Synthesis of Chloro(phenyl)trifluoromethyliodane and Catalyst-Free Electrophilic Trifluoromethylations

Article abstract of DOI:10.1021/acs.orglett.8b01510

The present work deals with a challenge in the synthesis of aryltrifluoromethyliodanes (ArICF₃X) and develops a direct route to PhICF₃Cl via a simple ligand-exchange reaction of PhI(OCOCF₃)₂, Me₃SiCF₃, and NaCl for the first time. The I-Cl bond length in PhICF₃Cl supports its iodonium character, which enables an enhanced CF₃-transfer capability in electrophilic S-, O-, N-, and C-trifluoromethylations as well as in catalyst-free trifluoromethylation-cyclizations of arylisonitriles.

Full text of DOI:10.1021/acs.orglett.8b01510

Letter
pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Synthesis of Chloro(phenyl)trifluoromethyliodane and Catalyst-Free
Electrophilic Trifluoromethylations
Cong Xu,‡,∥ Xiaoning Song,†,∥ Jia Guo,† Sibao Chen,† Jie Gao,† Jing Jiang,† Fengyun Gao,†
Yuxin Li,‡ and Mang Wang*,†
†Jilin Province Key Laboratory of Organic Functional Molecular Design & Synthesis, College of Chemistry, Northeast Normal
University, Changchun 130024, China
‡National Engineering Laboratory for Druggable Gene and Protein Screening, School of Life Sciences, Northeast Normal University,
Changchun 130117, China
S
* Supporting Information
ABSTRACT: The present work deals with a challenge in the
synthesis of aryltrifluoromethyliodanes (ArICF3X) and
develops a direct route to PhICF3Cl via a simple ligand-
exchange reaction of PhI(OCOCF3)2, Me3SiCF3, and NaCl
for the first time. The I−Cl bond length in PhICF3Cl supports
its iodonium character, which enables an enhanced CF3-transfer capability in electrophilic S-, O-, N-, and C-
trifluoromethylations as well as in catalyst-free trifluoromethylation−cyclizations of arylisonitriles.
Scheme 1. Electrophilic Trifluoromethylating Agents
he introduction of the trifluoromethyl group into organic
Tmolecules has become one of the most popular topics of
organofluorine chemistry because the trifluoromethylated
compounds usually exhibit significantly enhanced efficacy in
physical, chemical, or biological properties.1 Consequently,
numerous methods have emerged for trifluoromethylations,
among which one of the major challenges is the development
and utilization of powerful and easily-handled CF3 sources.2,3
In particular, those low-cost, practical, and scalable electro-
philic trifluoromethylating agents are highly desired.3
There are two classes of electrophilic trifluoromethylating
agents widely used in this field. One mainly includes
chalcogenium salts,3f,4 in which the representatives are S-
CF3-dibenzothiopheniums (Scheme 1(1), Umemoto (1990s)).
Other S-based CF3-reagents5−7 have also been developed
recently (Scheme 1 (1)). The second class belongs to
aryltrifluoromethyl λ3-iodanes (ArICF3X) which were defined
as fundamentally electrophilic perfluoroalkylating reagents in
1978 (Scheme 1(2), challenging issue).8 However, their
preparation and application is, in fact, a never fully solved
challenge in fluorine chemistry. Previous attempts by
Yagupolskii and Umemoto failed due to the instability of the
involved intermediate, although the similar preparation of
ArICnF2n+1X (n > 1) by the condensation of (CF3CO2)2-
ICnF2n+1 with arenes could be successfully achieved.8 Long
after the pioneering work, Togni and co-workers attempted to
prepare ArICF3X through a ligand-exchange reaction of ArIX2
with CF3 at the iodine center using Me3SiCF3 (TMSCF3) as
the CF3 source. Unfortunately, all experimental results were
negative.9 In 2006, the same group designed a three-step
method for the synthesis of two CF3-hypervalent iodanes
(namely as Togni’s reagents), which bear a rigid benziodox-
olone backbone to increase the stability of the molecules
(Scheme 1 (2), Togni (2006)) from 2-iodobenzoic acid/2-
Received: May 14, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.8b01510
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
a
Table 1. Optimization of Reaction Conditions
Scheme 2. S-, O-, N-, and C-Trifluoromethylations Using 1a
b
PIFA/
entry TMSCF3/KF
time1 (h),
temp1 (°C)
time2 (min),
temp2 (°C)
yield of 1a
(%)
1
2
3
4
5
6
7
8
1:2:2
1:2:1
1:2:1
1:2:1
0.5, 25
0.5, 25
0.5, 0
∼10, rt
∼10, rt
∼10, rt
∼10, rt
∼10, rt
∼10, rt
∼10, rt
1, rt
1, 0
1, 0
1, 0
1, 0
14
23
34
39
45
75
74
77
83
78
86
84
70
80
55
24, −20
24, −45
24, −45
24, −45
24, −45
24, −45
24, −40
21, −45
18, −45
9, −45
1:2:1
1:2:1.5
1:1.5:1.5
1:1.5:1.5
1:1.5:1.5
1:1.5:1.5
1:1.5:1.5
1:1.5:1.5
1:1.5:1.5
1:1.4:1.4
1:1.8:1.8
9
10
11
12
13
14
15
1, 0
1, 0
1, 0
18, −45
18, −45
a
Reaction conditions: PIFA (0.5 mmol), MeCN (1 mL), NaCl (15%
b
aq, 20 mL), acetone (10 mL), N2. Isolated yield.
a
Table 2. Synthesis of PhICF3X
b
entry
MX aq
NaCl
KCl
NaBr
KF
observable products
yield of 1 (%)
a
Reaction conditions: Sub (0.2 mmol), 1a (0.1 mmol), Et3N (0.2
1
2
3
4
5
6
7
8
PhICF3Cl
PhICF3Cl
PhICF3Br
1a, 86
1a, 76
1b, 70
b
mmol), MeOH (2 mL), N2. Sub (0.1 mmol), 1a (0.12 mmol), DCM
(2 mL), N2. Sub (5 mmol), 1a (0.1 mmol), air. Sub (0.1 mmol), 1a
(0.15 mmol), NaH (0.11 mmol), DMF (1.5 mL), N2. Sub (0.3
mmol), 1a (0.15 mmol), DMF (1 mL), N2. Sub (0.3 mmol), 1a (0.1
mmol), K2CO3 (0.3 mmol), DMF (1.5 mL), N2. Sub (0.1 mmol), 1a
(0.12 mmol), DCM (1 mL), N2. Sub (0.2 mmol), 1a (0.15 mmol),
c
d
e
c
PhI
PhI
PhI
PhI
PhI
PhI
f
c
NaI
g
c
NaBF4
NaPF6
NaH2PO4
NaOTf
NaOTs
NaSO4
h
c
i
DMF (1 mL), N2. Sub (0.2 mmol), 1a (0.1 mmol), MeCN (1 mL),
c
j
k
N2. Sub (0.2 mmol), 1a (0.1 mmol), DCM (1 mL), N2. 19F NMR
c
l
9
10
11
yields using benzotrifluoride as an internal standard. Isolated yields.
c
c,d
PhI, CF3OTs
c
PhI
free trifluoromethylation−cyclizations of arylisonitriles leading
to CF3-substituted phenanthridines.
a
Reaction conditions: PIFA (0.5 mmol), MeCN (1 mL), MX (15%
b
c
1
After detecting the [PhICF3]+ species,12 we sought a
practical method to isolate it for utilization. According to
Togni’s work,9 the exchange between ligand X of ArIX2 and
CF3 most likely occurred but was followed by quick
degradation of the desired ArICF3X. During our work, we
gradually recognized that ligand X is a key factor for the
stability of ArICF3X. After stirring a mixture of PhI(OAc)2
(PIDA) and TMSCF3 in MeCN at room temperature in the
presence of KF, we quenched the reaction with aq NaCl
solution and studied the resulting mixture. A small amount of
white solid was occasionally obtained. To our delight, the
NMR and MS data supported the existence of PhICF3Cl (1a,
Table 1). However, the reaction could not be repeated well.
Instead, we often detected the formation of PhI. It indicated
that the exchange reaction between PIDA and TMSCF3
worked but the product degraded. With the consideration
that low temperature might benefit the stability of PhICF3Cl,
we performed the reaction at lower temperature. Unfortu-
nately, the reaction gave a trace amount of 1a at 0 °C but no
1a at −45 °C. In these cases, PIDA remained before the NaCl
aq, 20 mL), acetone (10 mL), N2. Isolated yields. Detected by H
d
NMR spectroscopy. Detected by 19F NMR spectroscopy.
iodobenzylic alcohol and TMSCF3.10 Since then, no work
appeared in either preparation or even detection11 of noncyclic
ArICF3X for a long time. Their applications as CF3 reagents
have been challenging this field.
In 2013, our group12 and Guo’s group13 independently
obtained MS spectroscopic evidence suggesting the existence
of the [PhICF3]+ species. Recently, Toste’s group isolated
noncyclic ArICF3X by treating Togni’s reagents, synthesized
from TMSCF3, with HCl gas (Scheme 1 (2), Toste (2016)).14
The counterions were recognized as the key factor for the
stability of the resulting CF3-iodoniums in their work. Here, we
reported a never-before completed strategy9 to directly prepare
PhICF3Cl (1a, Scheme 1 (3)) from a direct ligand-exchange
reaction of PhI(OCOCF3)2, TMSCF3, and NaCl for the first
time. The enhanced CF3-transfer capability and wide
utilizations of PhICF3Cl were found in various catalyst-free
S-, O-, N-, and C-trifluoromethylations as well as in catalyst-
B
DOI: 10.1021/acs.orglett.8b01510
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Letter
Compound 1a is a white solid, which exhibits complete air
tolerance under ambient conditions but decomposes at about
116 °C (for DTA and TGA data, see the SI). In addition, 1a
slowly degraded in organic solvents. We found that its
degradation in CD3CN was faster than in DMSO-d6, CDCl3,
or acetone-d6 (see the SI). By comparison, PhICF3Br 1b is apt
to degrade during storage and remarkably decomposes in
solvent even though it is stable enough to be identified. The X-
ray crystallographic analysis of 1a showed (Table 1) that it
exhibits a distorted T-shape geometry, evidenced by the
C(CF3)−I−Cl bond angle (172.9(3)°). Moreover, the I−Cl
bond length (2.829(3) and 2.841(2) Å) suggests that 1a
possesses an iodonium character.14 The chloride-bridging
interactions, observed throughout the structure of 1a, result
in the formation of a tetramer (Table 1 and SI, the solid state
structure of 1a), which is likely another factor for its stability in
the solid state. Here, we developed a simple and direct method
for the synthesis of noncyclic CF3-containing λ3-iodane 1a. Its
gram-scale preparation with 80% yield further demonstrated
the efficiency and practicability of the method (see the SI).
With a new CF3 agent in hand, it is necessary to investigate
its reactivity in various trifluoromethylations. Compared with
Togni’s reagent hydrochloride-like agents prepared by Toste,14
better solubility of PhICF3Cl in organic solvents would enable
more convenient use in synthesis. Indeed, all trifluoromethly-
tions tested with PhICF3Cl (Scheme 2 and 3) did not require
phase-transfer catalyst. S-Trifluoromethylations10b of both 1-
dodecanethiol and thiophenol proceeded in the presence of
Et3N, affording CF3 thioethers 2 and 3 efficiently. When 4-
methylbenzenesulfonic acid, 3-phenylpropanol, and 2,4,6-
trimethylphenol were selected for O-trifluoromethylation,15
CF3 ester 4, and CF3 ethers 5 and 6 were delivered in good
yields, respectively. In the case of N−H ketimine, which was
proven to be inert toward Togni’s reagent in the absence of
catalyst,16 the N−CF3 product 7 was isolated in 72% yield by
stirring a mixture of diphenylmethanimine and 1a in DMF at
35 °C for 14 h.
Next, we further evaluated the scope of this agent toward
C−H trifluoromethylations. As described in Scheme 2, CF3
could be introduced onto the α-Csp3 of β-keto ester10b in the
presence of K2CO3 to deliver 8 in 55% yield. Alkenes were also
compatible with our protocol. By reacting ketene dithioacetal
with 1a in DCM for 12 h, a vinyl Csp2−H trifluoromethylation
product12 was obtained in excellent yield. In the case of silyl
enol ether, α-CF3-substituted ketone 10 was isolated as the
final product.17 With respect to the trifluoromethylations of
electron-rich arenes,18 both indole and 1,3,5-trimethoxyl
benzene were suitable substrates to give CF3-substituted
arenes 11 and 12 in 65% and 72% yields, respectively.
Clearly, the broad substrate compatibility and the enhanced
CF3-transfer capability suggest unique usefulness of 1a in
trifluoromethylation (Scheme 2). With the aim of exploring its
versatile synthetic applications, we next investigated the use of
1a in CF3-substituted heterocycle synthesis. Trifluoromethyla-
tion−cyclization of 2-isocyano-1,1′-biphenyls provides an
important entry to 6-CF3-substituted phenanthridines.19
Various trifluoromethylating reagents have been used via
either a radical or an electrophilic process in the presence of a
catalyst or an initiator.20 Notably, only by stirring a mixture of
isocyanides 13 and 1a in DMF were all desired CF3-substituted
heterocycles 14 obtained in 57−94% yields in our work
(Scheme 3). Undoubtedly, such a simple and mild process
exhibits again a powerful CF3-transfer ability of 1a in
Scheme 3. Trifluoromethylation−Cyclizations of 13 Using
a,b
1a
a
Reaction conditions: 1a (0.24 mmol), 13 (0.2 mmol), DMF (2 mL),
b
N2. Isolated yields.
quench process, while PhICl2 was formed instead after the
NaCl quench process likely via an exchange reaction between
PIDA and Cl anion (for all of the above experiments using
PIDA, see Table S1). Thus, we tested other PhIX2 substrates.
To our delight, the reaction using PIFA was repeated well and
with a slightly better yield of 1a (Table 1, entries 1−5).
Additionally, both the amount and the ratio of PIFA, TMSCF3,
and KF were also a factor for achieving good yield (Table 1,
entries 5−7; see also the SI). When TMSCF3 and KF were
used in a ratio of 1.5:1.5 compared with PIFA at −45 °C, 1a
was isolated in 74% yield (Table 1, entry 7). Interestingly, both
the time and the temperature during the NaCl quench step
also played decisive roles for good results (Table 1, entries 8−
15). After having been stirred for 21 h at −45 °C, the reaction
mixture was quickly poured into a mixed solution of 15% of aq
NaCl and acetone under stirring at 0 °C for only 1 min and
then was followed by the extraction using CH2Cl2.
Concentration of the extract could deliver 1a in 86% yield
(Table 1, entry 11). Shorter reaction time led to lower yield
(Table 1, entries 12−15). With PhICl2 or PhI(OH)(OTs) as
substrates, no reactions were observed at −45 °C (see Table
S2).
Moreover, the activator for TMSCF3 was screened, but only
KF and CsF were suitable (see the SI). Regarding the reaction
solvent, CH2Cl2, DCE, MeCO2Et, THF, DMF, DMSO, EtOH,
and MeOH were tested, but all of them were ineffective (see
the SI). For quenching reagents, besides NaCl (entry 1, Table
2), KCl was another suitable chloride leading to 1a in 76%
yield (entry 2, Table 2). Notably, NaBr furnished PhICF3Br
(1b) in 70% yield (entry 3, Table 2). By comparison, Toste
could not obtain ArICF3Br derived from Togni’s reagent II by
their method.14 When using other inorganic salt aqueous to
quench the reaction, all desired PhICF3X were completely
degraded during workup (entries 4−11, Table 2). PhI could be
detected in all cases. In the case of NaOTs, CF3OTs was
detected likely via the O-trifluoromethylation of NaOTs with
the in situ formed [PhICF3]+ (entry10, Table 2).
C
DOI: 10.1021/acs.orglett.8b01510
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trifluoromethylation.20,21 The incomplete inhibition of the
radical inhibitor on the reaction of 14b provided a proof of the
ionic character of the reaction mechanism (see the SI).
REFERENCES
■
(1) (a) Kirsch, P. Modern Fluoroorganic Chemistry; Wiley-VCH:
Weinheim, 2004. (b) Uneyama, K. Organofluorine Chemistry;
Blackwell Publishing: Oxford, 2006. (c) Theodoridis, G. Advances in
Fluorine Science; Tressaud, A., Ed.; Elsevier: Amsterdam, 2006; Vol. 2,
pp 121−175. (d) Begue, J.-P.; Bonnet-Delpon, D. Bioorganic and
Medicinal Chemistry of Fluorine; Wiley: Hoboken, NJ, 2008.
(e) Tressaud, A.; Haufe, G. Fluorine and Health: Molecular Imaging,
Biomedical Materials and Pharmaceuticals; Elsevier Science: Amster-
dam, 2008. (f) Ojima, I. Fluorine in Medicinal Chemistry and Chemical
Biology; Wiley: Chichester, U.K., 2009. (g) Egami, H.; Sodeoka, M.
Angew. Chem., Int. Ed. 2014, 53, 8294. (h) Merino, E.; Nevado, C.
Chem. Soc. Rev. 2014, 43, 6598.
(2) (a) Liu, X.; Xu, C.; Wang, M.; Liu, Q. Chem. Rev. 2015, 115,
683. (b) Prakash, G. K. S.; Mandal, M. J. Fluorine Chem. 2001, 112,
123. (c) Singh, R. P.; Shreeve, J. M. Tetrahedron 2000, 56, 7613.
(d) Prakash, G. K. S.; Yudin, A. K. Chem. Rev. 1997, 97, 757.
(e) Zhang, C. Adv. Synth. Catal. 2014, 356, 2895.
In conclusion, we prepared a noncyclic CF3-containing λ3-
iodane via a direct ligand-exchange reaction of PIFA, TMSCF3,
and NaCl for the first time. As new CF3 source, PhICF3Cl was
well used in various trifluoromethylation reactions. Its unique
CF3-delivering capability was also presented in trifluorome-
thylation−cyclization of aryl isocyanides under catalyst-free
conditions. Compared with neutral Togni reagents, it is the
iodonium character of 1a that endows it with an enhanced
electrophilicity in the CF3-transfer process. We believe that
easy availability and versatile usefulness of such low-cost
ArICF3X would provide new opportunities for helping the
continuing proliferation of CF3-containing compounds in
medicinal chemistry and biological chemistry. Investigations
on the expansion of the synthetic method and the utilization of
such kinds of CF3 reagents are in progress in our laboratory.
́
́
(3) (a) Shibata, N. Bull. Chem. Soc. Jpn. 2016, 89, 1307.
(b) Charpentier, J.; Fruh, N.; Togni, A. Chem. Rev. 2015, 115, 650.
̈
́
(c) Mace, Y.; Magnier, E. Eur. J. Org. Chem. 2012, 2012, 2479.
(d) Shibata, N.; Matsnev, A.; Cahard, D. Beilstein J. Org. Chem. 2010,
6, 65. (e) Ma, J.-A.; Cahard, D. J. Fluorine Chem. 2007, 128, 975.
(f) Umemoto, T. Chem. Rev. 1996, 96, 1757.
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.8b01510.
(4) (a) Yagupol'skii, L. M.; Kondratenko, N. V.; Timofeeva, G. N. J.
Org. Chem. USSR 1984, 20, 103. (b) Umemoto, T.; Ishihara, S. J. Am.
Chem. Soc. 1993, 115, 2156. (c) Umemoto, T.; Ishihara, S.; Adachi, K.
J. Fluorine Chem. 1995, 74, 77. (d) Umemoto, T.; Ishihara, S. J.
Fluorine Chem. 1999, 98, 75. (e) Magnier, E.; Blazejewski, J. C.;
Tordeux, M.; Wakselman, C. Angew. Chem., Int. Ed. 2006, 45, 1279.
(f) Umemoto, T.; Adachi, K.; Ishihara, S. J. Org. Chem. 2007, 72,
6905. (g) Yagupolskii, L. M.; Matsnev, A. V.; Orlova, R. K.;
Deryabkin, B. G.; Yagupolskii, Y. L. J. Fluorine Chem. 2008, 129, 131.
(h) Umemoto, T.; Zhang, B.; Zhu, T.-H.; Zhou, X.-C.; Zhang, P.; Hu,
S.; Li, Y.-Q. J. Org. Chem. 2017, 82, 7708.
(5) (a) Noritake, S.; Shibata, N.; Nakamura, S.; Toru, T.; Shiro, M.
Eur. J. Org. Chem. 2008, 2008, 3465. (b) Matsnev, A.; Noritake, S.;
Nomura, Y.; Tokunaga, E.; Nakamura, S.; Shibata, N. Angew. Chem.,
Int. Ed. 2010, 49, 572. (c) Saidalimu, I.; Tokunaga, E.; Shibata, N.
ACS Catal. 2015, 5, 4668.
Experimental procedures, analytical data for new
compounds, and crystallographic data for 1a (PDF)
Accession Codes
CCDC 1583041 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/data_request/cif, or by emailing
data_ request@ccdc.cam.ac.uk, or by contacting The Cam-
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB21EZ, UK; fax: + 44 1223 336033.
(6) Adachi, K.; Ishihara, S. Japan Tokkyo Kokai 2005, 145917.
(7) Liu, Y.; Shao, X.; Zhang, P.; Lu, L.; Shen, Q.-L. Org. Lett. 2015,
17, 2752.
(8) (a) Yagupolskii, L. M.; Maletina, I. I.; Kondratenko, N. V.; Orda,
V. V. Synthesis 1978, 1978, 835. (b) Umemoto, T.; Kuriu, Y.;
Shuyama, H.; Miyano, O.; Nakayama, S.-I. J. Fluorine Chem. 1982, 20,
695. (c) Umemoto, T.; Kuriu, Y.; Shuyama, H.; Miyano, O.;
Nakayama, S.-I. J. Fluorine Chem. 1986, 31, 37.
(9) Eisenberger, P. The Development of New Hypervalent Iodine
Reagents for Electrophilic Trifluoromethylation. Thesis, Eidgenossi-
sche Technische Hochschule, ETH Zurich, 2007.
(10) (a) Eisenberger, P.; Gischig, S.; Togni, A. Chem. - Eur. J. 2006,
12, 2579. (b) Kieltsch, I.; Eisenberger, P.; Togni, A. Angew. Chem., Int.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: wangm452@nenu.edu.cn.
ORCID
Cong Xu: 0000-0001-9817-7186
Xiaoning Song: 0000-0001-5507-8073
Yuxin Li: 0000-0003-1538-2868
Mang Wang: 0000-0001-8006-4626
Author Contributions
∥C.X. and X.S. contributed equally to this work.
̌
Ed. 2007, 46, 754. (c) Matousek, V.; Pietrasiak, E.; Schwenk, R.;
Togni, A. J. Org. Chem. 2013, 78, 6763.
Notes
(11) Chu, L.-L; Qing, F.-L. Org. Lett. 2012, 14, 2106.
(12) Xu, C.; Liu, J.-X.; Ming, W.-B.; Liu, Y.-J.; Liu, J.; Wang, M.; Liu,
Q. Chem. - Eur. J. 2013, 19, 9104.
(13) (a) Wang, H.-Y.; Xiang, Z.; Liu, G.-S.; Guo, Y.-L. J. Am. Soc.
Mass Spectrom. 2013, 24, 761. (b) Zhu, H.; Zhang, S.-S.; Wang, H.-Y.;
Xu, B.; Guo, Y.-L. Chin. J. Chem. 2015, 33, 1365.
(14) Brantley, J. N.; Samant, A. V.; Toste, F. D. ACS Cent. Sci. 2016,
2, 341.
(15) (a) Koller, R.; Huchet, Q.; Battaglia, P.; Welch, J. M.; Togni, A.
Chem. Commun. 2009, 5993. (b) Koller, R.; Stanek, K.; Stolz, D.;
Aardoom, R.; Niedermann, K.; Togni, A. Angew. Chem., Int. Ed. 2009,
48, 4332.
(16) Zheng, G.; Ma, X.-L.; Li, J.-H.; Zhu, D.-S.; Wang, M. J. Org.
Chem. 2015, 80, 8910.
The authors declare the following competing financial
interest(s): We have a patent pending on content relating to
this manuscript.
ACKNOWLEDGMENTS
■
We thank the National Natural Science Foundation of China
(21672032) and the Fundamental Research Funds for the
Central Universities (2412017QD013) for funding support of
this work. We also express sincere gratitude to Professor Qun
Liu, Northeast Normal University, for his constructive
suggestions.
D
DOI: 10.1021/acs.orglett.8b01510
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(17) (a) Li, L.; Chen, Q.-Y.; Guo, Y. J. Org. Chem. 2014, 79, 5145.
̌
(b) Katayev, D.; Matousek, V.; Koller, R.; Togni, A. Org. Lett. 2015,
17, 5898.
(18) (a) Wiehn, M. S.; Vinogradova, E. V.; Togni, A. J. Fluorine
Chem. 2010, 131, 951. (b) Shimizu, R.; Egami, H.; Nagi, T.; Chae, J.;
Hamashima, Y.; Sodeoka, M. Tetrahedron Lett. 2010, 51, 5947.
(c) Mejía, E.; Togni, A. ACS Catal. 2012, 2, 521.
(19) (a) Simeon, S.; Rios, J. L.; Villar, A. Pharmazie 1989, 44, 593.
(b) Phillips, S. D.; Castle, R. N. J. Heterocycl. Chem. 1981, 18, 223.
(c) Abdel-Halim, O. B.; Morikawa, T.; Ando, S.; Matsuda, H.;
Yoshikawa, M. J. Nat. Prod. 2004, 67, 1119.
(20) (a) Zhang, B.; Muck-Lichtenfeld, C.; Daniliuc, C. G.; Studer, A.
̈
Angew. Chem., Int. Ed. 2013, 52, 10792. (b) Zhang, B.; Studer, A. Org.
Lett. 2014, 16, 3990. (c) Liu, Y.-R.; Tu, H.-Y.; Zhang, X.-G. Synthesis
2015, 47, 3460. (d) Lu, S.-C.; Gong, Y.-L.; Zhou, D.-M. J. Org. Chem.
2015, 80, 9336. (e) Sakamoto, R.; Kashiwagi, H.; Selvakumar, S.;
Moteki, S. A.; Maruoka, K. Org. Biomol. Chem. 2016, 14, 6417.
(f) Cheng, Y.-Z.; Jiang, H.; Zhang, Y.; Yu, S.-Y. Org. Lett. 2013, 15,
5520. (g) Wang, R.-Z.; Jiang, H.; Cheng, Y.-Z.; Kadi, A. A.; Fun, H.-
K.; Zhang, Y.; Yu, S. Synthesis 2014, 46, 2711. (h) Tang, X.-Y.; Song,
S.; Liu, C.-B.; Zhu, R.-J.; Zhang, B. RSC Adv. 2015, 5, 76363.
(i) Rong, J.; Deng, L.; Tan, P.; Ni, C.-F.; Gu, Y.-C.; Hu, J.-B. Angew.
Chem., Int. Ed. 2016, 55, 2743. (j) Wang, Y.-X; Wang, J.-H.; Li, G.-X.;
He, G.; Chen, G. Org. Lett. 2017, 19, 1442.
(21) Kawamura, S.; Egami, H.; Sodeoka, M. J. Am. Chem. Soc. 2015,
137, 4865.
E
DOI: 10.1021/acs.orglett.8b01510
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