Reaction optimization^a.

Entry	Variation from standard conditions	Yieldb (%)
1	None	74
2	Ts-ABZ as limiting reagent	69
3	2a as limiting reagent	44
4	C = 0.05 M	74
5	C = 0.2 M	60
6	Room temperature	50
7	No BF3·Et2O	49
8	No light or photocatalyst	<5

^aReactions were carried out on 0.1 mmol scale. Light irradiation was carried out using a single Kessil lamp.

^bNMR yield determined using CH₂Br₂ as internal standard.