- Ammonium hydrotribromide salts as convenient and selective brominating agents of aryl methyl ketones
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A simple and improved protocol for the α-monobromination of acetophenone and acetyl carbazole derivatives using different ammonium hydrotribromide salts under mild reaction condition was described.
- Badali, Mohammad,Khalafy, Jabbar,Alidoost, Elnaz,Aghazadeh, Masomeh
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p. 859 - 863
(2016/11/21)
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- Sodium hypochlorite-promoted novel synthesis of organic ammonium tribromides and application of phenanthroline hydrotribromide in chemoselective oxidation of organic sulfides by hydrogen peroxide
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A novel method of synthesis of organic ammonium tribromides (OATBs) is developed by using an inexpensive and eco-friendly sodium hypochlorite as oxidant for conversion of Br to Br3 . The OATBs thus prepared include both quaternary ammonium tribromides and N-heterocyclic tribromides. A new addition to the family of OATBs is made in the form of phenanthroline hydrotribromide. The efficacy of this new tribromide as catalyst is ascertained in the oxidative transformation of organic sulfides to their corresponding sulfoxides and sulfones by hydrogen peroxide.
- Dey, Madhudeepa,Dey, Rupa R.,Dhar, Siddhartha S.
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supporting information
p. 631 - 633
(2014/05/20)
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- A peptide bromoiodinane approach for asymmetric bromolactonization
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A series of 37 peptides containing an iodo-aryl amide active site were generated by means of both solid phase and conventional synthesis. These peptides were screened for asymmetric induction in the bromolactonization of 4-phenyl-4-pentenoic acid based on the generation of chiral bromoiodinane bromenium sources. The study culminated in the discovery of a tri-peptide iodo-aryl amide that effected the desired bromolactonization in quantitative conversion with 24% ee. The experiments disclosed herein provided valuable insight that ultimately facilitated the development of more synthetically useful enantioselective halocyclization methodology.
- Whitehead, Daniel C.,Fhaner, Matthew,Borhan, Babak
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supporting information; experimental part
p. 2288 - 2291
(2011/05/16)
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- Carboxy pyridinium bromide perbromide reagents, part I: Selective oxidation of thiols and sulfides
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Efficient and convenient oxidation of aliphatic and aromatic thiols to disulfides and of sulfides to sulfoxides with pyridinium hydrobromide perbromide (PHBP), nicotinic acid hydrobromide perbromide (NAHBP), and 2,6-dicarboxy pyridinium hydrobromide perbromide (DCPHBP) in a solvent or under solvent free conditions and at ambient temperature is introduced. Copyright Taylor & Francis Group, LLC.
- Lakouraj, Moslem M.,Ghodrati, Keivan
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experimental part
p. 1432 - 1439
(2009/05/07)
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- An environmentally benign synthesis of organic ammonium tribromides (OATB) and bromination of selected organic substrates by tetrabutylammonium tribromide (TBATB)
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Stable crystalline organic ammonium tribromides (OATB), like Me4NBr3, Et4NBr3, Bu4NBr3, cetyltrimethylammonium tribromide, PyHBr3, can be readily synthesised from the reaction of the corresponding bromides with V2O5 and aqueous H2O2. Typically, TBATB, Bu4NBr3, brominates a variety of organic substrates rather easily under mild conditions. An activated aromatic ring is selectively brominated in the presence of an olefinic double bond.
- Chaudhuri, Mihir K.,Khan, Abu T.,Patel, Bhisma K.,Dey, Deepa,Kharmawophlang, Wancydora,Lakshmiprabha,Mandal, Gagan C.
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p. 8163 - 8166
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Formic and Oxalic Acids by Pyridinium hydrobromide perbromide
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The oxidation of formic and oxalic acids by pyridinium hydrobromide perbromide (PHPB) leads to the formation of carbon dioxide.The reaction is first order with respect to PHPB.The rate of reaction increases with an increase in the concentration of acids but the order is less than one.The values of the formation constants for the organic acid-PHPB complexes and the rates of their decomposition, at different temperatures, have been calculated.Oxidation of α-deuterioformic acid indicated the presence of a primary kinetic isotope effect.With an increase in the amount of acetic acid in the solvent mixture of acetic acid and water, the rate increased.Suitable mechanisms involving the formation of acyclic and cyclic intermediates in the oxidations of formic and oxalic acids respectively have been proposed.
- Suri, Deeps,Kothari, Seemn,Banerji, Kalyan K.
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p. 1301 - 1317
(2007/10/03)
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- Correlation Analysis of Reactivity in the Oxidation of Substituted Benzyl Alcohols by Pyridinium Hydrobromide Perbromide
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Oxidation of monosubstituted benzyl alcohols by pyridinium hydrobromide perbromide (PHPB) leads to the formation of the corresponding benzaldehydes.The reaction is first order with respect to PHPB.Michaelis-Menten-type kinetics were observed with respect to he alcohol.The oxidation of α,α-dideuteriobenzyl alcohol indicated the presence of a substantial kinetic isotope effect.The rates of oxidation of meta- and para-substituted benzyl alcohols were correlated in terms of Taft's and Swain's dual substituent-parameter equations.The rates of the meta compounds correlated best with Taft's ?1 and ?0R values whereas the para-compounds showed an excellent correlation with Taft's ?1 and ?R + constants.The rates of the otho-substituted alcohols showed very good correlation with Charton's triparametric equation.The rate increased with an increase in the polarity of the solvent.A mechanism involving a rapid reversible formation of an intermediate complex and its subsequent decomposition in the rate-determining step has been proposed.
- Suri, Deepa,Banerji, Kalyan K.,Kothari, Seema
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p. 1734 - 1758
(2007/10/03)
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- KINETICS AND MECHANISM OF OXIDATION OF (ARYLTHIO)ACETIC ACIDS BY PYRIDINIUM HYDROBROMIDE PERBROMIDE
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Oxidation of several monosubstituted (phenylthio)acetic acids (PTAA) by pyridinium hydrobromide perbromide (PHPB) was studied in aqueous acetic acid.The reaction is first order with respect to PHPB.Michaelis-Menten type kinetics are observed with respect to (arylthio)acetic acid.The effect of solvent composition indicates that the transition state is more polar than the reactants.The formation constants of the intermediate substrate-PHPB complexes and the rates of their decomposition were determined at different temperatures.The rates of oxidation of para and meta-substituted (phenylthio)acetic acids were correlated with Hammett's substituent constants.The ρ value is -1.60 at 35 deg c.The rates of oxidation of ortho substituted compounds are correlated with Charton's triparametric equation.A mechanism involving the decomposition of the intermediate complex in the slow rate-determining step affording a sulphonium ion which hydrolyses in a subsequent fast step to the sulphoxide is proposed.
- Karunakaran, K.,Elango, K. P.
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p. 429 - 434
(2007/10/02)
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- Process and intermediates
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A novel process for the preparation of isomers or mixtures of isomers of compounds of the formula STR1 and novel intermediates therefore.
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- Kinetics and Mechanism of Oxidation of Aliphatic Aldehydes by Pyridinium Hydrobromide Perbromide
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Oxidation of six aliphatic aldehydes by pyridinium hydrobromide perbromide (PHPB) in aqueous acetic acid leads to the formation of the corresponding carboxylic acids.The reaction is first order with respect to PHPB.Michaelis-Menten type kinetics were observed with respect to the aldehyde.The formation constants for the aldehyde-PHPB complexes and the rate of their decomposition, at different temperatures, were evaluated.The oxidation of MeCDO exhibited a substantial kinetic isotope effect.The effect of solvent composition indicated that the transition state is morepolar than the reactants.The role of aldehyde in the oxidation process is discussed.A mechanism involving transfer of a hydride ion from the aldehyde hydrate to the oxidant is proposed.
- Devi, Jai,Kothari, Seema,Banerji, Kalyan K.
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p. 2680 - 2694
(2007/10/02)
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