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RSC Advances
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COMMUNICATION
Journal Name
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yield of 2h and diminished yield of 2z were possibly due to the
high electron rich nature of allyloxyphenyl moiety. These
observations are not in support of the generation of radical
species in the present reaction conditions. Next, to probe
insights into the mechanism of copper-catalyzed
trifluoromethylation, 31P NMR and 19F NMR studies were
conducted. Unfortunately, all these studies did not afford any
valuable information about the mechanism (see Supporting
information).
Thus, based on the observation and copper-catalyzed cross-
coupling reaction,20-21 we postulated the following mechanism
for the copper-catalyzed trifluoromethylation of symmetrical
and unsymmetrical diaryl-λ3-iodanes 1/6. The active copper
complex A, generated from Cu(I) and PPh3, on reaction with
TMSCF3 in the presence of KF would form the CF3-bound
copper species B. Formation of copper species C could be
explained through the oxidation of B with diaryl-λ3-iodanes
1/6. Finally, reductive elimination of benzotrifluorides 2 from C
would afford the active copper species A to continue the
catalytic cycle.
4359.
3
4
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TfO
I
R
Ar
[(PPh3)CuCF3]
TMSF
KF
B
1/6
ArI
TMSCF3
PPh3
+
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X = I or OTf
[(PPh3)CuX]
CuI
A
CF3
III
X
R
Cu
Ph3P
R
CF3
C
2
Scheme 6. Plausible mechanism.
In
conclusion,
an
efficient
copper-catalyzed
trifluoromethylation of symmetrical and unsymmetrical diaryl-
λ3-iodanes have been developed for the synthesis of diverse
trifluoromethylated (hetero)arenes in good yield and
regioselectivity. The optimized reaction tolerates various
reactive functional groups like bromo, iodo, cyano, nitro, ester,
ketone and enolizable ketone.
8
Notes and references
‡ We thank Council of Scientific & Industrial Research (CSIR)
(Project No. 02(0092)/12/EMR-II) for financial support and
Department of Science and Technology (DST) (Project No.
SR/S1/OC-48/2012) for sponsoring Gas Chromatography. VKP
thanks CSIR for a fellowship.
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