Co molar ratio of 1:1 in THF was six times faster than with [Co 2 (CO) 8 ] alone.
Conversely, [Ru 3 (CO) 12 ] gives rise to cyclohexanecarbaldehyde in only 3% yield in
similar conditions. The role of the ruthenium has not been clearly elucidated, but it
would be involved in the aldehyde forming step by reacting as a hydride delivering
agent on the acyl cobalt intermediate. Combinations of metal-based catalysts have
been also used for promoting tandem reactions. One such example is the one-pot
preparation of bicyclopentenones reported by Jeong from propargyl malonate and
allylic acetate via a sequence of Tsuji–Trost allylation and Pauson–Khand reaction
promoted by a combination of Pd and Rh catalysts (Scheme 15, Eq. 5) [69]. As in the
case of cooperative dual catalysis, such tandem reaction requires testing a wide range
of combinations to ensure that both catalytic systems are compatible toward each other
and toward the different substrates, intermediates, products, and reagents.
OK
O
O 2 N
+
TfO
1,10-phenantroline (15 mol%)
Tol-Binap (4 mol%)
NMP, 170°C, 24h
[Cu 2 O] (7.5 mol%)
[PdI 2 ] (4,5 mol%)
72% yield
+ CO 2
O 2 N
+ H 2 + CO
CHO
CH 2 OH
+
52% yield
(14% - Co 2 (CO) 8 alone)
(3% - Ru 3 (CO) 12 alone)
[Co 2 (CO) 8 ] (0.125 mol%)
[Ru 3 CO 12 ] (0
.
083 mol%)
THF, 110°C, 4h
40 bar 40 bar
1% yield
PhI + HC CH
[CuI] (1 mol%),
[(PPh 3 ) 3 PdCl 2 ] (0.5 mol%)
Et 2 NH, r.t., 6h
Ph
Ph
85% yield
O
OCH(CF 3 )2
O
O i Pr
O
CN
Me
NC
O i Pr
O
Me
+
[Rh(acac)(CO) 2 ] (1 mol%)
[Pd(Cp)(π-C 3 H 5 )] (1 mol%)
(S,S) - (R,R) - PhTRAP (2 mol%)
THF, -25°C, 5h
+ (CF 3 )2CHOH + CO 2
91% yield
93% ee (R)
(without Rh cat. after 24h)
91% yield 0% ee
(1)
(2)
( 3 )
(4)
[(PPh3)2Pd(Ph)X]
alkynylation of the Pd cat.
HC CH
[CuI]/Et 2 NH
[(PPh3)2Pd(Ph)(
)]
C CH
[NEt 2 H 2 ]X
Pd
P
P
Rh
OC
N C
Me
-
O
O i Pr
16-TS
[Cu]Ar + L 2 Pd(Ar')(OTf)
L 2 Pd(Ar)(Ar')
transmetallation step
[Cu] + X
- + ArCO 2
-
CO 2
decarboxylation
Ph
EtO 2 C
CO 2 Et
+
OAc
O
EtO 2 C
EtO 2 C
Ph
[Pd 2 (dba) 3 ]/CHCl 3 (1.5 mol%)
dppb (3 mol%)
[RhClCO(dppp)] 2 (7 mol%)
BSA (1.2 eq.)
CO (1 atm), toluene
110 °C, 25h
92% yield
Ph
EtO 2 C
EtO 2 C
Pd
Rh
(5)
P
P
Scheme 15 Examples of two-component catalysis
148
E. Bodio et al.
Conversely, [Ru 3 (CO) 12 ] gives rise to cyclohexanecarbaldehyde in only 3% yield in
similar conditions. The role of the ruthenium has not been clearly elucidated, but it
would be involved in the aldehyde forming step by reacting as a hydride delivering
agent on the acyl cobalt intermediate. Combinations of metal-based catalysts have
been also used for promoting tandem reactions. One such example is the one-pot
preparation of bicyclopentenones reported by Jeong from propargyl malonate and
allylic acetate via a sequence of Tsuji–Trost allylation and Pauson–Khand reaction
promoted by a combination of Pd and Rh catalysts (Scheme 15, Eq. 5) [69]. As in the
case of cooperative dual catalysis, such tandem reaction requires testing a wide range
of combinations to ensure that both catalytic systems are compatible toward each other
and toward the different substrates, intermediates, products, and reagents.
OK
O
O 2 N
+
TfO
1,10-phenantroline (15 mol%)
Tol-Binap (4 mol%)
NMP, 170°C, 24h
[Cu 2 O] (7.5 mol%)
[PdI 2 ] (4,5 mol%)
72% yield
+ CO 2
O 2 N
+ H 2 + CO
CHO
CH 2 OH
+
52% yield
(14% - Co 2 (CO) 8 alone)
(3% - Ru 3 (CO) 12 alone)
[Co 2 (CO) 8 ] (0.125 mol%)
[Ru 3 CO 12 ] (0
.
083 mol%)
THF, 110°C, 4h
40 bar 40 bar
1% yield
PhI + HC CH
[CuI] (1 mol%),
[(PPh 3 ) 3 PdCl 2 ] (0.5 mol%)
Et 2 NH, r.t., 6h
Ph
Ph
85% yield
O
OCH(CF 3 )2
O
O i Pr
O
CN
Me
NC
O i Pr
O
Me
+
[Rh(acac)(CO) 2 ] (1 mol%)
[Pd(Cp)(π-C 3 H 5 )] (1 mol%)
(S,S) - (R,R) - PhTRAP (2 mol%)
THF, -25°C, 5h
+ (CF 3 )2CHOH + CO 2
91% yield
93% ee (R)
(without Rh cat. after 24h)
91% yield 0% ee
(1)
(2)
( 3 )
(4)
[(PPh3)2Pd(Ph)X]
alkynylation of the Pd cat.
HC CH
[CuI]/Et 2 NH
[(PPh3)2Pd(Ph)(
)]
C CH
[NEt 2 H 2 ]X
Pd
P
P
Rh
OC
N C
Me
-
O
O i Pr
16-TS
[Cu]Ar + L 2 Pd(Ar')(OTf)
L 2 Pd(Ar)(Ar')
transmetallation step
[Cu] + X
- + ArCO 2
-
CO 2
decarboxylation
Ph
EtO 2 C
CO 2 Et
+
OAc
O
EtO 2 C
EtO 2 C
Ph
[Pd 2 (dba) 3 ]/CHCl 3 (1.5 mol%)
dppb (3 mol%)
[RhClCO(dppp)] 2 (7 mol%)
BSA (1.2 eq.)
CO (1 atm), toluene
110 °C, 25h
92% yield
Ph
EtO 2 C
EtO 2 C
Pd
Rh
(5)
P
P
Scheme 15 Examples of two-component catalysis
148
E. Bodio et al.