Table 1.

Reaction Optimization

Entry	Variation from the Standard Conditionsa	Yield (%)b
		4a	13
1	Under natural light, 0°C to rt	43	15
2	In the dark, 0°C to rt	35	18
3	Under CFL, 0°C to rt	59	13
4	Under CFL, −20°C to rt	70	8
5	Under CFL, −40°C to rt	80	<5
6	Na2CO3 as the base, under CFL, −40°C to rt	73	<5
7	t-BuOLi as the base, under CFL, −40°C to rt	54	<5
8c	PhIO instead of MnO2, Na2CO3 as the base, in one pot	66	<5

^aReaction conditions: 2a (0.45 mmol), MnO₂ (8.0 equiv. based on 2a), MgSO₄ (60.0 mg), and DCE (3.0 mL) was pre-stirred for 45 min, then the reaction mixture was filtered and injected to the oven-dried tube, which was equipped with 3a (0.15 mmol), Cs₂CO₃ (2.0 equiv.), and the mixture was carried out at −40°C to room temperature under argon atmosphere for 10 h with the irradiation of visible light (8 W CFL).

^bIsolated yield based on 3a.

^cReaction conditions: 2a (0.30 mmol), PhIO (0.30 mmol), 3a (0.15 mmol), Na₂CO₃ (0.30 mmol), 4Å MS (50 mg), and DCE (2.0 mL) was carried out in one pot at −40°C to rt. under argon atmosphere for 10 h with the irradiation of visible light (8 W CFL).