Synthesis and herbicidal activity of 2-alkyl(aryl)-4-amino-3-[alkyl(alkoxy) carbonyl]-5-cyano-6-[(3-trifluoromethyl)phenoxy]-pyridines

Article abstract of DOI:10.1002/jhet.1591

To find novel bleaching herbicide lead compounds, a series of novel 2-alkyl(aryl)-4-amino-3-[alkyl(alkoxy)carbonyl]-5-cyano-6-[(3-trifluoromethyl) phenoxy]-pyridines was designed and synthesized by the multistep reactions. N,S-acetal 1 reacted with 2 to obtain multisubstituted pyridines 3 in the presence of zinc nitrate as the catalyst. The target compounds 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 5j, 5k, 5l were formed by the oxidation of 3, followed by the substitution with 3-(trifluoromethyl)phenol in the presence of potassium carbonate. Their structures were confirmed by IR, ¹H NMR, EI-MS, and elemental analyses. The preliminary bioassays indicated that some of them displayed moderate herbicidal activity against dicotyledonous weed Brassica campestris L at the concentration of 100 mg/L.

Full text of DOI:10.1002/jhet.1591

Month 2013 Synthesis and Herbicidal Activity of 2-Alkyl(aryl)-4-amino-3-[alkyl(alkoxy)
carbonyl]-5-cyano-6-[(3-trifluoromethyl)phenoxy]-pyridines
*
Yue-E Zhai and De-Qing Shi
Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, College of Chemistry, Central China Normal University,
Wuhan 430079, People’s Republic of China
*
E-mail: chshidq@mail.ccnu.edu.cn
Received October 8, 2011
DOI 10.1002/jhet.1591
Published online 00 Month 2013 in Wiley Online Library (wileyonlinelibrary.com).
F3C
NH2
N
O
NH2
O
NH2
O
OH
NC
NC
NC
Zn(NO3)2. 6H2O
C2H5OH
NC
NC
SMe
NH2
R2
R2
R2
H2O2/Na2WO4. 2H2O
DMF
F3C
R1COCH2COR2
+
O
R1
R1
N
R1
K2CO3/CH3CN
N
O
H3CS
H3CS
O
1
2
3
4
5a~5l
To find novel bleaching herbicide lead compounds, a series of novel 2-alkyl(aryl)-4-amino-3-[alkyl(alkoxy)
carbonyl]-5-cyano-6-[(3-trifluoromethyl)phenoxy]-pyridines was designed and synthesized by the multistep reactions.
N,S-acetal 1 reacted with 2 to obtain multisubstituted pyridines 3 in the presence of zinc nitrate as the catalyst.
The target compounds 5a~5l were formed by the oxidation of 3, followed by the substitution with 3-(trifluoromethyl)
1
phenol in the presence of potassium carbonate. Their structures were confirmed by IR, H NMR, EI-MS, and
elemental analyses. The preliminary bioassays indicated that some of them displayed moderate herbicidal activity
against dicotyledonous weed Brassica campestris L at the concentration of 100 mg/L.
J. Heterocyclic Chem., 00 00 (2013).
INTRODUCTION
5 in 71–93% yields. Their structures were deduced from
their spectral data (IR, 1H NMR, and EI-MS) and elemen-
tal analyses, which were listed in the experimental part. For
example, the IR spectra of 5b revealed NH2 at 3405 and
3332 cmÀ1, the signal 2228 cmÀ1 is attributed to CN
absorption, and 1660 and 1258 cm-1 are attributed to
C═O and C-O-C absorption bands, respectively. In the
1H NMR spectra of 5b, the two methyl protons showed
as two singlets at d 2.50 and 2.58, respectively, whereas
the amino protons displayed as a broad singlet at d 6.78.
However, in some cases, the amino protons could not be
Compounds containing pyridine moiety exhibited a
variety of biological activities and are widely used as
insecticides, fungicides, and herbicides in modern plant
protection [1–3]. Phytoene desaturase (PDS) is a key enzyme
for photosynthetic apparatus of green plants. If PDS is
inhibited by its inhibitors, a lack of carotenoid synthesis
may lead to typical bleaching symptoms in plants, so
the PDS inhibitors are developed as a kind of important
bleaching herbicides in modern agriculture (Fig. 1). As for
their structure–activity relationships, PDS inhibitors usually
possess a central five-membered or six-membered heterocy-
cle containing one or two substituted phenyl rings, in which
a 3-(trifluoromethyl)phenyl group is a common structure in
all inhibitors [4–6]. To find novel bleaching herbicide lead
compounds, we designed and synthesized a series of
novel multisubstituted pyridine derivatives containing of a
3-(trifluoromethyl)phenoxy group 5 by using commercially
herbicides diflufenican and picolinafen as lead compounds.
Herein, we would like to report the synthesis and herbicidal
activities of the title compounds 5 in this paper (Scheme 1).
1
found in their H NMR spectra; the aromatic protons of
the target compounds 5 appeared in the chemical shift d
7.1~8.2. The EI mass spectrum of 5b shows strong
molecular ion peak at m/z 335 with 100% abundance and
anticipated fragmentation ion peaks.
Herbicidal activity.
The preliminary herbicidal
activities of compounds 5 were evaluated, against two
representative targets, oil rape and barnyard grass, at
concentrations of 100 and 10 mg/L, according to a
literature method [7]. The results are listed in Table 1 and
show that these compounds have moderate herbicidal
activity against oil rape at the concentration of 100 mg/L.
For example, compounds 5c and 5j possessed 80.9 and
81.7% inhibition against Brassica campestris L at the
concentration of 100 mg/L. As for the preliminary
structure–activity relationships, firstly, those compounds
when R2 is methoxy and R1 is methyl or electron-
donating substituents in aromatic ring (e.g., 5c and 5j)
exhibited better activity than those when R1 is electron-
withdrawing ones in aromatic ring (e.g., 5g, 5i, 5k,
RESULTS AND DISCUSSION
N,S-acetal 1 reacted with b-diketone or b-keto ester 2 in
the presence of zinc nitrate to obtain multisubstituted
pyridine 3 in good to excellent yields, the oxidation of 3
with H2O2 in the presence of a catalytic amount of sodium
tungstate to give pyridyl methylsulfone 4, which reacted
with 3-(trifluoromethyl)phenol in the presence of anhy-
drous potassium carbonate to give the target compounds
© 2013 HeteroCorporation

Y. Zhai and D. Shi
Vol 000
O
O
O
N
NH
O
Cl
F
F
N
O
N
NH
N
N
O
F3C
O
F3C
F3C
N
NO2
HN
F
O
Picolinafen
diflufenican
imidacloprid
Picoxystrobin
Figure 1. Some commercial pyridine pesticides and phytoene desaturase inhibitors.
Scheme 1. Synthetic route to compounds 5a~5l.
NH2
O
NH2
O
NC
NC
Zn(NO3)2. 6H2O
C2H5OH
NC
SMe
NH2
R2
R2
H2O2/Na2WO4. 2H2O
DMF
R1COCH2COR2
+
O
N
R1
NC
N
R1
H3CS
H3CS
O
1
2
3
4
F3C
5a (R1 = Me, R2 = OC2H5), 5b (R1 = Me, R2 = CH3), 5c (R1 = Me, R2 = OCH3),
5d (R1 = C6H5, R2 = OC2H5), 5e (R1 = 4-FC6H4, R2 = OC2H5), 5f (R1 = 2-FC6H4, R2 = OC2H5),
NH2
N
O
OH
NC
R2
F3C
5g (R1 = 2-ClC6H4, R2 = OCH3), 5h (R1 = 4-CH3C6H4, R2 = OC2H5), 5i (R1 = 3-ClC6H4, R2 = OCH3),
5j (R1 = 4-CH3C6H4, R2 = OCH3), 5k (R1 = 4-ClC6H4, R2 = OCH3), 5l (R1 = 4-NO2C6H4, R2 = OCH3)
R1
K2CO3/CH3CN
O
5a~5l
and 5l) did; secondly, those compounds when R2 is
methoxy displayed better activity than those when R1 is
ethoxy did. Further exploring of structure–activity
relationships needs more experimental results to support.
Further biological activity (in vivo) investigations are on
the way.
In conclusion, a series of novel 2-alkyl (aryl)-4-amino-3-
[alkyl(alkoxyl)carbonyl)]-5-cyano-6-[(3-trifluoromethyl)
phenoxy]-pyridines was designed and synthesized by the
multistep reactions. Their structures were confirmed by IR,
1H NMR, EI-MS, and elemental analyses. The preliminary
bioassays indicated that some of them displayed moderate
herbicidal activity against dicotyledonous weed B. campestris
L at the concentration of 100 mg/L.
EXPERIMENTAL
Melting points were determined with a WRS-1B digital melting
1
point apparatus and are uncorrected. H NMR spectra (Wuhan,
China) were recorded with a Varian Mercury PLUS 600
(600 MHz) spectrometer (CA, USA) with TMS as the internal refer-
ence and CDCl3 as the solvent, whereas mass spectra were measured
on a Finnigan TraceMS 2000 spectrometer (CA, USA) at 70 eV by
using EI method. IR spectra were measured by a Nicolet NEXUS470
spectrometer (ThermoNicoletCorporation, USA). Elemental analy-
ses were performed with an Elementar Vario ELШ CHNSO
elemental analyzer (Elementar cooperation, Germany). Compounds
1 and 2 can be prepared according to the reported methods [8,9],
respectively. All of the solvents and materials were reagent grade
and purified as required (Beijing, China).
Synthesis of 4-amino-3-(ethoxy carbonyl)-5-cyano-6-methylthio-
2-phenyl-pyridine 3a [10]. 1 (3.47 g, 25 mmol), ethyl benzoyl
acetate (4.8 g, 25 mmol), zinc nitrate hydrate (14.9 g, 50 mmol),
and anhydrous ethanol (50 mL) were added to a 100-mL three-
necked flask; the mixture was stirred under reflux for 12 h till
the reaction was complete (monitored by TLC). The resulting
mixture was cooled to room temperature and filtered by
suction, and the crude product was recrystallized in ethanol to
give 3a as white solid in 87% yield, mp 135.8–137.2ꢀC; other
compounds 3 can be synthesized in the similar procedure,
which can be used in the next reaction directly without further
structure characterization.
Synthesis of 2-alkyl (aryl)-4-amino-3-(alkyl or alkoxycarbonyl)-
5-cyano-6-methylsulfonyl-pyridines 4 [10]. 3 (10 mmol), sodium
tungstate (2 mmol, 0.66 g), and DMF (20 mL) were added to
a 100-mL three-necked flask; the mixture was stirred at 40–
50ꢀC, whereas the solution of 30% H2O2 (4.5 g, 40 mmol) in
ethanol (5 mL) was added dropwise slowly; after the
addition was complete, the mixture was stirred at 60ꢀC for
3 h (monitored by TLC). After most of solvents were
removed in vacuum, the residue was poured into water
(100 mL), the solid formed was filtered by suction, and the
Table 1
Herbicide activity of compounds 5a~5l (growth inhibition rate %).
B. campestris root test
E. crus-galli cup test
Compound 10 mg/mL 100 mg/mL
10 mg/mL
100 mg/mL
5a
5b
5c
5d
5e
5f
5g
5h
5i
18.2
18.2
50.2
25.5
0
18.6
23.9
0
50.2
50.2
80.9
63.9
31.1
52.5
52.5
10.2
10.5
81.7
41.8
41.8
0
0
0
0
0
0
5.0
0
15.0
10.0
5.0
5.0
25.0
30.0
25.0
0
0
0
0
0
25
0
0
0
45.5
0
5j
5k
5l
0
25.0
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2013
2-Alkyl(aryl)-4-amino-3-[alkyl(alkoxy)carbonyl]-5-cyano-6-
[(3-trifluoromethyl)phenoxy]-pyridines
1
5f: light yellow solid, yield 76%, mp 140.3~141.7ꢀC; H NMR
crude product was recrystallized using the mixture of DMF
and H2O (1:1) to give 4 as light yellow solids in 68–89%
yields, which can be used in the next reaction directly
without further structure characterization.
(CDCl3, 600 MHz) d: 0.75 (t, J= 7.2 Hz, 3H, CH2CH3), 3.96
(q, J= 6.6 Hz, 2H, OCH2), 7.14 (d, J= 7.8 Hz, 1H, ArH), 7.24
(d, J= 7.2 Hz, 1H, ArH), 7.28 (d, J= 7.2 Hz, 1H, ArH), 7.33
(d, J= 7.8 Hz, 1H, ArH), 7.39 (d, J= 7.8 Hz, 1H, ArH), 7.42–7.48
(m, 2H, ArH), 7.51 (s, 1H, ArH); IR (KBr) υ: 3412, 3331 (NH),
2989 (ArH), 2228 (CN), 1693 (C═O), 1628, 1570, 1547 (Ar), 1327
(C-F), 1278 (C-O-C) cmÀ1; EI-MS (70 eV) m/z (%): 426 (M-19,
100), 398 (82.3), 282 (14.6), 199 (9.7), 145 (21.0), 126 (14.6). Anal.
Calcd for C22H15F4N3O3: C 59.33, H 3.39, N 9.43; found C 59.12,
H 3.45, N 9.47.
General procedure for the synthesis of 2-alkyl(aryl)-4-amino-3-
[alkyl(alkoxy)carbonyl]-5-cyano-6-[(3-trifluoromethyl)phenoxy]-
pyridines 5. 4 (3.0mmol), 3-(trifluoromethyl)phenol (6.0 mmol,
0.97g), anhydrous potassium carbonate (3 mmol, 0.41g), and
CH3CN (20 mL) were added to a 50-mL three-necked flask, and
the mixture was allowed to be stirred under reflux for 1–2 h
(monitored by TLC). The workup involved stripping of the
solvent followed by addition of water (30mL) and extraction of
the product mixture into chloroform (15ml*3). After phase
separation, washing with 5% aqueous NaOH and drying over
anhydrous magnesium sulfate, filtration, and evaporation, the
crude product was recrystallized using the mixture of CH2Cl2 and
petroleum ether (1:1) or purified by flash column chromatography
on silica gel (eluent: petroleum ether/acetone 6:1) to give 5 in
71–93% yields.
5g: colorless crystals, yield 86%, mp 169.5~170.5ꢀC; 1H NMR
(CDCl3, 600 MHz) d: 3.45 (s, 3H, OCH3), 7.15 (d, J = 7.8 Hz, 1H,
ArH), 7.22–7.28 (m, 2H, ArH), 7.34 (d, J = 7.2 Hz, 1H, ArH),
7.40 (d, J = 7.8 Hz, 1H, ArH), 7.43–7.48 (m, 2H, ArH), 7.51
(s, 1H, ArH); IR (KBr) υ: 3421, 3338 (NH), 2985 (ArH), 2225
(CN), 1691 (C═O), 1623, 1574, 1548 (Ar), 1321 (C-F), 1275
1
(C-O-C) cmÀ ; EI-MS (70 eV) m/z (%): 447 (M, 0.51), 426
(5.9), 421 (100), 396 (8.1), 358 (4.2), 282 (7.8), 145 (18.8),
5a: colorless crystals, yield 76%, mp 135.4~136.3ꢀC; 1H NMR
(CDCl3, 600MHz) d: 1.24 (t, J = 7.3 Hz, 3H, CH2CH3), 2.52
(s, 3H, CH3), 4.39 (q, J = 7.2 Hz, 2H, OCH2), 7.37 (d, J = 6.6 Hz,
1H, ArH), 7.47 (s, 1H, ArH), 7.50–7.53 (m, 2H, ArH); IR (KBr)
υ: 3411, 3365 (NH), 2984 (ArH), 2222 (CN), 1695 (C═O),
1620, 1568, 1536 (Ar), 1325 (C-F), 1274 (C-O-C) cmÀ1; EI-MS
(70 eV) m/z (%): 365 (M+, 100), 319 (61), 293 (87.8), 186 (77.4),
145 (45.5), 95 (9.7). Anal. Calcd for C17H14F3N3O3: C 55.89, H
3.86, N 11.50; found C 55.94, H 3.93, N 11.37.
126 (9.5), 95 (5.2). Anal. Calcd for C21H13ClF3N3O3: C 56.33,
H 2.93, N 9.38; found C 56.49, H 3.13, N 9.10.
5h: colorless solid, yield 93%, mp 124.3~126.5ꢀC; 1H NMR
(CDCl3, 600MHz) d: 0.84 (t, J= 7.8 Hz, 3H, CH2CH3), 2.35 (s, 3H,
CH3), 4.01 (q, J= 7.2 Hz, 2H, OCH2), 7.12 (d, J= 7.8 Hz, 2H, ArH),
7.22 (d, J= 7.8 Hz, 2H, ArH), 7.41 (d, J= 7.2 Hz, 1H, ArH), 7.48–
7.50 (m, 2H, ArH), 7.57 (s, 1H, ArH); IR (KBr) υ: 3444, 3370
(NH), 2981 (ArH), 2219 (CN), 1692 (C═O), 1623, 1570, 1542
(Ar), 1328 (C-F), 1277 (C-O-C) cmÀ1; EI-MS (70 eV) m/z (%): 441
(M, 100), 412 (59.7), 395 (17.2), 369 (70.3), 262 (53.4), 145 (24.5),
142 (30.6), 115 (12.1), 91 (11.6). Anal. Calcd for C23H18F3N3O3: C
62.58, H 4.11, N 9.52; found C 62.39, H 4.20, N 9.36.
1
5b: colorless solid, yield 85%, mp 135.8~137.6ꢀC; H NMR
(CDCl3, 600MHz) d: 2.50 (s, 3H, CH3), 2.58 (s, 3H, CH3), 6.78
(s, 2H, NH2), 7.37 (d, J = 7.2 Hz, 1H, ArH), 7.47 (s, 1H, ArH),
7.51–7.53 (m, 2H, ArH); IR (KBr) υ: 3405, 3332 (NH), 2990
(ArH), 2228 (CN), 1660 (C═O), 1569, 1453, 1427 (Ar), 1325
(C-F), 1258 (C-O-C) cmÀ1; EI-MS (70 eV) m/z (%): 335
(M+, 100), 320 (53.2), 292 (17.8), 186 (80.7), 145 (41.8),
95 (9.9). Anal. Calcd for C16H12F3N3O2: C 57.32, H 3.61,
N 12.53; found C 57.47, H 3.50, N 12.77.
5i: colorless crystals, yield 89%, mp 116.4~117.6ꢀC; 1H NMR
(CDCl3, 600 MHz) d: 3.54 (s, 3H, OCH3), 7.16 (d, J = 7.8 Hz, 1H,
ArH), 7.25 (d, J = 7.8 Hz, 1H, ArH), 7.30 (s, 1H, ArH), 7.34
(d, J = 8.4 Hz, 1H, ArH), 7.40 (d, J = 6.6 Hz, 1H, ArH), 7.50–
7.54 (m, 2H, ArH), 7.55 (s, 1H, ArH); IR (KBr) υ: 3443, 3364
(NH), 2985 (ArH), 2213 (CN), 1690 (C═O), 1625, 1568, 1546
5c: colorless crytals, yield 79%, mp 153.2~154.0ꢀC; 1H NMR
(CDCl3, 600 MHz) d: 2.51 (s, 3H, CH3), 3.92 (s, 3H, OCH3), 7.37
(d, J = 7.2 Hz, 1H, ArH), 7.47 (s, 1H, ArH), 7.49–7.53 (m, 2H,
ArH); IR (KBr) υ: 3408, 3343 (NH), 2995 (ArH), 2223 (CN),
1686 (C═O), 1575, 1451, 1442 (Ar), 1327 (C-F), 1271 (C-O-C)
cmÀ1. Anal. Calcd for C16H12F3N3O3: C 54.71, H 3.44, N
11.96; found C 54.53, H 3.20, N 11.75.
(Ar), 1326 (C-F), 1272 (C-O-C) cmÀ1
. Anal. Calcd for
C21H13ClF3N3O3: C 56.33, H 2.93, N 9.38; found C 56.47, H
3.02, N 9.25.
1
5j: colorless solid, yield 85%, mp 139.5~141.3ꢀC; H NMR
(CDCl3, 600 MHz) d: 2.35 (s, 3H, CH3), 3.54 (s, 3H, OCH3),
6.45 (s, 2H, NH2), 7.13 (d, J = 8.4 Hz, 2H, ArH), 7.22 (d,
J = 7.8 Hz, 2H, ArH), 7.41 (d, J = 7.2 Hz, 1H, ArH), 7.48–7.51
(m, 2H, ArH), 7.57 (s, 1H, ArH); IR (KBr) υ: 3442, 3375 (NH),
2985 (ArH), 2216 (CN), 1690 (C═O), 1626, 1571, 1547 (Ar),
1325 (C-F), 1272 (C-O-C) cmÀ1. Anal. Calcd for C22H16F3N3O3:
C 61.83, H 3.77, N 9.83; found C 61.63, H 3.84, N 9.61.
5k: colorless crystals, yield 87%, mp 142.5~142.8ꢀC; 1H NMR
(CDCl3, 600 MHz) d: 3.54 (s, 3H, OCH3), 6.58 (s, 2H, NH2),
7.24 (d, J = 8.4 Hz, 2H, ArH), 7.30 (d, J = 8.4 Hz, 2H, ArH),
7.39 (d, J = 6.0 Hz, 1H, ArH), 7.49–7.51 (m, 2H, ArH), 7.54
(s, 1H, ArH); IR (KBr) υ: 3445, 3366 (NH), 2982 (ArH), 2218
(CN), 1693 (C═O), 1621, 1567, 1544 (Ar), 1326 (C-F), 1270
(C-O-C) cmÀ1. Anal. Calcd for C21H13ClF3N3O3: C 56.33, H
2.93, N 9.38; found C 56.18, H 2.80, N 9.49.
5d: colorless solid, yield 87%, mp 159.3~161.1ꢀC; 1H NMR
(CDCl3, 600 MHz) d: 0.79 (t, J =7.2Hz, 3H, CH2CH3), 3.98
(q, J= 7.2 Hz, 2H, OCH2), 6.58 (s, 2H, NH2), 7.31–7.51 (m, 8H,
ArH), 7.56 (s, 1H, ArH); IR (KBr) υ: 3418, 3337 (NH), 2992
(ArH), 2225 (CN), 1662 (C═O), 1571, 1458, 1423 (Ar), 1327
(C-F), 1255 (C-O-C) cmÀ1; EI-MS (70 eV) m/z (%): 427 (M+, 100),
398 (57.6), 381 (21.7), 248 (65.1), 145 (36.5), 128 (39.1), 104
(14.6), 77 (31.0). Anal. Calcd for C22H16F3N3O3: C 61.83, H 3.77,
N 9.83; found C 61.98, H 3.64, N 9.60.
1
5e: colorless solid, yield 91%, mp 131.5~132.3ꢀC; H NMR
(CDCl3, 600 MHz) d: 0.87 (t, J =7.2 Hz, 3H, CH2CH3), 4.02
(q, J = 6.6 Hz, 2H, OCH2), 7.01 (d, J = 8.4Hz, 2H, ArH), 7.30 (dd,
J = 4.8Hz, J = 8.4 Hz, 2H, ArH), 7.40 (d, J = 6.6Hz, 1H,
ArH), 7.48–7.51 (m, 2H, ArH), 7.55 (s, 1H, ArH); IR (KBr) υ:
3410, 3334 (NH), 2985 (ArH), 2227 (CN), 1693 (C═O), 1625,
1572, 1546 (Ar), 1328 (C-F), 1275 (C-O-C) cmÀ1. Anal. Calcd
for C22H15F4N3O3: C 59.33, H 3.39, N 9.43; found C 59.47, H
3.50, N 9.24.
5l: colorless crystals, yield 71%, mp 170.5~171.2ꢀC; 1H NMR
(CDCl3, 600 MHz) d: 3.52 (s, 3H, OCH3), 7.39 (s, 1H, ArH), 7.43
(d, J = 8.4 Hz, 2H, ArH), 7.48–7.52 (m, 3H, ArH), 8.18
(d, J = 8.4 Hz, 2H, ArH); IR (KBr) υ: 3444, 3350 (NH), 2224
(CN), 1705 (C═O), 1633, 1570, 1522 (Ar), 1326 (C-F), 1280
(C-O-C) cmÀ1; EI-MS (70 eV) m/z (%): 458 (M, 100), 432
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Y. Zhai and D. Shi
Vol 000
[3] Karadimos, D. A.; Karaoglanidis, G. S.; Tzavella–Klonari, K.
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[4] Sandmann, G.; Böger, P. Phytoene desaturase as a target for
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[5] Sandmann, G. Bleaching herbicides: action mechanism in
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(7.9), 411 (11.8), 357 (10.6), 293 (34), 282 (14.5), 247 (28.6),
219 (9.6), 195 (8.5), 153 (16.3), 145 (32), 138 (12.2), 77 (17.2).
Anal. Calcd for C21H13F3N4O5: C 55.03, H 2.86, N 12.22; found
C 55.27, H 2.72, N 12.46.
Herbicidal activity testing.
The herbicidal activity
measurement method was adapted according to a literature
method [7].
Acknowledgments. This work was supported by the Natural Science
Foundation of China (No. 20872046) and the Fundamental Research
Funds for the Central Universities (No. CCNU09A02013).
REFERENCES AND NOTES
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Journal of Heterocyclic Chemistry
DOI 10.1002/jhet