- Site-Specific Alkene Hydromethylation via Protonolysis of Titanacyclobutanes
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Methyl groups are ubiquitous in biologically active molecules. Thus, new tactics to introduce this alkyl fragment into polyfunctional structures are of significant interest. With this goal in mind, a direct method for the Markovnikov hydromethylation of alkenes is reported. This method exploits the degenerate metathesis reaction between the titanium methylidene unveiled from Cp2Ti(μ-Cl)(μ-CH2)AlMe2 (Tebbe's reagent) and unactivated alkenes. Protonolysis of the resulting titanacyclobutanes in situ effects hydromethylation in a chemo-, regio-, and site-selective manner. The broad utility of this method is demonstrated across a series of mono- and di-substituted alkenes containing pendant alcohols, ethers, amides, carbamates, and basic amines.
- Bartfield, Noah M.,Frederich, James H.,Law, James A.
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supporting information
p. 14360 - 14364
(2021/05/27)
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- Highly selective conversion of guaiacol to: Tert -butylphenols in supercritical ethanol over a H2WO4 catalyst
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The conversion of guaiacol is examined at 300 °C in supercritical ethanol over a H2WO4 catalyst. Guaiacol is consumed completely, meanwhile, 16.7% aromatic ethers and 80.0% alkylphenols are obtained. Interestingly, tert-butylphenols are produced mainly with a high selectivity of 71.8%, and the overall selectivity of 2,6-di-tert-butylphenol and 2,6-di-tert-butyl-4-ethylphenol is as high as 63.7%. The experimental results indicate that catechol and 2-ethoxyphenol are the intermediates. Meanwhile, the WO3 sites play an important role in the conversion of guaiacol and the Br?nsted acid sites on H2WO4 enhance the conversion and favour a high selectivity of the tert-butylphenols. The recycling tests show that the carbon deposition on the catalyst surface, the dehydration and partial reduction of the catalyst itself are responsible for the decay of the H2WO4 catalyst. Finally, the possible reaction pathways proposed involve the transetherification process and the alkylation process during guaiacol conversion.
- Mai, Fuhang,Cui, Kai,Wen, Zhe,Wu, Kai,Yan, Fei,Chen, Mengmeng,Chen, Hong,Li, Yongdan
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p. 2764 - 2771
(2019/02/01)
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- A template-free approach to nanotube-decorated polymer surfaces using 3,4-phenylenedioxythiophene (PhEDOT) monomers
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In this work, novel 3,4-phenylenedioxythiophene (PhEDOT) monomers with alkyl, branched, and aromatic substituents were synthesized and tested for their efficacy at forming surfaces with unique wetting properties and surface morphology without the aid of surfactants. Monomers with a naphthalene substituent clearly showed the highest capacity to stabilize gas bubbles (O2 or H2) formed in solution during electrodeposition from trace water, resulting in the formation of nanotubes. Variation in the resulting density, diameter, and height of nanotubes was demonstrated by varying the electropolymerization protocol, conditions, or electrolyte used. The wetting induced by the nanotube formation results in the surfaces formed having both high contact angles with water (W) and strong adhesion, despite all polymers being intrinsically hydrophilic. This one-step and easily tunable approach to nanotube formation has potential to advance applications in membrane design, water transport and harvesting, as well as sensor design.
- Szczepanski, Caroline R.,M'Jid, Inès,Darmanin, Thierry,Godeau, Guilhem,Guittard, Frédéric
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p. 17308 - 17323
(2016/11/18)
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- Mechanistic studies of the free-radical fragmentation of monoalkyl diazenes
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Mechanistic studies of the deoxygenation of primary alcohols by Mitsumobu displacement with o-nitrobenzenesulfonylhydrazine (NBSH) reveal that the monoalkyl diazene intermediates formed in this process are exceedingly good hydrogen-atom donors toward alkyl radicals, exceeding tri-n-butylin hydride in reactivity. Competition experiments are described wherein the radical intermediates are trapped by intra- and intermediate addition to carbon-carbon double bonds, to dioxygen, and to the free radical 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO).
- Myers, Andrew G.,Movassaghi, Mohammad,Zheng, Bin
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p. 6569 - 6572
(2007/10/03)
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- The E.S.R. Spectra of Cation Radicals Derived from Phenethyltetrahydroisoquinoline Ethers and Model Compounds
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Cation radicals derived from the title compounds by oxidation with thallium tristrifluoroacetate have been characterized.The structures assigned to these radicals suggest that initial oxidation occures at the phenethyl ring in the compounds examined.Oxidation of homolaudanosine in this way gave the expected homoaporphine.
- Hewgill, Frank R.,Pass, Michael C.
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p. 555 - 563
(2007/10/02)
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- REACTION OF o-BENZOQUINONE BISACETALS WITH ORGANOLITHIUMS. A NOVEL ROUTE TO SUBSTITUTED VERATROLES
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Substituted veratroles were easily obtained by the reaction of o-benzquinone bisacetals with organolithiums.
- Kikuchi, Yoshiyuki,Hasegawa, Yoko,Matsumoto, Masakatsu
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p. 2199 - 2202
(2007/10/02)
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