Herbicidal activity and application cyclic of phosphonates

Article abstract of DOI:10.1080/10426507.2018.1540490

Among alkylphosphonates Io,O,O-dimethyl 1-(2,4-dichlorophenoxyacetoxy) ethylphosphonate (clacyfos) was found to be an effective inhibitor against dicotyledons PHDc and exhibited excellent herbicidal activity in our previous work. According to our study on the alkylphosphonates Io, both R¹ and R² groups in the structural unit of phosphorus-containing played a very important role in herbicidal activity. Therefore, a series of 2-[1-(substituted phenoxycarboxy)alkyl]-5,5-dimethyl-1,3,2-dioxaphosphinane-2-one containing fluorine II was obtained by the modification of alkylphosphonates Io. The bioassay results showed that cyclic phosphonate II-6 with CH₃ as R_, 2-Cl,4-F as Y_n exhibited promising herbicidal activity. Its herbicidal activity, weed-controlling spectrum, selectivity between crops and weeds were further evaluated in greenhouse and field.

Full text of DOI:10.1080/10426507.2018.1540490

Phosphorus, Sulfur, and Silicon and the Related Elements
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Herbicidal activity and application cyclic of
phosphonates
H. W. He, W. Wang, H. Peng & X. S. Tan
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PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
https://doi.org/10.1080/10426507.2018.1540490
Herbicidal activity and application cyclic of phosphonates
H. W. He, W. Wang, H. Peng, and X. S. Tan
Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, Wuhan,
P. R. China
ABSTRACT
ARTICLE HISTORY
Received 29 September 2018
Accepted 12 October 2018
Among alkylphosphonates Io, O,O-dimethyl 1-(2,4-dichlorophenoxyacetoxy) ethylphosphonate (cla-
cyfos) was found to be an effective inhibitor against dicotyledons PHDc and exhibited excellent
herbicidal activity in our previous work. According to our study on the alkylphosphonates Io, both
R1 and R2 groups in the structural unit of phosphorus-containing played a very important role in
herbicidal activity. Therefore, a series of 2-[1-(substituted phenoxycarboxy)alkyl]-5,5-dimethyl-1,3,2-
dioxaphosphinane-2-one containing fluorine II was obtained by the modification of alkylphospho-
nates Io. The bioassay results showed that cyclic phosphonate II-6 with CH3 as R, 2-Cl,4-F as Yn
exhibited promising herbicidal activity. Its herbicidal activity, weed-controlling spectrum, selectivity
between crops and weeds were further evaluated in greenhouse and field.
KEYWORDS
Cyclic alkylphosphonate;
herbicidal activity; fluorine
GRAPHICAL ABSTRACT
1. Introduction
structure.[6,7] Considering the possible contribution of cyclo-
phosphonate to herbicidal activity an open-chain O,O-dia-
lkyl phosphonate unit in the structure of Io was further
modified by introducing a six-membered cyclic phosphonate
unit. Series of 2-[1-(substituted phenoxyacetoxy)alkyl]-5,5-
dimethyl-1,3,2-dioxaphosphinane-2-one II were designed
and synthesized (Scheme 1). Their herbicidal activity was
tested, and active compound was further evaluated in green-
house and field.
Organic phosphorus compounds display a wide range of
biological activities and have attracted considerable attention
in the field of pesticides.[1] A detailed study of acylphosphi-
nates and acylphosphonates revealed that these analogs of
pyruvate could be designed as mechanism-based inhibitors
of pyruvate dehydrogenase complex (PDHc).[2] However,
they are not active enough for full development as herbi-
cides.[2,3] On the basis of acetylphosphonate as a hit com-
pound, several series of 1-substituted alkylphosphonates Io,
were designed and synthesized. Among alkylphosphonates 2. Results and discussion
Io,
O,O-dimethyl
1-(2,4-dichlorophenoxyacetoxy)ethyl-
2.1. Syntheses
phosphonate (clacyfos) was found to be an effective inhibi-
tor against dicotyledons PHDc and exhibited excellent
herbicidal activity in our previous work.[4] Clacyfos can be
as herbicide against broad-leaved weeds, grass weeds, and
sedges by post-emergence application.[5] These results
encouraged us to make further modifications on the basis of
Cyclic phosphonate II could be conveniently synthesized by
the condensation of 2-(1-hydroxyalkyl)-5,5-dimethyl-1,3,2-
dioxaphosphinane-2-one M2 with an appropriate substituted
phenoxyacetyl chloride M4 in the presence of a base
(Scheme 2). The addition of 1,3,2-dioxaphosphinane M1 to
the structure Io. According to our study on alkylphospho- various aldehydes gave corresponding cyclic 1-hydroxyalkyl-
nates Io, both R1 and R2 groups in the structural unit of phosphonates M2. Considering the unique properties of
phosphorus-containing played a very important role in her- fluorine, the 2-Cl,4-F, 2-F,4-Cl, 2-F, 4-F or 3-CF3 group as
bicidal activity. It was noticed that a variety of studies had Yn was introduced into substituted phenoxyacetic acid
demonstrated that bioactivity and stability of phosphonates respectively. A series of cyclic phosphonates II containing
or phosphates could be increased by introducing a phos- fluorine including II 1-18 has been synthesized by this way
phorus-containing heterocyclic moiety to their parent (Table 1).[8]
CONTACT H. W. He
he1208@mail.ccnu.edu.cn
Key Laboratory of Pesticide & Chemical Biology Ministry of Education College of Chemistry, Central China
Normal University, Wuhan, 430079, P. R. China.
ß 2018 Taylor & Francis Group, LLC

2
H. W. HE ET AL.
Scheme 1. Design of cyclic phosphonates.
Scheme 2. Synthesis of cyclic phosphonates II.
Table 1. Structure of cyclic phosphonates containing fluorine II.
2.2. Herbicidal activity
Compd.
R
Yn
Compd.
R
Yn
All of these cyclic phosphonates II containing fluorine
exhibited moderate to good herbicidal activities by a prelim-
inary test.[6] The results showed fluorine or trifluoromethyl
group as Yn on benzene ring had a very important effect on
herbicidal activity. A satisfactory herbicidal activity required
a reasonable combination both type and position of Yn.
Compound II-6 with CH3 as R, 2-Cl,4-F as Yn was found to
have best herbicidal activity among those compounds II 1-
18. The post-emergence herbicidal activity and weed-con-
trolling spectrum of II-6 were further examined.
As shown in Table 2, II-6 displayed significant inhibition
against common amaranth, goosefoot, leaf mustard, and
morning glory at 37.5 and 18.75 g ai/ha, respectively. It
exhibited better herbicidal activity against tested broad-
leaved weeds than that of 2,4-D and glyphosate even at
18.5 g ai/ha. II-6 showed broad-spectrum activity to control
II-1
II-2
II-3
II-4
II-5
II-6
II-7
II-8
II-9
CH3
CH3
CH3
CH3
CH3
CH3
Ph
H
II-10
II-11
II-12
II-13
II-14
II-15
II-16
II-17
II-18
Ph
Ph
Ph
3-CF3
2-F, 4-Cl
2-Cl, 4-F
H
2-F
4-F
3-CF3
2-F, 4-Cl
2-Cl, 4-F
2-F
4-F
3-CF3
2-F,4-Cl
2-Cl,4-F
H
2-Furyl
2-Furyl
2-Furyl
2-Furyl
2-Furyl
2-Furyl
Ph
Ph
2-F
4-F
at Shandong in China. A formulation of 10% EC was used
in the field testing. 10% II-6 EC was tested in the maize
field against primary broad-leaved weeds at 300-600 g ai/ha
in Shandong when weeds were at 3 to 5 leaves stage and
maize was at 4 to 6 leaves stage. 57% 2,4-D butyl ester EC
was used at a recommended rate 513 g ai/ha as a positive
control. The results showed that 10% II-6 EC exhibited 90-
100% inhibitory activity against white eclipta (Eclipta pros-
trate), Asian copperleaf (Acalypha australis), chingma abuti-
lon (Abutilon theophrasti), goosefoot (Chenopodium album),
bunge’s smartweed (Polygonum bungeanum), Sibirian cockle-
bur (Xanthium strumarium) and black nightshade (Solanum
nigrum) at 300–360 g ai/ha in maize field (Table 3). No evi-
dent injury of maize was observed in all treatments even at
600 g ai/ha by II-6 during experimental period.
broad-leaved
weeds
included
common
amaranth
(Amaranthus retroflexus), goosefoot (Chenopodium album),
leaf mustard (Brassica juncea), morning glory (Ipomoea nil),
monarch redstem (Ammannia baccifera), pickerel weed
(Monochoria vaginalis), ball cabbage (Brassica oleracea), wild
vetch (Vicia gigantea), chili (Capsicum annuum), curled
dock (Rumex crispus), chingma abutilon (Abutilon theo-
phrasti), alligatorweed (Alternanthera philoxeroides), field
chickweed (Cerastium arvense), white eclipta (Eclipta pros-
trata) at 150 g ai/ha. Crop selectivity and safety evaluation
of II-6 were carried out by post-emergence spray treatment.
The results showed II-6 could result in injury to dicotyle-
donous crops, such as green vegetable, tomato, radish, chili,
cotton, rape, and soybean even at 75 g ai/ha. However
wheat, maize, and rice exhibited higher tolerance to II-6
even at 150–600 g ai/ha.
3. Conclusions
Cyclic phosphonates containing fluorine II 1-18 were
designed and prepared based on the modification of open-
chain 1-substituted alkylphosphonates Io. Their herbicidal
activity was further evaluated in greenhouse and field. Cyclic
phosphonate II-6 (R ¼ Me, Yn ¼ 2-Cl,4-F) was found to be
In order to evaluate the efficacy of II-6 against weeds in most active compound with good selectivity between dicoty-
field condition, the field trial was conducted in maize field ledonous weeds and monocotyledonous crops. II-6 exhibited

PHOSPHORUS, SULFUR, AND SILICON AND THE RELATED ELEMENTS
3
Table 2. The post-emergence herbicidal activity of II-6.
3.2. Crop selectivity
Compd.
Rate (g ai/ha)
Amrb
Cheb
Brjb
Ipnb
Conventional rice, corn, cotton, soybean, rape, and wheat
were respectively planted in plots (diameter ¼12 cm) con-
taining test soil and grown in a greenhouse at 20–25 ꢀC.
After the plants had reached the four-leaf stage, the spraying
treatment was conducted at different dosages by diluting the
formulation of the selected compounds. The visual injury
and growth state of the individual plant were observed at
regular intervals. The final evaluation for crops safety of the
selected compounds was conducted by visual observation in
30 days after treatment on the 0–100 scale (0 ¼ no injury,
10 ¼ chlorosis, 100 ¼ death).
II-6
37.5
18.75
37.5
18.75
37.5
18.75
37.5
95
90
90
70
60
60
100
90
75
70
80
75
70
50
80
70
100
95
100
80
75
70
100
100
90
90
100
90
60
50
100
100
2,4-D
Glyphosate
Clacyfos
18.75
aInhibitory potency (%) against the growth of plants in the greenhouse, 0 (no
effect), 100% (completely kill).
bAmr: common amaranth; Che: goosefoot; Brj: leaf mustard; Ipn: morning glory.
Table 3. Post-emergence herbicidal activity of 10% II-6 EC in maize field.
Inhibitory potency % (45 DAT)
Rate g ai/ha
Eclc Acac Abuc Chec Polc Xanc Solc
300
360
450
600
92 100
96 100
98 100
100 100
95 100
95
97
100
100
96
96
95
90
95
90
95
98
98
97
Funding
100 100
100 100 100
100 100 100
The work was supported in part by the National Research
and Development Plan (2017YFD0200506), the National
Natural Science Foundation of China (21877047), 111
Project B17019.
57% 2,4-D butyl ester EC 513
96
98
98
aInhibitory potency (%) was measured as percentage change in each weed
fresh weight compared to that of the untreated control; values are the aver-
age of 4 replicates. DAT is day after treatment.
bApplication method: Spray one time by a Jacto PJ-16 or Matabi sprayer.
cEcl: white eclipta, Aca: Asian copperleaf, Abu: chingma abutilon, Che: goose-
foot, Pob: bunge’s smartweed, Xan: Siberian cocklebur, Sol:
black nightshade.
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