Table 1.

Optimization of reaction conditions^a.

Entry	Oxidants	Equivalent	Temperature (°C)	Time (h)	Yield (%)b
1	–	–	100	4.0	N.R.c
2	K2S2O8	2.0	100	4.0	N.R.
3	Ag2O	2.0	100	4.0	N.R.
4	CuO	2.0	100	4.0	N.R.
5	CuBr2	2.0	100	4.0	43
6	CuBr2	4.0	100	4.0	95
7	CuBr2	6.0	100	4.0	92
8	CuBr2	4.0	100	2.0	94
9	CuBr2	4.0	90	2.0	88
10	CuBr2	4.0	80	2.0	57
11	CuBr2	4.0	70	2.0	N.R.
12	CuBr2	4.0	100	1.5	94
13	CuBr2	4.0	100	1.0	89
14d	CuBr2	4.0	100	1.5	92

^aUnless otherwise specified, all reactions were performed with 0.03 mmol of 1a in 10.0 mL of o-DCB under an argon atmosphere.

^bIsolated yield.

^cNo reaction.

^dUnder an ambient environment.