Chemistry Reference
In-Depth Information
10.4 Carbonylative Suzuki Reactions
The palladium-catalysed cross-coupling of organohalides with organobor-
anes is known as the Suzuki reaction and is one of the most popular
coupling reactions. When a Suzuki reaction is performed under an atmos-
phere of CO, one carbonyl group will be inserted into the two coupling
partners (carbonylative Suzuki reaction).
As early as 1986, Kojima and co-workers reported the carbonylative
coupling of aryl iodides or benzyl halides with organoboranes in the
presence of a catalytic amount of palladium catalyst.
59
This was the first
application of organoboranes in carbonylative coupling reactions mediated
by 1.1 equiv. of Zn(acac)
2
to favour the transmetallation. Various ketones
were produced in good yields starting from aryl iodides and benzyl chloride
(Scheme 10.48).
Later, in 1991, Suzuki and co-workers developed another methodology for
the carbonylative coupling of vinyl halides with organoboranes using
Pd(PPh
3
)
4
and K
3
PO
4
as a base to synthesize vinyl ketones in moderate to
excellent yields
60
(Scheme 10.49). However, for iodoalkenes bearing electron-
withdrawing substituents, the chemoselectivity decreased and a mixture of
carbonylated and non-carbonylated products was observed. In the same
year, this methodology was extended to iodoalkanes with the assistance of
light.
61
In 1993, Suzuki and co-workers reported the palladium-catalysed carbo-
nylative coupling of aryl iodides with aryl boronic acids.
62a
Various diaryl
ketones were produced in high yields (Scheme 10.50). The correct choice of
base and solvent was essential to obtain the desired ketones without biaryl
by-products. The coupling of benzyl bromide was also described. In 1998,
the same group extended this methodology to aryl bromides and triflates.
62b
In the case of aryl bromides, NaI or KI was required as an additive.
Ishikura and Terashima described an application of the carbonylative
coupling of organohalides or vinyl triflates in a one-pot procedure using
indolyl borates as coupling partner to achieve indol-2-yl ketones in good
PdCl
2
(PPh
3
)
2
(5 mol%)
PPh
3
(10 mol% )
THF-HMPA (4:1)
CO (1 bar ), 50-55 °C
Zn(acac)
2
(1.1 equi v)
O
10 exa mple s
43-82%
RX
R'
B
R
R'
X=I.Cl
Scheme 10.48 First Pd-catalysed carbonylative coupling of organoboranes.
Pd(PPh
3
)
4
(5 mol%)
benzene/dioxane
CO (1-3 bar), RT
K
3
PO
4
(3 equiv)
O
X
7 examples
48-99%
R
2
RB
R
R
2
R
1
R
1
Scheme 10.49 Pd-catalysed carbonylative Suzuki coupling of organoboranes with
vinyl halides.
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