Chemistry Reference
In-Depth Information
Free amine
Free alcohol
OH
NH
3
Cl
O
1) [Ir(COD)Cl]
2
Ligand
24
DMF
P
N
+ H
3
NSO
3
O
22
21
2) HCl, Et
2
O
23
(70%, 70% ee)
Ligand
24
NH
3
eMM
eMM
N
Ir
L
N
HSO
3
[Ir(COD)Cl]
2
DMF
21
H
3
NSO
3
22
OH
O
S
H
OO
O
NH
3
DMF
Scheme 5.7.
The iridium-catalyzed regio- and enantioselective decarboxylative allylic amidation
reaction of substituted allyl benzyl imidodicarbonates was reported by Singh and
Han (Scheme 5.8) [13]. The reaction of cinnamyl benzyl imidodicarbonate
25
using
ligand
ent
-
17
proceeded smoothly in the presence of DBU and proton sponge
(PS; 1,8-bis(dimethylamino)naphthalene) [13a]. Both DBU and PS were found to be
necessary for the reaction, since the reaction did not proceed to completion in the
absence of either. Additionally, the result of a crossover experiment was more consistent
with the reaction mechanisms involving the Ir-
π
- allylic intermediate over intramolecular
[3,3] - rearrangement.
O
[Ir(COD)Cl]
2
Ligand
ent
-
17
Cbz
Ir
L
[Ir(COD)Cl]
2
Cbz
H
O
HN
25
Ph
DBU, PS
Ph
Ph
THF
π
-Allyl intermediate
25
26
(>99% ee)
Conversion (100%)
Regioselectivity (>99:1)
Scheme 5.8.
Allylic amination is important for the synthesis of nitrogen-containing heterocycles.
Takemoto, Miyabe, and others reported a novel method for preparing azacycles based
on the sequential iridium-catalyzed allylic amination [14]. The enantioselective intermo-
lecular reaction of
27
by using the iridium complex was studied by Helmchen and others
(Scheme 5.9) [9b,c]. The reaction proceeded smoothly in the presence of base. The good
enantioselectivity was obtained upon activation with 1,5,7-triazabicyclo[4.4.0]undec-
5-ene (TBD) as base to give the cyclic product
28
in 99% yield and 94% ee. Sequential
aminations of bis-allylic carbonate
29
, involving an inter- followed by an intramolecular
reaction, gave
trans
- azacycle
30
with
>
99% ee.
