Under cooling of an ice water bath, to a solution of cyclohexanone (10 mmol, 1.0 equiv), and 2,6-dimethylpyridine (30 mmol, 3.0 equiv) in dry THF (10 mL) was added triisopropylsilyl trifluoromethanesulfonate (20 mmol, 2.0 equiv). The mixture was warmed to room temperature and stirred for 4 h. After the reaction was complete, a saturated NH4Cl aqueous solution (10 mL) was added to quench the reaction. The organic layer was collected and the aqueous phase was extracted with ethyl acetate.