Research on controllable degradation of sulfonylurea herbicides

Article abstract of DOI:10.1039/c5ra25765d

In order to seek ecologically safer and environmentally benign sulfonylurea herbicides (SU), insight into the structure/bioassay/soil degradation tri-factor relationship was first established. With the introduction of various groups (alkyl, nitro, halogen, cyano etc.) at the 5^th position of its benzene ring, structural derivatives of chlorsulfuron were designed, synthesized, and evaluated for their herbicidal activity. The structures of the title compounds were confirmed by infrared spectroscopy, ultraviolet spectroscopy, ¹H and ¹³C NMR, mass spectrometry, elemental analysis and X-ray diffraction. Bioassay results confirmed that most derivatives retained their superior herbicidal activities in comparison with chlorsulfuron. After investigating the soil degradation behavior of each molecule under set conditions, it was found that structures with electron-withdrawing substituents at the 5^th position of the benzene ring retained their long degradation half-lives, yet the introduction of electron-donating substituents accelerated the degradation rate. These results will provide a valuable clue to further explore the potential controllable degradation of SU and other herbicides, and to discover novel herbicides that are favorable for environmentally and ecologically sustainable development.

Full text of DOI:10.1039/c5ra25765d

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DOI: 10.1039/C5RA25765D
RSC Advances
ARTICLE
Research on Controllable Degradation of Sulfonylurea Herbicides
Xue‐Wen Hua,a Ming‐Gui Chen,a Shaa Zhou,a Dong‐Kai Zhang,a Ming Liu,a Sha Zhou,a Jing‐Bo Liu,a
Kang Lei,a Hai‐Bin Song,a Yong‐Hong Li,a Yu‐Cheng Gub and Zheng‐Ming Lia, *
Received 00th January 20xx,
Accepted 00th January 20xx
In order to seek ecologically safer and environmentally benign sulfonylurea herbicides (SU), an insight of structure /
bioasasay / soil degradation tri‐factor relationship was firstly established. With the introduction of various groups (alkyl,
nitro, halogen, cyano etc) at the 5th position of its benzene ring, a structural derivation of Chlorsulfuron was designed,
synthesized, and evaluated for their herbicidal activity. The title compounds were confirmed by infrared spectroscopy,
DOI: 10.1039/x0xx00000x
www.rsc.org/
1
ultraviolet spectra, H and 13C NMR, mass spectra, elemental analysis and X‐ray diffraction. Bioassay results confirmed
that most derivatives retained their superior herbicidal activities in comparison with Chlorsulfuron. After investigating soil
degradation behavior of each molecule under set conditions, it was found that electron‐withdrawing substituents at 5th
position of benzene ring remained their long degradation half‐lives, yet introduction of electron‐donating substituents
accelerated their degradation rates. These results will provide a valuable clue to further explore the potential controllable
degradation of SU and other herbicides, and to discover novel herbicides which are favorable for environmentally and
ecologically sustainable development.
population and comparatively rather limited arable land in
China, a traditional intensive cultivation practice has been
undertaken to rear 2-3 different crops annually on the same
Introduction
In the past two decades, an important class of herbicides
sulfonylureas (SU), has been developed. These structures
interfere with an unique enzyme existing only in plants,
acetolactate synthase (ALS),1, 2 which results in blocking of the
biosynthesis of three branched-chain amino acids which have
brought outstanding properties such as ultra-low application
rate, good selectivity and negligible mammalian toxicity.3, 4
In recent years, with large scale application of sulfonylurea
herbicides, sometimes the residues have showed up certain
phytotoxicity in crop rotation which are not conducive to
piece of land,10 which requires that herbicides used should
degrade efficiently in soil during different period of this
particular crop rotation system. Sulfonylurea herbicides if
degrade too slow than expected, there will pose a phytotoxicity
problem to the next crop. In summary, our cultivation system
(various crops per land per year) requires a special approach to
integrate sulfonylurea herbicides into our plant protection
practices. During our innovation program, it is anticipated that
“green herbicides” should be highly active as well as to possess
a suitable degradation rate in which residues will not persist in
soil to hurt the next crop seedlings.
environmental protection and ecologically sustainable
development.5,
6
Experiments,7 as well as evidence from
The researches about the relationship of degradation
behaviors and structural modification can contribute to
development of environment-friendly pesticides which are
favorable for ecological protection. Recently, several reports
mentioned that by introducing a special moiety onto the 5th
position of its classical benzene ring, the revised sulfonylurea
structure could exert influence on its degradation rate, i.e.
Iodosulfuron-methyl-sodium, Foramsulfuron, and Flupyrsulfur-
on-methyl-sodium (Fig. 1).10, 11 It inspired us to further explore
the relationship about degradation behaviors and structural
modification of SU molecules. Based on our previous
experience, the introduction of a few substituents at 5th position
of the benzene ring in sulfonylurea structures was favorable to
remain the herbicidal activity, on the other hand, can accelerate
their hydrolysis in water with different pH values.10, 12 To our
knowledge, the current researches about the degradation on
sulfonylurea herbicides mostly focused individually on soil
degradation, hydrolysis or photodegradation under different
farmers in China and Australia, have suggested that under
certain conditions, a few sulfonylurea herbicides persist long
enough to affect the growth of sensitive crops such as grain
legumes, field peas and sunflower in the following season.8, 9 In
2013,
three
sulfonylurea
herbicides,
Chlorsulfuron,
Metsulfuron-methyl, and Ethametsulfuron (Fig. 1), have been
prohibited in China due to their persistent existence in soil
which is harmful to the next rotation crop. Due to the huge
a. State Key Laboratory of Elemento‐Organic Chemistry, Collaborative Innovation
Center of Chemical Science and Engineering (Tianjin), Nankai University, Balitai,
Nankai District, Tianjin 300071, China
b. Jealott’s Hill International Research Centre, Syngenta Ltd, Berkshire RG42 6EY PO
BOX 163, Bracknell, United Kingdom
*Address correspondence to author at Room 518, Bo‐Ling Building, Nankai
University, Balitai, Nankai District, Tianjin 300071, China (Tel: 0086‐22‐23503732;
Fax: 0086‐22‐23505948; E‐mail: nkzml@vip.163.com)
†Electronic Supplementary Information (ESI) available: Containing the crystal data for
compound I‐12, soil degradation curves and structure spectra of all target compounds,
including 1H and 13C NMR, IR, UV and MS. See DOI: 10.1039/x0xx00000x
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1‐3 | 1
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ARTICLE
Journal Name
NH
View Article Online
O
O
O
O
O
O
DOI: 10.1039/C5RA25765D
Cl
O
N
N
O
N
N
O
O
N
N
O
O
O
S
S
S
N
N
N
O
N
N
N
O
N
N
N
O
H
H
H
H
H
H
Metsulfuron-methyl
Ethametsulfuron
Chlorsulfuron
O
N
O
O
O
O
O
N
O
N
O
N
F
F
O
N
O
N
N
O
O
O
F
N
S
N
S
O
I
S
N
N
O
N
N
O
N
N
N
O
H
O
O
O
H
H
H
H
Na
Na
Iodosulfuron-methyl-sodium
Foramsulfuron
Flupyrsulfuron-methyl-sodium
Figure 1 Several structures of sulfonylurea herbicides
CH3
Cl
N
N
SO2NHCONH
N
OCH3
R
R = H (Chlorsulfuron), CH3, C2H5, i-C3H7, N(CH3)2, NO2, F, Cl, Br, I, CN, CF3
Figure 2 Design strategy of target compounds
conditions,13-16 such as pH values, temperature, light, sterile or All reaction reagents were analytical grade, while all analytical
non-sterile, and organic amendments. However, there are no reagents for high performance liquid chromatograph (HPLC)
reports available about the systemic relationship between the were HPLC grade, including methanol, acetonitrile etc. Melting
soil degradation and structural modification of sulfonylurea points of all compounds were determined on an X-4 binocular
herbicides by introducing different substituents onto the 5th microscope (Gongyi Tech. Instrument Co., Henan, China), and
position of their benzene ring. Therefore, this relationship the temperatures were uncorrected. 1H and 13C nuclear
should be studied to guide the search for ecologically safer and magnetic resonance (NMR) spectra were obtained on a Bruker
environmentally benign sulfonylureas.
AV-400 spectrometer (400 MHz), and chemical-shift values (δ)
The classical Chlorsulfuron had been considered once to be a were reported as parts per million (ppm) with tetramethylsilane
popular sulfonylurea herbicide widely applied in grain fields in as the internal standard. Elemental analyses (EA) were
China. In this study, a series of Chlorsulfuron derivatives were measured on a vario EL CUBE elemental analyzer. Infrared (IR)
designed and synthesized with introducing various groups spectra were recorded on a Bruker Vector 22 Fourier transform
(alkyl, nitro, halogen, cyano etc) onto the 5th position of its infrared (FTIR) spectrometer using KBr pellets. Ultraviolet
benzene ring (Fig. 2). The corresponding synthetic routes (UV) spectra were performed on a TU-1810 ultraviolet-visible
towards intermediates II-1
~
II-12 and target compounds I-1
~
spectrophotometer. Mass spectra were recorded on a Thermo-
I-12 were designed and carried out according to Scheme 1 and Finnigan LCQ-Advantage LC/mass detector instrument. HPLC
Scheme 2 respectively. Followed by evaluation of herbicidal data were obtained on a SHIMADZU LC-20AT. Column
activity and investigation of soil degradation under set chromatography purification was carried out using silica gel
conditions, an insight of structure / bioassay / soil degradation (200–300 mesh).
tri-factor relationship was firstly established, which will
provide us important information on environment and
ecological impact during future SU global application.
General synthetic procedure for title compounds I‐1 ~ I‐12
1-(2-Chloro-5-nitrophenylsulfonyl)-3-(4-methoxy-6-methyl-
1,3,5-triazin-2-yl)urea (I-1) was prepared as follows. To a
mixture of intermediate II-1 (1.15g, 4.8 mmol) and a catalytic
amount of triethylenediamine (0.06 g, 0.5 mmol) in anhydrous
toluene (50 mL) was added dropwise oxalyl chloride (3.05 g,
24 mmol) at room temperature. The solution was heated to
60 °C and stirred for 8h, then heated up to 100 °C to continue
reacting for another 12 h. The excess oxalyl chloride and a little
toluene was distilled to remove, followed by the addition of 4-
Materials and methods
Soil
A soil from the plain of Ji’an city (Jiangxi Province, China) was
sampled from the upper layer (0-25 cm), air-dried in the shade
and passed through a 2 mm sieve. It is a red acid soil, with pH
5.41 (soil/water ratio 1:5), soil organic matter content 6.85 g/kg
and 25% water-holding capacity (WHC).
methoxy-6-methyl-1,3,5-triazin-2-amine
.
The mixture was
stirred for 8h at 70 °C, and then concentrated to be purified
through chromatograph on silica gel using dichloromethane /
Reagents and Instruments
2 | J. Name., 2012, 00, 1‐3
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Journal Name
ARTICLE
Cl
Cl
Cl
Cl
Cl
View Article Online
SO3Na
SO2NH2
SO NH
SO2NH2
DOI: 10.1039/C5RA25765D
2
2
1) Oleum
2) NaOH
diazotization
1) ClSO3H
Fe/HCl
2) NH3·H2O
NO2
2
NH2
3
R1
NO2
1
NO2
II-1
II-2 ~ II-6
Cl
Cl
Cl
Cl
Cl
NO2
NH2
SO2Cl
SO2NH2
HNO3/H2SO4
NaNO2/HCl/CH3COOH
Na2S2O4
NH3·H2O
SO2/CuCl/CuCl2/CH3COOH
R2
R2
R2
R2
II-7 & II-8
R2
4a-b
7a-b
5a-b
6a-b
Cl
Cl
Cl
NaBH3CN
SO2NH2
SO2NH2
37% HCHO
CH3
8
CH3COOH
CH3CN
NH2
3
N
Cl
Cl
II-9
Cl
NaBH4/AlCl3
SO2NH2
1)
ClSO3H
2)
THF/reflux
NH3·H2O
R3
II-10 ~ II-12
O
9
10
Cl
R1 = H、F、Cl、Br、I；R2= CN、CF3；
R3 = CH3、C2H5、i-C3H7
Cl
9
Cl
wittig
Pd/C
H2
O
11
12
Compounds
5‐substituted group
Compounds
5‐substituted group
Compounds
II‐9
5‐substituted group
II‐1
II‐2
II‐3
II‐4
NO2
H
II‐5
II‐6
II‐7
II‐8
Br
I
N(CH3)2
CH3
II‐10
F
CN
CF3
II‐11
C2H5
Cl
II‐12
i‐C3H7
Scheme 1 Synthesis of intermediates II
ethyl acetate (v/v 5:1) as eluent to give white solid I-1
Compounds I-2 ~ I-12 were synthesized similarly.
.
1350 and 1165 (SO2). δH (400 MHz; (CD3)CO) 2.53 (3H, s,
CH3), 4.04 (3H, s, OCH3), 7.62 – 7.69 (2H, m, Ph-H), 7.75 (1H,
t, J 7.6, Ph-H), 8.26 (1H, d, J 7.9, Ph-H), 9.77 (1H, s, NH),
12.96 (1H, s, NH). δC (101 MHz; (CD3)CO) 24.6, 55.0, 127.5,
131.4, 131.8, 132.7, 135.2, 136.5, 148.2, 164.3, 170.8, 178.9.
m/z (ESI) [M-H]- Found: 355.9. Calc. for C12H11ClN5O4S-:
356.0.
1-(2-Chloro-5-nitrophenylsulfonyl)-3-(4-methoxy-6-methyl-
1,3,5-triazin-2-yl)urea (I-1)
White gramular, yield 53%, mp 144-146 °C. Found: C, 35.7; H,
2.7; N, 20.8. Calc. for C12H11ClN6O6S: C, 35.7; H, 2.75; N,
20.8 %. λmax(CH2Cl2)/nm 235. νmax (KBr)/cm-1 1728 (C=O),
1354 and 1173 (SO2). δH (400 MHz; (CD3)CO) 2.40 (3H, s,
CH3), 3.90 (3H, s, OCH3), 7.88 (1H, d, J 8.7, Ph-H), 8.45 (1H,
1-(2-Chloro-5-fluorophenylsulfonyl)-3-(4-methoxy-6-methyl-
1,3,5-triazin-2-yl)urea (I-3)
d, J 8.6, Ph-H), 8.83 (1H, s, Ph-H), 9.81 (1H, s, NH), 13.15 (1H, White gramular, yield 59%, mp 165-166 °C. Found: C, 38.6; H,
s, NH). δC (101 MHz; (CD3)CO) 25.5, 55.9, 128.4, 130.3, 3.0; N, 18.5. Calc. for C12H11ClFN5O4S: C, 38.4; H, 2.95; N,
134.5, 138.6, 139.0, 147.4, 149.1, 165.1, 171.8, 179.8. m/z (ESI) 18.6 %. λmax (CH2Cl2)/nm 233. νmax (KBr)/cm-1 1716 (C=O),
[M-H]- Found: 400.9. Calc. for C12H10ClN6O6S-: 401.0.
1362 and 1166 (SO2). δH (400 MHz; (CD3)CO) 2.52 (3H, s,
CH3), 4.03 (3H, s, OCH3), 7.44 – 7.61 (1H, m, Ph-H), 7.67 –
7.76 (1H, m, Ph-H), 7.81 – 8.01 (1H, m, Ph-H), 9.81 (1H, s,
NH), 13.03 (1H, s, NH). δC (101 MHz; (CD3)CO) 24.6, 55.0,
119.7 (d, J 26.7), 122.3 (d, J 23.2), 126.8 (d, J 3.6), 133.8 (d, J
7.8), 138.1 (d, J 7.4), 148.2, 160.5 (d, J 249.2), 164.2, 170.8,
1-(2-Chlorophenylsulfonyl)-3-(4-methoxy-6-methyl-1,3,5-
triazin-2-yl)urea (I-2)
White gramular, yield 58%, mp 163-165 °C. Found: C, 40.3; H,
3.4; N, 19.5. Calc. for C12H12ClN5O4S: C, 40.3; H, 3.4; N,
19.6 %. λmax (CH2Cl2)/nm 234. νmax (KBr)/cm-1 1716 (C=O),
This journal is © The Royal Society of Chemistry 20xx
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ARTICLE
Journal Name
CH3
N
View Article Online
DOI: 10.1039/C5RA25765D
Cl
Cl
R
Cl
N
N
SO2NHCONH
SO2NH2
SO2NCO
(i)
(ii)
OCH3
R
R
I
II
III
Products
I‐1
R
Products
I‐5
R
Br
I
Products
I‐9
R
NO2
N(CH3)2
I‐2
H (Chlorsulfuron)
I‐6
I‐10
CH3
C2H5
I‐3
F
I‐7
CN
CF3
I‐11
I‐4
Cl
I‐8
I‐12
i‐C3H7
Scheme 2 Synthesis of target compounds. Reagents and conditions: (i) (COCl)2, DABCO, anhydrous toluene, 60 ºC, 8h; 60
– 100 ºC; 100 ºC, 12h; (ii) 4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2‐amine, anhydrous toluene, 70 ºC, 8h.
178.9. δF (376 MHz, (CD3)CO) -114.1. m/z (ESI) [M-H]- White gramular, yield 58%, mp 176-178 °C. Found: C, 40.9; H,
Found: 373.9. Calc. for C12H10ClFN5O4S-: 374.0.
3.4; N, 21.6. Calc. for C13H11ClN6O4S: C, 40.8; H, 2.9; N,
22.0 %. λmax (CH2Cl2)/nm 234. νmax (KBr)/cm-1 1710 (C=O),
1356 and 1166 (SO2). δH (400 MHz; (CD3)CO) 2.54 (3H, s,
CH3), 4.05 (3H, s, OCH3), 7.95 (1H, d, J 8.3, Ph-H), 8.18 (1H,
dd, J 1.9, 8.3, Ph-H), 8.56 (1H, d, J 1.9, Ph-H), 9.86 (1H, s,
NH), 13.21 (1H, s, NH). δC (101 MHz; (CD3)CO) 24.6, 55.0,
111.6, 116.4, 133.2, 136.0, 136.5, 138.0, 148.6, 164.3, 170.8,
178.8. m/z (ESI) [M-H]- Found: 380.9. Calcd for
C13H10ClN6O4S-: 381.0.
1-(2, 5-Dichlorophenylsulfonyl)-3-(4-methoxy-6-methyl-1,3,5-
triazin-2-yl)urea (I-4)
White gramular, yield 62%, mp 164-165 °C. Found: C, 36.95;
H, 3.1; N, 17.5. Calc. for C12H11Cl2N5O4S: C, 36.75; H, 2.8; N,
17.8 %. λmax (CH2Cl2)/nm 233. νmax (KBr)/cm-1 1716 (C=O),
1368 and 1171 (SO2). δH (400 MHz; (CD3)CO) 2.53 (3H, s,
CH3), 4.04 (3H, s, OCH3), 7.73 (1H, d, J 8.6, Ph-H), 7.80 (1H,
dd, J 8.6, 2.5, Ph-H), 8.19 (1H, d, J 2.5, Ph-H), 9.88 (1H, s,
NH), 13.13 (1H, s, NH). δC (101 MHz; (CD3)CO) 24.6, 55.0,
130.1, 132.1, 132.7, 133.4, 134.9, 138.0, 148.3, 164.2, 170.8,
1-(2-Chloro-5-trifluoromethylphenylsulfonyl)-3-(4-methoxy-6-
methyl-1,3,5-triazin-2-yl)urea (I-8)
178.8. m/z (ESI) [M-H]- Found: 389.9. Calc. for White gramular, yield 57%, mp 136-138 °C. Found: C, 36.7; H,
C12H10Cl2N5O4S-: 390.0.
2.7; N, 16.4. Calc. for C13H11ClF3N5O4S: C, 36.7; H, 2.6; N,
16.45 %. λmax (CH2Cl2)/nm 233. νmax (KBr)/cm-1 1716 (C=O),
1361 and 1177 (SO2). δH (400 MHz; (CD3)CO) 2.54 (3H, s,
CH3), 4.05 (3H, s, OCH3), 7.97 (1H, d, J 8.4, Ph-H), 8.13 (1H,
ddd, J 0.5, 2.2, 8.4, Ph-H), 8.49 (1H, d, J 2.1, Ph-H), 9.89 (1H, s,
NH), 13.21 (1H, s, NH). δC (101 MHz; (CD3)CO) 24.6, 55.0,
123.2 (q, J 273.2), 129.0 (q, J 34.1), 129.5 (q, J 3.9), 131.8 (q, J
3.4), 133.3, 135.9, 137.6, 148.3, 164.2, 170.8, 178.9. δF (376
MHz, (CD3)CO) -63.32. m/z (ESI) [M-H]- Found: 424.0. Calc.
for C13H10ClF3N5O4S-: 424.0.
1-(2-Chloro-5-bromophenylsulfonyl)-3-(4-methoxy-6-methyl-
1,3,5-triazin-2-yl)urea (I-5)
White gramular, yield 65%, mp 165-167 °C. Found: C, 33.4; H,
2.8; N, 15.85. Calc. for C12H11BrClN5O4S: C, 33.0; H, 2.5; N,
16.0 %. λmax (CH2Cl2)/nm 235 nm. νmax (KBr)/cm-1 1715
(C=O), 1369 and 1169 (SO2). δH (400 MHz; (CD3)CO) 2.52
(3H, s, CH3) 4.03 (3H, s, OCH3), 7.64 (1H, d, J 8.5, Ph-H), 7.92
(1H, d, J 8.5, Ph-H), 8.32 (1H, s, Ph-H), 9.86 (1H, s, NH),
13.10 (1H, s, NH). δC (101 MHz; (CD3)CO) 24.6, 55.0, 120.1,
130.8, 133.6, 134.9, 137.9, 138.1, 148.3, 164.2, 170.8, 178.8.
m/z (ESI) [M-H]- Found: 433.8. Calc. for C12H10BrClN5O4S-:
433.9.
1-(2-Chloro-5-dimethylaminophenylsulfonyl)-3-(4-methoxy-6-
methyl-1,3,5-triazin-2-yl)urea (I-9)
White gramular, yield 60%, mp 172-174 °C. Found: C, 41.6; H,
4.4; N, 20.5. Calc. for C14H17ClN6O4S: C, 41.95; H, 4.3; N,
20.9 %. λmax (CH2Cl2)/nm 234. νmax (KBr)/cm-1 1713 (C=O),
1355 and 1164 (SO2). δH (400 MHz; (CD3)CO) 2.52 (3H, s,
CH3), 3.05 (6H, s, N(CH3)2), 4.04 (3H, s, OCH3), 6.98 (1H, d, J
8.9, Ph-H), 7.38 (1H, d, J 8.9, Ph-H), 7.49 (1H, s, Ph-H), 9.74
(1H, s, NH), 12.84 (1H, s, NH). δC (101 MHz; (CD3)CO) 24.6,
39.5, 54.9, 115.0, 116.3, 117.4, 131.9, 136.5, 148.1, 149.1,
164.2, 170.8, 178.8. m/z (ESI) [M-H]- Found: 399.0. Calc. for
C14H16ClN6O4S-: 399.1.
1-(2-Chloro-5-iodophenylsulfonyl)-3-(4-methoxy-6-methyl-
1,3,5-triazin-2-yl)urea (I-6)
White gramular, yield 57%, mp 179-181 °C. Found: C, 29.9; H,
2.4; N, 14.5. Calc. for C12H11ClIN5O4S: C, 29.8; H, 2.3; N,
14.5 %. λmax (CH2Cl2)/nm 234. νmax (KBr)/cm-1 1728 (C=O),
1358 and 1170 (SO2). δH (400 MHz; (CD3)CO) 2.51 (3H, s,
CH3), 4.02 (3H, s, OCH3), 7.47 (1H, d, J 8.3, Ph-H), 8.08 (1H,
d, J 8.1, Ph-H), 8.48 (1H, d, J 1.8, Ph-H), 9.67 (1H, s, NH),
13.02 (1H, s, NH). m/z (ESI) [M-H]- Found: 481.8. Calc. for
C12H10ClIN5O4S-: 481.9.
1-(2-Chloro-5-methylphenylsulfonyl)-3-(4-methoxy-6-methyl-
1,3,5-triazin-2-yl)urea (I-10)
1-(2-Chloro-5-cyanophenylsulfonyl)-3-(4-methoxy-6-methyl-
1,3,5-triazin-2-yl)urea (I-7)
White gramular, yield 61%, mp 187-188 °C. Found: C, 42.0; H,
3.7; N, 18.8. Calc. for C13H14ClN5O4S: C, 42.0; H, 3.8; N,
4 | J. Name., 2012, 00, 1‐3
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18.8 %. λmax (CH2Cl2)/nm 235. νmax (KBr)/cm-1 1711 (C=O), wR = 0.1090. Hydrogen atoms were observed and refined with
View Article Online
DOI: 10.1039/C5RA25765D
1353 and 1165 (SO2). δH (400 MHz; (CD3)CO) 2.33 (3H, s, a fixed value of their isotropic displacement parameter. The
Ph-CH3), 2.38 (3H, s, CH3), 3.90 (3H, s, OCH3), 7.40 (2H, s, correction for absorption was multi-scan, Tmin = 0.9304, Tmax
=
Ph-H), 7.90 (1H, s, Ph-H), 9.64 (1H, s, NH), 12.80 (1H, s, NH). 0.9574.
δC NMR (101 MHz; (CD3)CO) 20.7, 25.5, 55.8, 129.2, 132.4,
133.7, 136.6, 137.0, 138.9, 149.0, 165.2, 171.7, 179.7. m/z (ESI)
[M-H]- Found: 369.9. Calc. for C13H13ClN5O4S-: 370.0.
Herbicidal Activity Screening
Herbicidal activities were tested in greenhouse (25 ± 2 ºC)
according to the following method.11 The emulsions of purified
compounds (10.0 mg) were respectively prepared by dissolving
them in N,N-dimethylformamide (1 mL) with the addition of a
1-(2-Chloro-5-ethylphenylsulfonyl)-3-(4-methoxy-6-methyl-
1,3,5-triazin-2-yl)urea (I-11)
White gramular, yield 66%, mp 151-153 °C. Found: C, 43.75; certain amount of Tween 80 (1.0 g) in distilled water (1000
H, 4.1; N, 18.0. Calc. for C14H16ClN5O4S: C, 43.6; H, 4.2; N, mL). The mixture of the same amount of N,N
-
18.15 %. λmax (CH2Cl2)/nm 234. νmax (KBr)/cm-1 1714 (C=O), dimethylformamide, Tween 80, and distilled water was used as
1354 and 1168 (SO2). δH (400 MHz; (CD3)CO) 1.27 (3H, t, J a negative control and Chlorsulfuron was employed as a
7.6, CH2CH3), 2.52 (3H, s, CH3), 2.78 (2H, q, J 7.6, CH2CH3), positive control. Each experiment was performed in triplicate.
4.03 (3H, s, OCH3), 7.56 (1H, d, J 8.2, Ph-H), 7.59 (1H, dd, J The solutions of tested compounds were sprayed with a
1.9, 8.2, Ph-H), 8.06 (1H, d, J 1.7, Ph-H), 9.76 (1H, s, NH), laboratory belt sprayer delivering a 750 L/ha (1 ha=10000 m2)
12.91 (1H, s, NH). δC (101 MHz; (CD3)CO) 14.7, 24.6, 27.7, spray volume.
55.0, 128.4, 131.7, 131.8, 134.6, 136.2, 144.1, 148.2, 164.2,
Soil treatment: sandy clay (100.0 g) in a plastic box (11.0
170.8, 178.8. m/z (ESI) [M-H]- Found: 384.0. Calc. for cm×7.5 cm×6.0 cm) was wetted with distilled water. Fifteen
C14H15ClN5O4S-: 384.0.
sprouting seeds of the test weeds were planted in the fine earth
(0.6 cm depth) in the glasshouse and sprayed with the test
compound solution. After spraying for 28 days, the ground
fresh weight was measured and compared to the negative group
to calculate the inhibition percent of fresh weight. The test
1-(2-Chloro-5-isopropylphenylsulfonyl)-3-(4-methoxy-6-
methyl-1,3,5-triazin-2-yl)urea (I-12)
White gramular, yield 59%, mp 137-138 °C. Found: C, 45.1; H,
4.5; N, 17.4. Calc. for C15H18ClN5O4S: C, 45.1; H, 4.5; N,
17.5 %. λmax (CH2Cl2)/nm 234. νmax (KBr)/cm-1 1715 (C=O),
1357 and 1164 (SO2). δH (400 MHz; (CD3)CO) 1.29 (6H, d, J
6.9, CH(CH3)2), 2.52 (3H, s, CH3), 3.01 – 3.19 (1H, m, CH),
4.03 (3H, s, OCH3), 7.57 (1H, d, J 8.2, Ph-H), 7.63 (1H, dd, J
2.1, 8.2, Ph-H), 8.09 (1H, d, J 2.1, Ph-H), 9.80 (1H, s, NH),
12.97 (1H, s, NH). δC (101 MHz; (CD3)CO) 23.0, 24.6, 33.4,
55.0, 128.5, 130.6, 131.7, 133.1, 136.2, 148.2, 148.5, 164.3,
170.8, 178.8. m/z (ESI) [M-H]- Found: 398.0. Calc. for
C15H17ClN5O4S-: 398.1.
weed involves Brassica campestris
Echinochloa crusgalli and Digitaria adscendens
, Amaranthus tricolor,
.
Foliage spray: seedlings (one leaf and one stem) of the test
weeds were sprayed with the test compound solution at the
same rate as used for the soil treatment test. The calculated
method and test materials were as same as soil treatment.
Soil Degradation Investigating
The soil degradation of Chlorsulfuron derivatives were
investigated in acid soil (pH 5.41) with the initial additive
concentration of 5 mg a.i./kg under laboratory conditions at 25
ºC and a moisture content corresponding to 70% field capacity.
The samples were analysed by a high-performance liquid
chromatograph (HPLC) technique. The methods employed a
Shimadzu HPLC (series LC-20AT), equipped with a binary
pump (Shimadzu, LC-20AT), an UV/VIS detector (Shimadzu,
SPD-20A), an auto sampler (Shimadzu, SIL-20A), a Shimadzu
shim-pack VP-ODS column (5µm, 250 mm × 4.6 mm)
connected to a Shimadzu shim-pack GVP-ODS (10 mm × 4.6
mm) precolumn, and a computer (model Dell) for carrying out
the analysis. The mobile phases consisted of methanol (A) and
phosphoric acid solution in double distilled water (B) (pH =
3.00) with a flow rate of 0.8 ~ 1.0 mL/min. The injection
volume was set at 10 μL, and the detector wavelength was
adjusted at 235 nm according to the UV spectra of the target
compounds. The specific HPLC analytical conditions, which
could ensure good separation between soil contaminants and
standard samples, were listed in Table 1. From the results, the
HPLC analytical methods were adjusted according to the
X‐ray Diffraction Analysis
The target compound I-12 was recrystallized by slow
evaporation from a mixture of ethyl acetate and n-hexane to
afford a colourless single crystal with dimensions of 0.20 ×
0.18 × 0.12 mm, which was mounted on a glass fiber for X-ray
diffraction analysis. The data were collected at 113(2) K on a
Rigaku Saturn 724 CCD diffractometer with graphite
monochromated Mo Kα radiation (λ =0.71073 Å), θmax = 27.91°.
The molecular formula is C15H18ClN5O4S and the formula
weight is 399.85. The crystal was a monoclinic system, space
group P2(1)/n, with unit cell parameters: a = 9.4336 (19) Å; b =
11.524 (2) Å; c = 16.608 (3) Å, V = 1773.1 (6) Å3, Z = 4,
density (calculated) = 1.498 g/cm3, and linear absorption
coefficient 0.366 mm-1. In total, 17,832 integrated reflections
were collected, reducing to a data set of 4,240 unique with Rint
=
0.0549, and completeness of data (to theta = 27.91°) of 99.7%.
Data were collected and processed using Crystal Clear (Rigaku).
An empirical absorption correction was applied using
CrystalClear (Rigaku). The structure was solved by direct
methods with the SHELXS-97 program.17 Full-matrix least-
squares refinement based on F2 using the weight of
different molecular characteristics. Therefore, the Log
for target compounds were calculated with Prediction System
of Log (CISOC-Log
) as previously reported,18 and
P values
P
P
1/[σ2 Fo2)+(0.0567 )2+0.3384
( P P gave final values of R = 0.0439,
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J. Name., 2013, 00, 1‐3 | 5
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Journal Name
Table 1 Analytical conditions for the soil degradation of target compounds
View Article Online
HPLC analysis conditions
(wavelength, flow rate,
mobile phase (v/v))
Adding mass
fraction
(mg/kg)
AverageDOI: 10.1039/C5RA25765D
Coefficient of
recovery
Extraction solvents
(v/v)
Compounds
R
NO2
H
Variation/%
rate/%
5
2
0.5
5
2
0.5
5
2
0.5
5
2
0.5
5
2
0.5
5
2
0.5
5
2
0.5
5
2
0.5
5
2
0.5
5
2
0.5
5
2
0.5
5
2
0.5
86.71
83.56
79.43
81.81
82.35
80.23
86.40
82.79
75.57
84.51
81.75
72.08
75.50
73.80
72.26
84.09
82.07
83.58
91.06
87.79
73.44
81.25
83.41
88.05
74.53
72.91
72.80
83.90
84.59
88.69
84.95
83.66
75.10
93.52
91.40
91.31
1.34
1.89
4.14
1.30
4.04
1.55
1.44
1.60
2.55
2.77
1.40
1.64
3.84
3.27
1.84
1.80
1.46
2.47
1.03
4.03
4.22
1.84
3.43
3.41
1.67
1.31
2.59
4.41
1.20
1.32
4.35
1.50
2.35
1.10
1.62
3.63
235 nm, 1.0 mL/min,
CH3OH/H2O (pH 3.0) =
60/40
acetone/DCM/Phosph
oric acid solution (pH
2.0) = 40/5/5
I‐1
I‐2
235 nm, 0.8 mL/min,
CH3OH/H2O (pH 3.0) =
60/40
acetone/THF/DCM =
30/5/5
235 nm, 1.0 mL/min,
CH3OH/H2O (pH 3.0) =
60/40
acetone/DCM/Phosph
oric acid solution (pH
2.0) = 40/5/5
I‐3
F
235 nm, 1.0 mL/min,
CH3OH/H2O (pH 3.0) =
65/35
acetone/THF/DCM =
30/10/10
I‐4
Cl
235 nm, 1.0 mL/min,
CH3OH/H2O (pH 3.0) =
65/35
acetone/THF/DCM =
30/10/10
I‐5
Br
235 nm, 0.8 mL/min,
CH3OH/H2O (pH 3.0) =
70/30
acetone/THF/DCM =
30/5/5
I‐6
I
235 nm, 0.8 mL/min,
CH3OH/H2O (pH 3.0) =
60/40
acetone/THF/DCM/Ph
osphoric acid solution
(pH 2.0) = 30/10/10/10
I‐7
CN
235 nm, 0.8 mL/min,
CH3OH/H2O (pH 3.0) =
70/30
acetone/THF/DCM =
30/20/10
I‐8
CF3
N(CH3)2
CH3
C2H5
i‐C3H7
235 nm, 0.8 mL/min,
CH3OH/H2O (pH 3.0) =
65/35
acetone/THF/DCM =
30/10/10
I‐9
235 nm, 0.8 mL/min,
CH3OH/H2O (pH 3.0) =
65/35
acetone/THF/DCM =
30/10/10
I‐10
I‐11
I‐12
235 nm, 1.0 mL/min,
CH3OH/H2O (pH 3.0) =
65/35
acetone/THF/DCM =
30/5/5
235 nm, 0.8 mL/min,
CH3OH/H2O (pH 3.0) =
70/30
acetone/THF/DCM =
30/5/5
Note: Compound I‐2 represent Chlorsulfuron, and the determination of soil recovery rates was performed in quintuplet at each adding
mass fraction to calculate the average recovery rate and coefficient of variation.
displayed in Fig
selected in accordance with Log
.
3
. Then the appropriate extraction solvent was was added to adjust the soil moisture content to approximately
values by measuring soil 70% field capacity. The bottles were then stoppered with a
P
recovery rates and coefficients of variation (Table 1). When all cotton plug and put into an ecological incubator (temperature
the analytical methods were ready, the soil degradation 25 ± 1 ºC, humidity 80%) to incubate in the dark prior to
behaviors were investigated under set conditions.
treatment. In the cultivating process, the moisture content in
Testing soil (20.00 g, air-dry weight) passed through 2 mm Erlenmeyer flask was adjusted regularly to maintain the
sieve was weighed into six groups of 150 mL Erlenmeyer flasks, original water-holding state. The samples were taken
three in each group respectively, and added standard solutions periodically and added the extraction solvent for extraction.
at a concentration of 5 mg a.i./kg. Followed the solvent The mixture was shaken for 2h at 200 r/min with an oscillator,
volatilizing completely under a fume hood, the soil was and then centrifuged for 2 min at 6500 r/min with a Thermo
thoroughly mixed, and an appropriate volume of distilled water Scientific Legend Mach 1.6 R centrifuge to obtain supernatant
6 | J. Name., 2012, 00, 1‐3
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elemental analysis (EA). Several unique structural characteristics
DOI: 10.1039/C5RA25765D
were also revealed via the crystal structure of compound I-12 (Fig.
4).
3.5
3
View Article Online
2.5
2
Crystal structure analysis
Several molecular characteristics were apparently presented upon
crystal structure analysis of compound I-12 (CCDC No. 1426721).
From the data, the bond angles of O(1) – S(1) – C(1), O(2) – S(1) –
C(1), and N(1) – S(1) – C(1) were 107.86(8)º, 109.27(8)º, and
106.65(8)º respectively, indicating the sp3 hybridization state of the
S(1) atom. The sum of O(3) – C(10) – N(1), O(3) – C(10) – N(2),
and N(1) – C(10) – N(2) angles was 359.99º, indicating the sp2
hybridization state of the C(10) atom. The torsion angle of O(3) –
C(10) – N(2) – H(2) was 0.083(14)º, while 176.539(16)º for O(3) –
C(10) – N(1) – H(1). The dihedral angle between two planes
containing N(1) – C(10) – O(3) – N(2) and C(11) – N(3) – C(12) –
N(4) – C(13) – N(5) was 13.379(70)º, which showed both planes
were non-planar. In the meantime, the dihedral angle between the
benzene ring and the triazine ring was 66.914(52)º, demonstrating
their non-plane.
1.5
1
I-7 I-2 I-1 I-3 I-9 I-10 I-4 I-5 I-11 I-8 I-6 I-12
Figure 3 The relationship of structures and calculated Log P
values for target compounds
which was concentrated later in vacuum at room temperature.
After the residue was extracted by dichloromethane (30 mL ×
2), the combined organic layer was dried by anhydrous sodium
sulfate, filtered and concentrated up to dryness. The product
was dissolved in acetonitrile (10 mL), and filtered through a
filter membrane (0.22 µm) to HPLC analysis. Each sample was
taken six times for drawing first-order kinetic curves, and every
time was performed in triplet for statistical analysis.
Biological assay
The herbicidal activities of target compounds, with Chlorsulfuron
as a positive control, against four weeds representing
monocotyledonous and dicotyledonous plants at 150 g/ha and 30
g/ha respectively, were shown in Table 2 and comprehensively
evaluated. From the data, in a given category, no matter soil
treatment or foliage spray, the herbicidal activities of the title
compounds against dicotyledonous plants were higher than those
against monocotyledons, including positive control Chlorsufuron
(compound I-2). In addition, no compounds displayed good
inhibition rate against Digitaria sanguinalis regardless of which
spraying methods adopted whereas, on the other hand, almost all of
the target compounds exhibited excellent herbicidal activity against
Amaranthus tricolor at 30 g/ha. Interestingly, the structure I-9
containing dimethylamino group at 5th position exhibited superior
herbicidal activities under soil treatment at 150 g/ha against Brassica
campestris, Amaranthus tricolor, Echinochloa crusgalli, and
Digitaria sanguinalis with the inhibition percent of 100, 98.5, 92.6,
and 91.3% respectively. In the meantime, the introduction of halo,
nitro, dimethylamino, and methyl groups at 5th position was
favorable to remain or improve the herbicidal activities of the target
compounds, while ethyl, isopropyl, cyano, and trifluoromethyl
substituents decreased the inhibition rates. For example, the
Results and discussion
Synthetic chemistry
Herein, the important intermediates II were designed and
synthesized according to the methods in Scheme 1. Firstly,
intermediate II-1 was prepared from 1-chloro-4-nitrobenzene 1
through sulfonation and nucleophilic substitution reactions as
previously reported,19 and then reduced to provide 2-chloro-4-
aminobenzenesulfonamide 3 with Fe/HCl in ethanol which was
diazotized to get intermediates II-2 ~ II-6 with diffident diazo
reagents as reported literatures.20-24 Compound II-7 (or II-8) was
synthesized by a process starting from nitration of material 4a (or 4b)
with fuming nitric acid/concentrated sulfuric acid,25, 26 followed by
reduction of nitro group with Na2S2O4, diazotization of amino
group27 and then nucleophilic substitution reaction. Compound 3
was transformed to intermediate II-9 by reaction with NaBH3CN,
formalin, CH3COOH in acetronitrile.28 4'-Chloroacetophenone 9
was reduced to produce 1-chloro-4-ethylbenzene 10 with
NaBH4/AlCl3 in tetrahydrofuran.29 Synthesis of 1-chloro-4-
isopropylbenzene 12 from material 9 usually involves wittig reaction,
reduction of olefin group with Pd/C/H2 in methanol. Intermediate II-
10 was synthesized by reaction of 1-chloro-4-methylbenzene 8 with
chlorosulfonic acid,30, 31 ammonium hydroxide, and compounds II-
11, II-12 were prepared as the same manner, which all the structures
were also confirmed by 13C-HMBC. The synthetic route towards the
target compounds was summarized in Scheme 2. Subsequently,
twelve molecules were synthesized from intermediates II.
Compounds III were prepared by reaction of materials II with oxalyl
chloride and a catalytic amount of triethylenediamine (DABCO),
and converted to products I through reaction with 4-methoxy-6-
methyl-1,3,5-triazin-2-amine in anhydrous toluene. All target
compounds were purified by chromatography on silica gel using
dichloromethane/ethyl acetate as eluent. The synthesized compounds
were identified and characterized by infrared spectroscopy (IR),
ultraviolet (UV) spectra, 1H NMR, 13C NMR, mass spectra and
Figure 4 The crystal structure of compound I‐12
J. Name., 2013, 00, 1‐3 | 7
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Table 2 Herbicidal activity of the target compounds
View Article Online
DOI: 10.1039/C5RA25765D
Herbicidal activity (inhibition percent)/%
Soil treatment Foliage spray
Echinoc‐ Digitar‐
Concentra
tion
(g a.i./ha)
Compo
unds
Echinoc‐ Digitar‐
hloa ia
crusgall‐ sangui‐
R
Brassica Amaran
Brassica
campestri
‐s
Amaran
‐thus
tricolor
hloa
ia
campest
‐thus
tricolor
crusgall‐ sangui‐
‐ris
i
nalis
i
nalis
30
150
30
84.0
98.1
100
60.6
98.5
99.2
100
65.4
86.2
67.9
88.0
78.6
81.1
41.6
62.1
18.5
49.8
57.2
72.8
40.7
50.6
1.2
6.8
100
100
100
100
86.8
100
100
100
87.2
100
100
100
44.9
62.1
100
100
100
100
100
100
100
100
58.6
75.8
98.3
100
100
100
100
100
100
100
100
100
100
100
100
100
78.8
100
100
100
100
100
99.2
100
100
100
74.9
85.1
79.2
84.7
64.8
89.8
59.3
66.7
45.2
64.0
59.7
64.4
35.8
47.5
22.5
38.1
69.8
88.3
36.9
55.7
15.4
33.8
11.1
18.1
0
I‐1
I‐2
NO2
H
12.6
14.6
69.9
20.4
72.8
16.5
59.2
3.9
0
0
150
30
100
0
97.5
99.7
96.2
99.7
80.8
99.1
100
99.2
99.8
99.2
100
16.7
29.7
0
I‐3
F
150
30
I‐4
Cl
150
30
12.4
0
99.2
100
I‐5
Br
150
30
33.0
1.0
0
100
3.8
8.1
9.6
13.9
8.1
27.5
16.7
38.3
0
I‐6
I
150
30
100
100
8.7
17.6
32.7
61.0
95.6
93.7
100
84.8
88.6
88.6
98.5
69.7
98.5
100
0
I‐7
CN
150
30
10.7
16.5
20.4
38.8
91.3
29.1
39.8
0
I‐8
CF3
N(CH3)2
CH3
C2H5
i‐C3H7
150
30
25.1
38.3
92.6
19.3
59.7
20.2
33.3
8.6
I‐9
150
30
95.6
97.5
64.2
87.7
54.1
95.6
I‐10
I‐11
I‐12
150
30
100
16.7
9.6
39.7
0
82.6
97.0
52.3
80.3
150
30
36.9
14.6
30.1
150
29.2
16.7
Note: Compound I‐2 represent Chlorsulfuron.
herbicidal activities of compounds I-1 (5-nitro), I-3 (5-fluoro), I-4 were chosen to measure the soil recovery rates respectively.
(5-chloro), I-5 (5-bromo), I-6 (5-iodo), I-9 (5-dimethylamino), and Interestingly, a ternary mixed system, acetone / tetrahydrofuran /
I-10 (5-methyl) were similar to the positive control Chlorsulfuron (I- dichloromethane, was found to be favorable to extract the standard
2), however, the products I-7 (5-cyano), I-8 (5-trifluoromethyl), I-11 samples. At last, the disappearance of SU was reported by plotting
(5-ethyl), and I-12 (5-isopropyl) displayed relatively weak herbicidal the concentration as a function of the degradation time. Each
activities when compared with Chlorsufuron. From the above results, experiment was performed in triplicate to measure the standard
it was concluded that most compounds in general showed good deviation. The corresponding first-order kinetic equations and half-
herbicidal activities in comparison with Chlorsulfuron except life (t1/2) periods were shown in Table 3 respectively. From the data,
structures I-7 and I-12.
it was concluded that the introduction of electron-donating
substituents at 5th position of the benzene ring inclined to accelerate
the degradation rates, while with the electron-withdrawing groups to
prolong the half-life periods of target compounds in comparison with
Chlorsulfuron (I-2). For example, the half-life data of I-9 (5-
dimethylamino), I-11 (5-ethyl), I-12 (5-isopropyl), and I-10 (5-
methyl) were 0.96, 7.89, 9.4, and 11.16 days respectively, which
were shorter than that of Chlorsulfuron (t1/2 = 12.25 days), however,
those of compounds I-6 (5-iodo), I-8 (5-trifluoromethyl), I-3 (5-
fluoro), I-4 (5-chloro), I-5 (5-bromo), I-1 (5-notro), and I-7 (5-cyano)
were 14.78, 17.73, 18.43, 19.2, 19.58, 21.53, and 32.54 days
Soil Degradation
The soil degradation for target compounds was investigated under
set conditions, and should follow first-order kinetic equation. The
appropriate HPLC analytical conditions were confirmed through
comparing HPLC analyses of blank soil, test soil and standard
samples. In the process of extraction solvent selection, methanol,
acetonitrile, acetone, tetrahydrofuran (THF), dichloromethane (DCM)
and mixed solutions, like acetone / dichloromethane, acetone /
tetrahydrofuran, and acetone / tetrahydrofuran / dichloromethane
8 | J. Name., 2012, 00, 1‐3
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Table 3 Kinetic parameters for the soil degradation
DOI: 10.1039/C5RA25765D
Comp
ounds
First‐order
kinetic equation
Correlation
Half‐life
R
coefficient /R2 t1/2/days
I‐7
I‐1
CN
NO2
Br
Ct = 4.698e‐0.0213t
Ct = 4.445e‐0.0322t
Ct = 3.842e‐0.0354t
Ct = 3.845e‐0.0361t
Ct = 4.542e‐0.0376t
Ct = 3.911e‐0.0391t
Ct = 3.824e‐0.0469t
Ct = 3.914e‐0.0566t
Ct = 4.284e‐0.0621t
Ct = 4.392e‐0.0737t
Ct = 4.466e‐0.0878t
Ct = 3.982e‐0.725t
0.9978
0.9958
0.9983
0.9982
0.9998
0.9944
0.9989
0.9979
0.9978
0.9973
0.9975
0.9945
32.54
21.53
19.58
19.20
18.43
17.73
14.78
12.25
11.16
9.40
I‐5
I‐4
Cl
I‐3
F
I‐8
CF3
I
I‐6
I‐2
H
I‐10
I‐12
I‐11
I‐9
CH3
i‐C3H7
C2H5
N(CH3)2
7.89
0.96
Note: Compound I‐2 represent Chlorsulfuron.
100
90
80
70
60
50
40
30
20
10
0
35
30
25
20
15
10
5
32.54
21.53
19.58
19.2
18.43
17.73
14.78
12.25 11.16
9.4
7.89
0.96
0
I‐7
I‐1
I‐5
I‐4
I‐3
I‐8
Structure
I‐6
I‐2
I‐10
I‐12
I‐11
I‐9
Brassica campestris (foliage spray, 30 g/ha)
Amaranthus tricolor (foliage spray, 30 g/ha)
Echinochloa crusgalli (foliage spray, 30 g/ha)
Digitaria sanguinalis (foliage spray, 30 g/ha)
half‐life/days
Brassica campestris (soil treatment, 30 g/ha)
Amaranthus tricolor (soil treatment, 30 g/ha)
Echinochloa crusgalli (soil treatment, 30 g/ha)
Digitaria sanguinalis (soil treatment, 30 g/ha)
Figure 5 The relationship of structures, herbicidal activity and half‐life
respectively. Surprisingly, the half-life of compound I-9 was less
In summary, a structural derivation of Chlorsulfuron was designed
than one day. Furthermore, the degradation rates among the target and synthesized by introducing various groups (alkyl, nitro, halogen,
compounds introduced halo groups at 5th position had no significant cyano etc) onto the 5th position of its benzene ring. Identities of the
difference. For instance, the degradation half-life data of compounds target compounds were confirmed by IR, UV, 1H and 13C NMR, MS,
I-6, I-3, I-4, and I-5 were 14.78, 18.43, 19.2, and 19.58 days EA and X-ray diffraction. Bioassay results indicated that most of
respectively. From the above experimental results, it was confirmed synthesized sulfonylureas showed superior herbicidal activities when
that the introduction of different substitutes at 5th position do compared with Chlorsulfuron. After their soil degradation behaviors
influence the soil degradation rates of target compounds, which were investigated, an insight of structure / bioassay / soil degradation
could provide valuable information to explore potential controllable tri-factor relationship was firstly established and summarized in Fig.
degradation of other herbicides.
5. As observed from the figure, the introduction of various
substituents at 5th position of the benzene ring can remain or vary the
herbicidal activities, such as nitro, halo, methyl, and dimethylamino
etc, on the other hand, can influence the soil degradation rates where
Conclusions
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electron-donating groups are favorable, especially dimethylamino 20. C. Görl, N. Beck, K. Kleiber and H. G. Alt, J. Mol. Catal. A –
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DOI: 10.1039/C5RA25765D
group. These results will provide a valuable clue to further explore
Chem., 2012, 352, 110.
the potential controllable degradation of SU and other herbicides to 21. Z. Q. Yu, Y. W. Lv, C. M. Yu and W. K. Su, Tetrahedron Lett.,
seek ecologically safer and environmentally benign herbicides. It 2013, 54, 1261.
will also provide us a new strategy to decrease the relevant impact 22. P. H. Fries and D. Imbert, J. Chem. Eng. Data, 2010, 55, 2048.
on our environment and ecology during future herbicides research 23. C. X. Zhao, J. W. Malecha, S. A. Noble, S. G. Duron, A. K.
program.
Lindstrom and A. K. Shiau, US patent, 0234046, 2005.
24. L. Shi, L. P. Zhou, G. K. Dai, N. Y. Wang, D. L. An and Q. Y.
Cai, Talanta, 2013, 115, 386.
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This work was supported by the National National Science
Foundation of China (No. 21272129), Collaborative Innovation
Center of Chemical Science and Engineering (Tianjin), and
Syngenta Doctorate Scholarship.
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10 | J. Name., 2012, 00, 1‐3
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DOI: 10.1039/C5RA25765D
Graphic for table of contents
Through studying structure, bioassay and soil degradation tri-factor relationship, potential
controllable degradation of SU was firstly explored and summarized.