3247-00-5Relevant articles and documents
Stimuli responsive surfaces through recognition-mediated polymer modification
Xu, Hao,Norsten, Tyler B.,Uzun, Oktay,Jeoung, Eunhee,Rotello, Vincent M.
, p. 5157 - 5159 (2005)
Specific three-point hydrogen bonding between diamidopyridine (DAP) and thymine (Thy) was employed to reversibly anchor "brush-like" Tri-DAP end-functionalized polystyrene onto Thy-modified silica surfaces. The Royal Society of Chemistry 2005.
Fast Addition of s-Block Organometallic Reagents to CO2-Derived Cyclic Carbonates at Room Temperature, Under Air, and in 2-Methyltetrahydrofuran
Elorriaga, David,de la Cruz-Martínez, Felipe,Rodríguez-álvarez, María Jesús,Lara-Sánchez, Agustín,Castro-Osma, José Antonio,García-álvarez, Joaquín
, p. 2084 - 2092 (2021/04/02)
Fast addition of highly polar organometallic reagents (RMgX/RLi) to cyclic carbonates (derived from CO2 as a sustainable C1 synthon) has been studied in 2-methyltetrahydrofuran as a green reaction medium or in the absence of external volatile organic solvents, at room temperature, and in the presence of air/moisture. These reaction conditions are generally forbidden with these highly reactive main-group organometallic compounds. The correct stoichiometry and nature of the polar organometallic alkylating or arylating reagent allows straightforward synthesis of: highly substituted tertiary alcohols, β-hydroxy esters, or symmetric ketones, working always under air and at room temperature. Finally, an unprecedented one-pot/two-step hybrid protocol is developed through combination of an Al-catalyzed cycloaddition of CO2 and propylene oxide with the concomitant fast addition of RLi reagents to the in situ and transiently formed cyclic carbonate, thus allowing indirect conversion of CO2 into the desired highly substituted tertiary alcohols without need for isolation or purification of any reaction intermediates.
Shuttle arylation by Rh(I) catalyzed reversible carbon–carbon bond activation of unstrained alcohols
Lutz, Marius D.R.,Gasser, Valentina C.M.,Morandi, Bill
supporting information, p. 1108 - 1119 (2021/04/19)
The advent of transfer hydrogenation and borrowing hydrogen reactions paved the way to manipulate simple alcohols in previously unthinkable manners and circumvented the need for hydrogen gas. Analogously, transfer hydrocarbylation could greatly increase the versatility of tertiary alcohols. However, this reaction remains unexplored because of the challenges associated with the catalytic cleavage of unactivated C–C bonds. Herein, we report a rhodium(I)-catalyzed shuttle arylation cleaving the C(sp2)–C(sp3) bond in unstrained triaryl alcohols via a redox-neutral β-carbon elimination mechanism. A selective transfer hydrocarbylation of substituted (hetero)aryl groups from tertiary alcohols to ketones was realized, employing benign alcohols as latent C-nucleophiles. All preliminary mechanistic experiments support a reversible β-carbon elimination/migratory insertion mechanism. In a broader context, this novel reactivity offers a new platform for the manipulation of tertiary alcohols in catalysis.
Reactivity of mixed organozinc and mixed organocopper reagents: 12. Three component reaction of mixed (n-alkyl)(diaryl)zincates, chloroformates and phosphines for the synthesis of esters
?zkan, Duygu,Erdik, Ender
, p. 75 - 81 (2015/10/05)
The reaction of mixed n-butyldiphenylzincate, n-BuPh2ZnMgBr with ethyl chloroformate, ClCOOEt in the presence n-Bu3P in THF takes place with quantitative yield and phenyl group transfer to give PhCOOEt. Ethoxycarbonylation of n-BuPh2ZnMgBr is preferable to the reaction of PhMgBr forming ester and triphenylcarbinol and also to the reaction of triphenylzincate, Ph3ZnMgBr for atom economy. Group selectivity in the phosphine catalyzed C-COOR coupling of n-BuPh2ZnMgBr and n-Bu2PhZnMgBr can be controlled by changing reaction parameters. n-Bu3P catalyzed reaction of n-BuPh2ZnMgBr with ClCOOEt takes place with phenyl selectivity whereas reaction of n-Bu2PhZnMgBr with ClCOOPh results in n-butyl transfer. Catalysis by Ph3P increases n-butyl group:phenyl group transfer ratio in the ethoxycarbonylation of both zincates. Selective transfer of aryl groups in n-Bu3P catalyzed reaction of n-butyl(aryl)2ZnMgBr reagents with ClCOOEt in THF provides a new procedure for the organometallic synthesis of arenecarboxylic acid ethyl esters at room temperature.
MELANIN PRODUCTION INHIBITOR
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Paragraph 0258 - 0262, (2015/12/17)
Disclosed is a melanin production inhibitor which has an excellent inhibitory activity on the production of melanin and is highly safe. The melanin production inhibitor is represented by general formula (1) (excluding clotrimazole) and/or a pharmacologically acceptable salt thereof. In the formula, A1, A2 and A3 are independently selected from a hydrogen atom, an aryl group which may have a substituent, and an aromatic heterocyclic group which may have a substituent. At least one of A1, A2 and A3 is selected from the aryl group and the aromatic heterocyclic group, the total number of carbon atoms contained in A1, A2 and A3 is 6 to 50 and, when at least two of A1, A2 and A3 represent the aryl groups or the aromatic heterocyclic groups, the adjacent two aryl or aromatic heterocyclic groups may be bound to each other via an alkyl chain or an alkenyl chain to form a ring; m represents an integer of 0 to 2; X represents a hetero atom, a hydrogen atom, or a carbon atom; R1 and R2 are independently selected from a hydrogen atom and an oxo group. When one of R1 and R2 is an oxo group, the other is not present. R3 is selected from a hydrogen atom, and a C1-8 hydrocarbon group in which one or some of hydrogen atoms or carbon atoms may be substituted by a hetero atom or hetero atoms. The number of R3's present in the compound corresponds to X and, when two or more R3's are present, the R3's are independently present and the adjacent two R3's may be bound to each other to form, together with X, a ring, and the terminal of R3 may be bound to a carbon atom to which A1, A2 and A3 are bound, thereby forming a ring.
MELANIN PRODUCTION INHIBITOR
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, (2011/10/13)
Disclosed is a melanin production inhibitor which has an excellent inhibitory activity on the production of melanin and is highly safe. The melanin production inhibitor comprises a compound represented by general formula (1) (excluding clotrimazole), and/or a pharmacologically acceptable salt thereof. In the formula, A1, A2 and A3 are independently selected from a hydrogen atom, an aryl group which may have a substituent, and an aromatic heterocyclic group which may have a substituent, wherein at least one of A1, A2 and A3 is selected from the aryl group and the aromatic heterocyclic group, the total number of carbon atoms contained in A1, A2 and A3 is 6 to 50 and, when at least two of A1, A2 and A3 represent the aryl groups or the aromatic heterocyclic groups, the adjacent two aryl or aromatic heterocyclic groups may be bound to each other via an alkyl chain or an alkenyl chain to form a ring; m represents an integer of 0 to 2; X represents a hetero atom, a hydrogen atom, or a carbon atom; R1 and R2 are independently selected from a hydrogen atom and an oxo group, wherein when one of R1 and R2 is an oxo group, the other is not present; and R3 is selected from a hydrogen atom, and a C1-8 hydrocarbon group in which one or some of hydrogen atoms or carbon atoms may be substituted by a hetero atom or hetero atoms, wherein the number of R3's present in the compound corresponds to the number of X's and, when two or more R3's are present, the R3's are independently present and the adjacent two R3's may be bound to each other to form, together with X, a ring, and the terminal of R3 may be bound to a carbon atom to which A1, A2 and A3 are bound, thereby forming a ring.
Electrophilicity versus electrofugality of tritylium ions in aqueous acetonitrile
Horn, Markus,Mayr, Herbert
supporting information; scheme or table, p. 7478 - 7487 (2010/08/20)
First-order rate constants kw for the reactions of a series of donorsubstituted triphenylmethylium (tritylium) ions with water in aqueous acetonitrile have been determined photometrically at 20°C using stopped-flow and laser-flash techniques. T
Stabilities of trityl-protected substrates: The wide mechanistic spectrum of trityl ester hydrolyses
Horn, Markus,Mayr, Herbert
supporting information; experimental part, p. 7469 - 7477 (2010/09/11)
Ionization rates of para-substituted triphenylmethyl (trityl) acetates, benzoates, and para-nitrobenzoates have been determined in aqueous acetonitrile and aqueous acetone at 25 °C. Conventional and stoppedflow techniques have been used to evaluate rate constants ranging from 1.38 × 10-5 to 2.15 × 102S-1 by conductimetry and photospectrometry methods. The varying stabilities of the differently substituted tritylium ions account for a gradual change of reaction mechanism. Poorly stabilized carbocations are generated slowly by the ionization of their covalent precursors and trapped fast by water. Better stabilized carbocations are generated more rapidly and accumulate, so that ionization and trapping by water can be observed as separate steps in a single experiment. Finally, highly stabilized tritylium ions do not react with water, and only the rates of their formation could be measured. The ionization rate constants correlate linearly with Winstein's ionizing powers Y; the low slopes (0.17 + parameters is excellent for symmetrically substituted tritylium derivatives, deviations for unsymmetrically substituted systems are observed. The failing rate-equilibrium relationship between the rates of ionizations (log kion) and the stabilities of the carbocations in aqueous solution (pKR+) may be explained by the late " development of resonance between a p-amino group and the carbocationic center of the tritylium ion during the ionization process.
Triaryl methane derivatives as antiproliferative agents
Al-Qawasmeh, Raed A.,Lee, Yoon,Cao, Ming-Yu,Gu, Xiaoping,Vassilakos, Aikaterini,Wright, Jim A.,Young, Aiping
, p. 347 - 350 (2007/10/03)
Clotrimazole (CLT) 1, a synthetic anti-fungal imidazole derivative, inhibits tumor cell proliferation and angiogenesis. In the current study, flow cytometric analysis demonstrated that the decrease in tumor cell growth by CLT 1 was associated with inhibition of cell cycle progression at the G 1-S phase transition, resulting in G0-G1 arrest. A series of CLT 1 analogues has been generated in order to develop CLT 1 derivatives that are devoid of the imidazole moiety which is responsible for the hepatoxicity associated with CLT 1 while retaining CLT 1 efficacy. The majority of these analogues demonstrate in vitro antiproliferative activity ranging from submicromolar to micromolar concentrations.
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
Arnett, Edward M.,Flowers II, Robert A.,Ludwig, Richard T.,Meekhof, Alison E.,Walek, Stuart A.
, p. 499 - 513 (2007/10/03)
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.
