Reactions of Thiocyanates and Isothiocyanates

Reactions of Thiocyanates and Isothiocyanates.—Although these functional groups are structiurally dissimilar from many points of view, a thiocyanate behaving as a sulphenyl cyanide, while an isothiocyanate shows the reactions expected of it on the basis of its heterocumulene structure, there are several examples now of isomerization reactions — S—C=N —N=C=S, partly justifying a unified treatment of their reactions. 

S -Cyanylation of thiols (2-mercaptoethanol, cysteine, or papain) can be achieved with 2-nitro-5-thiocyanatobenzoic acid at pH7—8, at room temperature.  

Edman in Protein Sequence Determination , ed. S. B. Needleman, Chapman  

spectra of isothiocyanato-alkyl radicals, e.g, MeCH NCS from Et NCS, produced by JT-irradiation in adamantane, are interpreted somewhat inconclusively in terms of structure, but are consistent with rapid interconversion of bent planar and linear structures for the —CHj—N-=C=S grouping.  

Allylic rearrangement of thiocyanates to isothiocyanates has been demonstrated for monosaccharide derivatives, - opening up methods for sugar transformations but especially for s mthesizing amino-sugars. For example, (165) gives (166) by way of the isothiocyanate resulting from thermal isomerization. The allylic O-methanesulphonyl substituent in 

---