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Z
R
Z
Pd
+
Pd
+
Ar
ArP d
+
R
H
Z
H
Z
Ar
H
base
R
H
Ar
R
HP d
+
Z
Ar
H
H
R
HPd
+
Z
H
H
Z
Z
Pd
+
Pd
+
R
Ar
Ar
R
Ar
R
Scheme 9.88 Mechanistic rationale for stereoselectivity.
N
2
BF
4
COOR
Pd(OA c)
2
(10 mol %)
bmim-BF
4,
70-80°C, 11-14 h
+
R
1
R
2
R
2
R
1
,R
2
=o-Me,F,NO
2,
NHCO
2
Me; m-Cl;
p-OMe, Cl, Br, CF
3
; 3,4-Me, O Me, Cl; etc.
R=Me,Et
CO OR
R
1
Scheme 9.89
Stereoselective synthesis of b,b-diaryl acrylates.
F
N
2
BF
4
CO
2
Me
Pd (OAc)
2
or Pd
2
(dba)
3
(10 mol% Pd)
bmimX, 65°C, 1 h
+
CO
2
Me
N
CO
2
Ph
F
N
CO
2
Ph
X=PF
6,
NTf
2
8 3-91%
Scheme 9.90 Base-free arylation of cyclic allylic amides.
the base-free mode; the addition of base, even NaOAc commonly used in
other protocols involving diazonium salts, suppressed the arylation
(Scheme 9.90).
283
The base-free arylation of 1-acyl-2-trifluoromethylethylenes was shown by
Konno et al. to give the products in which the incoming aryl selectively went
to the b-position relative to the CF
3
group and not to acyl, as might be ex-
pected.
284
The reactions were performed either in the presence of phosphine
ligand or in a phosphine-free mode (in THF in place of ethanol). With some
substrate pairs the former gave better results and with some other substrate
pairs the latter, with a common trend that phosphine-free reactions gave
lower stereoselectivity (Scheme 9.91).
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