To a solution of 3a (42 mg, 0.178 mmol, 1.0 eq) and triethylsilane (0.0567 mL, 0.356 mmol, 2.0 equiv.) in 1,2-dichloroethane (1.78 mL) in a test tube was added Co(thd)2 (3.78 mg, 0.0089 mmol, 5 mol %) at room temperature. The reaction mixture was stirred under an oxygen atmosphere (balloon) at room temperature for 1.5 h (The reaction mixture turned green after approximately 20 min). After the consumption of 3a on TLC (The corresponding peroxide appeared at a higher position on the TLC plate.), the solution was then sparged with nitrogen gas for 15 minutes to expel excess oxygen gas. MeOH (1.78 mL), γ-terpinene (0.114 mL, 0.712 mmol, 4 equiv.), and FeSO4•7H2O (69.3 mg, 0.249 mmol, 1.4 equiv.) were added sequentially to the reaction mixture at -30 °C. After stirring for 14 h at room temperature, the reaction was quenched by adding water. The reaction mixture was extracted with CH2Cl2 (three times), and the combined organic layers were dried over MgSO4, and then concentrated. After removing the solvent, column chromatography on silica gel with hexane/ethyl acetate (9/1 to 8/2) afforded the product 3c (25 mg, 71% yield) as a white powder.