Table 3. Further optimization of C(sp²)–H hydroxylation ^{a , b} .

Entry	Copper salts	Base	Acid	Yield
				3a	2a
1	Cu(OAc)2 + CuBr	Cs2CO3	PivOH	59	12
2	Cu(OAc)2 + CuBr	Cs2CO3	1-Ad-COOH	61	13
3 c	Cu(OAc)2 + CuBr	Cs2CO3	1-Ad-COOH	63	12
4 c , d	Cu(OAc)2 + CuBr	Cs2CO3	1-Ad-COOH	63	11
5 c , d , e	Cu(OAc)2 + CuBr	Cs2CO3	1-Ad-COOH	66	8
6 c , d , e , f	Cu(OAc)2 + CuBr	Cs2CO3	1-Ad-COOH	67	8
7 c , d , e , f	Cu(OPiv) 2 + CuBr	Cs 2 CO 3	1-Ad-COOH	75(80) g	0
8 c , d , e , f	Cu(OCOiPr)2 + CuBr	Cs2CO3	1-Ad-COOH	68	0
9 c , d , e , f	Cu(OCO)2 + CuBr	Cs2CO3	1-Ad-COOH	45	0

^aReaction conditions: 1 (0.1 mmol), Cu(OAc)₂ (0.2 mmol), CuBr (0.08 mmol), base (0.15 mmol), acid (0.15 mmol), ligand (0.1 mmol), DMSO (1.0 mL), 100 °C, air, 6 h.

^bYield determined by ¹H NMR analysis of crude reaction mixture using CH₂Br₂ as an internal standard.

^cAcid (0.18 mmol).

^dCuX₂ (0.15 mmol).

^eDMSO (0.5 mL).

^fLigand (0.04 mmol).

^g105 °C.