- Peroxo–tungstate(VI) complexes: syntheses, characterization, reactivity, and DFT studies
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Abstract: Three new oxodiperoxo–tungsten(VI) complexes containing benzene core carboxylic acids, viz., benzoic acid, 2-chlorobenzoic acid, and 3-aminobenzoic acid as co-ligands have been synthesized from reaction of Na2WO6H4, 30% H2O2 and the corresponding co-ligands in aqueous medium. The compounds have been comprehensively characterized by elemental analyses, FT-IR, 1H NMR, UV–Vis spectral studies as well as by mass spectrometric and TGA analyses. The infrared spectra suggest occurrence of terminally bonded W=O as well as triangular bidentate peroxo groups (C2v) and monodentate carboxylate group bound to the WO4+ center. The mass spectra of the compounds are in good agreement with proposed molecular formulations. Thermogravimetric analyses indicate the existence of both lattice and coordinated water molecules in the complexes. Density functional theory (DFT) calculations were used to compute the frequencies of relevant vibrational modes, electronic properties and also to investigate structure of the compounds. Compound potassium(aquo)(2-chlorobenzoato)oxodiperoxo–tungstate(VI)dihydrate acts as an oxidant for bromide ion in aqueous phase bromination of chosen organic substrates to their corresponding bromo-organics. Graphical abstract: [Figure not available: see fulltext.]
- Das, Nandita,Chowdhury, Shubhamoy,Purkayastha, Ranendra N. Dutta
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p. 1255 - 1266
(2019/07/04)
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- Fast halogenation of some N-heterocycles by means of N,N'-dihalo-5,5- dimethylhydantoin
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An instantaneous, selective and high-yielding halogenation process is reported. The method operates with imidazoles, pyrazoles, and indoles under benign reaction conditions. The developed process involves the use of N,N'-dihalo-5,5-dimethylhydantoins (halo=chlorine, bromine, iodine) as halogenation reagents that are activated by catalytic quantities of a strong Bronsted acid. Moreover, the halogenation process is switchable to produce either the mono- or di-halogenated products. Issues related to the reaction mechanism are investigated and a proposal for a reaction mechanism is disclosed.
- Sandtorv, Alexander H.,Bjorsvik, Hans-Rene
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p. 499 - 507
(2013/05/08)
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- Synthesis and Reactions of Brominated 2-Nitroimidazoles
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Various approaches to the synthesis of the hitherto-unknown 4(5)-bromo-2-nitroimidazole (5) are reported.Direct bromination of 2-nitroimidazole with N-bromosuccinimide gave the unreported 4,5-dibromo-2-nitroimidazole (10) in quantitative yield, but this could be selectively debrominated to give compound (5).While 1-methyl-2-nitroimidazole readily gave 4-bromo-1-methyl-2-nitroimidazole (15) on bromination, this could not be demethylated to give (5), and bromination of various other N-protected 2-nitroimidazoles was also unsuccessful.Lithiation of 4-bromo-1-tritylimidazole (21) followed by quenching with propyl nitrate gave (after detritylation and methylation) a mixture of a dimer (28) and compound (15), indicating that the desired product (5) is produced in this reaction although it can only be isolated in derivatized form.The proposed route for formation of the dimer suggests a general reaction between 1-alkyl-4-bromo-2-nitroimidazoles and strong C- and N-nucleophiles, resulting in substitution at the 5-position.
- Palmer, Brian D.,Denny, William A.
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