Control reactions^a.

Entry	TiO2 (z equiv.)	Light	Oxidant	Yield 3aa (%)
1	10	Darkb	Air	—
2	10	440 nm	Argon	—
3	—	440 nm	Air	—

^aReaction conditions: 1a (1.12 mmol), 2a (0.56 mmol) 4.0 mL solvent, 12 h.

^bReaction ran without light source; reaction flask wrapped with foil.