Pseudohalogen Chemistry. III. Orientation of Heterolytic Addition of Thioeyanogen Chloride to Some Unsymmetrical Alkenes

Thiocyanogen chloride reacts with various unsymmetrical alkenes, cycloalkenes, and α-arylalkenes in the presence of a radical inhibitor in acetic acid in the dark at 25 °C to yield α-chloro-β-thiocyanates, α-acetoxy-β-thiocyanates, α-hydroxy-β-thiocyanates, vinylic thiocyanates or allylic isothiocyanates in various combinations. The additions to the α-arylalkenes are regiospecific, yielding the Markownikov-orientated products, but the regiospecificity of the additions to the aliphatic alkenes depends on the structure of the alkene. The orientation of addition is discussed in terms of open carbonium ions, e.g. 17, for the α-arylalkenes and cyano-sulfonium ions, e.g. 18, for the aliphatic alkenes.