Chemistry Reference
In-Depth Information
Evans and co-workers reported a regio- and diastereoselective tandem Rh-catalyzed
alkylation/ Pauson-Khand annulation reaction. They employed [RhCl(CO)dppp]
2
as a cat-
alyst to reacted allylic carbonate with the sodium salt of
-branched malonate under a
carbon monoxide atmosphere to furnish the desired cyclopentenones in good yields and
diastereoselectivities (Scheme 7.45).
79
OCO
2
Me
MeO
2
C
MeO
2
C
CO
2
Me
CO
2
Me
5 mol% [RhCl(CO)(dppp)]
2
CO, MeCN, 30
Me
+
+
°
C
Me
Me
CH
2
CNa(CO
2
Me)
2
A
B
88% yield,
A:B
=37:1
[RhCl(CO)(dppp)]
2
CO, MeCN, reflux
MeO
2
C
MeO
2
C
MeO
2
C
MeO
2
C
O
O
+
H
H
Me
Me
A'
B'
87% yield,
A' : B'
=7:1
Scheme 7.45
Rh-catalyzed tandem alkylation/ PK reaction.
The Chung group attempted to utilize a combined chiral Pd(II) and Co/C catalytic system
for the asymmetric allylic alkylation and cascade carbonylative cyclization (Scheme 7.46).
80
MeO
2
C
MeO
2
C
H
MeO
2
C
2.5 mol% [Pd(allyl)Cl]
2
/L*
C
s2
CO
3
,CH
2
Cl
2
,r.t.
MeO
2
C
OAc
+
Me
n
Me
n
Co/C
30 atm CO
130
o
C
L* =
O
O
Me
N
H
N
H
MeO
2
C
MeO
2
C
O
PPh
2
Ph
2
P
H
H
H
n
31-94%
ee
90-97% yield
Scheme 7.46
Tandem alkylation-carbonylative cyclization.
