Table 1. Optimization of the reaction conditions^a.

Entry	I2 (x eq.)	Additives (x eq.)	Temp (°C)	Yieldb (%)
1	1.6	—	100	48
2	1.6	50% HI (1.0)	100	55
3	1.6	CH3CO2H (1.0)	100	53
4	1.6	CF3CO2H (1.0)	100	32
5	1.6	CF3SO3H (1.0)	100	51
6	1.6	TsOH (1.0)	100	68
7	1.6	ZnCl2 (1.0)	100	61
8	1.6	CuBr2 (1.0)	100	57
9	1.6	Cu(OTf)2 (1.0)	100	44
10	1.6	FeCl3 (1.0)	100	59
11	1.6	Fe(OTf)3 (1.0)	100	52
12	1.6	TsOH (0.5)	100	60
13	1.6	TsOH (1.5)	100	75
14	1.6	TsOH (2.0)	100	69
15	0.8	TsOH (1.5)	100	51
16	1.2	TsOH (1.5)	100	62
17	2.0	TsOH (1.5)	100	67
18	1.6	TsOH (1.5)	80	47
19	1.6	TsOH (1.5)	120	70

^aReaction conditions: 1a (1.0 mmol), 2a (1.0 mmol), 3a (1.0 mmol), I₂ (x equiv), additive (x equiv), 6 h, DMSO (6.0 mL), indicated temperature, unless otherwise noted.

^bIsolated yields.