Chemistry Reference
In-Depth Information
1) Pd(OAc)
2
(5 mol%)
ligand
D
(20 mol%)
K
2
CO
3
,toluene,110°C
X
R
1
R
1
+
R
2
N
2) Pd/carbon, HCOONH
4
MeOH, rt
R
2
N
O
H
N
X
N
R
1
+
R
2
R
1
N
H
N
R
2
1) Pd(OAc)
2
(5 mol%)
ligand
D
(15 mol%)
CuCN (0-10 mol%
K
2
CO
3
,dioxane,110°C
O
R
1
R
1
N
X
N
+
R
2
N
2) Pd/carbon, HCOONH
4
MeOH, rt
R
2
N
O
H
R
1
R
1
X
N
N
+
R
2
N
N
O
R
2
H
Me
Me
Me
Me
X=Cl,Br,I
Me
Me
P
Me
D
HBF
4
Scheme 12.27 Pd-catalyzed direct
arylation of different p-electron-deficient
heterocycles.
N
O
Ar
ArBr
(P
t
Bu
3
)
2
Pd
0
(P
t
Bu
3
)
2
Pd
II
(Ar)Br
path a
K
2
HCO
3
K
2
CO
3
KBr
MeCO
2
K
Pd
II
dimer
N
O
Pd(P
t
Bu
3
)Ar
Ar
path b
t
Bu
3
P
Pd
O
AcOH
O
Me
N
O
N
t
Bu
3
P
Pd
II
O
H
O
O
Me
CMD
Figure 12.10 Proposed mechanism for direct arylation of different p-electron-de-
ficient heterocycles.
step in this process, CMD, suggested by Fagnou and co-workers has attracted
significant attention in the succeeding literature.
The direct C-H functionalization of the pyridine ring is problematic be-
cause of two distinct factors: pyridines are electronically deactivated and the
pyridine nitrogen competes with the directing group for binding to the metal
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