Chemistry Reference
In-Depth Information
Fe(CO)
3
X = OAc: BF
3.
OEt
2
X = OH: H
+
Fe(CO)
3
X
10.136
10.137
SiMe
3
MeOH
Fe(CO)
3
(OC)
3
Fe
OMe
10.138
10.139
Scheme 10.34
Ph
Ph
PhLi
O
2
O
Fe(CO)
2
PPh
3
Fe(CO)
2
PPh
3
10.140
10.141
10.142
Scheme 10.35
H
H
NaBH
4
+
2:1
Fe(CO)
3
Fe(CO)
3
Fe(CO)
3
10.143
10.144
10.145
Scheme 10.36
Parallel chemistry is observed with the trimethylene methane complexes
10.136
(Scheme 10.34).
45
In this
case, however, the cationic
5
-complex
10.137
, although observable by NMR at low temperature,
46
cannot
be isolated. It could be trapped with nucleophiles, but different nucleophiles gave different types of product.
Allyltrimethylsilane gave a new trimethylene methane complex
10.138
,
47
while methanol yielded an
4
-diene
complex
10.139
. The different structural types produced, trimethylene methane versus diene complex, are
likely to be due to kinetic and thermodynamic control as addition of methanol would be expected to be
reversible under acidic conditions.
With
5
-complexes of different skeletons, nucleophilic attack is not always at the terminal carbon
(Scheme 10.35). The identity of both the ligands and the nucleophile also affects this selectivity
(Scheme 10.36). The products can undergo oxidatively induced CO insertion and reductive elimination to
give interesting products.
48
In other cases, CO insertion has to be forced using high pressure (Scheme 10.37).
Oxidatively induced reductive elimination has also been observed leading to
cis
-1,2-divinyl cyclopropanes
10.152
that undergo a facile [3,3]-sigmatropic shift, especially after ester reduction, to cycloheptadienes
10.154
(Scheme 10.38).
49
