those consisting of tetrafluoroborate, alkylsulfate, alkylsulfonate, carboxylate, or phosphate anions are hydrophilic and are completely dissolved in water. Dupont and coworkers first reported stable hydrophobic imidazolium salt, 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) in 1996. Since then, this salt has been used as a typical hydrophobic IL in many chemical reactions because its mixture with water forms a biphasic layer. Furthermore, this IL shows poor solubility in hexane or ether, which allows realization of an easy work-up process. However, [C4mim][PF6] was reported to be sensitive to the moisture at high temperature and produced hazardous hydrogen fluoride as it decomposed. Therefore, bis(trifluoromethanesulfonyl)amide (NTf2) salts are now recommended as the anion for preparing hydrophobic IL