Chemistry Reference
In-Depth Information
Ar
Ar
Me
O
O
Me
P
H
Rh
+
*
*
P
Reductive
elimination
*
Ar
Ar
P
Rh
+
Rh
+
O
*
Me
O
P
H
H
A
Ar
Oxidative
cyclization
Rh
+
Allyl
rearrangement
O
H
Scheme 8D.59.
R
[RhCl(diene*)]
2
(2.5 mol %)
MeO
2
C
R
MeO
2
C
Me
AgSbF
6
(10 mol %)
MeO
2
C
Me
MeO
2
C
H
CH
2
Cl
2
, 25
C, 1 h
°
Ph
Ph
Ph
Ph
Ph
Ph
(
S
,
S
)-Bn-bod*
(
S
,
S
)-Ph-bod*
(
S
,
S
)-Ph-bnd*
5% ee (86%)
R = Ph
Me
i
Pr
94% ee (87%)
97% ee (89%)
>99% ee (95%)
35% ee (58%)
Scheme 8D.60.
[95] . (
S
,
S
)-Ph-bod* as a chiral ligand in particular shows the highest performance. In
this catalyst system, a variety of substitution patterns on the alkyne and the 1,3-diene
portions are tolerated to give the cyclic products with high effi ciency.
The chiral diene (
S
,
S
) - Ph - bod * - complex can also be applied to the intermolecular
versions between 1,3-dienes and alkyne to afford the corresponding 1,4-dienes in high
enantioselectivity (Scheme 8D.61 ).
Since the intramolecular [5 + 2] cycloaddition with the Wilkinson catalyst was
reported, a variety of achiral Rh and Ru catalyst systems have been developed over 10
years [96]. Recently, the fi rst asymmetric intramolecular [5 + 2] cycloaddition using a
chiral Rh complex was reported by Wender et al. (Scheme 8D.62) [97]. The use of cat-
ionic [Rh{(
R
) - BINAP}(solvent)]SbF
6
complex in dichloroethane promotes the cycload-
dition of several vinylcyclopropanes (VCPs).
