Pseudohalogen chemistry—VI: Homolytic thiocyanation of mono- and di-substituted alkenes using thiocyanogen and ultraviolet light

Under the influence of UV light, thiocyanogen reacts rapidly with mono- and di-substituted alkenes in benzene under nitrogen at 20–30°C to give, depending on the structure of the alkene, α,β-dithiocyanates, allylic isothiocyanates or mixtures of the two in high yields. Additions to acyclic alkenes are trans-stereoselective, while those to alkenes of the cyclohexene family are trans-stereospecific. A radical-chain mechanism, involving competing addition and substitution reactions initiated by the thiocyanato radical, is proposed.