Chemistry Reference
In-Depth Information
TABLE 4.9. Lactam Formation in Cyclic Systems
O
O
O
N
2
Rh(II)-cat.
N
N
N
CH
2
Cl
2
, 40°C
n
n
n
72
73
74
Ratio
ee (%)
Catalyst
n
=
73:74
Yield (%)
Major Product
Rh
2
(5
S
- MEPY)
4
1
99:1
67
97
Rh
2
(4
S
- MEOX)
4
2
26:74
95
98
TABLE 4.10. Intramolecular Cyclization of
α
- Methoxycarbonyl -
α
- Diazoacetamides
O
O
O
R
R
R
N
Rh(II)-cat.
N
CO
2
Me
N
CO
2
Me
CO
2
Me
N
2
CH
2
Cl
2
R'
R'
R'
78
79
80
Yield
(%)
d e
(%)
e e
(%)
Compound
Catalyst
R =
R
′
=
Product
a
Rh
2
(
S
- PTPA)
4
t
- Bu
P h
80
9 4
> 98
74
b
Rh
2
(
S
- PTTL)
4
4 - (NO
2
) P h
P h
79
8 0
> 98
74
c
Rh
2
(
S
- PTTL)
4
4 - (NO
2
)Ph
4 - (OMe)Ph
79
7 2
> 98
81
d
Rh
2
(
S
- PTTL)
4
4 - (NO
2
)Ph
4 - (NO
2
)Ph
79
8 1
> 98
73
O
O
Rh
2
(4
S
-MACIM)
4
CH
2
Cl
2
, 40°C
LAH
Me
Me
N
2
N
N
N
Me
H
H
86% yield
96% de
7
5
7
6
7
7
(-)-Heliotridane
Scheme 4.15.
Highly diastereoselective synthesis of (
−
) - heliotridane.
PTPA)
4
as catalyst [124,190]. Up to 74% ee was obtained for this reaction with an excel-
lent 94% yield. However, upon changing the group to a less bulky
p
- methoxyphenyl or
p
-nitrophenyl group, complete selectivity for γ - lactam product
79
was observed
[124,191,192]. The reaction appeared to be somewhat catalyst dependent, and Rh
2
(
S
-
PTTL)
4
performed best overall. Only when R′ was an aryl group was the enantiomeric
