Table 2. Optimization of the sp² C–H carbonylation ^a .

Entry	Cu source	Oxidant	Base	Solvent	Yield b (%)
1	Cu(OAc)2	O2		1,4-Dioxane	17
2	Cu(OAc)2	MnO2		1,4-Dioxane	28
3	Cu(OAc)2	NMO		1,4-Dioxane	33
4	Cu(OAc)2	Ag2O		1,4-Dioxane	19
5	Cu(OAc)2	Ag2CO3		1,4-Dioxane	45
6	Cu(OAc)2	Ag2CO3		DMA	74
7	Cu(OAc)2	Ag2CO3	PhCO2Na	DMA	69
8	Cu(OAc)2	Ag2CO3	Py	DMA	86
9	Cu(OAc)2	Ag2CO3	Na2HPO4	DMA	90(86)
10	CuCl	Ag2CO3	Na2HPO4	DMA	76
11	—	Ag2CO3	Na2HPO4	DMA	0

^aReaction conditions: 3a (0.3 mmol), Cu(OAc)₂ (10 mol%), oxidant (2 eq.), base (1 eq.), solvent (2 mL), 140 °C, 24 h.

^bYields are based on 3a, determined by ¹H NMR using dibromomethane as the internal standard. Isolated yield is in parenthesis.