A redox-economical synthesis of trifluoromethylated enamides with the Langlois reagent

Article abstract of DOI:10.1039/c7ob00203c

A redox-economical strategy for the synthesis of trifluoromethylated enamides using copper catalysis is reported. The reaction employs the inexpensive Langlois reagent (CF₃SO₂Na) and takes place without the need of an external oxidant. The trifluoromethylated enamide products can easily be converted into the corresponding ketone, saturated amide or oxazole.

Full text of DOI:10.1039/c7ob00203c

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A Redox-Economical Synthesis of Trifluoromethylated Enamides
with the Langlois Reagent
Hai-Bin Yanga and Nicklas Selander*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
A
redox-economical strategy
for
the synthesis
of
a) Work by Loh:
trifluoromethylated enamides using copper catalysis is reported.
The reaction employs the inexpensive Langlois reagent (CF3SO2Na)
and takes place without the need of an external oxidant. The
trifluoromethylated enamide products can easily be converted
into the corresponding ketone, saturated amide or oxazole.
NHAc
NHAc
[CF3+], Cu(I)
CF3
O
R'
I
R
R
R
R'
CF3
b) Work by Gillaizeau:
O
R
[CF3+], Fe(II)
N
N
Togni's reagent II
N–O Bond-containing substrates have recently found great
applications in transition metal-catalyzed oxidative coupling
reactions.1 As the polarized N–O bond is reductively cleavable
by transition metals, the N–O bond can serve as an internal
oxidant in catalysis for the synthesis of valuable nitrogen-
containing products. By avoiding the excess of an added
oxidant, less waste is produced and the functional group
compatibility can be improved.2 The synthetically viable O-
acetyloximes have recently been investigated in transition
metal-catalyzed oxidative couplings.1d,1e,3 Their application as
internal oxidants for catalysis and in other transformations has
n
n
+
[CF3
]
c) Work by Liu:
NHCOR
CF3
NHCOR
[CF3+], cat. phosphine
CF3
H
CF3
d) This work:
NOR'
NHAc
CF3SO2Na
Cu(II)
Redox-economical
trifluoromethylation
R
R
-
strategy using [CF3
]
R' = Ac or H
CF3
been demonstrated by many groups for the synthesis of Scheme 1 Syntheses of trifluoromethylated enamides
dihydropyrroles, pyrroles, pyridines, isoquinolines, β-
ketosulfones, β-ketophosphonates and other important
building-blocks.3 However, to the best of our knowledge, the
internal oxidant strategy has not yet been applied in
trifluoromethylation reactions.
The same reagent was employed in an iron-catalyzed
trifluoromethylation of enamides by Gillaizeau and co-workers
(Scheme 1b).8 Furthermore, Liu and co-workers reported on a
phosphine-catalyzed
synthesis
of
trifluoromethylated
enamides via an olefinic trifluoromethylation (Scheme 1c).9
Despite these important contributions, methods for
preparing β-trifluoromethylated enamides using more stable
nucleophilic CF3 reagents (e.g., CF3SO2Na) have not been
developed. The initiation of a CF3 radical from nucleophilic CF3
reagents requires a stoichiometric oxidant.10 Furthermore,
enamides are usually prepared via a reductive acylation of
ketoximes with a stoichiometric reducing agent.11 Thus, with
the above-mentioned issues in mind, and in connection with
the use of oxime derivatives as internal oxidants, we envisaged
a direct synthesis of β-trifluoromethylated enamides. Herein,
we report a copper-catalyzed trifluoromethylation of ketoxime
acetates using CF3SO2Na via a presumed radical mechanism
(Scheme 1d). Compared to the trifluoromethylation of
enamides using Togni’s reagent II, our strategy would allow for
a more redox-economical pathway (Scheme 2).
Due to the special properties of fluorine (small atomic
radius and high electronegativity), trifluoromethylated
compounds play an important role for the pharmaceutical and
agrochemical industries.4 Consequently, the development of
practical and reliable methods for the introduction of the CF3-
substituent has recently attracted considerable attention.5 The
trifluoromethylation of olefins6-10 is an important and useful
route for the incorporation of the CF3-substituent. For
example, Loh and co-workers7 developed an elegant copper-
catalyzed trifluoromethylation reaction of enamides using
Togni’s reagent II (Scheme 1a).
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Raising the temperature to 100
°C allowed a shorter reaction
time with a comparable yield (61%, entry 16). The yield of 2a
dropped to 47% upon reducing the catalyst loading (10 mol%,
entry 17).12
Upon identification of suitable reaction conditions, we
turned to the scope of the reaction with respect to various
oxime acetates. When phenyl-substituted oxime acetate 1a
was employed, the trifluoromethylated enamide 2a was
obtained in 65% yield, by 19F NMR analysis of the crude
reaction mixture. On a 1.0 mmol scale, 2a was isolated in 57%
yield (E/Z ratio: 1.6:1). Due to the fluctuation of E/Z ratios over
Scheme 2 Strategies for enamide trifluoromethylation
time, we employed a hydrolysis step to convert enamides
2
We began our studies on the trifluoromethylation of oxime
into the corresponding ketones 3 for a more accurate
acetate
1 with the Langlois reagent (CF3SO2Na) as CF3-source.
determination of yields (Table 2). For various para-substituted
acetophenone oxime acetates, it was found that substrates
with electron-donating substituents reacted readily under the
However, no trifluoromethylated product was observed in the
complex reaction mixture that resulted. Lei and co-workers3p
recently demonstrated that the addition of acetic anhydride to
the copper-catalyzed α-phosphorylation of oxime acetates led
to improved yields. When acetic anhydride was employed as
standard conditions (Table 2, 1b
acetates with electron-withdrawing groups, the reaction had
to be conducted at 100 C (Table 2, 1d ). Carboxylic acid 3e
-c). However, for oxime
°
-f
an additive in the trifluoromethylation reaction, enamide
2
was obtained from the corresponding methyl ester 1e, which
was hydrolyzed in the second step. Both meta- and ortho-
substituted derivatives provided the trifluoro-methylated
ketones in good yields, with the exception of 3h (38% yield)
was obtained in 15% yield using 20 mol% of CuI (Table 1, entry
1). A brief screening of various copper catalysts showed that
CuF2 gave product
2 in the highest yield, 41%, as a 1:1 mixture
of E/Z isomers (Table 1, entries 2-6). No product was observed
with AgCl, FeCl2, Mn(OAc)2, or in the absence of a catalyst.12
Upon changing solvent (entries 7-10) and acylation reagent
(entries 11-12), improved yields were observed for MeCN in
combination with acetic anhydride. A further improvement
was observed upon dilution (61%, entry 14) and when 1.5
equiv of Ac2O was used (65%, entry 15).
which required an elevated temperature (Table 2, 3g-i). The
naphthyl-substituted oxime acetate 1j furnished product 3j in
50% yield, whereas the furyl derivative 1k gave a modest yield
(28%), probably due to coordination to the catalyst (Table 2,
3k). Upon extension of the alkyl chain (1l), a low reactivity was
observed; ketone 3l was obtained in only 14% yield. This is
consistent with previous findings in the Cu-catalyzed
Table 1 Screeening of reaction parametersa
Table 2 Substrate scope for various oxime acetatesa
NHAc
catalyst (20 mol%)
Ac2O (1.0 equiv)
NOR
CF3SO2Na
Ph
solvent (1 mL), 80 o
C
Ph
Langlois reagent
1
2a CF3
Entry 1, R
Catalyst
Solvent
Time (h) Yield (%) E/Z
1a, Ac
CuI
1
1,4-dioxane 24
24
15
24
32
30
22
41
38
33
17
0
1.4:1
1a, Ac
1a, Ac
1a, Ac
1a, Ac
1a, Ac
1a, Ac
1a, Ac
1a, Ac
1a, Ac
1b, Piv
1c, Bz
1a, Ac
1a, Ac
1a, Ac
1a, Ac
1a, Ac
CuTc
2
1,4-dioxane
1.4:1
1.1:1
1.3:1
1.0:1
1.0:1
1.8:1
1.9:1
1.8:1
-
3
Cu(OAc)2 1,4-dioxane 72
4
CuCl2
CuBr2
CuF2
CuCl2
CuCl2
CuCl2
CuCl2
CuCl2
CuCl2
CuF2
CuF2
CuF2
CuF2
CuF2
1,4-dioxane 24
1,4-dioxane 24
1,4-dioxane 24
5
6
CH3CN
DCE
7
24
24
24
24
24
24
24
48
48
24
48
8
9
PhMe
10
11
12
13
14b
15c
16d
17e
DMSO
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
28
34
51
61
65
61
47
2.1:1
1.8:1
2.0:1
1.5:1
1.6:1
1.6:1
1.9:1
a Step 1:
(0.04 mmol) were stirred in MeCN (4 mL) under Ar for 48 h at 80
1
(0.20 mmol), CF3SO2Na, (0.30 mmol), Ac2O (0.30 mmol) and CuF2
C. Step 2:
°
(after purification) was dissolved in 2 M aq. HCl (1 mL) and 1,4-
Product
dioxane (1 mL), the mixture was stirred for 2 h at 80
2
b
C. Yields were
°
determined by 19F NMR (E/Z mixtures). Isolated yields. Isolated yield,
c
d
a
Reaction conditions:
mmol) and Ac2O (0.20 mmol) in 1.0 mL solvent at 80
1
(0.20 mmol), CF3SO2Na (0.30 mmol), catalyst (0.04
C. NMR yields are
step 1 was performed on a 0.5 mmol scale (1.0 mmol for 1a) at 80
f
°
C for 72
e
h. Step 1 conditions: 24 h at 100
°
°C. Step 2 reaction time: 24 h, ester
b
c
d
given. 4.0 mL MeCN was used. With 0.30 mmol Ac2O. Carried out at
100 °C. e With 10 mol% catalyst. DCE = 1,2-dichloroethane.
hydrolysis occurred. See the Supporting Information for full details.
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phosphorylation and sulfinylation of oxime acetates.3n,3p
Another limitation of the method is the longer carbon chain
derivatives, e.g., the ethyl-analog of oxime acetate 1a, which
only resulted in trace amounts of product.
Moreover, we found that oxime 4a can be directly
employed as a starting material in a domino acetylation/
trifluoromethylation sequence to afford 2a in 59% yield (E/Z
ratio 1.7:1, Scheme 3).
To demonstrate the synthetic utility of the method, CF3-
containing enamide 2a was subjected to subsequent
transformations. The Ni-mediated reduction of 2a provided
the saturated amide 5a in 61% yield. Furthermore, an
oxidative cyclization of 2a with PIFA led to oxazole 6a in 53%
yield (Scheme 4).9
Based on the proposed mechanisms for the α-
phosphorylation of oxime acetates,3p and the reductive
acylation of ketoximes,11b two possible mechanistic pathways
involving radical species were envisioned for the
trifluoromethylation reaction:
path, and radical/radical coupling path. In the
radical/enamide path (path a, Scheme 5), oxime acetate is
reduced to enamide in the presence of CuF2, CF3SO2Na and
Ac2O. In the same process, a CF3 radical ( ) is generated by
reduction of the copper(II) species, followed by N–O bond
a radical/enamide addition
Scheme 5 Proposed reaction mechanisms
a
1
7
I
cleavage.11b The trifluoromethylated enamide
through the addition of radical to enamide
2
is then formed
I
7 followed by an
Scheme 6 Trifluoromethylation of enamide 7
oxidation of intermediate II to regenerate Cu(II). Alternatively,
in a radical/radical coupling path (path b, Scheme 5), oxime
However, the addition of enamide 7a to
a
acetate
isomerization of III to IV, followed by a coupling with CF3
radical (formed by reduction of a Cu(III)-species) and
acylation, product is formed.
To probe for mechanistic insights, we conducted a couple
of control experiments. First, the trifluoromethylation of was
1 is reduced by CuF2 to imine radical III. Upon
trifluoromethylation reaction of another oxime acetate (1c) led
to an increased yield; 26% of ketone 3a was obtained after
hydrolysis.12 Thus, we concluded that 7a would be a viable
intermediate (supporting a radical/enamide path) in the
catalytic trifluoromethylation reaction, and that the N-O bond
I
2
1
of
1 is important for a catalytic turnover. Furthermore, no
completely suppressed by the addition of TEMPO, indicating
the presence of productive radical species.12 Second, the
reaction took place in the absence of CF3SO2Na. This
observation suggests that this reagent also plays a crucial role
as a reductant for the formation of an enamide intermediate
involvement of enamide
investigated: Upon treating enamide 7a with the Langlois
reagent and CuF2 at 100 C for 24 h, only 15% of 2a was
7 as a reaction intermediate was
(e.g. 7a).11b Additional support for the enamide intermediate
7
1
was given by monitoring the reaction progress by H and 19F
NMR. In the trifluoromethylation of 1a, enamide 7a was
detected prior to product 2a, and maintained at a steady
concentration until completely consumed. The NMR
experiments also showed a gradual E to Z isomerization of the
product over time.12
°
obtained along with the hydrolysis product (Scheme 6).
Scheme 3 Domino transformation of oxime 4a
Conclusions
In conclusion,
a
redox-economical13 Cu-catalyzed
trifluoromethylation reaction of oxime acetates was
developed. By employing the cheap and practical Langlois
reagent, the method provides ready access to
trifluoromethylated enamides in the absence of an external
oxidant. The enamide products were transformed into the
corresponding trifluoromethylated ketones after hydrolysis, or
into the amide and oxazole in a single step. The reaction is
Scheme 4 Transformations of enamide 2a
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Zhou, J. Wang, Z. Gu, S. Wang, W. Zhu, J. L. Acena, V. A.
Soloshonok, K. Izawa and H. Liu, Chem. Rev. 2016, 116, 422.
For reviews, see: (a) C. Alonso, E. Martínez de Marigorta, G.
Rubiales and F. Palacios, Chem. Rev. 2015, 115, 1847; (b) J.
likely to proceed via addition of a CF3-radical to an acetylated
enamine intermediate.
5
6
Charpentier, N. Früh and A. Togni, Chem. Rev. 2015, 115
,
Acknowledgments
650; (c) X. Liu, C. Xu, M. Wang and Q. Liu, Chem. Rev. 2015,
115, 683; (d) C. Zhang, Adv. Synth. Catal. 2014, 356, 2895; (e)
A. Studer, Angew. Chem, Int. Ed. 2012, 51, 8950.
This work was supported by the Swedish Research Council
(VR), the Carl Trygger Foundation, and the Wenner-Gren
Foundation.
For representative examples, see (a) B. Yang, X.-H. Xu and F.-
L. Qing, Org. Lett. 2015, 17, 1906; (b) X.-J. Tang and W. R.
Dolbier, Angew. Chem. Int. Ed. 2015, 54, 4246; (c) Z. Feng,
Q.-Q. Min, H.-Y. Zhao, J.-W. Gu and X. Zhang, Angew. Chem.
Int. Ed. 2015, 54, 1270; (d) H. Egami, Y. Usui, S. Kawamura, S.
Nagashima and M. Sodeoka, Chem. Asian J. 2015, 10, 2190;
(e) F. Wang, D. Wang, X. Mu, P. Chen and G. Liu, J. Am. Chem.
Soc. 2014, 136, 10202; (f) T. Xu, C. W. Cheung and X. Hu,
Angew. Chem. Int. Ed. 2014, 53, 4910; (g) R. Zhu and S. L.
Buchwald, Angew. Chem. Int. Ed. 2013, 52, 12655; (h) X. Wu,
L. Chu and F.-L. Qing, Angew. Chem. Int. Ed. 2013, 52, 2198;
(i) S. Mizuta, S. Verhoog, K. M. Engle, T. Khotavivattana, M.
O’Duill, K. Wheelhouse, G. Rassias, M. Médebielle and V.
Gouverneur, J. Am. Chem. Soc. 2013, 135, 2505; (j) J. M.
Larsson, S. R. Pathipati and K. J. Szabó, J. Org. Chem. 2013,
78, 7330; (k) W. Kong, M. Casimiro, E. B. Merino and C.
Nevado, J. Am. Chem. Soc. 2013, 135, 14480; (l) C. Feng and
T.-P. Loh, Angew. Chem. Int. Ed. 2013, 52, 12414; (m) H.
Egami, R. Shimizu, S. Kawamura and M. Sodeoka, Angew.
Chem. Int. Ed. 2013, 52, 4000; (n) H. Egami, S. Kawamura, A.
Notes and references
1
For representative examples, see: (a) K. Parthasarathy, M.
Jeganmohan and C.-H. Cheng, Org. Lett. 2008, 10, 325; (b) J.
Wu, X. Cui, L. Chen, G. Jiang and Y. Wu, J. Am. Chem. Soc.
2009, 131, 13888; (c) T. Gerfaud, L. Neuville and J. Zhu,
Angew. Chem, Int. Ed. 2009, 48, 572; (d) Y. Tan and J. F.
Hartwig, J. Am. Chem. Soc. 2010, 132, 3676; (e) P. C. Too, Y.-
F. Wang and S. Chiba, Org. Lett. 2010, 12, 5688; (f) N.
Guimond, S. I. Gorelsky and K. Fagnou, J. Am. Chem. Soc.
2011, 133, 6449; (g) S. Rakshit, C. Grohmann, T. Besset and F.
Glorius, J. Am. Chem. Soc. 2011, 133, 2350; (h) T. K. Hyster
and T. Rovis, Chem. Commun. 2011, 47, 11846; (i) R. M.
Martin, R. G. Bergman and J. A. Ellman, J. Org. Chem. 2012,
77, 2501; (j) K. M. M. Huihui, J. A. Caputo, Z. Melchor, A. M.
Olivares, A. M. Spiewak, K. A. Johnson, T. A. DiBenedetto, S.
Kim, L. K. G. Ackerman and D. J. Weix, J. Am. Chem. Soc.
2016, 138, 5016; (k) J. Cornella, J. T. Edwards, T. Qin, S.
Kawamura, J. Wang, C.-M. Pan, R. Gianatassio, M. Schmidt,
Miyazaki and M. Sodeoka, Angew. Chem. Int. Ed. 2013, 52
,
7841; (o) R. Zhu and S. L. Buchwald, J. Am. Chem. Soc. 2012,
134, 12462; (p) Y. Yasu, T. Koike and M. Akita, Angew. Chem.
Int. Ed. 2012, 51, 9567; (q) R. Shimizu, H. Egami, Y.
M. D. Eastgate and P. S. Baran, J. Am. Chem. Soc. 2016, 138
,
2174.
(a) V. Khlestkin and D. Mazhukin, Curr. Org. Chem. 2003, 7,
967; (b) C. Liu, J. Yuan, M. Gao, S. Tang, W. Li, R. Shi and A.
Lei, Chem. Rev. 2015, 115, 12138.
Hamashima and M. Sodeoka, Angew. Chem. Int. Ed. 2012,
51, 4577; (r) S. Mizuta, O. Galicia-López, K. M. Engle, S.
Verhoog, K. Wheelhouse, G. Rassias and V. Gouverneur,
Chem. Eur. J. 2012, 18, 8583; (s) L. Chu and F.-L. Qing, Org.
Lett. 2012, 14, 2106; (t) J. Xu, Y. Fu, D.-F. Luo, Y.-Y. Jiang, B.
Xiao, Z.-J. Liu, T.-J. Gong and L. Liu, J. Am. Chem. Soc. 2011,
133, 15300; (u) X. Wang,; Y. Ye, S. Zhang, J. Feng, Y. Xu, Y.
Zhang and J. Wang, J. Am. Chem. Soc. 2011, 133, 16410; (v)
A. T. Parsons and S. L. Buchwald, Angew. Chem. Int. Ed. 2011,
50, 9120.
C. Feng and T.-P. Loh, Chem. Sci. 2012, 3, 3458.
R. Rey-Rodriguez, P. Retailleau, P. Bonnet and I. Gillaizeau,
Chem. Eur. J. 2015, 21, 3572.
P. Yu, S.-C. Zheng, N.-Y. Yang, B. Tan and X.-Y. Liu, Angew.
Chem. Int. Ed. 2015, 54, 4041.
2
3
(a) K. Takai, N. Katsura and Y. Kunisada, Chem. Commun.
2001, 1724; (b) Y. Koganemaru, M. Kitamura and K.
Narasaka, Chem. Lett. 2002, 784; (c) M. Yoshida, M. Kitamura
and K. Narasaka, Bull. Chem. Soc. Jpn. 2003, 76, 2003; (d) S.
Liu and L. S. Liebeskind, J. Am. Chem. Soc. 2008, 130, 6918;
(e) P. C. Too, S. H. Chua, S. H. Wong and S. Chiba, J. Org.
Chem. 2011, 76, 6159; (f) Z.-H. Ren, Z.-Y. Zhang, B.-Q. Yang,
Y.-Y. Wang and Z.-H. Guan, Org. Lett. 2011, 13, 5394; (g) A.
John and K. M. Nicholas, Organometallics 2012, 31, 7914; (h)
Y. Wei and N. Yoshikai, J. Am. Chem. Soc. 2013, 135, 3756; (i)
M. Bingham, C. Moutrille and S. Z. Zard, Heterocycles 2014,
7
8
9
88, 953; (j) Q. Wu, Y. Zhang and S. Cui, Org. Lett. 2014, 16
,
10 (a) Q. Lu, C. Liu, Z. Huang, Y. Ma, J. Zhang and A. Lei, Chem.
Commun. 2014, 50, 14101; (b) X.-Y. Jiang and F.-L. Qing,
Angew. Chem. Int. Ed. 2013, 52, 14177; (c) A. Deb, S. Manna,
A. Modak, T. Patra, S. Maity and D. Maiti, Angew. Chem. Int.
Ed. 2013, 52, 9747; (d) B. R. Langlois, E. Laurent and N.
Roidot, Tetrahedron Lett. 1992, 33, 1291.
11 (a) W. Tang, Z. Cai, G. Liu, G. Jiao and C. Senanayake,
Synthesis 2013, 45, 3355; (b) Z.-H. Guan, Z.-Y. Zhang, Z.-H.
Ren, Y.-Y. Wang and X. Zhang, J. Org. Chem. 2011, 76, 339;
(c) Z.-H. Guan, K. Huang, S. Yu and X. Zhang, Org. Lett. 2009,
11, 481; (d) C. Sun and S. M. Weinreb, Synthesis 2006, 3585.
12 See the Supporting Information for further details.
13 N. Z. Burns, P. S. Baran and R. W. Hoffmann, Angew. Chem.
Int. Ed. 2009, 48, 2854.
1350; (k) W. Du, M.-N. Zhao, Z.-H. Ren, Y.-Y. Wang and Z.-H.
Guan, Chem. Commun. 2014, 50, 7437; (l) M.-N. Zhao, R.-R.
Hui, Z.-H. Ren, Y.-Y. Wang and Z.-H. Guan, Org. Lett. 2014,
16, 3082; (m) A. Faulkner, N. J. Race, J. S. Scott and J. F.
Bower, Chem. Sci. 2014,
J. Yang, W. Wu and H. Jiang, Angew. Chem. Int. Ed. 2014, 53
5, 2416; (n) X. Tang, L. Huang, Y. Xu,
,
4205; (o) X. Tang, L. Huang, J. Yang, Y. Xu, W. Wu and H.
Jiang, Chem. Commun. 2014, 50, 14793; (p) J. Ke,; Y. Tang, H.
Yi, Y. Li, Y. Cheng, C. Liu and A. Lei, Angew. Chem. Int. Ed.
2015, 54, 6604; (q) H. Su, W. Li, Z. Xuan and W. Yu, Adv.
Synth. Catal. 2015, 357, 64; (r) H. Huang, J. Cai, X. Ji, F. Xiao,
Y. Chen and G.-J. Deng, Angew. Chem. Int. Ed. 2016, 55, 307;
(s) H. Huang, J. Cai, L. Tang, Z. Wang, F. Li and G.-J. Deng, J.
Org. Chem. 2016, 81, 1499.
4
For reviews, see: (a) S. Purser, P. R. Moore, S. Swallow and V.
Gouverneur, Chem. Soc. Rev. 2008, 37, 320; (b) J. Wang, M.
Sánchez-Roselló, J. L. Aceña, C. del Pozo, A. E. Sorochinsky, S.
Fustero, V. A. Soloshonok and H. Liu, Chem. Rev. 2014, 114
,
2432; (c) T. Fujiwara and D. O’Hagan, J. Fluorine Chem. 2014,
167, 16; (d) E. P. Gillis, K. J. Eastman, M. D. Hill, D. J. Donnelly
and N. A. Meanwell, J. Med. Chem. 2015, 58, 8315; (e) Y.
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