Accelerated aerobic oxidative α-hydroxylation of 2-methylcyclohexanone with imidazolium ionic liquids.

• An imidazolium ionic liquid catalysed strategy was suggested for aerobic α-hydroxylation of 2-methylcyclohexanone. • In IL media, anion was suggested to influence the reaction via local polarity. The ILs (BmimBF4 as model) could be separated by extraction with organic solvent directly. • Dissolved in DMSO, cation was proved to interact with carbonyl group and accelerate the reaction significantly with 1H NMR and ATR-FTIR. The great demands of chemical industries for environmental-friendly process draw interests on ionic liquids of high boiling points and low explosion risks. In this work, the aerobic α-hydroxylation of 2-methylcyclohexanone accelerated by 1-alkyl-3-methylimidazolium ionic liquids (ILs) was explored, where the ILs increased the efficiency considerably. ILs could also work as solvent and be separated from reaction mixture by extraction with organic solvents afterwards, where the anion moiety of ILs had a great impact on the reaction. After reaction, ethyl acetate was proved to be well-performed to separate BmimBF 4 for next use. Besides, the imidazolium cation moiety was proved to accelerate the reaction via 1H NMR and ATR-FTIR. For mechanistic study, an interaction between imidazolium cation and ketone was proposed and, moreover, supported by ESI-MS. This work should encourage the application and understanding of ionic liquids in aerobic oxidation. [Display omitted] [ABSTRACT FROM AUTHOR]