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O
Pd(P
t
Bu
3
)
2
(2 mol% )
Mo(CO)
6
,NEt
3
CH
3
CN, RT
I
4 examples
68-9 2%
R'
R'
R
R
O
I
Pd(P
t
Bu
3
)
2
CO (1bar), THF
DABCO, RT
Ph
Ph
O
2
N
O
2
N
64%
Scheme 10.33 Pd-catalysed carbonylative Sonogashira coupling reaction with
Mo(CO)
6
as CO source.
O
I
Pd/C, NEt
3
CO (20 bar)
Toluene, 130 °C
10 examples
63-9 7%
R'
R'
R
R
Scheme 10.34 Pd/C-catalysed carbonylative Sonogashira reaction of aryl iodides.
O
I
Pd/Fe
3
O
4
,NEt
3
CO (20 bar)
Toluene, 130 °C
15 examples
50-9 5%
R'
R'
R
R
Scheme 10.35 Pd/Fe
3
O
4
-catalysed carbonylative Sonogashira coupling of aryl
iodides.
good to excellent yields (Scheme 10.33). Again, a one-pot synthesis of pyr-
azoles via condensation of corresponding alkynones with hydrazine was also
conducted and the corresponding products were obtained in good yields at
room temperature.
In 2008, Xia and co-workers reported a recyclable phosphine-free catalyst
system for alkynone synthesis.
44
Using palladium on charcoal (Pd/C) and
NEt
3
, the carbonylative Sonogashira coupling of aryl iodides with alkynes
was carried out smoothly and the desired products were isolated in mod-
erate to excellent yields (Scheme 10.34).
Later on, the same group presented an unusual variation of the palladium-
catalysed carbonylative Sonogashira coupling reaction.
45
Here, a magnetic-
ally separable palladium catalyst was synthesized by combining palladium
nanoparticles and superparamagnetic Fe
3
O
4
nanoparticles in KBH
4
solution.
This catalyst proved to be ecient for the carbonylation reaction of aryl
iodides with alkynes under phosphine-free conditions. Because of the
magnetic behaviour of Fe
3
O
4
, the catalyst could be reused with sustained
selectivity and activity. Various alkynones were synthesized in good to ex-
cellent yields (Scheme 10.35).
Another approach applying a heterogeneous palladium catalyst was re-
ported by Cai and co-workers, who described an MCM-41-supported
bidentate
phosphine-palladium complex
[MCM-41-2p-Pd(0)]
as
a
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