- Organopromoted Direct Synthesis of 1,1-Diphenyl-3-arylindanes via Formal [3+2] Cycloadditions of Triphenylcarbenium Tetrafluoroborate with Styrenes
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A formal [3+2] cycloaddition of triphenylcarbenium tetrafluoroborate with structurally different styrene derivatives has been developed. A combination of benzophenone and Et3N is key for promoting a formal [3+2] cycloaddition of triphenylcarbenium tetrafluoroborate with styrenes affording 1,1-diphenyl-3-arylindanes in moderate to good yields. The reaction mechanism of this transformation is also discussed.
- Surapanich, Nakin,Chaisuwan, Patcharin,Kuhakarn, Chutima,Reutrakul, Vichai
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- Synthesis and Catalytic Activity of Atrane-type Hard and Soft Lewis Superacids with a Silyl, Germyl, or Stannyl Cationic Center
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The synthesis and isolation of atrane-type molecules 1E+ (E=Si, Ge, or Sn) having a cationic group 14 elemental center are reported. The cations 1E+ act as hard and soft Lewis superacids, which readily interact with various hard and soft Lewis basic substrates. The rigid atrane framework stabilizes the localized positive charge on the elemental center and assists the formation of the well-defined highly coordinated states of 1E+. The cations were applied to the hydrodefluorination, Friedel-Crafts reaction, alkyne cyclization, and carbonyl reduction as Lewis acid catalysts. Most notably, [1Si][ClO4] exhibits unique chemoselectivity that depends on a solvent in the competitive reaction of silyl enol ether with a mixture of benzaldehyde dimethyl acetal and benzaldehyde. Our findings indicate the potential of hard and soft Lewis superacids in organic synthesis.
- Tanaka, Daiki,Konishi, Akihito,Yasuda, Makoto
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- Simple and one-pot protocol for synthesis of indene-spiro-oxindoles involving tandem Prins and Friedel-Crafts reactions
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(Chemical Equation Presented) A simple and one-pot protocol for the synthesis of indene-spiro-oxindole derivatives via TiCl4-mediated reaction between 1,1-diarylethylenes and isatin derivatives involving construction of two carbon-carbon bonds
- Basavaiah, Deevi,Reddy, Kanumuri Ramesh
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- Probing steric influences on electrophilic phosphonium cations: A comparison of [(3,5-(CF3)2C6H3)3PF]+ and [(C6F5)3PF]+
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The electrophilic phosphonium cation (EPC) salt [(3,5-(CF3)2C6H3)3PF][B(C6F5)4] (2) is prepared via oxidation of the precursor phosphine with XeF2 and subse
- Lafortune, James H. W.,Szkop, Kevin M.,Farinha, Farah E.,Johnstone, Timothy C.,Postle, Shawn,Stephan, Douglas W.
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- Alkoxymagnesium iodide complexes
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The complexes R(Ph)MeCOMg(Et2O)I [1, R = Me (a), Ph (b)] were obtained by the reaction of R(Ph)C=O with MeMgI in diethyl ether in good yields. Crystallisation of 1 from acetonitrile resulted in single crystals of di- and trinuclear complexes I2(μ-OCPhMe2)2Mg(MeCN) 4 (2) and {2[I(MeCN)Mg(μ-OCPh2Me)2Mg(MeCN)I] (3) × [I(MeCN)Mg(μ-OCPh2Me)2Mg(μ-OCPh 2Me)2Mg(MeCN)I] (4) × 2CH2Cl2} in which the metal centres are linked by alkoxy substituents. The thermal decomposition of the complexes 1 was studied by successive detection of the EI mass spectra of diethyl ether, the olefins 5, the tertiary alcohols 6, and the formal olefin dimers 7. The complexes R1(Ph)MeCOMg(Et2O)I [1, R1 = Me (a), Ph (b)] are obtained by the reaction of R 1(Ph)C=O with MeMgI in diethyl ether in good yields. Crystallisation of 1 from acetonitrile results in single crystals of di- and trinuclear complexes (2, 3 and 4) in which the metal centres are linked by alkoxy substituents. The thermal decomposition of the complexes 1 is monitored by mass spectral detection of the decomposition products. Copyright
- Haiss, Peter,Kuhn, Annette,Kuhn, Norbert,Maichle-Moessmer, Caecilia,Laufer, Stefan,Steimann, Manfred,Zeller, Klaus-Peter
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- Metal-free pincer ligand chemistry polycationic phosphonium Lewis acids
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Oxidation of 2,6-bis(diphenylphosphine)methyl pyridine with MeO3SCF3, yields the dication [2,6-(CH2PMePh2)2C5H3N][CF3SO3]22, while subsequent treatment with two equivalents of [K(THF)n][B(C6F5)4] (n = 1.3-1.5) afforded [2,6-(CH2PMePh2)2C5H3N][B(C6F5)4]23. Analogous treatment using XeF2 afforded 2,6-(CH2PF2Ph2)2C5H3N 4, while subsequent fluoride abstractions afford the corresponding [BF4], [CF3SO3] and [B(C6F5)4] salts, 5-7, respectively. Compound 4 reacts with an excess of MeO3SCF3 to give [2,6-(CH2PF2Ph2)2C5H3N(CH3)][CF3SO3] 8 while subsequent reaction with [Et3Si·2C7H8][B(C6F5)4] gave the related tricationic species, 9. The Lewis acidity of these di- and triphosphonium cations 3, 7 and 9 was examined and their utility as Lewis acid catalysts was assessed in the dimerization of 1,1-diphenylethylene, the hydrodefluorination of 1-fluoroadamantane, and the dehydrocoupling of phenol and silane.
- Szkop, Kevin M.,Stephan, Douglas W.
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- Lewis Superacidic Catecholato Phosphonium Ions: Phosphorus-Ligand Cooperative C-H Bond Activation
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A series of catecholato phosphonium ions, including the first stable bis(catecholato)-substituted derivatives, are isolated and fully characterized. The cations rank among the most potent literature-known Lewis acids on the Gutmann-Beckett and ion affinit
- Greb, Lutz,Roth, Daniel,Stephan, Douglas W.,Stirn, Judith
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supporting information
p. 15845 - 15851
(2021/10/02)
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- Towards Naked Zinc(II) in the Condensed Phase: A Highly Lewis Acidic ZnII Dication Stabilized by Weakly Coordinating Carborate Anions
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The employment of the hexyl-substituted anion [HexCB11Cl11]? allowed the synthesis of a ZnII species, Zn[HexCB11Cl11]2, 3, in which the Zn2+ cation is only weakly coordinated to two carborate counterions and that is soluble in low polarity organic solvents such as bromobenzene. DOSY NMR studies show the facile displacement of at least one of the counterions, and this near nakedness of the cation results in high catalytic activity in the hydrosilylation of 1-hexene and 1-methyl-1cyclohexene. Fluoride ion affinity (FIA) calculations reveal a solution Lewis acidity of 3 (FIA=262.1 kJ mol?1) that is higher than that of the landmark Lewis acid B(C6F5)3 (FIA=220.5 kJ mol?1). This high Lewis acidity leads to a high activity in catalytic CO2 and Ph2CO reduction by Et3SiH and hydrogenation of 1,1-diphenylethylene using 1,4-cyclohexadiene as the hydrogen source. Compound 3 was characterized by multinuclear NMR spectroscopy, mass spectrometry, single crystal X-ray diffraction, and DFT studies.
- Adet, Nicolas,Specklin, David,Gourlaouen, Christophe,Damiens, Thibault,Jacques, Béatrice,Wehmschulte, Rudolf J.,Dagorne, Samuel
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p. 2084 - 2088
(2020/11/30)
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- Nitrenium Salts in Lewis Acid Catalysis
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Molecular compounds featuring nitrogen atoms are typically regarded as Lewis bases and are extensively employed as donor ligands in coordination chemistry or as nucleophiles in organic chemistry. By contrast, electrophilic nitrogen-containing compounds are much rarer. Nitrenium cations are a new family of nitrogen-based Lewis acids, the reactivity of which remains largely unexplored. In this work, nitrenium ions are explored as catalysts in five organic transformations. These reactions are the first examples of Lewis acid catalysis employing nitrogen as the site of substrate activation. Moreover, these compounds are readily accessed from commercially available reagents and exhibit remarkable stability toward moisture, allowing for benchtop transformations without the need to pretreat solvents.
- Mehta, Meera,Goicoechea, Jose M.
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supporting information
p. 2715 - 2719
(2020/01/24)
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- Bis(perchlorocatecholato)germane: Hard and Soft Lewis Superacid with Unlimited Water Stability
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Previously described Lewis superacids are moisture sensitive and predominantly hard in character—features that severely limit their widespread use in orbital-controlled reactions and under non-inert conditions. Described here are adducts of bis(perchlorocatecholato)germane, the first hard and soft Lewis superacid based on germanium. Remarkably, the synthesis of this compound is performed in water, and the obtained H2O adduct constitutes a strong Br?nsted acid. If applied as an adduct with aprotic donors, it displays excellent activity in a diverse set of Lewis acid catalyzed transformations, covering hydrosilylation, hydrodefluorination, transfer hydrogenation, and carbonyl–olefin metathesis. Given the very straightforward synthetic access from two commercially available precursors, the unlimited water stability and the soft Lewis acidic character, it promotes the transfer of Lewis superacidity into organic synthesis and materials science.
- Greb, Lutz,Roth, Daniel,Wadepohl, Hubert
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supporting information
p. 20930 - 20934
(2020/09/17)
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- Decarbonylation of phenylacetic acids by high valent transition metal halides
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Triphenylacetic acid underwent unusual decarbonylation when allowed to react with a series of halides of group 4-6 metals in their highest oxidation state, in dichloromethane at ambient temperature. Thus, the reaction of CPh3COOH with MoCl5, in 1:1 molar ratio, afforded the trityl salt [CPh3][MoOCl4], 1, in 79% yield, while the 1:2 reaction of CPh3COOH with NbF5 afforded [CPh3][NbF6], 2, in 70% yield, NbOF3 being the metal co-product. CPh3COOH reacted with NbCl5, TiF4 and WOCl4 to give mixtures of compounds, however the cation [CPh3]+ was NMR identified in each case. [CPh3][NbCl6], 3, was isolated from NbCl5 and CPh3COCl, prior to being generated from CPh3COOH and PCl5. The reaction of CPh3COOH with TiCl4 was non-selective, and the salt [CPh3][Ti2Cl8(μ-κ2-O2CCPh3)], 4, was obtained in 18% yield. The decarbonylation reactions of CMePh2COCl and CMe2PhCOCl by means of NbCl5 led to the indanes 5a-b, which were isolated in 79-97% yields after hydrolysis of the mixtures and subsequent alumina filtration of the organic phases. The reactions of CH(Ph)2COOH with NbCl5 and WCl6 afforded NbCl4(OOCCHPh2), 6, and CHPh2COCl, respectively, as the prevalent species. CPh2(CH2CH2Br)COOH did not undergo CO release when allowed to interact with WCl6, instead selective intramolecular condensation to C(Ph)2C(O)OCH2CH2, 7, occurred. MeCCCOOH underwent hydrochlorination by WCl6 to give MeC(Cl)CHCOOH, 8, in 72% yield. All the products were fully characterized by elemental analysis, IR and multinuclear NMR spectroscopy. In addition, the solid state structures of 1, 2, 4, 7, and 8 were elucidated by X-ray diffraction.
- Bartalucci, Niccolò,Marchetti, Fabio,Zacchini, Stefano,Pampaloni, Guido
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p. 5725 - 5734
(2019/05/10)
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- Samarium triflate-catalyzed dimerization of vinylarenes
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We report the preparation of substituted indanes and their dimeric isomers via the samarium triflate-mediated [Sm(OTf)3, 10 mol%] self-dimerization of vinylarenes in MeNO2 at 25 oC for 10 h. The diverse products were obtained in moderate to high yields. The synthesis involves a (3+2) annulation via the formation of carbon-carbon bonds. Plausible mechanisms are proposed and discussed. The investigation of various rare metal triflates catalyst loadings, reaction conditions, and substrate scope led to an operationally easy one-pot Friedel-Crafts reaction protocol.
- Chang, Meng-Yang,Tsai, Yu-Lin
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p. 200 - 211
(2020/02/13)
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- Transfer Hydrocyanation of α- and α,β-Substituted Styrenes Catalyzed by Boron Lewis Acids
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A straightforward gram-scale preparation of cyclohexa-1,4-diene-based hydrogen cyanide (HCN) surrogates is reported. These are bench-stable but formally release HCN and rearomatize when treated with Lewis acids. For BCl3, the formation of the isocyanide adduct [(CN)BCl3]? and the corresponding Wheland complex was verified by mass spectrometry. In the presence of 1,1-di- and trisubstituted alkenes, transfer of HCN from the surrogate to the C?C double bond occurs, affording highly substituted nitriles with Markovnikov selectivity. The success of this transfer hydrocyanation depends on the Lewis acid employed; catalytic amounts of BCl3 and (C6F5)2BCl are shown to be effective while B(C6F5)3 and BF3?OEt2 are not.
- Orecchia, Patrizio,Yuan, Weiming,Oestreich, Martin
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supporting information
p. 3579 - 3583
(2019/02/05)
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- Synthesis and Properties of Triarylhalostibonium Cations
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As part of our fundamental interest in the chemistry of main-group Lewis acids, we have decided to target stibonium cations whose Lewis acidity is enhanced by the presence of a halogen substituent directly bound to antimony. Starting from Ph3Sb
- Yang, Mengxi,Gabba?, Fran?ois P.
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p. 8644 - 8650
(2017/08/14)
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- Catalytic double hydroarylation of alkynes to 9,9-disubstituted 9,10-dihydroacridine derivatives by an electrophilic phenoxyphosphonium dication
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The electrophilic pyridinium-substituted phenoxy-phosphonium dicationic salt [(PhO)P(2-(N-Mepy))Ph2][B(C6F5)4]2, is shown to be an effective catalyst for the double hydroarylation of alkynes with diarylamines to afford a series of 9-methyl-9-aryl-9,10-dihydroacridine and 9,10-dimethyl-9-aryl-9,10-dihydroacridine derivatives.
- LaFortune, James H. W.,Bayne, Julia M.,Johnstone, Timothy C.,Fan, Louie,Stephan, Douglas W.
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supporting information
p. 13312 - 13315
(2017/12/26)
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- Selective reaction of benzyl alcohols with HI gas: Iodination, reduction, and indane ring formations
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Reactions of benzyl alcohols with HI in solvent-free conditions were examined. Three types of reactions (iodination, reduction, and ring formation) occurred depending on the degree of crowding around the benzyl position and the benzylic stabilization of substrates. Results also showed that the ring formation to give indanes proceeded efficiently when HI was used, and that compounds with electron-rich aromatic rings gave indane derivatives in good yields.
- Matsumoto, Shoji,Naito, Masafumi,Oseki, Takehisa,Akazome, Motohiro,Otani, Yasuhiko
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p. 7254 - 7259
(2017/11/24)
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- Pyridinium-phosphonium dications: Highly electrophilic phosphorus-based Lewis acid catalysts
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Using commercially available 2-pyridyldiphenylphosphine (o-NC5H4)PPh2, a family of electrophilic phosphonium cations [(o-NC5H4)PFPh2]+ (2) and dications [(o-MeNC5H4)PRPh2]2+ (R = F (4); Me (5)) were prepared. The Lewis acidity of these pyridinium-phosphonium dications was probed in Friedel-Crafts dimerization, hydrodefluorination, hydrosilylation, dehydrocoupling and hydrodeoxygenation reactions. The influence of the counterion on the catalytic activity of the electrophilic phosphonium cations is also discussed.
- Bayne, Julia M.,Holthausen, Michael H.,Stephan, Douglas W.
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p. 5949 - 5957
(2016/04/26)
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- Ferrocenyl-derived electrophilic phosphonium cations (EPCs) as Lewis acid catalysts
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Oxidation of diphenylphosphinoferrocene and 1,1′-bis(diphenylphosphino)ferrocene with XeF2, resulted in the formation of CpFe(η5-C5H4PF2Ph2) 1 and Fe(η5-C5H4PF2Ph2)22 respectively. Subsequent reactions with [SiEt3][B(C6F5)4] yielded [CpFe(η5-C5H4PFPh2)][B(C6F5)4] 3 and [Fe(η5-C5H4PFPh2)2] [B(C6F5)4]24. PhP(η5-C5H4)2Fe 5 was prepared, converted to [PhMeP(η5-C5H4)2Fe][O3SCF3] 6 and then to [PhMeP(η5-C5H4)2Fe][B(C6F5)4] 7. The ability of the salts 3, 4 and 7 to catalyze Friedel-Crafts dimerization of 1,1-diphenylethylene, dehydrocoupling of phenol and triethylsilane, deoxygenation of acetophenone and hydrodefluorination of 1-fluoropentane were probed. While compound 7 proved to be ineffective, compounds 3 and 4 were useful Lewis acid catalysts. Compounds 3 and 4 were shown to catalyze the deoxygenation of a series of ketones.
- Mallov, Ian,Stephan, Douglas W.
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supporting information
p. 5568 - 5574
(2016/04/09)
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- Electrophilic phosphonium cations (EPCs) with perchlorinated-aryl substituents: Towards air-stable phosphorus-based Lewis acid catalysts
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A series of phosphines incorporating (C6Cl5) substituents, Ph2P(C6Cl5) 1, PhP(C6Cl5)22, P(C6Cl5)33 and (C6F5)P(C6Cl5)24 were prepared. In the case of 1, 2 and 4, these were converted to the corresponding aryl-difluorophosphoranes 5-7via reaction with XeF2, whereas reaction of 3 with XeF2 afforded only an inseparable mixture of products. The compounds 5-7 were converted to the fluorophosphonium cations 8-10, whereas the reaction of 3 with Selectfluor afforded (C6Cl5)2POF and (C6Cl5)2. The fluorophosphonium salts showed evidence of improved air stability as well as Lewis acid catalytic activity in hydrodefluorination, hydrosilylation, deoxygenation and dehydrocoupling chemistry.
- Postle, Shawn,Podgorny, Vitali,Stephan, Douglas W.
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p. 14651 - 14657
(2016/10/03)
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- Electrophilic phenoxy-substituted phosphonium cations
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A family of electrophilic phenoxy-substituted phosphonium salts [(RO)P(C6F5)3][B(C6F5)4] (R = C6H5, 4-FC6H4, 2,4-F2C6H3, C6F5) have been synthesized and their air stability was evaluated. Computations of the fluoride ion affinity and global electrophilicity index have been used to compare the electrophilicity of these phosphonium salts. The Lewis acidity of these phosphonium salts was probed computationally and experimentally in a Friedel-Crafts-type dimerization, hydrodefluorination, hydrosilylation, hydrodeoxygenation, and dehydrocoupling reactions.
- LaFortune, James H. W.,Johnstone, Timothy C.,Pérez, Manuel,Winkelhaus, Daniel,Podgorny, Vitali,Stephan, Douglas W.
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supporting information
p. 18156 - 18162
(2016/11/25)
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- Metal-Free Domino One-Pot Decarboxylative Cyclization of Cinnamic Acid Esters: Synthesis of Functionalized Indanes
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Trifluoroacetic acid promoted unprecedented domino reaction for the synthesis of diverse indanes starting from simple cinnamic acid esters is described. Their formation can be explained via acid triggered decarboxylation of cinnamic acid esters and subsequent inter/intramolecular cyclization. Overall process involves in the intramolecular cleavage of two σ-bonds (C-O and C-C) and inter/intramolecular construction of two/one C-C σ-bond(s). Significantly, this protocol was successful without the aid of any metal salts.
- Gopi Krishna Reddy, Alavala,Satyanarayana, Gedu
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p. 12212 - 12222
(2016/12/23)
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- Electrophilic bis-fluorophosphonium dications: Lewis acid catalysts from diphosphines
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Stepwise oxidation of 1,8-bis(diphenylphosphino)naphthalene and a series of (oligo)methylene-linked diphosphines with XeF2 followed by fluoride abstraction yields a family of compounds featuring phosphine, phosphonium and phosphorane moieties in close proximity. The bisphosphonium ions [(C10H6)(Ph2PF)2]2+ (5) and [CH2(Ph2PF)2]2+ (9a) exhibit remarkable Lewis acidity arising from the proximity of the phosphonium centers. The effectiveness of bisphosphonium dications (5, 9a-e) is examined in a series of Lewis acid catalysed transformations.
- Holthausen, Michael H.,Hiranandani, Rashi R.,Stephan, Douglas W.
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p. 2016 - 2021
(2015/08/18)
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- Electrophilic Fluorophosphonium Cations in Frustrated Lewis Pair Hydrogen Activation and Catalytic Hydrogenation of Olefins
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The combination of phosphorus(V)-based Lewis acids with diaryl amines and diaryl silylamines promotes reversible activation of dihydrogen and can be further exploited in metal-free catalytic olefin hydrogenation. Combined experimental and density functional theory (DFT) studies suggest a frustrated Lewis pair type activation mechanism. FLP hydrogenation: The combination of a phosphorus(V)-based Lewis acid with diaryl amines or diaryl silylamines promotes reversible activation of dihydrogen and can be further exploited in metal-free catalytic olefin hydrogenation. Combined experimental and density functional theory (DFT) studies suggest a frustrated Lewis pair (FLP)-type activation mechanism.
- Vom Stein, Thorsten,Perz, Manuel,Dobrovetsky, Roman,Winkelhaus, Daniel,Caputo, Christopher B.,Stephan, Douglas W.
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supporting information
p. 10178 - 10182
(2015/09/01)
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- The highly lewis acidic dicationic phosphonium salt: [(SIMes)PFPh 2][B(C6F5)4]2
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The dicationic imidazolium-phosphonium salt [(SIMes)PFPh 2][B(C6F5)4]2 has been prepared and shown to exhibit remarkable Lewis acidity in stoichiometric reactions and acting as an effective Lewis acid catalyst for the hydrodefluorination of fluoroalkanes and the hydrosilylation of olefins.
- Holthausen, Michael H.,Mehta, Meera,Stephan, Douglas W.
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supporting information
p. 6538 - 6541
(2014/06/24)
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- Olefin isomerization and hydrosilylation catalysis by lewis acidic organofluorophosphonium salts
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Organofluorophosphonium salts of the formula [(C6F 5)3-xPhxPF][B(C6F5) 4] (x = 0, 1) exhibit Lewis acidity derived from a low-lying σ* orbital at P opposite F. This acidity is evidenced by the reactions of these salts with olefins, which catalyze the rapid isomerization of 1-hexene to 2-hexene, the cationic polymerization of isobutylene, and the Friedel-Crafts-type dimerization of 1,1-diphenylethylene. In the presence of hydrosilanes, olefins and alkynes undergo efficient hydrosilylation catalysis to the alkylsilanes. Experimental and computational considerations of the mechanism are consistent with the sequential activation and 1,2-addition of hydrosilane across the unsaturated C-C bonds.
- Perez, Manuel,Hounjet, Lindsay J.,Caputo, Christopher B.,Dobrovetsky, Roman,Stephan, Douglas W.
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supporting information
p. 18308 - 18310
(2014/01/06)
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- Combinations of ethers and B(C6F5)3 function as hydrogenation catalysts
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It works ether way: Labile adducts of dialkyl ethers with the electrophilic borane B(C6F5)3 are shown to scramble HD to H2 and D2 and catalyze the hydrogenation of 1,1-diphenylethylene. Copyright
- Hounjet, Lindsay J.,Bannwarth, Christoph,Garon, Christian N.,Caputo, Christopher B.,Grimme, Stefan,Stephan, Douglas W.
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supporting information
p. 7492 - 7495
(2013/07/26)
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- Nucleophilic attack in methoxycarbenes: Heterolytic cleavage of the carbon (sp3)-oxygen bond versus aminolysis
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The iridium methoxycarbene [IrCp*Cl{=C(OMe)CH=CPh2} (PPh2Me)]PF6 (3) can undergo a clean attack by nucleophiles at least by two different pathways: (1) an unusual nucleophilic attack of primary, secondary, and tertiary amines at the sp3 carbon-oxygen bond, which gives an acyl complex and amine alkylation and (2) a nucleophilic attack of the ammonia at the carbenic carbon, which forms a primary aminocarbene.
- Talavera,Bolano,Bravo,Castro,Garcia-Fontan,Hermida-Ramon
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p. 4402 - 4408
(2013/09/02)
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- Synthesis and Structures of a Series of Bulky "Rind-Br" Based on a Rigid Fused-Ring s-Hydrindacene Skeleton
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A series of octa-R-substituted bromo-s-hydrindacenes, "Rind-Br," have been synthesized by a sequence of the Lewis acid catalyzed intramolecular FriedelCrafts reaction, bromination and vice versa. Their structural features and physical properties depend on
- Matsuo, Tsukasa,Suzuki, Katsunori,Fukawa, Tomohide,Li, Baolin,Ito, Mikinao,Shoji, Yoshiaki,Otani, Takashi,Li, Liangchun,Kobayashi, Megumi,Hachiya, Makoto,Tahara, Yoshiyuki,Hashizume, Daisuke,Fukunaga, Takeo,Fukazawa, Aiko,Li, Yongming,Tsuji, Hayato,Tamao, Kohei
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p. 1178 - 1191
(2012/01/31)
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- Nitrosonium salts, NO+X- (X = B(3,5-diCF 3Ph)4- or PW12O40 3-), as electrophilic catalysts for alkene activation in arene alkylation and dimerization reactions
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It has been found that in apolar reaction media the nitrosonium cation (NO+) activated alkenes under mild conditions toward electrophilic substitution of arene substrates to yield the alkylated arene with Markovnikov orientation. In the absence of arenes the alkenes react with themselves to yield a mixture of dimeric alkenes. The nitrosonium cation can be dissolved in the reaction medium by using the tetrakis-(bis-(3,5-trifluromethyl)phenyl) borate anion, where upon the reactions occur effectively at 30 °C. Alternatively an insoluble, heterogeneous catalyst was prepared so as to yield a NO+ cation with a polyoxometalate (PW12O403-) anion. This catalyst was generally more effective and selective toward a broader range of substrates at 70 °C. Copyright
- Khenkin, Alexander M.,Neumann, Ronny
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supporting information; scheme or table
p. 11876 - 11877
(2009/02/05)
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- An efficient and selective hydroarylation of styrenes with electron-rich arenes, catalyzed by bismuth(III) chloride and affording Markovnikov adducts
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In the presence of BiCl3, the hydroarylation of styrenes with electron-rich arenes afforded Markovnikov adducts selectively in good to high yields. Under arene-free conditions, the intermolecular hydroarylation of α-substituted styrenes and subsequent intramolecular hydroarylation produced the cyclic dimers of α-substituted styrenes in good yields. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Sun, Hong-Bin,Li, Biao,Hua, Ruimao,Yin, Gwu
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p. 4231 - 4236
(2007/10/03)
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- Indium(III) bromide-catalyzed chemioselective dimerization of vinylarenes
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Indium(III) bromide catalyzes the dimerization of α-substituted vinylarenes. Chemioselectivity towards open chain or cyclic dimers depends on the nature of the substituent at the aryl group of the vinylarene.
- Peppe, Clovis,Lang, Ernesto Schulz,De Andrade, Fabiano Molinos,De Castro, Liérson Borges
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p. 1723 - 1726
(2007/10/03)
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- Novel dimerization, alkoxylation, and sulfidation of olefins catalyzed by RuCl3·nH2O
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Novel ruthenium-catalyzed reactions that employ ruthenium trichloride n-hydrate (RuCl3·nH2O) were investigated and dimerization, alkoxylation and sulfidation of olefins were noted. Adducts of Markovnikov type and anti-Markovnikov type were obtained in a stereospecific manner and in good yield, depending on the type of olefins used as the starting materials. (Graph Presented).
- Higashimura, Mitsuteru,Imamura, Keita,Yokogawa, Yukiko,Sakakibara, Tsutomu
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p. 728 - 729
(2007/10/03)
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- Acid catalysis in the aminium hexachloroantimonate-induced cyclodimerization of 1-aryl-1-phenylethylenes
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The aminium hexachloroantimonate-induced cyclodimerization of various 1-aryl-1-phenylethylenes, affording regioisomeric indane derivatives via a carbocation mechanism, was found to occur in a similar manner when SbCl5 was used instead of the am
- Ciminale, Francesco,Lopez, Luigi,Farinola, Gianluca M.,Sportelli, Stefano,Nacci, Angelo
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p. 3850 - 3854
(2007/10/03)
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- Reactions of trimethylsilyl-derived iodohydrins with electron-rich π-systems
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Reactions of trimethylsilyl-derived iodohydrins of the type R1R2CH-CH(I)OTMS, with electron-rich olefins, and the effects of certain factors on these reactions, were studied. The trimethylsilyl-derived iodohydrins were obtained in situ by reacting R1R2CH-CHO (R1 = R2 = H; R1 = H, R2 = alkyl, phenyl) with TMSI. The corresponding trimethylsilyl enol ether derivatives (R1R2C=CH-OTMS), and 1,1-diarylethylenes were the olefins used. Aldehydes of the type RCH2-CH=O reacted smoothly in the presence of TMSI to yield the condensation product RCH2-CH=C(R)-CH=O. Both RCH(-CH=CAr2)2 and the cyclic acetal 5 were obtained as main products of the RCH=O-TMSI-CH2=CAr2 reaction system, depending on the [RCHO]:[TMSI]:[CH2=CAr2] concentration ratio. The mechanisms of formation for the various main products and by-products are discussed. TMSI substitutes, formed by reacting Me3SiCl with each of several Lewis acids, were also used.
- Ishai, Eti,Shamai, Sarit,Feit, Ben-Ami
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p. 434 - 438
(2007/10/03)
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- Carbon-carbon bond formation via oxidative-addition processes of titanium(II) reagents with π-bonded organic substrates. Reactivity modifications by Lewis acids and Lewis bases Part 22. Organic chemistry of subvalent transition metal complexes
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A series of titanium(II) derivatives, TiE2, was prepared by alkylative reduction of TiE4 by two equivalents of n-butyllithium in THF at -78 to 25°C (E = Cl, F, OBun, OPri and 0.5 NPh-CH2-CH2-NPh). The LiE by-product could usually be removed by THF evaporation and dissolution of the TiE2 into toluene. All such TiE2 derivatives were shown to effect the epimetallation and oligomerization of olefins, acetylenes and carbonyl derivatives in varying degrees. Particularly pertinent were the isolation and chemical reactions of titanium(II) isoproxide, the postulated intermediate in the Kulinkovich synthesis of cyclopropanols from ethyl Grignard reagents and organic esters, as well as an intermediate in many allied reactions developed by the Sato group. The findings of the present study corroborate completely the foregoing hypothesis that titanium(II) isopropoxide is the key intermediate in such novel reactions in organic synthesis. Furthermore, Ti(OPrl)2 can be prepared readily in a relatively pure state and has been found to react with 1-alkenes, alkynes and ketones by epimetallation at 25°C to form three-membered titanacycles, which can be utilized in organic synthesis. Finally, the ease with which such TiE2 derivatives epimetallate unsaturated organic substrates has been shown to be decreased by the steric demands of E and by the coordination of Lewis bases or donor solvent to the titanium(II) center. Lewis acids, on the other hand, greatly increase the rate of epimetallation by TiE2. A dramatic illustration of this effect is in the action of TiCl2·Me2AlCl on unsaturated hydrocarbons, wherein the polymerization of ethylene and of 1-alkene and the cyclotrimerization of alkynes are found to occur at room temperature.
- Eisch, John J.,Gitua, John N.,Otieno, Peter O.,Shi, Xian
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p. 229 - 238
(2007/10/03)
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- 1,1-Diphenylethylene adsorbed onto acid zeolites: Nature of the blue (605-nm) species
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Diffuse reflectance spectra of HY (Si/Al 15) and Hβ (Si/Al 13) zeolites after adsorption of 1,1-diphenylethylene (DPE) show an intense 605-nm absorption band characteristic of an elusive blue species observed a long time ago for DPE-silica-alumina solids. This blue species was wrongly attributed to the corresponding DPE+. radical cation or a complex of DPE with Lewis sites of these solids. In our case, EPR spectra of DPE samples adsorbed on HY and Hβ zeolites indicate that the spin population of these samples is too low (15 spin · g-1) to contain significant amounts of any paramagnetic species. In addition, IR spectra of the organic material incorporated within HY and Hβ is very similar to those of some DPE dimers. Product studies after solid-liquid extraction of zeolites and silica-alumina in which DPE has been adsorbed also show the formation of the corresponding dimers derived from the acid-catalyzed mechanism. Variable amounts of oxidation products are also formed when the adsorption is carried out in the open air. In addition, 13C-NMR spectra in solution of blue samples generated by treatment of DPE with sulfuric acid in dimethyl sulfate also indicate the presence of the same dimer distribution and the absence of detectable low-field signals that could be attributed to any carbenium ion. With these data, it is clear that in spite of the intense color developed in these samples, the bulk of the organic material adsorbed on the zeolites does not correspond to any intermediate, but to dimers. Semiempirical ROHF calculations using the ZINDO program provide some support to the possibility that the blue color could be due to 1,1,3,3-tetraphenyl-1-butylium cation, the reaction intermediate involved in the DPE dimerization mechanism.
- Fornes, Vicente,Garcia, Hermenegildo,Jovanovic, Slobodan,Marti, Vicente
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p. 4715 - 4726
(2007/10/03)
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- Electrophilic additions to styrylsilanes: the effect of changing the ligands on silicon
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Styrylsilanes readily undergo addition of carbon electrophiles and protons.The products of the reaction depend upon the non-participating substituents on silicon.Thus, while (E)-β-(trimethylsilyl)styrene 4 readily reacts with electrophiles, the reaction products did not contain silicon or new C-C bonds; even in the presence of aryl-substituted carbon electrophiles, the favored reaction was protiodesilylation.In contrast, (E)-β-(trichlorosilyl)styrene 2 did not participate in the reaction with carbon electrophiles or reasonably strong protic acids.However, with triflic acid, 2 cleanly and diastereoselectively dimerized producing after methylation 25, as shown by an X-ray crystal sructure analysis.The simple change of a methyl for a chloro group 3 under the same conditions produced a different diastereomer 19 along with a trimer 21.The reasons for the changes in reaction mechanism are discussed. β-effect / electrophilic addition / styrylsilane / leaving group ability / ligand effect / diastereoselective indane synthesis
- Brook, Michael A.,Henry, Courtney,Jefferson, Elizabeth,Jueschke, Ralf,Sebastian, Thomas,et al.
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p. 559 - 568
(2007/10/02)
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- Reactions on Aromatic Olefins Induced by Aminium Salts: Protic-Acid or Radical Cation Catalyzed Processes
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Aromatic olefins by reaction with aminium salts lead, in strongly acidic reaction media, to different reaction products, arising from the intermediate formation of carbocation or radical-cation species.
- Ciminale, Francesco,Lopez, Luigi,Mele, Giuseppe
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p. 12685 - 12696
(2007/10/02)
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- N-Fluorobisimides: Reactions with Some Olefins via α-Fluoro Carbocationic Intermediates
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N-Fluorobisimides are a new class of electrophilic fluorinating agents.Reaction of (CF3SO2)2NF (1) with olefins gave various products, depending on the reaction conditions and the structure of the substrate.In solvents of higher nucleophilicity such as H2O, acetic acid, aqueous HCl, and (HF)nPy, α-fluorohydrins and their acetates, α,β-chlorofluoro- and α,β-difluoroalkanes were obtained.In acetic acid, trans-stilbene and tetraphenylethylene produced the rearranged, nonfluorinated aldehyde and ketone.Evidence is presented for the reactions proceeding via a one-electron transfer mechanism involving α-fluorocarbocationic intermediates.
- DesMarteau, Darryl D.,Xu, Ze-Qi,Witz, Michael
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p. 629 - 635
(2007/10/02)
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- Reactions of electrophilic transition metal cations with olefins and small ring compounds. Rearrangements and polymerizations
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The reactivity of the cationic, weakly ligated, tranisition metal compounds, (BF4)2 (1); (BF4)2, (M = Ni, 2; Co, 3); (BF4)2, (M = Mo, 4; W, 5), vis-a-vis olefins and strained ring compounds was studied.A number of these species were observed to form a charge-transfer complex with tetra-p-anisylethylene.These compounds were also found to catalyze the skeletal rearrangement and polymerization of appropriately substituted olefins and cyclopropanes.These reactions appear to be initiated by the electrophilic (heterolytic) cleavage of either the ?-bond of the olefin or a strained C-C ?-bond of the small ring compound.
- Sen, Ayusman,Lai, Ta-Wang,Thomas, Richard R.
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p. 567 - 588
(2007/10/02)
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- Reactions of 1,1-Diphenylethylene and Its Derivatives with Tris(p-bromophenyl)aminium Hexachloroantimonate
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Reaction of 1,1-diphenylethylene (1) with (p-BrC6H4)3N*+SbCl6- produced indan dimer 2 in dried solvents and gave a butadiene derivative 7 and a tetrahydrofuran derivative 8 in wet solvents whereas the dimerization of the derivatives of 1 afforded cyclobutane type dimers and butadiene type dimers.
- Kim, Kwan Soo,Son, Se Hwan,Joo, Yung Hyup,Jung, Dai Il,Hahn, Chi Sun
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p. 2251 - 2252
(2007/10/02)
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- Chemistry of Weakly Solvated Lanthanide-Metal Cations. Synthesis, Characterization, and Catalytic Chemistry of x
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The title compound, x, 1, was synthesized by the NOBF4 oxidation of metallic Eu in CH3CN.The interaction of the BF4- ions with the Eu(III) center was established by molecular weight, conductivity, and 11B and 19F NMR spectral measurements. 1 was found to exist as a dimer in CH3CN.In addition, it behaved as a 1:2 electrolyte, indicating the coordination of two of the BF4- ions per Eu(III) ion.However, the conductivity increased when chelating amines were added due to the partial displacement of the coordinated BF4- ions.The 11B and 19F NMR spectra of 1 in CH3CN indicated the presence of two different types of BF4- anions, one of which was isotropically shifted due to interaction with the paramagnetic Eu(III) center.The coordinated BF4- anions could be displaced quantitatively by the addition of 2 equiv of NO3- ions per Eu(III) ion.A degenerate metathesis of the fluorine between the BF3 and the coordinated BF4- ions was observed when BF3 was added to a CH3CN solution of 1. 1 formed a charge-transfer complex with tetra-p-anisylethylene in CH3NO2 but not in CH3CN.In addition, 1 initiated the oligomerization and the polymerization of styrene, α-methylstyrene, and 1,3-cyclohexadiene in CH3NO2.The molecular weights of the polymers obtained increased markedly on lowering the reaction temperature.At room temperature, indan derivatives were obtained from α-methyl- and α-phenylstyrene.The rate of polymerization of styrene was markedly attenuated when CH3CN was used instead of CH3NO2. 1 also initiated the isomerization of quadricyclane and the ring-opening polymerization of 2(10)-pinene and cyclopropylbenzene in CH3NO2.
- Thomas, Richard R.,Chebolu, Venkatasuryanarayana,Sen, Ayusman
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p. 4096 - 4103
(2007/10/02)
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- Cationic Polar Cycloadditions of Phenylthionium Ions with Olefines: A New Route to Thiochromans
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Reaction of 2-chloro-N,N-dimethyl-2-(phenylthio)acetamide (1a) with styrene in the presence of stannic chloride gave 3,4-dihydro-N,N-dimethyl-4-phenyl-2H-1-benzothiopyran-2-carboxamide.The same benzothiopyran was also obtained from N,N-dimethyl-2-(phenylsulfinyl)acetamide and styrene under the Pummerer reaction conditions, but in lower yield.Similarly, α-chlorosulfides derived from ethyl 2-(phenylthio)acetate, 2-(phenylthio)acetonitrile, 1-(phenylthio)-2-propanone, and thioanisole reacted with styrene to give the corresponding 4-phenylbenzothiopyrans in variable yields.The reaction of 1a with trans-stilbene gave the expected benzothiopyran derivative, but the reaction of 1a with 1,1-diphenylethylene and phenylacetylene showed some variation of the reaction course.This cycloaddition reaction was extended to the intramolecular case.A possible mechanism for the formation of the benzothiopyran is discussed.
- Ishibashi, Hiroyuki,Okada, Motofumi,Sato, Kazumi,Ikeda, Masazumi,Ishiyama, Ko-ichi,Tamura, Yasumitsu
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- Reductive Alkylation/Arylation of Arylcarbinols and Ketones with Organosilicon Compounds
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Arylcarbinols react with certain organosilanes in the presence of boron trifluoride to yield hydrocarbons resulting from transfer of an R group from silicon to carbon.The transfer works well with aryl- and allylsilanes and fails with alkylsilanes.Allylation of ionizable carbinols is sometimes accompanied by cation-mediated oligomerization.This can be offset by converting the carbinols in question to their respective allyldimethylsilyl ethers followed by rearrangement of the ethers with BF3.While diaryl ketones are sluggishly bisallylated, the corresponding ketals undergo smooth bisallylation at 0 deg C with allytrimethylsilane/BF3/CH2Cl2.
- Cella, J. A.
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p. 2125 - 2130
(2007/10/02)
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- Oxidative Desilylation of Alkylsilanes with Triphenylcarbenium Ion. Control of Transition-State Geometry
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Ten acylic, cyclic, and aralkyl-type silanes were treated with triphenylcarbenium tetrafluoroborate in dichloromethane to measure rates of oxidative desilylation: RCH2CH2SiR3+Ph3C(1+)BF4(1-)->Ph3CH+RCH=CH2+R3SiF+BF3.The divergence of rates, from Ph2CHCH2SiMe3, which was inert, through dimethylsilacyclopentane (k2=4E-6), to dimethylsilacyclohexane (k2=2.2E-3), can not be rationalized on purely electronic grounds.A transition state requiring anticoplanar arrangement of the silicon moiety and β-hydrogen to be extruded is proposed.Dimethylsilacyclobutane, which reacts extremely rapidly (k2 approx. 2E-2), suffers allylic cleavage of the initially formed fluoro(2-propenyl)dimethylsilane.As the olefin products suffer decomposition or polymerization under the reaction conditions, this desilylation is of minimal preparative value.
- Washburne, Stephen S.,Szendroi, Robert
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p. 691 - 693
(2007/10/02)
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- REACTION OF BENZENE WITH PHENYLACETYLENE IN THE PRESENCE OF H3PO4*BF3
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In contrast to the known reactions of phenylacetylene with aromatic compounds, which lead to the formation of a mixture of phenylarylethylenes and phenyldiarylethanes, the reaction of benzene with phenylacetylene gives high yields of either 1-methyl-1,3,3-triphenylindane (III) or 1-methyl-1,3-diphenylindene (IV), depending on the conditions.In addition to the above-mentioned compounds, 1,1-diphenylethylene (I) and its dimer, 1,1,3,3-tetraphenyl-1-butene (II) were found in the reaction products.
- Ryabov, V. D.,Korobkov, V. Yu.
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p. 337 - 340
(2007/10/02)
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