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In-Depth Information
F
F
Pd(OAc)
2
(5 m ol%)
MePhos (10 mol%)
Ag
2
CO
3
, K
2
CO
3
EtOAc/H
2
O (2.5:1)
rt, 16 h
F
F
H
F
I
+
F
F
F
F
95%
F
Scheme 14.73
Pd(OAc)
2
(10 m ol %)
dcpe (5 mol %)
CuCO
3
, 4 Å MS
dioxane/DMSO (9:1)
140 °C, 16 h
O
S
O
Ph
CO
2
H
S
+
Ph
CO
2
Et
N
N
N
N
CO
2
Et
80%
Scheme 14.74
BocN
BocN
Ni(cod)
2
(20 mol %)
dcpe (40 mol %)
K
3
PO
4
, dioxane
165 °C
MeO
2
C
MeO
2
C
O
N
N
N
N
+
O
O
PhO
O
36%
O
HN
muscoride A
O
steps
O
N
N
N
O
O
O
Scheme 14.75
The accelerating effect of water was attributed to dissolution of the inorganic
reactants (Ag
2
CO
3
and K
2
CO
3
).
Benzoic acid derivatives have also been used as coupling partners in the
direct arylation of arenes. 2-Substituted oxazole- and thiazolecarboxylic acids
undergo decarboxylative coupling with oxazoles to give biazoles in good
yields using Pd(OAc)
2
/dcpe [dcpe
¼
1,2-bis(dicyclohexylphosphino)ethane]
(Scheme 14.74).
212
Under optimized conditions, a 10 : 1 ratio of cross-coupled
to homo-coupled product was obtained. 2-Substituted benzoic acid derivatives
were used to arylate tetra- and pentafluorobenzene derivatives using
Pd(O
2
CCF
3
)
2
/PCy
3
in the presence of Ag
2
CO
3
.
213
Phenyl esters were effective
substrates for the 2-arylation of oxazoles catalyzed by Ni(COD)
2
/dcpe.
214
This
transformation was used as a key step in the synthesis of the natural product
muscoride A (Scheme 14.75).
14.6 Conclusion and Future Prospects
The development of more environmentally sustainable approaches to cross-
coupling catalysis represents an important area of future development in
these incredibly powerful reactions. To date, significant effort has been
devoted to developing solvent replacements, particularly the use of water in
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