- Novel spectrophotometric methods for the determination of fluconazole in the presence of its oxidative degradation product
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Five sensitive, selective and precise spectrophotometric stability-indicating methods for the determination of fluconazole in the presence of its oxidative degradation product and in pharmaceutical formulations are developed and validated. Method A is a newly developed spectrophotometric one that is called ratio difference method by measuring the difference in amplitudes between 261.5 and 266.5 nm of ratio spectrum. Method B is a third derivative spectrophotometric one, which determines peak amplitudes from 265.5-268nm (peak-peak). Method C is ratio subtraction method. Method D is the first derivative of the ratio spectra by measuring the peak amplitude at 269 nm. Finally, method E is the mean centering of ratio spectra method by measuring the peak amplitude at 266.5 nm. The proposed methods allow the determination of fluconazole in the presence of its oxidative degradation product over a concentration range of 50-400 μg.mL-1 with mean percentage recoveries of 100.24±0.91, 99.91±0.52, 100.20±1.26, 99.79±0.69, and 100.77±0.72 respectively. The selectivity of the proposed methods is checked using laboratory prepared mixtures. The proposed methods have been successfully applied to the analysis of fluconazole in pharmaceutical dosage forms without interference from other dosage form additives and the results have been statistically compared with a reported method.
- Lotfy, Hayam Mahmoud,Monir, Hany Hunter,Abd El-Aleem, Abd El-Aziz El-Bayoumi
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p. 1447 - 1455
(2013/07/19)
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- Dipalladium complexes with triazolidin-diylidene bridges and their catalytic activities
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The 1,2,4-trimethyltriazolidin-3,5-diylidene (ditz) bridged dipalladium heterotetracarbene complex [PdBr2(iPr2-bimy)] 2(μ-ditz) (3) (iPr2-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene) was prepared by Ag-carbene transfer involving the 1,2,4-trimethyltriazolium dication (C), Ag2O, and the precursor complex (iPr2-bimyH)[PdBr3( iPr2-bimy)] (2). Bromido substitution of 3 with AgO 2CCH3 and AgO2CCF3afforded the carboxylato complexes [Pd(O2CCH3)2( iPr2-bimy)]2(μ-ditz) (4) and [Pd(O 2CCF3)2(iPr2-bimy)] 2(μ-ditz) (5). Multinuclei NMR spectroscopies and X-ray diffraction analyses showed that the all-trans isomers of 3, 4, and 5 are the predominant products in all three cases. In addition, the decomposition product of complex 4, trans-[Pd(O2CCH3)2( iPr2-bimy)2] (trans-6) was structurally determined by X-ray crystallography. A comparative catalytic study revealed the superiority of complexes 3, 4, and 5 over the previously reported mononuclear bis(benzimidazolin-2-ylidine) complexes without ditz bridges in the Mizoroki-Heck coupling reaction. Overall, complex 4 bearing acetato coligands showed the best catalytic performance.
- Guo, Shuai,Huynh, Han Vinh
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experimental part
p. 4565 - 4573
(2012/07/27)
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- An investigation into the alkylation of 1,2,4-triazole
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The alkylation of 1,2,4-triazole with 4-nitrobenzyl halides and a variety of bases afforded the 1- and 4-alkylated isomers with a consistent regioselectivity of 90:10. Previously reported regiospecific alkylations of 1,2,4-triazole were re-examined and the quoted isomer ratios were shown to depend on the isolation procedure. The use of DBU as base in the alkylation of 1,2,4-triazole allows for a convenient and high yielding synthesis of 1- substituted-1,2,4-triazoles. (C) 2000 Elsevier Science Ltd.
- Bulger, Paul G.,Cottrell, Ian F.,Cowden, Cameron J.,Davies, Antony J.,Dolling, Ulf-H.
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p. 1297 - 1301
(2007/10/03)
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- Oxidative Alkylation of Azoles. III. Reaction of N-Chloro-1,2,4-triazole with Methyl Iodide
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Reaction of 1-chloro-1,2,4-triazole with methyl iodide in methylene chloride or chloroform at 20-40 deg C results in formation of products of mono- and dialkylation of the ring at positions 1 and 4.Under the same conditions, the 1,4-dimethyltriazolium salt gives rise to 5-iodo derivative.
- Kurenkov, A. A.,Pevzner, M. S.
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p. 1118 - 1121
(2007/10/03)
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- Photochemistry of N-(Benzoylimino)-1,2,4-triazolium and N-(Benzoylimino)pyridinium Ylides: A Source of Benzoylnitrene Useful in Photolabeling and Photo-Cross-Linking Experiments
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The photochemistry of substituted 1-(benzoylimino)pyridinium and 4-(N-benzoylimino)-1,2,4-triazolium ylides was investigated to judge their capacity to give aroylnitrenes and their suitability for use in photolabeling experiments.Evidence presented indicates that the triplet states of the ylides cleave to generate aroylnitrenes.In an attempt to enhance triplet formation, nitro- and acetyl-substituted pyridinium ylides were examined.Their irradiation does not give nitrenes in meaningful yield.However, irradiation of the triazolium ylides gives nitrenes in excellent yield.The mechanism of these reactions was probed, and additional evidence is obtained that supports the proposal that benzoylnitrene is a singlet in its ground state.The triazolium ylides may be suitable reagents for photolabeling applications.
- Arnold, Charles R.,Melvin, Tracy,Nelson, William M.,Schuster, Gary B.
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p. 3316 - 3319
(2007/10/02)
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- Alkylation, Acylation and Silylation of Azoles
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Performing alkylation, acylation and silylation reactions in separate deprotonation and nucleophilic displacement steps allows for better control of reaction conditions and facilitates problem handling in these processes.In the alkylation of azoles the alkylating agents and solvents possess individual reaction capabilities which seem to be approximately additive.Monoalkylation occurs if the sum of the normalized reaction potentials is equal or larger than the pKa value of the azole.Dialkylation is avoided by keeping the sum of the normalized reaction potentials below the pKa value of the alkylazole.The applicability of these principles is demonstrated by the development of effective procedures for the methylation, benzylation, acetylation, methoxycarbonylation and trimethylsilylation of azoles.
- Begtrup, Mikael,Larsen, Peter
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p. 1050 - 1057
(2007/10/02)
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- INTRODUCTION OF SUBSTITUENTS INTO 5-MEMBERED AZA-HETEROAROMATICS
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With emphasis on mono- and regio-selectively, methods for introduction of substituents at nitrogen and carbon atoms of 5-membered aza-heteroaromatics have been developed.The methods involve application of activation and of assistant groups for direction and protection.Activation has been achieved by the use of quaternary azolium ions and azol-N-oxides as reactive intermediates.If necessary, the N-oxides were further activated by alkylation or acylation.
- Begtrup, Mikael
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p. 573 - 598
(2007/10/02)
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- Nucleophilic Substitution in Quaternary Salts of NN'-Linked Biazoles and Related Systems.
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Some reactions of dicationic and monocationic N,N'-linked biazoles and of quaternized 1-(N-azolyl)pyridinium ions with nucleophiles have been studied.Although the pyrrolyl nucleus has been found to be a poor leaving group in these reactions, in other cases nucleophilic attack readily takes place at an azolyl carbon atom, with subsequent elimination of the N-substituent.The 1-methyl-3-(1-methyl-1,2,4-triazol-4-ylio)benzimidazolium dication (1) reacted at room temperature with ammonium, diethylamine, methoxyde, hydroxide, and cyanide ions, and with sodium borohydride, giving in all cases the corresponding 2-substituted benzimidazoles in good yield.In the case of the 2,4,6-trimethyl-1-(2-methylpyrazol-1-io)pyridinium dication (6), the reaction with cyanide ion afforded, regioselectively, 5-cyano-1-methylpyrazole, with no trace of the isomeric 3-cyano-1-methylpyrazole.The synthesis of the cations and dications from N-aminoazoles was easily performed.The reaction of 1-aminobenzimidazole with dehydroacetic acid in aqueous hydrochloric acid gave not only the expected 1-benzimidazol-1-yl-2,6-dimethylpyridin-4(1H)-one (9), but also 3-acetyl-1-benzimidazol-1-yl-4-hydroxy-6-methylpyridin-2(1H)-one (11).In pyridine, a pyran-2,4-dione intermediate (10), isomeric to (11), was also isolated.The quaternization reactions were easily performed, but high temperatures caused cleavage of the N-N bond.
- Castellanos, Maria Luisa,Llinas, Montserrat,Bruix, Marta,Mendoza, Javier de,Martin, M. Rosario
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p. 1209 - 1216
(2007/10/02)
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