Chemistry Reference
In-Depth Information
TABLE 8B.38. Allylic Alkylation of Azlactones
O
Ph
OLi
O
R
N
K
2
CO
3
R
CO
2
Me
NHBoc
OCO
2
Me
Ar
Ar
O
(C
7
H
8
)Mo(CO)
3
,
L43a
, THF, 65°C
CH
3
OH
N
Ar
R
Ph
Entry
Ar
R
Yield (%)
Diast. Ratio
ee (%)
1
Ph
Me
92
97:3
99
2
3 - Thienyl
Me
84
96:4
91
3
2 - Furyl
Me
84
> 98:2
92
4
Ph
Bn
92
> 98:2
96
5
3 - Thienyl
Bn
86
> 98:2
94
6
Ph
MeSCH
2
CH
2
8 6
> 98:2
92
7
Ph
i
- Pr
76
> 98:2
96
TABLE 8B.39. Allylic Alkylation of 4 - Oxazolones
LiO
N
O
O
R
R
R
Ph
O
Ar
OCO
2
Me
+
Ar
N
N
(C
7
H
8
)Mo(CO)
3
,
L43a
,
THF, 65°C
O
O
Ar
b
l
Ph
Ph
Entry
Ar
R
Yield (%)
Ratio
b
/
l
d r
a
ee (%)
a
1
Ph
Me
91
99:1
12:1
> 99
2
2,4 - (MeO)
2
- Ph
Me
82
12:1
18:1
> 99
3
2 - Br - Ph
Me
78
27:1
24:1
99
4
Ph
Bu
86
49:1
9:1
> 99
5
Ph
All
97
8:1
10:1
> 99
6
3 - Thienyl
i
- Bu
89
14:1
10:1
99
7
Ph
i
- Pr
70
5.5:1
20:1
99
a
Selectivity of the major branched isomer.
dr, diastereomeric ratio.
Ko
č
ovský et al. reported on the use of a wide range of silyl enol ethers in their
Mo(II)- and W(II)-catalyzed allylic alkylations (Fig. 8B.28). Although the reactions
were carried out without a chiral ligand, these experiments indicate that these nucleo-
philes might be interesting alternatives to the standard nucleophiles (such as malonates).
The silyl enolethers of aldehydes and ketones in particular are of interest, as they
allow the allylation of nonstabilized enolates [212]. By comparison of silyl enolethers
with phenylethers, they recognized that a wide range of electron-rich aromatics can
