Chemistry Reference
In-Depth Information
R
1
Y
Y
R
1
R
2
R
2
X
H
Pd
0
L
n
R
1
Y
R
1
R
2
Y
R
2
Pd
H
Pd
H
X
-
O
HO
O
O
Z
Z
R
1
Y
X
-
R
2
R
1
Y
R
2
Pd
H
Pd
H
O
O
O
O
Z
Z
X = Cl, Br; Y = no atom, CR
2
,N-R,O,C=O;Z=
t
Bu, O
-
Figure 12.13 Proposed mechanism.
[Pd
2
(dba)
3
](5mol%)
DavePhos (10 mol%)
R
2
R
2
OR
3
H
R
1
+
R
1
OR
3
CyNLi (1.5 equiv)
toluene, 22-110
°
C
17-72h
X
O
O
Scheme 12.49 b-Arylation of a carboxylic ester.
[Pd(dba-3,5,3',5')
2
]
(2.5 mol%)
NBn
2
NBn
2
DavePhos (10 mol%)
+
R
1
CyNLi (1.5 equiv.)
to luene, 70
CO
2
Me
X
H
CO
2
Me
n
n
R
°
C
Scheme 12.50 Amine-directed long-range aliphatic arylation.
seven-membered rings. Based on computational and experimental studies,
they proposed a general mechanism (Figure 12.13).
On the other hand, a related intermolecular C-C bond reaction through
Pd-catalyzed C
sp
3
-H activation was reported by Baudoin's group. In their first
report in 2010,
77
b-arylation of a carboxylic ester was achieved with the aid of
a strong base (Scheme 12.49). In a subsequent report in 2012,
78
they de-
scribed an amine-directed long-range aliphatic arylation with aryl bromides
(Scheme 12.50).
12.3 Rhodium-Catalyzed Reactions
Despite many recent developments in the field of Rh-catalyzed C-H activa-
tions, this area is far less developed compared with corresponding
Pd-catalyzed reactions. Rh catalysts have a unique mode of reactivity for C-C
bond formation via C-H activation and are typically highly regioselective.
Search WWH ::
Custom Search