To demonstrate the practicality of this visible-light and cobalt-catalyzed direct allylic C-H oxygenation of terminal alkenes, the reaction of 1a with 2a was successfully scaled up to 1.0 mmol scale. Desired branched allylic ether 3a was obtained in 78% isolated yield (Scheme 3a). Next, a series of control experiments were performed to elucidate the mechanism of this room temperature C-H oxygenation reaction. The reaction of 1a and 2a in the presence of a radical scavenger TEMPO under otherwise identical to standard conditions was carried out (Scheme 3b). No desired C-H alkoxylation product 3a