- Synthesis, structural characterization, and antioxidant activities of 2,4-dinitrophenyl-hydrazone derivatives
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Thirty-two derivatives of 2,4-dinitro phenylhydrazone 1-32 were synthesized by one step reaction and characterized by spectroscopic techniques such as EI-MS and 1H-NMR. Compounds 1-32 were screened for their in vitro antioxidant activities. DPPH radical s
- Ahad, Ghulam,Khan, Momin,Khan, Asif,Ibrahim, Mohammad,Salar, Uzma,Kanwal,Khan, Khalid Mohammed,Perveen, Shahnaz
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p. 961 - 973
(2018/10/02)
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- Correlation analysis of reactivity in the oxidation of substituted benzyl alcohols by benzimidazolium dichromate - A kinetic and mechanistic aspects
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The oxidation of a number of para- and meta-substituted benzyl alcohols by benzimidazolium dichromate (BIDC), in dimethyl sulphoxide, leads to the formation of the corresponding benzaldehydes. The reaction is first order with respect to each BIDC and alcohol. The reaction is catalyzed by hydrogen ions and the dependence has the form kobs = a + b[H+]. The oxidation of [1,1-2H2]benzyl alcohol exhibited the presence of a substantial kinetic isotope effect. The rates of the oxidation of meta-substituted benzyl alcohols correlated best with Taft's σ1 and σR0 constants. The para-substituted compounds exhibited excellent correlation with σ1 and σRBA values. The polar reaction constants are negative. The rate of oxidation of benzyl alcohol was determined in nineteen organic solvents. An analysis of the solvent effect by multiparametric equations indicated the greater importance of the cation-solvating power of the solvents. Suitable mechanisms have been discussed.
- Kumar, Pravesh,Panday, Dinesh,Kothari, Seema
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p. 1207 - 1215
(2020/06/27)
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- Oxidized single-walled carbon nanotubes (swcns-cooh) as a new catalyst for the protection of carbonyl groups as hydrazones
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Nano-materials are considered as suitable heterogeneous catalysts for many organic reactions. Herein oxidized carbon nanotube (SWCNTs-COOH) has been reported as a heterogeneous catalyst, for protection of carbonyl groups as hydrazones in EtOH at 80 C. The reactions proceed smoothly with good to excellent yields, and the SWCNTs-COOH used can be recycled.
- Borazjani, Maryam Kiani,Safaei, Hamid Reza,Panahandeh, Majid,Kiani, Ali Reza,Kiani, Masoumeh,Mofarahi, Masoud
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p. 279 - 281
(2013/12/04)
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- Structure-Reactivity correlation in the oxidation of substituted benzaldehydes by tetraethylammonium chlorochromate
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Oxidation of 36 monosubstituted benzaldehydes by tetraethylammonium chlorochromate in dimethyl sulphoxide, leads to the formation of corresponding benzoic acids. The reaction is of first order with respect to chlorochromate and aldehydes. The reaction is promoted by H+; the H+ dependence has the form kobs = a + b[H+]. The oxidation of duteriated benzaldehyde exhibits substantial primary kinetic isotope effect. The reaction was studied in 19 different organic solvents and the effect of solvent was analyzed using Taft's and Swain's multiparametric equations. The rates of the oxidation of para- and meta-substituted benzaldehydes showed excellent correlation in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho-substituted benzaldehydes were correlated well with tetraperametric LDRS equation. The oxidation of para-substituted benzaldehydes is more susceptible to the delocalized effect than is the oxidation of ortho- and meta- substituted compounds, which display a greater dependence on the field effect. The positive value of h suggests the presence of an electron-deficient reaction centre in the rate-determining step. The reaction is subjected to steric acceleration by the orthosubstituents. A suitable mechanism has been proposed.
- Gehlot,Prasadrao,Sharma
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experimental part
p. 1173 - 1178
(2012/01/05)
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- Studies on the kinetics of tripropylammonium fluorochromate oxidation of some aromatic alcohols in non-aqueous media
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The oxidation of benzyl alcohol (BnOH) and a few para-substituted benzyl alcohols by tripropylammonium fluorochromate (TriPAFC) in dimethylsulphoxide (DMSO) leads to the formation of corresponding aldehydes. The reaction is first order each in TriPAFC and the alcohols. The reaction is catalysed by hydrogen ions. The hydrogen ion dependence has the form: kobs = a + b[H +]. The oxidation of α α′-dideuterio benzyl alcohol exhibited a substantial primary kinetic isotope effect (kH/k D = 5.45 at 303 K). Oxidation of benzyl alcohol was studied in 19 different organic solvents. The solvent effect has been analysed using Kamlet's and Swain's multiparametric equation. A mechanism involving a hydride ion transfer via chromate ester is proposed.
- Mansoor, S. Sheik,Shafi, S. Syed
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experimental part
p. 85 - 90
(2011/10/18)
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- An efficient tandem oxidative-protection reaction of benzylic alcohols to corresponding arylhydrazones and oximes
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A mild and efficient one-pot synthesis of hydrazones and oximes from the reaction of the oxidation product of benzyl alcohols and phenols by 3,6-bis(triphenylphosphonium)cyclohexene dichromate with phenylhydrazine, 2,4-dinitrophenylhydrazine, and hydroxylamine is described. Copyright Taylor & Francis Group, LLC.
- Badri, Rashid,Shushizadeh, Mohammad Reza
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p. 601 - 605
(2007/10/03)
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- Dowex polymer-mediated protection of carbonyl groups
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Dowex (strongly acidic cationic exchange resin) polymer is employed as solid acid catalyst for the clean and less hazardous protection of carbonyl compounds as phenylhydrazones and 2,4-dintrophenylhydrazones in ethanol under reflux conditions. The reactions proceed very smoothly and the yields of the derivatives are excellent. Copyright Taylor & Francis, Inc.
- Niknam, Khodabakhsh,Kiasat, Ali Reza,Karimi, Sadegh
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p. 2231 - 2236
(2007/10/03)
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- Ring transformation of cyclohepta[b]pyrimido[5,4-d]furan-8(7H),10(9H)- dionylium ion to the corresponding pyrrole derivatives via troponeimine intermediates: Photo-induced autorecycling oxidizing reactions of some amines
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Ring transformation of 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]furan- 8(7H),10(9H)-dionylium tetrafluoroborate 4+·BF 4- to 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]pyrrrole- 8(7H),10(9H)-dionylium tetrafluoroborate 6a-d+·BF 4- consists of the reaction of 4+· BF4- with amines and subsequent exchange of the counter-ion using aq. HBF4. Reactions of 4+·BF 4- with aniline and 4-substituted anilines afforded the corresponding pyrrole derivatives 6a-c+·BF4 - directly in good yields. On the other hand, reaction of 4 +·BF4- with benzylamine gave the troponeimine intermediate 9, which was not converted to 6d+· BF4- and reverted to 4+·BF 4- by adding HBF4; however, it was converted to 6d+·BF4- upon treatment with (COCl)2 or SOCl2, followed by exchange of the counter-ion. In a search for the characteristics of 9, inspection and comparison of the X-ray crystal analyses, NMR and UV-vis spectra, and CV measurement of 9 and N,N-disubstituted troponeimine derivatives 12 were carried out to suggest the remarkable structure of 12 having ionic C-O bonding between the imine-carbon atom and the oxygen atom of the barbituric acid moiety in the solid state. Thus, characteristics of 9 were ascribed to the sterically hindered and favorable conformation of N-protonated troponeimine intermediates. Furthermore, novel photo-induced oxidation reactions of a series of 4+·BF 4-, 5+·BF4-, and 6a,e+·BF4- towards some amines under aerobic conditions were carried out to give the corresponding imines in 455-8362% yields [based on compounds 4+, 5+, and 6a,e +], suggesting the oxidation reaction occurs in an autorecycling process. Mechanistic aspects of the amine-oxidation reaction are also postulated.
- Naya, Shin-Ichi,Nitta, Makoto
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p. 9139 - 9148
(2007/10/03)
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- A straightforward synthesis of some fused aza-arenes via nucleophilic displacement of a ring hydrogen atom in nitroarenes by aromatic hydrazone anions
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6-Nitroquinoline 6 undergoes direct cyclocondensation with aromatic aldehyde hydrazones 9 in the presence of sodium hydride in DMF at low temperature, giving the corresponding 3-aryl-1H-pyrazolo[3,4-f]quinolines 10 and/or 3-aryl[1,2,4]triazino[6,5-f]quino
- Uehata, Koji,Kawakami, Takehiko,Suzuki, Hitomi
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p. 696 - 702
(2007/10/03)
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- Substituent Dependence of the ?-Acceptor Induced Bond Cleavage Reactions of Benzyl Phenyl Ethers
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The relative C-O bond cleavage reaction rates (krel) of eight substituted benzyl phenyl ethers (BPE's) have been measured.These C-O bond cleavage reactions were thermally initiated by 2,3-dichloro-5,6-dicyanoquinone (DDQ).The equilibrium constants (K) for charge-transfer complex formation of these BPE's with the electron acceptors DDQ and TCNE in the solvent methylene chloride have also been determined at room temperature.The best correlation of log krel for DDQ reactions has been observed in these reactions.From this data, hydride transfer to DDQ is the rate-determining step of the reaction.
- Penn, John H.,Lin, Zhe
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p. 1554 - 1559
(2007/10/02)
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- A Novel Cleavage of Five-Membered Cyclic Acetals Using Sodium Hydrogen Telluride
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Under mild conditions, a variety of 1,3-dioxolanes are easily cleaved in high yields by treatment with sodium hydrogen telluride in ethanol.
- Lue, Ping,Fan, Wei-Qiang,Zhou, Xun-Jun
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p. 692 - 693
(2007/10/02)
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- EXCHANGE REACTIONS OF SUBSTITUTED BENZALDEHYDE HYDRAZONES
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Hydrazones IV, derived from substituted benzaldehydes and N-aminophthalimide, experience an exchange reaction with one equivalent of 2,4-dinitrophenylhydrazine under conditions free of added mineral acid to cleanly and irreversibly produce the related 2,4-dinitrophenylhydrazones V in good yields.Although literature melting points for compounds V may vary from one reference to another, the infrared spectra (ν (mull), cm-1; IV: 1770, 1710; V: 3280, 1615, 1580, 1510) of starting materials and products in the exchange process are strikingly different and permit ready characterization.
- Hearn, Michael J.,Sy, Karen Grace
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p. 339 - 342
(2007/10/02)
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- Kinetics and Mechanism of the Oxidation of Substituted Benzylamines by N-Chlorosuccinimide
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The oxidation of ortho-, meta-, and para-substituted benzylamines by N-chlorosuccinimide (NCS), to the corresponding benzaldehydes, is first-order with respect to NCS and the amine.The pH dependence of the reaction rate suggests that the unprotonated benzylamine is the reductant.There is no effect of added succinimide.NCS itself has been postulated as the reactive oxidising species.The oxidation of benzylamine exhibited a substantial primary kinetic isotope effect (kH/kD=6.20).The rates of oxidation of the meta- and para-substituted benzylamines were separately correlated in Taft and Swain's dual substituent parameter equations.For the para-substituted compounds, the best correlation is obtained with ?I and ?R+ values; meta-substituted compounds correlate with ?I and ?R0 values.The reaction constants have negative values.The oxidation rates of the ortho-substituted compounds yield an excellent correlation in a triparametric equation involving Taft's ?I and ?R+ values and Charton's steric parameter, V.A mechanism involving transfer of a hydride ion from the amine to the oxidant in the rate-determining step is proposed.
- Banerji, Kalyan K.
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p. 1015 - 1020
(2007/10/02)
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- A New Ring Opening Reaction of N-Aminophthalimide Hydrazones
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Araldehyde hydrazones III of N-aminophthalimide underwent rapid ring opening reactions initiated by the addition of excess base to their refluxing methanolic solutions.The products were conveniently isolated through liquid-liquid extraction as the stable
- Hearn, Michael J.,Rosenberg, Judith,Campbell, Mary L.
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p. 1405 - 1407
(2007/10/02)
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- Kinetics and Mechanism of the Oxidation of Substituted Benzyl Alcohols by Lead Tetraacetate
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The kinetics of the oxidation of benzyl alcohol to benzaldehyde by lead tetraacetate have been studied in benzene solution both in the absence and presence of pyridine.The values of the reaction constant ρ for the reactions in the absence and presence of pyridine at 303 K are -1.13 and -1.92 respectively.The activation enthalpies and entropies of the nine compounds are linearly related.The oxidation of α,α-dideuteriobenzyl alcohol indicated presence of a primary kinetic isotope effect.The reaction does not induce polymerisation of acrylonitrile.Probable mechanisms have been suggested.
- Bhatia, Indu,Banerji, Kalyan K.
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p. 1076 - 1092
(2007/10/02)
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