Optimization of reaction conditions^a.

Entry	Additive	Solvent	Yield of 3aa/%	Yield of 4aa/%
1	AgTFA	PhMe	0	0
2	AgTFA	DCE	0	0
3	AgTFA	1,4-Dioxane	0	0
4	AgTFA	TFE	21	3
5	AgTFA	HFIP	59	4
6	AgTFA	HFIP	0	0b
7	—	HFIP	0	0
8	AgOAc	HFIP	5	<3
9	Ag2O	HFIP	<3	<3
10	K2HPO4	HFIP	0	0
11	Na2CO3	HFIP	0	0
12	AgTFA	HFIP	53	4c
13	AgTFA	HFIP	42	3d
14	AgTFA	HFIP	71	<3 e
15	Ag2CO3	HFIP	9	34f
16	Ag 2 CO 3	HFIP	5	55 f , g

^aReaction conditions: 1a (0.20 mmol), 2 (0.48 mmol), Pd(OAc)₂ (10 mol%), additive (0.48 mmol), solvent (0.50 mL), 25 °C, 16 h, and isolated yield.

^bWithout Pd(OAc)₂.

^cAt 40 °C.

^dAt 60 °C.

^eTFA (0.2 mmol) was added.

^f 1a (0.20 mmol), 2a (0.24 mmol), Pd(OAc)₂ (5.0 mol%), and Ag₂CO₃ (0.24 mmol).

^g 2a was added in three portions every 4 h. DCE = dichloroethane, TFE = 2,2,2-trifluoroethanol, HFIP = hexafluoroisopropanol, and TFA = trifluoroacetic acid.