Chemistry Reference
In-Depth Information
Enantioselective copper-catalyzed substitution reactions of propargylic acetates with
amines were reported by van Maarseveen et al. and Nishibayashi et al., respectively
(Scheme 5.23) [28]. The copper-catalyzed propargylic amination of acetate
74
using a
chiral ligand
76
afforded the propargylic amine
75
with 85% ee [28a]. Similar reaction
of
74
catalyzed by copper catalyst derived from ligand
78
gave the corresponding propar-
gylic amine
77
with 85% ee [28b] .
MeO
CuI
Ligand
76
OAc
MeO
O
O
N
HN
+
Ph
Ph
H
2
N
Ph
N
N
i
-Pr
2
NEt
Ph
74
MeOH
Ph
Ph
Ligand
76
75
(97%, 85% ee)
Cl
CuOTf·(C
6
H
6
)
0.5
OAc
MeO
PPh
2
PPh
2
Me
Ligand
78
N
+
MeO
Ph
Me
H
i
-Pr
2
NEt
Ph
74
MeOH
Cl
77
(96%, 85% ee)
Ligand
78
Scheme 5.23.
The dynamic kinetic asymmetric allylic amination of racemic allene acetates through
vinyl-allyl Pd(II) intermediates has been studied [29]. Trost and others reported the
dynamic kinetic asymmetric addition of amines to racemic allenes using Trost's ligand
ent
-
35
(Scheme 5.24) [29a]. Asymmetric addition of
N
- benzylmethylamine to allene
79
with Cs
2
CO
3
afforded allene
80
in 98% yield and 95% ee in the presence of Cs
2
CO
3
and
tetrahexylammonium chloride (THACl).
Pd
2
(dba)
3
·CHCl
3
Ligand
ent
-
35
THACl
BnO
H
BnO
Bn
Me
Bn
H
+
N
Me
OAc
H
Cs
2
CO
3
80
(98%, 95% ee)
79
THF
THACl = tetrahexylammonium chloride
Scheme 5.24.
5.3. AZA - C LAISEN REARRANGEMENT AND RELATED REACTIONS
[3,3]-Sigmatropic rearrangements are the widely used reactions in organic chemistry.
Particularly, the metal-catalyzed aza-Claisen rearrangement, known as the Overman
rearrangement, is attractive as C-N bond-forming reaction [30], which allows us to
