Chemistry Reference
In-Depth Information
Co
2
(CO)
6
OH
TsN
R
1
R
1
(10 mol%)
R
2
Z
ZO
DME, 70 °C, CO (1 atm)
( )
( )
n
n
R
2
Z = C(CO
2
Et)
2
, R
1
= H, R
2
= H (n = 1): 78%
Z = C(CO
2
Me)
2
, R
1
= H, R
2
= Me (n = 1): 84%
Without CyNH
2
Z = C(CO
2
Et)
2
, R
1
= H, R
2
= H (n = 2): 81%
Z = NTs, R
1
= H, R
2
= H (n = 1): 94%
Z = CHCH
2
OTBS, R
1
= H, R
2
= H (n = 1): 81%
With CyNH
2
(20 mol%)
Scheme 3.21
3.6 Catalytic Reaction Using Multinuclear Cobalt Carbonyl Catalysts
The problem for catalytic reactions using Co
2
(CO)
8
is the formation of a stable and inactive
oligomeric complex. Chung used stable tetrametallic complex Co
4
(CO)
12
as a catalyst,
which would
in situ
be transformed to active dimetallic complex (Scheme 3.22).
22
Although
the harsh reaction conditions of the high temperature (150
◦
C) and high pressure of carbon
monoxide (10 atm) were required, just 0.5-1 mol% o the catalyst realized a high yield both
in inter- and intramolecular reactions.
O
R
R
Co
4
(CO)
12
(0.5 mol%)
+
CH
2
Cl
2
, 150 °C
CO (10 atm)
With norbornadiene
R = Ph: 97%
R = n-C
4
H
9
: 98%
R = (CH
2
)
3
Cl: 71%
R = cyclohex-1-enyl: 75%
R = CH
2
OH: 80%
With norbornene
R = Ph: 93%
R = n-C
4
H
9
: 100%
Co
4
(CO)
12
(1 mol%)
Z
Z
O
CH
2
Cl
2
, 150 °C
CO (10 atm)
Z = CO
2
Et: 92%
Z = NTs: 87%
Scheme 3.22
3
-CH) as a stable catalyst, which can be recog-
nized as the carbon-analogue of Co
4
(CO)
12
.
23
Sugihara used tri-nuclear Co
3
(CO)
9
(
The reaction conditions were a little milder
