Deep eutectic solvent supported TEMPO for oxidation of alcohols

Abstract

A novel deep eutectic solvent supported TEMPO (DES–TEMPO) composed of N,N-dimethyl-(4-(2,2,6,6-tetramethyl-1-oxyl-4-piperidoxyl)butyl)dodecyl ammonium salt ([Quaternium-TEMPO]⁺Br⁻) and urea was prepared. An efficient catalytic system for the oxidation of alcohols with molecular oxygen as terminal oxidant has been developed from DES–TEMPO and Fe(NO₃)₃·9H₂O. The DES–TEMPO/Fe(NO₃)₃ system showed good performances on the selective oxidation of various alcohols to the corresponding aldehydes and ketones under mild and solvent-free conditions. The DES could be recovered easily and recycled up to five times in the oxidation of benzyl alcohol without significant loss of catalytic activity.