Selenium analogs of phenoxypropionic and phenoxyacetic herbicides

Article abstract of DOI:10.1515/znb-2018-0128

Selenium analogs of phenoxyacetic herbicides, namely 2-(2,4-dichlorophenoxy)propionic acid (2,4-DP), 2-(2,4-dichlorophenoxy)acetic acid (2,4-D), 2-(4-chloro-2-methylphenoxy)propionic acid (MCPP), 2-(4-chloro-2-methylphenoxy)acetic acid (MCPA), 2-(2,4,5-trichlorophenoxy)propionic acid (2,4,5-TP), and 2-(2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), were synthesized in two steps. Iodo aryl derivatives were dimerized with elemental selenium in the presence of CuO as catalyst to the corresponding diselenides. Diselenides were reduced with NaBH₄ to a selenide anion and condensed with either propionic or chloroacetic acid to achieve the selenium analogs of phenoxyacetic herbicides. These selenium analogs show moderate herbicidal and fungistatic activity.

Full text of DOI:10.1515/znb-2018-0128

Z. Naturforsch. 2018; aop
JSerezylZeaknrzieuwsmki*,aBonguamliołagHusraso, AfnnpahKieełcnzeowxskya apnrdoMapriiaoKrnawicczyak nd
phenoxyacetic herbicides
https://doi.org/10.1515/znb-2018-0128
excess of selenium in a living organism may cause numer-
ous diseases [1, 7]. The hyperaccumulation of selenium in
plants can cause selenosis in animals [8].
This explains why the role of selenium in agriculture
seems controversial [9].
Received June 10, 2018; accepted October 22, 2018
Abstract: Selenium analogs of phenoxyacetic herbi-
cides, namely 2-(2,4-dichlorophenoxy)propionic acid
(2,4-DP), 2-(2,4-dichlorophenoxy)acetic acid (2,4-D),
2-(4-chloro-2-methylphenoxy)propionic acid (MCPP),
The beneficial effects of selenium have encouraged
researchers to synthesize a multitude of organoselenium
derivatives [10–14], such as isoselenocyanates, selenou-
reas, and selenazoles [4]. Some synthetic organoselenium
compounds show anti-hypertensive, antiviral, antibacte-
rial, antifungal [11], and insecticidal [15] effects. The orga-
noselenium compounds to be chosen for these purposes
are often designed to be analogs of biologically active
other chalcogen atom-containing compounds (e.g. replac-
ing sulfur-containing amino acids with selenium [16]).
Herewepresentthesynthesisandpesticidalproperties
of the selenium analogs of the parent phenoxypropionic
and phenoxyacetic herbicides, namely 2-(2,4-dichloro-
2-(4-chloro-2-methylphenoxy)acetic
acid
(MCPA),
2-(2,4,5-trichlorophenoxy)propionic acid (2,4,5-TP), and
2-(2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), were syn-
thesized in two steps. Iodo aryl derivatives were dimerized
with elemental selenium in the presence of CuO as cata-
lyst to the corresponding diselenides. Diselenides were
reduced with NaBH4 to a selenide anion and condensed
with either propionic or chloroacetic acid to achieve the
selenium analogs of phenoxyacetic herbicides. These
selenium analogs show moderate herbicidal and fungi-
static activity.
Keywords: fungistatic activity; herbicidal activity; phe- phenoxy)propionic acid (2,4-DP), 2-(2,4-dichlorophe-
noxyacetic herbicides; phenoxypropionic herbicides; noxy)acetic acid (2,4-D), 2-(4-chloro-2-methylphenoxy)
selenium analogs.
propionic acid (MCPP), 2-(4-chloro-2-methylphenoxy)
acetic acid (MCPA), 2-(2,4,5-trichlorophenoxy)propionic
acid (2,4,5-TP), and 2-(2,4,5-trichlorophenoxy)acetic
acid (2,4,5-T), containing the selenium atom instead of
a bridged oxygen atom. The proposed selenium analogs
are unknown, with the exception of 4a (synthesized and
evaluated earlier [17, 18]). In order to provide a complete
picture of the activity of chalcogene derivatives of the
parent herbicides, also the sulfur analogs were synthe-
sized and evaluated (known and tested earlier, as well.
See Refs. [19–23]).
1 Introduction
Selenium is an important trace element in living organ-
isms and plays a significant role in their biology [1, 2].
Selenium is present in selenocysteine (a glutathione
peroxidase enzyme), which participates in the oxygen
metabolism process and is responsible for an organism’s
self-defense mechanism against the oxidative stress [3–6].
The biological activity of seleno amino acids has been dis-
cussed [6].
Recent experimental and epidemiological data 2 Results and discussion
suggest that many selenium-containing compounds
exhibit anticancer activity, mainly by inducing self- Selenium analogs of 2,4-DP, 2,4-D, MCPP, MCPA, and
destruction (apoptosis) of cancer cells and limiting meta- 2,4,5-TP were synthesized from 2,4-dichloroiodobenzene,
stases [4]. However, it is necessary to underline that an 2-methyl-4-chloroiodobenzene, and 2,4,5-trichloroiodo-
benzene, respectively, in two steps involving the syn-
thesis of diselenides from the above-listed iodoarenes,
*Corresponding author: Jerzy Zakrzewski, Institute of Industrial
followed by the reaction of the diselenides with 2-chlo-
Organic Chemistry, Annopol 6, 03-236 Warsaw, Poland,
ropropionic (3a) or chloroacetic (3b) acid in the presence
of sodium borohydride (compare with the recently pub-
lished literature [24]).
e-mail: zakrzewski@ipo.waw.pl
Bogumiła Huras, Anna Kiełczewska and Maria Krawczyk: Institute of
Industrial Organic Chemistry, Annopol 6, 03-236 Warsaw, Poland
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ꢀJ. Zakrzewski et al.: Selenium analogs of phenoxypropionic and phenoxyacetic herbicides
2ꢀ
As the first step, the diselenides 2a–c were syn-
The nature of the detected components 4f1 and 4f2
thesized (Scheme 1). Selenization of the corresponding is strongly supported by 1H, 13C, and 77Se NMR spectra. All
iodoarenes 1a–c with selenium in the presence of CuO the spectra are a superposition of all the expected signals
as catalyst gave the expected diselenides 2a–c [25]. Com- of the mixture of both 2-(2,4,5-trichlorophenylselanyl)
pound 2a had been synthesized earlier [17].
acetic acid (4f1) and 2-(4,5-dichlorophenylselanyl)acetic
1H and 13C NMR spectra of 2c show a strong peak acid (4f2).
belonging to DMSO (a solvent used in diselenide 2 synthe-
The singlets belonging to CH2, COOH, and the Se
sis). The NMR spectra as well as the wide range of melting nucleus are doubled in the corresponding NMR spectra.
1
points suggest that 2c is an inclusion compound with two
The proton signals in H NMR belonging to protons
molecules of DMSO (estimated on the basis of the integra- in the aryl rings in 4f1 and 4f2 are the superposition of
tion of the appropriate 1H NMR signal).
two distinct singlets (4f1) and the pattern of a d,d,dd
In the second step, the selenium analogs of 2,4-DP, multiplet, which is very characteristic for the protons in
2,4-D, MCPP, MCPA and 2,4,5-TP, 2-(arylselanyl)propionic the positions 2, 3, and 6 (4f2).
(4a, c, e), and 2-(arylselanyl)acetic acids (4b, d) were syn-
A combination of 12 carbon signals, which are the
thesized from the diselenides 2a–c and 2-chloropropionic superposition of 6 signals of 4f1 and 6 signals of 4f2, can
(3a) or chloroacetic (3b) acid using NaBH4 as the reducing be elegantly interpreted: 5 signals belong to CH carbon
agent (Schemes 2 and 3).
atoms and 7 belong to the carbon atoms, which is con-
Structures of the selenium compounds 2a–c and firmed by the presence of 5 signals in DEPT 135° spectrum.
The identification of the signals probably attributed
4a–e were confirmed by mass spectrometry (MS), high-
1
13
77
resolution MS (HRMS), H NMR, C NMR, Se NMR, and to the 4,5-dichloro-substituted aromatic ring may be
IR spectroscopy (see experimental section and Supporting explained by the formation of a benzyne intermediate
Information 1).
Attempts to synthesize the selenium analog of 2,4,5-T
(elimination of o-Cl,I) during the synthesis of 2c.
All the signals discussed above are listed in the
from 2c and chloroacetic acid (3b) led to an approxi- experimental section and presented in Supporting
mately equimolar, nonseparable mixture of the expected Information I.
(2,4,5-trichlorophenylselanyl)acetic acid (4f1) and a
It is worth noting that, as in the case of 4f,
second compound, likely the dechlorinated derivative 4f2 2-(2,4,5-trichlorophenylselanyl)propionic acid (4e) is
(Scheme 3).
also contaminated with an analogous impurity with two
R2
I
Cl
R1
R1
1a, 2a R1 = Cl, R2 = H
Se, CuO
Se
,
R1 = CH3, R2 = H
1b 2b
Se
17–94%
1c, 2c R1 = Cl, R2 = Cl
R2
R1
1a–1c
Cl
2a–2c
Cl
R2
Scheme 1:ꢁSynthesis of diselenides 2a–c.
R3
R3
R2
O
Se
O
Cl
R1 = Cl R2 = H R3 = CH3
4b R1 = Cl R2 = H R3 = H
R1
Cl
4a
R1
OH
R2
3a b
,
Se
OH
R1 = CH3 R2 = H R3 = CH3
R1 = CH3 R2 = H R3 = H
Se
4c
4d
NaBH4
R1
3a
3b
Cl
R3 = CH3
Cl
2a–c
4e R1 = Cl R2 = Cl R3 = CH3
R3 = H
23–71%
R2
4a–e
Scheme 2:ꢁ2-(Arylselanyl)propionic (4a, c, e) and 2-(arylselanyl)acetic acids (4b, d) from diselenides 2a–c.
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ꢀ3
J. Zakrzewski et al.: Selenium analogs of phenoxypropionic and phenoxyacetic herbicidesꢀ
Cl
Cl
O
O
Se
O
Se
Cl
Cl
Cl
Cl
3b
Cl
OH
OH
Cl
OH
Se
+
Se
NaBH4
Cl
Cl
Cl
2c
4f1
Cl 4f2
Scheme 3:ꢁ(2,4,5-Trichlorophenylselanyl)acetic acid (4f1) and (4,5-dichlorophenylselanyl)acetic acid (4f2) as the products of the
condensation of 2c with chloroacetic acid (3b).
R3
R3
O
O
SH
S
Cl
R1
R1
OH
3a b
,
OH
NaOH
R2
R2
3a R3 = CH3
Cl
Cl
6a–f
R3 = H
3b
5a–c
59–89%
1
5a R1 = Cl
5b
5c R1 = Cl
R2 = H
6a
R = Cl
R2 = H R3 = CH3
R2 = H R3 = H
6b R1 = Cl
1
R = CH3 R2 = H
6c R1 = CH3 R2 = H R3 = CH3
R2 = Cl
1
R = CH3 R2 = H R3 = H
6d
6e R1 = Cl
R2 = Cl R3 = CH3
R2 = Cl R3 = H
R1 = Cl
6f
Scheme 4:ꢁ2-Arylsulfanylpropionic (6a, c, e) and 2-(arylsulfanyl)acetic (6b, d, f) acids, the sulfur analogs of herbicides 2,4-DP, 2,4-D, MCPP,
MCPA, 2,4,5-TP, and 2,4,5-T.
chlorine atoms – likely 2-(4,5-dichlorophenylselanyl)pro-
pionic acid, albeit the content of this impurity is negligi- 4 and 6 was observed, but it was slightly lower than that
ble (see 1H NMR in Supporting Information I).
of the parent phenoxypropionic and phenoxyacetic her-
Herbicidal activity of the selenium and sulfur analogs
The sulfur analogs of the parent herbicides 2,4-DP, bicides. It is worth noting that both selenium and sulfur
2,4-D, MCPP, MCPA, 2,4,5-TP, and 2,4,5-T have been well analogs 4 and 6 do not show any pre-emergence (via soil)
known since the 1940s. In spite of this, we decided to activity, in contrast to that of the parent 2,4-DP, MCPP,
synthesize them for comparison and as a background for MCPA, 2,4,5-TP, and 2,4,5-T.
the evaluation of the biological activity of the selenium
The diselenides 2 show only weak fungistatic activ-
analogs 4. The sulfur analogs 6a–6f were synthesized ity (conc. 200 ppm). The selenium and sulfur analogs of
from 2,4-dichlorothiophenol (5a), 2-methyl-4-chloro- the parent herbicides 4 and 6 show medium fungistatic
thiophenol (5b), and 2,4,5-trichlorothiophenol (5c) activity. The selenium analog of MCPA (4d) and the sulfur
(Scheme 4).
analog of 2,4-DP (6a) show significant fungistatic activity
The structures of the sulfur analogs 6, as known com- against three phytopathogenic species of fungi. However,
pounds, were confirmed by MS and IR spectra (see the it should be stressed that all tested analogs 4 and 6 show
experimental section and Supporting Information I).
The herbicidal and fungistatic activities of the synthe-
sized selenium and sulfur analogs of the phenoxypropi-
onic and phenoxyacetic herbicides 2,4-DP, 2,4-D, MCPP,
phytotoxic properties.
MCPA, 2,4,5-TP, and 2,4,5-T (4a–4f, 6a–6f) as well as 3 Conclusion
fungistatic activity of the diselenides (2a–2c) were evalu-
ated. For the data on the herbicidal (4a–4f and 6a–6f) Selenium analogs of phenoxypropionic and phenoxy-
and fungistatic (2a–2c, 4a–4f, and 6a–6f) activities, see acetic herbicides, namely 2,4-DP, 2,4-D, MCPP, MCPA,
Supporting Information 2.
2,4,5-TP, 2,4,5-T, were synthesized for the first time.
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4ꢀ
The selenium analogs 4 and the sulfur analogs 6 show hydrogen carbonate solution was again acidified with 2N
moderate herbicidal and fungistatic activities.
HCl and extracted with ethyl acetate. The organic layers
were dried with anhydrous magnesium sulfate. The drying
agent was removed by filtration, and ethyl acetate was
evaporated under reduced pressure. A nearly colorless
residue (6.76 g) was obtained. For dehydration, the pre-
cipitate was azeotroped with benzene (4ꢀ×ꢀ30 mL). Evapo-
ration of benzene gave a colorless solid (6.22 g), which
was washed thoroughly with hexane. Yield 5.57 g (51.6%);
Rfꢀ=ꢀ0.16 (benzene/ethyl acetate 1:1), 0.68 (n-butanol/acetic
acid/water 50:1:5); m.p. 178–182°C (178–180°C [26]).
4 Experimental section
4.1 General
Chlorophenols 1 were purchased from Aldrich. Bromo-
fluoroacetic acid 2 was purchased from Fluorochem. Five
of the six parent phenoxyacetic herbicides, namely 2,4-DP,
2,4-D, MCPP, MCPA, and 2,4,5-T, used as reference mate-
rials in biological assays were acquired from the offer of
standard materials manufactured and certified at IPO.
Thin-layer chromatography (TLC) was carried out on silica
gel Merck Alurolle 5562 or Alufolien 5554 [mobile phases:
hexane/ethyl acetate (9:1); benzene/ethyl acetate (9:1);
benzene/methanol (9:1)]. TLC visualization was achieved
using UV (254 nm) light. Visualization of the selenium-
containing compounds was achieved by spraying with
1% ethanolic PdCl2 (dark brown spots on pale beige
background). Column chromatography was performed
on silica gel 0.040–0.063 mm, 230–400 mesh: Merck
1.09385.1000 or Zeochem 60 hyd. Electrospray ionization
MS (EI MS) data at 70 eV were recorded on AMD 604 and
Agilent Technologies 5975 B mass spectrometers. HR EI
MS data were recorded using an AMD 604 mass spectro-
meter. ESI MS and HR ESI MS (methanol as solvent) were
recorded by using a Micromass LCT apparatus. IR spectra
were recorded on a Jasco 420 FT IR spectrophotometer.
4.3 Diselenides 2a–2c: general procedure
(according to Ref. [25])
Iodoaryl derivative 1a–c (0.004 mol), black metallic sele-
nium (0.632 g, 0.008 mol), and nano-cupric oxide (0.064
g, 0.0008 mol) were suspended in anhydrous DMSO
(8 mL) at room temperature. The reagents were heated
to a temperature of 90°C. Then, finely ground potassium
hydroxide (0.896 g, 0.016 mol) was added portionwise. The
suspension was stirred at 90°C until the disappearance of
the starting iodide (TLC, hexane) (1.5–3.5 h). The reaction
mixture was allowed to cool to room temperature. Water
(90 mL) and ethyl acetate (50 mL) were added to the reac-
tion mixture. The resulting biphasic mixture was stirred
vigorously for 5–10 min. The layers were then separated.
The aqueous layer was further extracted with ethyl acetate
(3ꢀ×ꢀ40 mL) controlling the content of the product (TLC).
The combined organic layers were dried over magnesium
sulfate. The drying agent, the residue of copper oxide, and
selenium were filtered off. Removal of the solvent under
reduced pressure afforded the crude product. The crude
product was applied onto silica gel using ethyl acetate as
solvent. The mixture of the silica and the crude product
was applied at the top of the chromatographic column. The
product was eluted with hexane to give diselenides 2a–2c.
13
77
1H, C NMR, and Se NMR data were collected on Bruker
1
AVANCE 300 and 500 spectrometrs, at 300 MHz for H,
75 MHz for 13C, and either 57 or 95 MHz for 77Se.
4.2 2-(2,4,5-Trichlorophenoxy)propionic
acid, 2,4,5 (TP)
Sodium hydride (1.7 g, 60% paste, 0.0425 mol) was added
in portions to a solution of 2,4,5-trichlorophenol (1c, 7.9 g,
0.04 mol) and 2-chloropropionic acid (3a, 4.34 g, 0.04 mol, 4.3.1 Bis(2,4-dichlorophenyl) diselenide (2a)
3.42 mL) in anhydrous dioxane (50 mL). A second portion
of anhydrous dioxane (50 mL) was added, and the reagents Yield 0.55 g (60.8%); m.p. 89–90°C; Rfꢀ=ꢀ0.7 (hexane); syn-
were heated for 1.5 h at 100°C. The reaction mixture was thesized in Ref. [17], however, without information about
cooled to 50°C, and the second part of sodium hydride (1.7 any analytical data.
g of a 60% paste, 0.0425 mol) was added in portions. The
Cl
Cl
reaction was heated for 1.5 h at 100°C. The reaction mixture
Se
was cooled to room temperature, acidified with 2N HCl
Se
(60 mL), and extracted with ethyl acetate. The organic layer
Cl
Cl
was washed with sodium hydrogen carbonate. The sodium
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ꢀ5
J. Zakrzewski et al.: Selenium analogs of phenoxypropionic and phenoxyacetic herbicidesꢀ
Cl
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ456 (11), 455 (5), 454 (37), 453
+
(11), 452 (70), 451 (18), 450 (79) [M] , 449 (22), 448 (55),
Cl
Cl
Cl
447 (18), 446 (26), 376 (1), 374 (3), 372 (6), 370 (6), 336 (2),
334 (2), 305 (2), 303 (2), 302 (3), 300 (3), 272 (2), 270 (4),
229 (17), 227 (66), 225 (100), 223 (46), 222 (14), 221 (15),
192 (24), 190 (56), 188 (26), 187 (9), 186 (10), 155 (10),
109 (8), 75 (13), 74 (15). HRMS (EI, 70 eV): m/zꢀ=ꢀ449.7562
Se
Se
Cl
Cl
(calcd. 449.7554 for C12H6Cl480Se2). H NMR (300 MHz,
1
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ524 (19), 522 (41), 520 (58), 518
CDCl3): δꢀ=ꢀ7.51 (1 H, d, Jꢀ=ꢀ8.4 Hz, H6), 7.37 (1 H, d,
Jꢀ=ꢀ2.2 Hz, H3), 7.15 (1 H, dd, Jꢀ=ꢀ8.5 Hz, Jꢀ=ꢀ2.2 Hz, H5).
13C NMR (75 MHz, CDCl3,): δꢀ=ꢀ134.07 (CAr), 133.93 (CAr),
131.86 (CHAr), 129.16 (CHAr), 128.25 (CHAr), 127.38 (CAr).
77Se NMR (95 MHz): δꢀ=ꢀ403.70. IR (cm−1, KBr): νꢀ=ꢀ1624,
1550, 1550, 1445, 1367, 1265, 1143, 1120, 1092, 1085, 1019,
856, 812, 800.
+
(53) [M] , 516 (32), 515 (10), 514 (15), 263 (32), 261 (85), 259
(100, ArSe), 257 (45), 256 (12), 255 (14), 226 (46), 224 (69),
222 (32). HRMS (EI, 70 eV): m/zꢀ=ꢀ517.6735 (calcd. 517.6775
for C12H4Cl680Se2) H NMR (300 MHz, CDCl3): δꢀ=ꢀ7.66 (2 H,
1
13
s,), 7.47 (2 H, s), 2.62 (14 H, s, DMSO). C NMR (75 MHz,
CDCl3): δꢀ=ꢀ132.65, 132.63, 132.13, 130.51, 128.89, 128.59,
40.99 (DMSO). 77Se NMR (95 MHz): δꢀ=ꢀ419.14. IR (cm−1,
KBr): νꢀ=ꢀ3434, 1630, 1453, 1425, 1380, 1319, 1104, 1049,
873, 614.
4.3.2 Bis(4-chloro-2-methylphenyl) diselenide (2b)
Yield 0.77 g (94.4%); a semisolid oil at ambient tempera- 4.4 2-(Arylselanyl)propionic (4a, c, e) or
ture, Rfꢀ=ꢀ0.6 (hexane).
2-(arylselanyl)acetic (4b, d, f) acids, a
general procedure
Cl
A solution of sodium borohydride (0.0668 g, 0.00176 mol)
Se
Se
in anhydrous ethanol (approx. 3 mL) was added dropwise
under strict argon atmosphere at 0°C to a solution of dis-
Cl
elenide 2a–c (0.0008 mol) in anhydrous ethanol (5 mL).
The yellowish starting solution became a colorless milky
+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ412 (12), 410 (19) [M] , 408 (15),
suspension, which was stirred for about 15 min at 0°C (the
406 (8), 334 (17), 333 (10), 332 (65), 331 (17), 330 (100), 329
yellow color may reappear). A second portion of sodium
(16), 328 (48), 327 (15), 326 (16), 207 (13), 206 (33), 205
borohydride (0.0334 g, 0.00088 mol) in anhydrous ethanol
(37), 204 (69), 203 (36), 202 (38), 201 (25), 200 (17), 199
(approx. 2 mL) was added dropwise to the mixture at 0°C.
(9), 180 (10), 179 (17), 178 (11), 169 (18), 167 (10), 165 (12),
A solution of sodium hydroxide (0.032 g, 0.0008 mol)
127 (34), 125 (98), 99 (15), 93 (26), 91 (20), 90 (17), 89 (69),
in water (approx. 0.5 mL) was added to 2-chloropropi-
63 (33). HRMS (EI, 70 eV): m/zꢀ=ꢀ409.8639 (calcd. 409.8646
onic acid (3a) or chloroacetic acid (3b) (0.0016 mol). The
for C14H12Cl280Se2). H NMR (300 MHz, CDCl3): δꢀ=ꢀ7.21–7.24
1
resulting solution of the sodium salt of the chloroacid
(2 H, m, 2ꢀ×ꢀH3), 7.10 (1 H, d, Jꢀ=ꢀ8.4 Hz, 2ꢀ×ꢀH6), 7.03 (2 H,
3 was slowly added dropwise to the reaction mixture
ddd, Jꢀ=ꢀ8.4 Hz, Jꢀ=ꢀ2.4 Hz, Jꢀ=ꢀ0.6 Hz, 2ꢀ×ꢀH5), 2.34 (6 H, s,
under strict argon atmosphere at 0°C. Gas evolution was
13
2ꢀ×ꢀCH3). C NMR (75 MHz, CDCl3,): δꢀ=ꢀ141.56 (CAr), 134.27
observed. The reagents were allowed to come to room
(CHar), 133.69 (CAr), 130.23 (CHar), 129.18 (CAr), 126.95
temperature in 1 h and then stirred at room temperature
(CHar), 22.11 (Ar-CH3). 77Se NMR (57 MHz): δꢀ=ꢀ332.08. IR
for 24 h. Air was introduced into the reaction mixture and
(cm−1, film): νꢀ=ꢀ1580, 1461, 1445, 1379, 1200, 1101, 1027,
the reactants were stirred at r.t. for 30 min. The reaction
1015, 869, 809.
mixture remained colorless. The suspension was evapo-
rated to dryness under vacuum on a rotary evaporator. To
the residue was added water (35 mL) and the first portion
of diethyl ether (35 mL). The ether layer was separated
and inspected by TLC. If the presence of the starting
4.3.3 Bis(2,4,5-trichlorophenyl) diselenide (2c)
Yield 0.18 g (17.4%); m.p. 130–139°C; Rfꢀ=ꢀ0.6 (hexane); an diselenides 2a–c was detected, they were recovered by
inclusion compound with DMSO (see the text).
column chromatography. The aqueous layer (pH 11) was
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6ꢀ
O
acidified with concentrated hydrochloric acid (approx.
2 mL) to pH 2. The acidified aqueous layer was extracted
with the second portion of diethyl ether (3ꢀ×ꢀ30 mL). In
order to completely remove the unreacted starting 2-chlo-
ropropionic acid (3a), the second combined ether layers
were washed thoroughly with water (3ꢀ×ꢀ30 mL) to pH 4
and then dried over magnesium sulfate. Removal of the
drying agent and evaporation of ether afforded the crude
product 4, which was purified by column chromatography
(hexane, hexane/ethyl acetate 9:1, hexane/ethyl acetate
4:1). Compounds 4a–f were obtained as colorless, greasy
solids, which were thoroughly washed on a porous funnel
with hexane, water, and again with hexane. The solids
were compressed on the funnel and thoroughly dried
under reduced pressure to give 4a–f.
Se
Cl
Cl
OH
+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ286 (60), 284 (91) [M] , 282 (43),
281 (12), 280 (14), 241 (19), 239 (30), 237 (14), 229 (17), 227
(66), 225 (100), 223 (47), 222 (14), 221 (16), 192 (27), 190
(62), 188 (30), 187 (10), 186 (11), 164 (32), 162 (49), 161
(32), 159 (48), 122 (19), 109 (12), 93 (17), 75 (20), 74 (23).
HRMS (EI, 70 eV,): m/zꢀ=ꢀ283.8896 (calcd. 283.8910 for
C8H6O2Cl280Se). H NMR (300 MHz, CDCl3,): δꢀ=ꢀ10.61 (1 H,
1
bs), 7.51 (1 H, d, Jꢀ=ꢀ8.4 Hz, H6), 7.41 (1 H, d, Jꢀ=ꢀ2.1 Hz, H3),
7.19 (1 H, dd, Jꢀ=ꢀ8.6 Hz, Jꢀ=ꢀ2.1 Hz, H5), 3.57 (2 H, s, CH2). 13C
NMR (75 MHz, CDCl3): δꢀ=ꢀ176.23 (C=O), 136.34 (CAr), 134.13
(CAr), 133.31 (CHAr), 129.49 (CHAr), 127.96 (CAr), 127.88 (CHAr),
4.4.1 2-(2,4-Dichlorophenylselanyl)propionic acid (4a)
25.82 (CH2). Se NMR (95 MHz): δꢀ=ꢀ325.13. IR (cm−1, KBr):
77
νꢀ=ꢀ3434, 1699 (1697 [17]), 1453, 1430, 1380, 1302, 1173, 1099,
Yield 0.20 g (41.8%); m.p. 89–92°C; Rfꢀ=ꢀ0.8 (n-BuOH/
CH3COOH/H2O 50:1:5).
1025, 865, 798, 656.
O
Se
4.4.3 2-(4-Chloro-2-methylphenylselanyl)propionic
acid (4c)
Cl
OH
Yield 0.22 g (48.8%); m.p. 91–93°C; Rfꢀ=ꢀ0.75 (n-BuOH/
CH3COOH/H2O 50:1:5).
Cl
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ302 (17), 300 (66), 298 (100)
O
Se
+
[M] , 296 (46), 295 (13), 294 (15), 255 (29), 253 (45), 251
OH
(21), 229 (16), 228 (29), 227 (61), 226 (46), 225 (92), 224
(28), 223 (46), 222 (18), 221 (14), 192 (29), 190 (64), 188
(32), 187 (11), 186 (11), 175 (18), 173 (28), 155 (15), 153 (10),
149 (10), 148 (24), 146 (37), 109 (11), 75 (16), 74 (17), 73
Cl
(10), 45 (14). HRMS (EI, 70 eV): m/zꢀ=ꢀ297.9053 (calcd.
297.9067 for C9H8O2Cl280Se). H NMR (300 MHz, CDCl3): MS (EI, 70 eV): m/z (%)ꢀ=ꢀ280 (24), 278 (54) [M] , 276 (26),
δꢀ=ꢀ11.39 (1 H, bs, COOH), 7.60 (1 H, d, Jꢀ=ꢀ8.4 Hz, H6), 7.44 275 (9), 274 (9), 233 (6), 207 (17), 206 (15), 205 (39), 204 (13),
(1 H, d, Jꢀ=ꢀ2.4 Hz, H3), 7.18 (1 H, dd, Jꢀ=ꢀ8.4 Hz, Jꢀ=ꢀ2.1 Hz, 203 (23), 202 (9), 201 (9), 169 (12), 167 (6), 153 (15), 142 (9),
H5), 3.89 (1 H, q, Jꢀ=ꢀ7.2 Hz CH(CH3)), 1.59 (3 H, d, Jꢀ=ꢀ7.2 Hz, 127 (34), 126 (22), 125 (100), 93 (26), 91 (22), 90 (10), 89 (36),
CH(CH3)). 13C NMR (75 MHz, CDCl3,): δꢀ=ꢀ179.66 (C=O), 63 (15), 45 (8). HRMS (EI, 70 eV): m/zꢀ=ꢀ277.9608 (calcd.
1
+
138.52 (CAr), 136.48 (CHAr), 135.08 (CAr), 129.52 (CHAr), 127.66 277.9613 for C10H11O2Cl80Se). H NMR (300 MHz, CDCl3):
1
77
(CHAr), 127.18 (CAr), 36.62 (CH(CH3)), 16.78 (CH3). Se NMR δꢀ=ꢀ7.55 (1 H, d, Jꢀ=ꢀ8.4 Hz, H6), 7.25 (1 H, dd, Jꢀ=ꢀ2.4 Hz,
(95 MHz): δꢀ=ꢀ432.56. IR (cm−1, KBr): νꢀ=ꢀ3438, 1698, 1452, Jꢀ=ꢀ0.6 Hz, H3), 7.09 (1 H, ddd, Jꢀ=ꢀ8.25 Hz, Jꢀ=ꢀ2.4 Hz,
1240, 1098, 1024, 859, 800.
Jꢀ=ꢀ0.6 Hz, H5), 3.90 (1 H, q, Jꢀ=ꢀ7.2 Hz CH(CH3)), 2.46 (1 H, s,
Ar-CH3), 1.60 (3 H, d, Jꢀ=ꢀ6.9 Hz, CH(CH3)). 13C NMR (75 MHz,
CDCl3): δꢀ=ꢀ179.83 (COOH), 143.75 (CAr), 137.77 (CHAr), 135.05
(CAr), 130.01 (CHAr), 126.99 (CAr), 126.70 (CHAr), 36.74 (CH-
CH3), 22.93 (Ar-CH3), 17.15 (CH-CH3). 77Se NMR (57 MHz):
4.4.2 2-(2,4-Dichlorophenylselanyl)acetic acid (4b)
Yield 0.11 g (23.1%); m.p. 114–117°C (119°C [17]); Rfꢀ=ꢀ0.8 δꢀ=ꢀ401.07. IR (cm−1, KBr): νꢀ=ꢀ3433, 2928, 1696, 1229, 1100,
(n-BuOH/CH3COOH/H2O 50:1:5).
869, 810.
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J. Zakrzewski et al.: Selenium analogs of phenoxypropionic and phenoxyacetic herbicidesꢀ ꢀ7
4.4.4 2-(4-Chloro-2-methylphenylselanyl)acetic
acid (4d)
(52), 154 (15), 153 (11), 152 (9), 151 (9), 146 (14), 145 (7), 144
(8), 143 (7), 136 (13), 117 (8), 109 (25), 108 (18), 107 (16),
97 (8), 84 (6), 74 (22), 73 (19), 55 (11), 45 (25). HRMS (EI,
Yield 0.23 g (53.4%); m.p. 108–110°C; Rfꢀ=ꢀ0.75 (n-BuOH/ 70 eV): m/zꢀ=ꢀ331.8665 (calcd. 331.8677 for C9H7Cl3O280Se2).
CH3COOH/H2O 50:1:5).
1H NMR (300 MHz, CDCl3): δꢀ=ꢀ11.54 (1 H, bs, COOH), 7.76 (1
H, s, Har), 7.51 (1 H, s, Har), 3.92 (1 H, q, Jꢀ=ꢀ7.2 Hz, CH-CH3),
O
Se
13
1.62 (3 H, d, Jꢀ=ꢀ7.2 Hz, CH-CH3). C NMR (75 MHz, CDCl3):
OH
δꢀ=ꢀ179.32 (COOH), 136.21 (CAr), 135.92 (CHAr), 133.15 (CAr),
131.45 (CAr), 130.63 (CHAr), 128.60 (CAr), 36.87 (CH-CH3), 16.76
(CH-CH3). 77Se NMR (95 MHz): δꢀ=ꢀ441.12. IR (cm−1, KBr):
νꢀ=ꢀ3433, 3100, 2979, 2930, 2650, 2550, 1691, 1570, 1456,
1432, 1420, 1320, 1296, 1112, 1052, 926, 871, 618.
Cl
+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ266 (23), 264 (53) [M] , 262 (25),
261 (8), 260 (9), 207 (8), 206 (7), 205 (19), 204 (14), 203 (14),
202 (9), 201 (7), 169 (9), 167 (5), 142 (11), 141 (6), 139 (14), 127 4.4.6 2-(2,4,5-Trichlorophenylselanyl)acetic
(33), 125 (100), 93 (20), 91 (13), 89 (28), 77 (6), 75 (4), 73 (4),
acidꢀ+ꢀ2-(4,5-dichlorophenylselanyl)acetic acid
(4f1ꢀ+ꢀ4f2)
63 (14). HRMS (EI, 70 eV): m/zꢀ=ꢀ263.9460 (calcd. 263.9456
1
for C9H9O2Cl80Se). H NMR (300 MHz, CDCl3): δꢀ=ꢀ7.51 (1 H,
d, Jꢀ=ꢀ8.4 Hz, H6), 7.21 (1 H, dd, Jꢀ=ꢀ2.1 Hz, Jꢀ=ꢀ0.6 Hz, H3), Yield 0.17 g (33.6%); m.p. 104–107°C; Rfꢀ=ꢀ0.75 (n-BuOH/
7.11 (1 H, ddd, Jꢀ=ꢀ8.25 Hz, Jꢀ=ꢀ2.4 Hz, Jꢀ=ꢀ0.6 Hz, H5), 3.46 (2 CH3COOH/H2O 50:1:5).
H, s, CH2), 2.43 (3 H, s, Ar-CH3). 13C NMR (75 MHz, CDCl3,):
O
O
Se
Se
δꢀ=ꢀ177.08 (COOH), 142.08 (CAr), 134.98 (CHAr), 134.28 (CAr),
OH
130.06 (CHAr), 127.90 (CAr), 126.95 (CHAr), 26.45 (CH2), 22.39
Cl
OH
Cl
(Ar-CH3). 77Se NMR (57 MHz): δꢀ=ꢀ288.02. IR (cm−1, KBr):
νꢀ=ꢀ2980, 2921, 2850, 1699, 1464, 1435, 1380, 1306, 1169,
1102, 1034, 909, 868, 806, 659.
Cl
Cl
+
Cl
1H NMR (300 MHz, CDCl3): δꢀ=ꢀ7.65 (1 H, s, 4f1), 7.53 (1 H,
d, Jꢀ=ꢀ2.4 Hz, 4f2), 7.48 (1 H, s, 4f1), 7.29 (1 H, d, Jꢀ=ꢀ8.4 Hz,
4f2), 7.15 (1 H, dd, Jꢀ=ꢀ9 Hz, Jꢀ=ꢀ2.4 Hz, 4f2), 3.61 (2 H, s), 3.62
(2 H, s). 13C NMR (75 MHz, CDCl3): δꢀ=ꢀ176.53, 176.35, 134.06
4.4.5 2-(2,4,5-Trichlorophenylselanyl)propionic
acid (4e)
Yield 0.38 g (71.4%); m.p. 107–110°C; Rfꢀ=ꢀ0.8 (n-BuOH/ (C), 133.32 (C), 133.23 (C), 132.87 (CH), 132.15 (C), 131.83 (C),
CH3COOH/H2O 50:1:5).
131.48 (C), 131.14 (CH), 130.57 (CH), 130.35 (CH), 129.47 (C),
128.34 (CH), 26.07, 25.82. 77Se NMR (95 MHz): δꢀ=ꢀ332.88,
332.76.
O
Se
Cl
OH
Cl
4.5 2-Arylsulfanylpropionic (6a, c, e) and
2-arylsulfanylacetic (6b, d, f) acids:
general procedure
Cl
+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ336 (33), 334 (84), 332 (100) [M] , An appropriate thiophenol 5 (0.0025 mol) and 20%
330 (45), 329 (12), 328 (14), 300 (12), 298 (18), 296 (9), 291 aqueous sodium hydroxide solution (1 mL for liquid
(18), 289 (48), 287 (56), 285 (25), 284 (7), 283 (8), 264 (17), thiophenols: 2,4-dichlorothiophenol (5a) and 4-chloro-
263 (30), 262 (44), 261 (75), 260 (54), 259 (89, ArSe), 258 2-methylthiophenol (5b), or 2–3 mL for solid thiophe-
(32), 257 (45), 256 (18), 255 (20), 253 (16), 252 (14), 251 (10), nol: 2,4,5-trichlorothiophenol (5c)) were placed in a
250 (10), 228 (19), 227 (18), 226 (63), 225 (30), 224 (89), flask. A solution of a sodium salt of 2-chloropropionic
223 (21), 222 (43), 221 (15), 220 (14), 211 (8), 209 (24), 208 acid (3a) or chloroacetic acid (3b) was prepared sepa-
(10), 207 (29), 206 (9), 205 (9), 192 (9), 191 (10), 190 (21), rately. Compound 3a or 3b (0.0025 mol) was added to
189 (19), 188 (14), 187 (11), 186 (9), 184 (17), 182 (50), 180 the 20% aqueous sodium hydroxide solution (1 mL).
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ꢀJ. Zakrzewski et al.: Selenium analogs of phenoxypropionic and phenoxyacetic herbicides
8ꢀ
The resulting solution of the sodium salt of the acid was (12), 97 (5), 75 (13), 74 (13), 73 (8), 69 (12), 63 (10). IR (cm−1,
added to a solution of sodium thiophenolate. A solu- KBr): νꢀ=ꢀ3434, 1708, 1456, 1431, 1311, 1201, 1105, 1033, 898,
tion (in the case of liquid thiophenols) or a suspension 868, 809, 664, 567.
(for a solid 2,4,5-trichlorothiophenol) was heated to
Tꢀ=ꢀ125–130°C with magnetic stirring for 5 h. The reaction
mixture was allowed to cool to room temperature and 4.5.3 2-(4-Chloro-2-methylphenylsulfanyl)propionic
transferred with water (15–20 mL) to a beaker. The solu-
tion (pHꢀ=ꢀ11) was acidified with concentrated hydrochlo-
acid (6c)
ric acid to pHꢀ=ꢀ2 (1–2 mL depending on the amount of Yield 0.35 g (61.4%); m.p. 70–72°C (68–69°C [19]); Rfꢀ=ꢀ0.25
sodium hydroxide used). The resulting suspension was (benzene/methanol 9:1, elongated spot).
extracted with methylene chloride (3ꢀ×ꢀ15 mL). The methyl-
ene chloride layers were dried over anhydrous magnesium
O
S
sulfate. Removal of drying agent and evaporation of the
OH
methylene chloride under reduced pressure afforded the
crude product (approx. 0.5 g), which was crystallized from
benzene (1.5–2 mL) to give pure thiophenoxy acids.
Cl
4.5.1 2-(2,4-Dichlorophenylsulfanyl)propionic acid (6a)
+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ232 (32), 230 (84) [M] , 187 (37),
185 (100), 159 (19), 157 (53), 150 (21), 125 (16), 121 (24), 89
Yield 0.56 g (88.8%); m.p. 100–102°C (101–102°C [19]);
Rfꢀ=ꢀ0.25 (benzene/methanol 9:1, elongated spot).
(15), 77 (20), 69 (7), 63 (11), 59 (15), 45 (54). IR (cm−1, KBr):
νꢀ=ꢀ3449, 3000–2500, 1708, 1581, 1466, 1450, 1420, 1330,
1294, 1234, 1200, 1096, 1052, 874, 812, 666.
O
S
OH
Cl
4.5.4 2-(4-Chloro-2-methylphenylsulfanyl)acetic
acid (6d)
Cl
Yield 0.31 g (59.4%); m.p. 126–127°C (126–127°C [22]);
Rfꢀ=ꢀ0.25 (benzene/methanol 9:1, elongated spot).
+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ254 (8), 252 (38), 250 (55) [M] ,
207 (69), 205 (100), 179 (34), 177 (50), 170 (11), 144 (20),
142 (51), 135 (6), 134 (6), 133 (7), 107 (14), 75 (6), 74 (7), 73
(6), 69 (11), 63 (11), 59 (20), 45 (15). IR (cm−1, KBr): νꢀ=ꢀ3434,
1699, 1456, 1412, 1299, 1193, 1106, 1033, 910, 855, 809, 657,
569, 550.
O
S
OH
Cl
4.5.2 2-(2,4-Dichlorophenylsulfanyl)acetic acid (6b)
+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ218 (38), 216 (100) [M] , 198 (6),
173 (25), 171 (68), 159 (13), 157 (38), 136 (7), 135 (9), 134 (6),
127 (14), 125 (34), 121 (21), 112 (4), 99 (5), 91 (10), 89 (18), 77
(15), 63 (14), 45 (48). IR (cm−1, KBr): νꢀ=ꢀ3451, 3200–2500,
1707, 1465, 1431, 1390, 1315, 1210, 1193, 1108, 1054, 911, 871,
805, 668.
Yield 0.46 g (83.5%); m.p. 120–122°C (122–123°C [20, 21]);
Rfꢀ=ꢀ0.6 (n-BuOH/CH3COOH/H2O 50:1:5).
O
S
Cl
OH
4.5.5 2-(2,4,5-Trichlorophenylsulfanyl)propionic
acid (6e)
Cl
+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ240 (10), 238 (49), 236 (70) [M] ,
193 (68), 191 (100), 179 (10), 177 (14), 159 (8), 156 (11), 155 Yield 0.56 g (78.7%); m.p. 113.5–115°C (114.5–115.5°C [19]);
(11), 149 (8), 144 (15), 142 (40), 121 (6), 111 (9), 109 (12), 107 Rfꢀ=ꢀ0.25 (benzene/methanol 9:1, elongated spot).
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ꢂꢁꢁꢁ
ꢀ9
J. Zakrzewski et al.: Selenium analogs of phenoxypropionic and phenoxyacetic herbicidesꢀ
Acknowledgment: This work was supported by the
Polish Ministry of Science and Higher Education,
4180/E-142/S/2018.
O
S
Cl
OH
Cl
Conflict of interest: The authors declare no competing
financial interest.
Cl
+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ288 (19), 286 (54), 284 (54) [M] ,
+
243 (36), 241 (99), 239 (100) [M – COOH] , 215 (13), 213 (36),
References
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4.5.6 2-(2,4,5-Trichlorophenylsulfanyl)acetic acid (6f)
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+
MS (EI, 70 eV): m/z (%)ꢀ=ꢀ274 (25), 272 (71), 270 (72) [M] ,
+
229 (34), 227 (98), 225 (100) [M – COOH] , 213 (10), 211 (10),
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(4), 106 (7), 105 (6), 97 (10), 74 (11), 69 (8), 62 (5), 61 (5), 45
(44). IR (cm−1, KBr): νꢀ=ꢀ3450, 3000–2500, 1719, 1450, 1433,
1320, 1310, 1284, 1203, 1122, 1059, 895, 970, 662.
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4.6 Bioassay procedures
See Supporting Information II available online.
5 Supporting Information
Supporting Information I (spectra of the synthesized [26] E. Grabowska, J. Arct, Z. Eckstein, Rocz. Chem. 1969,
43, 715.
compounds) and Supporting Information II (herbicidal
and fungistatic activity data and bioassay procedures)
are given as supplementary material available online
(DOI: 10.1515/znb-2018-0128).
Supplementary Material: The online version of this article offers
supplementary material (https://doi.org/10.1515/znb-2018-0128).
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Z. Naturforsch.ꢀ
ꢀ2018 | Volume x | Issue x(b)
Graphical synopsis
Jerzy Zakrzewski, Bogumiła Huras,
Anna Kiełczewska and Maria Krawczyk
Selenium analogs of phenoxypropionic
and phenoxyacetic herbicides
https://doi.org/10.1515/znb-2018-0128
Z. Naturforsch. 2018; x(x)b: xxx–xxx
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