- Relative activity of metal cathodes towards electroorganic coupling of CO2 with benzylic halides
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Electrochemical reduction of benzylic halides represents a convenient route to generating carbanions for their subsequent coupling with CO2 to obtain various carboxylic acids. Despite the industrial prospects of this synthetic process, it still lacks systematic studies of the efficient catalysts and reaction media design. In this work, we performed a detailed analysis of the catalytic activity of a series of different metal electrodes towards electroreduction of benzylic halides to corresponding radicals and carbanions using cyclic voltammetry. Specifically, we screened and summarized the performance of 12 bulk metal cathodes (Ag, Au, Cu, Pd, Pt, Ni, Ti, Zn, Fe, Al, Sn, and Pb) and 3 carbon-based materials (glassy carbon, carbon cloth, and carbon paper) towards electrocarboxylation of eight different benzylic halides and compare it to direct CO2 reduction in acetonitrile. Extensive experimental studies along with a detailed analysis of the results allowed us to map specific electrochemical properties of different metal electrodes, i.e., the potential zones related to the one- and two-electron reduction of organic halides as well as the potential windows where the electrochemical activation of CO2 does not occur. The reported systematic analysis should facilitate the development of nanostructured electrodes based on group 10 and 11 transition metals to further optimize the efficiency of electrocarboxylation of halides bearing specific substituents and make this technology competitive to current synthetic methods for the synthesis of carboxylic acids.
- Engelhardt, Helen,Klinkova, Anna,Medvedev, Jury J.,Medvedeva, Xenia V.
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- Synthetic method of fatty acid containing nitrogen heterocycle
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The invention discloses a synthetic method of fatty acid containing nitrogen heterocycle. The synthetic method comprises the following steps: (S1) adding a heterocyclic compound with substitution of chloromethyl groups, a catalyst and a solvent DMF into a reaction kettle; (S2) introducing carbon dioxide to lead the pressure in the kettle to be 2-4MPa, adjusting and reacting for 10-16 hours at thetemperature of 40-50 DEG C; (S3) adding diluted hydrochloric acid into the reaction kettle to carry out acidification, using ethyl acetate for extraction, combining organic phases, carrying out rotaryevaporation to remove liquid, and further carrying out vacuum drying, thus obtaining the fatty acid containing nitrogen heterocycle. The synthetic method disclosed by the invention has the beneficialeffects that a one-pot method is adopted, the raw materials are easy to obtain, price is low, aftertreatment of products is also simpler, the universality for a substrate is also very high, and the promotion and application are easy.
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Paragraph 0042
(2018/07/30)
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- Multifunctional catalysis promoted by solvent effects: Ti-mcm41 for a one-pot, four-step, epoxidation-rearrangement-oxidation-decarboxylation reaction sequence on stilbenes and styrenes
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Titanium sites grafted on several siliceous supports are able to act as multifunctional catalytic centers, activating tert-butyl hydroperoxide for oxidation reactions, as redox centers, and promoting rearrangements, as Lewis acids. In the one-pot, four-step conversion of stilbene into benzophenone, the best results were obtained over Ti-MCM41. Under suitable conditions, the catalyst promotes a tandem sequence: alkene epoxidation, epoxide rearrangement, aldehyde oxidation, and oxidative decarboxylation. α,α,α-Trifluorotoluene and a fluorinated glycerol-derived solvent were the optimal solvents for this tandem process, due to their polar aprotic character that allows the efficient oxidation reactions and a poor coordinating ability to prevent any deactivation of the Lewis acid character of the sites. The result of the tandem sequence of reactions is a ketone with loss of a carbon atom that, depending on the starting alkene, is the same result as that of an ozonolysis but under safer and milder conditions. Interesting and new insights on the mechanism of the different reactions involved are also described.
- Fraile, José M.,García, Nuria,Mayoral, José A.,Santomauro, Fabio G.,Guidotti, Matteo
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p. 3552 - 3561
(2015/06/16)
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- Ni-catalyzed direct carboxylation of benzyl halides with CO2
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A novel Ni-catalyzed carboxylation of benzyl halides with CO2 has been developed. The described carboxylation reaction proceeds under mild conditions (atmospheric CO2 pressure) at room temperature. Unlike other routes for similar means, our method does not require well-defined and sensitive organometallic reagents and thus is a user-friendly and operationally simple protocol for assembling phenylacetic acids.
- León, Thierry,Correa, Arkaitz,Martin, Ruben
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supporting information
p. 1221 - 1224
(2013/03/14)
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- Siloxyl ether functionalized resins for chemoselective enrichment of carboxylic acids
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Although the carboxylic acid moiety is prevalent in many biologically produced molecules, including natural products and proteins, methods to chemoselectively target this functional group have remained elusive. Generally, strategies that utilize carboxylate nucleophilicity also promote reactions with other nucleophiles such as amines and hydroxyls. A reagent was sought to facilitate the selective isolation of carboxylic acid containing compounds from complex mixtures. Here, the development of siloxyl ether functionalized solid supports is described.
- Trader, Darci J.,Carlson, Erin E.
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supporting information; experimental part
p. 5652 - 5655
(2011/12/04)
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- Triarylmethanes and 9-arylxanthenes as prototypes amphihydric compounds for relating the stabilities of cations, anions and radicals by C-H bond cleavage and electron transfer
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Thermodynamic stability properties of 11 p-substituted trityl and seven 9-phenylxanthyl carbocations are reported in sulfolane and of their conjugate carbanions in DMSO. The cations are compared by calorimetric heats of hydride transfer from cyanoborohydride ion, their first and second reduction potentials, their pK+Rs in aqueous sulfuric acid, 13C chemical shifts and free energies of methoxy exchange. Carbanions are compared by their heats and free energies (pKHA) of deprotonation and their first and second oxidation potentials. Radicals are compared by their oxidation and reduction potentials. Their bond dissociation energies are derived by alternative routes: from the carbocation and its reduction potential and from the carbanion and its oxidation potential. The various properties are correlated against each other and against appropriate Hammett-type substituent parameters. Correlations between the different measured properties reported here range from fair to excellent. Despite their importance as historic prototypes for the three trivalent oxidation states of carbon, trityl and xanthyl systems are atypical models for comparing transmission of electron demand in other series of carbocations, radicals or carbanions with significantly different structures. The 9-arylxanthyl series is especially poor because of its insensitivity to substituent effects. The effects of substituents on various properties which represent the stabilities of R+s correlate surprisingly well against those for corresponding R-s. Accordingly, compensating effects on the oxidation and reduction of a series of related R.s may lead to a nearly constant electron transfer energy and absolute hardness for the series. In contrast, the free energies for interconversion of the carbocations and carbanions which determine the gap between pKR+. and pKHA are very sensitive to structural change.
- Arnett, Edward M.,Flowers II, Robert A.,Ludwig, Richard T.,Meekhof, Alison E.,Walek, Stuart A.
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p. 499 - 513
(2007/10/03)
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- N-acyl sulfamic acid esters (or thioesters), N-acyl sulfonamides, and N-sulfonyl carbamic acid esters (or thioesters) as hypercholesterolemic agents
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The present invention is directed to compounds useful for the regulation of cholesterol of Formula I, methods for using them and pharmaceutical compositions thereof, STR1 wherein X and Y are oxygen, sulfur, or (CR'R")n wherein n is 1 to 4; R is hydrogen, alkyl, or benzyl; R1 and R2 are phenyl, substituted phenyl, naphthyl, substituted naphthyl, an aralkyl group, an alkyl chain, adamantyl, or a cycloalkyl group.
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- Studies on the B(AL)2 mechanism for esther hydrolysis
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The preparation and alkaline hydrolysis of 18O-methyl 2,2-dimethylpropanoate and 18O-methyl triphenylacetate are reported. From mass spectral analysis of the carboxylic acid products, it is concluded that the former substrate is hydrolyzed exclusively by the B(AC)2 mechanism, whereas the latter substrate proceeds 95% by the B(AC)2 mechanism and 5% by the B(AL)2 mechanism. The balance between these two mechanisms is discussed.
- Douglas,Campbell,Wigfield
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p. 1841 - 1844
(2007/10/02)
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- The photochemistry of mixed anhydrides: A search for selectivity in photochemically initiated bond cleavage reactions
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A number of mixed anhydrides (RC(O)OC(O)R') have been synthesized for the purpose of exploring the regioselectivity of their photochemical reactions. The photochemical reaction products, quantum yields, and reaction rates have been determined. For those compounds containing no α-hydrogens, high regioselectivity is obtained upon irradiation and can be understood on the basis of the relative C-O bond dissociation energies. The reaction can be quenched by intramolecular electron transfer. For those compounds containing α-hydrogen atoms, the Norrish type II reaction is faster than the corresponding C-O cleavage reactions, resulting in poor regioselectivity.
- Penn, John H.,Owens, Walter H.
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