Table 2.

Iron and copper-catalyzed aerobic oxidation of pyridine-substituted 2-benzylpyridines (3).^a

Entry	Catalyst	Substrate	R	Product	Yield 3 (%)b	Yield 4 (%)b
1	FeCl2·4H2O	3a	5-CN	4a	19	67
2	CuI	3a	5-CN	4a	18	66
3	CuI	3a	5-CNc	4a	0	83
4	FeCl2·4H2O	3b	5-Me	4b	9	73
5	CuI	3b	5-Me	4b	9	82
6	CuI	3b	5-Mec	4b	0	72
7	FeCl2·4H2O	3c	5-OMe	4c	65	15
8	CuI	3c	5-OMe	4c	66	15
9	CuI	3c	5-OMed,e	4c	0	65
10	FeCl2·4H2O	3d	5-CO2Me	4d	0	69
11	CuI	3d	5-CO2Me	4d	0	62
12	FeCl2·4H2O	3e	5-NHCOMe	4e	0	64
13	CuI	3e	5-NHCOMe	4e	27	56
14	CuI	3e	5-NHCOMec	4e	0	91
15	FeCl2·4H2O	3f	4-Cl	4f	0	85
16	CuI	3f	4-Cl	4f	8	88
17	FeCl2·4H2O	3g	3-Cl	4g	73	23
18	CuI	3g	3-Cl	4g	71	22
19	CuI	3g	3-Cld,e	4g	0	87
20	FeCl2·4H2O	3h	5-Cl	4h	70	20
21	CuI	3h	5-Cl	4h	69	15
22	CuI	3h	5-Cld,e	4h	0	92
23	FeCl2·4H2O	3i	6-Cl	4i	90	0
24	CuI	3i	6-Cl	4i	91	0
25	CuI	3i	6-Cle, f	4i	0	59

^aReactions were performed on a 0.5 mmol scale in 1 mL of solvent using 1 atmosphere of O₂ (balloon). ^bIsolated yields. ^c48 h. ^dAcOH (3 equiv). ^e130 °C. ^fTFA (3 equiv).