Table 1. Optimization of the reaction conditions ^a .

Entry	[Cu]	Ligand	Additive	Base	Solvent	Yield (%)
1	CuBr	L1	—	K2CO3	MeCN	42
2	CuBr2	L1	DEAD	K2CO3	MeCN	36
3	Cu(acac)2	L1	DEAD	K2CO3	MeCN	83
4	Cu(OAc)2	L1	DEAD	K2CO3	MeCN	86
5	Cu(OAc)2	L1	—	K2CO3	MeCN	61
6	Cu(OAc)2	L2	DEAD	K2CO3	MeCN	52
7	Cu(OAc)2	L3	DEAD	K2CO3	MeCN	34
8	Cu(OAc)2	L4	DEAD	K2CO3	MeCN	75
9	Cu(OAc)2	L5	DEAD	K2CO3	MeCN	80
10	Cu(OAc)2	L1	AIBN	K2CO3	MeCN	62
11	Cu(OAc)2	L1	V65	K2CO3	MeCN	65
12	Cu(OAc)2	L1	DEAD	Cs2CO3	MeCN	47
13	Cu(OAc)2	L1	DEAD	DBU	MeCN	21
14	Cu(OAc)2	L1	DEAD	K2CO3	THF	Trace
15	Cu(OAc)2	L1	DEAD	K2CO3	PhMe	Trace
16	Cu(OAc)2	L1	DEAD	K2CO3	DMF	14

^a Reaction conditions: 1a (0.25 mmol), 2a (0.30 mmol), [Cu] (10 mol%), ligand (20 mol%), additive (20 mol%), base (0.25 mmol), solvent (3 mL), under N₂ 80 °C, 10 h. Yields of the isolated products are given.