Chemistry Reference
In-Depth Information
1. Li, NH
3
2. SmI
2
Co
2
(CO)
8
O
H
O
O
Ph
Ph
7.66
7.67
Me
H
O
H
H
H
7
6
8
7
9
Scheme 7.19
7.3.2 The Hetero-Pauson-Khand Reaction
The alkene component of the Pauson-Khand reaction can be replaced by a carbonyl group, leading to
the formation of butenolides. This reaction has proved useful in butenolide synthesis using molybdenum
complexes with labile ligands. It was used in a short synthesis of an epimer of dihydrocanadensolide
7.76
from aldehyde
7.74
(Scheme 7.21).
44
It was also used in a short synthesis of mintlactone
7.79
from citronellol
7.77
(Scheme 7.22).
45
In an interesting transformation, citronellol
7.77
was de-methylated to the alkynol,
which was oxidized to the aldehyde
7.78
. Carbonylation of the aldehyde
7.78
was achieved using an activated
molybdenum carbonyl species. Another synthesis of mintlactone may be found in scheme 4.43.
Ph
Ph
CO,
catalyst
O
O
O
7.70
H
7.71
O
O
O
PPh
2
PPh
2
catalyst =
or
[(cod)RhCl]
2
or (
S
)-tolBINAP
ent
-
1.38
OC
Ti
CO
7.72
7.73
O
Scheme 7.20
H
n
-Bu
O
1. H
2
, Pd/C
2. RuCl
3
, NaIO
4
Mo(CO)
3
(DMF)
3
O
O
O
O
O
H
O
7
4
7
.
5
7.76
Scheme 7.21
