- Reactivity of substituted benzoic acids and their complexes with 2,4,6-trinitrotoluene toward diphenyldiazomethane
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The reactions of 2,4-dihydroxybenzoic and 4-aminobenzoic acids with diphenyldiazomethane are accelerated in the presence of 2,4,6-trinitrotoluene as π-acceptor. The catalytic effect of the latter is determined by the formation of charge-transfer complexes
- Ryzhakov,Andreev
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- Iron(III)-catalyzed direct synthesis of diphenylmethyl esters from 2-diphenylmethoxypyridine
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A highly efficient method has been developed for the synthesis of diphenylmethyl (DPM) esters from 2-diphenylmethoxypyridine. Various carboxylic acids readily reacted with 2-diphenylmethoxypyridine in the presence of FeCl3 as a catalyst to provide the desired DPM esters with high yields. The procedure is facile and enables effective synthesis of a variety of esters for the protection of carboxylic acids.
- Tran, Van Hieu,La, Minh Thanh,Kim, Hee-Kwon
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p. 2379 - 2387
(2019/07/03)
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- Facile synthesis of diphenylmethyl esters from 2-diphenylmethoxypyridine using catalytic boron trifluoride·diethyl etherate
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A practical method for the direct preparation of diphenylmethyl (DPM) esters from 2-diphenylmethoxypyridine is described. The reaction was readily performed in the presence of a catalytic amount of boron trifluoride-diethyl etherate at room temperature. Using this reaction protocol, various carboxylic acids were converted to DPM esters with high yields. This method is highly effective for the protection of carboxylic acids and the synthesis of DPM esters, and offers a promising approach for facile esterification of a variety of carboxylic acids.
- La, Minh Thanh,Kim, Hee-Kwon
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p. 1855 - 1859
(2018/04/11)
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- Sulfonated nanohydroxyapatite functionalized with 2-aminoethyl dihydrogen phosphate (HAP@AEPH2-SO3H) as a reusable solid acid for direct esterification of carboxylic acids with alcohols
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Sulfonated nanohydroxyapatite functionalized with 2-aminoethyl dihydrogen phosphate (HAP@AEPH2-SO3H) efficiently catalyzed direct esterification of carboxylic acids and alcohols with high selectivity toward the formation of esters in good to excellent yields. Our results clearly show that HAP@AEPH2-SO3H can be easily recovered by simple filtration and reused for subsequent five runs without any significant impact on yields of products. The main advantage of this methodology is easy and ecofriendly catalyst preparation, easy catalyst separation, practical simplicity, safe reaction conditions, recyclable catalyst and high products yields.
- Siavashi, Narges Yousefi,Akhlaghinia, Batool,Zarghani, Monireh
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p. 5789 - 5806
(2016/06/01)
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- Synthesis and esterification reactions of aryl diazomethanes derived from hydrazone oxidations catalyzed by TEMPO
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Diverse hydrazones were oxidized to the corresponding diazoalkanes using sodium hypochlorite in the presence of catalytic amounts of TEMPO (2,2,6,6-tetramethylpiperidinyloxy). A library of diverse benzhydryl esters and analogues was prepared from diazoalkanes obtained by this procedure.
- Perusquía-Hernández, Carolina,Lara-Issasi, Gonzalo R.,Frontana-Uribe, Bernardo A.,Cuevas-Ya?ez, Erick
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p. 3302 - 3305
(2013/06/27)
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- The Reaction between Acyl Halides and Alcohols: Alkyl Halide vs. Ester Formation
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In the reaction between an acyl halide and an alcohol the thermodynamically favoured products are the free carboxylic acid and the alkyl halide.The initial reaction is, generally, the formation of an ester and HHal.When the alcohol is very prone to yield an alkyl cation upon protonation by HHal, formed H2O exhibited a superior reactivity and competed successfully with the alcohol for the acyl halide making, therefore, ester formation practically confined to a triggering role.But, in those cases where the cation is less easily formed, ester formation was favoured and, consequently, became the necessary elementary step towards alkyl halide formation.Tis final product, on the other hand, might be extremely slow to form in an SN2 reaction between the protonated ester function and the halide ion.In these instances, therefore, as well as in the cases when a basic solvent competes for the proton of HHal, the ester is the final product.A notable exception of the situation above outlined, is given by α-hydroxy-α-phenylbenzeneacetic acid (2y), which appears to undergo direct chlorine-hydroxyl interchange through a quaternary intermediate (E), in the end collapsing to α-chloro-α-phenyl-benzeneacetic acid (4y).Different systems were compared using CH2Cl2 as a solvent under strictly similar conditions.Some 28 different substrates were tested for reaction with AcCl (1a), whereas the action of eight acyl halides (a) against (RS)-α-methylbenzenemethanol (2n) and α-phenylbenzenemethanol (2p), as well as the effect of five different solvents on the reaction between two alcohols (2p and 2-methyl-2-propanol, 2c) with 1a, were observed.
- Strazzolini, Paolo,Giumanini, Angelo G.,Verardo, Giancarlo
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p. 217 - 254
(2007/10/02)
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- FURTHER STUDIES ON THE EXTENDED HAMMETT EQUATION COMPRISING THE HYDROPHOBIC CONSTANT: REACTIVITY DATA FOR BENZOIC ACIDS, ARYLACETIC ACIDS, β-ARYLPROPIONIC ACIDS, trans- AND cis-CINNAMIC ACIDS, METHYL BENZOATES; DISSOCIATION CONSTANTS, DDM REACTION AND ALKALINE HYDROLYSIS IN VARIOUS W...
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The extended Hammett equation Δ = ρ? + h? comprising the hydrophobic constant ? is found to be effective in the title compounds and reactivities in various solvent mixtures.In 32 vol.percent tert-butanol-water hm decreases in the order ArCOOMe (-0.25), cis-ArCH=CHCOOH (-0.18), ArCOOH and ArCH2COOH (-0.16), ArCH2CH2COOH and trans-ArCH=CHCOOH (-0.07).For ArCOOH, mixtures like 40-60percent methanol, 50percent ethanol, 50percent acetone and 50percent dioxane give similar hm values of circa -0.05.For ArCH2COOH the effects of 3-iodo and 4-iodo substituents are acid-weakening in32percent tert-butanol.The consequences of the h? term for ρ, ?, and the averaging of ? values, are discussed.
- Hoefnagel, Anthonius J.,Wepster, Bartholomeus M.
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p. 119 - 135
(2007/10/02)
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- Investigation of Electronic Effects in the Pyridine and Pyridine N-Oxide Rings. Part 4. Kinetics and Mechanism of the Reaction of Diazodiphenylmethane with Substituted Carboxypyridine and 2-carboxypyridine N-Oxides in Dimethylforamide
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Rate constants for the reaction of 15 substituted carboxypyridines and four substituted 2-carboxypyridine N-oxides with diazodiphenylmethane (DDM) in dimethylformamide (DMF) were determined at 30 deg C, by the known spectrophotometric method.For comparison, rate constants for the raection of 12 substituted benzoic acids were determined under the same conditions.Kinetic and thermodynamic parameters obtained, together with products analyses, essentially verify the previously proposed reaction mechanism in this solvent.The empirical Hammett treatment has benn applied to the results, and it was shown that a scattered overall plot (ρ=1.019, log ko=-2.98, r=0.91, s=0.22, n=31) was obtained with additive ? constants from the corresponding ? values for the pyridine aza-group and N-oxide group and Hammett ? constants for substituents.Fairly good separate correlations were obtained from the data for substituted benzoic acids (ρ=1.07, log ko=-2.91, r=0.985, s=0.12, n=12), halogen- and nitro-substituted acids (ρ=1.18, log ko=-3.35, r=0.995, s=0.04, n=4).A far less satisfactory correlation was obtained when it was applied to the substituted carboxypyridines, including the N-oxides (ρ=1.15, log ko=-3.35, r=0.91, s=0.18, n=19).It was concluded that powerful solvent nucleophilic stabilisation of the reactant carboxylic acid in the initial state is greatly influenced by the type of substitution, substituent solvation, and probably also by the kind of electronic interaction of the particular substituent with the heteroaromatic nuclei.
- Radojkovic-Velickovic, Mirjana,Misic-Vukovic, Milica
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p. 1975 - 1977
(2007/10/02)
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- An Approach towards Identification of Product Precursors in the Solvolyses of Diarylmethyl p-Nitrobenzoates in Ethanol-Water Solvents
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The product ratios, ether:alcohol, for the solvolyses of the title compounds in ethanol-water solvent mixtures have been measured, and have been compared with ratios of the same products generated from the reactions of the corresponding diaryldiazomethanes in the same solvents.The ratios are similar although not always identical, and disparities are ascribed to solvation differences.The question of 'selectivities' of intermediates towards ethanol and water is addressed, and it is concluded that product ratios can be used as selectivity measures only when a single intermediate yields stable products.The present results thus throw little light on the reality or otherwise of stability-selectivity relationships in the present series.Internal return is suggested as an important component in the unassisted solvolysis of the esters.
- McLennan, Duncan J.,Martin, Peter L.
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p. 1099 - 1106
(2007/10/02)
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- Mechanism for Diacyl Peroxide Decomposition
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The presence of ion-pair intermediates in diacyl peroxide decomposition has been established.Various substituted (4-X-phenyl)phenylacetyl Y-benzoyl peroxides and three corresponding 4-X-benzhydryl-4-nitrobenzoic carbonic anhydrides (X = CH3, H, Cl) were prepared.All compounds decomposed in 90percent acetone-water (v/v), giving the ionic products ester, alkohol, and acid.The fraction of ester (R) was similar to that found in the solvolysis of substituted benzhydryl-N-nitrosoamides, indicating a similar spectrum of ion-pair intermediates.The yield of ester product could be increased markedly by the addition of common ion.The mixed carbonic carboxylic anhydrides were not products of peroxide decomposition in either nucleophilic or nonnucleophilic solvents and showed a lower decompositin rate than the peroxide.Lastly, both the peroxide and the mixed carbonic carboxylic anhydride decomposed in chloroform with net retention.Neither CIDNP nor any radical abstraction product was detected.
- Linhardt, R.J.,Murr, B.L.,Montgomery, E.,Osby, J.,Sherbine, J.
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p. 2242 - 2251
(2007/10/02)
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- Linear Free Energy ortho-Correlations in the Thiophene Series. Part IX (1). Kinetics of Esterification with Diazodiphenylmethane of Some 3-, 4- and 5-Substituted Thiophene-2-carboxylic Acids in Methanol
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The rate constants for the esterification of some 3-, 4- and 5-substituted thiophene-2-carboxylic acids with diazodiphenylmethane in methanol at 25 deg C have been measured.The reactivity of some para- and ortho-substituted benzoic acids has also been det
- Noto, Renato,Buscemi, Silvestre,Consiglio, Giovanni,Spinelli, Domenico
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p. 735 - 738
(2007/10/02)
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