Sulfides reductive cleavage

Reductive pathways that are encountered less frequently in dnig metabolism include reduction of Af-oxides to their corresponding tertiary amines and reduction of sulfoxides III sulfides. Reductive cleavage of disulfide linkages and reduction of carbon-carbon double bonds also occur, but constitute only minor pathways in drug metabolism. 

The reductive cleavage of allyl ethers 28 30 or sulfides is preferred over the metalation of allyl... 

Tetraorganyldiphosphine sulfides, R2 P(S)-PR2 (R = Ph, Me) can be reduced in DMF/Et4NI at about —1.8 V versus the Hg pool [197]. The process is supposed to occur with the two-electron reductive cleavage of one of the bonds formed by sulfur. Under similar... 

Reductive cleavage of 1,3-dithiolanes is accomplished in low yields with sodium in liquid ammonia and gives either dithiols or mercapto sulfides depending on substituents in position two [679]. 

The classical preparation of alkyllithium compounds by reductive cleavage of alkyl phenyl sulfides with lithium naphthalene (stoichiometric version) was also carried out with the same electron carrier but under catalytic conditions (1-8%). When secondary alkyl phenyl sulfides 73 were allowed to react with lithium and a catalytic amount of naphthalene (8%) in THF at —40°C, secondary alkyllithium intermediates 74 were formed, which finally reacted successively with carbon dioxide and water, giving the expected carboxylic acids 75 (Scheme 30) °. 

A few mechanisms were postulated for this reaction (6). No matter what mechanism is considered, the oxidation of elemental sulfur or thiosulfate is accompanied by reductive cleavage of the sulfur-sulfur bridges. In the case of sulfur, the intermediate involved is a cyclic form of sulfur, probably Ss, although there is little difference observed for different allotrophic forms of sulfur such as rhombic, precipitated, and amphorous. These cyclic sulfides form the basis of polysulfanes and polythionates which could be metabolized readily by Thiobacilli (as shown in Figure 3). Actually, sulfur oxidation begins with its reduction, in which the gluathione-sulfhydryl groups located near the cell surface take part ... 

Reductive cleavage oflH-tMopyrane (l).4 T reatment of 1 with 2 equi v. of sodium in HMPT generates a dianion (a) by a selective cleavage of the S-vCH2 bond. Protonoloysis followed by methylation yields the pure (Z,Z)-diunsaturated methyl sulfide 2 with retention of configuration of the double bonds. 

Both permanganate and ozonolysis break the carbon-carbon double bond and replace it with carbonyl (C=0) groups. In the permanganate cleavage, any aldehyde products are further oxidized to carboxylic acids. In the ozonolysis-reduction procedure, the aldehyde products are generated in the dimethyl sulfide reduction step (and not in the presence of ozone), and they are not oxidized. 

The following discussion will be focused on the effect of structural variations on the kinetics of fragmentation, the cleavage mode, and the stepwise or concerted nature of the process. Similar concepts have also been applied to the reductive cleavage reactions of other series of substrates, i.e. a-substituted acetophenones [246-250], perbenzoates [240, 251], peroxides [242, 252-256], sulfides [244, 257, 258], sulfonium salts [259-263], nitrocumenes [264, 265], arylmethyl aryl ethers and thioethers [266-270]. 

Dimethylphosphine has been prepared by alkylation of phospho-nium iodide with methjd iodide and by reductive cleavage of phosphorus sulfides with methyImagnesium bromide. Diethyl-, dibutyl-, and dicyclohexylphosphines have been prepared by reduction of the corresponding tetraalkyldiphosphine disulfides with lithium hydroaluminate in ether. This latter method gives dialkylphosphines uncontaminated by mono- and trialkylphosphines. 

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