Cleavage of carbon-sulfur

The reductive capability of CgK has been a subject of interest (LA). Uses for CgK include the reductive cleavage of carbon-sulfur bonds (S5), the reductive alkylation of nitriles and esters (S6), and the reductive alkylation of aldehydes and ketones (S7). The activity of CgK has... 

Kirimura K, T Furuya, R Sato, Y Ishii, K Kino, S Usami (2002) Biodesulfurizarion of naphthothiophene and benzothiophene through selective cleavage of carbon-sulfur bonds by Rhodococcus sp. strain WU-K2R. Appl Environ Microbiol 68 3867-3872. 

Biodesulfurization (BDS) is the excision (liberation or removal) of sulfur from organosul-fur compounds, including sulfur-bearing heterocycles, as a result of the selective cleavage of carbon-sulfur bonds in those compounds by the action of a biocatalyst. Biocatalysts capable of selective sulfur removal, without significant conversion of other components in the fuel are desirable. BDS can either be an oxidative or a reductive process, resulting in conversion of sulfur to sulfate in an oxidative process and conversion to hydrogen sulfide in a reductive process. However, the reductive processes have been rare and mostly remained elusive to development due to lack of reproducibility of the results. Moderate reaction conditions are employed, in both processes, such as ambient temperature (about 30°C) and pressure. 

Kirimura, K. Furuya, T. Sato, R., et al., Biodesulfurization of Naphthothiophene and Ben-zothiophene Through Selective Cleavage of Carbon-Sulfur Bonds by Rhodococcus Sp Strain WU-K2R. Applied and Environmental Microbiology, 2002. 68(8) pp. 3867-3872. 

A viscosity reducing method based on the selective cleavage of carbon sulfur bonds of aromatic heterocyclic molecules containing a sulfur heteroatom. The physicochemical properties of these heterocycles contribute to the liquid viscosity. The method comprises contacting the liquid with an effective amount of a biocatalytic agent. 

Tetrahydrothiazin-3-ones are lactams that have been reduced to tetrahydrothiazines with borane <1980JHC449>, sodium borohydride <1992JOC4215>, or LAH <1987H(26)1503>, without cleavage of carbon-sulfur bond. In one case, incomplete reduction occured with LAH the intermediate lactol was dehydrated to give a dihydrothiazine as main product <1989JPS937>. 

By indirect anodic cleavage of carbon-sulfur bonds it is also possible to initiate rearrangements (Eqs. (105)—(106)) (Table 11, No. 6). 

Graphite reacts with alkali metals - potassium, cesium and rubidium - to form lamellar compounds with different stoichiometries. The most widely known intercalate is the potassium-graphite which has the stoichiometry of CgK. In this intercalate the space between the graphite layers is occupied by K atoms. CgK functions as a reducing agent in various reactions such as reduction of double bonds in a,fl-unsaturated ketones [19], carboxylic acids and Schiff bases alkylation of nitriles [20], esters and imines [21] reductive cleavage of carbon-sulfur bonds in vinylic and allylic sulfones [22]. The detailed reaction mechanism of CgK is not known, and the special properties which are ascribed to the intercalate come either from the equilibrium between K+/K [23], or topochemical observations (the layer structure) [24]. 

The by-products formed are shorter-chain sulfonyl fluorides or chlorides and fluorocarbons [51-54]. The structures of the by-products suggest a cleavage of carbon-sulfur and carbon-carbon bonds and some oxidative degradation as well. 

In this work, researchers employed attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) (Figure 4.6) analysis to support their posmlation on UV-initiated grafting. In their proposed mechanism, the grafting process of the PES membrane started with the absorption of UV-light by phenoxy phenyl sulfone chromophores in the backbone of the polymer chain. Two radical sites were produced at the end of each polymer chains as a result of hemolytic cleavage of carbon-sulfur bond (in sulfone linkage). The produced radicals (aryl and sulfonyl) thus induced the polymerization of acrylic acid at the reactive sites of the radicals. Sulfonyl radical... 

It is well documented that the nickel catalysts or reagents are useful for the cleavage of carbon-sulfur bonds ]25]. Thus, Ni(0)-catalyzed reductive dimerization of aryl thioethers affords the corresponding dimers in satisfactory yield [26]. 

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