- Diol-Ritter Reaction: Regio- And Stereoselective Synthesis of Protected Vicinal Aminoalcohols and Mechanistic Aspects of Diol Monoester Disproportionation
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The well-known epoxide-Ritter reaction generally affords oxazolines with poor to average regioselectivity. Herein, a mechanism-based study of the less known diol-Ritter reaction has provided a highly regioselective procedure for the synthesis of 1-vic-amido-2-esters from either terminal epoxides or 1,2-diols via Lewis acid-catalyzed monoesterification. When treated with a stoichiometric Lewis acid catalyst (BF3), these diol monoesters form dioxonium cation intermediates that are ring-opened with nitrile nucleophiles to form nitrilium intermediates, which undergo rapid and irreversible hydration to give the desired amidoesters. Diester byproduct formation is irreversible and appears to occur through disproportionation of diol monoester. With chiral epoxide starting materials, the formation of amidoester occurs with retention of configuration and no apparent erosion of optical purity as determined by single-crystal X-ray analyses and chiral chromatography, respectively. The direct access to chiral vic-amidoesters is especially practical with regard to the synthesis of antibacterial oxazolidinone analogues of the Zyvox antimicrobial family.
- Ondari, Mark E.,Klosin, Jerzy,Kruper, William R.,Lysenko, Ivan,Thomas, Pulikkottil J.,Cheng, Kevin,Abboud, Khalil A.,Kruper, William J.
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p. 2063 - 2074
(2021/10/20)
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- COMPOUNDS AND COMPOSITIONS FOR OCULAR DELIVERY
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The present invention provides new prodrags of Sunitinib, Brinzolamide, and Dorzolamide and compositions to treat medical disorders, for example glaucoma, a disorder or abnormality related to an increase in intraocular pressure (TOP), a disorder requiring neuroprotection, age-related macular degeneration, or diabetic retinopathy.
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Page/Page column 108; 211
(2020/05/12)
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- DBN-Catalyzed Regioselective Acylation of Carbohydrates and Diols in Ethyl Acetate
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The 1,5-diazabicyclo[4.3.0]non-5-ene (DBN)-catalyzed regioselective acylation of carbohydrates and diols in ethyl acetate has been developed. The hydroxyl groups can be selectively acylated by the corresponding anhydride in EtOAc in the presence of a catalytic amount (as low as 0.1 equiv.) of DBN at room temperature to 40 °C. This method avoids metal catalysts and toxic solvents, which makes it comparatively green and mild, and it uses less organic base compared with other selective acylation methods. Mechanism studies indicated that DBN could catalyze the selective acylation of hydroxyl moieties through a dual H-bonding interaction.
- Ren, Bo,Zhang, Mengyao,Xu, Shijie,Gan, Lu,Zhang, Li,Tang, Lin
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supporting information
p. 4757 - 4762
(2019/07/31)
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- Diisopropylethylamine-triggered, highly efficient, self-catalyzed regioselective acylation of carbohydrates and diols
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A diisopropylethylamine (DIPEA)-triggered, self-catalyzed, regioselective acylation of carbohydrates and diols is presented. The hydroxyl groups can be acylated by the corresponding anhydride in MeCN in the presence of a catalytic amount of DIPEA. This method is comparatively green and mild as it uses less organic base compared with other selective acylation methods. Mechanistic studies indicate that DIPEA reacts with the anhydride to form a carboxylate ion, and then the carboxylate ion could catalyze the selective acylation through a dual H-bonding interaction.
- Ren, Bo,Gan, Lu,Zhang, Li,Yan, Ningning,Dong, Hai
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supporting information
p. 5591 - 5597
(2018/08/17)
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- H-bonding activation in highly regioselective acetylation of diols
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H-bonding activation in the regioselective acetylation of vicinal and 1,3-diols is presented. Herein, the acetylation of the hydroxyl group with acetic anhydride can be activated by the formation of H-bonds between the hydroxyl group and anions. The reaction exhibits high regioselectivity when a catalytic amount of tetrabutylammonium acetate is employed. Mechanistic studies indicated that acetate anion forms dual H-bonding complexes with the diol, which facilitates the subsequent regioselective monoacetylation.
- Zhou, Yixuan,Rahm, Martin,Wu, Bin,Zhang, Xiaoling,Ren, Bo,Dong, Hai
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p. 11618 - 11622
(2013/12/04)
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- Hydration of alkenes and cycloalkenes in the presence of chromium and copper complexes
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Chromium and copper complexes catalyzed hydration of acyclic and cyclic olefins in the presence of carbon tetrachloride at 110-160 C (4-12 h) with formation of the corresponding alcohols.
- Khusnutdinov,Oshnyakova,Shchadneva
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p. 1428 - 1432
(2014/01/06)
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- Organosilicon-mediated regioselective acetylation of carbohydrates
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Organosilicon-mediated, regioselective acetylation of vicinal- and 1,3-diols is presented. Methyl trimethoxysilane or dimethyl dimethoxysilane was first used to form cyclic 1,3,2-dioxasilolane or 1,3,2-dioxasilinane intermediates, and subsequent acetate-c
- Zhou, Yixuan,Ramstroem, Olof,Dong, Hai
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supporting information; experimental part
p. 5370 - 5372
(2012/06/18)
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- Addition of CCl4 to olefins catalyzed by chromium and ruthenium complexes: The influence of water as a nucleophilic additive
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The feasibility of the addition of CCl4 to linear and cyclic olefins and dienes in the presence of chromium and ruthenium complexes was established. The influence of water as a nucleophilic additive and the influence of the olefin nature, the c
- Khusnutdinov,Schadneva,Oshnyakova,Dzhemilev
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experimental part
p. 331 - 338
(2010/06/16)
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- Hydrogenation of hindered ketones catalyzed by a silica-supported compact phosphine-Rh system
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(Chemical Equation Presented) A heterogeneous mono(phosphine)-Rh catalyst system silica-SMAP-Rh(OMe)(cod), where silica-SMAP stands for a caged, compact trialkylphosphine (SMAP) supported on silica gel, showed broad applicability toward the hydrogenation of hindered ketones. Doubly α-branched ketones such as diisopropyl ketone was hydrogenated under nearly atmospheric conditions. Di-tert-butyl ketone could be hydrogenated under more forcing conditions.
- Kawamorita, Soichiro,Hamasaka, Go,Ohmiya, Hirohisa,Hara, Kenji,Fukuoka, Atsushi,Sawamura, Masaya
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supporting information; scheme or table
p. 4697 - 4700
(2009/05/26)
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- Transacylation. Biomimetic synthesis of esters of acetic acid
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By mixing of β-hydroxypropyl phosphate and acetic acid in ethanol solution, ethyl acetate is produced. As found, acetyl phosphate is first formed, then it reacts with the solvent to give the final ethyl acetate product. By similar procedures, acetates of methanol, n-propanol, and n-butanol are also produced. Propylene oxide serves as a condensing agent.
- Devedjiev, Ivan T.,Ganev, Vesselin G.
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p. 350 - 352
(2007/10/03)
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- Efficient chemoselective liquid phase acylation of amines, alcohols and bifunctional compounds over ZSM-35
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ZSM-35, is a medium pore zeolite, has been synthesized using ethylene diamine as organic template. The catalyst is used in the acylation of different amines, alcohols and bifunctional compounds. This material is found to be active and selective acid catalyst, exhibits not only very good activity but also very high chemo-selectivity towards monoacylation of bifunctional compounds. This material is more reactive for smaller organic compounds because of its pore dimension. In case of bifunctional compounds like amino alcohols, amines are selectively acylated at lower temperature.
- Srivastava,Venkatathri
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p. 888 - 891
(2007/10/03)
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- Yttria-zirconia based Lewis acid: An efficient and chemoselective catalyst for acylation reactions
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Yttria-zirconia based strong Lewis acid efficiently catalyzes acylation of alcohols, amines and thiols under environmentally safe, heterogeneous reaction conditions with high selectivity and in excellent yields.
- Kumar,Pandey,Bodas,Dongare
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p. 206 - 209
(2007/10/03)
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- Formation and characterisation of a physical chitin gel
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The formation of N-acetyl chitosan gels in anacetic acid-water-propanediol solution was studied. Side reactions arising from the esterification of 1,2-propanediol by acetic anhydride, and hydrolysis of acetic anhydride were studied, as well as their possible role on the gel formation. The gels were studied by FTIR and 1H NMR spectroscopy. Independently of the initial acetylation degree of chitosan, a minimal acetylation degree is required for gelation (80%). The final acetylation degree of the gels increases with the molar ratio acetic anhydride/amine, but does not reach 100%. An increase in temperature favours the molecular mobility, inter- and intra-molecular hydrogen bondings and hydrophobic interactions, responsible for gelation which appears to depend on two parameters: a critical acetylation degree and a critical molecular weight allowing the aggregation of the polymer chains. The nature of the solvent used to avoid chitosan side reactions during gelation (ethanol or propanediol) does not influence the chemical structure of the gel but only the kinetics of gelation.
- Vachoud, Laurent,Zydowicz, Nathalie,Domard, Alain
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p. 169 - 177
(2007/10/03)
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- Regio- and stereoselective transacylation of polyhydric alcohols using pronase in organic solvents
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Pronase a mixture of proteases from Streptomyces griseus has been found to be a good catalyst for transacylation in organic solvents.With equimolar concentrations of p-nitrophenyl acetate as acyl donor in pyridine, aliphatic diols give predominantly the monoacetates.Glucose and isomeric hexoses give the 6-O-acetates in good yield. 6-Deoxy-sugars however, yield mixtures of acetates indicating that regioselectivity among the secondary hydroxyl groups are poor.Racemic trans-1,2-cyclohexanediol affords the (1R, 2R)-monoacetate in 44percent yield with greater than 90percent enantiomer ic purity. cis-1,2-cyclohexanediol and cis-1,2-cyclohexanedimethanol also give optically active monoacetates.
- Bhattacharya, A,Ali, E
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p. 898 - 899
(2007/10/02)
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- OXIDATION OF CYCLIC ACETALS BY HYDROGEN PEROXIDE
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The hydroxylation of cyclic acetals by hydrogen peroxide leads to the formation of the monoesters of glycols, which are the principal reaction products.During the hydroxylation of 4-substituted 1,3-dioxacyclanes two isomeric monoesters are formed, and the ester with a primary acylated hydroxyl group predominates.
- Nazarov, M. N.,Kuramshin, E. M.,Zlotskii, S. S.,Rakhmankulov, D. L.
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p. 1258 - 1260
(2007/10/02)
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- Formation of Glycol Monoacetates in the Oxidation of Olefins Catalyzed by Metal Nitro Complexes: Mono- vs. Bimetallic System
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The oxidation of terminal olefins by bis(acetonitrile)chloronitropalladium(II) (1) in acetic acid leads to a mixture of glycol monoacetate isomers as the main products.Various amounts of ketones and unsaturated acetates are also formed.The rate of formation and the yield of glycol monoacetate decrease with increasing chain length.Cyclic olefins yield no glycol monoacetates.Replacement of acetic acid by stronger or sterically hindered carboxylic acids completely eliminates the formation of glycol monocarboxylates.Introduction of oxygen converts this stoichiometric reaction into a catalytic system.Our studies, including those carried out with complex 1 labeled with 18O in the nitro ligand, suggest that the glycol monoacetates and most of the ketones are the product of oxygen atom transfer from the nitro group, while the unsaturated acetates are the result of a Wacker-type reaction.In the glycol monoacetate, the 18O label is found exclusively in the acetate group.A mechanism which is in agreement with the above observations as well as a comparison of the above reaction with the oxidation of olefins by nitrate ions in the presence of palladium(II) salts is offered.The formation of glycol monoacetates in the monometallic system represented by complex 1 is to be compared with the results obtained in the bimetallic systems consisting of a combination of py(TPP)CoNO2 and either (CH3CN)2PdCl2 or Pd(OAc)2.In the latter systems, ketones or vinyl acetates are found as the predominant products.This fact underlines the difference between the mono- and bimetallic systems and strongly argues against alternative mechanisms involving nitro group transfer from cobalt to palladium before the olefin oxidation takes place.Additional evidence underlining the difference between these two systems is presented.
- Mares, Frank,Diamond, Steven E.,Regina, Francis J.,Solar, Jeffrey P.
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p. 3545 - 3552
(2007/10/02)
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- Kinetic Investigation of the Reaction between Propylene Oxide and Acetic Acid
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The rate of the reaction between propylene oxide and acetic acid was found to be first order in propylene oxide concentration, while the partial reaction order for acetic acid varied with the composition of the reaction mixture between 2.0 and 2.6.Different alkali-metal acetate catalysts were investigated as well as the temperature dependence of the 'non-catalysed' and 'catalysed' reactions.Our results suggest that protonated propylene oxide formed in the pre-equilibrium and the hydrogen-bonded acetic acid-propylene oxide complex react with acetate ion or with acetic acid
- Szakacs, Sandor,Goeboeloes, Sandor,Nagy, Ferenc
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p. 417 - 420
(2007/10/02)
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- Method for preparing glycol esters
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An improved method for making glycol monoesters and diesters of carboxylic acid by the reaction of an olefin and oxygen in the presence of a carboxylic acid and a catalyst, wherein said catalyst includes a compound of a metal of groups IVB - VIIB having an atomic number between 40 and 42 inclusive or between 72 and 75 inclusive, i.e. zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, or rhenium.
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