Chemistry Reference
In-Depth Information
OSiMe
3
O
CpCo(C
O
)
2
,
Δ
I
Me
3
Si
SiMe
3
LiNH
2
+
11.38
11.36
11.37
O
O
Δ
electrocyclic
ring opening
Diels-Alder
reaction
Me
3
Si
Me
3
Si
Me
3
Si
Me
3
Si
1
1
3
9
1
1
0
O
O
1. CF
3
CO
2
H
2. Pb(OAc)
4
H
H
Me
3
Si
H
H
H
H
Me
3
Si
11.41
HO
11.42
Scheme 11.16
Cyclotrimerization is not limited to cobalt
23
or nickel.
24
Catalysts based upon various metals including
ruthenium,
25,26
rhodium (Schemes 11.17 and 11.18),
27-32
niobium,
33
titanium,
34
iridium
35
and, Berthelot's
original metal, nickel
36
have been reported. In many cases, the requirement for using a silyated alkyne
as one partner seems to not apply and even acetylene gas itself may be used; interestingly, in the
case of iridium catalysis, the regioselectivity of cycloaddition can be decided by the choice of ligand
(Scheme 11.19).
37
OBn
OBn
H H
(Ph
3
P)
3
RhC
l
O
O
Bn
BnO
Bn
BnO
BnO
BnO
O
O
1
1
.
4
3
1
1
.
4
4
Scheme 11.17
OH
OH
Ph
(Ph
3
P)
3
RhCl
N
Ts
N
Ts
Ph
1
1
.
4
5
1
1
5
Scheme 11.18
