5-Nitrothiazole reduction

Reduction of 2.4-dimethyl-5-nitrothiazole with activated iron gives a product that after acetylation yields 25% 2.4-dimethyl-5-acetamido-thiazole (58). The reduction of 2-methyl 5-nitrothiazole is also reported (351 to give a mixture of products. The nitro group of 2-acetylhydrazino-5-nitrothiazole is reduced by TiCl in hydrochloric acid or by Zn in acetic acid (591. 

Anion-radicals derived from the reduction of nitrothiazoles were studied by Tordo et al. (285). The reaction scheme is the following ... 

Nitrothiazole is obtained by reductive dehaiogenation of 2-bromo-5-nitrothiazole (2, 14, 83). 

The 2-nitrothiazole can be reduced to the corresponding aminothiazole by catalytic or chemical reduction (82, 85, 89). The 5-nitrothiazole can also be reduced with low yield to impure 5-aminothiazole (1, 85). All electrophilic substitution reactions are largely inhibited by the presence of the nitro substituent. Nevertheless, the nitration of 2-nitrothiazoIe to 2,4-dinitrothiazole can be accomplished (see Section IV). 

Nitrothiazoles are reduced to 2-aminothiazoles, either catalytically or chemically, whereas the reduction of 5-nitrothiazole gives poor yields of impure 5-aminothiazole. 2-Nitrobenzothiazole is reduced to the azo derivative by tin(II) chloride in basic medium (Scheme 126). 

The spin density on nitro group in nitrothiazole RA, obtained by reduction with the help of glucose and strong basis, decreases in the following sequence [879] (Scheme 3.24) ... 

Polarography investigations of nitrothiazoles are carried out in some works [535,929,931,983,984], The investigation of fourteen 2-R-5-nitrothiazoles it is shown that the compounds of greater toxicity have higher negative reduction potential values [535], The polarographic characteristics of 2-acetamido-5-nitrothiazole [931, 983] and niridazole (ambilhar) [929] have been obtained. 

High-performance liquid chromatography (HPLC) has been used to analyze metronidazole [1435-1437], misonidazole [1309,1438], and other nitroimidazoles [1435, 1439] in body fluids or pharmaceutical dosage forms. HPLC analysis of effect of hypoxic-cell radiosensitizer misonidazole on the radiation-induced reduction of DNA bases (thymine, cytosine, and adenine) has been carried out [1440, 1441], HPLC was employed to characterize different nitroimidazoles [327, 366, 388,409, 450, 1442-1444], nitropyrazoles [246, 301], nitrothiazoles [366], l-aryl(hetaryl)-4-nitro-l,2,3-triazoles [601], nitrobenzimidazoles [707], nitrobenzofurazans [774, 1445-1449], nitrobenzotriazoles [1450],... 

Partition coefficients in the octanol-pH 7.4-phosphate-buffer system. c Nitrothiazole oxidation-reduction potentials (volts) as calculated from their half-wave potentials, as determined using a Polarecord E 261 polarograph (Metrohm AG, Herisau, Switzerland) and a saturated Ag/AgCl reference electrode. Measurements were performed at 20°C and a drop time of 1 drop/2.8 sec. The compounds were dissolved in 1 ml dimethyl formamide and added to 24 ml of a borax-potassium biphosphate buffer of pH 7.3 [prepared according to J. M. Kolthoff, J. Biol. Chem. (1925) 68, 135]. A pH of 7.4 resulted. Standard error of determination 3 mv. 

Only the 2.4-dinitrothiazole is known, being prepared by nitration of 2-nitrothiazole by N2O4-NO2/BF3. The yield is 80% (90). The reduction with Raney Ni/AcjO of 2,4-dinitrothiazole proceeded smoothly, yielding the corresponding 2,4-diacetamidothiazole. 

Nitro-5-halogenothiazoles, 57 8 preparation of, 578 reaction with MeO", 580 2-(4-Nitrophenylimino)-4-thiazolidone, from 4-nitrophenylthiourea and chloroacetic acid, 296 2-Nitrothiazole, 576 nitration of, 577 preparation of, 576 reaction with KF, 566 reaction with MeO", 577 reduction of, 577... 

Nitrothiazole, 576 preparation of, 577 reduction of, 577 ring opening reaction, 577 Nitrothiazoles, chemical shift, proton, 68 coupling constants in EPR, 84 ionization potential, 5 2 reduction of, 381 ultraviolet absorption, 48 Nuclear magnetic resonance, 66 of alkyl thiazoles, 342 of aryl thiazoles, 342 correlation with theoretical calculations, 70... 

Various thiazole anion-radicals have been characterized by ESR. Tordo and co-workers have generated several nitrothiazole anion radicals (e.g., 204 and 205) by reduction of the precursors with glucose in methanol containing... 

Pedulli and co-workers have also studied anion-radicals in the thiazole system, including those from 2-nitrothiazole, 2,2 -bithiazolyl, 2-arylthiazoles, and bis(2-thiazolyl) ketone. Here the anion-radicals were generated by alkali-metal reduction in ethereal solvents and found to exist in contact ion-pairs. Whenever the organic component contained two adjacent binding sites, chelation of the counterion occurred and was revealed by examining the variation of its hyperfine splitting with temperature and solvent. The interaction of the ion-pairs with macrocyclic polyethers was also studied by ESR for certain of the chelating radicals. ... 

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