- Solvent and structural effects on the kinetics of the reactions of 2-substituted cyclohex-1-enylcarboxylic and 2-substituted benzoic acids with diazodiphenylmethane
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The rate constants for the reaction of 2-methyl-cyclohex-1-enylcarboxylic, 2-phenylcyclohex-1-enylcarboxylic, and 2-methylbenzoic and 2-phenylbenzoic acids with diazodiphenyl-methane were determined in 14 various solvents at 30°C. To explain the kinetic results through solvent effects, the second-order rate constants of the examined acids were correlated using the Kamlet-Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis, and the solvent effects on the reaction rates were analyzed in terms of initial and transition state contributions. The quantitative relationship between the molecular structure and the chemical reactivity has been discussed, as well as the effect of geometry on the reactivity of the examined molecules. The geometric data of all the examined compounds corresponding to the energy minima in solvent, simulated as dielectric continuum, obtained using semiempirical MNDO-PM3 energy calculations.
- Nikolic,Uscumlic,Juranic
-
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Read Online
- Tropylium-Catalyzed O-H Insertion Reactions of Diazoalkanes with Carboxylic Acids
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Herein, we describe the application of a nonbenzenoid aromatic carbocation, namely tropylium, as an organic Lewis acid catalyst in O-H functionalization reactions of diazoalkanes with benzoic acids. The newly developed protocol is applicable to a wide range of diazoalkane and carboxylic acid substrates with excellent efficiency (43 examples, up to 99% yield).
- Empel, Claire,Nguyen, Thanh Vinh,Koenigs, Rene M.
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supporting information
p. 548 - 553
(2021/01/26)
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- Hydrogen-bond-assisted transition-metal-free catalytic transformation of amides to esters
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The amide C-N cleavage has drawn a broad interest in synthetic chemistry, biological process and pharmaceutical industry. Transition-metal, luxury ligand or excess base were always vital to the transformation. Here, we developed a transition-metal-free hydrogen-bond-assisted esterification of amides with only catalytic amount of base. The proposed crucial role of hydrogen bonding for assisting esterification was supported by control experiments, density functional theory (DFT) calculations and kinetic studies. Besides broad substrate scopes and excellent functional groups tolerance, this base-catalyzed protocol complements the conventional transition-metal-catalyzed esterification of amides and provides a new pathway to catalytic cleavage of amide C-N bonds for organic synthesis and pharmaceutical industry. [Figure not available: see fulltext.]
- Huang, Changyu,Li, Jinpeng,Wang, Jiaquan,Zheng, Qingshu,Li, Zhenhua,Tu, Tao
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- An efficient metal-free oxidative esterification and amination of benzyl C-H bond
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An esterification and amination of benzylic C-H bonds was developed by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) under metal- and iodide-free conditions. Both carboxylic acids and amines could be used as ideal coupling partners for the oxidati
- Liu, Saiwen,Chen, Ru,He, Guowen,Zhang, Jin
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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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- Palladium-Catalyzed Carbonylative Synthesis of Benzyl Benzoates Employing Benzyl Formates as Both CO Surrogates and Benzyl Alcohol Sources
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An efficient and convenient palladium-catalyzed carbonylation reaction for the synthesis of benzyl benzoates from aryl bromides has been developed. Benzyl formates have been explored as a new type of efficient and useful CO sources and also reaction partners. A wide range of benzyl benzoates was obtained in good to excellent yields.
- Lai, Ming,Qi, Xinxin,Wu, Xiao-Feng
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supporting information
p. 3776 - 3778
(2019/06/24)
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- Preparation method for synthesizing ester compound by using N-Boc amide as raw material
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The invention relates to a preparation method for synthesizing an ester compound by using N-Boc amide as a raw material. According to the method, an inorganic base is used as a catalyst; the N-Boc amide is subjected to an intermolecular nucleophilic substitution reaction with various alcohol compounds; and various ester compounds can be efficiently obtained. The method has the advantages of beingmild in reaction condition, simple and convenient to operate, high in yield and favorable in functional-group compatibility.
- -
-
Paragraph 0042; 0043
(2019/03/28)
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- Cesium Carbonate Catalyzed Esterification of N-Benzyl- N-Boc-amides under Ambient Conditions
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We report a general activated amide to ester transformation catalyzed by Cs2CO3. Using this approach, esterification proceeds under relatively mild conditions and without the need for a transition metal catalyst. This method exhibits broad substrate scope and represents a practical alternative to existing esterification strategies. The synthetic utility of this protocol is demonstrated via the facile synthesis of crown ether derivatives and the late-stage modification of a representative natural product and several sugars in reasonable yields.
- Ye, Danfeng,Liu, Zhiyuan,Chen, Hao,Sessler, Jonathan L.,Lei, Chuanhu
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supporting information
p. 6888 - 6892
(2019/09/07)
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- Base-Promoted Amidation and Esterification of Imidazolium Salts via Acyl C-C bond Cleavage: Access to Aromatic Amides and Esters
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Imidazolium salts have been effectively employed as suitable acyl transfer agents in amidation and esterification in organic synthesis. The weak acyl C(O)-C imidazolium bond was exploited to generate acyl electrophiles, which further react with amines and alcohols to afford amides and esters. The broad substrate scope of anilines and benzylic amines and base-promoted conditions are the benefits of this route. Interestingly, phenol, benzylic alcohols, and a biologically active alcohol can also be subjected to esterification under the optimized conditions.
- Karthik, Shanmugam,Muthuvel, Karthick,Gandhi, Thirumanavelan
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p. 738 - 751
(2019/01/24)
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- Ester Formation via Symbiotic Activation Utilizing Trichloroacetimidate Electrophiles
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Trichloroacetimidates are useful reagents for the synthesis of esters under mild conditions that do not require an exogenous promoter. These conditions avoid the undesired decomposition of substrates with sensitive functional groups that are often observed with the use of strong Lewis or Br?nsted acids. With heating, these reactions have been extended to benzyl esters without electron-donating groups. These inexpensive and convenient methods should find application in the formation of esters in complex substrates.
- Mahajani, Nivedita S.,Meador, Rowan I. L.,Smith, Tomas J.,Canarelli, Sarah E.,Adhikari, Arijit A.,Shah, Jigisha P.,Russo, Christopher M.,Wallach, Daniel R.,Howard, Kyle T.,Millimaci, Alexandra M.,Chisholm, John D.
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p. 7871 - 7882
(2019/06/27)
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- Photocatalytic oxidation synthesis method of diphenylmethanol ester
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The invention discloses a photocatalytic oxidation synthesis method of diphenylmethanol ester. The method is characterized in that diphenylmethanol and carboxylic acid are used as reaction substrates,2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and ter
- -
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Paragraph 0021; 0042; 0043
(2019/03/08)
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- Metal-Free Aerobic Oxidative C–O Coupling of C(sp3)–H with Carboxylic Acids Catalyzed by DDQ and tert-Butyl Nitrite
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The formation of the C–O bond is one of the hot topics in the area of C(sp3)–H bond functionalization. A metal-free oxidative cross-coupling between benzylic C(sp3)–H bond and carboxylic acids has been developed. The reactions were performed with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as the catalyst, tert-butyl nitrite (TBN) as the co-catalyst, and molecular oxygen as the terminal oxidant. A variety of diarylmethanes could be successfully coupled with various carboxylic acids to obtain diarylmethanol esters in good to excellent yields. In addition, 2-benzylbenzoic acids could be converted into phthalides in moderate yields through an intramolecular oxidative cyclization.
- Pan, Decheng,Pan, Zilong,Hu, Zhiming,Li, Meichao,Hu, Xinquan,Jin, Liqun,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu
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p. 5650 - 5655
(2019/08/20)
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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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supporting information
p. 1855 - 1859
(2018/04/11)
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- Aerobic oxidative esterification and thioesterification of aldehydes using dibromoisocyanuric acid under mild conditions: No metal catalysts required
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A practical direct method for the direct preparation of esters and thioesters from aldehydes is described. Esters and thioesters were synthesized by oxidative esterification and thioesterification via in situ generated acyl bromide intermediates, which were used to react with various alcohols and thiols. The esterification and thioesterification were readily performed in the presence of dibromoisocyanuric acid in dichloromethane, without any metal catalysts and under mild conditions. By using this reaction protocol, various esters and thioesters were prepared in high yields. This effective method offers a promising approach for the facile esterification and thioesterification of aldehydes.
- Kwon, Young-Do,La, Minh Thanh,Kim, Hee-Kwon
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p. 10833 - 10841
(2018/07/05)
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- Zn-Catalyzed tert-Butyl Nicotinate-Directed Amide Cleavage as a Biomimic of Metallo-Exopeptidase Activity
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A two-step catalytic amide-to-ester transformation of primary amides under mild reaction conditions has been developed. A tert-butyl nicotinate (tBu nic) directing group is easily introduced onto primary amides via Pd-catalyzed amidation with tert-butyl 2-chloronicotinate. A weak base (Cs2CO3 or K2CO3) at 40-50 °C can be used provided that 1,1′-bis(dicyclohexylphosphino)ferrocene is selected as ligand. The tBu nic activated amides subsequently allow Zn(OAc)2-catalyzed nonsolvolytic alcoholysis in tBuOAc at 40-60 °C under neutral reaction conditions. The activation mechanism is biomimetic: the C3-ester substituent of the pyridine in the directing group populates the trans-conformer suitable for Zn-chelation, C=Oamide-Zn-Ndirecting group, and Zn-coordinated alcohol is additionally activated as a nucleophile by hydrogen bonding with the acetate ligand of the catalyst. Additionally, the acetate ligand assists in intramolecular O-to-N proton transfer. The chemoselectivity versus other functional groups and compatibility with challenging reaction partners, such as peptides, sugars, and sterols, illustrates the synthetic applicability of this two-step amide cleavage method. The tBu nic amides do not require purification before cleavage. Preliminary experiments also indicate that other weak nucleophiles can be used such as (hetero)arylamines (transamidation) as exemplified by 8-aminoquinoline.
- Wybon, Clarence C. D.,Mensch, Carl,Hollanders, Charlie,Gadais, Charlène,Herrebout, Wouter A.,Ballet, Steven,Maes, Bert U. W.
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p. 203 - 218
(2018/01/17)
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- Selective carboxylation of reactive benzylic C–H bonds by a hypervalent iodine(III)/inorganic bromide oxidation system
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An oxidation system comprising phenyliodine(III) diacetate (PIDA) and iodosobenzene with inorganic bromide, i.e., sodium bromide, in an organic solvent led to the direct introduction of carboxylic acids into benzylic C–H bonds under mild conditions. The unique radical species, generated by the homolytic cleavage of the labile I(III)–Br bond of the in situ-formed bromo-λ3-iodane, initiated benzylic carboxylation with a high degree of selectivity for the secondary benzylic position.
- Dohi, Toshifumi,Iwasaki, Kosuke,Kita, Yasuyuki,Morimoto, Koji,Tsunoda, Yusuke,Ueda, Shohei
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p. 1087 - 1094
(2020/05/06)
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- PROCESS FOR THE CATALYTIC DIRECTED CLEAVAGE OF AMIDE-CONTAINING COMPOUNDS
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The present invention relates to a catalytic method for the conversion of amide-containing compouds by means of a build-in directing group and upon the action of a heteronucleophilic compound (in se an amine (RNH2 or RNHR') or an alcohol (ROH) or a thiol (RSH)) in the presence of a metal catalyst to respectively esters, thioesters, carbonates, thiocarbonates and to what is defined as amide-containing compounds (such as carboxamides, urea, carbamates, thiocarbamates). The present invention also relates to these amide-containing compounds having a build-in directing group (DG), as well as the use of such directing groups in the catalytic directed cleavage of N-DG amides with the use of heteronucleophiles (in se an amine (RNH2 or RNHR') or an alcohol (ROH) or thiol (RSH)).
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- METHOD OF CONVERTING ALCOHOL TO HALIDE
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The present invention relates to a method of converting an alcohol into a corresponding halide. This method comprises reacting the alcohol with an optionally substituted aromatic carboxylic acid halide in presence of an N-substituted formamide to replace a hydroxyl group of the alcohol by a halogen atom. The present invention also relates to a method of converting an alcohol into a corresponding substitution product. The second method comprises: (a) performing the method of the invention of converting an alcohol into the corresponding halide; and (b) reacting the corresponding halide with a nucleophile to convert the halide into the nucleophilic substitution product.
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Page/Page column 50; 114; 124
(2017/01/02)
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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 of esters by in situ formation and trapping of diazoalkanes
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A general method has been developed for the in situ formation and trapping of diazoalkanes by carboxylic acids to form esters. The method is applicable to a large variety of carboxylic acids using diazo compounds that are formed from the hydrazones of benzaldehydes and aryl ketones. In situ reaction monitoring with IR spectroscopy (ReactIR) was used to demonstrate that slow addition of the hydrazone to a mixture of oxidant and carboxylic acid avoids the buildup of the diazo compound. This method enables the safe preparation of esters from simple precursors without isolation of diazo compounds.
- Squitieri, Richard A.,Shearn-Nance, Galen P.,Hein, Jason E.,Shaw, Jared T.
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supporting information
p. 5278 - 5284
(2016/07/14)
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- A novel lanthanum metal-assisted reaction of diaryl ketones and electrophiles
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A novel and efficient lanthanum metal-assisted carbon-carbon bond formation of diaryl ketones and various electrophiles, such as carbonyl compounds, esters, nitriles, and epoxides, has been developed. When diaryl ketones were allowed to react with dialkyl ketones in the presence of lanthanum metal and a catalytic amount of iodine, the cross pinacol coupling reaction proceeded to give the corresponding unsymmetrical 1,2-diols in moderate to good yields. α-Hydroxy ketones were prepared by the lanthanum metal-assisted reaction of diaryl ketones with esters or nitriles, followed by hydrolysis with aq HCl. It is interesting to note that for the epoxides, the coupling reaction proceeded via the Meinwald rearrangement of epoxides to give the corresponding 1,2-diols.
- Umeda, Rui,Ninomiya, Masashi,Nishino, Toshiaki,Kishida, Makoto,Toiya, Shunsuke,Saito, Tomoki,Nishiyama, Yutaka,Sonoda, Noboru
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p. 1287 - 1291
(2015/03/05)
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- Convenient Formation of Diphenylmethyl Esters Using Diphenylmethyl Trichloroacetimidate
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Diphenylmethyl trichloroacetimidate is a useful reagent for the protection of carboxylic acids as their corresponding diphenylmethyl esters. These esterifications proceed rapidly without the need for an added catalyst or promoter. A variety of carboxylic
- Adhikari, Arijit A.,Shah, Jigisha P.,Howard, Kyle T.,Russo, Christopher M.,Wallach, Daniel R.,Linaburg, Matthew R.,Chisholm, John D.
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p. 283 - 287
(2014/02/14)
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- Cu-catalyzed esterification reaction via aerobic oxygenation and C-C bond cleavage: An approach to α-ketoesters
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The Cu-catalyzed novel aerobic oxidative esterification reaction of 1,3-diones for the synthesis of α-ketoesters has been developed. This method combines C-C σ-bond cleavage, dioxygen activation and oxidative C-H bond functionalization, as well as provides a practical, neutral, and mild synthetic approach to α-ketoesters which are important units in many biologically active compounds and useful precursors in a variety of functional group transformations. A plausible radical process is proposed on the basis of mechanistic studies.
- Zhang, Chun,Feng, Peng,Jiao, Ning
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supporting information
p. 15257 - 15262
(2013/11/06)
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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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- Solvent and structural effects on the activation parameters of the reaction of carboxylic acids with diazodiphenylmethane
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The kinetics of the reaction of benzoic, 2-methylbenzoic, phenylacetic, cyclohex-1-enecarboxylic, 2-methylcyclohex-1-enecarboxylic, and cyclohex-1-eneacetic acids with diazodiphenylmethane was studied at 30, 33, 37, 40, and 45°C in a set of 12 protic and aprotic solvents. The reactions were found to follow the second-order kinetics. The activation energy as well as the activation parameters, such as the standard entropy, the standard enthalpy, and the standard Gibbs energy of the activation, was calculated from the second-order rate constants. The solvent and structural effects on the activation energy and the standard Gibbs energy of activation, for each examined compound, were analyzed. The results of Kamlet-Taft multiple correlation analysis show that the specific solvent-solute interactions play a dominant role in the governing of the reaction. The signs of the equation coefficients support the proposed reaction mechanism.
- Nikolic,Uscumlic
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p. 256 - 265
(2013/04/24)
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- Copper-catalyzed benzylic oxidation of C(sp3)-H bonds
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A selective oxidation of benzylic C(sp3)-H bonds to C(sp 3)-O bonds catalyzed by copper complexes of quinoline-imine ligands was developed with peresters as oxidants under mild reaction conditions, which converted benzylic methylenes directly into benzylic alcohols and esters by means of direct C-H bond functionalization.
- Zhang, Bo,Zhu, Shou-Fei,Zhou, Qi-Lin
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supporting information
p. 2033 - 2037
(2013/03/13)
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- A metal-free oxidative esterification of the benzyl C-H bond
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An efficient metal-free oxidative esterification of benzyl C-H bonds was developed. Using tetrabutylammonium iodide as catalyst and tert-butyl hydroperoxide as co-oxidant, benzylic substrates could react smoothly with various carboxylic acids to give the esters with good to excellent yields. The method was also suitable for the O-protection of N-Boc amino acids. The reaction mechanism was primarily investigated and a radical process was proposed. Copyright
- Feng, Jie,Liang, Shuai,Chen, Shan-Yong,Zhang, Ji,Fu, Song-Sen,Yu, Xiao-Qi
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experimental part
p. 1287 - 1292
(2012/06/15)
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- DDQ-catalyzed oxidative C-O coupling of sp3 C-H bonds with carboxylic acids
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Da-ddy, DDQ: By using catalytic amounts of DDQ combined with MnO 2 as oxidant, an efficient oxidative C-O coupling of benzylic sp 3 C-H bonds with carboxylic acids affords a series of carboxylic esters in 70-98 % yields. A wide range
- Yi, Hong,Liu, Qiang,Liu, Jie,Zeng, Ziqi,Yang, Yuhong,Lei, Aiwen
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p. 2143 - 2146
(2013/01/15)
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- Benzylic-acetoxylation of alkylbenzenes with PhI(OAc)2 in the presence of catalytic amounts of TsNH2 and I2
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Treatment of alkylbenzenes with (diacetoxyiodo)benzene in the presence of catalytic amounts of p-toluenesulfonamide or p-nitrobenzenesulfonamide, and molecular iodine in 1,2-dichloroethane at 60 °C gave the corresponding (α-acetoxy)alkylbenzenes in good to moderate yields. The present reaction is a simple method for the introduction of an acetoxy group to the benzylic position of alkylbenzenes.
- Baba, Haruka,Moriyama, Katsuhiko,Togo, Hideo
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experimental part
p. 4303 - 4307
(2011/08/22)
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- Diazo preparation via dehydrogenation of hydrazones with "activated" DMSO
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We report that "activated" dimethyl sulfoxide efficiently dehydrogenates hydrazones to the respective diazo species at -78°C. Under optimized conditions, triethylamine hydrochloride is removed quantitatively by vacuum filtration to provide solutions of diazo compounds. Stable diazo species can be isolated in high yield, or alternatively, the direct treatment of these solutions with carboxylic acids provides esters.
- Javed, Muhammad I.,Brewer, Matthias
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p. 1789 - 1792
(2008/02/02)
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- Efficient method for the preparation of inverted alkyl carboxylates and phenyl carboxylates via oxidation-reduction condensation using 2,6-dimethyl-1,4-benzoquinone or simple 1,4-benzoquinone
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Oxidation-reduction condensation using in situ formed alkoxydiphenylphosphines, 2,6-dimethy-1,4-benzoquinone, and carboxylic acids provides a useful method for the preparation of inverted tertiary alkyl carboxylates from the corresponding chiral tertiary alcohols under mild and neutral conditions. Similarly, it has afforded alkyl carboxylates successfully in good-to-high yields by the combined use of alkoxydiphenylphosphines having primary, secondary, or tertiary alkoxy groups, carboxylic acids, and simple 1,4-benzoquinone. When chiral secondary or tertiary alcohols are used, the corresponding inverted secondary or tertiary alkyl carboxylates are also obtained in good-to-high yields. In addition, a convenient method for the preparation of phenyl carboxylates in high yields has been established by utilizing oxidation-reduction condensation in toluene at 110 °C using phenoxydiphenylphosphines in situ-formed from phenols and chlorodiphenylphosphine, 2,6-dimethyl-1,4-benzoquinone, and carboxylic acids.
- Shintou, Taichi,Fukumoto, Kentaro,Mukaiyama, Teruaki
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p. 1569 - 1579
(2007/10/03)
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- Preparation of various carboxylic acid esters from bulky alcohols and carboxylic acids by a new type oxidation-reduction condensation using 2,6-dimethyl-1,4-benzoquinone
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A new-type oxidation-reduction condensation by using 2,6-dimethyl-1,4-benzoquinone (DMBQ), carboxylic acids and in situ formed alkoxydiphenylphosphines (1) including the bulky alkoxy group-substituted ones proceeded smoothly to afford the corresponding carboxylic acid esters in good to high yields. Alkoxydiphenylphosphines were formed in situ by treating either N,N-dimethylaminodiphenylphosphine (Ph2PNMe2) with primary or secondary alcohols or chlorodiphenylphosphine with the lithium salts of primary, secondary and tertiary alcohols.
- Mukaiyama, Teruaki,Kikuchi, Wataru,Shintou, Taichi
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p. 300 - 301
(2007/10/03)
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- Efficient Method for the Preparation of Primary, Inverted Secondary and Tertiary Alkyl Carboxylates from Alcohols and Carboxylic Acids by a New Type of Oxidation-Reduction Condensation Using Simple 1,4-Benzoquinone
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A new type of oxidation-reduction condensation using in situ formed alkoxydiphenylphosphines (i.e., diphenylphosphinite esters), easily available 1,4-benzoquionone and carboxylic acids provides a new and efficient method for the preparation of alkyl carboxylates from the corresponding alcohols under mild and neutral conditions. Further, the yields of the corresponding inverted carboxylates were equally high in the case of chiral secondary or tertiary alcohols.
- Shintou, Taichi,Mukaiyama, Teruaki
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p. 1100 - 1101
(2007/10/03)
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- Efficient method for the preparation of carboxylic acid alkyl esters or alkyl phenyl ethers by a new-type of oxidation-reduction condensation using 2,6-dimethyl-1,4-benzoquinone and alkoxydiphenylphosphines
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A new-type of oxidation-reduction condensation proceeded smoothly to afford carboxylic acid alkyl esters or alkyl phenyl ethers in good to high yields by combined use of alkoxydiphenylphosphines (1) having primary, bulky secondary or tertiary alkoxy groups, a mild quinone-type oxidant such as 2,6-dimethyl-1,4-benzoquinone (DMBQ) and carboxylic acids or phenols. Generally, alkoxydiphenylphosphines were prepared easily from chlorodiphenylphosphine (2) and alcohols in the presence of pyridine, and were isolated by distillation. On the other hand, the phosphines 1 were also prepared in situ from N,N-dimethylaminodiphenylphosphine (3a) and primary or secondary alcohols while primary, bulky secondary or tertiary alkoxydiphenylphosphines were alternatively formed in situ by adding 2 to the "BuLi-treated alcohols in order to perform the above reactions by a one-pot procedure from alcohols and nucleophiles. The reaction of thus formed 1, DMBQ and carboxylic acids or phenols afforded the corresponding alkylated products, including hindered secondary and tertiary alkylated ones, in good to high yields at room temperature. In the case of using chiral secondary alcohols, the corresponding carboxylic acid alkyl esters were obtained as well in high yields with perfect inversion of stereochemistry by SN2 replacement.
- Shintou, Taichi,Kikuchi, Wataru,Mukaiyama, Teruaki
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p. 1645 - 1667
(2007/10/03)
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- Studies in polyphenol chemistry and bioactivity. 2. Establishment of interflavan linkage regio- and stereochemistry by oxidative degradation of an O-alkylated derivative of procyanidin B2 to (R)-(-)-2,4-diphenylbutyric acid
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The assignment of interflavan bond regio- and stereochemistry in oligomeric proanthocyanidins has in the past relied on empirical spectroscopic techniques which are influenced by the conformation of the C rings. Only recently was the 4,8-regiochemistry of procyanidin B2 (3b) firmly established by 2-dimensional NMR methods. We describe herein the proof of 4β-stereochemistry in 3b by oxidative degradation of the derivative 3d bearing differential (O-benzyl and O-methyl) protecting groups in its 'top' and 'bottom' epicatechin moieties, to (R)-(-)-2,4-diphenylbutyric acid. The key elements of the degradative process are (1) removal of the C-3 alcohol functions through a modified Barton deoxygenation employing hypophosphorous acid as the reducing agent; (2) deprotection of the 'top' unit by hydrogenolysis, followed by exhaustive aryl triflate formation with N,N-bis-(trifluoromethanesulfonyl)aniline and DBU in DMF; (3) hydrogenolytic deoxygenation of the 'top' unit over Pearlman's catalyst with concomitant scission of the O-C2 bond; (4) selective oxidation of the 'bottom' unit with NaIO4/RuCl3. The hitherto unreported absolute configuration of (-)-2,4-diphenylbutyric acid was established as R by X-ray crystal structure analysis of the (R)-(+)-α-methylbenzylamine salt. As a corollary, the selectivity of hydrogenolytic and solvolytic reactions of epicatechin-derived tetrasulfonates has been investigated.
- Kozikowski, Alan P.,Tueckmantel, Werner,George, Clifford
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p. 5371 - 5381
(2007/10/03)
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- Oxidation of ethers with the system aluminum tri-tert-butylate-tert-butyl hydroperoxide
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The system aluminum tri-tert-butylate-tert-butyl hydroperoxide oxidizes ethers containing α-methylene and α-methine CH bonds: dialkyl, phenyl alkyl, benzyl alkyl, and benzhydryl alkyl. The process involves oxidation of methylene and methine C-H bonds to α-hydroperoxides, followed by their reaction with the aluminum alcoholate. Decomposition of aluminum-containing peroxides yields the final reaction products.
- Stepovik,Martynova,Dodonov
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p. 257 - 262
(2007/10/03)
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- Ring-chain tautomerism. Part 10 +. The reaction of oxocarboxylic acids with diazodiphenylmethane
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The rate coefficients for the esterification of a series of oxocarboxylic acids with diazodiphenylmethane have been determined in ethanol or 2-methoxyethanol at 30.0°C. These and the rates of reaction with model compounds have been used to estimate the equilibrium constants for ring-chain tautomerism for the oxocarboxylic acids.
- Bowden, Keith,Misic-Vukovic, Milica M.,Ranson, Richard J.
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p. 1601 - 1606
(2007/10/03)
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- Borderline mechanisms involving ion-molecule pairs for the nucleophilic substitution reactions of benzhydrol and its derivatives. Facile formation and cleavage of diphenylmethyl ethers for the protection of hydroxyl groups
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Nucleophilic substitution reactions of benzhydrol and its derivatives, in refluxing benzene in the presence of para-toluenesulfonic acid, took different routes depending on whether paratoluenesulfonic acid was used in excess or in catalytic amounts. In the first case the reactions took place via benzhydryl carbocations and in the second case they proceeded via intimate ion-molecule pairs. On the basis of this study, facile methods for introduction and removal of CHPh2 as a protective group of alcohols are presented.
- Paredes, Rodrigo,Perez, Ruby L.
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p. 2037 - 2038
(2007/10/03)
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- Preparation of diphenylmethyl esters by Oxone oxidation of benzophenone hydrazone
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Oxone was found to be an efficient oxidizing reagent of benzophenone hydrazone for the preparation of diphenylmethyl esters (benzhydryl, Dpm).
- Curini, Massimo,Rosati, Ornelio,Pisani, Emanuela,Cabri, Walter,Brusco, Stefano,Riscazzi, Massimiliano
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p. 1239 - 1240
(2007/10/03)
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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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- THE REACTIONS OF N-BENZOYLPEROXYCARBAMIC ACID WITH AZINES AND IMINES
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N-Benzoylperoxycarbamic acid (BPC) was found to react generally with imines and azines to form oxaziridines rather than N-oxides.The imine products were stable, but those found from azines apparently were unstable and converted to ketones or aldehydes plus diazo compounds.
- Paredes, Rodrigo,Bastos, Holger,Montoya, Raul,Chavez, Alba Lucia,Dolbier, William R.,Burkholder, Conrad R.
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p. 6821 - 6830
(2007/10/02)
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- O-DIPHENYLMETHYLATION OF ALCOHOLS AND CARBOXYLIC ACIDS USING DIPHENYLMETHYL DIPHENYL PHOSPHATE AS ALKYLATING AGENT
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Diphenylmethyl diphenyl phosphate reacts quickly under mild conditions with various alcohols and carboxylic acids towards diphenyl-methyl ethers and esters respectively while hydroxyacids can be selectively alkylated at the alcohol site.
- Kolovos, Miltiadis,Froussios, Cleanthis
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p. 3909 - 3912
(2007/10/02)
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- Nitrosation of the N-Alkyl-O-acylhydroxylamines. A New Deamination Method.
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The nitrosation of N-alkyl-O-acylhydroxylamines leads to immediate decomposition at dry ice temperatures; the corresponding ester and nitrous oxide are formed.An 18O study has shown that the nitroso-O-acylhydroxylamines fragment directly rather than undergo a rearrangement reaction (as observed with the nitrosoamides).The product yields are respectable, especially at low tempreatures, and the method has promise for the generation of high energy carbonium ions.
- White, Emil H.,Ribi, Max,Cho, Lee K.,Egger, Notker,Dzadzic, Petar M.,Todd, Michael J.
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p. 4866 - 4871
(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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- The Influence of the Solvent on Organic Reactivity. Part 5. Kinetics of the Reaction of Diazodiphenylmethane with Benzoic Acid in Branched-chain Alkanols and in Electronegatively Substituted Alcohols
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Rate coefficents at 30.0 deg C are presented for the reaction of diazodiphenylmethane and benzoic acid in five branched-chain alkanols and in nine electronegatively substituted alcohols.As in earlier work, correlation analysis of log k values involves multiple regression on the ?* value of the group R1 in the alcohol R1OH, the Kirkwood function of dielectric constant f(ε)=(ε-1)/(2ε+1), and nγH, the number of hydrogen atoms in the γ-position of the alcohol.The results for branched-chain alcohols provide further examples of the acceleratory effect of γ-hydrogen atoms.A correlation equation based on 27 alkanols and phenyl-substituted alcohols, for which ?* lies between -0.325 and +0.215, can be applied with reasonable success to seven electronegatively substituted alcohols, for which ?* lies in the range 0.07-0.92. 2-Methoxy- and 2-phenoxy-ethanol show marked deviations.Correlation equations properly incorporating the data for the electronegatively substituted alcohols are finally presented.
- Mather, David,Shorter, John
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p. 1179 - 1184
(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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- The Separation of Polar Steric Effects. Part 14. Kinetics of the Reactions of Benzoic Acid and of ortho-Substituted Benzoic Acids with Diazodiphenylmethane in Various Alcohols
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The main results now discussed are rate coefficients for the reactions of benzoic acid and 32 ortho-substituted benzoic acids with diazodiphenylmethane (DDM) at 30.0 deg C in 11 alcohols including 2-methoxyethanol.The reaction involves a rate-determining proton transfer.The results have been subjected to correlation analysis in two ways. (a) For the reactions of a given acid in the various alcohols, the log k values are correlated through multiple regression on appropriate solvent parameters. (b) For reactions in a given alcohol, the log k values for the various acids are correlated by using the appropriate form of the extended Hammett equation involving inductive, resonance, and steric parameters.Analyses of type (a), as in earlier work, involve the ?* value of the group R in the alcohol ROH, the Kirkwood function of dielectric constant, f(ε)=(ε-1)/(2ε+1) and nγH, the number of hydrogen atoms in the γ-position in the alcohol.These correlations yield information on the influence of ortho-substituents on the relative importance of specific and non-specific solvent effects.In analyses of type (b) the correlation equations are established with a limited set of substituents (up to 18), whose characteristic parameters ?I, ?R, and υ (determined by Charton) are well established, and are unlikely to show effects due to hydrogenbonding or substituent conformation.The results for other substituents are then interpreted by comparing log k(calc.) from a correlation expression with log k(obs.).
- Aslam, Hanif M.,Burden, Alan G.,Chapman, Norman B.,Shorter, John,Charton, Marvin
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p. 500 - 508
(2007/10/02)
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