Thiols groups

Glycosidic thiol groups can be introduced into glycosyl bromides by successive reactions with thiourea and aqueous sodium disulfite (D. Horton, 1963 M. Cemy, 1961, 1963). Such thiols are excellent nucleophiles in weakly basic media and add to electrophilic double bonds, e.g., of maleic esters, to give Michael adducts in high yields. Several chiral amphiphiles have thus been prepared without any need for chromatography (J.-H. Fuhrhop, 1986 A). 

The piefeiied route depends upon the avajlabihty of a hydrogen atom in the beta-position to the thiol group. In other words, a-toluenethiol (in toluene) decomposes to give 1,2-diphenylethane and hydrogen sulfide, via the homolytic route, whereas 2-methyl-2-propanethiol decomposes to give 2-methyl-1-propene and hydrogen sulfide. 

Thiol groups in the 2-, 3- and 6-positions have been desulfurized with Raney nickel under the usual conditions to give the corresponding unsubstituted compounds. 

The base-catalyzed reaction of thiothreitol with methyl dithiobenzoate selectively protects a thiol group as an 5-thiobenzoyl derivative in the presence of a hydroxyl group.-... 

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