Chemistry Reference
In-Depth Information
O
Me
3
NO
O
O
1.
N
2
10.25
2.
Δ
O
(OC)
3
Fe
(OC)
3
Fe
h
ν
, AcOH
1
.
2
1
.
2
10.26
O
OSiMe
3
1. NaOH
2. Me
2
CuLi;
Me
3
SiCl
(OC)
6
Co
2
(OC)
6
Co
2
10.27
10.28
O
O
1. Ce(NH
4
)
2
(NO
3
)
6
2. Hg
2+
, H
3
O
+
KOH, EtOH
H
O
10.29
10.30
Scheme 10.9
AlBr
3
, CO
H
Fe(CO)
3
Fe(CO)
3
O
1
0
.
1
O
1
0
.
2
1
0
.
3
3
Scheme 10.10
Diene complexes can also be decomplexed by treatment with strong Lewis acids (Scheme 10.10). CO
insertion occurs, leading to formation of a cyclopentenone
10.33
.
13
This reaction is, formally, a cycloaddition
of carbon monoxide with a diene, followed by migration of the resulting alkene into conjugation.
The iron complexes show two-fold reactivity. They react with both strong electrophiles and with strong nu-
cleophiles as the iron can stabilize both the cationic and anionic intermediates. While the electron-withdrawing
ironmoiety activates the diene to nucleophilic attack, it deactivates it towards electrophilic attack. Electrophilic
attack is still useful - the iron stabilizes the diene to all the side reactions that could go along with electrophilic
attack, and stabilizes the cationic product.
10.1.1 Electrophilic Attack
A seemingly simple example of electrophilic attack is shown by Friedel-Crafts acylation of the parent
butadiene complex
10.34
(Scheme 10.11).
14
Two products,
10.37
and
10.38
, can be obtained with the acetyl
