- Ruthenium Removal Using Silica-Supported Aromatic Isocyanides
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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.
-
supporting information
(2021/05/13)
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- Pd-Catalyzed Tandem Isomerization/Cyclization for the Synthesis of Aromatic Oxazaheterocycles and Pyrido[3,4- b]indoles
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An effient tandem process consisting of palladium-catalyzed double-bond isomerization of long-chain olefins and subsequent intramolecular cyclization promoted by B2(OH)2 for the synthesis of aromatic oxazaheterocycles is disclosed. This strategy can also provide rapid access to pyrido[3,4-b]indoles, trans-2-olefins, and eneamides bearing various functional groups with high regio- and stereoselectivity.
- Ding, Linglong,Niu, Yan-Ning,Xia, Xiao-Feng
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p. 10032 - 10042
(2021/07/31)
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- A Next-Generation Air-Stable Palladium(I) Dimer Enables Olefin Migration and Selective C?C Coupling in Air
-
We report a new air-stable PdI dimer, [Pd(μ-I)(PCy2tBu)]2, which triggers E-selective olefin migration to enamides and styrene derivatives in the presence of multiple functional groups and with complete tolerance of air. The same dimer also triggers extremely rapid C?C coupling (alkylation and arylation) at room temperature in a modular and triply selective fashion of aromatic C?Br, C?OTf/OFs, and C?Cl bonds in poly(pseudo)halogenated arenes, displaying superior activity over previous PdI dimer generations for substrates that bear substituents ortho to C?OTf.
- Kundu, Gourab,Rissanen, Kari,Schoenebeck, Franziska,Sperger, Theresa
-
supporting information
p. 21930 - 21934
(2020/10/02)
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- A Pd-Catalyzed Site-Controlled Isomerization of Terminal Olefins
-
An effective Pd-catalyzed isomerization of olefins with 2-PyPPh2 as the ligand is described. A wide variety of trans-2-olefins bearing various functional groups can be obtained with high regio- A nd stereoselectivity under mild reaction conditions. The ligand is crucial for the reaction.
- Ren, Wenlong,Sun, Fei,Chu, Jianxiao,Shi, Yian
-
supporting information
p. 1868 - 1873
(2020/03/03)
-
- Method for synthesizing E-methyl styrene compound
-
The method for preparing E-pyridyl or alkyl-substituted,bipyridine, in a solvent, in the presence of nitrogen protection, in, reaction 0 °C -50 °C in the presence of a metal nickel salt 24 - 36h, ligand and an additive is E, and the preparation method disclosed by the invention has the advantages, cheap 2,2 ’ - raw materials, easiness in obtaining 2,2 ’ - and the like. The ligand is,bipyridine or an alkyl-substituted bipyridyl compound, in the. presence of a nitrogen, protection agent, in a solvent.
- -
-
Page/Page column 10; 11
(2020/03/25)
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- Tandem Olefin Isomerization/Cyclization Catalyzed by Complex Nickel Hydride and Br?nsted Acid
-
We disclose a nickel/Br?nsted acid-catalyzed tandem process consisting of double bond isomerization of allyl ethers and amines and subsequent intramolecular reaction with nucleophiles. The process is accomplished by [(Me3P)4NiH]N(SO2CF3)2 in the presence of triflic acid. The methodology provides rapid access to tetrahydropyran-fused indoles and other oxacyclic scaffolds under very low catalyst loadings.
- Kathe, Prasad M.,Caciuleanu, Alexandru,Berkefeld, Andreas,Fleischer, Ivana
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p. 15183 - 15196
(2020/11/30)
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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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- Synthesis of Benzofuranones via Palladium-Catalyzed Intramolecular Alkoxycarbonylation of Alkenylphenols
-
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
-
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)
-
- A General Strategy for Open-Flask Alkene Isomerization by Ruthenium Hydride Complexes with Non-Redox Metal Salts
-
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
-
p. 3849 - 3859
(2017/09/18)
-
- Tunable Photocatalytic Activity of Palladium-Decorated TiO2: Non-Hydrogen-Mediated Hydrogenation or Isomerization of Benzyl-Substituted Alkenes
-
Palladium-decorated TiO2 is a moisture- and air-tolerant versatile catalyst. Its photocatalytic activity can be tuned in favor of hydrogenation or isomerization of benzyl-substituted alkenes simply by changing the irradiation wavelength. Benzyl-substituted alkenes are selectively isomerized to phenyl-substituted alkenes (E-isomer) with complete conversion over Pd@TiO2 under H2-free conditions. The reaction can be thermally induced under air or driven by visible-light irradiation at room temperature under Ar. UV irradiation in methanol solvent leads to efficient hydrogenation. The fine-tunability of the catalyst can also be used for selective deuterium incorporation using deuterated solvents; here H/D exchange is used as a mechanistic tool but with clear potential for isotope substitution applications.
- Elhage, Ayda,Lanterna, Anabel E.,Scaiano, Juan C.
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p. 250 - 255
(2017/05/31)
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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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- Endo-selective pd-catalyzed silyl methyl heck reaction
-
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
-
supporting information
p. 17926 - 17929
(2015/03/04)
-
- Eugenol isomerization promoted by arene-ruthenium(ii) complexes in aqueous media: Influence of the pH on the catalytic activity
-
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)
-
- Ylide hydrolysis in tandem reactions: A highly Z/E-selective access to 3-alkylidene dihydrobenzofurans and related analogues
-
An efficient synthetic approach to benzoheterocycles has been developed based on the hydrolysis of key ylide intermediates in a tandem reaction, upon which a variety of 3-alkylidene dihydrobenzofurans and related benzoheterocyclic products can be obtained
- Zhu, Jian-Bo,Wang, Peng,Liao, Saihu,Tang, Yong
-
supporting information
p. 3054 - 3057
(2013/07/26)
-
- Benign catalysis with iron: Unique selectivity in catalytic isomerization reactions of olefins
-
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
-
experimental part
p. 734 - 739
(2012/06/04)
-
- Modular palladium bipyrazoles for the isomerization of allylbenzenes - Mechanistic considerations and insights into catalyst design and activity, role of solvent, and additive effects
-
The catalytic activity of novel bidentate N,N-chelated palladium complexes derived from electron excessive, backbone fused 3,3'-bipyrazoles in the selective isomerization of terminal arylpropenoids and 1-alkenes is described. The catalysts are easily modified by appropriate wing tip substitution, while maintaining the same bulky, rigid unreactive aliphatic backbone. Eleven novel palladium complexes with different electronic and steric properties were investigated. Their performance in the palladium(II)-catalyzed isomerization of a series of substituted allylbenzenes was evaluated in terms of electronic as well as steric effects. Besides the clear finding of a general trend towards higher catalyst activity with more electron-donating properties of the coordinated N,N-bidentate ligands, we found that the catalytic process strongly depends on the choice of solvents and additives. Extensive solvent screening revealed that reactions run best in a 2:1 toluene-methanol mixture, with the alcohol employed being a crucial factor in terms of electronic and steric factors. A reaction mechanism involving a hydride addition-elimination mechanism starting with a palladium hydride species generated in situ in alcoholic solutions, as corroborated by experiments using deuterium labeled allylbenzene, seems to be most likely. The proposed mechanism is also supported by the observed reaction rate orders of κobs[cat.]≈1 (0.94), κobs [substrate]=0.20→1.0 (t→∞) and κobs [methanol]=-0.51 for the isomerization of allylbenzene. Furthermore, the influence of acid and base, as well as the role of the halide coordinated to the catalyst, are discussed. The system catalyzes the isomerization of allylbenzenes very efficiently yielding high E:Z selectivities under very mild conditions (room temperature) and at low catalyst loadings of 1 mol% palladium even in unpurified solvents. The integrity and stability of the catalyst system were confirmed by multiple addition reaction cycles, successive filtration and isolation experiments, and the lack of palladium black formation. Copyright
- Spallek, Markus J.,Stockinger, Skrollan,Goddard, Richard,Trapp, Oliver
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experimental part
p. 1466 - 1480
(2012/09/11)
-
- In situ generated bulky palladium hydride complexes as catalysts for the efficient isomerization of olefins. Selective transformation of terminal alkenes to 2-alkenes
-
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
-
supporting information; experimental part
p. 7998 - 8009
(2010/08/04)
-
- Continuous-Flow microreactor Chemistry under High-Temperature/pressure
-
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
-
supporting information; experimental part
p. 1321 - 1325
(2009/07/26)
-
- Mechanistic insights into the palladiumII-catalyzed hydroxyalkoxylation of 2-allylphenols
-
The Pd(OCOCF3)2/[(HOCH2CH 2NHCOCH2)2NCH2]2- catalyzed oxidation of o-allylphenol with H2O2 in water/methanol affords a syn and anti mixture of 2-(1,2-dihydroxypropyl)phenol and 2-(2-hydroxy-1-methoxypropyl)phenol. Mechanistic experiments and ESI-MS studies support a pathway wherein isomerization of the C=C bond followed by its epoxidation and oxirane opening led to the products. Recycling of the catalytic system led to gradual lost of activity.
- Thiery, Emilie,Chevrin, Carole,Le Bras, Jean,Harakat, Dominique,Muzart, Jacques
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p. 1859 - 1862
(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
-
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)
-
- A concise stereospecific synthesis of repinotan (BAYx3702)
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A concise synthesis of the 2-[aminomethyl]chroman derivative BAYx3702 (3), a potent 5-hydroxytryptamine (5-HT1A) antagonist is described. Utilization of a Mitsunobu reaction of phenol (11) with the non-racemic allylic alcohol (12) and consequen
- Gross, Jonathan L.
-
p. 8563 - 8565
(2007/10/03)
-
- Reaction of gem-dibromocyclopropanes or iodobenzofuran with trialkylmanganate
-
Treatment of gem-dibromocyclopropanes with trialkylmanganate, derived from manganese(II) chloride and three equivalents of Grignard reagent or alkyllithium, followed by an addition of electrophiles provided dialkylated cyclopropanes in good yields. It was
- Kakiya, Hirotada,Inoue, Rie,Shinokubo, Hiroshi,Oshima, Koichiro
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p. 2131 - 2137
(2007/10/03)
-
- 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)
-
- Manganese(II) chloride-catalyzed alkylmagnesation of 2-alkynylphenol
-
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)
-
- Photochemical Reactions of o-Alkenylphenols and 1-Alkenyl-2-naphthol with Alkylamines: Amination via Photoinduced Proton Transfer
-
Irradiation of o-alkenylphenols 1a-c and 2a-e in the presence of alkylamines gave o-(1-alkylaminoalkyl)phenols 4a-n and 5a-e in relatively good yields.Deprotonation of these o-alkenylphenols by the amines occurs in the excited singlet state to give the excited singlet state of the phenolate anion 7 and the ammonium ion.The proton transfer from the ammonium ion to the alkenyl group of 7 generates the zwitterion 8 that allows the nucleophilic addition of the amine at the benzylic cation centre.Similar photoamination of 1-(2-methylpropenyl)-2-naphthol 3 with alkylamines occured to give 1-(1-alkylamino-2-methylpropyl)-2-naphthols 6a-b.
- Yasuda, Masahide,Sone, Tatsuya,Tanabe, Kimiko,Shima, Kensuke
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p. 459 - 464
(2007/10/02)
-
- Pyrolyses of o-Alkoxy- and o-Alkylthio-N-Allylanilines and of Some Related O- and S-Allyl Compounds
-
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)
-
- Transformation of Carbon-Oxygen into Carbon-Carbon Bonds Mediated by Low-Valent Nickel Species
-
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
-
p. 4894 - 4899
(2007/10/02)
-
- 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)
-
- The Behaviour of 2H-1-Benzopyrans Toward Trialkylaluminium Reagents
-
2H-1-Benzopyrans react with trialkylaluminium compounds by alkyl- and hydrogen-transfer to C-2 and C-4 to give the o-allylphenols (2), (3), and the (E)-o-propenylphenols (4) and (5).The site of attack and the ratio of alkyl- to hydrogen-transfer depend on the alkylaluminium used and on the size of the substituent at C-2 of the pyran.A mechanism involving reaction of the alkylaluminium with the quinone methanide (6), which is in equilibrium with the pyran (1), is in accord with all experimental results.
- Alberola, Angel,Ortega, Alfonso Gonzalez,Pedrosa, Rafael,Bragado, Jose L. Perez,Amo, Justo F. Rodriguez
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p. 1209 - 1212
(2007/10/02)
-
- Process for the isomerization of aromatic alkenyl compounds
-
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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