Synthesis and bioactivity study of 2-acylamino-substituted N'-benzylbenzohydrazide derivatives

Article abstract of DOI:10.1021/jf303376t

The discovery of new safe and effective pesticides is one of the main means of providing eco-friendly agricultural agents for modern crop protection. To identify new biological molecules based of the anthranilic diamide skeleton of the novel pesticide chlorantraniliprole, which acts on the ryanodine receptor and functional groups in acyl hydrazine insect growth regulators, more than 40 new compounds of 2-acylamino-substituted N'-benzylbenzohydrazide derivatives were designed and synthesized. The structures of the new compounds were characterized using ¹H nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HRMS), or electron impact mass spectrometry (EI-MS), and their biological activities at a concentration of 600 mg L ^-1 were determined against cotton aphid (Aphis gossypii Glover), carmine spider mite (Tetranychus cinnabarinus), and diamondback moth (Plutella xylostella). The results of a preliminary assay showed that compounds 6a-I-2 and 6d-III-4 maintained the lethal activity of anthranilic diamide against P. xylostella; compounds 6c-II-4, 6d-I-7, 6d-II-1, and 6d-III-5 exhibited good lethal activity against A. gossypii; and compounds 6a-II-1, 6a-III-1, 6b-I-7, 6c-I-1, and 6c-III-5 retained promising larvicidal activities against T. cinnabarinus. In subsequent further tests against T. cinnabarinus, compounds 6a-II-1, 6a-III-1, 6c-I-1, and 6c-III-5 showed an LC₅₀ value of <90 mg L^-1; especially, the LC₅₀ of compound 6a-III-1 was only 27.9 mg L^-1. In conclusion, the introduction of the functional fragment-substituted acyl hydrazine improved the acaricidal activity of the anthranilic diamide skeleton, and the halogen atom at X position and the methyl group at R₁ play crucial roles in the biological activities of the compounds.

Full text of DOI:10.1021/jf303376t

Article
pubs.acs.org/JAFC
Synthesis and Bioactivity Study of 2‑Acylamino-Substituted
N′‑Benzylbenzohydrazide Derivatives
Junjun Ou,† Xiaokun Zhu,† Lei Wang,† Chuan Xu,† Feng Liu,† Long Ren,‡ Xibao Xu,‡ Yi Wang,†
Changhui Rui,*,‡ and Shangzhong Liu*,†
†Department of Applied Chemistry, College of Science, China Agricultural University, Beijing 100193, People's Republic of China
‡Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, People's Republic of China
ABSTRACT: The discovery of new safe and effective pesticides is one of the main means of providing eco-friendly agricultural
agents for modern crop protection. To identify new biological molecules based of the anthranilic diamide skeleton of the novel
pesticide chlorantraniliprole, which acts on the ryanodine receptor and functional groups in acyl hydrazine insect growth
regulators, more than 40 new compounds of 2-acylamino-substituted N′-benzylbenzohydrazide derivatives were designed and
1
synthesized. The structures of the new compounds were characterized using H nuclear magnetic resonance (NMR), high-
resolution mass spectrometry (HRMS), or electron impact mass spectrometry (EI-MS), and their biological activities at a
concentration of 600 mg L−1 were determined against cotton aphid (Aphis gossypii Glover), carmine spider mite (Tetranychus
cinnabarinus), and diamondback moth (Plutella xylostella). The results of a preliminary assay showed that compounds 6a-I-2 and
6d-III-4 maintained the lethal activity of anthranilic diamide against P. xylostella; compounds 6c-II-4, 6d-I-7, 6d-II-1, and 6d-III-
5 exhibited good lethal activity against A. gossypii; and compounds 6a-II-1, 6a-III-1, 6b-I-7, 6c-I-1, and 6c-III-5 retained
promising larvicidal activities against T. cinnabarinus. In subsequent further tests against T. cinnabarinus, compounds 6a-II-1, 6a-
III-1, 6c-I-1, and 6c-III-5 showed an LC50 value of <90 mg L−1; especially, the LC50 of compound 6a-III-1 was only 27.9 mg L−1.
In conclusion, the introduction of the functional fragment-substituted acyl hydrazine improved the acaricidal activity of the
anthranilic diamide skeleton, and the halogen atom at X position and the methyl group at R1 play crucial roles in the biological
activities of the compounds.
KEYWORDS: 2-acylamino-substituted N′-benzylbenzohydrazide derivatives, synthesis, insecticide
In 1988, Rohm & Hass Co. introduced dibenzoylhydrazine
compound RH-58496,7 as an insect growth inhibitor (ecdysone
antagonist) that has high efficacy and a new action mode. Since
then, acylhydrazines that act as insect growth regulators have
become one of the main classes of pesticides. Subsequently,
many new compounds based on the features of RH-5849 have
been discovered and widely used over the past 20 years, such as
RH-5992,8 ANS-118,9 and JS-118.10
Functional fragments or skeletons play a crucial role in
biologically active chemicals, and modifications in the func-
tional groups could improve or change the biological activity of
parent compounds. To improve the biological activity of
anthranilic diamide insecticides against aphids or acarids, we
incorporated the functional fragment acylhydrazine into
anthranilic diamide and synthesized a series of 2-acylamino-
substituted N′-benzylbenzohydrazide derivatives (Table 3)
according to Scheme 1. The biological activities of these
compounds against three representative insect species were
assessed preliminarily.
INTRODUCTION
■
Control of pest insects with the application of chemical
insecticides is an important aspect in modern agricultural
practices. However, broad application of chemicals over the
long term induces resistance in the treated pest insects by
improving their tolerance1 and causing changes in their
behavior.2 In addition, there are concerns regarding the impact
of residual compounds and environmental issues with the use
of chemical insecticides; hence, some existing commercial
products might not meet the requirement of pest insect control
in the future.
Controlling the development of insecticide resistance in pests
and limiting the usage of synthetic chemicals for maintaining an
eco-friendly environment necessitates the identification of
alternative molecules with new structural features and action
modes. For instance, the recently commercialized insecticides
flubendiamide (Nihon Nohyaku Co., Ltd., and Bayer
Pharmaceutical) and chlorantraniliprole (DuPont Crop Pro-
tection), belonging to the new chemical classes phthalic acid
diamides and anthranilic diamides, respectively, act on the
ryanodine receptor as a new target of insecticides.3,4 Because of
their excellent performance in the field, new mode of action,
and low toxicity to mammals, they have been applied broadly
worldwide and have been attracting the attention of researchers
focusing on insecticide discovery. These compounds were
considered as the most important breakthrough in the field of
pesticides after the discovery of dibenzoylhydrazine com-
pounds.5
MATERIALS AND METHODS
Instruments and Reagents. Reagents and solvents were
purchased from Alfa-Aesar, J&K, Beijing Coupling Technology Co.,
■
Received: August 1, 2012
Revised: October 19, 2012
Accepted: October 22, 2012
Published: October 22, 2012
© 2012 American Chemical Society
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a
Scheme 1
a
Reagents and conditions: (i) DMF, NCS/NBS, 80 °C, 30 min; (ii) 1,4-dioxane, triphosgene, reflux, 6 h; (iii) acyl chloride, dry THF, Et3N, 0 °C,
room temperature, 12 h; (iv) 85% hydrazine hydrate, ethanol, reflux, 30 min; (v) THF, room temperature, 24−48 h.
Ltd., or China Sinopharm Chemical Reagent Co., Ltd., and used
directly without further purification. All anhydrous solvents were dried
and purified using the standard techniques before use. New
compounds were purified using column chromatography filled with
silica gel or recrystallized in organic solvents.
Compound 3b is commercially available, and intermediates 3c and
3d were prepared according to the procedure described for
intermediate 3a. The data for 3c and 3d are shown in Table 1.
Synthesis of 6-Chloro-2-(1-chloro-2-methylpropan-2-yl)-8-meth-
yl-4H-benzo[d][1,3]oxazin-4-one (4a-I) .13 Intermediate 3a (1.06 g, 5
mmol) and anhydrous triethylamine (2.02 g, 20 mmol) were added to
20 mL of anhydrous tetrahydrofuran, and the mixture was cooled to 0
°C under stirring. Next, 3-chloro-2,2-dimethylpropanoyl chloride (0.93
g, 6 mmol) was injected slowly into the mixture by using a syringe over
a period of 10 min. The mixture was stirred at room temperature for
12 h, and most of the tetrahydrofuran and triethylamine were distilled
off using a rotary evaporator. The residue was dissolved in 20 mL of
ethyl acetate and then washed once with saturated sodium bicarbonate
solution and twice with water. The obtained organic phase was dried
and concentrated to afford 1.53 g of 4a-I as a white solid: yield, 93%;
mp, 87.2−87.9 °C; 1H NMR (300 MHz, CDCl3) δ 7.95 (d, J = 2.5 Hz,
1H, Ar−H), 7.56 (d, J = 2.5 Hz, 1H, Ar−H), 3.78 (s, 2H, −CH2−Cl),
2.51 (s, 3H, Ar−CH3), 1.22 (s, 6H, Me2−C); EI-MS (m/z, %) 285
(M+, 100).
1H nuclear magnetic resonance (NMR) spectra were obtained at
300 MHz by using a Bruker spectrometer in CDCl3 or DMSO-d6
solution with tetramethylsilane as the internal standard. 13C NMR
spectra were obtained on a Bruker spectrometer and recorded in
CDCl3 solution referenced to its corresponding solvent peaks (δ
77.23). Chemical shift values (δ) were expressed in parts per million
(ppm). High-resolution mass spectrometry (HRMS) and MS data
were recorded using Agilent G1969A and G1956B spectrometers,
respectively, by using the electron impact (EI) ion source. The melting
points were determined using a Stuart melting point apparatus and
were uncorrected.
Synthesis. Synthesis of 2-Amino-5-chloro-3-methylbenzoic Acid
(2a) .11 2-Amino-3-methylbenzoic acid 1 (15.1 g, 0.1 mol) was
dissolved in 100 mL of N,N-dimethylformamide and heated to 70 °C;
subsequently, N-chlorosuccinimide (14.5 g, 0.11 mol) was gradually
added at 70−80 °C. The mixture was stirred at 80 °C for 30 min and
poured into a flask containing 500 g of ice. The precipitate was filtered,
rinsed with ice water, and dried to afford 18.1 g of 2a as a pale powder:
Intermediates 4a-II−4d-III were prepared according to the
procedure used for 4a-I. The data for 4a-II−4d-III are shown in
Table 1.
Synthesis of 2-Chlorobenzyl Hydrazine (5a) .14 For this, 50 g (0.85
mol) of hydrazine hydrate (85%) was dissolved in 200 mL of ethanol
and heated to reflux. Subsequently, 2-chlorobenzyl chloride (16 g, 0.1
mol) was added dropwise over a period of 1 h, and the reaction
mixture was kept at reflux for another 30 min. Most of the ethanol and
hydrazine hydrate were distilled off using a rotary evaporator, and the
residue was dissolved in ethyl acetate and washed with brine and
water. The obtained organic layer was dried and distilled to afford 10.2
g of 5a as a light yellow liquid (yield, 65%). The other benzyl
hydrazines 5b−5g (5b, 2-fluorobenzyl hydrazine; 5c, 4-fluorobenzyl
hydrazine; 5d, 2-chloro-5-(hydrazinylmethyl)pyridine; 5e, 3-
(trifluoromethyl)benzyl hydrazine; 5f, 2,4-dichlorobenzyl hydrazine;
and 5g, benzyl hydrazine) were prepared by following the same
procedure as that used for 5a, and all of these intermediates were
directly reacted with 4a-I−4d-III without purification.
1
yield, 97.8%; meting point (mp), 196.2 °C (decomposed); H NMR
(300 MHz, DMSO) δ 7.61 (d, J = 2.5 Hz, 1H, Ar−H), 7.26 (d, J = 2.5
Hz, 1H, Ar−H), 2.16 (s, 3H, Ar−CH3); EI-MS (m/z, %) 186 ([M +
H]+, 100).
Synthesis of 2-Amino-5-bromo-3-methylbenzoic Acid (2c). N-
Bromosuccinimide (19.5 g, 0.11 mol) was reacted with 2-amino-3-
methylbenzoic acid 1 (15.1 g, 0.1 mol) according to the procedure
described for compound 2a to afford 21.9 g of 2c as a brown powder:
1
yield, 95.6%; mp, 218.2−219.7 °C; H NMR (300 MHz, DMSO) δ
7.68 (d, J = 2.5 Hz, 1H, Ar−H), 7.32 (d, J = 2.5 Hz, 1H, Ar−H), 2.11
(s, 3H, Ar−CH3); EI-MS (m/z, %) 230 ([M + H]+, 100).
Synthesis of 6-Chloro-8-methyl-1H-benzo[d][1,3]oxazine-2,4-
dione (3a) .12 A suspension of 2a (9.25 g, 50 mmol) in 100 mL of
1,4-dioxane was heated to reflux; subsequently, triphosgene (5.88 g, 20
mmol) in 50 mL of 1,4-dioxane was added dropwise over a period of
30 min. The reaction mixture was kept at reflux for 6 h and then
cooled to room temperature in a water bath. The resultant precipitate
was filtered, rinsed with petroleum ether, and dried to afford 10.30 g of
General procedures for the synthesis of target compounds have
been described below (6a-I-1 as an example), and the data for 6a-I-2−
6d-III-5 are shown in Table 2.
Synthesis of 3-Chloro-N-(4-chloro-2-(2-(2-chlorobenzyl)-
hydrazinecarbonyl)-6-methylphenyl)-2,2-dimethylpropanamide
(6a-I-1) .15 2-Chlorobenzyl hydrazine 5a (0.19 g, 1.2 mmol) was
added to a solution of compound 4a-I (0.33 g, 1 mmol) in 5 mL of
tetrahydrofuran, and the mixture was stirred for about 24 h at room
temperature. When the reaction was completed by using a thin layer
chromatography (TLC) monitor, 10 mL of petroleum ether was
1
3a as a white powder: yield, 97.6%; mp, 263 °C (decomposed); H
NMR (300 MHz, DMSO) δ 10.14 (s, 1H, −NH−), 7.85 (d, J = 2.5
Hz, 1H, Ar−H), 7.57 (d, J = 2.5 Hz, 1H, Ar−H), 2.21 (s, 3H, Ar−
CH3); EI-MS (m/z, %) 212 ([M + H]+, 100).
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Table 3. Structure and Preliminary Biological Activity of the New Compounds
% mortality
compd
6a-I-1
X
R1
R2
R3
against A. gossypii
against T. cinnabarinus
against P. xylostella
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
-Cl
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−H
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)3
−C(CH3)3
−C(CH3)3
−C(CH3)3
−C(CH3)3
2-Cl−C6H4−
2-F−C6H4−
4-F−C6H4−
2-Cl−C5H3N-5−
3-CF3−C6H4−
2,4-Cl−C6H3−
C6H5−
2-Cl−C6H4−
2-F−C6H4−
4-F−C6H4−
2−Cl-C5H3N-5-
3-CF3−C6H4−
2,4-Cl−C6H3−
C6H5−
2-Cl−C6H4−
3-CF3−C6H4−
2,4-Cl−C6H3−
C6H5−
4-F−C6H4−
3-CF3−C6H4−
2-F−C6H4−
2-Cl−C6H4−
2-Cl−C5H3N-5−
3-CF3−C6H4−
2,4-Cl−C6H3−
C6H5−
2-Cl−C6H4−
2-Cl-C5H3N-5−
3-CF3−C6H4−
2,4-Cl−C6H3−
C6H5−
2-Cl−C6H4−
2-Cl−C5H3N-5−
3-CF3−C6H4−
C6H5−
2-Cl−C6H4−
C6H5−
2-Cl−C6H4−
3-CF3−C6H4−
2,4-Cl−C6H3−
C6H5−
14.5
70.2
81.5
30.6
5.1
11
61.1
67
64
100
64
6a-I-2
6a-I-3
6a-I-4
47.1
61.8
73.8
50.9
100
80.5
73.8
81.3
8.6
16
6a-I-5
52
6a-I-6
42.3
68.5
51.7
38.9
41.5
24.2
68.3
77.8
52.4
65.5
58.3
62
6a-I-7
52
76
76
88
50
40
64
34
52
76
88
94
6a-II-1
6a-II-2
6a-II-3
6a-II-4
6a-II-5
6a-II-6
6a-II-7
6a-III-1
6a-III-5
6a-III-6
6a-III-7
6b-II-3
6b-II-5
6b-III-2
6c-I-1
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
−Cl
−Br
−Br
−Br
−Br
−Br
−Br
−Br
−Br
−Br
−Br
−Br
−Br
−Br
−Br
−H
−H
−H
−H
−H
−H
−H
−H
−C(CH3)3
−C(CH3)3
69
92.5
100
77.2
88.8
70.1
73.8
73.8
77.6
95.7
55.8
72.7
82.5
20.3
40.1
19.3
19.8
77
−CH2−C(CH3)3
−CH2−C(CH3)3
−CH2−C(CH3)3
−CH2−C(CH3)3
−C(CH3)3
70.4
91.3
28.9
1.8
−H
−H
−C(CH3)3
28
28
76
52
52
70
52
64
64
16
34
50
76
40
40
22
22
52
64
64
50
52
100
40
−CH2−C(CH3)3
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)3
−C(CH3)3
−C(CH3)3
−C(CH3)3
−C(CH3)3
−CH2−C(CH3)3
−CH2−C(CH3)3
−CH2−C(CH3)3
−CH2−C(CH3)3
−C(CH3)2CH2Cl
−C(CH3)2CH2Cl
−C(CH3)3
−C(CH3)3
−C(CH3)3
−C(CH3)3
−CH2−C(CH3)3
−CH2−C(CH3)3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
−CH3
8.5
6c-I-4
33.3
78.6
3.8
6c-I-5
6c-I-6
6c-I-7
84.6
49.1
96.2
54.2
90.2
86.1
88
6c-II-1
6c-II-4
6c-II-5
6c-II-6
6c-II-7
6c-III-1
6c-III-4
6c-III-5
6c-III-7
6d-I-1
64.9
11.6
23.4
100
78.1
46.7
79.3
5.9
25.9
18.7
96.6
68.8
95.6
92.2
75
6d-I-7
6d-II-1
6d-II-5
6d-II-6
6d-II-7
6d-III-4
6d-III-5
imidacloprid
chlorantraniliprole
pyridaben
46.8
52.9
16.7
19.3
57.9
89.4
62.3
65.5
94.2
2-Cl−C5H3N-5−
3-CF3−C6H4−
a
100
b
b
c
91.3
29.9
100
d
100
a
b
c
Concentration of imidacloprid was 2 mg L−1. Concentration of chlorantraniliprole was 200 mg L−1. Concentration of chlorantraniliprole was 0.2
d
mg L−1. Concentration of pyridaben was 50 mg L−1.
added. The white solid precipitates were collected by filtration, washed
with petroleum ether (5 mL), and dried to afford 0.39 g of 6a-I-1 as a
white powder: yield, 73%; mp, 188.2−190.0 °C; 1H NMR (300 MHz,
DMSO) δ 9.91 (s, 1H, −NH−), 9.29 (s, 1H, −NH−), 7.66−7.58 (m,
1H, Ar−H), 7.49−7.40 (m, 2H, Ar−H), 7.38−7.28 (m, 2H, Ar−H),
7.26 (d, J = 2.5 Hz, 1H, Ar−H), 5.54 (s, 1H, −NH−), 4.07 (s, 2H,
Ar−CH2−), 3.77 (s, 2H, −CH2−Cl), 2.16 (s, 3H, Ar−CH3), 1.28 (s,
6H, Me2−C); EI-MS (m/z, %) 442 ([M + H]+, 100).
made on a dead/alive basis, and mortality rates were corrected using
Abbott’s formula.16 Evaluations were made on the basis of a
percentage scale of 0−100, in which 0 = no activity and 100 = total
mortality. There was a deviation of 5% in the values. First, 12 mg of
each tested sample was dissolved completely in 2 mL of acetone/
methanol (v/v, 1:1) to obtain a solution having a concentration of 6
mg mL−1. Next, the solution was diluted to 600 mg L−1 with 18 mL of
distilled water containing Triton X-100 (0.05%).
Biological Assay. All bioassays were performed on representative
test organisms reared in the laboratory. Each bioassay was repeated at
Lethal Activity against Cotton Aphid (Aphis gossypii Glover). The
lethal activities of the new compounds against cotton aphid were
evaluated according to the reported procedure.17,18 More than 30
25
1 °C according to statistical requirements. Assessments were
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Scheme 2
Scheme 3
healthy apterous third-instar nymphae on tender Hibiscus syriacus
leaves were dipped into the diluted solutions of the compounds for 5 s;
the superfluous fluid on the leaves was then removed. The treated
insects were kept in an illumination box at 25 1 °C, and mortality
was recorded after 24 h.
Lethal Activity against Carmine Spider Mite (Tetranychus
cinnabarinus). The larvicidal activities of the new compounds against
carmine spider mites were assessed according to the reported
procedure.19,20 More than 20 third-instar mite larvae on Phaseolus
vulgaris leaves were dipped in the diluted solutions of related chemicals
for 5 s; the superfluous liquor on the leaves was then removed. The
larvae were kept in an illumination box at 25 1 °C, and mortality was
recorded 48 h after treatment.
Lethal Activity against Diamondback Moth (Plutella xylostella).
The larvicidal activities of the new compounds against the diamond-
back moth were tested according to the reported procedure.18,21 More
than 20 second-instar moth larvae on cruciferous vegetables leaves
were dipped in the diluted solutions of the compounds for 5 s; the
superfluous liquor was then removed. The larvae were kept in an
illumination box at 25 1 °C, and mortality was recorded 48 h after
treatment.
chloride (Scheme 2). This method yielded many disubstituted
byproducts.
To avoid the formation of disubstituted byproducts, another
synthetic pathway (Scheme 1) was designed, in which isatoic
anhydrides were first treated with acyl chlorides to form
intermediate N-acyl-substituted-1H-benzo[d][1,3]oxazine-2,4-
diones (3′) and then treated with benzylhydrazines to afford
the target compounds. Target compounds 6 were obtained
readily and efficiently without the formation of disubstituted
byproducts. When intermediates 3′ and final compounds 6
were analyzed using mass spectrum, the masses of the final
compounds 6 were confirmed to be accurate. However, the
mass of 3′ compounds was 44 less than that expected.
Characterization with 13C NMR and corresponding analysis
revealed that the intermediate 3′ formed during the reaction
was not stable and could undergo an internal molecular
transformation to form compounds 4 after releasing one
molecule of carbon dioxide as shown in Scheme 3.
The acyl chlorides were first reacted with 6- and/or 8-
substituted 1H-benzo[d][1,3]oxazine-2,4-dione to afford 4a-I−
4d-III; the structures of these intermediates were confirmed by
1H NMR, 13C NMR, and EI-MS. To our knowledge, these have
been reported for the first time. Next, the compounds were
reacted with substituted benzylhydrazine to efficiently form the
corresponding new compounds 6a-I-1−6c-III-7.
Commercial pesticides chlorantraniliprole 95% (0.2 mg L−1),
imidacloprid 95% (2 mg L−1), and pyridaben 97.1% (50 mg L−1)
were used as positive controls against P. xylostella, A. gossypii, and T.
cinnabarinus, respectively, and were treated under the same conditions
with acetone, methanol, and water containing Triton X-100 (0.05%).
Each test was performed in triplicate. The biological activities from the
preliminary assay are summarized in Table 3.
Biological Assay. The results from the assay on the three
representative organisms showed that all of the new
compounds exhibited biological activities to a certain extent
at a concentration of 600 mg L−1, and the substituted groups at
positions X, R1, R2, and R3 had various influences on mortality.
The data presented in Table 3 suggest that the relationship
RESULTS AND DISCUSSION
■
Synthesis of Compounds. For the synthesis of new
anthranilic diamide compounds, the substituted amines were
reacted with isatoic anhydrides,3 followed by acylation with acyl
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Table 4. Inhibition Activity against Carmine Spider Mite of Four Synthetic Compounds at Five Concentrations Compared with
Chlorantraniliprole and Pyridaben
lethal activity (%) against T. cinnabarinus
compd
6a-II-1
400 mg L−1
200 mg L−1
100 mg L−1
50 mg L−1
25 mg L−1
LC50 (mg L−1
)
97.8
92.2
89.6
93.3
40.7
100
82.2
86.4
83.6
64.4
29.9
100
60.8
80.4
62.6
43.3
17.2
100
62.5
74.1
44.9
38.4
13.2
100
30.9
38.4
36.5
26.0
7.4
43.8
27.9
51.7
89.8
632.9
5.5
6a-III-1
6c-I-1
6c-III-5
chlorantraniliprole
pyridaben
97.7
between the substituted groups and biological activities could
be summarized as below.
95.7% from 5.9 and 46.7%, respectively. The substituted groups
at position R2 had impacts on the acaricidal activity depending
on the atoms that were substituted at position X. When a
chlorine atom was substituted at position X, compounds 6a-II-
1, 6a-III-1, 6a-II-2, and 6a-III-6 with tert-butyl or neopentyl
group showed stronger lethal activities against T. cinnabarinus
than compounds 6a-I-1, 6a-I-2, and 6a-I-6 with a 2-chloro-1,1-
dimethylethyl group. On the other hand, when a bromine atom
was located at position X, compounds containing 2-chloro-1,1-
dimethylethyl exhibited better acaricidal activity. Among the
various substituted aromatic groups at position R3, only 2-
chlorophenyl or 3-trifluoromethylphenyl could slightly improve
the lethal activity. Hence, modifying the R2 and R3 groups and
retaining the chlorine and bromine atoms at position X might
effectively improve the acaricidal activity of the new class of
compounds.
Lethal Activity against Carmine Diamondback Moth
(P. xylostella). Of the compounds produced by the structure
modification via the introduction of benzylhydrazine, only
compounds 6a-I-2 and 6d-III-4 showed 100% mortality against
P. xylostella at 600 mg L−1; the other compounds showed
markedly weaker lethal activity than that exerted by the positive
control 95% chlorantraniliprole at 0.2 mg L−1. This suggested
that the replacement of the methyl group by a hydrogen atom
at position R1 remarkably reduced the mortality. Moreover,
when the test concentration was lowered to 200 mg L−1, all
new compounds showed very weak lethal activity.
The tested moths began to die 24 h after treatment, and only
a small part of the corpses changed to yellow or black. This
death pattern resembled that when moths are poisoned by
chlorantraniliprole.
The acaricidal activity of the four compounds 6a-I-1, 6a-III-
1, 6c-I-1, and 6c-III-5, which exhibited good lethal activity
against T. cinnabarinus at a concentration of 600 mg L−1, was
further investigated by conducting the assay at concentrations
of 400, 200, 100, 50, and 25 mg L−1. The lethal activity levels
and calculated LC50 values are shown in Table 4. The results
showed that the four compounds exhibited promising acaricidal
activity even at lower concentrations; for instance, 6a-II-1 and
6a-III-1 showed 62.5 and 74.1% mortality at 50 mg L−1,
respectively, and the LC50 of compound 6a-III-1 was only 27.9
mg L−1.
In all of the tests, the mite larvae stopped moving after 1 h of
treatment, and many larvae died within 24 h after treatment.
The corpses changed to black after 48 h of treatment. This
suggests that the mode of action of these new compounds
against T. cinnabarinus could be different from that of
acylhydrazine compounds.
Lethal Activity against Cotton Aphid (A. gossypii). The
replacement of the hydrogen atom with chlorine or bromine
atom at X position on anthranilic diamides reduced the lethal
activity. For example, the lethal activities of compounds 6d
were higher than those of the corresponding compounds 6a
and 6c; in particular, the mortality rate after treatment with 6d-
III-5 reached 94.2%, but those after treatment with 6c-III-5
and 6a-III-5 were only 18.7 and 58.3%, respectively. Of the
three different groups, tert-butyl, chlorinated tert-butyl (2-
chloro-1,1-dimethylethyl), and neopentyl at position R2, the
chlorinated tert-butyl group remarkably decreased the lethal
activities of 6a-I-1, 6c-I-1, 6a-I-5, and 6c-I-6. The replacement
of neopentyl with tert-butyl did not improve the lethal activity
of the compounds; for instance, the lethal activity against A.
gossypii of 6b-III-2, 6c-III-4, and 6c-III-5 was apparently
decreased. At position R3, the introduction of a chlorine atom,
fluorine atom, and trifluoromethyl group on the aromatic
groups could slightly improve the lethal activity.
In conclusion, more than 40 2-acylamino-substituted N′-
benzylbenzohydrazide derivatives were synthesized and char-
acterized in this study. Some new compounds exhibited good
lethal activities against A. gossypii, P. xylostella, and T.
cinnabarinus. In particular, four compounds, 6a-II-1, 6a-III-1,
6c-I-1, and 6c-III-5, exhibited promising lethal activity against
T. cinnabarinus, and their LC50 values were below 90 mg L−1.
Compound 6a-III-1(X = Cl, R1 = CH3, R2 = tert-butyl, R2 = 2-
chlorophenyl) possessed the best LC50 value of 27.9 mg L−1,
which is not close to that of a commercial acracidal agent
pyridaben (5.5 mg L−1), but it is much better than that of
chlorantraniliprole (632.9 mg L−1). This finding indicates that
the incorporation of the acylhydrazine fragment could improve
the acaricidal activity of the anthranilic diamide compounds as
expected and warrant further studies for designing new
molecules with good biological activity.
Overall, when X was a hydrogen or bromine atom, most of
the compounds had good lethal activity, and especially, the
mortality rates for 6d-II-1, 6c-II-4, 6d-III-5, 6c-II-6, 6c-III-7,
and 6d-I-7 reached >90%. Thus, the anthranilic diamides
containing benzylhydrazine derivatives with no substitution at
position X and a phenyl group at R3 showed markedly
improved lethal activity against aphids.
Lethal Activity against Carmine Spider Mite (T.
cinnabarinus). Chlorination and bromination at position X
have crucial effects on the acaricidal activity; introduction of a
chlorine or bromine atom at X position on the skeleton
structure of anthranilic diamides could remarkably improve the
acaricidal activity. For instance, when the hydrogen atom at
position X of compounds 6d-II-1 and 6d-I-1 was only replaced
by chlorine and bromine atoms, the mortality rates for 6a-II-1
and 6c-I-1 against T. cinnabarinus were increased to 100 and
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AUTHOR INFORMATION
Corresponding Author
*(C.R.) Phone: +86-10-62815944. E-mail: chrui@ippcaas.cn.
(S.L.) Phone: +86-10-62731070. Fax: +86-10-62731070. E-
mail: shangzho@cau.edu.cn.
■
Funding
This work was supported by the National Natural Science
Foundation of China (NNSFC) (No. 20972186 and
21172256), the National Basic Research Program of China
(No. 2010CB126104), and the Green Pesticide Research,
Development and Industrialization (No. 2011BAE06B03).
(18) Zhao, Q.; Li, Y.; Xiong, L.; Wang, Q. Design, synthesis and
insecticidal activity of novel phenylpyrazoles containing a 2,2,2-
trichloro-1-alkoxyethyl moiety. J. Agric. Food Chem. 2010, 58 (8),
4992−4998.
Notes
The authors declare no competing financial interest.
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optimizing a target-diverse scaffold: tetrazolinone derivatives. Bioorg.
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S.; Zhang, Z.; Song, H.; Liu, F. Synthesis and insecticidal activity of N-
tert-butyl-N,N′-diacylhydrazines containing 1,2,3-thiadiazoles. J. Agric.
Food Chem. 2011, 59 (2), 628−634.
ABBREVIATIONS USED
■
HRMS, high-resolution mass spectrometry; MS, mass spec-
trometry; DMF, N,N-dimethylformamide; NCS, N-chlorosuc-
cinimide; NBS, N-bromosuccinimide; THF, tetrahydrofuran;
TLC, thin layer chromatography; NMR, nuclear magnetic
resonance.
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