Chemistry Reference
In-Depth Information
Me
3
-C
3
H
5
)PdCl]
2
,L
*
MeO
2
C
MeO
2
C
Me
[(
η
Co/C
OAc
O
+
30 atm CO
Cs
2
CO
3
, rt, DCM
MeO
2
C
MeO
2
C
n
n=1~3
H
H
H
n
n
Yield (%)
ee (%)
O
O
L*=
NH
HN
1
2
3
92
90
97
94
72
31
PPh
2
Ph
2
P
Scheme 9.24
the yield (Scheme 9.25).
60
This was the three-step one-pot synthesis of [5.5.5.5]fenestranes
from the readily available 1,6-enynes and alkynes as the starting material. Two different
catalysts, cobalt nanoparticles and allyl palladium chloride, were capable of promoting
three sequential but independent catalytic cycles in the desired chronological order, thereby
allowing a new molecular queuing process to take place. This is another example of a
combination of homogeneous and heterogeneous catalysts in a tandem reaction. The in-
triguing interplay of sequential reactions gives the highly funtionalized [5.5.5.5]fenestranes
in high yields. It should be noted, however, that the steric effect of the substituent(s) on the
enyne substrate and alkyne diester is an important factor allowing the Pd-catalyzed allylic
alkylation reaction to proceed. The bulk cobalt on charcoal instead of cobalt nanoparticles
was not effective in the third step. Cobalt nanoparticles were tolerant of virtually all the
reaction conditions and quite effective for both the first and third reactions.
Co NP
3
-C
3
H
5
)PdCl]
2
Dppe, BSA, KOAc
rt, 12 h
O
[(
η
O
MeO
2
C
20 atm CO, THF
130
AcO
°
C, 18 h
R
AcO
MeO
2
C
MeO
2
C
R
MeO
2
C
O
Co NP
MeO
2
C
20 atm CO, THF
130
O
MeO
2
C
°
C, 18 h
R
R
Yield (%)
Me
Ph
84
74
Scheme 9.25
This study might open a number of doors for PKRs and related organic reactions
that could be effectively catalyzed by a combination of homogeneous and heterogeneous
catalysts.
