Synthesis and Herbicidal Activities of Sodium Methyl(α-(Substituted Phenoxyacetoxy)Alkyl)Phosphinates

Article abstract of DOI:10.1080/10426507.2014.974092

A series of sodium methyl(α-(substituted phenoxyacetoxy)alkyl)phosphinates was designed and synthesized. Their structures were confirmed by IR, ¹H NMR and elemental analysis, and some of them were further confirmed by MS. The results of bioassay showed that most of title compounds exhibited moderate to good herbicidal activities against the root of barnyard grass and rape at 10～100 mg/L.

Full text of DOI:10.1080/10426507.2014.974092

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Phosphorus, Sulfur, and Silicon and the Related
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Synthesis and Herbicidal Activities of Sodium Methyl(α-
(Substituted PhenoxyAcetoxy)Alkyl)phosphinates
Tao Wangab, Yujiao Gaoa, Hao Penga & Hongwu Hea
a The Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of
Chemistry, Central China Normal University, Wuhan, Hubei, P. R. China
b College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang,
Jiangxi, P. R. China
Accepted author version posted online: 30 Oct 2014.
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To cite this article: Tao Wang, Yujiao Gao, Hao Peng & Hongwu He (2014): Synthesis and Herbicidal Activities of Sodium
Methyl(α-(Substituted PhenoxyAcetoxy)Alkyl)phosphinates, Phosphorus, Sulfur, and Silicon and the Related Elements, DOI:
10.1080/10426507.2014.974092
To link to this article: http://dx.doi.org/10.1080/10426507.2014.974092
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SYNTHESIS AND HERBICIDAL ACTIVITIES OF SODIUM METHYL(α-
(SUBSTITUTED PHENOXYACETOXY)ALKYL)PHOSPHINATES
Tao Wanga,b, Yujiao Gaoa, Hao Penga, and Hongwu Hea,*
aThe Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of
Chemistry, Central China Normal University, Wuhan, Hubei, P. R. China
bCollege of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang,
Jiangxi, P. R. China
Address correspondence to Hao Peng or Hongwu He, College of Chemistry, Central China
Normal University, 152 Luoyu Road, Wuhan, 430079, P. R. China. E-mail:
penghao@mail.ccnu.edu.cn or he1208@mail.ccnu.edu.cn

This work was supported by the National Key Technologies R & D Program of China
(No. 2011BAE06B03).
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Abstract: A series of sodium methyl(α-(substituted phenoxyacetoxy)alkyl)phosphinates was
designed and synthesized. Their structures were confirmed by IR, 1H NMR and elemental
analysis, and some of them were further confirmed by MS. The results of bioassay showed that
most of title compounds exhibited moderate to good herbicidal activities against the root of
barnyard grass and rape at 10~100 mg/L.
O
O
P
Yn
H3C
H3C
Yn
P
O
NaI
O
H3CO
O
NaO
O
acetone,N2
R
O
R
O
Supplemental materials are available for this article. Go to the publisher’s online edition of
Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file
Keywords Synthesis; phosphinate; herbicidal activity
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INTRODUCTION
The pyruvate dehydrogenase complex (PDHc) is of interest from the point of view of
agrochemical design, because it catalyses a key transformation in carbohydrate metabolism, the
oxidative decarboxylation of pyruvate to acetyl coenzyme A.1,2 Detailed studies of
acylphosphinates and acylphosphonates reveal that these analogues of pyruvic acid could be
designed as mechanism-based inhibitors of PDHc, however, they are not active enough to fully
develop into herbicides.1,2 In our previous work, a series of α-(substituted
phenoxyacetoxy)alkylphosphonic acid ester and their salts, as potent PDHc inhibitors, was
designed and synthesized, and the ensuing bioassay results showed notable herbicidal activities.3-
6 Structure-activity relationship analyses indicate that the phosphonate salts show higher
inhibitory activity against PDHc than the corresponding phosphonic acid ester, because the salts
are more analogous to the pyruvic acid which acts as the substrate of PDHc.4-6
As a part of our ongoing work, a series of α-(substituted phenoxyacetoxy)alkylphosphinic
acid ester7,8 and their monosodium salts was designed, in which the chloro, methyl or
trifluoromethyl groups were kept as Yn on the phenoxy on the basis of SAR results of our
previous research.7,8 Herein, ten title compounds were synthesized and their herbicidal activities
were evaluated. The results of bioassay show that all of title compounds exhibited moderate to
good herbicidal activities against the tested plants, which is in good agreement with the
prediction.
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RESULTS AND DISCUSSION
Syntheses
The multistep procedure for the synthesis of the title compound 7 is outlined in Scheme 1.
The dichloro(methyl)phosphine 1 was synthesized by the reaction of phosphorus trichloride with
methyl iodide in the presence of aluminum chloride.7,8 O-Methyl methylphosphinate 2 could be
prepared from the dichloro(methyl)phosphine 1 by reaction with methanol under anhydrous
condition. The nucleophilic addition of O-methyl methylphosphinate 2 with aldehydes in the
presence of a catalytic amount of Et3N gave O-methyl 1-hydroxyalkyl(methyl)phosphinate 3 in
satisfactory yields. The method for the synthesis of substituted phenoxyacetyl chloride 5 were
adopted, according to the previous work reported in our group.6-8 -(Substituted
phenoxyacetoxy)alkylphosphinates 6 can be obtained by the condensation of compounds 3 with
different substituted phenoxyacetyl chlorides 5. The phosphinates 6 reacted with oven-dried
sodium iodide in dry acetone to provide sodium methyl(-(substituted
phenoxyacetoxy)alkyl)phosphinates 7. The structures of 7a-7j were confirmed by comprehensive
IR, 1H NMR, elemental analysis, and some of them were further identified via mass spectrum
(MS).
Herbicidal Activity
Compounds 7a-7j were tested for herbicidal activity on barnyard grass (Echinochloa
crusgalli) and rape (Brassica napus) at 100 and 10 mg/L by Petri dishes method. All of the
compounds showed moderate to good herbicidal activity against the root of barnyard grass and
rape. Especially, compounds 7a, 7b, 7e, 7g, 7i, and 7j showed >90% inhibitory activity against
the growth of root of rape and barnyard grass. Compounds 7a, 7b, 7g, 7i, and 7j displayed >90%
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inhibitory activity against the growth of stem of rape. And all compounds displayed higher
inhibitory activity against the growth of the root than that of the stem, while compounds 7e
showed weak stimulating activity to the stem of barnyard grass.
The groups R and Yn had significant influence on the inhibitory activity of monosodium salt
of alkylphosphinates 7. When R groups were kept constant, compounds with 2,4-Cl2 as Yn, had
better inhibitory activity against the growth of rape and barnyard grass except against the growth
of stem of barnyard grass. When 2,4-Cl2 as Yn were kept constant, compounds with Ph or 2-ClPh
as R (7b or 7c) showed higher inhibitory activity against the growth of stem of barnyard grass
than compounds with 2,4-Cl2Ph or pyrid-2-yl as R (7f or 7i). When 3-CF3 as Yn was kept
constant, compounds with Ph as R (7a) showed higher inhibitory activity against the growth of
rape and barnyard grass than compounds with 2-ClPh as R (7d).
Experimental details and the table of activities (Table S 1) are presented in the
Supplemental Materials.
CONCLUSION
In conclusion, a series of sodium methyl(α-(substituted phenoxyacetoxy)alkyl)phosphinates
was synthesized via the key intermediate O-methyl methyl(α-(substituted
phenoxyacetoxy)alkyl)phosphinates with satisfactory yields. The test for herbicidal activity
indicated that most of the title compounds possessed good herbicidal activity against the tested
plants. As for the active compounds, they displayed higher inhibitory activity against the growth
of the root than that of the stem.
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EXPERIMENTAL
Column chromatography was carried out with Merck silica gel (230-400 mesh). Thin-layer
chromatography (TLC) was performed on silica gel GF-254. Melting points (m.p.) were
measured on a WRS-IB electrothermal melting-point apparatus and uncorrected. Infrared spectra
were recorded in potassium bromide pellets with a Nicolet Avatar 360 Fourier transform infrared
(FTIR) spectrophotometer. 1H NMR was recorded on a Varian XL-400 spectrometer using
tetramethylsilane (TMS) as internal standard and DMSO-d6 as solvent. MS were performed on a
Finnigen TRACE spectrometer and API2000LC/MS. Elemental analysis were analyzed on a
Vario EL III CHNSO elemental analyzer.
Synthesis
The synthesis of dichloro(methyl)phosphine 1
Phosphorus trichloride (1 mol) and anhydrous aluminium chloride (1.14 mol) were added in
the flask. The mixture was heated for 30 min at 60~70 oC, cooled in an ice bath, and
methyliodide (1 mol) was added dropwise over 0.5 h with continous stirring. After 1 h the
complex solidifies and further stirring was impossible. Then a mixture of dry potassium chloride
(1.4 mol) and iron powder (60 g) were added to the solid complex. The reflux condenser was
exchanged for a distillation condenser. The mixture was distilled to give 150 g of the fraction
collected at 78~165 oC. Then the mixture was fractionated three times to give the pure
dichloro(methyl)phosphine 1 as a colourless liquid in 60% yields.
The synthesis of O-methyl (1-hydroxyalkyl)methylphosphinates 3
O-Methyl methylphosphinate 2 (0.02 mol) and an appropriate aldehyde (0.024 mol) were
stirred at room temperature for 10 min. To this mixture cooled in an ice-water bath was slowly
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added triethylamine (0.01 mol) as a catalyst. The mixture was stirred for 4~6 h at room
temperature. The components with lower boiling point was evaporated in vacuo to give the crude
compound 3. Purification by column chromatography on silica gel and elution with petroleum
ether/acetone (4/1, v/v) gave the corresponding pure 3.
General procedure for the synthesis of sodium methyl(-(substituted
phenoxyacetoxy)alkyl)phosphinates 7a-7j
A solution of O-methyl methyl(α-(substituted phenoxyacetoxy)alkyl)phosphinates (0.02
mol) and oven-dried sodium iodide (0.02 mol) in dry acetone (molecular sieve 4 Å, 40 mL) was
refluxed with stirring under nitrogen for 4~6 h. The solution was evaporated under reduced
pressure. The residual solid was recrystallized from methanol to afford the pure product as white
solid or crystals in 63~82% yields.
Sodium methyl(phenyl(2-(3-(trifluoromethyl)phenoxy)acetoxy)methyl)phosphinate
(7a)
White soild; yeild 72%; mp 163~165 oC;1H NMR (DMSO-d6): δ 0.81 (d, 3H, CH3, J=14.8
Hz), 5.09 (s, 2H, OCH2CO), 5.59 (d, 1H, OCHP, J=16.64 Hz), 7.01~7.56 (m, 9H, C6H5, C6H4);
IR (KBr, υ/cm-1): 3125 (Ph-H), 2925, 1742 (C=O), 1592, 1492, 1445, 1198 (P=O), 1070 (C-O-
C), 1046 (P-O-C), 927, 735; Calcd. For C17H15F3NaO5P: C, 49.77, H, 3.69; Found: C, 49.73, H,
3.58.
Sodium ((2-(2,4-dichlorophenoxy)acetoxy)(phenyl)methyl)(methyl)phosphinate (7b)
White soild; yeild 78%; mp 162~164 oC;1H NMR (DMSO-d6): δ 0.80 (d, 3H, CH3, J=15.0
Hz), 4.88~5.09 (m, 2H, OCH2CO, J=6.3 Hz), 5.60 (d, 1H, OCHP, J=18.0 Hz), 7.02~7.54 (m,
8H, C6H5, C6H3); IR (KBr, υ/cm-1): 3092 (Ph-H), 2948, 1770 (C=O), 1632, 1588, 1483, 1224
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(P=O), 1102 (C-O-C), 1046 (P-O-C), 931, 766; Calcd. For C16H14Cl2NaO5P: C, 46.74, H, 3.43;
Found: C, 46.47, H, 3.28.
Sodium ((2-chlorophenyl)(2-(2,4-
dichlorophenoxy)acetoxy)methyl)(methyl)phosphinate (7c)
1
White soild; yeild 63%; mp >280 oC; H NMR (DMSO-d6): δ 0.99 (d, 3H, CH3, J=13.6
Hz), 5.04 (s, 2H, OCH2CO), 6.04 (d, 1H, OCHP, J=10.8 Hz), 7.04~7.59 (m, 7H, C6H4, C6H3); IR
(KBr, υ/cm-1): 3043 (Ph-H), 2945, 1761 (C=O), 1637, 1618, 1478, 1178 (P=O), 1059 (C-O-C),
1043 (P-O-C), 933, 752; Calcd. For C16H13Cl3NaO5P: C, 43.13, H, 2.94; Found: C, 42.73, H,
2.94.
Sodium ((2,4-dichlorophenyl)(2-(3-
(trifluoromethyl)phenoxy)acetoxy)methyl)(methyl)phosphinate (7d)
1
White soild; yeild 76%; mp >280 oC; H NMR (DMSO-d6): δ 0.82 (d, 3H, CH3, J=15.4
Hz), 5.05 (s, 2H, OCH2CO), 5.88 (d, 1H, OCHP, J=10.8 Hz), 7.05~7.58 (m, 7H, C6H3, C6H4); IR
(KBr, υ/cm-1): 3111 (Ph-H), 2931, 1757 (C=O), 1608, 1590, 1461, 1188 (P=O),1066 (C-O-C),
1041 (P-O-C), 933, 754; Calcd. For C17H13Cl2F3NaO5P: C, 42.61, H, 2.73; Found: C, 42.30, H,
2.94.
Sodium ((2-(2,4-dichlorophenoxy)acetoxy)(2,4-
dichlorophenyl)methyl)(methyl)phosphinate (7e)
White soild; yeild 82%; mp 225~227 oC;1H NMR (DMSO-d6): δ 0.96 (d, 3H, CH3, J=16.8
Hz), 5.03 (s, 2H, OCH2CO), 5.95 (d, 1H, OCHP, J=8.0 Hz), 7.03~7.58 (m, 6H, C6H3, C6H3); IR
(KBr, υ/cm-1): 3026 (Ph-H), 2943, 1765 (C=O), 1619, 1590, 1482, 1193 (P=O), 1073 (C-O-C),
1047 (P-O-C), 937, 740; Calcd. For C16H12Cl4NaO5P: C, 40.03, H, 2.52; Found: C, 40.14, H,
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2.73; LC-MS (m/z, %): 455 (M+-23, negative 100), 253 (17.52), 219 (13.86), 161 (19.16), 127
(67.93), 501 (M++23, positive 77.99), 301 (49.69), 265 (54.09), 245 (42.77), 173 (11.95), 139
(100).
Sodium ((2-(2-fluorophenoxy)acetoxy)(pyridin-2-yl)methyl)(methyl)phosphinate (7f)
White soild; yeild 68%; mp >276 oC;1H NMR (DMSO-d6): δ 0.87 (d, 3H, CH3, J=13.6 Hz),
5.03 (s, 2H, OCH2CO), 5.59 (d, 1H, OCHP, J=10.4 Hz), 6.95~8.45 (m, 8H, C5H4N, C6H4); IR
(KBr, υ/cm-1): 3132 (Ph-H), 2929, 1752 (C=O), 1594, 1505, 1433, 1199 (P=O), 1113 (C-O-C),
1062 (P-O-C), 928, 753; Calcd. For C15H14FNNaO5P: C, 49.87, H, 3.91, N, 3.88; Found: C,
49.92, H, 4.44, N, 3.48.
Sodium ((2-(4-chlorophenoxy)acetoxy)(pyridin-2-yl)methyl)(methyl)phosphinate (7g)
White soild; yeild 66%; mp 234~235 oC;1H NMR (DMSO-d6): δ 0.89 (d, 3H, CH3, J=14.0
Hz), 5.02 (s, 2H, OCH2CO), 5.61 (d, 1H, OCHP, J=10.4 Hz), 6.94~8.47 (m, 8H, C5H4N, C6H4);
IR (KBr, υ/cm-1): 3117 (Ph-H), 2928, 1754 (C=O), 1594, 1491, 1434, 1199 (P=O), 1095 (C-O-
C), 1054 (P-O-C), 927, 734; Calcd. For C15H14ClNNaO5P: C, 47.70, H, 3.74, N, 3.71; Found: C,
47.53, H, 4.21, N, 3.26.
Sodium ((2-(2-chloro-5-methylphenoxy)acetoxy)(pyridin-2-
yl)methyl)(methyl)phosphinate (7h)
White soild; yeild 70%; mp >265 oC;1H NMR (DMSO-d6): δ 0.98 (d, 3H, CH3, J=14.0 Hz),
2.22 (s, 3H, CH3Ph), 5.03 (s, 2H, OCH2CO), 5.67 (d, 1H, OCHP, J=10.8 Hz), 6.78~8.48 (m, 7H,
C5H4N, C6H3); IR (KBr, υ/cm-1): 3139 (Ph-H), 2935, 1739 (C=O), 1594, 1493, 1435, 1206
(P=O), 1061 (C-O-C), 1026 (P-O-C), 920, 745; Calcd. For C16H16ClNNaO5P: C, 49.06, H, 4.12,
N, 3.58; Found: C, 49.62, H, 4.03, N, 3.19.
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Sodium ((2-(2,4-dichlorophenoxy)acetoxy)(pyridin-2-yl)methyl)(methyl)phosphinate
(7i)
White soild; yeild 76%; mp 229~230 oC;1H NMR (DMSO-d6): δ 0.87 (d, 3H, CH3, J=13.6
Hz), 5.07 (s, 2H, OCH2CO), 5.62 (d, 1H, OCHP, J=11.2 Hz), 7.16~8.48 (m, 7H, C5H4N, C6H3);
IR (KBr, υ/cm-1): 3147 (Ph-H), 2933, 1754 (C=O), 1593, 1573, 1480, 1200 (P=O), 1080 (C-O-
C), 1057 (P-O-C), 940, 755; Calcd. For C15H13Cl2NNaO5P: C, 43.71, H, 3.18, N, 3.40; Found: C,
44.01, H, 3.32, N, 3.10; LC-MS (m/z, %): 411, 388 (M+-23, negative 100), 219 (33.50), 161
(83.50); 434 (M++23, positive 100), 411 (8.39), 267 (75.48), 192 (9.03), 175 (9.03).
Sodium ((2-(2,6-dichlorophenoxy)acetoxy)(pyridin-2-yl)methyl)(methyl)phosphinate
(7j)
White soild; yeild 64%; mp >257 oC;1H NMR (DMSO-d6): δ 0.88 (d, 3H, CH3, J=14.0 Hz), 5.10
(s, 2H, OCH2CO), 5.63 (d, 1H, OCHP, J=11.2 Hz), 7.16~8.49 (m, 7H, C5H4N, C6H3); IR (KBr,
υ/cm-1): 3121 (Ph-H), 2936, 1765 (C=O), 1618, 1595, 1482, 1193 (P=O), 1073 (C-O-C), 1048
(P-O-C), 936, 762; Calcd. For C15H13Cl2NNaO5P: C, 43.71, H, 3.18, N, 3.40; Found: C, 43.51,
H, 3.26, N, 3.00.
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2. Baillie, A. C.; Wright, K.; Wright, B. J.; Earnshaw, C. G. Pestic. Biochem. Phys. 1988, 30,
103-112.
3. Peng, H.; Wang, T.; Xie, P.; Chen, T.; He, H. W.; Wan, J. J. Agric. Food Chem. 2007, 55,
1871-1880.
4. Gao, L.; Deng, X. Y.; Tan, X. S.; Long, Q. W.; Peng, H.; He, H. W. Phosphorus, Sulfur
Silicon Relat. Elem. 2013, 188, 989-994.
5. Long, Q. W.; Deng, X. Y.; Gao, Y. J.; Xie, H. Y.; Peng, H.; He, H. W. Phosphorus, Sulfur
Silicon Relat. Elem. 2013, 188, 819-825.
6. Peng, H.; Long, Q. W.; Deng, X. Y.; He, H. W. Phosphorus, Sulfur Silicon Relat. Elem.
2013, 188, 1868-1874.
7. Li, M. Q.; You, G. Y.; Peng, H.; He, H. W. J. Pestic. Sci. 2013, 38, 78-84.
8. Deng, X. Y.; Liao, G. H.; Long, Q. W.; Gao, Y. J.; Peng, H.; He, H. W. Phosphorus, Sulfur
Silicon Relat. Elem. 2013, 188, 663-671.
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[CH3PCl3]+[AlCl3I]-
PCl3
CH3I
AlCl3
CH3PCl2
1
O
O
P
Et3N
RCHO
Et3N
H
H3C
H3CO
2
H3C
2CH3OH
CH3PCl2
P
H
R
C
H3CO
DCM
OH
1
3
O
OH
Cl
OH
Yn
Yn
HO
SOCl2
or
Cl
O
Yn
O
O
3 + 5
O
O
O
5
4
Br
O
O
H3C
Yn
Et3N
P
O
H3CO
O
R
O
6
O
P
O
H3C
H3CO
Yn
H3C
Yn
NaI
acetone,N2
P
O
O
NaO
O
R
O
R
O
6
7a-7j
7a
7b
7c
7d
: R=Ph, Yn=3-CF3; : R=Ph, Yn=2,4-Cl2; : R=2-ClPh, Yn=2,4-Cl2; : R=2,4-Cl2Ph, Yn=3-CF3;
7e: R=2,4-Cl2Ph, Yn=2,4-Cl2; 7f: R=pyrid-2-yl, Yn=2-F; 7g: R=pyrid-2-yl, Yn=4-Cl; 7h: R=pyrid-2-yl,
7i
7j
Yn=2-Cl,5-CH3; : R=pyrid-2-yl, Yn=2,4-Cl2; : R=pyrid-2-yl, Yn=2,6-Cl2
Scheme 1 Synthetic route of compounds 7a-7j
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