However, the substrate scope could not be expanded to amides. Several amides
were tried under various reaction conditions; no desired product was obtained.
In 2013, Schomaker and coworkers reported highly chemoselective amidation of
C¼C and sp
3 C–H bonds by silver catalyst (Scheme 7) [29]. AgOTf was used as the
catalyst with phenanthroline as ligand set in the presence of PhIO as the oxidant and
4 Å molecular sieves as additive in DCM. The reaction ran at room temperature.
The ratio of AgOTf/ligand is critical since it controlled the reaction pathways to
form either aziridination or C–H insertion product. The substrate scopes were
Scheme 6 Silver-mediated intramolecular amination of sp
3 C–H bonds
R
O
H H
NH 2
O
R
HN
O
O
R
N
O
O
N
N
Ag
OTf
N
N
Ag
OTf
N
N
+phenanthroline
-phenanthroline
AgOTf/ligand = 1/3
AgOTf/ligand = 1/1.25
Me
Me
H
O
NH 2
O
H
H
H
O
H H
NH 2
O
Et
H
Substrate (AgOTf/ligand = 1/3)
Product
a
b
a
b
Substrate (AgOTf/ligand = 1/3)
Product
a dr(cis:trans) b
H
H
O
NH 2
O
Me
Me
H
H
H
O
H H
NH 2
O
H 9 C 4
H
Et
H
H 11 C 5
H
O
NH 2
O
H
H
Et
O
H H
NH 2
O
H
H
H
H
O
NH 2
O
H
H
O
H H
NH 2
O
H
Me
81%
0
H 11 C 5
76%
1%
C 3 H 7
76%
0
TBSO
36%
0
93%
0
87%
4%
73%
11%
68%
0
--3:1
--2.4:1
Scheme 7 Silver-catalyzed tunable, chemoselective sp
3 C–H amination
122
T. Zhou and Z.-J. Shi