1.3.4- oxadiazole-2-thiol

C8H6BrN04 4-nitrophenyl bromoacetate 19199-82-7 25.00 1.7429 2 12875 C8H6N20S 5-phenyl-1,3,4-oxadiazole-2-thiol 3004-42-0 25.00 1.3469 2... 

The 3-oxidotriazolopyridinium zwitterions 245 fail to react with DMAD unless magnesium bromide is present, when ring opening occurs (2000H(53 265) (Section IV.F). The thiol 268 adds methyl acrylate as expected the resulting ester is converted via the acid hydrazide, to an oxadiazole (89IJC(B)170). 

Sealants obtained by curing polysulfide liquid polymers with aryl bis(nitrile oxides) possess stmctural feature of thiohydroximic acid ester. These materials exhibit poor thermal stability when heated at 60°C they soften within days and liquefy in 3 weeks. Products obtained with excess nitrile oxide degrade faster than those produced with equimolar amounts of reagents. Spectroscopic studies demonstrate that, after an initial rapid addition between nitrile oxide and thiol, a second slower reaction occurs which consumes additional nitrile oxide. Thiohydroximic acid derivatives have been shown to react with nitrile oxides at ambient temperature to form 1,2,4-oxadiazole 4-oxides and alkyl thiol. In the case of a polysulfide sealant, the rupture of a C-S bond to form the thiol involves cleavage of the polymer backbone. Continuation of the process leads to degradation of the sealant. These observations have been supported by thermal analysis studies on the poly sulfide sealants and model polymers (511). 

Published routes to pyrazino[2,3-3][l,4]thiazines, as reviewed in CHEC-II(1996) <1996CHEC-II(7)737>, involved the reaction of a 3-aminopyrazine-2-thiol with a biselectrophile and of a 3-chloropyrazin-2-amine with thioglycolate. In more recent work, the system is formed by condensation of a dichloropyrazine with a 2-aminothiophenol (Equation 182) <2002CPB922>. The same approach, using either 2-aminothiophenol or 2-aminoethanethiol, has been used to form oxadiazole-fused systems (Scheme 100) <1997CHE1352>. In studies toward the synthesis of ER-49890 151, benzannulated pyrazino[2,3-/ ][l,4]thiazines have also been accessed by an indirect sequence (Scheme 101)<2005H(65)403>. 

Y Watanabe, K Imai. Liquid chromatographic determination of amino and imino acids and thiols by postcolumn derivatization with 4-fluoro-7-nitrobenzo-2,l,3-oxadiazole. Anal Chem 55 1786— 1791, 1983. 

Keywords l,3,4-oxadiazole-2-thiol, l,3,4-thiadiazole-2-thiol, alumina, micro-wave irradiation, quinolone, sulfide... 

Aryl-l,3,4-tlriadiazole/oxadiazole-2-thiols 2 (0.01 mol) and 0.01 mol ethyl car-boxylate 1 were adsorbed separately on basic alumina. Both adsorbed materials were mixed intimately and irradiated in the microwave oven for 60-90 s. After completion of the reaction the mixture was cooled, and the product was extracted with 4x 10 mL CH2C12. Recovering the solvent under reduced pressure afforded the products 3 which were recrystallized from EtOH-CH2Cl2. 

Chloro-7-nitrobenz-2,l,3-oxadiazole (NBD-C1) reacts with primary and secondary aliphatic amines to produce intensely fluorescent derivatives. Although anilines, phenols and thiols react with NBD-C1, they produce derivatives which do not fluoresce or which are only weakly fluorescent. This limits the types of compounds which can be analyzed with this reagent and thus makes the technique more selective. This selectivity is desirable in trace analysis because of a lower degree of interference from co-extractives. The general reaction scheme for formation of the fluorescent amine derivatives is shown in Fig.4.50. 

Quinoline derivatives (60) have been synthesized by the reaction of 5-alkyl-l,3,4-thia-diazol/oxadiazol-2-thiols with 7-chloro-6-uoro-2,4-dimethylquinoline and by the reaction of 2-hydroxy-l,4-naphthoquinone with 2-chloro-3-formyl-4-methyl/ 6-methyl/7-methyl/8-methylquinolines, respectively, on basic alumina using micro-waves (Kidwai et al., 2000). 

Bifunctional systems form heterocyclic rings for example (194) yields (195). Photolysis of N-(triphenylmethyl)anilines results exclusively in C-N bond homolysis to give the trityl (< ) = 0.6-0.8) and anilino radicals." Reduction of the N-O bond cleaved intermediate (196) (formed on irradiation of 5-amino or 5-phenyl-1,2,4-oxadiazoles) by sodium hydrogen sulfide, thiols or thioamides yields the corresponding benzamidines (197). In contrast, in the presence of nucleophilic thioureas (199) or thiocarbamates (200), N-S bond formation occurs and subsequent elimination from the possible intermediate (201) yields the thiadia-zoles (198) or (202) respectively. ... 

Figure 5.3 CVs obtained for AT-methylphenazine (5 pM) in the absence (brown) and presence (green) of 400 pM xanthine at a Au electrode modified with 5-(4 -pyridinyl)-l,3,4-oxadiazole-2-thiol) and XDH (in 50 mM TYis buffer, pH 8) at a sweep rate of 5 mV s. Reprinted with permission from ref. 30. Copyright 2012 American Chemical Society.

Kalimuthu et al. reported an electrochemical study of EbDH where the enzyme was immobilized on a 5-(4 -pyridinyl)-l,3,4-oxadiazole-2-thiol modified gold electrode and trapped under a membrane. No direct electrochemistry of EbDH was observed, but in the presence of ferrocenium methanol as an effective artificial electron acceptor mediated electrocatalysis of EbDH was demonstrated with its native substrate ethylbenzene (Figure 5.32A) and also the related substrate p-ethylphenol (Figure 5.32B). The catalytic system was modelled by electrochemical simulation across a range of sweep rates and concentrations of substrate and mediator. 

Kidwai et al. have developed a convenient synthesis of 7-(5-alkyl-l,3,4-thiadia-zol/oxadiazol-2-ylthio)-6-flnoro-2, 4-dimethy Iquinolines (57) from 5-alkyl-l,3, 4-thiadiazol/oxadiazol-2-thiols (56) with 7-chloro-6-fluoro-2,4-dimethylquinohne (55) using basic alumina in MW (Scheme 6.21) [39, 60],... 

Kt = [(517)]/[(518)]. Walter and Schlichting have reported n.m.r. and i.r. spectral evidence for the occurrence of a betaine-thioacyl tautomerism in solutions of 1,1,4,4-tetrasubstituted thiosemicarbazides (519). Various physical investigations have shown that the thione form predominates for 1 -alkylthio-2-carbamoy 1-2-cy anoethy lene-1 -thiols, a 3 -unsaturated /3-aminodithio-esters, oxazole-2-thiones, l,3,4-oxadiazole-2-thione, ... 

An aspect that will increase in importance is the study of tautomerism of compounds adsorbed on metallic surfaces. Two recent examples are (i) tautomerization of 5-(4-pyridyl)-l,3,4-oxadiazole-2-thiol from thione to thiol when adsorbed on gold [49] and (ii) modification of the tautomers of azacytosines after adsorption on Au single crystal surfaces [50]. 

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