PSEUDOHALOGEN CHEMISTRY-VII. ADDITION OF THIOCYANOGEN TO ALKYNES

Article abstract of DOI:10.1016/0040-4020(80)80084-6

Thiocyanogen does not react with simple alkynes under heterolytic conditions in benzene at 20-25 deg C.Under homolytic conditions, addition occurs readily giving mixtures of E- and Z-dithiocyanatoalkenes with high E:Z ratios; prolonged treatment with excess reagent also leads to mixtures of the dithiocyanatoalkenes but usually with lower E:Z ratios.A radical-chain mechanism, involving preferential anti-addition of thiocyanogen in an initial kinetically-controlled reaction and subsequent thermodynamically-controlled isomerisation of the adducts, is proposed.The influence of substituents on the reaction rates and product ratios is discussed in terms of their steric effects.