- Hydrolysis of 1,8- and 2,3-naphthalic anhydrides and the mechanism of cyclization of 1,8-naphthalic acid in aqueous solutions
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Naphthalene-1,8-dicarboxylic acid, 1,8-Acid, cyclizes spontaneously in acidic aqueous solution to naphthalene-1,8-dicarboxylic anhydride, 1,8-An, and here we Present an ab initio study of the reaction pathway. The effect of pH on the hydrolysis of 1,8-An was analysed and compared with the hydrolysis of naphthalene-2,3-dicarboxylic anhydride, 2,3-An, to naphthalene-2,3-dicarboxylic acid, 2,3-Acid. The values of the pKa's of 1,8-Acid and 2,3-Acid were ca. 3.5 and 3.0, for monoanion formation, pKa1, and 5.5 and 5.0 for dianion formation, pKa2, respectively. Fluorimetric titration demonstrated that the diprotonated 2,3-Acid. AH2, was further protonated to yield AH3+. The pH-rate constant profile for 2,3-An hydrolysis showed a water reaction between pH's 1.0 and 6.0 and a base catalysed hydrolysis above pH 7.0. Under no condition was 2,3-An formed from 2,3-Acid. The pH dependent decomposition kinetics of 1,8-An is complex and, below pH 6.0, the pH-rate constant profile was fitted by assuming that both AH2 and AH3+ are in equilibrium with 1,8-An. The values of the equilibrium constants for 1,8-An formation from AH2 and AH3+ were ca. 4 and 100 in dilute and concentrated acid, respectively. Ab initio calculations for a possible reaction pathway connecting the undissociated 1,8-Acid to 1,8-An show a transition state where an intramolecular proton transfer is concerted with oxygen alignment towards the carbonyl centre. The planar intermediate is then dehydrated yielding a complex between water and 1,8-An.
- Barros, Teresa C.,Yunes, Santiago,Menegon, Guilherme,Nome, Faruk,Chaimovich, Hernan,Politi, Mario J.,Dias, Luis G.,Cuccovia, Iolanda M.
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- New Derivatizing Agents for Amino Acids and Peptides. 1. Facile Synthesis of N-Substituted 1-Cyanobenzisoindoles and Their Spectroscopic Properties
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2,3-Naphthalenedicarboxaldehyde (NDA) is shown to be a very useful reagent for the derivatization of primary amines, amino acids, and small peptides.The reaction of these amino compounds with NDA and cyanide ion produces highly fluorescent 2-substituted 1-cyanobenzisoindoles that are relatively stable.The physical and fluorescent properties of a variety of 1,2-disubstituted benzisoindoles are presented.
- Carlson, R. G.,Srinivasachar, K.,Givens, R. S.,Matuszewski, B. K.
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- "release and catch" catalysis by tungstate species for the oxidative cleavage of olefins
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The oxidative cleavage of olefins produces valuable carbonyl compounds, and thus, the development of green catalytic methods using H2O2 as an oxidant is highly desired. In this work, we have successfully developed an efficient catalytic system for the oxidative cleavage of olefins and related compounds using H2O2. In the presence of tungstate species supported on zinc-modified tin dioxide (W/Zn-SnO2), the oxidative cleavage of 1-methyl-1-cyclohexene proceeds efficiently through multistep reaction pathways involving oxygenation, hydrolysis, perhydrolysis, and isomerization reactions. In this reaction system, active peroxotungstate species, generated by the reaction of the supported tungstate species with H2O2, are released into the solution during the course of the reaction. At the end of the reaction (after the complete consumption of H2O2), the released tungstate species are re-captured by the support. The W/Zn-SnO2 catalyst can be reused at least nine times for the oxidative cleavage of 1-methyl-1-cyclohexene without loss of catalytic performance and can be applied to the oxidation of various other substrate molecules.
- Yoshimura, Yu,Ogasawara, Yoshiyuki,Suzuki, Kosuke,Yamaguchi, Kazuya,Mizuno, Noritaka
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p. 1662 - 1670
(2017/07/22)
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- Preparation method of 2,3-naphthalic acid
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The invention discloses a preparation method of 2,3-naphthalic acid, belonging to the technical field of preparation of organic compounds used as medical and liquid crystal intermediates. According to the preparation method, o-phthalaldehyde is used as a raw material, and through performing acetalation reaction, reducing reaction, hydrolysis reaction, cycloaddition reaction, dehydration reaction and hydrolysis reaction in sequence, finally the 2,3-naphthalic acid is prepared. The preparation method optimizes the reaction steps and conditions and has the advantages of reasonable synthetic route, high purity and yield of product, low production cost, low pollution, easy industrialization and the like.
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- Formation and decomposition of N-alkylnaphthalimides: Experimental evidences and ab initio description of the reaction pathways
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The kinetics of hydrolysis of 1,8-N-butyl-naphthalimide (1,8-NBN) to 1,8-N-butyl-naphthalamide (1,8-NBAmide) and of 2,3-N-butyl-naphthalimide (2,3-NBN) to 2,3-N-butyl-naphthalamide (2,3-NBAmide), as well as the formation of the respective anhydrides from the amides were investigated in a wide acidity range. 1,8-NBN equilibrates with 1,8-NBAmide in mild alkali. Under the same conditions 2,3-NBN quantitatively yields 2,3-NBAmide. Over a wide range of acidities the reactions of the 1,8- and 2,3-N-butyl-naphthalamides (or imides) yield similar products but with widely different rates and at distinct pH's. Anhydride formation in acid was demonstrated for 1,8-NBAmide. The reactions mechanisms were rationalized in the manifold pathways of ab initio calculations. The differences in rates and pH ranges in the reactions of the 1,8- and 2,3-N-butyl-naphthalamides were attributed to differences in the stability of the tetrahedral intermediates in alkali as well as the relative stabilities of the five and six-membered ring intermediates. The rate of carboxylic acid assisted 1,8-N-Butyl-naphthalamide hydrolysis is one of the largest described for amide hydrolysis models. Copyright
- De Barros, Teresa Cristina,Filho, Pedro Berci,Loos, Michel,Politi, Mario Jose,Chaimovich, Hernan,Cuccovia, Iolanda Midea
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p. 385 - 397
(2011/11/06)
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- Rapid chemoselective deprotection of benzyl esters by nickel boride
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Benzyl esters of a variety of acids can be chemoselectively cleaved on treatment with nickel boride in methanol at ambient temperature to give the parent carboxylic acids in high yields. Other protecting functionalities such as methyl, ethyl, tert-butyl, and trityl esters as well as benzyl ethers, tert-butyl ethers, and Nbenzylamides are unaffected under these conditions. Georg Thieme Verlag Stuttgart.
- Khurana, Jitender M.,Arora, Reema
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experimental part
p. 1127 - 1130
(2009/12/03)
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- Probing the spatial requirements for [60]fullerene-[60]fullerene π-stacking and the syn addition of [60]fullerenes across acenes
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The reaction between 2equiv of [60]fullerene and 6,8,15,17- tetraphenylheptacene-7,16-quinone leads to both cis and trans-bis[60]fullerene adducts. This result contrasts sharply with the highly diastereoselective syn additions of [60]fullerenes across 6,13-diphenylpentacene and 6,8,15,17-tetraphenylheptacene. The importance of spatially dependent [60]fullerene-[60]fullerene π-stacking interactions in promoting a syn addition of [60]fullerenes is discussed.
- Miller, Glen P.,Briggs, Jonathan
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p. 477 - 481
(2007/10/03)
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- Selenium(IV) oxide catalyzed oxidation of aldehydes to carboxylic acids with hydrogen peroxide
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A convenient method for oxidative transformation of aromatic, heteroaromatic and aliphatic aldehydes into carboxylic acids is presented. It is based on the oxidation of aldehydes in THF using 30% hydrogen peroxide in the presence of 5 molar % of selenium(IV) oxide. The scope and limitation of the method are discussed.
- Brzaszcz,Kloc,Maposah,Mlochowski
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p. 4425 - 4434
(2007/10/03)
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- o-Quinonoid heterocycles: Benzo[c]tellurophene
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The first synthesis of the o-quinonoid heterocycle benzo[c]tellurophene (5) has been achieved. Compound 5, prepared in two steps from the known 1,3-dihydrobenzo[c]tellurophene diiodide (6), was characterized spectroscopically, and by Diels-Alder trapping reactions.
- Morkved, Eva H.,Lakshmikantham,Cava, Michael P.
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p. 9149 - 9150
(2007/10/03)
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- Synthesis and Stability of Aryl Bis(nitrile oxides) with Potential as Curing Agents for Polysulfide Sealants
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Several aromatic bis(nitrile oxides) have been prepared as potential curing agents for sealants produced from thiol-terminated polysulfide liquid polymers.All were obtained by dehydrohalogenation of α-halo oximes and the requisite aldehydes were synthesized from either the dimethyl derivatives or the chloromethylated hydrocarbons.The direct chloromethylation of naphthalene which offered a convenient route to the naphthalene-1,4- and 1,5-bis(carbonitrile oxides) was re-examined.Also prepared were naphthalene-2,6-bis(carbonitrile oxide), anthracene-9,10-bis(carbonitrile oxide) and 4,4'-sulfonylbisbenzonitrile dioxide.The course of the reaction between naphthalene-2,3-dicarbaldehyde and hydroxylamine was established and shown to differ from that involving phthalaldehyde.Stabilities of the nitrile oxides at -15 deg C, 4 deg C and 25 deg C were assessed by spectroscopic means.
- Hanhela, Peter J.,Paul, D. Brenton
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p. 287 - 299
(2007/10/02)
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