Chemistry Reference
In-Depth Information
OH
OH
OH
OH
H
Ph
Ph
Ph
H
H
Ph
H
C
o
2
(CO)
8
Co
2
(CO)
8
(72 %)
(76 %)
(OC)
3
Co
Co(CO)
3
(OC)
3
Co
Co(CO)
3
54a
53a
53b
54b
aorb
aorb
OH
OH
OH
OH
H
Ph
Ph
H
Ph
H
H
Ph
Ph
3
P(OC)
2
Co
Co(CO)
3
Ph
3
P(OC)
2
Co
Co(CO)
3
(OC)
3
Co
Co(CO)
2
PPh
3
(OC)
3
Co
Co(CO)
2
PPh
3
55a
56a
56b
55b
c
c
c
c
H
O
O
H
Ph
Ph
Ph
Ph
HO
HO
HO
HO
H
H
H
H
H
H
H
H
O
H
H
O
57a
58a
57b
58b
a) NMO, PPh
3
,THF,-60°C;98%(51:49
3a
:
4a
) from complex
2a
;95%(50:50
3b
:
4b
) from complex
2b
;b)BNO,PPh
3
,
-59 °C; 66 % (70:30
3a
:
4a
), from complex
2a
;77%(49:51
3b
:
4b
)fromcomplex
2b
; c) norbornene, NMO, DCM, rt.; 77 %
for
5a
,40%for
6a
,69%for
5b
,58%for
6b
.
Scheme 4.14
Asymmetric Pauson-Khand reactions via optically pure alkyne-Co
2
(CO)
5
PPh
3
complexes.
In 2002, Areces
et al.
reported a new synthesis of enantiomerically pure 3-
azabicyclo[3.3.0]octen-7-one derivatives
61-63
via intramolecular PK cycloaddition
using a sugar moiety as the chiral template (Scheme 4.15).
16
As starting materials, aza-
enynes
60a-c
were prepared from aldehyde
59
, which is easily accessible from tri-O-actyl-
D-glucal
R
N
CHO
R
N
O
R
N
O
(
i) Co
2
(CO)
8
(ii) NMO
H
+
H
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
OAc
59
60a
(R = Tosyl)
60b
(R = COCH
3
)
60c
(R = Boc)
61a
(R = Tosyl)
62a
(R = COCH
3
)
63a
(R = Boc)
61b
(R = Tosyl)
62b
(R = COCH
3
)
63b
(R = Boc)
Scheme 4.15
Synthesis of enantiomerically pure 3-azabicyclo[3.3.0]octen-7-one derivatives.
The intramolecular PK reactions of
60a-c
afforded the corresponding 3-
azabicyclo[3.3.0]octen-7-one derivatives,
61-63
, in good yields (47-60%) as 1:1
mixtures of their diastereomers, which were separated via column chromatography
followed by crystallization. Three years later, a more detailed synthesis of enantiomerically
