products including two substituted benzo[1,4]dioxins, a naphtho[2,3-b][1,4]dioxin, a 2H-chromene and a benzo[b]furan.
- Van Otterlo, Willem A. L.,Ngidi, E. Lindani,De Koning, Charles B.
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p. 6483 - 6486
(2007/10/03)
-
- CHELATING CARBENE LIGAND PRECURSORS AND THEIR USE IN THE SYNTHESIS OF METATHESIS CATALYSTS
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Chelating ligand precursors for the preparation of olefin metathesis catalysts are disclosed. The resulting catalysts are air stable monomeric species capable of promoting various metathesis 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 metathesis 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 metathesis 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.
- -
-
-
- Selective isomerization of 2-allylphenol to (Z)-2-propenylphenol catalyzed by Ru(cod)(cot)/PEt3
-
Ru(cod)(cot) (cod = cycloocta-1,5-diene, cot = cycloocta1,3,5-triene) catalyzes selective isomerization of 2-allylphenol to (Z)-2-propenylphenol in the presence of triethylphosphine with high yield (94%) and (Z)-selectivity (97%).
- Sato, Takehiro,Komine, Nobuyuki,Hirano, Masafumi,Komiya, Sanshiro
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p. 441 - 442
(2007/10/03)
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- Manganese(II) chloride-catalyzed alkylmagnesation of 2-alkynylphenol
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Treatment of 2-alkynylphenol with an alkyl Grignard reagent in the presence of a catalytic amount of manganese(II) chloride provided 2-(2-alkyl-1-alkenyl)phenol in good yield. Alkylmagnesation proceeded with high regio-and stereoselectivities.
- Nishimae, Shinji,Inoue, Rie,Shinokubo, Hiroshi,Oshima, Koichiro
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p. 785 - 786
(2007/10/03)
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- Transition metal-catalyzed cyclization of 2-allylphenol to 2,3-dihydro-2-methylbenzofuran without β-elimination
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The intramolecular nucleophilic addition of 2-allylphenol was catalyzed by RuCl3·nH2O/AgOTf-PPh3-Cu(OTf) 2 to afford 2,3-dihydro-2-methylbenzofuran in good yield, while 2-(3-butenyl)-phenol was converted to 3,4-dihydro-2(2H)-methylbenzopyran.
- Hori, Kazushige,Kitagawa, Hideki,Miyoshi, Akio,Ohta, Tetsuo,Furukawa, Isao
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p. 1083 - 1084
(2007/10/03)
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- Applications of High-Temperature Aqueous Media for Synthetic Organic Reactions
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Preparative organic synthesis was investigated in aqueous media at temperatures up to 300°C. Experiments were conducted with a recently disclosed pressurized microwave batch reactor (MBR) or in conventionally heated autoclaves. Thirty-six examples are presented. Among these, methods were developed for a Fischer synthesis, an intramolecular aldol condensation that was scaled up, decarboxylation of indole-2-carboxylic acid, Rupe rearrangement of 1-ethynyl-l-cyclohexanol, isomerization of carvone to carvacrol, and conversion of phenylacetylene to acetophenone. The applicability of high-temperature water was also demonstrated for biomimetic processes important in food, flavor, and aroma chemistry and for tandem reactions such as formation of 2-methyl-2,3- dihydrobenzofuran from allyl phenyl ether. When addition of acid or base was necessary, less agent was usually required for high-temperature processes than for those at and below boiling, and the reactions often proceeded more selectively. In some instances the requirement was orders of magnitude lower, with obvious consequences for safe, economic processing and for lowering costs of effluent disposal. The diversity of reactions indicates that high-temperature aqueous media could play an increasingly important role in the development of new preparative processes.
- An, Jingyi,Bagnell, Laurence,Cablewski, Teresa,Strauss, Christopher R.,Trainor, Robert W.
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p. 2505 - 2511
(2007/10/03)
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- Reactions of allyl phenyl ether in high-temperature water with conventional and microwave heating
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In a systematic study, allyl phenyl ether (1) was heated in water for 1 h at temperatures of 180°C and above. Parallel experiments were conducted with a conventionally heated autoclave and a recently developed microwave batch reactor. Relatively modest temperature differences resulted in diverse product distributions, and these were independent of the method of heating. Maximum conversion of 1 to 2-allylphenol occurred at 200°C (56%) and to 2-methyl-2,3-dihydrobenzofuran at 250°C (72%). Although 2-(2-hydroxyprop-1-yl)phenol comprised less than 1% of the product mixture at both 180 and 260°C, it accounted for 37% at 230°C. The reaction sequence was investigated by heating intermediates individually at selected temperatures up to 290°C. Hydration of 2-allylphenol to 2-(2-hydroxyprop-1-yl)phenol was partially reversible. The work showed that high-temperature water constitutes an environmentally benign alternative to the use of acid catalysts or organic solvents and offers scope for interconversion of alcohols and alkenes.
- Bagnell, Laurence,Cablewski, Teresa,Strauss, Christopher R.,Trainor, Robert W.
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p. 7355 - 7359
(2007/10/03)
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- ISOMERIZATION OF ALLYL ALCOHOLS WITH RHODIUM(I) COMPLEXES
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The results of the isomerization reaction of some allyl alcohols (2-propen-1-ol, 3-buten-2-ol and 1-octen-3-ol) with the Rh(I) complexes HRh(CO)(PPh3)3, HRh4, Rh4ClO4 are presented.The mechanism of the Rh3-catalyzed isomerization is discussed.
- Trzeciak, Anna Maria,Ziolkowski, Jozef Julian
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p. 403 - 410
(2007/10/02)
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- Microwave-Induced Reactions of Organic Substrates in the Cage of Zeolites
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Microwave irradiation of compounds 1, 7, 15, 19, 23, and 24 adsorbed on Y zeolites has been studied.The reaction rate of the corresponding rearrangement, dehydrogenation and dehydration is dramatically enhanced as compared with reactions under thermal conditions.
- Ipaktschi, Junes,Brueck, Matthias
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p. 1591 - 1593
(2007/10/02)
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- Pyrolyses of o-Alkoxy- and o-Alkylthio-N-Allylanilines and of Some Related O- and S-Allyl Compounds
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The o-substituted allyl compounds (1)-(12) have been pyrolysed in order to generate aminyl, phenoxyl, and thiophenoxyl radicals with adjacent substituents.In all cases, products are formed by intramolecular hydrogen transfer from the substituent to the radical centre.This process may be followed by rearrangement to give an aldehyde, by heteroatom extrusion to give an alkene, or by ring formation to give five-membered ring heterocycles (Scheme 1, routes A, B1, and B2 respectively.The distribution of products formed by each route is dependent both on the nature of the o-substituent, and on the nature of the initial radical.
- Cadogan, J. I. G.,Hickson, Clare L.,McNab, Hamish
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p. 1885 - 1890
(2007/10/02)
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- Transformation of Carbon-Oxygen into Carbon-Carbon Bonds Mediated by Low-Valent Nickel Species
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The substitution of alkoxy groups of enol ethers (1-methoxycyclohexenes, 1-methoxy-1-alkenes, and benzofuran) and aryl ethers (methoxynaphthalenes, cresyl methyl ethers, and dimethoxybenzenes) by hydrogen, alkyl groups, and aryl units, through Grignard reactions catalyzed by bis(triphenylphosphine)nickel dichloride or nickel dichloride, is described.The stereochemistry of the new reaction is portrayed, especially in connection with processes involving ring opening of dihydropyrans and dihydrofurans.The reaction has been applied to the synthesis of a termite trail pheromone and the acetate of the Douglas fir beetle aggregation pheromone.
- Wenkert, Ernest,Michelotti, Enrique L.,Swindell, Charles S.,Tingoli, Marco
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p. 4894 - 4899
(2007/10/02)
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- REACTION DE WITTIG EN MILIEU HETEROGENE SOLIDE-LIQUIDE : TRANSFORMATION DIRECTE DES ALDEHYDES PHENOLIQUES NATURELS EN ALCENES
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New alkenylphenols can be obtained directly, without protecting the phenol group from the condensation reaction between phenolic aldehydes and various phosphonium salts in the presence of potassium carbonate in protic and aprotic media, using a solid-liquid phase transfer.
- Bigot, Yves Le,Delmas, Michel,Gaset, Antoine
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p. 193 - 196
(2007/10/02)
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- Process for the isomerization of aromatic alkenyl compounds
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Aromatic alkenyl compounds, for example, eugenol and safrole, are isomerized, for example to isoeugenol and isosafrole, by contact with a ruthenium or osmium catalyst.
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