(92k) Generation of Superoxide Ion in Room Temperature Ionic Liquids and Its Use in Organic Synthesis

Room temperature ionic liquids (RTILs) have recently gained status as being environmentally benign solvents. The RTILs are nonvolatile and nonflammable. Because of the superoxide ion's mild oxidizing capacity it can be effectively utilized in organic synthesis. In this work we show that stable superoxide ions can be generated in RTILs such as 1-butyl-3-methyl-imidazolium hexafluorophosphate, [BMIM][HFP], and 1-butyl-2,3-dimethyl-imidazolium hexafluorophosphate, [BDMIM][HFP]. It has also been shown that alcohols can be converted into ketones; examples of this type of reaction are the conversion of benzoin to benzil, and benzhydrol to benzophenone. The yield of the products depends greatly upon the structure of the RTIL. For instance, when [BMIM][HFP] was used as the solvent for the reaction, the average yield of benzhydrol to benzophenone was 50%. In contrast, when [BDMIM][HFP] was used the average yield of benzophenone increased to 98%.