- Activation and Functionalisation of the C-H Bonds of Methane and Higher Alkanes by a Silica-supported Tantalum Hydride Complex
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Silica-supported tantalum hydride activates at low temperature the C-H and the C-D bonds of cyclooctane and CD4, respectively, to form the corresponding cyclooctyl and perdeuteriomethyl-tantalum surface complexes; these complexes are transformed under molecular oxygen into the corresponding tantalum-alkoxy derivatives which with acetic acid give rise to the corresponding alkylacetates.
- Vidal, Veronique,Theolier, Albert,Thivolle-Cazat, Jean,Basset, Jean-Marie
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Read Online
- Gold-Catalyzed Direct C(sp3)?H Acetoxylation of Saturated Hydrocarbons
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In this communication we report our studies towards the development of a gold-catalyzed direct acetoxylation of C(sp3)?H bonds. We achieve this through the use of the hypervalent iodine reagent PhI(OAc)2 in combination with a simple gold salt (HAuBr4) as the catalyst. Through a comparison of the reactivities of cyclooctane and adamantane we judge the reaction to proceed via hydride transfer. This is further substantiated through computational studies of the relative energies for the anions, radicals and cations derived from C?H bond cleavage of cyclooctane and adamantane relevant to the C?H cleaving step.
- Jo, Tae Geun,Klein, Johannes E. M. N.
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p. 4087 - 4091
(2021/08/25)
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- Selective biocatalytic hydroxylation of unactivated methylene C-H bonds in cyclic alkyl substrates
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The cytochrome P450 monooxygenase CYP101B1 from Novosphingobium aromaticivorans selectively hydroxylated methylene C-H bonds in cycloalkyl rings. Cycloketones and cycloalkyl esters containing C6, C8, C10 and C12 rings were oxidised with high selectively on the opposite side of the ring to the carbonyl substituent. Cyclodecanone was oxidised to oxabicycloundecanol derivatives in equilibrium with the hydroxycyclodecanones.
- Sarkar, Md Raihan,Dasgupta, Samrat,Pyke, Simon M.,Bell, Stephen G.
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p. 5029 - 5032
(2019/05/21)
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- Fine Control over Site and Substrate Selectivity in Hydrogen Atom Transfer-Based Functionalization of Aliphatic C-H Bonds
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The selective functionalization of unactivated aliphatic C-H bonds over intrinsically more reactive ones represents an ongoing challenge of synthetic chemistry. Here we show that in hydrogen atom transfer (HAT) from the aliphatic C-H bonds of alkane, ether, alcohol, amide, and amine substrates to the cumyloxyl radical (CumO?) fine control over site and substrate selectivity is achieved by means of acid-base interactions. Protonation of the amines and metal ion binding to amines and amides strongly deactivates the C-H bonds of these substrates toward HAT to CumO?, providing a powerful method for selective functionalization of unactivated or intrinsically less reactive C-H bonds. With 5-amino-1-pentanol, site-selectivity has been drastically changed through protonation of the strongly activating NH2 group, with HAT that shifts to the C-H bonds that are adjacent to the OH group. In the intermolecular selectivity studies, trifluoroacetic acid, Mg(ClO4)2, and LiClO4 have been employed in a orthogonal fashion for selective functionalization of alkane, ether, alcohol, and amide (or amine) substrates in the presence of an amine (or amide) one. Ca(ClO4)2, that promotes deactivation of amines and amides by Ca2+ binding, offers, moreover, the opportunity to selectively functionalize the C-H bonds of alkane, ether, and alcohol substrates in the presence of both amines and amides.
- Salamone, Michela,Carboni, Giulia,Bietti, Massimo
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p. 9269 - 9278
(2016/10/14)
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- Sulfonic acid-functionalized periodic mesoporous organosilicas in esterification and selective acylation reactions
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The application of sulfonic acid-functionalized periodic mesoporous organosilicas (PMOs) having either phenyl (1a) or ethyl (1b) bridging groups was investigated in the esterification of a variety of alcohols and fatty acids. It was found that 1b consistently exhibited higher catalytic performance than 1a in the described reaction. In particular, it was proposed that the superior catalytic activity of 1b in esterification of fatty acids with methanol is a result of adequate hydrophobic-hydrophilic surface balance in the ethyl PMO catalyst. In addition, the study of chemoselective acylation of 1,3-butanediol with dodecanoic acid with varied mesoporous silica-supported solid sulfonic acids including both 1a and 1b implies that there is a compromise between the reaction selectivity and the surface physicochemical properties of the employed catalyst. Our results clearly show that the catalyst having high surface hydrophilic nature gives high selectivity toward the formation of mono-acylated products whereas those with relatively high hydrophobic characteristics showed enhanced selectivity toward the formation of di-acylated products.
- Karimi, Babak,Mirzaei, Hamid M.,Mobaraki, Akbar,Vali, Hojatollah
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p. 3624 - 3631
(2015/07/01)
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- Synthesis of sulfonic acid containing ionic-liquid-based periodic mesoporous organosilica and study of its catalytic performance in the esterification of carboxylic acids
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A new sulfonic acid containing ionic-liquid-based periodic mesoporous organosilica (PMO-IL-SO3H) material was prepared and its catalytic application was investigated in the esterification of carboxylic acids with alcohols. The PMO-IL-SO3H nanocatalyst was first characterized with diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and nitrogen sorption analysis. Then, the catalytic performance of this material was studied in the esterification of carboxylic acids with short- and long-chain aliphatic alcohols, cyclic alcohols, and benzylic alcohols under solvent-free conditions. The results showed that the catalyst has superior activity for the conversion of several alcohols to afford the corresponding ester products in excellent yields and high purity. Moreover, the catalyst could be recovered and reused several times without a significant decrease in activity and product selectivity. Copyright
- Elhamifar, Dawood,Karimi, Babak,Moradi, Abbas,Rastegar, Javad
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p. 1147 - 1152
(2014/10/16)
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- Direct dehydrative esterification of alcohols and carboxylic acids with a macroporous polymeric acid catalyst
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A macroporous polymeric acid catalyst was prepared for the direct esterification of carboxylic acids and alcohols that proceeded at 50-80 C without removal of water to give the corresponding esters with high yield. Flow esterification for the synthesis of biodiesel fuel was also achieved by using a column-packed macroporous acid catalyst under mild conditions without removal of water.
- Minakawa, Maki,Baek, Heeyoel,Yamada, Yoichi M. A.,Han, Jin Wook,Uozumi, Yasuhiro
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supporting information
p. 5798 - 5801
(2013/12/04)
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- Hydroacetoxylation of olefins with acetic acid genetated in situ from vinyl acetate in the presence of ruthenium complexes
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Ruthenium complexes catalyze the decomposition of vinyl acetate releasing the acetic acid and its subsequent addition to linear and cyclic olefins.
- Khusnutdinov,Shchadneva,Khisamova,Dzhemilev
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experimental part
p. 155 - 160
(2011/05/03)
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- Dual behavior of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions
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The dual behavior phenomenon of alcohols in iodine-catalyzed esterification under solvent-free reaction conditions (SFRCs) is described; the governing factor is the stability of the carbonium ion generated from the alcohol; high concentration reaction conditions (HCRCs) or dilute solutions are much less suitable. In the case of benzylic alcohols, loss of optical activity was noted, whereas alkyl alcohols furnished a product with retention of stereochemistry.
- Jereb, Marjan,Vra?i?, Dejan,Zupan, Marko
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scheme or table
p. 2347 - 2352
(2009/09/06)
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- Selective oxidation of alkanes with molecular oxygen and acetaldehyde in compressed (supercritical) carbon dioxide as reaction medium
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The oxidation of cycloalkanes or alkylarenes with molecular oxygen and acetaldehyde as sacrificial co-reductant occurs efficiently in compressed (supercritical) carbon dioxide (scCO2) under mild multiphase conditions. No catalyst is required and high-pressure ATR-FTIR online measurements show that a radical reaction pathway is heterogeneously initiated by the stainless steel of the reactor walls. For secondary carbon atoms, high ketone to alcohol ratios are observed (3.5-7.9), most probably due to fast consecutive oxidation of alcoholic intermediates. Since C - C scission reactions are detected only to a very small extent, tertiary carbon atoms are transformed into the corresponding alcohols with high selectivity. Detailed analysis of the product distributions and other mechanistic evidence suggest that acetaldehyde acts not only as the sacrificial oxygen acceptor, but also as an efficient H-atom donor for peroxo and oxo radicals and as a crucial reductant for hydroperoxo intermediates. In comparison to other inert gases such as compressed N, or Ar, the use of carbon dioxide was shown to increase the yields of alkane oxygenates under identical reaction conditions.
- Theyssen, Nils,Hou, Zhenshan,Leitner, Walter
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p. 3401 - 3409
(2008/09/19)
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- Esterification of alkene with cerium(IV) sulfate in carboxylic acid
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Reaction of alkenes [cyclohexene (1), cycloheptene (2), cyclooctene (3), 1-heptene (4), 1-octene (5), styrene (6), 1,7-octadiene (7), indene (8), and 1,2-dihydronaphthalene (9)] with cerium(IV) sulfate (CS) in carboxylic acids [formic acid, acetic acid, and propionic acid] readily yielded the corresponding carboxylic esters. This addition reaction follows the Markovnikov rule. This reaction provides a new simple method for preparing carboxylic esters from alkenes. It was also found that this method is useful for formylation.
- Horiuchi, C. Akira,Fukushima, Tomoaki,Furuta, Noriyuki,Chai, Wen,Ji, Shun-Jun,Saito, Yoshikazu,Hashimoto, Chikao,Takahashi, T. Tomoyoshi,Sugiyama, Takashi,Muto, Akinori,Sakata, Yusaku,Nozaki, Sukekatsu
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p. 270 - 272
(2007/10/03)
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- Iron perchlorate on silica gel as multi-purpose reagent for catalysis of closure and rupture of carbon-oxygen bond in epoxides, alcohols, and esters
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Aliphatic alcohols and water in the presence of catalytic amounts of Fe3+ ion introduced as iron(III) perchlorate on silica gel carrier perform efficient regiospecific opening of an epoxy ring. Carbon acids esterification with various type alcohols was carried out using the system Fe(ClO4)3-silica gel in dichloromethane under conditions excluding solvolysis. Acetylation and formylation of alcohols was performed by efficient transesterification with ethyl acetate and ethyl formate.
- Salechi,Khodaei,Ghareghani,Motlagh
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p. 794 - 796
(2007/10/03)
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- A LEWIS ACID-CATALYZED PROCEDURE FOR THE CONVERSION OF 2-METHOXYETHOXYMETHYL ETHERS TO CARBOXYLIC ESTERS
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A procedure for the conversion of 2-methoxyethoxymethyl (MEM) ethers to carboxylic esters employed ferric chloride (0.4 equivalents) and a carboxulic anhydride (14 equivalents) and exibited selectivity for the MEM ether functionality in the presence of benzyl ethers.
- Gross, Raymond S.,Watt, David S.
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p. 1749 - 1760
(2007/10/02)
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- β'β ANIONIC ELIMINATION OF CARBOXYLIC ESTERS
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The elimination of lithium, magnesium and aluminium enolates of isobutyrates of medium ring cyclanols occurs in a syn fashion.A set of experimental procedures is presented.This elimination seems to be restricted to strained systems.The stereochemistry has been determined on stereospecifically deuterated cyclooctanol isobutyrates.The primary isotope effect kH/k2 was 3.0 +/- 0.1 and the secondary 1.1.The name β'β elimination is proposed for this syn elimination and related elimination.
- Aubert, Corinne,Begue, Jean-Pierre,Biellmann, Jean-Francois
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p. 5581 - 5590
(2007/10/02)
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- Electrophilic Cleavage of Cyclopropanes. Acetolysis of Bicyclic and Tricyclic Cyclopropanes
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The acetolysis of a series of bicycloalkanes and propellanes has been studied.The effect of ring strain, caused by changing ring size or introducing a trans-ring fusion, on the rate and products of the reaction has been examined.No correlation was found between rates of acetolysis and strain energy relief, but with the exception of propellane, there is a rough correlation with ionization potentials.The degree of polarization of the C-C bonds in the presence of a proton correlates very well with reactivity and is a controlling factor for the acetolysis rates.The importance of the energies of unoccupied orbitals with the appropriate symmetry in controlling electron polarization is shown by the large difference in rate of reaction between - and propellanes.
- Wiberg, Kenneth B.,Kass, Steven R.,Meijere, Armin de,Bishop, K. C.
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p. 1003 - 1007
(2007/10/02)
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- REACTION OF ORGANOBORANES WITH LEAD(IV) ACETATE AZIDE. A SYNTHESIS OF AZIDOALKANES FROM ALKENES VIA HYDROBORATION.
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Trialkylboranes prepared from alkenes via hydroboration react with lead(IV) acetate azide in dichloromethane at minus 25 degree C to form the corresponding azidoalkanes in a one-pot manner. One of two of the alkyl groups of trialkylboranes are utilized in the reaction. For example, 1-azidohexane is afforded from 1-hexene in 50% yield based on the alkene employed.
- Masuda,Hoshi,Arase
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p. 1026 - 1030
(2007/10/02)
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