Screening of solvents for the preparation of sulfonic esters^a.

Entry	Solvent	Yieldb (%)
1	1,4-Dioxane	Trace
2	DMF	Trace
3	THF	22
4	Toluene	35
5	MeCN	39
6	DCE	73
7	CH2Cl2	85

^aReaction conditions: compound 1 (1.0 mmol), MeOH (20 mmol), DABSO (1.0 mmol), CuI (0.1 mmol), HCl (1.0 mmol), irradiation by 5 W blue LEDs for 4 h.

^bIsolated yield after purification of flash column chromatography.