68
As a sequential work, they also reported an iron-catalyzed chelation-controlled
oxidative arylation of olefins with organozinc or Grignard reagents (Scheme 3.42)
[90]. In the presence of Fe(acac) 3 and 1-bromo-2-chloroethane,
2- pyridyldimethylvinylsilane reacted with diarylzinc reagents giving the arylation
products in moderate yields. The pyridine directing group played a crucial role in
this process. Notably, this is the first application of iron catalysis for an oxidative
Heck-type reaction, which produces a variety of aryl olefin derivatives with good
control of regioselectivity and stereoselectivity.
3.3.5 Grignard Reagents as Nucleophiles
Although various organometallic reagents can be successfully used as coupling
partners in oxidative C–H/C–C cross-coupling reactions, more reactive Grignard
reagents are rare to be found in such reactions.
X
Y
N
H
R
CF 3 SiMe 3
Cu(OAc) 2 /1,10-Phen
NaOAc, tBuONa
DTBP or air
DCE, 80°C
X
Y
N
CF 3
R
N
O
N
CF 3
O
N
CF 3
O
N
CF 3
N
N
CF 3
MeO 2 C
Me
Ph
Br
81%
88%
58%
57%
N
N
CF 3
S
N
CF 3
N
N
CF 3
CN
CF 3
F
F
F
F
F
32%
74%
30%
93%
Scheme 3.37 Copper-catalyzed oxidative trifluoromethylation of electron-poor heteroarenes
N
H
CF 3 SiMe 3
Cu(OH) 2 /1,10-Phen
Ag 2 CO 3 , KF
DCE, 80°C
R 3
R 2
R 1
N
CF 3
R 3
R 2
R 1
Scheme 3.38 Copper-catalyzed oxidative trifluoromethylation of indoles
C. He