Isolation and characterization of copper(III) trifluoromethyl complexes and reactivity studies of aerobic trifluoromethylation of arylboronic acids

Article abstract of DOI:10.1039/c6ra10302b

The isolation, characterization and reactivity of transition metal trifluoromethyl complexes are fundamental and challenging topics in trifluoromethylation chemistry. We report herein the synthesis and isolation of two new complexes [(phen)Cu^I(PPh₃)₂]⁺[Cu^III(CF₃)₄]^- (2) and (phen)Cu^III(CF₃)₃ (3) as well as a known complex (bpy)Cu^III(CF₃)₃ (4) at room temperature. 2 and 3 have been fully characterized using ¹H, ¹⁹F, ³¹P NMR, elemental analyses and X-ray crystallography. Reactivity studies indicate that 2 is unreactive toward arylboronic acids. In contrast, 3 and 4 can react with various aryl and heteroaryl boronic acids to deliver trifluoromethylated arenes in good to quantitative yields under mild conditions. The presence of a fluoride additive in DMF under aerobic conditions is crucial to these reactions. This study provides fundamental information about the structure and reactivity of elusive Cu(iii) trifluoromethyl complexes that have been proposed as relevant reactive intermediates in many trifluoromethylation reactions.

Full text of DOI:10.1039/c6ra10302b

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Isolation and Characterization of Copper(III) Trifluoromethyl
View Article Online
DOI: 10.1039/C6RA10302B
Complexes and Reactivity Studies of Aerobic Trifluoromethylation of
Arylboronic Acids†
Song-Lin Zhang*a and Wen-Feng Biea
5
Received (in XXX, XXX) Xth XXXXXXXXX 200X, Accepted Xth XXXXXXXXX 200X
First published on the web Xth XXXXXXXXX 200X
DOI: 10.1039/b000000x
characterized Cu(III) trifluoromethyl complex. Later,
Naumann et al. reported anionic square planar [CuΙΙΙ(CF3)4]−
complexes with Ph4P+ or Bu4N+ counterions via oxidation of
55 in-situ Cu(I) trifluoromethyl by halogen.13b Similar ion-pair
complexes were obtained by Grushin by reaction of CuCl or
in-situ formed “CuΙ-CF3” with CF3SiMe3 using air as the
oxidant.13c Heating the ion-pair complexes with bipyridine
(bpy) in acetic acid gave neutral (bpy)CuΙΙΙ(CF3)3.
The isolation, characterization and reactivity of transition metal
trifluoromethyl complexes are fundamental and challenging
10 topics in trifluoromethylation chemistry. We report herein the
synthesis and isolation of two new complexes
[(phen)CuΙ(PPh3)2]+[CuΙΙΙ(CF3)4]− (2) and (phen)CuΙΙΙ(CF3)3 (3) as
well as
a
known complex (bpy)CuΙΙΙ(CF3)3 (4) at room
temperature. 2 and 3 have been fully characterized using 1H, 19F,
15 31P NMR, elemental analyses and X-ray crystallography.
Reactivity studies indicate that
2
is unreactive toward
(a) One-pot synthesis of 2 and 3
arylboronic acids. In contrast, 3 and 4 can react with various aryl
and heteroaryl boronic acids to deliver trifluoromethylated
arenes in good to quantitative yields under mild conditions. The
20 presence of a fluoride additive in DMF under aerobic condition is
crucial to these reactions. This study provides fundamental
information about the structure and reactivity of elusive Cu(III)
trifluoromethyl complexes that have been proposed as relevant
reactive intermediates in many trifluoromethylation reactions.
3 eq. CF3SiMe3
3 eq. AgF
CF3
CuΙΙΙ
CF3
N
N
F3C
F3C
N
N
N
N
CuΙ
CuΙ
+
CuΙΙΙ
CH2Cl2
Ph3P
Br
PPh3
Ph3P
CF3
F3C
Room
Temperature
CF3
1
2
3
(b) Alternative synthesis of 3 and 4
1 eq. phen or bpy
6 eq. CF3SiMe3
CF3
N
N
4 eq. AgF
N
CuΙΙΙ CF3
CF3
N
CuΙΙΙ
or
CuI
DMF
CF3
25 Copper-mediated trifluoromethylation reactions have been
greatly developed and constitute one important branch of
organofluorine chemistry.1-3 Trifluoromethyation of aryl
halides,4,5 boronic acids6, arenes7 and others8-9 with various
CF3 sources promoted by copper salts have been intensively
30 studied during the past decades. Despite the significant
progress achieved in developing efficient reaction
methodologies, the isolation and reactivity properties of
possible copper trifluoromethyl intermediates are surprisingly
scarcely described which are however essential to the
35 mechanistic undertanding of these reactions.10 Very recently,
the characterization and reactivity properties of several CuΙ-
CF3 complexes have been reported that typically contains N-
heterocyclic carbene (NHC) or phenanthroline (phen)
ligand.11
F3C
Room
CF3
Temperature
4
3
(c) Reactivity of 3 and 4 with aryl boronic acids
ArB(OH)2
Reactive at RT-50oC
Up to quantitative yields
3 or 4
Ar-CF3
F salt, O2
60
Scheme 1 Syntheses and reactivity of CuΙΙΙ-CF3 complexes 2-4.
Herein, we report the preparation and isolation of CuΙΙΙ
trifluoromethyl complexes 2-4 by reaction of CuΙ precursors
with CF3SiMe3 in the presence of AgF (Scheme 1). Reactivity
65 studies show that these Cu(III) trifluoromethyl complexes are
able to efficiently trifluoromethylate arylboronic acids in up
to quantitative yields even at room temperature. Considering
the predominant role of phen ligand in copper
trifluoromethylation chemistry,3 the isolation and reactivity
70 properties of the phen-containing CuΙΙΙ trifluoromethyl
complexes should be fundamental to this important area.
40
In contrast, extremely rare studies have been reported on
the isolation, characterization and reactivity properties of
high-valent CuΙΙΙ CF3 complexes which have been frequently
proposed as reactive intermediates for oxidative or
electrophilic trifluoromethylation reactions.12,13 In 1989,
Reaction of (phen)CuΙ(PPh3)(Br) (1)14 with 3 equivalents of
CF3SiMe3 in the presence of AgF in CH2Cl2 at room
temperature allows the concurrent access to 2 and 3 as pure
75 yellow solids in 30% and 31% yields respectively (Scheme 1a,
see ESI for details).† Alternatively, complex 3 can be
synthesized and isolated by a different method of reaction of
CuI/phen with CF3SiMe3 using AgF as oxidant in a higher
yield of 63% (Scheme 1b, see ESI for details).† In both
80 reactions, AgF is crucial, which should probably accelerate
the transmetalation of CF3SiMe3 and act as a one-electron
45 Burton et al reported a pioneering study on the synthesis and
X-ray crystal structure of square planar
a
(CF3)2CuΙΙΙ(dithiocarbomato) complex by oxidation of
[CuΙ(CF3)2]− using thiuramdisulphide.13a This Cu(III)
trifluoromethyl complex could react with aryl iodides to give
50 trifluoromethylated arenes at 90-100°C. As far as we know,
this is the first example of the isolation and reactivity of well-
This journal is © The Royal Society of Chemistry [year]
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RSC Advances
Page 2 of 6
oxidant to convert the Cu(I) to higher oxidation states. When
View Article Online
DOI: 10.1039/C6RA10302B
bpy was used instead of phen in Scheme 1b, a neutral
(bpy)CuΙΙΙ(CF3)3 (4) was obtained in an isolated high yield of
71%.
5
19F NMR spectrum of complex 2 shows a resonance at -34.6
ppm with singlet splitting, consistent with previous reported
[CuΙΙΙ(CF3)4]− species.13b,c 19F NMR spectrum of complex 3
shows two signals at -24.4 (septet) and -37.4 (quartet) ppm,
with a ratio of ca 1:2 with the signal at -37.4 ppm being the
1
10 major one. H NMR of complex 2 clearly shows a ratio of 1:2
of phen/PPh3 and the typical splitting of the phen ligand in
Cu(I) complexes (see ESI for more details).† 1H NMR
spectrum of complex 3 shows only resonances of phen ligand
which are greatly low-field shifted compared to those in
15 complex 2. 31P NMR spectrum of 2 shows a weak signal at 3.0
ppm, confirming the existence of coordinated PPh3 ligand.
Complex 4 shows a similar structure to 3, with two fluorine
signals at -24.0 (septet) and -36.1 (quartet) ppm in 19F NMR
and protons of bpy in 1H NMR, which is consistent with
20 previously reported data.13c
Fig. 2 ORTEP drawing of complex 3 with thermal ellipsoids at 30%
probability. All the hydrogen atoms are omitted for clarity.
oxidation
Ag0
+
AgBr
N
Ph3P
+
N
N
N
+
CuΙ
CuΙΙ
+
FSiMe3
transmetalation
Br
Ph3P
Observed, detected by 19F NMR
and X-ray crystal structure
CF3
1
CF3
A
CF3SiMe3
+ AgF
Disproportionation
The structures of 2 and 3 were further confirmed by X-ray
crystallographic diffraction analyses (Fig.s 1-2).15 Complex 2
is composed of a square planar [CuΙΙΙ(CF3)4]− anion and a
tetrahedral [(phen)CuΙ(PPh3)2]+ countercation (Fig. 1). The
25 Cu-CF3 bond lengths in [CuΙΙΙ(CF3)4]− are averaged to about
1.936(7) Å. Complex 3 adopts an approximately trigonal
bipyramidal geometry with phen, Cu and one CF3 ligand lying
in the equatorial plane and the other two CF3s occupying the
apical positions (Fig. 2). The equatorial Cu-CF3 bond is
30 shorter than apical Cu-CF3 bonds (1.938(5) Å for equatorial
v.s. 1.953(5), 1.961(5) Å for apical Cu-CF3 bonds). These
bond lengths are shorter than Cu-CF3 bonds in related Cu(I)
trifluoromethyl complexes reported. For example, Cu-CF3
N
N
CF3
CuΙΙΙ
N
N
F3C
Equilibrium
N
N
CuΙΙΙ
+
CuΙ
CuΙ
F3C
CF3
F3C
Ph3P
CF3
Ph3P
CF3
CF3
PPh3
B
3
2
phen
+
PPh3
+
50
Scheme 2 Plausible mechanism for the concurrent formation of 2 and 3.
As to the mechanism for the concurrent formation of 2 and
3 in Scheme 1a, it is proposed that a Cu(II) precursor A is
initially formed.16 A disproportionates into 3 + B + PPh3
55 which is in equilibrium with 2 + phen by ligand exchange
(Scheme 2). Evidence supporting this mechanistic scheme
include the observation of Cu(II) intermediates and Ag mirror
during workup, 19F NMR detection of FSiMe3 at -157.9 ppm
and the access to X-ray crystal strucuture of PPh3-ligated
60 dimeric AgBr (5) (for more details, refer to ESI†).17
Additional evidence supporting the equilibrium between 2 and
3 comes from the observation that addition of phen to acetic
acid solution of 2 led to the efficient formation of 3 in 45%
isolated yield (see ESI for details).† Possibly, the addition of
65 excess phen to the solution of 2 drives the equilibrium to the
side of 3 (Scheme 2).
bonds in (PPh3)3CuΙ−CF3, phenCuΙ(PPh3)CF3, CuΙ(CF3)2 , and
−
35 (NHC)CuI-CF3 are reported to be 2.025(7), 1.985(1), 1.970(6)
and 2.022(4) Å.11a,b,d This should partly be attributed to the
different coordination geometries and the more electrophilic
nature of the Cu(III) center in 3. The trigonal bipyramidal
geometry of 3 is unusual considering that transition metal
40 complexes with d8 electronic configuration, such as Pd(II),
Ni(II) and Cu(III), often adopts square planar geometry.
Reactivity properties of complexes 2-4 were further studied
to evaluate their reaction with arylboronic acids.18 After initial
screening of the reaction conditions (Table 1, entries 1-4), it
70 was found that reaction of complex 3 with 2 equivalents of
para-methoxyphenyl
boronic
acid
(6a)
gave
the
trifluoromethylated product 7a in 65% yield in the presence of
2 equivalents of AgF in DMF at 80℃ for 18 hours (entry 4).19
A breakthrough was achieved with the use of KF additive,
75 which led to the quantitative trifluoromethylation of 5a even
at room temperature in 3 hours (entries 5-10). These results
should be the first examples of room-temperature quantitative
trifluoromethylation of arylboronic acids by isolated CuIII
trifluoromethyl complexes.6n Reducing the reaction time to 1
80 hour still led to a 90% yield while the reaction can reach a
85% yield in only 0.5 hour (entries 11&12).
Fig. 1 ORTEP drawing of complex 2 with thermal ellipsoids at 50%
probability. All the hydrogen atoms and one solvent molecule are omitted
45 for clarity. Disorders of fluorine atoms are observed.
2
|
Journal Name, [year], [vol], 00–00
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Table 1 Reactivity studies of complex 3 with arylboronic acid a
Table 2 Substrate scope for reaction of 3 with various arylboronic acids a
View Article Online
DOI: 10.1039/C6RA10302B
B(OH)2
CF3
B(OH)2
CF3
1 eq. KF, RT
CF3
CF3
N
N
CF3
CF3
N
N
Additive, Temp, time
DMF, O2
or 1 eq. AgF, 50 o
C
Cu
CF3
Cu
CF3
+
+
DMF, O2, 3 h
R
OCH3
OCH3
R
3
6
7
3
6a
7a
CF3
CF3
CF3
T (oC)
Time (h)
Yield (%) b
CF3
entry
Additive
MeO
1
2
3
4
5
6
7
8
9
―
KI
Cs2CO3
AgF
KF
KF
KF
KF
KF
80
80
80
80
80
18
18
18
18
18
10
18
18
10
3
trace
23
12
65
97
99
99
99
99
99
90
85
O
7a, 99% (84%)b
7b, 92% (80%)b
7c, 80%
7d, 47%
CF3
CF3
CF3
CF3
NC
Cl
F
O
7e, 99% c
CF3
7g, 42%
7f, 20%
7h, 20%
CF3
80
50
CF3
RT
RT
RT
RT
RT
CF3
O
OMe
O
7i, 99% c
CF3
7j, 96% c
O
7k, 20%
7l, 14%
10
11
12
KF
KF
KF
1
0.5
CF3
OMe
7m, trace
7n, trace
a Reaction conditions: 3 (0.1 mmol), 6a (0.2 mmol), additive (0.2 mmol),
O
4,4′-difluorobiphenyl (0.2 mmol, internal standard), DMF (1 mL), under
CF3
CF3
CF3
b
dry O2 atmosphere.
Yields determined by 19F NMR spectroscopy
CF3
7o, 61% c
S
N
N
5 relative to 6a.
7r, N.R. c
7p, 60% c
7q, 23% c
40 Reaction yields were determined by 19F NMR spectroscopy using 4,4′-
a
With the optimized reaction conditions identified, we next
examined reaction of 3 with a variety of substituted aryl
boronic acids with diverse electronic properties (Table 2). The
10 reactions show a complicated effect of electronic properties
and substitution position of the substituents. Generally,
electron-rich substituents are benificial to the reactions. For
substrates with strongly electron-withdrawing substituents,
b
difluorobiphenyl (-117.0 ppm) as internal standard.
Values in
c
parentheses are isolated yields using column chromatography. AgF at
50°C in the presence of 4 Å molecular sieves.
45 Table 3 Substrate scope for reaction of 4 with various arylboronic acids a
o
B(OH)2
using AgF at a little higher 50 C (in replace of KF at RT) is
CF3
CF3
N
N
1 equiv. KF
15 needed to achieve better yields. Additionally, para-substituted
boronic acids are generally more reactive than meta- and
ortho-substituted analogs (please see 7a vs 7l, 7m; 7b vs 7k).
Finally, heteroaryl boronic acids such as 2-benzothiophenyl,
2-benzofuryl, and 3-pyridyl boronic acids can also be
20 trifluoromethylated to produce the desired trifluoromethylated
heteroarenes 7o-q in moderate to good yields. These results
imply that 3 may be potential reactive intermediate in some
CuΙΙΙ CF3
+
DMF, O2, 50oC, 18 h
R
CF3
R
6
4
7
CF3
CF3
CF3
CF3
H3CO
O
7a, 99% (80%)b
7c, 99%
7d, 99%
7b, 99%
OCH3
CF3
CF3
CF3
copper/phen-mediated
oxidative
and
electrophilic
CF3
O
trifluoromethylation reactions.
O
O
25
Under similar conditions, complex 4 also shows good
reactivity with various aryl boronic acids, as summarized in
Table 3. In sharp contrast to 3 and 4, the ion-pair complex 2
shows little reactivity (Table S1 in ESI).† The reasons for this
reactivity difference are currently not well understood.
O
7i, 90%
7e, 74%
7j, 92%
7m, trace
O
CF3
CF3
CF3
S
N
7o, 77%
7r, trace
7p, 20%
30
Although at the current stage, the detailed reaction pathway
remains still elusive, a plausible mechanism is suggested as in
Scheme 3 based on the experimental observations. A key
Cu(III) intermediate i is proposed to account for the formation
of Ar-CF3 via reductive elimination, which should result from
a
Reaction yields were determined by 19F NMR spectroscopy using 4,4′-
b
difluorobiphenyl (-117.0 ppm) as internal standard.
parentheses are isolated yields using column chromatography.
Values in
50 resence of water to generate a new Cu(III) intermediate iv.
Ligand exchange of Ar with iv should produce intermediate i’
that can give a second Ar-CF3 after reductive elimination.
This mechanism proposal can rationalize the indispensable
role of F salt and oxygen for this reaction, and the optimal
35 ligand exchange of initial complex 3 with Ar ligand from
ArB(OH)2 in the presence of F salt and water impurity.
Accordingly, intermediate ii (or iii by comproportionation of
ii with 3) is formed which is then oxidized by oxygen in the p-
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Barata-Vallejo, S.; Bonesi, S. M.; Postigo, A. Org. Biomol. Chem.,
reaction stoichiometry of 1:2 of 3 with ArB(OH)2. In addition,
the observation of better reactivity of electron-rich
arylboronic acids and para-substituted arylboronic acids
(please refer to Table 2) can also be explained by the more
facile transmetalation of Ar of ArB(OH)2 to copper center in
critical intermediate i and i’ for electronically more rich and
sterically less demanding Ar group. Further studies are
underway on the elucidation of the detailed mechanism and
the preparation and reactivity of CuΙΙΙ CF3 complexes with
View Article Online
DOI: 10.1039/C6RA10302B
50
55
2015, 13, 11153.
3
4
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5
For some examples of copper-mediated trifluoromethylation of aryl
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60
10 other ancillary ligands.
F
B(OH)3
ꢀCF3
N
N
CuΙΙ
iii
reductive
F3C
CF3
65
N
N
N
N
elimination
oxidation
1/2O2, H2O
or
N
N
CuΙΙΙ
CuΙΙΙ
CuΙΙΙ
X
CF3
CF3
F3C
F3C
F3C
CF3
X = OH or
CF3
Ar
OH
iv
Fꢀ, OHꢀ
ArB(OH)2
Ar-CF3
3
i
N
N
ArB(OH)2
Fꢀ
CuΙ
F
B(OH)3
ii
CF3
70
Ar-CF3
N
N
N
N
5
CuΙΙΙ
CuΙ
X
reductive
elimination
X
F3C
Ar
v
i′
75
Scheme 3 Proposed mechanism for the aerobic trifluoromethylation of
arylboronic acids by CuΙΙΙ CF3 complex 3.
In summary, CuΙΙΙ trifluoromethyl complexes 2-4 with
15 representative phen or bpy ligand were prepared and isolated
at room temperature via oxidation of CuΙ precursors by AgF
and have been fully characterized in both solid state and
solution phase. Reactivity studies show that 3 and 4 are highly
reactive with aryl and heteroaryl boronic acids under mild co-
20 nditions. Up to quantitative yields can be achieved at room
temperature for trifluoromethylation of boronic acids using 3.
In contrast, 2 shows little reactivity. The isolation and
reactivity of these CuΙΙΙ CF3 complexes provides valuable
information for copper trifluoromethylation chemistry.
80
6
85
90
25
This study was supported by the National Natural Science
Foundation of China (Nos. 21472068, 21202062) and the
Natural Science Foundation of Jiangsu (No. BK2012108).
95
Notes and references
a
The Key Laboratory of Food Colloids and Biotechnology, Ministry of
30 Education, School of Chemical and Material Engineering, Jiangnan
University, Wuxi 214122, Jiangsu Province, China. Fax/Tel.: +86-510-
85917763; E-mail: slzhang@jiangnan.edu.cn
† Electronic Supplementary Information (ESI) available: Experimental
details, spectroscopic characterization data, X-ray crystallographic study,
35 19F NMR monitoring of reaction course and general procedures of
reaction of 2-4 with arylboronic acids. See DOI: 10.1039/b000000x/
100
105
110
115
7
1
For organofluorine chemistry and applications, see: (a) P. Kirsch,
Modern Fluoroorganic Chemistry, Wiley-VCH, Weinheim, Germany,
2004; (b) S. Purser, P. R. Moore, S. Swallow and V. V. Gouverneur,
Chem. Soc. Rev., 2008, 37, 320; (c) Y. Jiang, H. Yu, Y. Fu, L. Liu,
Sci. China Chem., 2015, 58, 673.
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45
8
9
(a) H. Egami and M. Sodeoka, Angew. Chem., Int. Ed., 2014, 53,
8293; (b) E. Merino and C. Nevado, Chem. Soc. Rev., 2014, 43, 6598.
Copper-mediated trifluoromethylation of alkynes, see: (a) L. Chu and
F.-L. Qing, J. Am. Chem. Soc., 2010, 132, 7262; (b) K. Zhang, X.-L.
Qiu, Y. Huang and F.-L. Qing, Eur. J. Org. Chem., 2012, 58; (c) D.-F.
Luo, J. Xu, Y. Fu and Q.-X. Guo, Tetrahedron Lett., 2012, 53, 2769;
(d) Y.-L. Ji, J.-J. Kong, J.-H. Lin, J.-C. Xiao, Y.-C. Gu, Org. Biomol.
Chem., 2014, 12, 2903.
2
For general reviews, see: (a) M. Schlosser, Angew. Chem., Int. Ed.,
2006, 45, 5432; (b) J.-A. Ma and D. Cahard, Chem. Rev., 2008, 108,
PR1; (c) V. V. Grushin, Acc. Chem. Res., 2010, 43, 160; (d) T.
Furuya, A. S. Kamlet and T. Ritter, Nature, 2011, 473, 470; (e) T.
Liang, C. N. Neumann and T. Ritter, Angew. Chem., Int. Ed., 2013,
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10 D. M. Wiemers and D. J. Burton, J. Am. Chem. Soc., 1986, 108, 832.
4
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Journal Name, [year], [vol], 00–00
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11 For well-characterized CuΙ-CF3 complexes, see: (a) G. G. Dubinina,
View Article Online
H. Furutachi and D. A. Vicic, J. Am. Chem. Soc., 2008, 130, 8600; (b)
G. G. Dubinina, J. Ogikubo and D. A. Vicic, Organometallics, 2008,
27, 6233; (c) H. Morimoto, T. Tsubogo, N. D. Litvinas and J. F.
Hartwig, Angew. Chem., Int. Ed., 2011, 50, 3793; (d) O. A.
Tomashenko, E. C. Escudero-Adan, M. M. Belmonte and V. V.
Grushin, Angew. Chem., Int. Ed., 2011, 50, 7655; (e) Z. Weng, R.
Lee, W. Jia, Y. Yuan, W. Wang, X. Feng and K.-W. Huang,
Organometallics, 2011, 30, 3229; (f) A. I. Konovalov, J. Benet-
Buchholz, E. Martin and V. V. Grushin, Angew. Chem., Int. Ed.,
2013, 52, 11637; (g) L. I. Panferova, F. M. Miloserdov, A.
Lishchynskyi, M. M. Belmonte, J. Benet-Buchholz and V. V.
Grushin, Angew. Chem., Int. Ed., 2015, 54, 5218.
DOI: 10.1039/C6RA10302B
5
10
15
20
25
12 (a) A. J. Hickman and M. S. Sanford, Nature, 2012, 484, 177; (b) A.
Casitas and X. Ribas, Chem. Sci., 2013, 4, 2301.
13 For CuΙΙΙ-CF3 complexes, see: (a) M. A. Willert-Porada, D. J. Burton
and N. C. Baenziger, J. Chem. Soc. Chem. Commun., 1989, 1633.
The crystal structure was later redetermined by Marsh with corrected
space group, see: R. E. Marsh, Acta Cryst., 1997, B53, 317; (b) D.
Naumann, T. Roy, K.-F. Tebbe and W. Crump, Angew. Chem., Int.
Ed. Engl., 1993, 32, 1482; (c) A. M. Romine, N. Nebra, A. I.
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Chem., Int. Ed., 2015, 54, 2745; (d) J. A. Schlueter, U. Geiser, J. M.
Williams, H. H. Wang, W.-K. Kwok, J. A. Fendrich, K. D. Carlson,
C. A. Achenbach, J. D. Dudek, D. Naumann, T. Roy, J. E. Schirber
and W. R. Bayless, J. Chem. Soc. Chem. Commun., 1994, 1599. The
crystal structure was later redetermined, see: U. Geiser, J. A.
Schlueter, J. M. Williams, D. Naumann and T. Roy, Acta Cryst.,
1995, B51, 789.
30 14 For the preparation of phenCu(PPh3)Br (1), see: R. K. Gujadhur, C. G.
Bates and D. Venkataraman, Org. Lett., 2001, 3, 4315.
15 CCDC 1402421 (3), 1402422 (2) and 1402423 (5) contain the
supplementary crystallographic data for this manuscript. These data
can be obtained free of charge from the Cambridge Crystallographic
35
40
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
16 During the work-up process, a small amount of green impurity was
observed which might imply the involvement of Cu(II) intermediates
in the reaction process.
17 For the formation of intermediate A and crystal structure of PPh3-
ligated AgBr (5), please refer to ESI.
18 For detailed reaction procedure and 19F NMR determination of
reaction yields, please refer to ESI.
19 Reaction of 1 eq. or 3 eq. of 6a with complex 3 led to lower yields.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 5

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Page 6 of 6
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DOI: 10.1039/C6RA10302B
N
N
N
N
CF3
CuΙΙΙ
CF3
F3C
F3C
N
N
CuΙΙΙ
CuΙΙΙ
CuΙ
CF3
F3C
CF3
CF3
F3
C
CF3
PPh3
Ph3P
4
3
2
O2
ArB(OH)2
Ar-CF3
Highly reactive at RT
Up to quantitative yields
ArB(OH)2
Ar-CF3
Unreactive
Novel phenCuΙΙΙ-CF3 complexes, isolated purely and fully characterized, are highly reactive for
aerobic trifluoromethylation of arylboronic acids.