The influence of room-temperature ionic liquids on the stereoselectivity and kinetics of the electrochemical pinacol coupling of acetophenone

Abstract

The electrochemical pinacol coupling of acetophenone is performed in three ionic liquids, [BMIM][NTf₂] (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), [Me₃BuN][NTf₂] (trimethylbutylammonium bis(trifluoromethylsulfonyl)imide), and [Et₃BuN][NTf₂] (triethylbutylammonium bis(trifluoromethylsulfonyl)imide). Besides the high operational simplicity of electrolysis in ionic liquids and particularly the ease of product recovery, as compared to conventional electrolytes, ionic liquids are also demonstrated to exert strong effects on both the stereoselectivity and kinetics of the reaction. Because ion associations occur between the radical anion intermediates and the ionic liquid cations, the dimerization step is considerably facilitated. Depending on the strength of the ionic interactions, the stereoselectivity or the kinetics is increased.