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Pd(OAc)
2
(2 mol %)
5 % XPhos, Cs
2
CO
3
t
Bu
SO
2
Ph
NH
t
Bu
N
toluene/t-BuOH (5:1)
90 °C
98 %
O
OTs
Pd(OAc)
2
(2 mol %)
5 % XPhos, K
2
CO
3
O
HN
Ph
t-BuOH, 110 °C
95 %
H
2
N
Ph
Pd
2
(dba)
3
(0.5 mol %)
2 % XPhos, KOH
H
N
Cl
H
2
N
Ph
Ph
H
2
O, 110 °C
93 %
N
N
Figure 2.46 Challenging C-N cross-coupling reactions using Pd/XPhos.
Pd
2
(dba)
3
(1.5 mol %)
SPhos (6 mol %)
K
3
PO
4
Ph
i
-Pr
i
-Pr
(HO)
2
B
Br
toluene, 100 °C
93 %
Ph
i
-Pr
i
-Pr
i
-Pr
i
-Pr
Figure 2.47 Highly hindered biaryl formation via Suzuki-Miyaura coupling using
Pd/SPhos.
Cy
Cy
Ph
P
Pd
Ph
MeO
O
OMe
Figure 2.48 X-ray structure of (SPhos)Pd(dba) with hydrogens removed for clarity
(dba
¼
dibenzylideneacetone).
Reprinted with permission from T. E. Barder, S. D. Walker, J. R.
Martinelli and S. L. Buchwald, J. Am. Chem. Soc., 2005, 127, 4685.
Copyright 2005 American Chemical Society.
and Pd(II) oxidative addition intermediates, but not at the amine-bound
Pd(II) intermediate. The following mechanism was proposed in which the
palladium is being transferred between the two cycles via ligand exchange at
the above-mentioned intermediates (Figure 2.50).
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