Table 1. Optimization of Reaction Conditions^a.

			yield (%)b
entry	catalyst (mol %)	additive (equiv)	3aa	3aa′	4a
1	CuBr (30)		22	19	18
2	CuBr (50)		13	25	38
3	CuBr (100)		trace	34	58
4c	CuBr (100)				80
5	CuBr (30)	TBAB	27	33	Trace
6	CuI (30)	TBAB	25	14	Trace
7	CuBr2 (30)	TBAB	31	12	Trace
8	CuCl2·2H2O (30)	TBAB	28	35	Trace
9	Cu(OAc)2·H2O (30)	TBAB	23	27	Trace
10	Cu(OCOCF3)2 (30)	TBAB	28	40	Trace
11	CuSO4·5H2O (30)	TBAB	30	36	Trace
12		TBAB
13d	Cu(OCOCF3)2 (30)	TBAB
14e	Cu(OCOCF3)2 (30)	TBAB	24	trace	Trace
15f	Cu(OCOCF3)2 (30)	TBAB	17	trace	Trace
16g	Cu(OCOCF3)2 (30)	TBAB
17	Cu(OCOCF3)2 (30)	TBAI	27	40	trace
18	Cu(OCOCF3)2 (30)	TBAC	26	43	trace
19h	Cu(OCOCF3)2 (30)	TBAB	31	21	trace
20i	Cu(OCOCF3)2 (30)	TBAB	26	46	trace
21i,j	Cu(OCOCF3)2 (30)	TBAB	31	40	trace

^aReaction conditions: 1a (0.1 mmol), 2a (0.2 mmol), Ag₂CO₃ (2 equiv), additive (1 equiv), solvent (2 mL): toluene/DMF (1:1), in air.

^bIsolated yield.

^cWithout 2a, 8 h.

^dWithout Ag₂CO₃.

^eAgOAc (2 equiv).

^fAgOCOCF₃ (2 equiv).

^gK₂S₂O₈ (2 equiv).

^h130 °C.

ⁱ150 °C.

^jUnder Ar atmosphere.