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[Pd(IPent)(PEPPSI)](
4
)
(2 mol%)
X
+
+
R
R
R
PinB
5M KOH
THF, reflux, 24 h
X=Cl,Br
α
-product
γ
-product
OMe
t
Bu
MeOC
X=Br:69%
X=Cl:74%
α/γ
=>99/1
X=Br:81%
α/γ
=97/3
X=Br:42%
α/ γ
=>99/1
X=Br:96%
α/ γ
=>99/1
MeO
OMe
N
N
MeO
N
X=Br:83%
α/γ
=>99/1
X=Br:98%
α/γ
=>99/1
X=Cl:95%
α/γ
=>99/1
Scheme 4.7 Activity of [Pd(IPent)(PEPPSI)]
(4)
in the selective Suzuki reaction
involving allylboronic acids.
BF
4
BF
4
N
N
N
N
N
N
Me s
Pd
Ph
2
Cl
Cl
Pd
Ph
2
Pd
Ph
2
Fe
Fe
Fe
12a
12b
12c
Figure 4.8
Structures of the precatalysts 12a-c for asymmetric Suzuki coupling.
12a
-(
R
)(0.5 mol%)
+
K
2
CO
3,
40°C
toluene, 24 h
Br
B(OH)
2
Yield: 8 8%
ee = 42%
Scheme 4.8 Asymmetric Suzuki coupling for the preparation of chiral binaphthyls.
4.3.1.1.4 Developments of New Well-Defined Precatalysts with New
''Throwaway Ligands''. When using a well-defined precatalyst in cross-
coupling reactions, one of the keys to success is the ease and the speed
with which the precatalyst leads to the formation of the active Pd(0) spe-
cies in the reaction medium. The development of new labile ligands, also
called throwaway ligands, is therefore very important. Among the most not-
able advances, Cazin and co-workers developed a new range of mixed
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