Chemistry Reference
In-Depth Information
O
PdCl
2
(PPh
3
)
2
-(CuI)
CO (1 bar), THF
aq NH
3
(0.5 M), RT
I
20 examples
47-87%
R"
R"
R
R
Scheme 10.27 Carbonylative room temperature Sonogashira reaction in aqueous
ammonia.
O
PdCl
2
(5 mol%)
PPh
3
(10 mol%)
CO (1 bar), H
2
O
NEt
3
,RT
I
20 examples
46-96%
R"
R"
R
R
Scheme 10.28 Pd-catalysed carbonylative Sonogashira coupling in water.
O
Pd(OAc)
2
,PPh
3
DMAc, 80 °C, CO
I
SbP h
2
5 examples
55-87%
R
R
Scheme 10.29 Pd-catalysed carbonylative Sonogashira coupling of an ethynylsti-
bane with aryl iodides.
good yields using aqueous ammonia as base. Surprisingly, no competitive
amination reaction occurred. This methodology was later exploited by
Bishop et al. to generate pyrazoles.
35c
Water as a green solvent has been applied successfully as the reaction
medium for palladium-catalysed carbonylative Sonogashira reactions
(Scheme 10.28).
36
In addition to alkynes, activated acetylenic stibanes can be
applied as coupling partners in carbonylations. An example is the palladium-
catalysed carbonylative Sonogashira coupling of alkynylstibanes with aryl
iodides published by Kakusawa and Kurita in 2006.
37
The reaction was
carried out under 1 bar of CO in DMAc using 5 mol% of Pd(OAc)
2
and 20
mol% of PPh
3
. Alkynones were obtained in good yields along with a small
amount of non-carbonylative coupling products (Scheme 10.29). However,
this side reaction could be completely suppressed by increasing the CO
pressure to 20 bar.
The use of ionic liquids and flow chemistry technologies are attracting
increasing attention. Consequently, these novel tools were also successfully
applied in carbonylative Sonogashira reactions by Ryu and co-workers.
38
Various alkynones were synthesized in moderate to good yields at low
pressure of CO in n-butylmethylimidazolium hexafluorophosphate. The
microreactor-based flow system was compared with typical batch conditions
and higher yields could be achieved in the former case (Scheme 10.30).
In 2006, Chen and co-workers reported a convenient, effective method for
the carbonylative Sonogashira coupling of aryl iodides with ethynylferrocene
under 1 atm of CO.
39
Various aryl
ferrocenylethynyl ketones were
Search WWH ::
Custom Search