Trifluoroethylation of Alkynes: Synthesis of Allylic-CF3 Compounds by Visible-Light Photocatalysis

Article abstract of DOI:10.1002/cjoc.201500919

Two types of allylic trifluoromethylated compounds were synthesized by reacting alkynes with CF₃CH₂I using visible-light photocatalysis. Subtle differences in the catalytic system controlled the selectivity of iodotrifluoroethylation

Full text of DOI:10.1002/cjoc.201500919

COMMUNICATION
DOI: 10.1002/cjoc.201500919
Trifluoroethylation of Alkynes: Synthesis of Allylic-CF3
Compounds by Visible-Light Photocatalysis
a
b
,a
,
Geum-bee Roh Naeem Iqbal, and Eun Jin Cho*
a
Department of Chemistry, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 06974, Republic of Korea
b
Department of Applied Chemistry, Hanyang University, 55 Hanyangdaehak-ro, Sangnok-gu, Ansan,
Gyeonggi-do 15588, Republic of Korea
3 2
Two types of allylic trifluoromethylated compounds were synthesized by reacting alkynes with CF CH I using
visible-light photocatalysis. Subtle differences in the catalytic system controlled the selectivity of iodotrifluoroethy-
lation and hydrotrifluoroethylation. The iodotrifluoroethylated products were obtained in the presence of
[
Ru(bpy) ]Cl and TMEDA in CH CN under visible-light irradiation, whereas hydrotrifluoroethylated products
3 2 3
were synthesized using fac-[Ir(ppy) ] and a mixture of DBU and K CO in DMF. The iodotrifluoroethylation reac-
3
2
3
tion worked particularly well, even at gram-scale, and the synthetic utility of iodotrifluoroethylated products was
proved by their coupling reactions, providing complex CF -containing products.
3
Keywords trifluoroethylation, alkyne, visible-light, photocatalysis
[
6]
Introduction
only one example with alkene and one example with
[
7]
alkyne have been reported (Figure 1b).
Herein, we have developed a mild, efficient, and se-
lective method for the synthesis of allylic CF com-
Trifluoromethylated organic molecules have gained
considerable attention, especially in pharmaceuticals
and agrochemicals, because the introduction of a CF
3
3
pounds from alkynes using 1,1,1-trifluoro-2-iodoethane
group to a molecule can change its physical, chemical,
and biological properties, leading to higher biological
stability, bioavailability, lipophilicity, and binding se-
(
CF CH I) as the trifluoroethyl source by visible-light
3 2
[8,9]
photocatalysis [Figure 1(2)].
The choice of the base
[1]
and photocatalyst is crucial to control the selectivity of
two different types of products in the reactions of al-
The mechanistic pathway for the synthesis
of allylic CF products involves the initial visible-light-
photocatalyzed formation of a •CH CF radical, which
is added to the alkyne, forming the allylic CF radical
intermediate 1'. Depending on the presence of a base,
the reaction may proceed either by radical propagation
lectivity. Because of the natural scarcity of CF
pounds and the enhancement of biological properties by
introducing a CF group, new and efficient synthetic
methods for trifluoromethylation are in demand.
3
com-
[4m,10]
kynes.
3
[
2]
3
A
2
3
plethora of metal-catalyzed, nucleophilic, electrophilic,
and radical reactions have been developed for the in-
corporation of CF
3
[
6]
[
3,4]
3
groups.
However, these studies
2
mainly focused on the construction of a C(sp )－CF
3
3
with CF CH I or by hydrogen-atom abstraction, pro-
ducing iodo- (2) or hydrotrifluoroethylated (3) products,
bond; C(sp )－CF
studied. One of the methods for forming C(sp )－CF
bonds is by synthesizing allylic CF compounds. In gen-
eral, allylic CF compounds have been obtained from
3
bond formation has been rarely
3
2
3
3
respectively [Figure 1(2)].
3
3
alkenes, mainly by allylic C－H activation with trifluo-
Experimental
romethyl sources such as Togni’s and Umemoto’s rea-
[
5]
Procedure for iodotrifluoroethylation
gents in the presence of Cu catalysts [Figure 1(1a)].
However, the requirement of an allylic C－H bond has
led to a limited substrate scope for allylic trifluoro-
methylations despite the efficiency of the reaction. Tri-
fluoroethyl sources such as trifluoroethyl halides are
An oven-dried 50 mL round bottom flask equipped
with a magnetic stir bar was charged with 2－3 mol%
[Ru(bpy) ]Cl (0.02 mmol, 15 mg) in CH CN (5 mL).
3 2 3
Alkyne 1 (1 mmol), 1,1,1-trifluoro-2-iodoethane (3
mmol, 296 μL for aliphatic alkyne and 4 mmol, 394 μL
for aromatic alkyne), and TMEDA (2 mmol, 299 μL)
were added. The round bottom flask was closed with a
alternative substrates for the synthesis of allylic CF
3
compounds from both alkenes and alkynes. However,
trifluoroethylation has not been widely explored, and
*
E-mail: ejcho@cau.ac.kr
Received December 31, 2015; accepted February 3, 2016; published online March 14, 2016.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201500919 or from the author.
Chin. J. Chem. 2016, 34, 459—464
© 2016 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
459

Roh, lqbal & Cho
COMMUNICATION
(
1) Previous Work
a) with -CF3 source
Togni's or Umemoto's
Results and Discussion
First, the reaction was carried out using phenylace-
tylene 1a as the starting material and CF CH I as the
CH CF radical source. To our delight, a high yield of
3
2
cat. Curef.5
+
R
R
CF3
2
3
iodotrifluoroethylated product 2a was obtained using
CF3
CF3
CF3
O
I
O
I
various Ru and Ir photocatalysts in CH CN and
3
S
O
+
TMEDA as the base under blue LED irradiation for 12 h.
Among the catalysts including [Ru(bpy) ]Cl ,
3
2
[
[
Ru(phen) ]Cl , fac-Ir(ppy)3, fac-Ir(dFppy)3, and
Ir(dtbbpy)(ppy) ]PF , [Ru(bpy) ]Cl was selected for
2 6 3 2
3 2
Togni's reagents
Umemoto's reagent
further studies on iodotrifluoroethylation because of the
highest yield and low cost (Table 1, Entries 1－5). The
use of 4 equiv. CF CH I increased the yield of the prod-
b) with -CH CF source
2
3
cat. Coref.6
flow chem)
visible-light
(
3
2
R
+
I
CF3
R
R
CF3
uct, whereas a mixture of products was formed with a
less amount (Table 1, Entries 6 and 7). Although the
reactivity was similar, the use of 3 mol% [Ru(bpy) ]Cl
photocatalysis
R'
ref.7
3
2
Na S O
2 4
2
+
X
CF3
increased the reproducibility of the results (Table 1, En-
try 8). Acetonitrile was found to be the best solvent
CF3
R
X = I, Br
R' = H or I
(
Table 1, Entries 8－10).
(
2) This work
Interestingly, when the catalyst was changed from
Ru(bpy) ]Cl to fac-Ir(ppy) in DMF, the yield of hy-
I
I-abstraction
[
3
2
3
R
CF3
CF3
drotrifluoroethylated product 3a increased (Table 1,
Entry 11); the results prompted us to optimize the con-
ditions for hydrotrifluoroethylation. The choice of base
was crucial for the selectivity, because the base func-
tions not only as an electron donor in the photocatalysis,
but also as a hydrogen-atom source. Consistent with our
2
I
CF3
R
R
visible-light
photocatalysis
1
1'
CF3
H
R
H-abstraction
3
[
4m]
previous reports on trifluoromethylation
fluoroalkylation,
and di-
Figure 1 Synthesis of allylic-CF compounds.
[10]
3
the use of DBU resulted in the
highest yield of 3a among several bases (Table 1, En-
tries 11－15). Despite the selective hydrotrifluoroethy-
lation with K CO , the reaction showed a lower conver-
rubber cap, placed under blue LEDs (7 W), and stirred
at room temperature for 12 h. The progress of the reac-
tion was monitored by TLC and gas chromatography.
The flask was opened, and the reaction mixture was
diluted with dichloromethane. After the aqueous
work-up, the organic layers were combined, dried over
2
3
sion and yield (Table 1, Entry 14). Based on these ob-
servations, we tried the use of a combination of K CO
and DBU, which further increased the yield of 3a (Table
, Entry 16). The use of 2 equiv. K CO and 4 equiv.
2
3
1
2
3
4
anhydrous MgSO , and concentrated in vacuo. The de-
DBU in DMF showed the highest reactivity for hydro-
trifluoroethylation (Table 1, Entries 17－21). The con-
trol experiments confirmed the requirement of visible
light and the photocatalyst (Table 1, Entries 22 and 23).
With the optimized conditions for both the reactions,
we first evaluated the iodotrifluoroethylation of diverse
aromatic/heteroaromatic and aliphatic alkynes (Table 2).
Aliphatic alkynes were better substrates for the iodotri-
fluoroethylation as the reaction occurred smoothly with
sired iodotrifluoroethylated product 2 was purified by
silica gel flash column chromatography using hexane as
the eluent.
Procedure for hydrotrifluoroethylation
A 50 mL round bottom flask equipped with a mag-
netic stir bar was charged with 2 mol% fac-Ir(ppy)
0.02 mmol, 13 mg) in DMF (10 mL). Alkyne 1 (1
mmol), 1,1,1-trifluoro-2-iodoethane (4 mmol, 394 μL),
DBU (4 mmol, 600 μL), and K CO (2 mmol, 276 mg)
3
(
3
equiv. of CF CH I and 2 mol% of [Ru(bpy) ]Cl .
3 2 3 2
2
3
The use of benzenesulfonate 1k provided 2k' as the
final product (Scheme 1). In the process, iodotrifluoro-
ethylated product (2k) was initially obtained; then, 2k
were added. The round bottom flask was closed with a
rubber cap, placed under blue LEDs (7 W), and stirred
at room temperature for 24 h. The progress of the reac-
tion was monitored by TLC and gas chromatography.
The flask was opened, and the reaction mixture was
diluted with dichloromethane. After the aqueous
work-up, the organic layers were combined, dried over
was converted to 2k' by an S
dide anion, which was formed by the photocatalysis of
CF CH I, attacked the benzenesulfonate moiety of 2k.
The iodotrifluoroethylation of 1h proceeded well
N
2 reaction where the io-
3
2
anhydrous MgSO
4
, and concentrated in vacuo. The de-
even at a 5 mmol scale without a remarkable loss in the
product yield, indicating that the reaction can be ame-
nable to industrial use. Moreover, alkenyl iodide prod-
sired hydrotrifluoroethylated product 3 was purified by
silica gel flash column chromatography using hexane as
the eluent.
ucts 2 are valuable CF building blocks because they can
3
460
www.cjc.wiley-vch.de
© 2016 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2016, 34, 459—464

3
Trifluoroethylation of Alkynes: Synthesis of Allylic-CF Compounds by Visible-Light Photocatalysis
a
Table 1 Optimization for iodo- and hydrotrifluoroethylation of phenyl acetylene 1a
2
mol% Photocatalyst
Base (2 equiv.)
I
+
I
CF3
CF3 +
CF3
Solvent (0.2 mol/L), r.t.
Blue LEDs (7 W), 12 h
(
3 equiv.)
2a
3a
1a
b
Yield /%
Entry Photocatalyst
Base
Solvent Variations
2
a
3a
4
1
2
3
4
5
6
7
8
9
1
[Ru(bpy)
3
]Cl
2
TMEDA
TMEDA
TMEDA
TMEDA
TMEDA
TMEDA
TMEDA
TMEDA
TMEDA
TMEDA
TMEDA
TEA
CH
3
CN
CN
80
76
80
67
77
60
89
90
74
24
35
20
13
0
[Ru(phen)
3
]Cl
2
CH
3
2
fac-Ir(ppy)3
fac-Ir(dFppy)3
[Ir(dtbbpy)(ppy) ]PF
CH CN
3
3
3
7
CH CN
0
2
6
CH CN
9
[Ru(bpy)
3
]Cl
2
CH
3
CN CF
3
CH
2
I (2 equiv.)
17
4
[Ru(bpy) ]Cl
CH CN CF CH I (4 equiv.)
3
2
2
3
3
2
[Ru(bpy) ]Cl
CH CN CF CH I (4 equiv.), 3 mol% Ru
3
3
3
3
2
[Ru(bpy) ]Cl
CH Cl
CF CH I (4 equiv.), 3 mol% Ru
2
3
2
2
2
3
2
0
[Ru(bpy) ]Cl
DMF
CF CH I (4 equiv.), 3 mol% Ru
1
3
2
3
2
11
fac-Ir(ppy)3
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
DMF
36
2
1
1
1
1
1
1
1
1
2
2
2
2
3
4
5
6
7
8
9
0
1
2
3
fac-Ir(ppy)
3
c
fac-Ir(ppy)3
fac-Ir(ppy)3
fac-Ir(ppy)3
fac-Ir(ppy)3
fac-Ir(ppy)3
DBU
49
44
0
c
K CO
3
2
c
t
KO Bu
0
c
K CO /DBU
2
3
Base (2/2 equiv.)
0
66
45
70
74
79
86
0
c
K CO /DBU
2
3
Base (2/2 equiv.), 0.1 mol/L
Base (2/3 equiv.)
9
c
fac-Ir(ppy)
3
K
2
CO
3
/DBU
0
c
fac-Ir(ppy)3
fac-Ir(ppy)3
fac-Ir(ppy)3
－
K CO /DBU
2
3
Base (2/4 equiv.)
0
c
K CO /DBU
2
3
Base (2/4 equiv.), CF CH I (4 equiv.)
3
2
0
c,d
K CO /DBU
2
3
Base (2/4 equiv.), CF CH I (4 equiv.)
3
2
0
K CO /DBU
0
2
3
2
fac-Ir(ppy)3
K CO /DBU
no light
0
0
2
3
a
b
c
d
Reaction scale: 1a (0.1 mmol). Yields were determined by GC using dodecane as the internal standard. 24 h. 0.1 mol/L.
a,b
Table 2 Substrate scope of the iodotrifluoroethylation of alkynes
_
2
3 mol% [Ru(bpy) ]Cl
3
2
TMEDA (2.0 equiv.)
I
R
H
+
I
I
CF3
CH CN (0.2 mol/L), r.t.
R
CF3
3
1
Blue LEDs (7 W), 12 h
2
I
I
I
I
CF3
CF3
CF3
CF3
CF3
F
nBu
Me
MeO
2
e, 84%
2
a, 78%
E:Z = 1:1.9)
2b, 88%
(E:Z = 1:1.7)
2
c, 89%
2d, 84%
(E:Z = 1:1.1)
(
E:Z = 1:1.4)
(
(
E:Z = 1:1.3)
I
I
I
I
I
CF3
CF3
CF3
HO
CF3
Cl
CF3
OH
S
2
h, 95%
2i, 87%
(E:Z = 1:1.1)
2j, 89%
(E:Z = 1:1.1)
2
g, 52%
2
f, 74%
(
E:Z = 1:1.9)
(
E:Z = 1:3.8)
(
E:Z = 1:1.3)
a
b
3 2
Reaction scale: 1 (1.0 mmol), CF CH I (3.0 mmol for aliphatic alkynes and 4.0 mmol for aromatic alkynes). Yields of products are the
sum of the yields of both E/Z isomers; the E/Z ratios were determined by gas chromatography and NOE experiments.
Chin. J. Chem. 2016, 34, 459—464
© 2016 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
461

Roh, lqbal & Cho
COMMUNICATION
Scheme 1 Exceptional substrate for iodotrifluoroethylation
O
S
I
O
2 mol% [Ru(bpy) ]Cl
TMEDA (2.0 equiv.)
O
S
I
3
2
O
1
k
O
CF3
+
O
CH CN (0.2 mol/L), r.t.
3
Blue LEDs (7 W)
I
CF3
2k
(
4.0 equiv.)
PhSO3
after 24 h: 2k : 2k' = 1.6 : 1
after 48 h: only 2k'
I
I
CF3
2k', 79%
(
E:Z=1:2.5)
n＋1
be transformed into CF
3
-containing trisubstituted al-
vides the photo excited complex [M
x
L ] by metal-to-
kenes, commonly found as the structural motifs in
pharmaceuticals and agrochemicals, by various cross-
coupling reactions. To prove this, the isolated product
ligand charge transfer. Then, the activated complex is
reductively quenched by a single electron transfer form
n
an amine, resulting in the formation of [M L
x
] . This
2
h was further subjected to Pd-catalyzed Suzuki and
complex donates one electron to CF
3
CH
2
I, regenerating
CF radical.
n
Sonogashira coupling reactions, forming trisubstituted
[M L
x
] and forming a carbon-centered •CH
2
3
alkenes 4 and 5, respectively. This shows the utility of
The addition of this radical species to alkyne 1 generates
trifluoroethylated vinyl radical 1'. Then, the reaction of
alkenyl iodide products 2 as the CF
Scheme 2).
The substrate scope of the hydrotrifluoroethylation
of alkynes was also investigated under the optimized
conditions where 2 mol% fac-Ir(ppy) and 2∶1 ratio of
DBU/K CO were used in DMF (Table 3). The reaction
3
building blocks
(
Scheme 2 Pd-catalyzed cross-coupling processes using 2h
3
10 mol% Pd(OAc)2
K2CO (2.0 equiv.)
3
2
3
OH
(
1)
showed a limited substrate scope; only aromatic and
heteroaromatic alkynes participated in the reaction, pro-
ducing styrene derivatives 3. Moreover, the reaction at a
larger scale (＞1.0 mmol) resulted in a decreased yield
of the products.
Compared to terminal alkynes, internal alkynes such
as 4-octyne and diphenylacetylene, were not good sub-
strates both for iodo- and hydrotrifluoroethylations with
significantly reduced reactivity. Reactions did not go to
completion and most starting material remained even
with longer reaction time.
ethanol
B
o
OH
8
0 C, 8 h
CF3
4, 68%
I
CF3
2h
5
mol% PdCl (PPh )
2
3 2
3 mol% CuI, TEA
0 oC, 4 h
(2)
4
Based on the results, a plausible mechanism for the
iodo and hydrotrifluoroethylation of alkynes is proposed
CF3
n
in Figure 2. The visible-light irradiation of [M L
x
] pro-
5, 82%
a,b
Table 3 Substrate scope of hydrotrifluoroethylation of alkynes
2
mol% fac-Ir(ppy)3
DBU/K CO3 (4.0/2.0 equiv.)
2
R
H
+
I
CF3
R
CF3
DMF (0.1 mol/L), r.t.
Blue LEDs (7 W), 24 h
1
3
N
CF3
CF3
CF3
CF3
CF3
n-Bu
F
CF3
3l, 40%c,d
3
m, 62%c
E:Z = 3.5:1)
3a, 69%
3c, 88%
(E:Z = 1.2:1)
3e, 67%
(E:Z = 2.6:1)
(
(
E:Z = 1:1)
(
E:Z = 2.4:1)
a
b
Reaction scale: 1 (0.5 mmol), CF
3 2
CH I (2.0 mmol). Yields of products are the sum of the yields of both E/Z isomers. The E/Z ratios
c
d
were determined by gas chromatography and NOE experiments. The reaction did not go to completion even at a 0.2 mmol scale. The
yield of 3l was determined by F NMR spectroscopy due to its volatility.
1
9
462
www.cjc.wiley-vch.de
© 2016 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2016, 34, 459—464

3
Trifluoroethylation of Alkynes: Synthesis of Allylic-CF Compounds by Visible-Light Photocatalysis
Figure 2 Proposed mechanism.
1
' can proceed by several pathways depending upon the
97, 757; (c) Ma, J.-A.; Cahard, D. Chem. Rev. 2008, 108, PR1; (d)
Koike, T.; Akita, M. Top Catal. 2014, 57, 967; (e) B.-Vallejo, S.;
Bonesi, S. M.; Postigo, A. Org. Biomol. Chem. 2015, 13, 11153.
4] For selected examples of trifluoromethylations, see: (a) Cho, E. J.;
Senecal, T. D.; Kinzel, T.; Zhang, Y.; Watson, D. A.; Buchwald, S.
L. Science 2010, 328, 1679; (b) Ball, N. D.; Kampf, J. W.; Sanford,
M. S. J. Am. Chem. Soc. 2010, 132, 2878; (c) Morimoto, H.; Tsubo-
go, T.; Litvinas, N. D.; Hartwig, J. F. Angew. Chem., Int. Ed. 2011,
conditions. The iodide abstraction of 1' from CF CH
3
2
I
provides alkenyl iodide 2. On the other hand, hydro-
trifluoroethylated product 3 can be synthesized either
through the direct hydrogen abstraction by 1' from an
[
•
＋
3
amine radical cation [NR ] or through the deiodination
from 2 using the same photocatalytic system.
5
0, 3793; (d) Tomashenko, O. A.; E.-Adán, E. C.; Belmonte, M. M.;
Grushin, V. V. Angew. Chem., Int. Ed. 2011, 50, 7655; (e) Nagib, D.
A.; MacMillan, D. W. C. Nature 2011, 480, 224; (f) Iqbal, N.; Choi,
S.; Ko, E.; Cho, E. J. Tetrahedron Lett. 2012, 53, 2005; (g) Iqbal, N.;
Choi, S.; Kim, E.; Cho, E. J. J. Org. Chem. 2012, 77, 11383; (h)
Yasu, Y.; Koike, T.; Akita, M. Angew. Chem., Int. Ed. 2012, 51,
Conclusions
An efficient method was developed for the synthesis
of allylic CF
ethylated compounds were obtained selectively from
alkynes and CF CH I by visible-light photocatalysis.
3
compounds. Iodo- and hydrotrifluoro-
9
567; (i) Kim, E.; Choi, S.; Kim, H.; Cho, E. J. Chem. Eur. J. 2013,
9, 6209; (j) Mizuta, S.; Verhoog, S.; Engle, K. M.; Khotavivattana,
3
2
1
Subtle differences in the combination of the catalyst,
base, and solvent controlled the reactivity and selectivity
of the reaction. The iodotrifluoroethylated products were
T.; O’Duill, M.; Wheelhouse, K.; Rassias, G.; Médebielle, M.; Gou-
verneur, V. J. Am. Chem. Soc. 2013, 135, 2505; (k) Xia, J.-B.; Zhu,
C.; Chen, C. J. Am. Chem. Soc. 2013, 135, 17494; (l) Deb, A.; Man-
na, S.; Modak, A.; Patra, T.; Maity, S.; Maiti, D. Angew. Chem., Int.
Ed. 2013, 52, 9747; (m) Iqbal, N.; Jung, J.; Park, S.; Cho, E. J. An-
gew. Chem., Int. Ed. 2014, 53, 539.
obtained in the presence of [Ru(bpy)
in CH CN, whereas the hydrotrifluoroethylated products
were produced using fac-Ir(ppy) and a mixture of DBU
and K CO in DMF. The iodotrifluoroethylation reac-
3 2
]Cl and TMEDA
3
3
[
3
5] Examples for the synthesis of allylic-CF compounds using alkenes
2
3
with CF sources, see: (a) Xu, J.; Fu, Y.; Luo, D.-F.; Jiang, Y.-Y.;
3
tion worked particularly well, even at gram-scale, and
the synthetic utility of the iodotrifluoroethylated prod-
ucts was proved by their coupling reactions, providing
Xiao, B.; Liu, Z.-J.; Gong, T.-J.; Liu, L. J. Am. Chem. Soc. 2011,
133, 15300; (b) Parsons, A. T.; Buchwald, S. L. Angew. Chem., Int.
Ed. 2011, 50, 9120; (c) Chu, L.; Qing, F.-L. Org. Lett. 2012, 14,
2
106; (d) Mizuta, S.; Engle, K. M.; Verhoog, S. G.; López, O.;
3
complex CF -containing products.
O’Duill, M.; Médebielle, M.; Wheelhouse, K.; Rassias, G.; Thomp-
son, A. L.; Gouverneur, V. Org. Lett. 2013, 15, 1250; (e) Mizuta, S.;
Verhoog, S.; Wang, X.; Shibata, N.; Gouverneur, V.; Médebielle, M.
J. Fluorine Chem. 2013, 155, 124; (f) Beniazza, R.; Molton, F.;
Duboc, C.; Tron, A.; McClenaghan, N. D.; Lastécouéres, D.; Vin-
cent, J.-M. Chem. Commun. 2015, 51, 9571.
Acknowledgement
This Research was supported by the Chung-Ang
University Research Scholarship Grants in 2015 and
National Research Foundation of Korea (No. NRF-
[
6] Kreis, L. M.; Krautwald, S.; Pfeiffer, N.; Martin, R. E.; Carreira, E.
M. Org. Lett. 2013, 15, 1634.
2
014R1A1A1A05003274).
[
[
7] Long, Z.-Y.; Chen, Q.-Y. Tetrahedron Lett. 1998, 39, 8487.
8] Recent reviews on visible light-photocatalysis, see: (a) Fagnoni, M.;
Dondi, D.; Ravelli, D.; Albini, A. Chem. Rev. 2007, 107, 2725; (b)
Ravelli, D.; Dondi, D.; Fagnoni, M.; Albini, A. Chem. Soc. Rev.
2009, 38, 1999; (c) Zeitler, K. Angew. Chem., Int. Ed. 2009, 48,
9785; (d) Narayanam, J. M. R.; Stephenson, C. R. J. Chem. Soc. Rev.
2011, 40, 102; (e) Yoon, T. P.; Ischay, M. A.; Du, J. Nat. Chem.
2010, 2, 527; (f) Tucker, J. W.; Stephenson, C. R. J. J. Org. Chem.
2012, 77, 1617; (j) Xuan, J.; Xiao, W. J. Angew. Chem., Int. Ed.
2012, 51, 6828; (h) Shi, L.; Xia, W. J. Chem. Soc. Rev. 2012, 41,
References
[
1] (a) Müller, K.; Faeh, C.; Diederich, F. Science 2007, 317, 1881; (b)
Hagmann, W. K. J. Med. Chem. 2008, 51, 4359; (c) O’Hagan, D.
Chem. Soc. Rev. 2008, 37, 308; (d) Purser, S.; Moore, P. R.; Swal-
low, S.; Gouverneur, V. Chem. Soc. Rev. 2008, 37, 320.
[
[
2] Furuya, T.; Kamlet, A. S.; Ritter, T. Nature 2011, 473, 470.
3] Reviews on trifluoromethylations, see: (a) Dolbier, W. R. Chem. Rev.
1
996, 96, 1557; (b) Prakash, G. K. S.; Yudin, A. K. Chem. Rev. 1997,
Chin. J. Chem. 2016, 34, 459—464
© 2016 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
463

Roh, lqbal & Cho
COMMUNICATION
7
687; (i) Prier, C. K.; Rankic, D. A.; MacMillan, D. W. C. Chem.
Rev. 2013, 113, 5322.
9] Examples using CF CH
Wang, S.; Nie, J.; Ma, J.-A. Angew. Chem., Int. Ed. 2012, 51, 6227;
b) Zhao, Y.; Hu, J. Angew. Chem., Int. Ed. 2012, 51, 1033; (c) Kreis,
L. M.; Krautwald, S.; Pfeiffer, N.; Martin, R. E.; Carreira, E. M. Org.
Lett. 2013, 15, 1634; (d) Feng, Y.-S.; Xie, C.-Q.; Qiao, W.-L.; Xu,
H.-J. Org. Lett. 2013, 15, 936; (e) Zhang, H.; Chen, P.; Liu, G. An-
gew. Chem., Int. Ed. 2014, 53, 10174; (f) Hwang, J.; Park, K.; Choe,
J.; Min, H.; Song, K. H.; Lee, S. J. Org. Chem. 2014, 79, 3267.
[10] Yu, C.; Iqbal, N.; Park, S.; Cho, E. J. Chem. Commun. 2014, 50,
12884.
[
3
2
I, see: (a) Liu, C.-B.; Meng, W.; Li, F.;
(
(Cheng, F.)
464
www.cjc.wiley-vch.de
© 2016 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2016, 34, 459—464