Table 1.

Optimization of the Reaction Conditions.^a

entry	catalyst	additiveb	solvent	temp (°C)	yield %
1	–	–	Et2O	23	0
2	CuCl	–	Et2O	23	53
3	FeCl2	–	Et2O	23	36
4c	FeCl2/SIMes	–	THF	23	0
5	CoCl2	–	Et2O	23	6
6	Ni(PPh3)2Cl2	–	THF	23	3
7	NiCl2·dme	–	Et2O	23	0
8	CuCl2	–	Et2O	23	17
9	CuBr	–	Et2O	23	21
10	CuCl	–	THF	23	45
11	CuCl	–	PhMe	23	38
12	CuCl	–	Et2O	0	44
13	CuCl	–	Et2O	−20	25
14	CuCl	–	Et2O	50	42
15	CuCl	LiCl	Et2O	23	67
16	CuCl	ZnBr2	Et2O	23	0
17	CuCl	tmeda	Et2O	23	2
18	CuCl	MgCl2	Et2O	23	95
19	CuCl	MgF2	Et2O	23	37
20	CuCl	LiF	Et2O	23	96

^aReaction conditions: 1 (0.17 mmol), 2 (1.5 equiv), catalyst (10 mol %), in the solvent (1 mL) under Ar for 12 h.

^b1.5 equiv

^cSIMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene.