Bis-(alkoxy)tetrathiotricarboxylates and use as herbicides thereof

Bis-(alkoxy)tetrathiotricarboxylates are disclosed as well as herbicidal compositions containing such compounds and the use of such compounds as post-emergence herbicides.

BACKGROUND OF THE INVENTION 
The present invention is directed to bis-(alkoxy)tetrathiotricarboxylates 
as well as herbicidal compositions containing these compounds and the use 
of these compounds as post-emergence herbicides. 
It has been predicted that the reaction of potassium ethylxanthate and 
phosgene would produce bis(ethoxy)tetrathiotricarboxylate. It is reported 
in Willcox, (1906) J. Amer. Chem. Soc. 28:1031-1034, however, that the 
expected product was not obtained, the reaction being "complex" in nature. 
Zhuravlev and Galchenko, (1947) Zhurnal Prikladnoi Khimii, pp. 1038-1043 
report that the reaction produces xanthogenic thioanhydride, potassium 
chloride, and carbonyl sulfide. There appears to be a suggestion in the 
paper that the tetrathiotricarboxylate is an unstable intermediate in the 
reaction. There is no evidence reported, however, indicating that the 
tetrathiotricarboxylate was formed. 
The preparation of dialkyltricarbonates and corresponding dialkyl 
dithioltricarbonates is known in the art. For examples, Friederang and 
Tarbell, (1968) Tetrahedron Letters 55:5535-5536, discloses the synthesis 
of di-t-butyl dithioltricarbonate from the reaction of sodium t-butyl 
thiolcarbonate and phosgene. Dean and Tarbell, Chemical Communications 
1969:728-729, discloses the preparation of di-t-butyl tricarbonate as well 
as di-isopropyl dithioltricarbonate and di-isopropyl tricarbonate. The 
isopropyl compounds, however, could not be obtained in pure form because 
they decomposed to their corresponding dicarbonates. 
The reaction products of dialkyl tricarbonates and dialkyl 
dithiotricarbonates with alcohols, mercaptans, primary amines and 
secondary amines have also been reported. The reaction of the di-ty-butyl 
compounds with alcohols and mercaptans yields mixed dicarbonates, reaction 
with primary amines yields isocyanates via a carbonic carbamic anhydride 
intermediate, and reaction with secondary amines yields carbamic 
anhydrides. See Dean and Tarbell, (1971) J. Org. Chem. 36:1180-1183. 
DETAILED DESCRIPTION OF THE INVENTION 
Applicants' invention relates to post-emergence herbicides of the class of 
compounds bis-(alkoxy)tetrathiotricarboxylates represented by the 
structure 
##STR1## 
wherein R and R', which can be the same or different, are selected from 
alkyl groups having from 1 to 8 carbon atoms, and alkenyl groups having 
from 2 to 8 carbon atoms, and cycloalkyl groups having 3 to 8 carbon 
atoms. Other embodiments of the present invention include herbicidal 
compositions comprising the above bis-(alkoxy)tetrathiotricarboxylates, 
and methods of controlling plants which comprises contacting plants with 
the above bix-(alkoxy)tetrathiotricarboxylates. 
Preferably, R and R' are selected from alkyl groups, having 1 to 6 carbon 
atoms, alkenyl groups and alkoxyalkyl groups having 2 to 6 carbon atoms, 
and cycloalkyl groups having 3 to 6 carbon atoms. Most preferably, R and 
R' are selected from alkyl groups, having 1 to 4 carbon atoms, alkenyl 
groups and alkoxyalkyl groups with 2 to 4 carbon atoms, and cycloalkyl 
groups with 3 to 4 carbon atoms. 
Where R and R' are selected from alkyl groups, these groups can include, 
but are not limited to, branched and straight chained alkyl radicals, such 
as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, 
amyl, isoamyl, 2-methylbutyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, 
n-hexyl, isohexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 
1,1-dimethylbutyl, 2,2-dimethylbutyl, 3,3-dimethylbutyl, 
1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,3-dimethylbutyl, heptyl, 
1-methylhexyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl, 5-methylhexyl, 
1,1-dimethylpentyl, 2,2-dimethylpentyl, 3,3-dimethylpentyl, 
4,4-dimethylpentyl, 1,3-dimethylpentyl, 1,4-dimethylpentyl, 
2,3-dimethylpentyl, 2,4-dimethylpentyl, 3,4-dimethylpentyl, 
1,2,3,-trimethylbutyl, 1,2,2-trimethylbutyl, 1,3,3-trimethylbutyl, 
2,3,3-trimethylbutyl, 2,2,3-trimethylbutyl, octyl, 1-methylheptyl, 
2-methylheptyl, 3-methylheptyl, 4-methylheptyl, 5-methylheptyl, 
6-methylheptyl, 1,1-dimethylhexyl, 2,2-dimethylhexyl, 3,3-dimethylhexyl, 
4,4-dimethylhexyl, 1,2-dimethylhexyl, 1,3-dimethylhexyl, 
1,4-dimethylhexyl, 1,5-dimethylhexyl, 2,3-dimethylhexyl, 
2,4-dimethylhexyl, 2,5-dimethylhexyl, 3,4-dimethylhexyl, 
3,5-dimethylhexyl, 4,5-dimethylhexyl, 1-ethylhexyl, 2-ethylhexyl, 
3-ethylhexyl, 4-ethylhexyl, trimethylamyls, methylethylamyls, propylamyls, 
tetramethylbutyls, diethylbutyls, and methylpropylbutyls. 
Where R and R' are selected from alkenyl groups, these groups can include, 
but are not limited to, vinyl, 1-propenyl, allyl, isopropenyl, 1-butenyl, 
2-butenyl, 3-butenyl, 1-methyl-1-propenyl, 1,3-butadienyl, 1-pentenyl, 
2-pentenyl, 3-pentenyl, 4-pentenyl, 1-methyl-1-butenyl, 
3-methyl-1-butenyl, 1,4-pentadienyl, 2,3-pentadienyl, 2,4-pentadienyl, 
1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, 5-hexenyl, 
1-methyl-1-pentenyl, 1-ethyl-1-butenyl, 1-propyl-1-propenyl, 
4-methyl-1-pentenyl, 1,3-hexadienyl, 1,4-hexadienyl, 1,5-hexadienyl, 
2,3-hexadienyl, and 2,4-hexadienyl. 
Wherein R and R' are selected from the group of cycloalkyls, these groups 
can include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, 
cyclohexyl, 2-methyl-cyclohexyl, 2,6-dimethyl cyclohexyl, 3,4-dimethyl 
cyclohexyl, cycloheptyl, and cyclooctyl. 
The compounds of the present invention can be synthesized by reacting a 
substituted xanthate suspended in dry ether with phosgene at ambient 
temperature. The phosgene may be bubbled into the salt suspension or fed 
dropwise in solution with toluene. Generally, the xanthate is the sodium, 
lithium, or potassium salt of the corresponding xanthic acid. 
Furthermore, it has been found that compounds of the present invention can 
be used as post-emergence herbicides on weed species, such as cocklebur, 
valvetleaf, common lambsquarters, barnyardgrass, hemp sesbania, and large 
crabgrass in crops, such as wheat, rice, and grain sorghum, as shown in 
the data below. Of course, the weed/crop combination(s) for which a 
particular tetrathiotricarboxylate is suited will vary and should be 
determined on an individual basis for each compound.

The following examples illustrate the preparation of compounds within the 
scope of the present invention and their activity as post-emergence 
herbicides. The examples are included for illustrative purposes only and 
are not intended to limit the scope of the invention. 
EXAMPLE 1 
Preparation of Bis-(Ethoxy)Tetrathiotricarboxylate 
Ten grams (0.0625 mole) of potassium ethylxanthate was suspended at ambient 
temperature in 100 ml of ether and stirred. Then a solution of phosgene 
(2.8 g, 0.028 mole) in 35 ml of toluene was added to the xanthate 
suspension dropwise over a 10 minute period. The suspension was stirred 
for an additional 45 minutes and then filtered to remove 6.2 g of 
precipitated potassium chloride. The filtrate was stripped of solvent to 
yield 6.7 g of yellow oil as a final product. The yellow oil was insoluble 
in water but soluble in chloroform. Elemental analysis indicated that the 
oil was the desired product having an analysis as follows: 
Calc'd for C.sub.7 H.sub.10 O.sub.3 S.sub.4 : C, 31.09; H, 3.73. Found: C, 
31.16; H, 3.82. 
EXAMPLE 2 
Preparation of Bis-(n-Propoxy)Tetrathiotricarboxylate 
To 30 g (0.17 mole) of potassium n-propyl xanthate suspended in 250 ml of 
ether there was added dropwise 7.8 g of phosgene in 109 ml of toluene 
dropwise over a period of about 30 minutes. The reaction mixture, after 
the addition of phosgene was stirred 20 minutes and filtered to remove 
potassium chloride. The filtrate was stripped of solvent to yield 19.12 g 
of a yellow oil. The yellow oil was insoluble in water but soluble in 
chloroform. Elemental analysis indicated that the oil was the desired 
product having an analysis as follows: 
Calc'd for C.sub.9 H.sub.14 O.sub.3 S.sub.4 : C, 36.22; H, 4.73. Found: C, 
36.39; H, 4.80. 
EXAMPLE 3 
Preparation of Bis-(Isopropoxy)Tetrathiotricarboxylate 
To 15 g (0.56 mole) of potassium isopropylxanthate suspended in 100 ml of 
ether with stirring was added dropwise a solution of 3.9 g (0.039 mole) of 
phosgene in 57 ml of toluene over a period of 15 minutes. Stirring was 
continued for 20 minutes after the addition was completed. The suspension 
was then filtered to remove the potassium chloride (8.0 g). Then the 
filtrate was stripped of solvent to yield a yellow oil. The yellow oil was 
insoluble in water but soluble in acetone and chloroform. Elemental 
analysis demonstrated the compound was 
bis-(isopropoxy)tetrathiotricarboxylate having an analysis as follows: 
Calc'd for C.sub.9 H.sub.14 O.sub.3 S.sub.4 : C, 36.22; H, 4.73. Found: C, 
36.34; H, 4.78. 
EXAMPLE 4 
Preparation of Bis-(n-Butoxy)Tetrathiotricarboxylate 
Potassium butylxanthate (30 g) was suspended in ether and phosgene gas 
bubbled through the suspension for 1 hour while being cooled in a water 
bath. After the addition of the gas, the suspension was purged with 
nitrogen gas for 10 minutes and then filtered to remove the precipitated 
potassium chloride (12 g). The filtrate was then stripped of solvent to 
yield a yellow liquid. 
Mass spectral analysis showed the oil to have a molecular ion peak at m/e 
212 which corresponds to the structure n-BuOC(S)SC(O)Cl. Infrared 
spectroscopy showed 2 carbonyl bands, one at 5.58 and the other at 5.73. 
The peak at 5.58 corresponds to the structure above. The peak at 5.73 
corresponds to the structure [n-BuOC(S)S].sub.2 CO; i.e., 
bis-(n-butoxy)tetrathiotricarboxylate. The oil was then taken up in ether 
and an additional 10 g of potassium butylxanthate added. After 20 minutes, 
the IR band at 5.58 had disappeared and the one at 5.73 was intensified. 
The suspension was filtered to remove 5.85 g of solid and the filtrate 
stripped of solvent to yield 29.05 g of the yellow oil. The yellow oil was 
insoluble in water but soluble in acetone and chloroform. Elemental 
analysis showed the oil to be in the desired product having an analysis as 
follows: 
Calc'd for C.sub.11 H.sub.18 O.sub.3 S.sub.4 : C, 40.46; H, 5.56. Found: C, 
40.72; H, 5.61. 
The compounds prepared in the above example are summarized in Table I. 
TABLE I 
__________________________________________________________________________ 
RUN 
No. Compound Structure 
__________________________________________________________________________ 
A bis-(ethoxy)tetrathiotricarboxylate 
##STR2## 
B bis-(n-propoxy)tetrathiotricarboxylate 
##STR3## 
C bis-(isopropoxy)tetrathiotricarboxylate 
##STR4## 
D bis-(n-butoxy)tetrathiotricarboxylate 
##STR5## 
__________________________________________________________________________ 
EXAMPLE 5 
Post-Emergence Herbicidal Activity 
The post-emergence herbicidal activity of compounds in Table I was 
demonstrated by greenhouse testing in the following manner. A good grade 
of top soil is placed in aluminum pans having holes in the bottom and 
compacted to the depth of 0.95 to 1.27 cm from the top of the pan. A 
predetermined number of seeds of each of several dicotyledonous and 
monocotyledonous annual plant species and/or vegetative propagules for the 
perennial plant species were placed on the soil and pressed into the soil 
surface. The seeds and/or vegetative propagules are covered with soil and 
leveled. The pans are then placed on the sand bench in the greenhouse and 
watered from below as needed. After the plants reach the desired age (two 
to three weeks) each pan, except for the control pans, is removed 
individually to a spraying chamber and sprayed by means of an atomizer at 
the rates noted. In the spray solution is an amount of an emulsifying 
agent mixture to give a spray solution or suspension which contains about 
0.4% by weight of the emulsifier. The spray solution or suspension 
contains a sufficient amount of the candidate chemical in order to give 
application rates corresponding to those set forth in the tables. The pans 
were returned to the greenhouse and watered as before and the injury to 
the plants as compared to the control is observed at approximately two 
weeks and the results recorded. 
The post-emergence herbicidal activity index used in Tables II and III is 
as follows: 
______________________________________ 
Plant Response Index 
______________________________________ 
0-24% Inhibition 
0 
25-49% Inhibition 
1 
50-74% Inhibition 
2 
75-99% Inhibition 
3 
100% Inhibition 4 
No Data N 
______________________________________ 
The plant species utilized in these tests are identified by letter in 
accordance with the following legend: 
______________________________________ 
A -- Canada Thistle* 
K -- Barnyardgrass 
B -- Cocklebur L -- Soybean 
C -- Velvetleaf M -- Sugar Beet 
D -- Morningglory N -- Wheat 
E -- Common Lambsquarter 
O -- Rice 
F -- Pennsylvania Smartweed 
P -- Grain Sorghum 
G -- Yellow Nutsedge* 
Q -- Wild Buckwheat 
H -- Quackgrass* R -- Hemp Sesbania 
I -- Johnsongrass* S -- Proso Millet 
J -- Downy Brome T -- Large Crabgrass 
______________________________________ 
*Established from vegetative propagules 
TABLE II 
______________________________________ 
Post-Emergence Activity at 11.2 kg/h 
Plant 
Compound 
A B C D E F G H I J K 
______________________________________ 
Ex. 1 0 2 2 1 4 N 0 0 0 0 1 
Ex. 2 1 2 2 1 3 4 0 1 1 0 1 
Ex. 3 2 3 3 1 4 N 0 0 0 1 3 
Ex. 4 2 2 2 2 4 0 0 1 0 1 1 
______________________________________ 
TABLE III 
__________________________________________________________________________ 
Post-Emergence Activity at 5.6 kg/h 
Plant 
Compound 
B C D E J K L M N O P Q R S T 
__________________________________________________________________________ 
Ex. 2 2 2 1 4 0 1 2 1 0 0 0 2 2 1 1 
Ex. 3 2 4 2 4 2 2 2 3 1 0 0 2 4 2 4 
__________________________________________________________________________ 
EXAMPLE 6 
Preparation of Bis-(Methoxy)Tetrathiotricarboxylate 
In a 250 ml round bottomed flask was placed a solution of 2.25 g (0.0227 
mole) of phosgene in 60 g diethyl ether and 50 g toluene. The solution in 
the flask was cooled to 0.degree. C. in an ice bath, and 6.3 (0.0432 mole) 
of potassium methylxanthate was added to the solution dropwise over a 
five-minute period with stirring. The solution was stirred for an 
additional 25 minutes and then filtered to remove potassium chloride. The 
solvent was evaporated to yield a crude solid. The solid was dissolved in 
ethyl acetate and precipitated with benzene. The purified solid had a 
melting point of 62.5.degree.-65.0.degree. C. Infrared spectroscopy 
confirmed the structure of the desired compound. 
The post-emergence herbicidal activity of 
bis-(methoxy)tetrathiotricarboxylate was demonstrated at two different 
rates using the procedure of Example 5, except that the compound was 
formulated immediately prior to spraying. The results are shown in TABLE 
IV. 
TABLE IV 
______________________________________ 
Post-Emergent Activity of Bis-(methoxy)- 
tetrathiotricarboxylate 
Plants 
Rate (kg/h) 
A B C D E F G H I J K 
______________________________________ 
56.1 4 3 3 3 4 3 1 1 0 2 3 
22.4 0 3 0 0 4 2 0 0 0 1 1 
______________________________________ 
From the test results presented in the tables, it can be seen that the 
compounds of the present invention have post-emergence herbicidal 
activity. 
Typically, herbicidal compounds of this invention are provided in the form 
of concentrates which require dilution prior to application to plants. The 
usual means for diluting the herbicide is the preparation of herbicidal 
compositions wherein the compound possessing herbicidal activity is mixed 
with other materials. Such other materials may be in either liquid or 
solid form and comprise adjuvants, inert materials, etc. 
The herbicidal composition containing herbicidal compounds of this 
invention are prepared in the usual manner by combining them with other 
materials which are well known in the herbicide art. The following is a 
description of herbicidal compositions employing the herbicidal compounds 
of this invention together with known materials and formulations typically 
utilized in the herbicide art. 
The herbicidal compositions, including concentrates which require dilution 
prior to application to the plants, of this invention contain from 5 to 95 
parts by weight of at least one compound of this invention and from 5 to 
95 parts by weight of an adjuvant in liquid or solid form, for example, 
from about 0.25 to 25 parts by weight of wetting agent, from about 0.25 to 
25 parts by weight of a dispersant, and from 4.5 to about 94.5 parts by 
weight of an inert liquid extender (e.g., water, acetone, 
tetrahydrofuran), all parts being by weight of the total composition. 
Preferably, the compositions of this invention contain from 5 to 75 parts 
by weight of at least one compound of this invention, together with the 
adjuvants. Where required, from about 0.1 to 2.0 parts by weight of the 
inert liquid extender can be replaced by a corrosion inhibitor, such as 
ethanol mercaptan, sodium thiosulfate, or an anti-foaming agent such as a 
dimethylpolysiloxane or both. The compositions are prepared by admixing 
the active ingredient with an adjuvant including diluents, extenders, 
carriers, and conditioning agents to provide a composition in the form of 
finely-divided solid, a liquid of organic origin, water, a wetting agent, 
a dispersing agent, an emulsifying agent, or any suitable combination of 
these. 
The herbicidal compositions of this invention, particularly liquids and 
soluble powders, preferably contain as a conditioning agent one or more 
surface-active agents in amounts sufficient to render a given composition 
readily dispersible in water or in oil. The incorporation of a 
surface-active agent into the compositions greatly enhance their efficacy. 
By the term "surface-active agent" it is understood that wetting agents, 
dispersing agents, suspending agents, and emulsifying agents are included 
therein. Anionic, cationic, and nonionic agents can all be used. 
Preferred wetting agents are alkyl benzene and alkyl naphthalene 
sulfonates, sulfated fatty alcohols, amines or acid amides, long-chain 
acid esters of sodium isothionate, esters of sodium sulfosuccinate, 
sulfated or sulfonated fatty acid esters, petroleum sulfonates, sulfonated 
vegetable oils, polyoxyethylene derivatives of phenols and alkylphenols 
(particularly isooctylphenol and nonylphenol) and polyoxyethylene 
derivatives of the mono-higher fatty acid esters of hexitol anhydrides 
(e.g., sorbitan). Preferred dispersants are methyl cellulose, sodium 
lignosulfonates, polymeric alkyl naphthalene sulfonates, sodium 
naphthalene sulfonate, polymethylene bisnaphthalenesulfonate and sodium 
N-methyl-N-(long chain acid)laurates. 
The application of an effective amount of the compounds or compositions of 
this invention to the plant is essential and critical for the practice of 
the present invention. The exact amount of active ingredient to be 
employed is dependent upon the response desired in the plant as well as 
such other factors as the plant species and stage of development thereof, 
and the amount of rainfall as well as the specific 
bis-(alkoxy)tetrathiotricarboxylate employed. In foliar treatment for the 
control of vegetative growth, the active ingredients are applied in 
amounts from about 0.112 to about 56.0 or more kilograms per hectare. An 
effective amount for phytotoxic or herbicidal control is that amount 
necessary for overall or selective control, i.e., a phytotoxic or 
herbicidal amount. One skilled in the art can readily determine from the 
teachings of this specification, including examples, the appropriate 
application rate. 
Although this invention has been described with respect to specific 
illustrative embodiments, the details thereof are not to be construed as 
limitations, for it will be apparent that various equivalents, changes, 
and modifications may be resorted to without departing from the spirit and 
scope thereof, and it is understood that such equivalent embodiments are 
intended to be included herein.