Optimization concerning solvent^a.

Entry	Solventbb	Reagent	Cool white LED (photon flux: 46 μmol s−1)	Time (h)	Yieldc (%)
1	CH3CN	NBS	Yes	1	84
2	CH3OH	NBS	Yes	15	45*
3	CH3CH2OH	NBS	Yes	15	47*
4	CH3COOCH2CH3	NBS	Yes	15	41*
5	CHCl3	NBS	Yes	15	27*
6	H2O	NBS	Yes	15	NA
7	DMSO	NBS	Yes	15	36*
8	DMF	NBS	Yes	6	79
9	CH3CN	NBS	Dark	15	65*
10	CH3OH	NBS	Dark	15	33*
11	CH3CH2OH	NBS	Dark	15	40*
12	CH3COOCH2CH3	NBS	Dark	15	11*
13	CHCl3	NBS	Dark	15	9*
14	DMF	NBS	Dark	15	38*
15	DMSO	NBS	Dark	15	21*
16	H2O	NBS	Dark	15	NA

^aReaction condition: 1 (0.6 mmol) and NBS were taken in different solvents.

^bVolume of solvent: 1 mL.

^cPure product was isolated by silica-gel column chromatography, * starting material was not consumed.