Table 1.

Optimizations of reaction conditions^a.

Entry	Catalyst	Reaction conditions	Yield (%)b
1	CuOTf	DCE, 40 °C,6 h	37
2	Cu(MeCN)4BF4	DCE, 40 °C, 6 h	41
3	Cu(MeCN)4PF6	DCE, 40 °C, 6 h	53
4	Cu(MeCN)4PF6	DCM, 40 °C, 6 h	52
5	Cu(MeCN)4PF6	CHCl3, 40 °C, 10 h	30
6	Cu(MeCN)4PF6	PhMe, 40 °C, 10 h	28
7	Cu(MeCN)4PF6	PhCl, 40 °C, 9 h	47
8c	Cu(MeCN)4PF6	DCE, 40 °C, 6 h	38
9d	Cu(MeCN)4PF6	DCE, 40 °C, 6 h	52
10e	Cu(MeCN)4PF6	DCE, 40 °C, 4 h	68
11e	Cu(MeCN)4PF6	DCE, 40 °C, N2, 4 h	72
12e	Cu(MeCN)4PF6	DCE, 20 °C, N2, 12 h	71
13e	Cu(MeCN)4PF6	DCE, 60 °C, N2, 2 h	70

^aReaction conditions: 1a (0.05 mmol), 2a (2–10 equiv), catalyst (0.005 mmol), solvents (1 mL), 40–60 °C, 2–12 h, in vials.

^bMeasured by ¹H NMR using 1,3,5-trimethoxybenzene as internal reference.

^c2 equiv of 2a was used.

^d10 equiv of 2a was used.

^e12 mol % of NaBAr^F₄ was added.

Ns = 4-nitrobenzenesulfonyl.