- Remarkably Efficient Iridium Catalysts for Directed C(sp2)-H and C(sp3)-H Borylation of Diverse Classes of Substrates
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Here we describe the discovery of a new class of C-H borylation catalysts and their use for regioselective C-H borylation of aromatic, heteroaromatic, and aliphatic systems. The new catalysts have Ir-C(thienyl) or Ir-C(furyl) anionic ligands instead of the diamine-type neutral chelating ligands used in the standard C-H borylation conditions. It is reported that the employment of these newly discovered catalysts show excellent reactivity and ortho-selectivity for diverse classes of aromatic substrates with high isolated yields. Moreover, the catalysts proved to be efficient for a wide number of aliphatic substrates for selective C(sp3)-H bond borylations. Heterocyclic molecules are selectively borylated using the inherently elevated reactivity of the C-H bonds. A number of late-stage C-H functionalization have been described using the same catalysts. Furthermore, we show that one of the catalysts could be used even in open air for the C(sp2)-H and C(sp3)-H borylations enabling the method more general. Preliminary mechanistic studies suggest that the active catalytic intermediate is the Ir(bis)boryl complex, and the attached ligand acts as bidentate ligand. Collectively, this study underlines the discovery of new class of C-H borylation catalysts that should find wide application in the context of C-H functionalization chemistry.
- Chattopadhyay, Buddhadeb,Hassan, Mirja Md Mahamudul,Hoque, Md Emdadul
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supporting information
p. 5022 - 5037
(2021/05/04)
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- ANALGESIC AND ANTI-ADDICTIVE COMPOSITIONS FOR TREATMENT OF CHRONIC PAIN AND OPIOID ADDICTION
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The invention provides a compound of formula I and stereoisomers, tautomers, or pharmaceutically acceptable salts thereof, and with the substituents and structural features described herein. Also described are pharmaceutical compositions and medicaments t
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Page/Page column 28; 29
(2020/06/10)
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- Synthesis of 2-arylquinazolin-4(3H)-ones by N-aryl benzamidines with aromatic carbonates
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The reaction of N-aryl benzamidines 1a, 1b, 1c, 1d, 1e, 1f, 1g, 1h, 1i, 1j, 1k, 1l, 1m, 1n with diphenyl carbonate 2a or ethyl phenyl carbonate 2b synthesized 2-arylquinazolin-4(3H)-ones 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 3j, 3k, 3l, 3m, 3n in simple and
- Aikawa, Shunichi,Sekiguchi, Chiharu,Yamazaki, Yuko,Hattori, Mika,Isaka, Tatsuya,Yoshida, Yasuhiko,Ihara, Shogo
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p. 343 - 348
(2014/04/17)
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- A kinetic study on nucleophilic displacement reactions of phenyl Y-substituted-phenyl carbonates with alkali metal ethoxides: Metal ion effect and reaction mechanism
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Pseudo-first-order rate constants (kobsd) have been measured for reactions of phenyl Y-substituted-phenyl carbonates with alkali metal ethoxides (EtOM, M = Li, Na, and K). The plot of kobsd vs. [EtOM] curves upward for the reaction of diphenyl carbonate with EtOM but is linear for that with EtOK in the presence of 18-crown-6-ether (18C6), indicating that the reaction is catalyzed by M+ ions and the catalytic effect disappears in the presence of 18C6. The kobsd values for the reactions with EtOK have been dissected into fEtO- and kEtOK, i.e., the second-order rate constants for the reactions with dissociated EtO- and ion-paired EtOK, respectively. The Hammett plots correlated with σ- and σ-0 constants exhibit highly scattered points, while the Yukawa-Tsuno plots result in an excellent linear correlation with p = 2.11 and r = 0.21 for kEtO-, and P = 1.62 and r = 0.26 for kEtOK, implying that the reaction proceeds through a concerted mechanism. The catalytic effect (i.e., the kEtOK/kEtOr ratio) is independent of the electronic nature of the substituent Y. Thus, it has been concluded that K+ ion catalyzes the reaction by increasing the electrophilicity of the reaction center.
- Um, Ik-Hwan,Seo, Ji-Yoon,Kang, Ji-Sun,An, Jun-Sung
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p. 1007 - 1013,7
(2020/08/24)
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- PROCESS FOR CONTINUOUS PRODUCTION OF ORGANIC CARBONATES OR ORGANIC CARBAMATES AND SOLID CATALYSTS THEREFORE
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Processes for the alcoholysis, inclusive of transesterification and/or disproportionation, of reactants are disclosed. The alcoholysis process may include feeding reactants and a trace amount of soluble organometallic compound to a reactor comprising a solid alcoholysis catalyst, wherein the soluble organometallic compound and the solid alcoholysis catalyst each independently comprise a Group II to Group VI element, which may be the same element in various embodiments. As an example, diphenyl carbonate may be continuously produced by performing transesterification over a solid catalyst followed by disproportionation, where a trace amount of soluble organometallic compound is fed to the transesterification reactor. Also disclosed is a process for reactivating a spent solid alcoholysis catalyst, such as a catalyst useful for transesterifications and/or disproportionations, the process including removing polymeric materials deposited on the catalyst and re-depositing catalytically active metals on the solid catalyst.
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Page/Page column 25
(2009/08/18)
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- PROCESS FOR THE PREPARATION OF DIARYL CARBONATE
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The invention relates to a process for the preparation of a diaryl carbonate by transesterification of an aromatic alcohol with a dialkyl carbonate in the presence of a transesterification catalyst during a period of time [ta], in which the aryl moiety is selected from unsubstituted phenyl and mono-, di- and trisubstituted phenyl groups, in which the alkyl moiety is selected from C2 to C4 linear and branched alkyl groups, in which the catalyst concentration is designated [ca], expressed as gram catalyst per gram of aromatic alcohol and dialkyl carbonate, in which the period of time [tm] and catalyst concentration [cm] are determined to arrive at a pre-set approach to the equilibrium for the transesterification of the aromatic alcohol with dimethyl carbonate to methyl aryl carbonate and methanol, in which the product [ca]*ta is at least 1.5* [cm]*tm, under otherwise the same reaction conditions.
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Page/Page column 19-23
(2008/12/07)
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- METHOD OF PREPARING DIALKYLCARBONATES
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The present invention relates to a process of preparing dialkylcarbonates, and particularly to an improved process of preparing dialkylcarbonates, which comprises performing a reaction between an alcohol compound and a chloroformate derivative in the presence of an imidazole compound, thereby enabling to prepare dialkylcarbonates with high yield in a mild condition without using toxic raw materials and to easily separate impurities.
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Page/Page column 8; 9
(2008/06/13)
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- Process for making diaryl carbonate
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Diphenyl carbonate is produced by reacting phenol with diethyl carbonate in a series of fixed bed reactors each of which is connected at different position on a distillation column via side draw and return streams. The composition of material in a distillation column varies along the length of the column, which is predictable under a given set of conditions of temperature and pressure, thus withdrawing streams at different stages in the column, allows the reactor receiving the feed from a particular stage to be operated under conditions to maximize the desired reaction, while allowing the unreacted or byproduct to go back into the distillation and be sent to a stage (by the equilibrium of the distillation) where they are favorably treated in a reactor.
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Page/Page column 4-7
(2008/06/13)
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- Process for producing organic carbonates
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A process for producing various organic carbonates by performing transesterification and disproportionation reactions in dual vapor/liquid phase mode preferably in the presence of solid catalyst composition selected from the group consisting of oxides, hydroxides, oxyhydroxides or alkoxides of two to four elements from Group IV, V and VI of the Periodic Table supported on porous material which has surface hydroxyl groups and the method of reactivating catalyst deactivated by polymer deposition by contacting the deactivated catalyst with a solution of hydroxy containing compound in a solvent such as benzene or THF.
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Page/Page column 8
(2008/06/13)
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- A new versatile synthesis of esters from Grignard reagents and chloroformates
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Cross-coupling reactions of chloroformates with organocopper reagents, derived from Grignard reagents, cuprous bromide and lithium bromide, provide a rapid and straightforward method for the synthesis of esters. Georg Thieme Verlag Stuttgart.
- Bottalico, Daniela,Fiandanese, Vito,Marchese, Giuseppe,Punzi, Angela
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p. 974 - 976
(2008/02/02)
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- A new, mild, general and efficient route to aryl ethyl carbonates in solvent-free conditions promoted by magnesium perchlorate
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A new, general and mild method for the direct synthesis of aryl and alkyl ethyl carbonates promoted by a Lewis acid is reported. The reaction proceeds smoothly with diethyl dicarbonate in the presence of Mg(ClO4) 2, a specific activator of 1,3-dicarbonyl compounds, and shows general applicability. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Bartoli, Giuseppe,Bosco, Marcella,Carlone, Armando,Locatelli, Manuela,Marcantoni, Enrico,Melchiorre, Paolo,Palazzi, Paolo,Sambri, Letizia
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p. 4429 - 4434
(2007/10/03)
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- Concerted mechanisms of the reactions of ethyl S-aryl thiocarbonates with substituted phenoxide ions
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The reactions of 4-nitrophenyl, 2,4-dinitrophenyl, and 2,4,6- trinitrophenyl O-ethyl thiolcarbonates with substituted phenoxide ions are subjected to a kinetic study in water, 25.0 °C, ionic strength 0.2 M (KCl). By following the reactions spectrophotometrically, pseudo-first-order rate coefficients (k(obsd)) are found under excess of the nucleophile. Plots of k(obsd) vs phenoxide anion concentration at constant pH are linear, with the slope (k(N)) independent of pH. The Bronsted-type plots (log k(N) vs pK(a) of the phenols) are linear with slopes β = 0.92, 0.77, and 0.61 for the reactions of the 4-nitrophenyl, 2,4-dinitrophenyl, and 2,4,6-trinitrophenyl derivatives, respectively. For these reactions, a concerted mechanism is proposed since the slope values are similar to those found in the concerted phenolysis of aryl acetates; the slope magnitudes are not consistent with a stepwise mechanism where the formation of a tetrahedral intermediate is rate limiting. Our results are in line with the finding that the reactions of the 2,4-dinitrophenyl and 2,4,6-trinitrophenyl derivatives with secondary alicyclic amines in water are concerted. In contrast, the reactions of the same substrates with pyridines are stepwise, which means that substitution of a pyridine moiety in a tetrahedral intermediate with a benzenethio group by a phenoxy group destabilizes the intermediate.
- Castro,Paves,Santos
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p. 2310 - 2313
(2007/10/03)
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- Correlation of the rates of solvolysis of phenyl chloroformate
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The specific rates of solvolysis of phenyl chloroformate in 21 solvents can be very well correlated using the extended Grunwald-Winstein equation, with incorporation of the NT solvent nucleophilicity scale and the YCl solvent ionizing scale, with sensitivities towards changes in the scale having values of 1.68 ± 0.10 and 0.57 ± 0.06, respectively. This is a solvolysis which, on the basis of several other types of evidence, is believed to follow an addition-elimination pathway with addition being rate-determining (or possibly an enforced concerted variant), and these sensitivities can be considered to be representative values for chloroformate esters following such a pathway.
- Kevill, Dennis N.,D'Souza, Malcolm J.
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p. 1721 - 1724
(2007/10/03)
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- Alkoxycarbonylation of alcohols and phenols by nitrosoformates
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Unstable neutral radicals [ROCONHO?] 2 and nitrosoformates 3 are formed by oxidation of N-hydroxycarbamates with lead dioxide. In the presence of alcohols or phenols and water they solvolyzed to mixtures of symmetrical 4 and asymmetrical 5 carbonates. The content of asymmetrical carbonates 5 increases with increasing reactivity of the nitrosoformates 3 formed, temperature, the content of water in the reaction mixture, and with decreasing reactivity of alcohol. The reactivities of individual alcohols have been evaluated with the help of competitive alcoholysis. The new method of alcohol or phenol alkoxylation has been verified experimentally by preparing six asymmetrical carbonates which were obtained in 34 to 47% yields.
- Mindl, Jaromir,Halama, Ales,Cernosek, Zdenek
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p. 1053 - 1063
(2007/10/03)
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- Sodium Hydrogen Telluride- An Efficient Reagent for Deblocking of Aryl Ethyl Carbonates
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Sodium hydrogen telluride is found to be a mild and efficient reagent for deblocking of aryl ethyl carbonates.
- Shobana, N.,Amirthavalli, M.,Deepa, V.,Shanmugam, P.
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p. 965 - 966
(2007/10/02)
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- KINETIC RELATIONSHIPS GOVERNING THE ETHANOLYSIS OF HALOGENOFORMATES
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The kinetics of the ethanolysis of a series of halogenoformates at various temperatures were investigated by titrimetric and conductometric methods.It is suggested that the conformational composition of the chloroformates has an effect on the solvolysis rate.A parameter which takes account of the conformational factor is proposed, and the quantitative relation of the Taft type relating the solvolysis rate constant to the parameters of the substituents is obtained.The effect of the leaving group and the effect of substitution of the ether oxygen by sulfur in the chloroformate were investigated.The obtained data are interpreted in terms of an addition-elimination mechanism.
- Orlov, S. I.,Chimishkyan, A. L.,Grabarnik, M. S.
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p. 1981 - 1987
(2007/10/02)
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