was detected, suggesting a potential radical nature of the reaction. To further prove the radical nature of this reaction, a radical clock reaction using allylic cyclopropane 4 and ethanol under standard conditions in presence of TEMPO (1.0 equiv) was performed (Scheme 3c). No desired allylic C-H oxygenation product was obsevered. Instead, a ring-openning adduct 5 from 4 and TEMPO was obtained in 26% yield, which may undergo the benzylic radical (5-1) enabled ring-opening of cyclopropane to generate alkyl radical intermediate (5-2), followed by radical trap with TEMPO. To further understand the mechanism of the reaction, time course of the reaction was monitored under standard conditions using 1u and 2a as substrates (Scheme 3d). Interestingly, 1u was almost completely consumed within 5 minutes, yet no substantial amount of desired allylic C-H oxygenation product 7 was formed. Instead, an internal alkene 6 was generated in quantitative yield. Then, the formation of 7 increased along with the consumption of