- Direct catalytic anti-markovnikov addition of carboxylic acids to alkenes
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A direct catalytic anti-Markovnikov addition of carboxylic acids to alkenes is reported. The catalyst system is comprised of the Fukuzumi acridinium photooxidant (1) and a substoichiometric quantity of a hydrogen-atom donor. Oxidizable olefins, such as styrenes, trisubstituted aliphatic alkenes, and enamides, can be employed along with a variety of carboxylic acids to afford the anti-Markovnikov addition adducts exclusively. A deuterium-labeling experiment lends insight to the potential mechanism.
- Perkowski, Andrew J.,Nicewicz, David A.
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supporting information
p. 10334 - 10337
(2013/08/23)
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- Preparation of silica-supported sulfate and its application as a stable and highly active solid acid catalyst
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Silica sulfate was prepared by a simple procedure, and proved to be an efficient and recyclable solid acid catalyst. SO3H groups were successfully introduced to silica surface while keeping its structure intact, as proved by XRD patterns and SEM images of the catalyst. With the catalysis of the supported sulfate materials, many of the ketones are efficiently transformed into the corresponding lactones with 30% hydrogen peroxide. In addition, the high performance of silica sulfate as a heterogeneous catalyst was further demonstrated for the esterification of varieties of carboxylic acid with ethanol.
- Yang, Zhi-Wang,Niu, Leng-Yuan,Jia, Xiao-Jie,Kang, Qiao-Xiang,Ma, Zhen-Hong,Lei, Zi-Qiang
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experimental part
p. 798 - 802
(2011/12/21)
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- Nonaromatic amidine derivatives as acylation catalysts
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(Chemical Equation Presented) Catalytic activity of nonaromatic bicyclic amidines and bicyclic isothioureas in acylation reactions was found to be remarkably dependent on the sizes of both rings. DBN and especially its thia-analogue (THTP) have been identified as highly active acylation catalysts.
- Birman, Vladimir B.,Li, Ximin,Han, Zhenfu
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- Asymmetric transesterification of secondary alcohols catalyzed by feruloyl esterase from Humicola insolens
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A new asymmetric transesterification of secondary alcohols catalyzed by feruloyl esterase from Humicola insolens has been found. Although alcohols are not the natural substrates for this enzyme, a high R enantioselectivity was observed. Stereochemical studies showed that variations in substrate structure lead to strong variations in enantioselectivity. The highest enantioselectivities are obtained when the β-carbon of the secondary alcohol is tertiary or quaternary.
- Hatzakis, Nikos S.,Smonou, Ioulia
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p. 325 - 337
(2007/10/03)
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- The Influence of Steric Effects on the Selectivity of Radical CC Bond Formation Reactions
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Bulky substituents R1 and R2 at radical 5 decrease the rate of addition to diethyl fumarate to a larger extent than to methyl acrylate (Table 1).The comparison with H-abstraction, which is only slightly influenced by steric effects, shows that 5e (R2 = t-C4H9) reacts at least 235 times slower with diethyl fumarate than 5a (R2 = CH3) (Table 2).Therefore, the stereoselectivity of cyclic radicals 1 (n = 1,2) increases if the CC bond formation reaction is carried out with diethyl fumarate instead of methyl acrylate.
- Giese, Bernd,Harnisch, Hanna,Luening, Ulrich
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p. 1345 - 1351
(2007/10/02)
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- Kinetics and Mechanisms of Nucleophilic Displacement with Heterocycles as Leaving Groups. 17. Solvolysis of 14-(Primary alkyl)-5,6,8,9-tetrahydro-7-phenyldibenzoacridiniums: Rates, Identification of Products, Activation Parameters, and a General Discussion of Mechanism
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Solvolysis rate are reported for the Me, Et, n-Pr, n-Pent, n-Oct, i-Bu, neo-Pent, PhCH2CH2, and MeOCH2CH2 title compounds in MeOH, EtPH, PentOH, CH3CO2H, and CF3CO2H.Rate variations with alkyl group structure are far less than the corresponding rate variations for the tosylate solvolysis, and afford no evidence for rate-enhancing participation by β-phenyl or β-methoxy groups in the acridinium solvolyses.The n-propyl, n-pentyl, and n-octyl title compounds solvolyze in CH3OD and CH3CO2D to give mixtures of normal and rearranged products, none of which contain deuterium and which are therefore not formed via olefin intermediates.Methanolysis of the isobutyl title compounds occurs via olefin, but the acetolysis also involves an important nonolefinic pathway yielding isobutyl and sec-butyl acetates.Methanolysis products from the neopentyl derivative are heavily deuterated, but acetolysis yields undeuterated neopentyl acetate as well as deuterated tert-pentyl acetate.Product proportions calculated using GC/MS were used to deduce the fractions of reactions by various mechanistic pathways.Individual rates are calculated for solvolysis to the various unrearranged and rearranged products.They indicate that normal substitution in MeOH occurs by a classical SN2 reaction, but that such substitution in AcOH involves ion-pair intermediates.It is concluded that such ion pairs under go Me and H migration after the rate-determining stage, in competition with substitution.Activation parameters provide further evidence for the mechanistic paths proposed which are discussed in relation to literature data available for the corresponding tosylate.
- Katritzky, Alan R.,Dega-Szafran, Zofia,Lopez-Rodriguez, Maria L.,King, Roy W.
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p. 5577 - 5585
(2007/10/02)
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- The Novel Synthesis of Alkyl Cyanides by the Reaction of Sodium Trialkylcyanoborate with Sodium Cyanide and Lead(IV) Acetate
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Sodium trialkylcyanoborates gave good yields of the corresponding alkyl cyanides in the reaction with sodium cyanide and lead(IV) acetate.
- Masuda, Yuzuru,Hoshi, Masayuki,Yamada, Tetsuo,Arase, Akira
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p. 398 - 399
(2007/10/02)
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- Acid-induced 13C Nuclear Magnetic Resonance Chemical Shift Changes of Ether and Ester Carbon Atoms
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13C N.m.r. chemical shifts of ehters dissolved in tetrachloromethane are displaced on addition of trifluoroacetic acid.The displacements result from independent interactions of the acid with the substrate oxygen atoms and alkyl residues.The structure-dependent and stereoselective shift changes are useful for signal assignments, structure determination, conformational analysis, assessment of the distribution of rapidly interconverting conformers of esters, and estimation of the relative basicity of ethers.
- Begtrup, Mikael
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p. 1609 - 1618
(2007/10/02)
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- Reactions with Umpolung via Radicals: CC-Bond Formation between Ketones and Alkenes
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The hydrazones 1 - 11 from ketones react in a general synthetic procedure with alkenes 33a - m to yield products 34 - 44 (table 2 and 3).Important intermediates of these reactions with umpolung are 1-acetoxyalkyl radicals 49 that are formed from organomercuric salts 14 - 24 by reduction with NaBH4.This new CC-bond formation reaction can be carried out in a one-pot synthesis without isolation of the metalorganic compounds (table 4). - In side reactions the reduction products 50 are formed, if bulky starting compounds or less reactive alkenes are used (table 5 and 6).
- Giese, Bernd,Erfort, Ulrich
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p. 1240 - 1251
(2007/10/02)
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- RATIO OF POLAR AND RADICAL PROCESSES IN THERMAL TRANSFORMATIONS OF PEROXIDES. I. EFFECT OF THE LENGTH AND BRANCHING OF THE CHAIN IN THE ALKYL SUBSTITUENT AT THE α-CARBON ATOM OF THE ACYL GROUP
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Acetyl 2-methylpropionyl, acetyl 2-methylbutyryl, acetyl 2-methyloctanoyl, acetyl 2,3-dimethylbutyryl, and acetyl 2,3,3-trimethylbutyryl peroxides are transformed thermally under the investigated experimental conditions with the formation of the corresponding acyl alkyl carbonates and radical products.The ratio of the polar and radical processes is affected by the length and branching of the chain in the hydrocarbon substituent at the α-carbon atom of the acyl group.
- Stankevich, A. I.,Zyat'kov, I. P.,Lazareva, A. M.,El'nitskii, A. P.
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p. 1543 - 1548
(2007/10/02)
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