- Synthesis of Distorted 1,8,13-Trisilyl-9-hydroxytriptycenes by Triple Cycloaddition of Ynolates to 3-Silylbenzynes
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1,8,13-Trialkyl(aryl)silyl-9-hydroxytriptycenes (trisilyltriptycenes) were synthesized by the triple addition of ynolates and 3-silylbenzynes with high regioselectivity. Benzene rings in the resulting triptycenes were highly distorted where the dihedral a
- Yoshinaga, Tatsuro,Fujiwara, Takumi,Iwata, Takayuki,Shindo, Mitsuru
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- Oxidative 1,2-Difunctionalization of Ethylene via Gold-Catalyzed Oxyarylation
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Under the conditions of oxidative gold catalysis, exposure of ethylene to aryl silanes and alcohols generates products of 1,2-oxyarylation. This provides a rare example of a process that allows catalytic differential 1,2-difunctionalization of this feedstock chemical.
- Harper, Matthew J.,Emmett, Edward J.,Bower, John F.,Russell, Christopher A.
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supporting information
p. 12386 - 12389
(2017/09/22)
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- Cationic Chiral Fluorinated Oxazaborolidines. More Potent, Second-Generation Catalysts for Highly Enantioselective Cycloaddition Reactions
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The coordination of chiral ligands to Lewis acid metal derivatives, a useful strategy for enantioselective, electrophilic catalysis, generally leads to a lower level of catalytic activity than that of the original uncomplexed compound. Activation by furth
- Mahender Reddy, Karla,Bhimireddy, Eswar,Thirupathi, Barla,Breitler, Simon,Yu, Shunming,Corey
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p. 2443 - 2453
(2016/03/08)
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- Substituent effects on the relative rates and free energies of ortholithiation reactions: Families of fluorobenzenes as the substrates
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2-, 3- and 4-substituted fluorobenzenes and 5-substituted 1,3-difluorobenzenes were metalated with sec-butyllithium (LIS) and with lithium 2,2,6,6-tetramethylpiperidide (LiTMP) under irreversible conditions in order to determine the rates of reaction rela
- Mongin, Florence,Curty, Christophe,Marzi, Elena,Leroux, Frdric R.,Schlosser, Manfred
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- Remote trimethylsilyl groups interfering with the ortho deprotonation of fluoroarenes and chloroarenes
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(2-Fluorophenyl)trimethylsilane (2-F) and (2-chlorophenyl)-trimethylsilane (2-Cl) react with sec-butyllithium or lithium 2,2,6,6-tetramethylpiperidide under permutational hydrogen/metal interconversion (metalation) more slowly than, respectively, the corr
- Heiss, Christophe,Marzi, Elena,Mongin, Florence,Schlosser, Manfred
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p. 669 - 675
(2007/10/03)
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- Fluoronaphthalene building blocks via arynes: A solution to the problem of positional selectivity
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When 3-fluoro- and 3-chloro-1,2-didehydrobenzenes are generated in the presence of 2-(trimethylsilyl)furan, two regioisomeric cycloadducts are formed in a 1:2 ratio. However, regioselectivity can be installed by fitting one bulky trimethylsilyl group into sterically critical positions of each of the two reaction components. Thus 3-fluoro-6-trimethylsilyl-1,2-didehydrobenzene and 2-(trimethylsilyl)furan give one cycloadduct exclusively. In this way, the Diels-Alder reaction between suitably adorned arynes and similarly designed furans can open an entry to naphthalene derivatives that have unprecedented substituent patterns that qualify them as building blocks for pharmaceutical or agricultural research. The acid-catalyzed isomerization of model 1,4-epoxy-1,4-dihydronaphthalenes, the aryne/furan cycloadducts, exhibits unexpected effects on rates and regioselectivity. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Masson, Eric,Schlosser, Manfred
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p. 4401 - 4405
(2007/10/03)
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- Reactions of trimethylstannide and trimethylsiliconide anions with aromatic and heteroarornatic substrates
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A parallel study was carried out on the reactions of Me3Sn- and Me3Si- ions towards aromatic and heteroaromatic substrates in hexamethylphosphoramide (HMPA) as solvent. It was found that Me3Si- ions are more reactive and therefore less selective than Me3Sn- ions. In HMPA, PhI and PhBr react with Me3Sn- ions through an HME pathway. PhCl also reacts by an HME reaction, but under photostimulation the SRN1 mechanism competes with the HME process, With PhF as sabstrate, Me3Sn- ions afford (4-fluorophenyl)trimethylstannane, presumably through a hypervalent tin species. Under irradiation, the SRN1 mechanism operates concurrently with the formation of the hypervalent tin species. Me3Si- ions, on the other hand, react with PhX (X = Cl, Br, I) to yield the ipso substitution product, presumably through the intermediacy of a hypervalent silicon species. PhF affords, upon reaction with Me3Si- ions, o- and p-fluorotrimethylsilylbenzenes together with the ipso substitution product PhSiMe3. A novel type of nucleophilic substitution mechanism takes place with Me3Si- ions upon reaction with aromatic and heteroaromatic substrates without classical leaving groups in HMPA. Copyright
- Postigo, Al,Vaillard, Santiago E.,Rossi, Roberto A.
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p. 889 - 893
(2007/10/03)
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- A novel type of nucleophilic substitution reactions on nonactivated aromatic compounds and benzene itself with trimethylsiliconide anions.
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[reaction: see text]. The reaction of fluorobenzene with Me3Si- anion (1) in HMPA at room temperature surprisingly affords o- and p-fluorotrimethylsilylbenzenes (substitution of aromatic H for TMS, 76% yield) 7a and 7b and also 14% of trimethylsilylbenzene (2). Benzene itself reacts at 50 degrees C to furnish 4 in 45% yield. Pyridine affords p-trimethylsilylpyridine quantitatively. Mechanistic studies are presented.
- Postigo,Rossi
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p. 1197 - 1200
(2007/10/03)
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- Fluorodesilylations of fluorophenyltrimethylsilanes with elemental fluorine: Discovery of a novel 1,2-migration of the trimethylsilyl group
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The main product in the direct elemental fluorination of 4-fluorophenyltrimethylsilane was 1,4-difluorobenzene, produced by the ipso electrophilic substitution of the trimethylsilyl group. An unexpected product, 2,5-difluorophenyltrimethylsilane, was also formed as the result of a novel 1,2-migration of the trimethylsilyl group. The same trimethylsilyl 1,2-shifts were observed in the elemental fluorinations of 2-fluoro-and 2,4-difluoro-phenyltrimethylsilanes. We propose that the carbocations formed in the rearrangements were stabilised by the mescineric effect of the α-fluorine and the greater stability of these intermediates provided the driving force for the trimethylsilyl group migrations. Although the main products in all of the fluorinations were the fluorodesilylated product, the reactions were not totally regioselective and some competing fluorodeprotonation also occurred in the reactions of 2-fluoro-and 2,4-difluoro-phenyltrimethylsilanes. The role of protic acids and Lewis acids in particular triflic acid, trifluoroacetic acid and boron trifluoride in a variety of co-solvents, respectively, was crucial in all the fluorinations we studied, experiments done in their absence gave very poor yields. Optimal conditions for fluorination of silylated substrates are described.
- Stuart, Alison M.,Coe, Paul L.,Moody, David J.
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p. 179 - 184
(2007/10/03)
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- Generation of ortho-Potassiofluorobenzene and its Functionalization
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A number of ortho-substituted fluorobenzenes are readily accessible by treating fluorobenzene at -100 deg C with 1:1 molar mixture of potassium tert-butoxide and n-butyllithium in tetrahydrofuran and hexane, and subsequently adding an electrophilic reagent.
- Fossatelli, M.,Verkruijsse, H.D.,Brandsma, L.
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p. 1701 - 1704
(2007/10/02)
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- Mechanism of Base-Catalyzed Desilylations of Aryl- and Heteroaryltrimethylsilanes
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The influence of different bases on the cleavage of silicium-carbon bonds in aryl- and heteroaryltrimethylsilanes is investigated in the presence of benzaldehyde as electrophilic scavenger for the aryl and heteroaryl anions formed in this process.A reactivity gradation of the various basic catalysts employed is determined from the reactions with 2-(trimethylsilyl)benzothiazole (1).The increase of catalytic activity of the anions parallels that of their ion potential.Attack of the base at the Si atom is postulated as the first step in this reaction sequence, with subsequent dissociation of the pentacoordinated intermediate in the rate-determining step.The carbanion thus liberated rapidly reacts with benzaldehyde.In the differently substituted aryltrimethylsilanes 13, 13', and 13'' the dependency of aryl anion stability in the base-catalyzed carbodesilylation was investigated.The relative rates of reaction correlate with Hammett's ?-constants rather than with the corresponding aryl anion stabilities.
- Effenberger, Franz,Spiegler, Wolfgang
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p. 3872 - 3899
(2007/10/02)
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