overnight. Good yields were obtained for activating the benzylic C–H bond, while
only moderate yields were obtained for inert C–H bond of cyclic alkanes.
In 2008, Dı ´az-Requejo, Pe ´rez, and coworkers developed a new silver-based
catalytic system which proceeded the direct intermolecular amination of alkanes
[33]. This new catalyzed system employed complexes [Tp
*,Br Ag] 2 8 as catalyst and
PhI¼NTs ([Ag]/[PhI¼NTs]¼1/20) as the nitrene source. The reaction was carried
out in neat alkane at 80
C for 4 h. Linear and branched alkanes were converted to
corresponding isomeric mixtures of amides in moderate to excellent yields
(Scheme 12). The amination/amidation was favored at tertiary sites over secondary
and primary sp
3 C–H bonds of alkanes, and only a few examples were observed at
primary sp
3 C–H bonds. The reaction was inhibited when 2,6-di-tert-butyl-4methylphenol (BHT) was present . Chloroalkanes were observed when CCl 4 was
used as solvent. These evidences indicated that the mechanism involved radical
species.
Although good results were observed for amination/amidation of alkanes, the
reaction needed to carry out in neat substrates. In 2013, Dauban, Dı ´az-Requejo,
Pe ´rez, and coworkers have developed a highly efficient nitrene source
sulfonimidamide. Based on their previous studies, complexes [Tp
*,Br Ag] 2 8 could
catalyze amination/amidation of alkanes (Scheme 12) [34]. In this report, a chiral
sulfonimidamide was used as the nitrene source instead of PhI¼NTs. High
R 2
R 3
R 1 H
R 2
R 3
R 1 NHS*
H
S*HN
S*HN
TsHN
TsHN
[Tp* ,Br Ag] 2 ,8
25%(70%)
30%(75%)
NHTs
10
90
H
H
H
H
H
NHS*
NHS*
NHS*
NHTs
NHTs
NHTs
10
59
31
24(15)
47(68)
29(22)
R
H
R
NHS*
>99% at rt
d.r. = 56/44
NHS*
82%
d.r. = 52/48
>99%
d.r. = 55/45
90%
d.r. = 66/34
R = Ph
R = p-OMeC 6 H 4
R = p-ClC 6 H 4
Substrate
65%(total)
80%(both)
70%(total)
NHTs
n
H
n
n = 1 80%
n = 2 90%
R 2
R 3
R 1 NHTs
[Tp* ,Br Ag] 2 ,8
PhI=NTs
neat alkanes
Yield/Distribution of products (%)
alkanes
5 equiv (30 equiv)
S
O
NH 2
TsN
p-Tol
(S)-Sulfonimidamide
75%
PhI(OAc) 2
method A
method B
method A
method B
Scheme 12 Sp
3 C–H bond amination using silver complex 8 as catalyst
126
T. Zhou and Z.-J. Shi
only moderate yields were obtained for inert C–H bond of cyclic alkanes.
In 2008, Dı ´az-Requejo, Pe ´rez, and coworkers developed a new silver-based
catalytic system which proceeded the direct intermolecular amination of alkanes
[33]. This new catalyzed system employed complexes [Tp
*,Br Ag] 2 8 as catalyst and
PhI¼NTs ([Ag]/[PhI¼NTs]¼1/20) as the nitrene source. The reaction was carried
out in neat alkane at 80
C for 4 h. Linear and branched alkanes were converted to
corresponding isomeric mixtures of amides in moderate to excellent yields
(Scheme 12). The amination/amidation was favored at tertiary sites over secondary
and primary sp
3 C–H bonds of alkanes, and only a few examples were observed at
primary sp
3 C–H bonds. The reaction was inhibited when 2,6-di-tert-butyl-4methylphenol (BHT) was present . Chloroalkanes were observed when CCl 4 was
used as solvent. These evidences indicated that the mechanism involved radical
species.
Although good results were observed for amination/amidation of alkanes, the
reaction needed to carry out in neat substrates. In 2013, Dauban, Dı ´az-Requejo,
Pe ´rez, and coworkers have developed a highly efficient nitrene source
sulfonimidamide. Based on their previous studies, complexes [Tp
*,Br Ag] 2 8 could
catalyze amination/amidation of alkanes (Scheme 12) [34]. In this report, a chiral
sulfonimidamide was used as the nitrene source instead of PhI¼NTs. High
R 2
R 3
R 1 H
R 2
R 3
R 1 NHS*
H
S*HN
S*HN
TsHN
TsHN
[Tp* ,Br Ag] 2 ,8
25%(70%)
30%(75%)
NHTs
10
90
H
H
H
H
H
NHS*
NHS*
NHS*
NHTs
NHTs
NHTs
10
59
31
24(15)
47(68)
29(22)
R
H
R
NHS*
>99% at rt
d.r. = 56/44
NHS*
82%
d.r. = 52/48
>99%
d.r. = 55/45
90%
d.r. = 66/34
R = Ph
R = p-OMeC 6 H 4
R = p-ClC 6 H 4
Substrate
65%(total)
80%(both)
70%(total)
NHTs
n
H
n
n = 1 80%
n = 2 90%
R 2
R 3
R 1 NHTs
[Tp* ,Br Ag] 2 ,8
PhI=NTs
neat alkanes
Yield/Distribution of products (%)
alkanes
5 equiv (30 equiv)
S
O
NH 2
TsN
p-Tol
(S)-Sulfonimidamide
75%
PhI(OAc) 2
method A
method B
method A
method B
Scheme 12 Sp
3 C–H bond amination using silver complex 8 as catalyst
126
T. Zhou and Z.-J. Shi