Electroorganic Synthesis in Ionic Liquids

Ionic liquids have also attracted significant research interest as environmentally benign reaction media because they are expected to replace hazardous and volatile organic solvents. The advantages of ionic liquids include easy recovery and re-use, in addition to minuscule vapor pressure, nonflammability, and relative inertness. For electroorganic synthesis, ionic liquids serve as good reaction media, because they have relatively wide potential windows and high conductivity. Because ionic liquids 

Simple electrochemical reductions of carbonyl compounds and organic halides have been achieved in ionic liquids. For example, the electrochemical reduction of benzoylformic acid in [emim][Br] (emim = l-ethyl-3-methylimidazolium) gave man-delic acid in 91% yield (Equation 12.2) [7]. 

Cathodic reduction of organic dihalides using a Co(II)-salen complex in [bmim] [BF4] (bmim = l-benzyl-3-methylimidazolium) was carried out successfully to give the corresponding dehalogenated compounds [8], The catalyst-solvent system was readily recycled with little loss of reactivity. 

Ionic liquids are also effective for electrochemical reductive coupling reactions. For example, the cathodic reduction of benzaldehyde in [bmpyr][NTf2] [bmpyr = 1-butyl-1-methylpyrrolidinium NTf2 = bis(trifluoromethylsulfonyl) imide] gave rise to dimerization [9]. Electroreductive coupling of acetophenone in ionic liquids gave the corresponding pinacol as a mixture of diastereomers (Equation 12.3) [10]. 

Ph Me [bmim][NTf2] [Et3BuN][NTf2] [Me3BuN][NTf2] 

---