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NN
Me
[RhCl(cod)]
2
(2 mol%)
KF (4 equiv), ClCH
2
CO
2
Et (4 equiv)
o-
NN
Me
+
NaBPh
4
Ph
xylene, 120 °C, 6h
1
equ
iv
4equiv
92%
N
[RhCl(cod)]
2
(2 mol%)
KF (4 equiv), ClCH
2
CO
2
Et (4 equiv)
o-
N
N
N
+
NaBPh
4
Ph
Ph
xylene, 120 °C, 6h
1equiv
4 equiv
98%
Scheme 12.53 Rh-catalyzed C-H arylation of phenylazoles.
[Rh(OMe)(cod)]
2
(2 mol%)
KF (8 equiv), ClCH
2
CO
2
Et (4 equiv)
o
N
N
+
PhB(OH)
2
N
N
-xylene, 140 °C, 4h, N
2
atm.
Ph
Ph
4 equiv
50%
Scheme 12.54 Rh-catalyzed C-H arylation of azobenzene.
Ar[M]
HCl or CH
3
CO
2
Et
Rh
I
-X
MX
Cl
Rh
I
-Ar
H-Rh
II I
CH
2
CO
2
Et
N
N
Rh
III
Ar
H
ClCH
2
CO
2
Et
Rh
I
-H
N
Ar
Figure 12.14 Proposed mechanism of Rh-catalyzed N-atom-directed C-H arylation.
and an Rh
I
H species. In this pathway, ethyl chloroacetate reacts with the
Rh
I
H species to release HCl or CH
3
CO
2
Et with the regeneration of Rh
I
X
species (Figure 12.14).
82
Notably, KF was used as a promoter in this reaction,
although the exact role remained unclear.
Vogler and Studer described the direct C-H arylation of 2-pyridyl(hetero)-
arenes using stoichiometric 2,2,6,6-tetramethylpiperidine N-oxide (TEMPO)
as oxidant and [RhCl(C
2
H
4
)
2
]
2
as catalyst.
83
In the case of 2-(thiophen-
2-yl)pyridine, C-H arylation was achieved selectively at the C3 position of the
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