Preparation of Disulphides, Hydrodisulphides, and Oligosulphides

Oxidation of thiols to disulphides can be brought about by using Ij, KaFe(CN)g, FeClg, l,3-dihydro-l-hydroxy-3-oxo-l,2-benziodoxole, or manganic tris(acetylacetonate).  

Unsymmetrical disulphides are prepared by the reaction of thiols with sulphenyl compounds, a new synthesis of this type involving first the conversion of a thiol R SH into R SSC02R by its reaction with CISCO2R in MeOH at 0 °C, followed by room-temperature reaction of the intermediate with a second thiol R SH to give R SSR and HO CS -OR . Acetyl sulphenyl chlorides AcSCl similarly yield AcSSR with RSH, - though the product is susceptible to attack by the thiol, resulting in the formation of symmetrical disulphides. Acyl alkyl 

622 J Nakaya, H. Arabori, and M. Imoto, Bull. Chem. Soc. Japan, 1970, 43, 1888. 

2-Naphthylsulphenyl thiocyanate, 2-Cjt)H7 S SCN, is readily converted into di-(2-naphthyl) disulphide with Fe(CO)6-THF at — 70 °C, and has been used for the conversion of JV-benzyloxycarbonyl-selenocysteine diphenylmethyl ester into the 5e-(2-naphthylsulphenyl) derivative, the seleno-sulphide R SSeR , though this disproportionates readily, especially in basic media, and diselenides and disulphides appear in the product mixture for this reason. The Bunte salt, PhCHa-S-SOg Na+, gives similar results when used in place of the sulphenyl thiocyanate in these studies, and this general route to disulphides - and diselenides, and its variant BuS-S03 Na+ + TolSCl- BuSSBu + TolSSTol, have been explored more widely. 

Incidental reference has been made to disulphide formation elsewhere in this Chapter, and a number of alternative methods have been explored /3-dimethylaminoethyl and y-dimethylaminopropyl diselenides have been prepared from the corresponding alkyl chloride and NagSeg cyanolysis 

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