Chemistry Reference
In-Depth Information
Tab l e 7 . 1
Rh-catalyzed asymmetric desymmetrization of acetal.
O
Ph
O
Ph
O
Cat*
H
H
+
Ph
O
Condition
O
O
*
*
H
H
Acetal
Conditions
Yield/ee[%]
Yield/ee[%]
A
No Rxn, (acetal decomposition)
B
41/86
25//70
A: [Rh(CO)
2
CI]
2
(3 mol%), (
R)-
BINAP (9 mol%), Ag0Tf (12 mol%), THF, 90
◦
C,CO (1atm)
B: [Rh(CO)
2
CI]
2
(5 mol%), (
R)-
BINAP (12 mol%),cinnamaldehyde (20 eq), 120
◦
C, Ar (1atm)
3 mol% [RhCl(CO)
2
]
2
12 mol% (
R
)-SIPHOS
12 mol% AgSbF
6
Ph
Ph
O
P
NMe
2
O
O
O
O
DCE, 90
°
C, 3 h
*
CO (1 atm)
56% yield
84%
ee
(
R
)-SIPHOS
Scheme 7.9
Asymmetric Rh-catalyzed PKR using (
R
)-SIPHOS as a chiral ligand.
use of metal-carbonyl to attain PKR in the absence of gaseous carbon monoxide.
17, 18
This
hypothesis employed an
in situ
aldehyde decarbonylation process and a subsequent CO
transfer reaction (Scheme 7.10).
Decarbonylation process
Carbonylation process
O
R
H
[M]
O
R
[M]
H
O
CO
-[M]
R
[M]
H
-RH
[M]
CO
[M]
CO
Metal carbonyl
Scheme 7.10
The proposed mechanism of PKR with an aldehyde as CO source.
Morimoto/Kakiuchi
et al.
reported pentafluorobenzaldehyde was an efficient CO
surrogate for the Pauson-Khand-type cyclization, whereas the Shibata group showed
