Discovery of flufenoxystrobin: Novel fluorine-containing strobilurin fungicide and acaricide

Article abstract of DOI:10.1016/j.jfluchem.2016.03.013

To discover new strobilurin analogues with high activity, a series of new fluorine-containing strobilurin derivatives were synthesized utilizing intermediate derivatization methods (IDM). The compounds were identified by ¹H and ¹⁹F n

Full text of DOI:10.1016/j.jfluchem.2016.03.013

Journal of Fluorine Chemistry 185 (2016) 173–180
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Discovery of flufenoxystrobin: Novel fluorine-containing strobilurin
fungicide and acaricide
Lin Lia,b, Miao Lic, Huiwei Chic, Jichun Yangc, Zhinian Lic, Changling Liuc,
*
a
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, China
Department of Pharmaceutical Chemistry, Hebei Medical University, Shijiazhuang, China
b
c
State Key Laboratory of the Discovery and Development of Novel Pesticides, Shenyang sinochem agrochemicals R&D Co., Ltd., Shenyang, China
A R T I C L E I N F O
A B S T R A C T
Article history:
To discover new strobilurin analogues with high activity, a series of new fluorine-containing strobilurin
derivatives were synthesized utilizing intermediate derivatization methods (IDM). The compounds were
identified by 1H and 19F nuclear magnetic resonance (NMR), IR and elemental analysis. Preliminary
bioassays in greenhouse indicated that compounds 2a (SYP-3759, flufenoxystrobin) and 2c exhibited
excellent fungicidal activities against Erysiphe graminis protecting wheat at 1.56 mg Lꢀ1 concentration
and compounds 2a showed a moderately high acaricidal activity at 10 mg Lꢀ1. Field trials showed the
fungicidal activities of compounds 2a and 2c is almost equivalent to that of pyraclostrobin, higher than
that of triadimefon and the acaricidal activity of compound 2a is almost equivalent to that of pyidaben,
but lower than that of fluacrypyrim. The preliminary mammalian toxicology results showed compound
2a was a low-toxicity compound. In conclusion compound 2a is a promising candidate for further
development; mammalian toxicology and ecotoxicology with compound 2a are in progress.
ã 2016 Elsevier B.V. All rights reserved.
Received 19 February 2016
Received in revised form 24 March 2016
Accepted 24 March 2016
Available online 24 March 2016
Keywords:
Flufenoxystrobin
Strobilurin derivatives
Fungicidal activity
Acaricidal activity
Structure-activity relationship
Intermediate derivatization methods
1. Introduction
acaricidal fluacrypyrim as shown in Fig. 1. The candidate structure
(1) encompasses the strobilurin moieties, “methyl (E)-
b-methox-
The strobilurins are known as one of the most important classes
of agricultural fungicides with broad fungicidal spectrum, lower
toxicity towards mammalian cells and environmentally benign
characteristics. Although many strobilurin fungicides have already
been commercialized, we postulated that new strobilurin ana-
logues could be discovered using the Intermediate Derivatization
Methods (IDM), a useful three-pronged approach for agrochemical
discovery that includes the Common Intermediate Method (CIM),
Terminal Group Replacement Method (TRM), and the Active
Compound Derivatization Method (ADM) [1–16]. In this paper, we
present our results from the application of TRM to generate new
strobilurin derivatives.
yacrylate”, “methyl (E)-methoxyiminoacetate”,
“N-methyl
(E)-methoxyiminoacetamide” and “methyl N-methoxycarbamate”,
and the meta-trifluoromethyl substituted phenol in the side chain.
3-Trifluoromethylphenol is also an important intermediate in
synthesis of herbicides picolinafen and diflufenican. Therefore, we
hypothesized that the 3-trifluoromethyl phenol moiety and the
strobilurin moieties are two critical components in their activities
and by replacing the pyridine or pyrimidine moiety in picox-
ystrobin and fluacrypyrim with 3-trifluoromethylphenol would
improve their biological activities further (see Fig. 1). Using this
approach, we synthesized a number of compounds of the type 1
and screened them for fungicidal activity.
The strobilurin derivatives containing meta-trifluoromethyl
substituted phenyl, pyridine and pyrimidine in the side chain
display excellent fungicidal and acaricidal activity, such as
fungicides picoxystrobin [17] and acaricide fluacrypyrim [18]. In
order to discover new strobilurin analogues with higher biological
activity, we initially designed general structure (1) by combining
structural components taken from highly potent picoxystrobin and
In order to further optimize our lead compound (1), we
observed that the diphenyl ether herbicides fomesafen, oxy-
fluorfen, lactofen, acifluorfen, ethoxyfen-ethyl and fluoroglycofen-
ethyl each share the 2-chloro-4-(trifluoromethyl)phenol (7a)
moiety which is by-product in synthesis process of oxyfluorfen
(Figs. 2 and 3). Our next step was to replace the 3-trifluorome-
thylphenol moiety in the designed structure (1) with the 2-chloro-
4-(trifluoromethyl)phenol moiety, common to the above listed
herbicides, to obtain compounds shown as design structure (2)
[19]. We also prepared similar analogues with pyridine as shown in
design structure (3).
* Corresponding author.
E-mail address: liuchangling@vip.163.com (C. Liu).
http://dx.doi.org/10.1016/j.jfluchem.2016.03.013
0022-1139/ã 2016 Elsevier B.V. All rights reserved.

174
L. Li et al. / Journal of Fluorine Chemistry 185 (2016) 173–180
Fig. 1. Design of skeleton.
A series of new strobilurin derivatives containing phenyl and
respective crops as compared to such standard fungicides as
azoxystrobin, kresoxim-methyl and pyraclostrobin (Fig. 4). In
addition to its strong fungicidal activity, compound 2a (SYP-3759,
flufenoxystrobin) exhibits an acaricidal activity against Tetranychus
pyridine in the side chain were synthesized and bioassayed. We
have found that some compounds display an excellent fungicidal
activity against Erysiphe graminis (E. graminis) protecting
Fig. 2. Agrochemicals containing 2-chloro-4-trifluoromethylphenol.

L. Li et al. / Journal of Fluorine Chemistry 185 (2016) 173–180
175
Fig. 3. Synthesis routes of oxyfluorfen and by-product (7a).
cinnabarinus (T. cinnabarinus) comparable with the reference
2.3. Discovery of the lead compounds 1a and 2a
acaricides fluacrypyrim and pyridaben (Fig. 4). Compound 2a is a
promising candidate for further development.
Considering that many fluorine-containing compounds exhibit
significant agricultural bioactivities, owing to the unique proper-
ties of the fluorine atom, such as high thermal stability and
lipophilicity, 3-trifluoromethylphenol and 2-chloro-4-(trifluoro-
methyl)phenol were introduced into strobilurin derivatives to
obtain compounds 1a and 2a, respectively. Both compounds
exhibited good activities against E. graminis, particularly com-
pound 2a with 2-chloro-4-trifluoromethyl-phenol substituent
displayed significant control of 100% against E. graminis at
1.56 mg Lꢀ1, much higher than azoxystrobin (Table 2). Encouraged
by this finding, it was decided to make further structural
modifications around these two lead compounds 1a and 2a in
order to discover new compounds with higher activity.
2. Results and discussion
2.1. Synthesis
According to the Schemes 1–3 , strobilurin derivatives were
synthesized generally in good yield of 70–90%, as shown in Table 1
(for meta-CF3-phenol analogues 1a-1i), Table
substituted-phenol 2a–2k) and Table 3 (for substituted pyridin-
2-ol 3a–3f). The synthesized compounds were characterized by
1H NMR, 19F NMR, IR and elemental analyses. All spectral and
analytical data were consistent with the assigned structures.
2 (for other
2.2. Fungicidal activity
2.4. Optimization of compound 1a
The fungicidal activity of the above compounds against E.
graminis in vivo was deter-mined at the concentration ranging
from 0.39 to 25 mg/L, using azoxystrobin, kresoxim-methyl and
pyraclostrobin which is the similar structure in the series as the
reference standards, in accordance to the methods described in
Section 3.2 and the results are listed in Tables 1–3. Some of the
synthesized compounds exhibited potential activity against
E. graminis. Compounds 2a–2c, having strong electron withdraw-
ing group CF3 on 4-position displayed best fungicidal activity (85,
80 and 85% respectively control at 0.39 mg/L), much higher than
azoxystrobin, kresoxim-methyl and pyraclostrobin (30, 0 and 70%
at 0.39 mg/L).
Using compound 1a as lead compound for further optimization,
we turned our attention to introducing the Cl atom on the 2, 4 and
6 positions of 3-CF3-phenyl ring. First, we introduced the Cl atom
on the 2 position and kept the 4 and 6 positions fixed as H. We
synthesized two compounds 1b with Q1 and 1c with
Q2 respectively. The bioassay results showed that compounds
1b and 1c were less efficacious than lead compound 1a (60 and
65 versus 100% at 25 mg Lꢀ1), indicating that introducing the Cl
atoms on the 2 position has a negative effect on bioactivity. Then,
we introduced the Cl atom on the 4 position and kept the 2 and
6 positions fixed as H. We synthesized three compounds 1d,1e and
1f with Q1, Q2 and Q3 respectively. To our surprise, compounds
Fig. 4. Reference compounds.

176
L. Li et al. / Journal of Fluorine Chemistry 185 (2016) 173–180
Scheme 1. Synthesis schemes of compound 1.
Scheme 2. Synthesis schemes of compound 2.
Scheme 3. Synthesis schemes of compound 3.

L. Li et al. / Journal of Fluorine Chemistry 185 (2016) 173–180
177
Table 1
Physical properties and fungicidal activity against E. graminis of meta-substituted-phenol analogues 1.
Compound
R1
R2
R3
Q
mp. (ꢁC)
Yield
(%)
% control at given concentration mg Lꢀ1
25
6.25
1.56
0.39
1a
1b
1c
1d
1e
1f
1g
1h
H
Cl
Cl
H
H
H
H
H
H
H
H
H
Cl
Cl
Cl
H
H
H
H
H
H
H
H
H
Cl
Cl
Cl
Q1
Q1
Q2
Q1
Q2
Q3
Q1
Q2
Q3
oil
71.6
70.5
75.3
76.1
74.9
75.6
73.4
73.2
88.5
100
60
65
60
0
20
78
90
100
82
50
0
0
40
0
0
84-86
100ꢀ102
oil
oil
oil
72-78
92-94
132ꢀ134
100
100
100
100
90
100
100
100
100
70
60
80
50
0
70
60
40
100
20
15
30
10
0
30
30
0
45
1i
100
100
98
Azoxystrobin
Kresoxim-methyl
Pyraclostrobin
100
70
1d–1f exhibited 60–80% control of E. graminis at 1.56 mg Lꢀ1. All of
these compounds were more efficacious than compound 1a which
only showed 50% control at 1.56 mg Lꢀ1 and nearly equivalent to or
a little higher than that of azoxystrobin and kresoxim-methyl
which gave 60 and 40% control respectively at 1.56 mg Lꢀ1. Finally,
we introduced the Cl atom on the 6 position and kept the 2 and
4 positions fixed as H and synthesized three compounds 1g,1h and
1i with Q1, Q2 and Q3 respectively. The fungicidal activity results
showed that compound 1i was more efficacious than the other
compounds 1g, 1h, lead compound 1a and azoxystrobin at
1.56 mg Lꢀ1, but lower than compound 1f which share the same
moiety Q3. Based on the structure-potency data, introducing the Cl
atom on the 4 position (compounds 1d–1f) are most potent among
2, 4 and 6 position of phenyl. The sequence of the substituents R1,
R2 and R3 of meta-CF3-phenyl are 4-Cl (R2 = Cl) > 6-Cl (R3 = Cl) > 2-Cl
(R1 = Cl) and the sequence of the substituent Q is Q3 > Q2 and Q1.
2.5. Optimization of compound 2a
2-Chloro-4-(trifluoromethyl)phenol is an important interme-
diate as introduced above, so we fixed 2-chloro-4-(trifluoro-
methyl)phenol moiety and replaced Q1 with Q2, Q3 and Q4 to
obtain compounds 2b, 2c and 2d. Fortunately, the results showed
that compounds 2b and 2c exhibited better activities than 2d and
similar to compound 2a, which displayed significant control of
100% against E. graminis at 1.56 mg Lꢀ1 (Table 2). More importantly,
Table 2
Physical properties and fungicidal activity against E. graminis of para-substituted-phenol analogues 2.
Compound
R4
R5
R6
Q
mp.
(ꢁC)
Yield
(%)
% control at given concentration mg Lꢀ1
25
6.25
1.56
0.39
2a
2b
2c
2d
2e
2f
2g
2h
CF3
CF3
CF3
CF3
CH3
CH3
CH3
CN
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Br
H
H
H
H
H
H
H
H
H
Cl
Br
H
Q1
Q2
Q3
Q4
Q1
Q2
Q3
Q1
Q1
Q1
Q1
104–106
115–116
92–94
oil
oil
oil
70.8
72.9
87.5
71.3
72.3
75.6
80.1
75.6
77.3
73.4
70.8
100
100
100
100
100
100
100
100
50
100
100
100
95
85
95
40
100
0
20
50
100
100
100
65
50
60
20
15
0
85
80
85
10
40
20
0
0
0
0
0
oil
86–88
84–86
94–96
98–100
2i
2j
2k
CN
CN
NO2
60
90
0
0
Azoxystrobin
Kresoxim-methyl
Pyraclostrobin
100
100
100
100
98
100
60
40
100
30
0
70

178
L. Li et al. / Journal of Fluorine Chemistry 185 (2016) 173–180
Table 3
Physical properties and fungicidal activity against E. graminis of pyridinol analogues 3.
Compound
R7
R8
R9
Q
mp.
(ꢁC)
Yield
(%)
% control at given concentration mg Lꢀ1
25
6.25
1.56
0.39
3a
3b
3c
3d
3e
3f
Cl
Cl
Cl
Cl
Cl
Cl
CF3
CF3
CF3
Cl
Cl
Cl
H
H
H
Cl
Cl
Cl
Q1
Q2
Q3
Q1
Q2
Q3
108–110
107–109
103–105
96–98
89–91
88–90
74.8
73.5
76.4
72.8
74.1
71.9
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
100
98
90
90
80
100
100
98
60
40
40
30
20
40
45
20
30
0
Azoxystrobin
Kresoxim-methyl
Pyraclostrobin
100
100
70
compounds 2a–2c showed better fungicidal activity than the
commercial fungicides azoxystrobin and kresoxim-methyl at
0.39 mg Lꢀ1 (85, 80 and 85% respectively, versus 30, 0 and 70%
for azoxystrobin, kresoxim-methyl and pyraclostrobin). Therefore,
compounds 2a and 2c could be selected as the promising candidate
for further commercial development. We next considered chang-
ing the substituent CF3 of compound 2a to CH3 (compounds 2e–
2g), unfortunately these compounds did not exhibit excellent
bioactivity compared with the compounds containing substituent
CF3 according to the pairs of 2a and 2e, 2b and 2f, 2c and 2g.
Because the activities were measured in vivo, effects of
metabolism and/or biotransformation inside the bodies of plant/
fungus and acarids result in the apparent potency variations. The
inference that the electron-withdrawing substituents of the
phenyl moiety may enhance the potency could be related to the
fact that they tend to retard mechanisms of oxidative metabolism
occurring on (or close to) the benzene ring [20,21]. The higher the
electronic (negative) charge within the ring system, the easier
would occur such an oxidative detoxication metabolism as
hydroxylation of the benzene ring. So we introduced strong
electronic group CN (2h–2j) and NO2 (2k) into the phenyl ring in
order to discover higher active compound, but these compounds
did not show more efficacious than compounds 2a–2c as expected.
On the whole, under equivalent dosage (25 mg Lꢀ1) most of the
strobilurin derivatives containing meta and para-substituted
phenol show 100% control against E. graminis but their fungicidal
activity varies in the lower concentrations. Generally, meta-CF3-
phenol analogues in Table 1 (R1 = Cl) seem to be less potent than
corresponding para-CF3-phenol analogues in Table 2 (R4 = CF3)
sharing common substituted Cl, for example the pair of meta and
para-CF3-phenol analogues 1b and 2a, 1c and 2b.
E. graminis in 2008 as summarized in Table 4. The fungicidal
activities of compounds 2a and 2c as 20% suspension concentrate
(SC) is almost equivalent to that of pyraclostrobin as 25% SC at
equivalent doses, and higher than that of triadimefon as 15%
wettable powder (WP) at 135 mg Lꢀ1
.
2.7. Acaricidal activity and field trials with compound 2a
The target compounds were tested for control of T. cinnabarinus,
however the compounds showed no acaricidal activity at 600 mg
Lꢀ1 dosages except compounds 2a and 2d which exhibited 100%
mortality. As indicated in Table 5, compound 2a was further tested
for control of T. cinnabarinus and showed a moderately high
acaricidal activity at 10 mg Lꢀ1, similar to the reference acaricide
fluacrypyrim.
Field trials were carried out in Pulandian, Liaoning Province in
2008 as summarized in Table 6. The acaricidal activity of
compound 2a against the red spider mite, Panonychus ulmi (Koch),
is almost equivalent to that of pyidaben at 50–100 mg Lꢀ1, and
lower than that of fluacrypyrim.
2.8. Mammalian toxicology of compounds 2a and 2c
The primary mammalian toxicology tests of compounds 2a and
2c were studied, as shown in Table 7. The following results were
Table 4
Field trial results for compounds 2a and 2c in Liaoning against E. graminis.
Compound
Doses
Disease index
Control
(%)
(mg Lꢀ1
)
2a 200 g Lꢀ1 SC
135
45
30
2.7
5.9
7.1
93.1
84.9
81.8
Additionally, 3-chloro-5-(trifluoromethyl)pyridin-2-ol and
3,5,6-trichloro-pyridin-2-ol attracted our attention because it
is a popular heterocycle intermediate in the field of pesticide. We
designed and synthesized pyridine analogues 3a–3f (Table 3),
however these compounds showed lower fungicidal activities
than compounds 2a–2c.
2c 200 g Lꢀ1 SC
135
45
30
3.2
7.5
8.4
91.7
81.0
78.3
Pyraclostrobin 250 g Lꢀ1 SE
Triadimefon 150 g Lꢀ1 WP
135
45
30
3.5
5.1
4.9
91.0
86.8
87.5
2.6. Field trials with compounds 2a and 2c against E. graminis
In this study 2a and 2c were two of the most potent
compounds with fungicidal activity against E. graminis. We
carried out field trials of these two compounds against
135
5.2
86.6

L. Li et al. / Journal of Fluorine Chemistry 185 (2016) 173–180
179
Table 5
Table 6
Acaricidal activity against T. cinnabarinus of compound 2a.
Field trial results for compound 2a in Pulandian against Panonychus ulmi (Koch).
Compound
% mortality at given concentration mg Lꢀ1
Compound
Doses (mg Lꢀ1
)
Mortality at days after spraying (%)
150
40
10
3 d
7 d
14 d
89.2
21 d
77.7
2a 200 g Lꢀ1 SC
Fluacrypyrim
100
100
95
100
95
95
2a
50
89.6
91.1
200 g Lꢀ1 SC
100
150
93.1
96.1
96.5
97.1
95.0
95.9
87.8
91.2
determined compounds 2a and 2c were all low-toxicity com-
pounds.
Fluacrypyrim
Pyidaben
50
100
99.7
99.5
100.0
100.0
98.2
99.1
94.8
95.3
3. Experimental
50
100
91.9
95.9
95.9
95.5
96.8
97.1
78.8
78.2
All starting materials and reagents were commercially available
and used without further purification except as indicated. Melting
points were determined on a Büchi melting point apparatus and
are uncorrected. 1H NMR spectra were recorded with Mercury 300
(Varian, 300 MHz) spectrometer with CDCl3 as the solvent and TMS
as the internal standard. 19F NMR spectra were obtained on a
Mercury 300 (Varian, 300 MHz) spectrometer using CF3COOH
(TFA) as an external standard, positive for downfield shift. Infrared
spectra were measured with KBr discs using a PF–983 G instru-
ment (Perkin-Elmer). Elemental analyses were performed on a
Vario EL elemental analyzer. These compounds were tested for
controlling wheat powdery mildew (Erysiphe graminis) on
“Liaochun No.10” wheat and spider mites (Tetranychus cinnabar-
inus) on Kidney bean obtained from the Agrochemical Discovery
Group in Shenyang Research Institute of Chemical Industry.
The general synthesis routes for the title compounds are shown
in Schemes 1–3. Representative procedures are given below and
reaction yields were not optimized. New compounds were
identified and verified by 1H NMR, 19F NMR, IR, MS and elemental
analysis.
810, 770, 740 (s, Ph-H) cmꢀ1; 1H NMR (300 MHz, CDCl3):
(s, 2H, CH + Ph-3-H), 7.53(m,1H, Ph'-6-H), 7.35(m, 3H, Ph-5-H + Ph'-
3,5-2H), 7.20(m, 1H, Ph'-4-H), 6.89(d, J = 8.4 Hz, 1H, Ph-6-H), 5.12(s,
2H, OCH2), 3.83(s, 3H, COOCH3), 3.71(s, 3H, OCH3); 19F NMR(CDCl3,
d
ppm 7.62
TFA):
d
ppm ꢀ6.75(s, 3F, CF3); Anal. calcd (%) for C19H16ClF3O4: C,
56.94; H, 4.02. Found: C, 56.99; H, 4.00.
3.1.1. Synthesis of (E)-methyl 2-(2-((2-chloro-4-(trifluoromethyl)
phenoxy)methyl)phenyl)-2-(methoxyimino)acetate (2b; general
procedure for the compounds 1c, 1e, 1h, 2f, 3b and 3e)
2-Chloro-4-(trifluoromethyl)phenol (0.43 g, 2.19 mmol) was
dissolved in 15 mL of butanone, and anhydrous potassium
carbonate (0.60 g, 4.35 mmol) was added to the solution. The
solution was stirred for 0.5 h, and methyl (E)-methyl 2-(2-
(bromomethyl)phenyl)-2-(methoxyimino)acetate
(0.63 g,
2.20 mmol) was then added. The reaction mixture was heated to
80 ꢁC and monitored by TLC. After five hours, the mixture was
cooled, diluted with 50 mL water and extracted with ethyl acetate
(3 ꢂ100 mL). The combined extracts were washed with brine,
dried (anhydrous magnesium sulfate), and filtered. The filtrate was
evaporated and the crude product was purified via silica gel
column chromatography, using a 1:2 (v/v) mixture of ethyl acetate
and petroleum ether (boiling point range: 60–90 ꢁC) as the eluting
solution to obtain compound 2b as a white solid: 0.67 g (72.9%), mp
115–116 ꢁC.
3.1. Synthesis of target compounds (1a–1i, 2a–2k and 3a–3f)
3.1.1. Synthesis of (E)-methyl 2-(2-((2-chloro-4-(trifluoromethyl)
phenoxy)methyl)phenyl)-3-methoxyacrylate (2a, SYP-3759, flufenox-
ystrobin; general procedure for the compounds 1a, 1b, 1d, 1g, 2d, 2e,
3a and 3d)
2-Chloro-4-(trifluoromethyl)phenol (7a) (0.39 g, 1.98 mmol)
was dissolved in 15 mL of DMF, and anhydrous potassium
carbonate (0.55 g, 3.99 mmol) was added to the solution.
The solution was stirred for 0.5 h, and methyl (E)-methyl
1H NMR(300 MHz, CDCl3):
dppm 7.63(s, 1H, Ph-3-H), 7.58(m,
1H, Ph'-6-H), 7.45(m, 3H, Ph'-3,4,5-3H), 7.22(d, J = 8.4 Hz, 1H, Ph-5-
H), 6.93(d, J = 8.4 Hz, 1H, Ph-6-H), 5.09(s, 2H, OCH2), 4.04(s, 3H,
2-(2-(chloromethyl)phenyl)-3-methoxyacrylate
(0.48 g,
NOCH3), 3.88(s, 3H, COOCH3); 19F NMR(CDCl3, TFA):
3F, CF3); Anal. calcd (%) for C18H15ClF3NO4: C, 53.81; H, 3.76; N,
3.49. Found: C, 53.86; H, 3.74; N, 3.46.
d
ppm ꢀ6.88(s,
2.00 mmol) was added. The reaction mixture was heated to
80 ꢁC and was monitored by TLC. At completion (after 3 h) the
mixture was partitioned with 50 mL of brine, and extracted 3 times
with 100 mL of ethyl acetate. The combined organic extracts were
dried, and concentrated to obtain the crude product. It was further
purified via silica gel column chromatography, using a 1:4 (v/v)
mixture of ethyl acetate and petroleum ether (boiling point range:
60–90 ꢁC) as the eluting solution to obtain 2a as a white solid 0.51 g.
3.1.2. Synthesis of (E)-2-(2-((2-chloro-4-(trifluoromethyl)phenoxy)
methyl)phenyl)-2-(methoxyimino)-N-methylacetamide (2c; general
procedure for the compounds 1f, 1i, 2g, 3c and 3f)
Compound 2b (0.40 g, 0.96 mmol) was dissolved in 10 mL of
methanol, and methylamine (0.08 g, 2.57 mmol) was added to the
solution. The solution was stirred at room temperature and
monitored by TLC. After three hours, the mixture was concentrat-
ed, diluted with 50 mL water and extracted with ethyl acetate
(3 ꢂ100 mL). The combined extracts were washed with brine,
dried (anhydrous magnesium sulfate), and filtered. The filtrate was
evaporated and the crude product was purified via silica gel
column chromatography, using a 1:1 (v/v) mixture of ethyl acetate
and petroleum ether (boiling point range: 60–90 ꢁC) as the eluting
solution to obtain compound 2c as a white solid: 0.35 g (87.5%).
IR(KBr)
n
: 2950 (s, CꢀꢀH), 1690 (s, C
¼
O), 1630 (s, C C), 1500,
¼
1430, 1410 (s, CH3), 1320, 1270 (m, CꢀꢀN), 1120 (s, CꢀꢀO), 990, 890,
Table 7
Toxicity results.
Test
Compound 2a
Compound 2c
Acute oral
LD50 ꢃ 5000 mg kgꢀ1
LD50 ꢃ 5000 mg kgꢀ1
No irritation
No irritation
Negative
LD50 > 4640 mg kgꢀ1
LD50 ꢃ 2150 mg kgꢀ1
No irritation
No irritation
Negative
Acute percutaneous
Skin irritant
Eye irritant
Ames
1H NMR(300 MHz, CDCl3):
dppm 7.62(m, 1H, Ph-3-H), 7.51(m,
1H, Ph'-6-H), 7.42(m, 3H, Ph'-3,4,5-3H), 7.24 (m,1H, Ph-5-H), 6.93–
6.96(d, J = 8.4 Hz, 1H, Ph-6-H), 6.78(bs, 1H, CONH), 5.12(s, 2H,

180
L. Li et al. / Journal of Fluorine Chemistry 185 (2016) 173–180
OCH2), 3.92(s, 3H, NOCH3), 2.92(d, J = 5.4 Hz, 3H, CONHCH3); 19F
NMR(CDCl3, TFA):
C18H16ClF3N2O3: C, 53.94; H, 4.02; N, 6.99. Found: C, 53.86; H, 4.05;
N, 7.01.
compounds. More field trials, mammalian toxicology and ecotoxi-
cology of compound 2a are in progress.
d
ppm ꢀ6.65(s, 3F, CF3); Anal. calcd (%) for
Supporting information description
3.2. Fungicidal assay
1H NMR, IR and elemental analyses data for all synthesized
compounds can be found in the Supporting Information. This
material is available free of charge via the Internet at http://www.
sciencedirect.com.
Each of the test compounds (4 mg) was first dissolved in 5 mL
mixture of acetone and methanol (1:1 by volume), then 5 mL of
water containing 0.1% Tween 80 was added to generate a 10 mL
stock solution of concentration 400 mg Lꢀ1. Serial test solutions
were prepared by diluting the above solution. A 1:1:2 (v/v/v)
Acknowledgment
mixture containing 2
was used as untreated control.
m
Tween 80 of acetone, methanol and water
We thank Dr. Mark Dekeyser (Canada) for assistance with
manuscript preparation.
Evaluations of fungicidal activities of the synthesized com-
pounds against E. graminis were performed as follows: briefly, a
whole plant is used in this test, and the testing solution is sprayed
to the host plant by a special plant sprayer. The plant is inoculated
with fungus after 24 h. According to the infecting characteristics of
fungus, the plant is stored in a humidity chamber and then
transferred into a greenhouse after infection is finished. The other
plants are placed in a greenhouse directly. The activity of each
compound was estimated by visual inspection after 7 days, and
screening results were reported as a range from 0% (no control) to
100% (complete control).
Appendix A. Supplementary data
Supplementary data associated with this article can be found,
in
the
online
version,
at
http://dx.doi.org/10.1016/j.
jfluchem.2016.03.013.
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