Dialkyl disulfide, reduction

Symmetrical 3,5-dialkyl-l,2,4-trithiolanes (178) can be synthesized in reasonable yield by chlorination of dialkyl disulfides (175) to a-chiloroalkyl sulfenyl chlorides (176), which are then reacted with potassium iodide to give di-a-chloroalkyl disulfides (177). Subsequent cyclization with sodium sulfide gave (178) (72T3489). When (176) was treated with one molar equivalent of sodium sulfide, the reductive dimerization and cyclization was effected in one step (78HCA1404). Treatment of perfluoropropene with sodium hydrogen sulfide in THF resulted in the formation of 3,5-bis(2,2,2-trifluoroethyl)-l,2,4-trithiolane (179) (72IZV2517). 

Titanium(IV) chloride and titanocene dichloride have catalytic effects on the reduction, e.g., in the transformation of alkyl thiocyanates to dialkyl disulfides and nitroarenes to aryl amines, respectively. 

The voltammetric reduction of a series of dialkyl and arylalkyl disulfides has recently been studied in detail, in DMF/0.1 M TBAP at the glassy carbon electrode The ET kinetics was analyzed after addition of 1 equivalent of acetic acid to avoid father-son reactions, such as self-protonation or nucleophilic attack on the starting disulfide by the most reactive RS anion. Father-son reactions have the consequence of lowering the electron consumption from the expected two-electron stoichiometry. Addition of a suitable acid results in the protonation of active nucleophiles or bases. The peak potentials for the irreversible voltammetric reduction of disulfides are strongly dependent on the nature of the groups bonded to the sulfur atoms. Table 11 summarizes some relevant electrochemical data. These results indicate that the initial ET controls the electrode kinetics. In addition, the decrease of the normalized peak current and the corresponding increase of the peak width when v increases, point to a potential dependence of a, as discussed thoroughly in Section 2. 

Reduction of the w-disulfenyl dichlorides 210 (obtained from dialkyl malonates and sulfur dichloride) under a variety of conditions, afforded, in varying amounts, the corresponding 1,2,4,5-tetrathianes 211, sometimes with concomitant formation of the tetrasulfides 212 or the disulfides 213 (Equation 18) <2000EJ02583>. 

Evidence has been presented for an atom transfer redox process in the reduction of Au(III) by dialkyl sulfides in aqueous methanol. The two-stage reaction involves initially a substitution equilibrium which is strongly dependent on the bulkiness of the entering sulfide. A second mole of disulfide is required in the subsequent redox reaction leading to Au(I) and sulfoxide. The attack occurs via a chlorine atom of the AuCl" reagent which is transferred to the sulfur, leaving an electron pair at the metal center. The reaction is markedly solvent dependent. 

Lower dialkyl sulfides are often employed as valuable solvents. Most organic sulfides with low molecular mass have intense unpleasant odors. Cotmnercial dimethyl sulfide contains highly malodorous impurities such as carbon disulfide, carbonyl sulfide, methyl thiol, dimethyidisulfide, hydrogen sulfide and other sidfurous compounds at low levels. Dialkyl sulfide borane complexes of high purity are used to produce low odor dialkyl sulfides by enantioselective reduction. ... 

---