Optimization of reaction conditions.

Entrya	Deviation from standard conditions	Yieldb (%)
1	None	85(82)c
2	CuCl (20 mol%)	84
3	CuCl (5 mol%)	76
4	No CuCl	0
5	CuI instead of CuCl	70
6	Cu2O instead of CuCl	45
7	CuBr instead of CuCl	58
8	Cu(OAc)2 instead of CuCl	61
9	Cu(OTf)2 instead of CuCl	49
10	L15 (40 mol%)	79
11	No L15	5
12	No K3PO4	10
13	DMSO instead of 1,4-dioxane	13
14	DMF instead of 1,4-dioxane	10
15	Toluene instead of 1,4-dioxane	50
16	H2O instead of 1,4-dioxane	0
17	EtOH instead of 1,4-dioxane	38
18	90 °C instead of 125 °C	67
19	Air instead of N2	10

^aThe general conditions are as follows: 1a (2.0 mmol), CuCl (0.1 mmol), L15 (0.2 mmol), K₃PO₄ (3.0 mmol), 1,4-dioxane (3.0 mL).

^bDetermined by gas chromatography using n-decane as the internal standard.

^cIsolated yield.