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NN
Bu
Me
O
Ph
3
P
Pd
Cl
Cl
I
1 mol%
4 examples
72-92%
[BMim]PF
6
,NEt
3
CO (3-5 bar), 120 °C
R
R
Scheme 10.30 Pd-catalysed carbonylative Sonogashira reaction in ionic liquids.
O
I
Pd(P Ph
3
)
4
(4 mol%), CuI
K
2
CO
3
, Toluene, 80 °C
12 examples
62-88%
Fe
R
R
Scheme 10.31 Pd-catalysed carbonylative Sonogashira coupling of ethynylferrocene
with aryl iodides.
O
I
PdCl
2
(P(OPh)
3
)
2
NEt
3
, Tolu ene
CO (1 bar), 80 °C
7 examples
24 -76%
R
R'
R'
R
Scheme 10.32 PdCl
2
[P(OPh)
3
]
2
-catalysed carbonylative Sonogashira coupling of aryl
iodides with alkynes.
synthesized in 62-88% yield (Scheme 10.31). Unexpectedly, strongly acti-
vated aryl iodides (4-Ac, 4-NO
2
) and iodopyridine gave no desired carbony-
lation product. However, this methodology was also applied for a two-step
synthesis of ferrocenylpyrazole and pyrimidine derivatives by Skoda-Foldes
and co-workers.
40
In 2009, Chen's group also reported another protocol for
the synthesis of ferrocenylethynyl ketones in water.
41
The use of phosphites, e.g. P(OPh)
3
, as ligands in palladium-catalysed
carbonylative Sonogashira coupling reactions was first reported by Trzeciak
and co-workers.
42
Using the defined complex PdCl
2
[P(OPh)
3
]
2
as catalyst,
alkynones were produced in low to moderate yields at 1 bar of CO
(Scheme 10.32). When the reaction was conducted in an ionic liquid, the
catalyst could be reused in four consecutive catalytic runs with high activity.
Notably, benzyl bromide was reported as substrate for the first time, but 2
equiv. of the acetylene were required in this system.
Iizuka and Kondo presented a palladium-catalysed ''CO-free'' method for
the synthesis of alkynones, which applied stoichiometric amounts of
Mo(CO)
6
as CO source.
43
The reaction was carried out at room temperature
and PtBu
3
was found to be an essential ligand under these conditions. When
strongly electron-withdrawing substituted aryl iodides were employed as
substrates in this protocol, the corresponding alkynones were produced in
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