To shed light on the reaction mechanism, a series of controlled experiments were conducted. First, the reaction was carried out in the presence of TEMPO as a radical scavenger under otherwise identical to standard conditions, the desired transformation was completely inhibited (Scheme 5a). Second, 4-methylcyclohexanone 1a delivered silyl enol ether 1bf in 97% yield in dark under otherwise identical to standard conditions (Scheme 5b). Interestingly, 1bf was successfully converted to phenol 2 in 78%% yield in the presence of 20 mol% trifluoromethanesulfonic acid under otherwise identical to standard conditions (Scheme 5b). These experiments suggest that the silyl enol ether may serve as key intermediate in the reaction. Moreover, the reaction of silyl enol ether 1be under standard conditions in the presence of benzalmalononitrile 1bg delivered 57 in 85% yield (dr = 2:1). Alternatively, the reaction of silyl enol ether 1be under standard conditions in the presence of α,β-unsaturated sulfones 1bh afforded β-substituted cyclohexanone 58 in 69% yield (Scheme 5c). The results indicate the reaction is likely to undergo an allylic radical intermediate. In addition, Stern-Volmer luminescence quenching experiments were performed. Both 4-methylcyclohexanone and 2,4,6collidine did not show significant quench of the excited state of photocatalyst [Ir(Ⅲ)] * . Silyl enol ether showed a relatively strong quenching effect to the excited photocatalyst (Scheme 5d). These observations confirmed that the reaction was initiated by the singleelectron oxidation of silyl enol ether by photocatalyst.