Chemistry Reference
In-Depth Information
W(CO)
5
.THF
O
7
.
4
7
.
5
Scheme 7.15
Et
Et
EtO
2
C
EtO
2
C
Ru
3
(CO)
12
, CO
O
EtO
2
C
EtO
2
C
7.57
7.56
Scheme 7.16
(OC)
3
Fe
Fe(CO)
5
, CO
O
7
.
8
7
.
9
Scheme 7.17
•
1. K
2
CO
3
, MeOH
2. PhSH, MgBr
2
3. Br
2
,
OMOM
OMOM
[(cod)RhCl]
2
dppp, CO
O
OEt
OPiv
OPiv
7.60
7.61
H
1. AIBN,
n
-Bu
3
SnH
2. CrO
3
, H
3
O
+
3. H
2
, Pd/C
H
O
O
OEt
O
O
O
H
Br
7.62
7.63
H
H
H
H
1. NaBH
4
, CeCl
3
2. TBSCl, C
3
H
4
N
2
3. LDA, H
2
C=O
O
O
PCC
TBSO
O
O
O
H
H
7.64
7.65
Scheme 7.18
7.3.1 Asymmetric Pauson-Khand Reaction
Asymmetric variants of the Pauson-Khand reaction have been explored employing chiral auxiliaries. At-
tachment of a chiral auxiliary to the alkene moiety gave good stereochemical induction (Scheme 7.19). This
chemistry was used in a formal synthesis of hirsutene
7.69
.
39
Chiral auxiliaries can also be attached to the
alkyne moiety.
40
Chiral catalysts have also been used with good results (Scheme 7.20). These include chiral titanocene
complexes
7.70
,
41
as well as complexes of rhodium
42
and iridium
43
with chiral phosphines.
