Oxidative coupling of thiols

Catalysts of this type are also extraordinarily reactive for the oxidative coupling of thiols to disulfides, and the reaction is quantitative in a wide variety of organic solvents. In this case, the analogous first step would be... 

The oxidative coupling of thiols catalyzed by Fem-exchanged montmorillonite in phosphate buffer (pH 7.2) has also been demonstrated (Scheme 3.48) [151]. This system gives the corresponding disulfide as the sole product, which is in contrast to a previous report [152], where oxidation of thiols catalyzed by ion-exchanged clay gave the sulfide as the major product. 

Scheme 3.48 Oxidative coupling of thiols catalyzed by Felll-montmorillonite.

Figure 3.91 Oxidative coupling of thiols with amines.

Saxena, A., Kumar, A., and Mozumd, S. 2007. Ni-nanoparticles An efficient green catalyst for chemo-selective oxidative coupling of thiols. Journal of Molecular Catalysis A Chemical, 269 35 0. 

Tetrabutylammonium chlorochromate, (C4H9)4XCr03CI, is formed by adding a solution of chromium trioxide in concentrated hydrochloric acid to a solution of tetrabutylammonium hydrogen sulfate in 5 N hydrochloric acid at 0 °C. The dry compound is used in chloroform for the oxidation of alcohols to carbonyl compounds and the oxidative coupling of thiols to disulfides [619],... 

The selective aerobic (O2) oxidative coupling of thiols in several imidazolium-based ionic liquids is studied in the absence of any base/metal catalysts. Disulfides are obtained from the corresponding thiols in good to excellent yields in l-hexyl-3-methylimidazolium bromide ([hmim]Br). Furthermore, a H NMR-based mechanistic study of the S-S bond formation demonstrated the cooperative role of halide anion and imidazolium cation of [hmimJBr. ... 

The synthesis of polysulfide elastomers involves the use of a small amount of trichloroalkane in addition to dichloroalkane and sodium sulfide in order to form a branched polymer. The prepolymer is treated with a mixture of sodium hydrosulfide and sodium sulfite followed by acidification to convert all end-groups to thiol groups. Further polymerization and crosslinking is achieved by oxidative coupling of the thiol end-groups by treatment with lead dioxide, p-quinone dioxime, or other oxidizing agent... 

Another very important factor in protein architecture is the disulfide —S—S— link. Remote parts of the polypeptide chain can be held close together through the oxidative coupling of two cysteine thiol groups to form a disulfide bridge ... 

There is a wider general interest in understanding the oxidation of cysteine thiolates in proteins since they are involved in redox-sensing reactions [99], Therefore, such oxidation reactions of thiols induced by Ru coordination may also play a more general role in the pharmacological activity of Ru-arene complexes by coupling Ru coordinative binding to redox processes both outside and inside cells. 

Only derivatives of the 1,2-oxathiole series have been obtained by direct heteroatom coupling. The successful bond formation involves some type of activation of the sulfur atom in 3-hydroxypropanethiol or its oxidized derivatives. TTie parent 1,2-oxathiolane system (106) was recently reported (81CC741) to be obtained from the vacuum pyrolysis of (105), as shown in Scheme 23. A cyclic oligomer is believed to be generated first and (106) is formed on standing. Oxidation of (106) yields the mono- and di-oxide which have been known for some time. The monoxide may be obtained by the oxidative coupling of 3-hydroxypropane thiol (equation 22). Chlorine is the most frequently used oxidant and... 

Hydrogen peroxide used over a wide pH range has been employed to oxidize sulfur compounds. The scope of the oxidation using hydrogen peroxide includes coupling of thiols to disulfides355 and thiols coupled with amines,356 which are used to produce industrially important compounds. For example, sulfenamides are accelerators for rubber vulcanization (Figure 3.91).357... 

An attractive reaction has been reported for BY, which is able in ethanol to catalyze the oxidative coupling of various thiols to disulfides (eq 16). ... 

Cystine bridges, disulfide bridges that are formed upon oxidative coupling of two thiol groups of cysteine residues, and frequently occur in peptides and proteins. 

Benzo[l,2,4]dithiazines 160 were synthesized via oxidative coupling of the sulfanyl group and the thiol group on substrate 159 (Equation 39) <2003MI>. Epidithiodiketopiperazine 162 was obtained via deprotection and subsequent oxidation of substrate 161 (Equation 40) <2006TL2387>. 

The use of nanoparticle for the C—S cross-coupling has been reported under ligand-free conditions. Punniyamurthy and coworkers introduced air-stable CuO nanoparticles for the coupling of thiols with aryl iodides [102, 172]. Karvembu [173] and Kakulapati [174] subsequently employed CuO nanoparticles for the coupling of aryl halides with thiophenol and ethyl potassium xanthogenate, respectively. Kamal and coworkers used CuO nanoparticles/graphene oxide for the coupling of aryl chlorides with thiols (Scheme 20.56) [175]. 

Thiol-terminated polymers are by far the most important type of polysulphide polymer manufactured. They may be readily cured by oxidative coupling of the thiol terminals ... 

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