Patent Publication Number: US-4057638-A

Title: Benzothiazole allophanate fungicides

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of my copending application U.S. Ser. No. 593,107, filed July 3, 1975 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to the use of novel benzothiazole allophanates as fungicides. In particular, such fungicides are useful for the control of such plant diseases as powdery mildew and especially cucumber powdery mildew. 
     The prior art in an article in Chem. Pharm. Bull. 20, 2626 (1972) (Sankyo Chem. Co.) discloses the reaction of 2-aminobenzothiazole and ethoxycarbonyl isothiocyanate; no use is reported for the product. ##STR2## 
     The preparation of the benzimidazole allophanate I from ethoxycarbonylisocyanate has been reported [Chem. Ber., 107, 62 (1974)], although again no use has been disclosed. ##STR3## 
     These references do not suggest the compounds of the instant invention nor do they disclose activity in controlling powdery mildew such as cucumber powdery mildew. 
     SUMMARY OF THE INVENTION 
     Injury due to fungi is prevented by application to the locus to be protected, a fungicidally effective amount of the compound described below; it should be emphasized that the compounds are novel. These compounds have systemic fungicidal activity and consequently can be applied directly to the plant parts to be protected, other parts of the plant or to the media in which the plants are growing. It is preferred to apply the compound directly to the plant. However, all such applications are to be included in the term &#34;applying to plants&#34; as used herein. 
     The compounds of the instant invention have the following formula: ##STR4## where X and Y may independently be hydrogen, methyl ethyl, fluorine, chlorine, or bromine; and 
     R is alkyl of 1 to 4 carbon atoms. 
     Preferred for their higher fungicidal activity are the compounds of Formula II where X or Y may independently by hydrogen, methyl or chlorine. 
     Similarly preferred for their higher fungicidal activity are the compounds of Formula II where R is methyl or ethyl. 
     Most highly preferred for their ease of synthesis or superior fungicidal activity are the compounds of Formula II where X or Y may independently be hydrogen, methyl, or chlorine, and R is methyl or ethyl. 
     Specifically preferred for their outstanding fungicidal activity are: 
     1. Methyl 4-(4-chlorobenzothiazol-2-yl)allophanate, m.p. 319°-320° C; 
     2. methyl 4-(4-methylbenzothiazol-2-yl)allophanate, m.p. 272°-280° C; 
     3. methyl 4-(benzothiazol-2-yl)allophanate, m.p. 338°-340° C; 
     4. methyl 4-(5-chlorobenzothiazol-2-yl)allophanate, m.p. 395° C; 
     5. methyl 4-(5-chloro-4-methylbenzothiazol-2-yl)allophanate, m.p. &gt;275° C (dec). 
     DETAILED DESCRIPTION OF THE INVENTION 
     Synthesis 
     The fungicidally active compounds of Formula II can be prepared by conventional means. For example, they can be prepared by the reaction of an alkoxycarbonyl isocyanate made according to the method of A. J. Speziale, L. R. Smith and J. E. Fedder J. Org. Chem., 30, 4307(1965) with a 2-aminobenzothiazole prepared by the method of C. F. H. Allen, Org. Syn. III, 76 (1955). ##STR5## wherein X and Y may independently be hydrogen, methyl, ethyl, fluorine, chlorine or bromine; and 
     R is alkyl of 1 to 4 carbon atoms either straight chain or branched. 
     The above reaction is carried out by bringing the reactants together in approximately stoichiometric proportions in a suitable organic solvent such as acetonitrile, acetone, benzene, butyl chloride, chlorobenzene, chloroform, o-dichlorobenzene, dichloroethylene, dimethylformamide, dioxane, ethyl acetate, ethyl ether, ethyl formate, methylene chloride, tetrahydrofuran, toluene, trichloroethane, trichloroethylene or xylene. No catalyst is needed but in many cases it is desirable to use a slight excess of the isocyanate reactant, for example 5-10% molar excess. Ordinarily temperatures in the range of 20°-35° C are employed for this reaction; pressure is ambient. The product resulting directly from this reaction is generally obtained by filtration or evaporation of the solvent and is usually of purity satisfactory for direct usage. 
    
    
     The following examples further illustrate the methods for synthesis of these novel, fungicidal compounds. All parts are by weight and all temperatures are in degrees centigrade unless otherwise indicated. 
     EXAMPLE 1 
     Five and one half parts by weight of methoxycarbonyl isocyanate was added gradually with stirring to a solution at room temperature of nine parts by weight of 2-amino-4-chlorobenzothiazole dissolved in 200 parts by weight of dioxane. After stirring the reaction mixture at room temperature overnight, a product was isolated by filtration giving a 45% yield of methyl 4-[4-chlorobenzothiazol-2-yl]allophanate having a melting point of 319°-20° C. 
     Analysis: Calc&#39;d for C 10  H 8  N 3  Cl 1  O 3  S 1  : C 42.04, H 2.82, N 14.71. Found: C 41.62, H 3.19, N 14.03. 
     EXAMPLE 2 
     Three and one half parts by weight of methoxycarbonyl isocyanate was added gradually with stirring to a solution at room temperature of 41/2 parts by weight of 2-aminobenzothiazole dissolved in 150 parts by weight of methylene chloride. After stirring the reaction mixture at room temperature for 12 hours, the product was isolated by filtration giving a 40% yield of essentially pure methyl 4-(benzothiazol-2-yl)allophanate having a melting point of 338°-340° C with decomposition. 
     Analysis: Calc&#39;d for C 10  H 9  N 3  O 3  S: H 3.61, N 16.72, S 12.76. Found: H 3.59, N 16.20, S 13.41. 
     EXAMPLE 3 
     Two and one half parts by weight of methoxycarbonyl isocyanate was added gradually with stirring to a solution of 4 parts by weight of 2-amino-4-methylbenzothiazole dissolved in 250 parts by weight of methylene chloride. The reaction mixture was stirred at room temperature for 12 hours. The solution was concentrated to one fifth the original volume and the solid isolated by filtration to give a 37% yield of methyl 4-(4-methylbenzothiazol-2-yl)allophanate having a melting point of 272°-280° with decomposition. 
     EXAMPLE 4 
     A solution of 2 parts by weight of methoxycarbonylisocyanate in 15 parts by weight of methylene chloride was added gradually with stirring to a solution, at room temperature, of 4 parts by weight of 2-amino-5-chloro-4-methylbenzothiazole in 75 parts by weight of methylene chloride and 50 parts by weight of tetrahydrofuran. After stirring the reaction mixture at room temprature overnight, a product was isolated by filtration giving a 40% yield of methyl 4-(5-chloro-4-methylbenzothiazol-2-yl)allophanate having a melting point greater than 275° . 
     EXAMPLE 5 
     One part by weight of methoxycarbonyl isocyanate was added gradually with stirring to a solution of 2 parts by weight of 2-amino-5-chlorobenzothiazole in 100 parts by weight of methylene chloride and 50 parts by weight of ethyl ether. After stirring the reaction mixture at room temperature overnight, a product was isolated by filtration giving an 85% yield of methyl 4-(5-chlorobenzothiazol-2-yl)allophanate having a melting point of 395°. 
     According to the method of Example 1 using the appropriately substituted 2-aminobenzothiazole and the appropriate alkoxycarbonyl isocyanate the compounds in Table I can be prepared. 
     
                       Table 1                                                     
______________________________________                                    
 ##STR6##                                                                 
X       Y         R              M.P.                                     
______________________________________                                    
Cl      H         C.sub.2 H.sub.5                                         
                                 308-10°                           
Cl      H         CH(CH.sub.3).sub.2                                      
                                 310-12°                           
Cl      H                                                                 
                   ##STR7##      315-7°                            
Cl      H         C.sub.3 H.sub.7                                         
                                 187-8°                            
Cl      H         C.sub.4 H.sub.9                                         
                                 323-5°                            
H       H         C.sub.2 H.sub.5                                         
                                 185-6°                            
H       H         CH(CH.sub.3).sub.2                                      
                                 152-3° dec                        
H       H                                                                 
                   ##STR8##      146-7°                            
H       H         C.sub.3 H.sub.7                                         
                                 162-3°                            
H       H         C.sub.4 H.sub.9                                         
                                 131-2°                            
CH.sub.3                                                                  
        H         C.sub.2 H.sub.5                                         
                                 276-8°                            
CH.sub.3                                                                  
        H         CH(CH.sub.3).sub.2                                      
                                 277-9° dec                        
CH.sub.3                                                                  
        H         CH.sub.3       272-8° dec                        
CH.sub. 3                                                                 
        H                                                                 
                   ##STR9##      277-81° dec                       
CH.sub.3                                                                  
        H         C.sub.4 H.sub.9                                         
                                 270-1°                            
Br      H         CH.sub.3       302-5° dec                        
F       H         CH.sub.3       320-9° dec                        
C.sub.2 H.sub.5                                                           
        H                                                                 
                   ##STR10##     253-62°                           
C.sub.2 H.sub.5                                                           
        H         CH(CH.sub.3).sub.2                                      
                                 264-70°                           
C.sub.2 H.sub.5                                                           
        H         CH.sub.3       280-2° dec                        
H       F         CH.sub.3       &gt;270°                             
F       Cl        CH.sub.3       &gt;270°                             
H       Br        CH.sub.3       --                                       
H       CH.sub.3  CH.sub.3       --                                       
H       C.sub.2 H.sub.5                                                   
                  CH.sub.3       --                                       
______________________________________                                    
 
    
     utility 
     In practicing the fungicidal methods of this invention, one or more of the active ingredients is applied to plants for the control of fungi at a dosage sufficient to control plant disease. Accordingly, these compositions and methods are applicable for the protection of living plants such as vegetables, field crops, ornamental plants and fruit-bearing trees. Some of these compositions are also effective when applied directly to the soil for controlling plant pathogenic fungi. The compounds of this invention are especially effective in controlling Erysiphaceae, powdery mildew fungi. 
     In application to plants, disease control is obtained in most instances by applying the active compound at a dosage or rate from about 0.1 to 10.0 kilograms per hectare. In application directly to the soil for use as a systemic fungicide, in most instances, the dosage or rate is from about 1 to 75 kilograms per hectare. The optimum dosage can be determined in each instance by one of the means conventional in the art. The optimum amount is, of course, determined by and dependent upon the particular fungicidal compound selected, the method of application, the climatic conditions, and, in the case of application to vegetation, the state and condition of growth of the vegetation to be treated. 
     EXAMPLE 6 
     Two-week old Straight Eight variety cucumber plants were sprayed uniformly to the point of run-off with a dispersion consisting of acetone, water, a surfactant and the compound of this invention (see below) at 80, 16, and 3.2 ppm. The following day all plants were inoculated with a distilled water suspension of cucumber powdery mildew (Erysiphe cichoracearum) conidia. After 9 days of incubation in the greenhouse, disease ratings were made by a visual estimate of the percentage of the inoculated leaf area that was diseased. This is a preventive test because chemicals were applied prior to inoculation. A summary of readings, based on three replicate plants for each treatment, is given below. 
     
         ______________________________________                                    
                Percent disease control                                   
                80 ppm 16 ppm   3.2 ppm                                   
______________________________________                                    
methyl 4-(4-chlorobenzothia-                                              
                  100      100      96                                    
zol-2-yl)allophanate                                                      
______________________________________                                    
 
    
     EXAMPLE 7 
     Methyl 4-(5-chlorobenzothiazol-2-yl)allophanate, when sprayed on cucumber plants in accordance with the procedure in Example 6, prevents cucumber powdery mildew (Erysiphe cichoracearum) as shown by the following readings: 
     
         ______________________________________                                    
Percent Disease Control                                                   
80 ppm      16 ppm        3.2 ppm                                         
______________________________________                                    
100         100           88                                              
______________________________________                                    
 
    
     EXAMPLE 8 
     Methyl 4-(5-chloro-4-methylbenzothiazol-2-yl)-allophanate, when sprayed on cucumbers in accordance with the procedure in Example 6, prevents cucumber powder mildew (Erysiphe cichoracearum) as shown by the following readings: 
     
         ______________________________________                                    
Percent Disease Control                                                   
80 ppm      16 ppm        3.2 ppm                                         
______________________________________                                    
100         99            88                                              
______________________________________                                    
 
    
     EXAMPLE 9 
     Methyl 4-(4-chlorobenzothiazol-2-yl)allophanate is prepared in accordance with the procedure of Example 1. 
     The following wettable powder, when dispersed in water and sprayed on apple trees, prevents apple powdery mildew (Podosphaera leucotricha). 
     
         ______________________________________                                    
Ingredient:            Percent by Weight                                  
______________________________________                                    
Methyl 4-(4-chlorobenzothiazol-2-yl)-                                     
                       20                                                 
 allophanate                                                              
Sodium lauryl sulfate  0.25                                               
Sodium lignin sulfonate                                                   
                       .5                                                 
Kaolin clay            79.25                                              
______________________________________                                    
 
    
     EXAMPLE 10 
     Methyl 4-(benzothiazol-2-yl)allophanate is prepared in accordance with the procedure of Example 1. 
     The following dust composition, when dusted on the ground where cucumbers are planted, controls cucumber powdery mildew (Erysiphe cichoracearum). 
     
         ______________________________________                                    
Ingredient:           Percent by Weight                                   
______________________________________                                    
Methyl 4-(benzothiazol-2-yl)allo-                                         
                      30                                                  
 phanate                                                                  
Talc                  70                                                  
______________________________________                                    
 
    
     EXAMPLE 11 
     Methyl 4-(4-methylbenzothiazol-2-yl)allophanate is prepared in accordance with the procedure of Example 1. 
     The following dust composition, when dusted on the surface of the soil in which cucumbers are planted, controls cucumber powdery mildew (Erysiphe cichoracearum). 
     
         ______________________________________                                    
Ingredient:            Percent by Weight                                  
______________________________________                                    
Methyl 4-(4-methylbenzothiazol-2-yl)-                                     
                       30                                                 
 allophanate                                                              
Ground phosphate rock  70                                                 
______________________________________                                    
 
    
     EXAMPLE 12 
     Methyl 4-(4-chlorobenzothiazol-2-yl)allophanate is prepared in accordance with the procedure of Example 1. 
     The following dust composition when dusted on the surface of the soil in which melons are grown prevents watermelon powdery mildew (Erysiphe cichoracearum). 
     
         ______________________________________                                    
Ingredient:            Percent by Weight                                  
______________________________________                                    
Methyl 4-(4-chlorobenzothiazole-2-yl)-                                    
                       30                                                 
allophanate                                                               
Stearated calcium carbonate                                               
                       70                                                 
______________________________________                                    
 
    
     Useful formulations of the compounds of Formula I can be prepared in conventional ways. They include dusts, solutions, suspensions, wettable powders, and the like. Many of these may be applied directly. Sprayable formulations can be extended in suitable media and used at spray volumes of from a few pints to several hundred gallons per acre. High strength compositions are primarily used as in termediates for further formulation. The formulations, broadly, contain about 1 to 99% by weight of active ingredient(s) and at least one of (a) about 0.1 to 20% surfactant(s) and (b) about 5 to 99% solid or liquid diluent(s). More specifically, they will contain these ingredients in the following approximate proportions: 
     
         ______________________________________                                    
            Percent by Weight                                             
            Active                                                        
            Ingredient                                                    
                    Diluent(s)                                            
                              Suffactant(s)                               
______________________________________                                    
Wettable Powders                                                          
              20-90      0-74      1-10                                   
Oil Suspensions,                                                          
               5-50     40-95      0-15                                   
Solutions                                                                 
Aqueous Suspensions                                                       
              10-50     40-84      1-20                                   
Dusts          1-25     70-99     0-5                                     
High Strength 90-99      0-10     0-2                                     
Compositions                                                              
______________________________________                                    
 
    
     Lower or higher levels of active ingredient can, of course, be present depending on the intended use and the physical properties of the compound. Higher ratios of surfactant to active ingredient are sometimes desirable, and are achieved by incorporation into the formulation or by tank mixing. 
     Typical solid diluents are described in Watkins, et al., &#34;Handbook of Insecticide Dust Diluents and Carriers&#34;, 2nd. Edn., Dorland Books, Caldwell, N.J. The more absorptive diluents are preferred for wettable powders and the denser ones for dusts. Typical liquid diluents and solvents are described in Marsden, &#34;Solvents Guide&#34;, 2nd. Edn., Interscience, New York, 1950. Solubility under 0.1% is preferred for suspension concentrates; solution concentrates are preferably stable against phase separation at 0° C. &#34;McCutcheon&#39;s Detergents and Emulsifiers Annual&#34;, Allured Publ. Corp., Ridgeweod, New Jersey, as well as Sisely and Wood, &#34;Encyclopedia of Surface Active Agents&#34;, Chemical Publ. Co., Inc. New York, 1964, list surfactants and recommended uses. All formulations can contain minor amounts of additives to reduce foam, caking, corrosion, microbiological growth, control pH, etc. Preferably, ingredients should be approved by the U.S. Environmental Protection Agency for the use intended. 
     The methods of making such compositions are well known. Solutions are prepared by simply mixing the ingredients. Fine solid compositions are made by blending and, usually, grinding as in a hammer or fluid energy mill. Suspensions are prepared by wet milling (see, for example, Littler, U.S. Pat. No. 3,060,084). 
     For further information regarding the art of formulation, see for example: 
     J. b. buchanan, U.S. Pat. No. 3,576,834, Apr. 27, 1971, Col. 5 Line 36 through Col. 7 Line 70 and Ex. 1-4, 17, 106, 123-140. 
     R. r. shaffer, U.S. Pat. No. 3,560,616, Feb. 2, 1971, Col. 3 Line 48 through Col. 7 Line 26 and Examples 3-9, 11-18. 
     E. somers, &#34;Formulation&#34;, Chapter 6 in Torgeson, &#34;Fungicides&#34;, Vol. I, Academic Press, New York, 1967. 
     EXAMPLE 13 
     
         ______________________________________                                    
Wettable Powder                                                           
methyl 4-(4-chlorobenzothiazol-2-yl)allo-                                 
                            50%                                           
 phanate                                                                  
dioctyl sodium sulfosuccinate                                             
                            1.5%                                          
sodium ligninsulfonate      3%                                            
low viscosity methyl cellulose                                            
                            1.5%                                          
attapulgite                 44%                                           
______________________________________                                    
 
    
     The ingredients are thoroughly blended, passed through an air mill to produce an average particle size well under 15 microns, reblended, and sifted through a U.S.S. No. 50 sieve (0.3 mm opening) before packaging. 
     All compounds of the invention may be formulated in the same manner. 
     EXAMPLE 14 
     
         ______________________________________                                    
Aqueous Suspension                                                        
methyl 4-(4-methylbenzothiazol-2-yl)allo-                                 
                           25%                                            
 phanate                                                                  
hydrated attapulgite       3%                                             
crude calcium ligninsulfonate                                             
                           10%                                            
disodium hydrogen phosphate                                               
                           0.5%                                           
sodium dihydrogen phosphate                                               
                           0.5                                            
water                      61%                                            
______________________________________                                    
 
    
     The ingredients are ground together in a ball or roller mill until the solid particles have been reduced to diameters under 10 microns. 
     EXAMPLE 15 
     
         ______________________________________                                    
Oil Suspension                                                            
methyl 4-(benzothiazol-2-yl)allophanate                                   
                           25%                                            
polyoxyethylene sorbitol hexaoleate                                       
                           5%                                             
highly aliphatic hydrocarbon oil                                          
                           70%                                            
______________________________________                                    
 
    
     The ingredients are ground together in a sand mill until the solid particles have been reduced to under about 5 microns. The resulting thick suspension may be applied directly, but preferably after being extended with oils or emulsified in water. 
     EXAMPLE 16 
     
         ______________________________________                                    
High Strength Concentrate                                                 
methyl 4-(benzothiazol-2-yl)allophanate                                   
                         98.5%                                            
silica aerogel           0.5%                                             
synthetic amorphous fine silica                                           
                         1.0%                                             
______________________________________                                    
 
    
     The ingredients are blended and air milled to produce a high strength concentrate. This material may then be formulated in a variety of ways. 
     EXAMPLE 17 
     
         ______________________________________                                    
Dust                                                                      
high strength concentrate, Example 16                                     
                          10.2%                                           
pyrophyllite, powdered    89.8%                                           
______________________________________                                    
 
    
     The ingredients are thoroughly blended and packaged for use. 
     EXAMPLE 18 
     
         ______________________________________                                    
Wettable Powder                                                           
methyl 4-(4-chlorobenzothiazol-2-yl)allo-                                 
                            80%                                           
 phanate                                                                  
sodium alkylnaphthalenesulfonate                                          
                            2%                                            
sodium ligninsulfonate      2%                                            
synthetic amorphous silica  3%                                            
kaolinite                   13%                                           
______________________________________                                    
 
    
     The ingredients are combined and passed through a hammer mill to produce a wettable powder with average particle size below 20 microns. After a final blending, the product is sifted through a USS No. 50 screen (0.3 mm opening) and packaged.