Chemistry Reference
In-Depth Information
O
OMe
Pd(OAc)
2
(2.5 mol %)
K
2
S
2
O
8
DMSO/H
2
O (3:2), rt
O
B(OH)
2
95%
+
HO
O
OMe
Scheme 14.67
O
2
N
Pd(OAc)
2
(2 mol %)
P(
i
-Pr)Ph
2
(6 mol %)
CuCO
3
, KF, 3 Å MS
NMP, 120 °C, 24 h
O
NO
2
Br
+
HO
94%
Scheme 14.68
NO
2
NO
2
O
Pd(O
2
CCF
3
)
2
(5 mol %)
PCy
3
(15 mol %)
Ag
2
CO
3
, DMSO/DME (3:17)
120 °C, 24 h
O
S
S
+
OH
78%
HO
Scheme 14.69
PdCl
2
(5 mol %)
PPh
3
(25 mol %)
H
2
O/DMF (3:1)
170 °C, MW, 8 min
Br
S
S
+
LiO
2
S
86%
NC
NC
Scheme 14.70
derivatives at room temperature in DMSO-water using potassium persulfate
as the oxidant (Scheme 14.67).
199
These decarboxylative reactions are less
attractive than the decarbonylative couplings because they require a stoi-
chiometric oxidant, such as Ag
2
CO
3
or K
2
S
2
O
8
.
Benzoic acids can also be used in place of typical organometallic partners
in cross-coupling reactions with aryl halides. Palladium-catalyzed coupling
of aryl halides with benzoic acids to give biaryls was reported independently
by the groups of Goossen and Wagner (Scheme 14.68).
200
High temperatures
and catalyst loadings are required along with a stoichiometric oxidant.
Heterocyclic acids are also suitable substrates.
201
A combined palladium and
copper catalyst system extended the reaction to aryl chlorides
202
and aryl
sulfonates.
203
Cross-coupling of two different arylcarboxylic acid derivatives is possible if
they are electronically different (Scheme 14.69).
204
Electron-deficient benzoic
acids can be coupled with electron-rich aromatic acid derivatives using
Pd(O
2
CCF
3
)
2
as the catalyst (5 mol%) and Ag
2
CO
3
as the oxidant in DMSO-
DME (3 : 17) at 120 1C. Good yields of the cross-coupled products are ob-
tained. Desulfinylative coupling of heteroarylsulfinates and aryl bromides
catalyzed by palladium occurs effectively in water with a small amount of
DMF (Scheme 14.70).
205
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