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F
F
OAc
F
COOH
F
Pd(OAc)
2,
Cu
2
O
Ag
2
CO
3
DMSO-dioxane
110 °C, 2 h
OA c
F
F
F
F
30%
F
F
Scheme 9.164 Example of decarboxylative arylation by electron-deficient carboxylic
acids.
COOR
1
Pd( OAc)
2
(10 mol%)
SIPr
COOR
1
COOH
HCl (P d:L = 1:1 )
10 mol% base
O
2,
DMF, 120-15 0°C, 10 h
·
R
R
R=2,6-F
2
;2,6-Cl
2
;2-NO
2
-4-OMe; 2-NO
2
-4,5-(OMe)
2
R
1
=Me,
i
-Pr
Scheme 9.165 Decarboxylative arylation using electron-deficient benzoic acids.
COOK
Ph
N
Pd(OAc)
2
(2 mol% )
TA N, C uF
2,
BQ
MS 4A , NMP, 120°C
+
NO
2
NO
2
89%
N
N
TAN
Scheme 9.166 Decarboxylative arylation using o-nitrobenzoate.
of arylpalladium intermediates. Further interesting achievements in this
area revealed that reaction can take place in the presence of a Pd complex
with an electron-rich heterocyclic carbene ligand under an oxygen atmos-
phere and rather harsh heating (Scheme 9.165). Intriguingly, the reaction
takes place in the absence of a stoichiometric amount of base, thus actually
under conditions of increasing acidity.
434
o-Nitrobenzoates were shown by Goossen and co-workers to arylate
standard olefins (styrenes, acrylates, also N-isopropylacrylamide) in a mul-
ticomponent system including cupric fluoride, benzoquinone, ligand [1,4,5-
triazanaphthalene, TAN (25)] and molecular sieves, in which all components
are important to achieve good yields (Scheme 9.166).
440
A suggestion was made that the role of CuF
2
in this process is different
from just being a terminal stoichiometric oxidant, rather it is involved in
oxidative decarboxylation to give an ArCuX intermediate (an anionic com-
plex is shown in the scheme as the release of fluoride anion in an anhydrous
aprotic medium is extremely unlikely), which is later transmetallated by
Pd(II) and enters the catalytic cycle (Scheme 9.167).
The experimental data and theoretical modelling of reaction path-
ways
437,441
revealed that the transformation of a carboxylate complex into
an arylpalladium intermediate is a concerted process developing a
typical migratory rearrangement (similar to what happens, for example, in
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