- Oxidant/complexing properties of the methimazole (MeImHS)/iodine system towards palladium and gold metals. Crystal structure of the complex cation [PdII(MeImHS)4]2+ balanced by a tetraiodide/iodide mixture
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This paper reports on the oxidative dissolution ability in dichloromethane and water of the methimazole-iodine system towards gold and palladium in powder. This research has a potential application in the recovery process of these metals from electrical and electronic waste equipment (WEEE). The iodine-adduct of methimazole (1-methyl-3H-imidazole-2-thione; MeImHS) oxidises gold and palladium powders in dichloromethane to form the complexes [AuI(MeImHS)2]I3 and [PdII(MeImHS)4](I4)0.73·2(I)0.27. The X-ray crystal structure of the palladium complex shows a square-planar Pd(ii) ion S-coordinated to four MeImHS units with the charge essentially balanced by an unusual tetraiodide I42- with minor amounts of iodide. The oxidative dissolution of palladium in water medium produces the cation [PdII(MeImHS)4]2+. Considering the reaction conditions under which the process was performed ([I2] = 1.14 × 10-3 M, T = 20 °C, pH = 5, reaction time 24 h), the obtained value of 64% of oxidation yields from Pd(0) to Pd(ii) is to be considered satisfactory. No appreciable oxidation was observed for the gold powder in water. The feasibility of recovering palladium from the triiodide salt of the complex cation [PdII(MeImHS)4]2+ was verified by carrying out a two-step reduction process using magnesium powder.
- Isaia, Francesco,Aragoni, Maria Carla,Arca, Massimiliano,Caltagirone, Claudia,Castellano, Carlo,Demartin, Francesco,Garau, Alessandra,Lippolis, Vito,Pivetta, Tiziana
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- Methimazole synthesizing and purifying method
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The invention discloses a methimazole synthesizing and purifying method, and belongs to the field of medicine synthesis. The method comprises the following steps: carrying out a condensation reaction on methylaminoacetaldehyde polyethylene glycol and ammonium thiocyanate which are used as raw materials in the presence of an acid catalyst and a phase transfer catalyst; and adding saturated salt water after the reaction is completed, uniformly mixing the obtained reaction product and the saturated salt water, adding an organic solvent to carry out extraction, drying and concentrating the obtained organic layer to obtain crude methimazole, heating and dissolving the crude product in a solvent, adding active carbon to decolorize the obtained solution, filtering the solution, and drying the filtered solution to obtain purified methimazole. The method is a preparation method simple to operate and suitable for industrial production.
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Paragraph 0005; 0021; 0024; 0026-0028
(2017/10/07)
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- Methimazole preparation process
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The invention provides a methimazole preparation process including the following steps: 1) with 1-methyl-1,3-2H-imidazole-2-one as a raw material and with cooperation of a reaction solvent, vulcanizing the raw material through a vulcanization reagent to obtain a methimazole crude product; and 2) recrystallizing the crude product obtained in the step 1) to obtain the finished product. With 1-methyl-1,3-2H-imidazole-2-one as the raw material, the common vulcanization reagent is used for vulcanization, and methimazole with light color, high purity and low content of metal ions is obtained; and the whole preparation process is simple, has the advantages of easy operation and lower cost, and is suitable for industrial promotion and application.
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Paragraph 0019; 0020
(2016/11/17)
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- Synthesis and crystal structures of new 1,3-disubstituted imidazoline-2-thiones
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Two methods (MeOH=K2CO3, pyridine=Et3N) were assessed for the introduction of sulfur into the 2-position of 1,3-disubstituted quaternary imidazolium salts 1-9 (Cl, I, BF4, PF6, CH3OSO3 were used as anions) to yield nine 1,3-disubstituted imidazoline-2-thiones 10-18 (1, 10: R1 = CH 3, R2 = CH3; 2, 11: R1 = OCH 2Ph, R2 = CH3; 3, 12: R1 = OCH 3, R2 = CH3; 4, 13: R1 = OCH 3, R2 = OCH3; 5, 14: R1 = NH 2, R2 = CH2Ph; 6, 15: R1 = NCHPh, R2 = CH3; 7, 16: R1 = NH2, R 2 = CH3; 8, 17: R1 = NCHPh, R2 = NCHPh; 9, 18: R1 = NH2, R2 = OCH3). Compounds 11-18 represent N-alkyloxy and N-amino imidazoline-2-thiones, whereas 10 served as reference compound. The first method was advantageous for the conversion 1 → 10 due to faster reaction, whereas in the reaction 2 → 11 considerable amounts of by-products were formed. Pure thiones 11, 14, 16, 17, and 18 were obtained only by the second method. Both methods worked for the synthesis of the methoxy derivatives 12 and 13 from 3 and 4, and the benzylideneamino derivative 15 from 6. 1-Amino-3- methylimidazoline-2-thione (16) was also prepared by hydrolysis of the benzylideneamino derivative 15. Crystal structures of seven 1,3-disubstituted imidazoline-2-thiones were determined by singlecrystal X-ray diffraction. Intermolecular C-H...S contacts were identified and, additionally, N-H...S interactions in aminothiones 14 and 16. The 1H NMR shifts of 10 and 13 were satisfactorily correlated with the Kamlet-Abboud-Taft π* and β parameters in ten solvents. From the lack of correlation with the a parameter and from the C=S bond length (average 1.68 A ) a significant contribution of a mesoionic imidazolium-2-thiolate resonance structure seems unlikely.
- Laus, Gerhard,Kahlenberg, Volker,Wurst, Klaus,Mueller, Thomas,Kopacka, Holger,Schottenberger, Herwig
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p. 1239 - 1252
(2013/12/04)
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- Antithyroid drugs and their analogues protect against peroxynitritemediated protein tyrosine nitration-a mechanistic study
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In this paper, the effect of some commonly used antithyroid drugs and their analogues on peroxynitritemediated nitration of proteins is described. The nitration of tyrosine residues in bovine serum albumin (BSA) and cytochrome c was studied by Western blot analysis. These studies reveal that the antithyroid drugs methimazole (MMI), 6-n-propyl-2-thiouracil (PTU), and 6-methyl-2- thiouracil (MTU), which contain thione moieties, significantly reduce the tyrosine nitration of both BSA and cytochrome c. While MMI exhibits good peroxynitrite (PN) scavenging activity, the thiouracil com-pounds PTU and MTU are slightly less effective than MMI. The S- and Semethylated compounds show a weak inhibitory effect in the nitration of tyrosine, indicating that the presence of a thione or selone moiety is important for an efficient inhibition. Similarly, the replacement of N-H moiety in MMI by N-methyl or N-m-methoxybenzyl substituents dramatically reduces the antioxidant activity of the parent com-pound. Theoretical studies indicate that the substitution of N-H moiety by NMe significantly increases the energy required for the oxidation of sulfur center by PN. However, such substitution in the selenium analogue of MMI increases the activity of parent compound. This is due to the facile oxidation of the selone moiety to the corresponding selenenic and seleninic acids. Unlike N,N'-disubstituted thiones, the corresponding selones efficiently scavenge PN, as they predominantly exist in their zwitterionic forms in which the selenium atom carries a large negative charge.
- Bhabak, Krishna P.,Mugesh, Govindasamy
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experimental part
p. 1175 - 1185
(2010/06/19)
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- Energy transfer, electron transfer, and addition reactions of triplet state of 1,3-dihydroimidazole-2-thiones investigated by laser flash photolysis
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The transient absorption bands observed at ca. 400 and 550 nm for 1,3- dihydro-2H-imidazole-2-thione (IT), 1,3-dihydro-1-methyl-2H-imidazole-2- thione (MIT), and 1,3-dihydro-2H-benzimidazole-2-thione (BIT) have been assigned to their triplet states (3IT* 's) by the quenching and sensitizing experiments using laser flash photolysis technique. Short intrinsic triplet lifetimes and relatively high triplet energies have been evaluated as characteristics of 3IT* 's. For electron acceptors, photoinduced electron- transfer reaction occurs via 3IT* 's in the diffusion controlled limit. The nucleophilic character of 3IT* 's was confirmed by changing the substituents of alkenes on the addition reactions. MO calculations indicate that the lowest electronic configurations of both 3IT* and 3MIT* have 3(n,π*) character, while 3BIT* has 3(π,π*) character. The addition reactivity of 3BIT* is slightly higher than those of 3IT* and 3MIT*, which is opposite to the general tendency.
- Alam, Maksudul M.,Ito, Osamu
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p. 339 - 345
(2007/10/03)
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- 2-[(2-Aminobenzyl)sulfinyl]-1-(2-pyridyl)-1,4,5,6- tetrahydrocyclopent[d]imidazoles as a novel class of gastric H+/K+-ATPase inhibitors
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Substituted 2-sulfinylimidazoles were synthesized and investigated as potential inhibitors of gastric H+/K+-ATPase. The 4,5-unsubstituted imidazole series 6-11 and the 1,4,5,6-tetrahydrocyclopent[d]imidazole series 12 were found to be potent inhibitors of the acid secretory enzyme H+/K+- ATPase. Structure-activity relationships indicate that the substitution of 2- pyridyl groups at the 1-position of the imidazole moiety combined with (2- aminobenzyl)sulfinyl groups at the 2-position leads to highly active compounds with a favorable chemical stability. Other substitution patterns in the imidazole moiety result in reducing biological activities. 2-[(2- Aminobenzyl)sulfinyl]-1-[2-(3-methylpyridyl)]-1,4,5,6- tetrahydrocyclopent[d]imidazole (12h, T-776) was selected for further development as a potential clinical candidate. Extensive study on the acid degradation of 12h indicates a mechanism of action different from that of omeprazole, the first H+/K+-ATPase inhibitor introduced to the market.
- Yamada,Yura,Morimoto,Harada,Yamada,Honma,Kinoshita,Sugiura
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p. 596 - 604
(2007/10/03)
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- Equilibrium Studies on the Cleavage of Disulfide Bond in 2,2'-Dithio-Diimidazoles with Iodide Ion in Aqueous Solutions
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The equilibrium of the reaction between 2,2'-dithio-diimidazoles and iodide ion in acidic aqueous solutions was studied spectrophotometrically.Cleavage of -S-S- bond and formation of imidazole-2-thiones and iodine, as reaction products, was observed.Factor analysis and spectra's deconvolution were used for estimation of equilibrium system composition and for determination of equilibrium constants.Occurrence of an additional band (with maximum at 30.000 cm-1) in equilibrium spectra was ascribed to the formation of imidazolethione-I2-charge-transfer complex. Key words: charge transfer, complex compounds, equilibrium constants
- Suszka, A.
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p. 565 - 576
(2007/10/02)
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