Metal free: A novel and efficient aerobic oxidation of toluene derivatives catalyzed by N′, N″, N‴, -trihydroxyisocyanuric acid and dimethylglyoxime in PEG-1000-based dicationic acidic ionic liquid

A non-metal catalytic system containing of N′, N″, N‴, -trihydroxyisocyanuric acid (THICA) and dimethylglyoxime (DMG) is described for the selective oxidation of toluene derivatives with dioxygen in PEG-1000-based dicationic acidic ionic liquid (PEG1000–DAIL). Several toluene derivatives were efficiently oxidized to corresponding acids under mild conditions. The oxidation followed a radical pathway and a possible mechanism was proposed. Both the catalyst and PEG1000–DAIL could be reused at least eight times without significantly decreasing the catalytic activity.

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► THICA-DMG was used in the oxidation of toluene-substituted derivatives.
► Ionic liquid PEG1000 –DAIL was used as solvent.
► A possible mechanism of this catalytic process was proposed.
► The catalyst could be reused at least eight times.