1-phenylthio-1-cyclopropanecarbonitrile and substituted phenylthio derivatives thereof as crop protectants

1-Phenylthio-1-cyclopropanecarbonitrile and substituted phenylthio derivatives thereof reduce herbicidal injury of certain food crops treated with a herbicide for control of weeds.

FIELD OF THE INVENTION 
This invention relates to novel substituted phenylthio derivatives of 
1-phenylthio-1-cyclopropanecarbonitrile. The invention also relates to the 
use of 1-phenylthio-1-cyclopropanecarbonitrile and substituted phenylthio 
derivatives thereof in compositions and methods for reducing injury to 
crop plants treated with herbicides. 
BACKGROUND OF THE INVENTION 
Many herbicides injure crop plants by slowing crop plant growth and 
development at herbicide application rates necessary to control weed 
growth. Accordingly, many herbicides cannot be used for controlling weeds 
in the presence of certain crops. Reduction of herbicidal injury to crops 
without an unacceptable corresponding reduction of herbicidal action on 
the weeds can be accomplished by use of crop protectants (also known as 
"herbicide antidotes" or "safeners"). A new class of crop protectants is 
provided by 1-phenylthio-1-cyclopropanecarbonitrile and substituted 
phenylthio derivatives thereof. 
Preparation of 1-phenylthio-1-cyclopropanecarbonitrile, by reaction of 
.alpha.-phenylthioacetonitrile with ethylene dibromide, is described in a 
publication of Makosza et al [Tetrahedron Letters, No. 23, pp. 2391-2394 
(1972)]. There is no suggestion that the cyclopropanecarbonitriles shown 
in the Makosza publication are useful as crop protectants. 
DESCRIPTION OF THE INVENTION 
Herbicidal injury to crop plants may be reduced by application to the crop 
plant locus of an effective amount of a safening agent having the 
structural formula: 
##STR1## 
wherein A is selected from the group consisting of naphthalenyl, 
tetrahydronaphthalenyl, benzodioxol, and 
##STR2## 
wherein X is independently selected from the group consisting of halogen, 
haloalkyl, alkyl, alkenyl, alkoxy, alkylthio, alkylcarbonyl, alkylalkenyl, 
and cycloalkyl; and n is 0 or a whole number from 1 through 5. Examples of 
the radical "naphthalenyl" are 1-naphthalenyl and 2-naphthalenyl. Examples 
of the radical "tetrahydronaphthalenyl" are 1-tetrahydronaphthalenyl and 
2-tetrahydronaphthalenyl. Examples of the radical "benzodioxol" are 
2,3-methylenedioxyphenyl and 3,4-methylenedioxyphenyl. The term "halogen", 
as used herein, includes chloro, bromo, fluoro and iodo radicals. The term 
"haloalkyl" means alkyl moities wherein at least one hydrogen atom has 
been replaced by a halogen including, for example, chloromethyl, 
iodobutyl, dichloroethyl, dibromopropyl, trichloromethyl, trifluoromethyl, 
and the like. The term "alkyl" means straight and branched alkyl radicals 
including, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, 
sec-butyl, tert-butyl, n-pentyl, isopentyl, 1-methylethyl, 
1,1-dimethylethyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylpropyl, and 
the like. The term "alkenyl" means straight or branched chain radicals 
containing at least one carbon-carbon double bond including, for example, 
ethenyl, propenyl and the like. The term "alkoxy" means straight or 
branched chain alkoxy radicals including, for example, methoxy, ethoxy, 
n-propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, 
isopentoxy, and the like. The term "alkylthio" means straight or branched 
chain alkyl radicals containing at least one divalent sulfur atom 
including, for example, methylthio, ethylthio, propylthio, isopropylthio, 
butylthio, pentylthio, and the like. The terms "alkylcarbonyl" means 
straight or branched chain alkyl radicals containing at least one carbonyl 
group including, for example, acetyl, propionyl, pivaloyl, and the like. 
The term "alkylalkenyl" means straight or branched chain alkyl radicals 
containing at least one carbon-carbon double bond, including, for example, 
1-propenyl, 2-methyl-1-propenyl, and the like. The term "cycloalkyl" means 
cyclic moieties composed of three or more alkylene groups including, for 
example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, 
cyclooctyl, and the like. 
Of the foregoing substituents, namely, haloalkyl, alkyl, alkenyl, alkoxy, 
alkythio, alkylcarbonyl, alkylalkenyl and cycloalkyl, those substituents 
having one to six carbon atoms are preferred. 
Herbicides which may be used with benefit in combination with a safening 
agent of the described class include thiocarbamates, triazines and 
acetamides. Examples of thiocarbamates herbicides are 
cis-/trans-2,3-dichloroallyldiisopropylthiocarbamate (common name 
"diallate") and 2,3,3-trichloroallyldiisopropylthiocarbamate (common name 
"triallate"). An example of a triazine herbicide is 
2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine (common name 
"atrazine"). Examples of acetamide herbicides are 
2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide (common name 
"alachlor"); 2-chloro-N-isopropylacetanilide (common name "propachlor"); 
N-(ethoxymethyl)-N-(2-ethyl-6-methyl-1-cyclohexen-1-yl)-2-chloroacetamide; 
N-(ethoxymethyl)-N-(2,5-dimethyl-1-cyclopenten-1-yl)-2-chloroacetamide; 
2-chloro-N-(2-methoxy-1-methylethyl)-6'-ethyl-o-acetotoluidide; 
2-chloro-N-(ethoxymethyl)-6'-ethyl-o-acetotoluidide (common name 
"acetochlor"); ethyl ester of N-chloroacetyl-N-(2,6-diethylphenyl)glycine; 
2-chloro-2',3'-dimethyl-N-(isopropyl)acetanilide; 
2-chloro-2',-6'-diethyl-N-(pyrazolylmethyl)acetanilide; 
2-chloro-6'-trifluoromethyl-N-(isopropoxymethyl)-acetanilide; 
2-chloro-2'-methyl-6'-trifluoromethyl-N-(isopropoxymethyl)acetanilide; 
2-chloro-2'-methyl-6'-trifluoromethyl-N-(ethoxymethyl)acetanilide; 
2-chloro-2'-methyl-6'-methoxy-N-(isopropoxymethyl)acetanilide; 
2-chloro-2'-methyl-6'-methoxy-N-(propoxymethyl)acetanilide; 
2-chloro-2'-isobutoxy-6'-methyl-N-(propoxymethyl)acetanilide; 
2-chloro-2'-isobutoxy-6'-ethyl-N-(ethoxymethyl)acetanilide; and 
2-chloro-2'-methyl-6'-ethoxy-N-(propoxymethyl)acetanilide. 
Many of the safener compounds of the invention are especially useful to 
reduce herbicidal injury to wheat plants and wheat seed caused by 
triallate herbicide. 
The terms "safening agent", "safener", "antidote", "antagonistic agent", 
"crop protectant" and "crop protective" are equivalent terms denoting a 
compound capable of reducing the phytotoxicity of a herbicide to a plant. 
The terms "crop protectant" and "crop protective" are sometimes used to 
denote a herbicide-safener combination which provides protection from 
competitive weed growth by reducing herbicidal injury to valuable crop 
plant while at the same time suppressing weed growth. 
The amount of safening agent employed in the methods and compositions of 
the invention will vary depending upon the particular herbicide with which 
the agent is employed, the rate of application of the herbicide, the 
particular food crop to be protected, and the manner of application to the 
plant locus. In each instance the amount of agent employed is a 
safening-effective amount, that is, the amount which reduces, or protects 
against, crop injury that otherwise would result from the presence of the 
herbicide. The amount of safening agent employed will be less than an 
amount that will substantially injure the crop plant. 
By application to the "plant locus" is meant application to the plant 
growing medium, such as soil, as well as to the seeds, emerging seedlings, 
roots, stems, leaves, or other plant parts. 
The safening agent can be applied to the crop plant locus in a mixture with 
the selected herbicide. For example, where the crop seed is first planted, 
a suitable mixture of safening agent and herbicide, whether in a 
homogenous liquid, emulsion, suspension or solid form, can be applied to 
the surface of, or incorporated in, the soil in which the seed has been 
planted. Or, the herbicide-safener mixture may be applied to the soil, and 
then the seed thereafter "drilled" into the soil below the soil layer 
containing the herbicide-safener mixture. The herbicide will reduce or 
eliminate the presence of undesirable weed and grass plants. Where the 
herbicide would by itself injure the crop seed, the presence of the 
safening agent will reduce or eliminate the injury to the crop seed caused 
by the herbicide. It is not essential that the application of herbicide 
and the safening agent to the plant locus be made using the selected 
herbicide and safening agent in the form of a mixture or composition. The 
herbicide and the safening agent may be applied to the plant locus in a 
sequential manner. For example, the safening agent may be first applied to 
the plant locus and thereafter the herbicide is applied. Or, the herbicide 
may be first applied to the plant locus and thereafter the safening agent 
is applied. 
The application of the safening agent can be made directly to the seed 
before planting. In this practice, a quantity of crop seed is first coated 
with the safening agent. The coated seed is thereafter planted. Then, the 
herbicide is applied to soil in which the coated seed has been planted. 
Several of the mentioned herbicides are known in the art. Propachlor and 
its herbicidal use are disclosed in U.S. Pat. No. 2,863,752 and U.S. Pat. 
Re. No. 26,961. U.S. Pat. No. 3,937,730 discloses and claims 
2-chloro-N-(2-methoxy-1-methylethyl)-6'-ethyl-o-acetotoluidide. The 
herbicidal use of 
N-(ethoxymethyl)-N-(2-ethyl-6-methyl-1-cyclohexen-1-yl)-2-chloroacetamide 
and of 
N-(ethoxymethyl)-N-2-(2,5-dimethyl-1-cyclopenten-1-yl)-2-chloroacetamide 
are disclosed in U.S. Pat. No. 4,351,667. Alachlor, butachlor and 
acetochlor and their herbicidal uses are disclosed in U.S. Pat. No. 
3,442,945 and U.S. Pat. No. 3,547,620. 
The novel compounds can be prepared by reacting an arylthioacetonitrile 
with 1,2-dihaloethane in the presence of a base catalyst as shown, for 
example, in the equation set forth above in Table 1. The selected 
arylthioacetonitrile and dihaloethane may be reacted directly together 
without the use of a solvent or may be reacted in an inert solvent at a 
temperature from about 0.degree. C. to about 150.degree. C., preferably 
from about 20.degree. C. to about 80.degree. C., and at a pressure from 
about 1 to about 10 atmospheres, preferably from about 1 to about 2 
atmospheres. Normally, the reaction is conducted at atmospheric pressure, 
although the pressure can be lower or higher than atmospheric, if needed 
to control the reaction or maintain the reactants and products in the 
desired phase. Useful inert solvents include aliphatic and aromatic 
hydrocarbons, such as methylene chloride, and the like. The reaction may 
be carried out in the presence of a quaternary ammonium catalyst, such as 
tetraethyl ammonium chloride, triethylbenzyl ammonium chloride, and the 
like, in a amount from about 0.1 to about 5.0% by weight, based on the 
weight of the reactants. The molar ratio of acetonitrile to dihaloethane 
can vary from about 1:1.5 to about 1:3. An excess amount of dihaloethane 
is preferred to ensure complete reaction of the acetonitrile. Reaction 
times can vary from a few minutes to several days. Usually, reaction times 
of less than 24 hours are sufficient. 
The following examples are presented for illustrative purposes only and are 
not intended as a restriction on the scope of the invention. All parts are 
by weight unless otherwise indicated. The 
1-phenylthio-1-cyclopropanecarbonitriles of the present invention can be 
prepared according to the general procedure described in Example 1. Table 
1 set forth physical and chemical data for specific compounds prepared in 
accordance with the general procedures of Example 1.