Table 1.

Reaction condition optimization.^a

entry	Cu cat.	solvent	temp (°C)	yield (%)a
1	CuI	THF	80	85b
2	CuI	THF	80	88
3	CuI	toluene	80	75
4	CuI	DCE	80	65
5	CuI	1,4-dioxane	80	82
6	CuI	MeCN	80	90
7	-	MeCN	80	0
8	CuI	MeCN	rt	39
9	CuI	MeCN	50	93
10	CuCl	MeCN	50	88
11	CuBr	MeCN	50	98
12	CuBr	MeCN	50	93b
13	CuBr	MeCN	50	80c
14	CuBr	MeCN	50	traced

^aGeneral reaction conditions: A solution of 1a (0.15 mmol), 2a (0.1 mmol), and Cu(I) catalyst (0.1 equiv) were stirred until no more starting material left. The reaction process was monitored by thin-layer chromatography. Isolated yield from flash chromatography was given;

^b1/1 of 1a/2a (0.1 mmol);

^c1a (0.1 mmol) and 2a (0.15 mmol);

^dPhenanthroline (0.1 equiv).