Chemistry Reference
In-Depth Information
[Ir(COD)Cl]
2
Ligand
ent
-
17
N
BnHN
OCO
2
Me
TBD
N
Bn
TBD =
N
H
THF
27
28
(99%, 94% ee)
[Ir(COD)Cl]
2
Ligand
ent
-
17
TBD
N
Bn
N
Bn
+
BnNH
2
+
MeOCO
2
OCO
2
Me
THF
29
30
(76%, >99% ee)
31
trans
:
cis
= 95:5
Scheme 5.9.
O
Ts
H
O
O
H
Ligand
35
O
Pd (0)
O
TsN
C
O
and
or
N
Ts
Ts
Et
3
N
N
In situ
N
O
O
OH
O
Ts
34a
34b
32
O
33
OH
OH
O
O
H
O
NH
HN
O
OH
N
N
Ts
PPh
2
Ph
2
P
(
−
)-Swainsonine
36
(>97% ee)
Ligand
35
Scheme 5.10.
Enantioselective allylic amination has emerged as a powerful tool for the synthesis
of natural products [15a]. Desymetrization of
meso
-compounds led to the development
of novel and effi cient strategies in the total synthesis of natural products as demonstrated
by Trost and others (Scheme 5.10) [15b-d]. The reaction of bis-carbamate
33
, generated
in situ
by reaction of a
meso
- diol
32
with
p
-tosyl isocyanate, provided easy access to
chiral nitrogen-substituted carbocycles
34a
and
34b
[15b]. In this transformation, ligand
35
gave excellent enantioselectivity when Et
3
N was used as a base [15c]. Desymetrization
product
36
served as a key building block for the synthesis of (
−
) - swainsonine, as dem-
onstrated by Blechert and others [15d] .
