Thiols, derivatives

Thiol derivatives of 5,6-dihydro-l,3-4H-oxazine (e.g., 39) are formed by reacting carbon disulfide with 3-aminopropanols. ° ... 

Treatment of quinoline 2-thiol derivative 660 with 2,3-dibromopropanol gave the thiazoloquinoline 661 which upon treatment with K2CO3 gave a mixture of 662 and the rearrangement product 663. Separation, hydrolysis and reaction of 662 with A -methylpiperazine afforded 664 (93JMC3148)... 

In the case of 271a and 271b, covalently bound adducts of 271a, b and CO2 (e. g., carbamic acid derivatives) were detected. This was absent in the case of thiol derivative 271c. The concentration of this material could be reduced by heating (a solution to 90 °C for 1 h) and increased by exposing to a CO2 atmosphere. 

In 1994, thiols were firstly used as stabilizers of gold nanoparticles [6a]. Thiols form monolayer on gold surface [18] and highly stable nanoparticles could be obtained. Purification of nanoparticles can be carried out, which makes chemical method of metal nanoparticles a real process for nanomaterial preparation. Various thiol derivatives have been used to functionalize metal nanoparticles [6b, 19]. Cationic and anionic thiol compounds were used to obtain hydrosols of metal nanoparticles. Quaternary ammonium-thiol compounds make the nanoparticle surface highly positively charged [20]. In such cases, cationic nanoparticles were densely adsorbed onto oppositely charged surfaces. DNA or other biomolecule-attached gold nanoparticles have been proposed for biosensors [21]. 

Thiols are also important protection against lipid peroxidation. Glutathione (7-Glu-Cys-Gly) is used by several glutathione-dependent enzymes such as free-radical reductase (converts vitamin E radical to vitamin E), glutathione peroxidase (reduces hydrogen peroxide and lipid hydroperoxides to water and to the lipid alcohol, respectively), and others. In addition, the thiol group of many proteins is essential for function. Oxidation of the thiol of calcium ATPases impairs function and leads to increased intracellular calcium. Thiol derivatives such as the ovothiols (l-methyl-4-mercaptohistidines) (Shapiro, 1991) have been explored as therapeutics. 

In the same context, Kang et al. have examined several bidentate thiol derivatives as ligands in the same reaction to that described above. A nickel complex derived from the p-amino thiol depicted in Scheme 2.31 catalysed the reaction in a useful asymmetric level of 74% ee, whereas the use of the thiol phosphine ligand depicted in Scheme 2.31 gave a lower enantioselectivity of 27% ee. In this study, the authors found that the enantioselectivity was strongly dependent on the ligand concentration and on the nickel-to-ligand ratio. 

Chemical stabilizers have been used to reduce the rate of oxygen-promoted degradation of polysaccharides at T>225°F. Methanol and sodium thiosulfate are the most commonly used (86). Sodium dithio-carbamate, alkanolamines, and thiol derivatives of imidazolines, thiazolines, and other heterocyclic compounds have also been tested for this application. Calcined dolomite (B7) and Cu(l) and Cu(ll) salts (88) have been reported to increase the thermal stability of HEC. 

Figure 3 Fragmentation for trihalomethylsulfeny 5-methyl-1,3,4-thiadiazole-2-thiol derivatives <2003JP01 >.

When thioxo (or thiol) derivatives (as part of a thiourea function incorporated into the heterocyclic system) are present, effective. Y-alkylation is observed. Thus, the 3-heteroaryl-substituted [l,2,4]triazolo[3,4-/)][l,3,4]thiadiazole-6(5//)-thiones 37 dissolved in sodium hydroxide solution react with alkyl halides to afford the corresponding 6-alkylthio derivatives 38 (Equation 4) <1992IJB167>. The mesoionic compounds 39, inner salts of anhydro-7-aryl-l-methyl-3-methylthio-6-sulfonyl-[l,2,4]triazolo[4,3-A [l,2,4]triazolium hydroxides, are methylated with methyl iodide to give the corresponding quaternary salts 40 (Equation 5) <1984TL5427, 1986T2121>. 

The hydrolysis product 51 can alternatively be accessed directly from the reaction of the thiol derivative 48 with chloro acetamide. Other electrophiles for the reaction with the thiol derivative were also described which lead to functionalized tetrazole or 5-6 fused bicyclic ring systems. 

When the thiole derivatives are converted into the corresponding sulfenyl chloride such as 56, an addition reaction to styrene or /3-methylstyrene in nitromethane gives regioisomeric mixtures of adducts 57 and 58 (Scheme 11) <2001CHE702> as well as the cyclization products 59 which are generated in 47% (R = H) and 52% (R = OI I () yield, respectively. 

Trifluoroethyl chloride, bromide, and iodide (but not fluoride) react with thio-late ions in DMF under laboratory illumination at 30-50 °C to give high yields of 2,2,2-trifluoroethyl thiol derivatives. Various features of the reactions show that they occur by the 5 rnI mechanism. The initiation may be spontaneous or thermal electron transfer between thiolate and halides, because the reactions can occur in the dark. 

Several variations of this synthetic route have been developed. For example, condensation of the methyltriazole (21) with thiourea gives the thiol derivative (22), and reaction with phosphoryl chloride in dimethylformamide converts the amino-amide to a cyano-amidine, which can be reduced to the 4-amino-5-aminomethyl derivative (Scheme 47). ... 

Triazole melts at 120-121 °C and boils at 260 °C. It has a density of 1.132 and a specific conductivity of about 10 0 cm , of the same order as imidazole. Triazole dissolves readily in water and ethanol but is only slightly soluble in ether. Substitution on N(l) usually lowers the melting point this effect is usually much smaller for substitution at N(4), although 4-aminotriazole has a melting point of 84-86°C. 3-Aminotriazole has a melting point of 159°C and the 3-thiol derivative of 221-... 

Brand Name(s) Cuprimine, Depen Chemical Class Thiol derivative... 

Additional polythiocarbonate poly thiol derivatives of the current invention were prepared by the authors (1) and are described. 

The next milestone came with the description of the condensation reactions between 1,3- dicarbonyl compounds and alcohols, amines or thiol derivatives. This reaction was a great success in the search for simplicity as an efficient tool for green chemical processes, thanks to the reduction of the number of synthetic steps and... 

Following preparation of the protected thiol derivative 29 (overall retention of configuration is observed when using Val), a mixed anhydride was prepared and converted into the amide 30 with ammonia. The acetyl group of 30 was then removed and the resulting thiol compound condensed with Z-Arg-OH to give the thioester dipeptide 31. 

A second important class of complexes contains both thiolate and tertiary phosphine ligands. These are prepared by reactions such as those of equations (28) or (29).187,228,233-236 Bridged complexes (9) and (10) may be prepared either from dithiols or from tertiary phosphine thiol derivatives, respectively.187,237 The structure of the large ring complex (10) has been determined.238... 

Analogous observations have been made in the phosphate series. Thus, the Monophosphate I is not an effective inhibitor of ChE s, unless it rearranges to a thiol derivative or becomes converted into the oxo derivative II (= paraoxon), a process taking place in vivo (22) ... 

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