A One-Pot Anodic Thiocyanation of Alkenes

Avishai Levy, Chemistry, Ben Gurion University of the Negev, Beer Sheva, Israel

Electrochemical thiocyanation of alkenes was studied in an undivided cell using a one-pot, two-phase medium (water-dichloromethane) or one phase with two solvents (water-acetonitrile), employing a constant current electrolysis (CCE). The aqueous solvent is utilised to oxidise thiocyante anions, and the organic solvent is utilised to dissolve the alkene substrate and stabilise the electro-generated thiocyanogen (SCN)₂ which is unstable in aqueous media. Thiocyanation was first implemented on a model alkene, the symmetric 2,3-dimethyl-2-butene, using a two-phase medium. The major product is a mixed di-addition of thiocyano and isothiocyano groups to the double bond. Other minor products involve addition of two thiocyano groups, one thiocyano and one hydroxy group, and a trace amount of one thiocyano group and a hydrogen atom. 

When implementing the one phase – two solvents system (CH₃CN-H₂O) on the same substrate, the thiocyano and hydroxyl vicinal addition becomes more prominent.

After obtaining "optimal" conditions, other alkenes were examined.