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"Catalyst Reservoirs"
L
Br
(CO)
m
Pd
n
L
n
Pd
H
L
ArCHO
+
Base
.
HBr
Pd
L
2
+
L
-
L
ArBr
Pd
L
Base
H
L
L
H
Pd
Pd
O
Br
Ar
Br
Ar
CO
L
Pd
O
Br
H
2
Ar
Figure 2.16 Mechanistic rationale for catalyst stability.
Adapted with permission from A. G. Sergeev, A. Spannenberg and M.
Beller, J. Am. Chem. Soc., 2008, 130, 15549. Copyright 2008 American
Chemical Society.
Neopentylphosphines
t
-Bu
t
-Bu
t
-Bu
t
-Bu
P
t
-Bu
P
P
t
-Bu
t
-Bu
t
-Bu
t
-Bu
DTBNpP
TBDNpP
TNpP
Figure 2.17 Neopentylphosphines studied by Shaughnessy and co-workers.
4-bromoanisole with aniline and morpholine, and DTBNpP outperformed
the other ligands, including P(t-Bu)
3
(Figure 2.18).
The Pd/DTBNpP catalyst system was demonstrated to be effective for a
broad scope of amination reactions of aryl bromides with primary and sec-
ondary amines under mild conditions (r.t.-50 1C) with catalyst loadings of
0.5-1.0 mol%. Aryl chlorides could also be successfully coupled, although
higher temperatures (50-140 1C) with increased catalyst loadings were
required (0.5-5 mol%) for deactivated substrates such as 4-chloroanisole.
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