Optimization of the reaction conditions^a.

Entry	Solvent	Oxidant	Time (h)	Temp (°C)	Yield (%)
1	DMSO	SF	24	100	71, 15b, 65c
2	DMF	SF	24	100	23
3	DMAC	SF	24	100	Trace
4	Toluene	SF	24	100	0
5	NMF	SF	24	100	18
6	DMSO	(NH4)2S2O8	24	100	Trace
7	DMSO	K2S2O8	24	100	33
8	DMSO	—	24	100	0
9	DMSO	SF	48	100	73
10	DMSO	SF	16	100	46
11	DMSO	SF	8	100	23
12	DMSO	SF	4	100	Trace
13	DMSO	SF	24	120	67
14	DMSO	SF	24	80	56
15	DMSO	SF	24	60	29
16	DMSO	SF	24	40	0

^aReaction conditions: 1a (1 mmol), 2 (1 mmol), oxidant (1.1 mmol) and DMSO (3 mL) in a sealed tube at the indicated reaction conditions.

^bReaction under N₂.

^cReaction was performed on a 10 mmol scale of 1a.