1-Benzoyl-3-hydroxy-6(1H)-pyridazinones and use as plant growth regulators
DESCRIPTION OF THE INVENTION 
     The use of 1,2-dihydro-3,6-pyridazinedione, commonly called maleic hydrazide, as a plant growth regulator and inhibitor is widespread and has been responsible for significant improvements in the production of certain specific agricultural crops. Many derivatives of this active substance have also been known for some time, none of which has shown any substantial improvement or useful difference in growth regulating activity, in comparison with the parent compound. It has been known, for example that the benzoyl derivative, 1-benzoyl-3-hydroxy-6(1H)-pyridazinone, having the structural formula ##STR2## has growth inhibiting activity approximately equal to maleic hydrazide, as measured by inhibition of bud growth on soybeans. (Canadian J. Biochem. and Physiol. v. 40 p. 1159-1165, Sept. 1962, also U.S. Pat. No. 2,614,917.) When applied to soybean plants which are in the process of setting pods, or on which pods are set, this compound causes the pods to shrink, turn brown and drop. 
     We have discovered a novel class of compounds that differs from the aforementioned compound only by the presence of a single substituent group, which possesses growth regulating activity of a distinctly different type, so that these compounds may be used, for example, to increase the setting and filling of pods on soybeans, as well as for other purposes, such as selective postemergent control of wild oats. Briefly, the novel growth regulators of the present invention are compounds having the structural formula ##STR3## in which Y is --COOH or an agriculturally acceptable salt thereof, --COOR, --CH 2  OH, --CHO, --R, --OR or halogen and R is C 1  to C 4  alkyl or alkenyl. 
    
    
     SYNTHESIS OF THE NOVEL GROWTH REGULATORS 
     The growth regulator compounds are readily synthesized from commercially available intermediates or by reaction of maleic hydrazide with ortho-substituted benzoic acids which are easily made by conventional methods. An illustrative procedure appears below. 
     SYNTHESIS OF 1-(2-CARBOMETHOXYBENZOYL)-3-HYDROXY-6(1H)-PYRIDAZINONE 
     Into a 100 ml round-bottomed flask fitted with a stirrer and reflux condenser there was charged 10.8 g (0.06 mole) of 2-carbomethoxybenzoic acid and 50 ml of chloroform. There was then added 7.8 G (0.066 mole) of SOCl 2 , followed by refluxing for 2 hr. The chloroform was then removed by distillation, followed by addition of 50 ml. of dimethoxyethane, 4.7 g (0.06 mole) of pyridine and 6.7 g (0.06 mole) of maleic hydrazide. The mixture was allowed to stir over night. The resulting reaction mixture was filtered to remove solids. Then the product was precipitated from the filtrate by addition of water and was recovered as a solid by filtration. The solid material was washed with hexane-ether solvent mixture and was filtered and dried. The yield was 6.6 g, m.p. 144°-145° C. Infrared and nuclear magnetic resonance spectra were consistent with the structure of the compound as named above. 
     USE OF THE GROWTH REGULATORS 
     By application of an effective amount of the growth regulators, either pre- or post-emergently, various effects on young plants become apparent. These effects may be demonstrated by means of the following illustrative procedures. 
     PRE-EMERGENT APPLICATION 
     Disposable paper trays about 21/2 inches deep which were filled with soil were sprayed with aqueous spray mixtures at a rate of 10 lb. of active chemical per acre of sprayed area, then were seeded with 6 species of plant seeds and were covered with about 1/4 inch of soil. The spray mixtures were prepared by dissolving the proper amount of growth regulant compound in 15 ml of acetone, adding 4 ml of a solvent-emulsifier mixture consisting of 60 wt. percent of a commercial polyoxyethylated vegetable oil emulsifier (96 wt. percent active ingredient, Emulphor EL-719), 20 wt. percent xylene and 20 wt. percent deodorized kerosene, then bringing total volume up to 60 ml by addition of warm water. Twenty-one days after seeding and treatment the plantings were examined and plant injury was rated according to the following schedule. 
     DEGREE OF EFFECT 
     0=no effect 
     1=slight effect, plants recovered 
     2=moderate effect, injury to 26 to 75 percent 
     3=severe effect, injury to 76 to 99 percent of foliage 
     4=miximum effect (all plants died) 
     POST-EMERGENT APPLICATION 
     Several species of plants were grown in potting soil in disposable styrofoam trays and tomatoes were grown in four-inch pots in the greenhouse. Aqueous spray formulations were prepared and the growing plants were sprayed at a spray volume of 60 gallons per acre and an application rate of 5 lb. per acre. Spray mixtures were prepared in the manner described above. For comparative purposes, plants were also sprayed at 60 gal./acre with a spray mixture containing no growth regulator. Plant injury was again rated according to the schedule disclosed above. 
     Observations of growth regulator effects in both pre- and post-emergent tests were observed and recorded as follows: 
     
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Effect             Abbreviation in Tables                                 
______________________________________                                    
Formative effect on new growth                                            
                   F                                                      
Epinasty           E                                                      
Growth reduction   G                                                      
Necrosis           N                                                      
Non-emergence      K                                                      
Chlorosis          C                                                      
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     In the table below there are tabulated various observations of pre- and post-emergent herbicidal and growth regulator effects of the compounds disclosed above. 
     
                                           TABLE I                                 
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GROWTH REGULANT EFFECTS OF COMPOUNDS OF THE FORMULA                       
 ##STR4##                                                                 
Compound         M.P.                                                     
No.   Y          °C.                            Comments           
__________________________________________________________________________
                       Pre-emergent Effects                               
                       Digitaria                                          
                             Celosia                                      
                                  Bromus                                  
                                      Setaria                             
                                           Raphanus                       
                                                Beta                      
                       sanguinalis                                        
                             plumosa                                      
                                  inermis                                 
                                      italica                             
                                           sativus                        
                                                vulgaris                  
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3712  COOCH.sub.3                                                         
                 144-145                                                  
                       G3F2  G2   K3G3                                    
                                      G3   G2   G2F1                      
4082  COOC.sub.2 H.sub.5                                                  
                 117-119                                                  
                       0     G1   0   G1   G1   G1       Promotes         
4139  COOH       &gt;200 dec.                                                
                       F1G1  F2G2 F3G3                                    
                                      F3G3 F1G1 N2G2     axillary         
4237  CH.sub.3   162-164                                                  
                       0     F1   0   F1   0    0        growth           
4238  Cl         &gt;210 dec.                                                
                       G1    G2   G1  G3   G3   G2                        
4240  COOCH.sub.2 CH.sub.2 CH.sub.3                                       
                 102-105                                                  
                       G1    G2   G2  G3   G2   G1                        
4282  OCH.sub.3  160-170                                                  
                       G2    G2   G2  G3   G2   G1                        
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                       Post-emergent Effects                              
                       Setaria                                            
                             Medicago                                     
                                  Avena                                   
                                      Raphanus                            
                                           Beta Lycopersicum              
                       italica                                            
                             sativa                                       
                                  sativa                                  
                                      sativus                             
                                           vulgaris                       
                                                esculentum                
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3712  COOCH.sub.3                                                         
                 144-145                                                  
                       G2    G2   G3F1                                    
                                      G2   F2G1 N1                        
4082  COOC.sub.2 H.sub.5                                                  
                 117-119                                                  
                       0     0    0   0    0    0        Promotes         
4139  COOH       &gt;200 dec.                                                
                       G1    F1G1 G3F1                                    
                                      0    F1   F1       axillary         
4237  CH.sub.3   162-164                                                  
                       N1G1  N1   G3  N1   N1   F1       growth           
4238  Cl         &gt;210 dec.                                                
                       G1    0    G1  0    F1   0                         
4240  COOCH.sub.2 CH.sub.2 CH.sub.3                                       
                 102-105                                                  
                       G1    G1   --  G1   N1G1 F2G1                      
4282  OCH.sub.3  160-170                                                  
                       G1    0    --  0    0    F1G1                      
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     The use of many of the growth regulator compounds may be demonstrated by treatment of soybeans (Soja max) to increase the number of seed pods and by treating tomato plants (Lycopersicum esculentum) to increase fruit set. In an illustrative experiment, Soja max (Evans variety) and Lycopersicum esculentum (Tiny Tim variety) were grown in 4-inch pots (one plant per pot) filled with greenhouse potting soil (2 parts good top soil, 11/2 parts builders&#39; sand, 11/2 parts peat, fertilized with 5 lb. of 12-12-6 fertilizer and 5 lb. of finely ground limestone per cu. yd.). Aqueous stray formulations were prepared and the potted plants were sprayed at a spray volume of 40 gal. per acre and at application rates of 16, 4, 1 and 1/4 oz. per acre. The spray mixtures were prepared by dissolving the proper amount of growth regulator compound in 15 ml. of actone, adding 2 ml. of a solvent-emulsifier mixture consisting of 60 wt. percent of a commercial polyoxyethylated vegetable oil emulsifier (96 wt. percent active ingredient, Emulphor El-719), 20 wt. percent xylene and 20 wt. percent deodorized kerosene, then bringing total volume up to 80 ml by addition of a 0.156 wt. percent aqueous solution of liquid non-ionic dispersant (90 wt. percent active trimethylnonyl polyethylene glycol ether, Tergitol TMN-10). Two replicates were sprayed at all application rates. For comparative purposes, plants were also sprayed at 40 gal./acre with water. The number of seed pods and of fruit as percentage of arithmetic mean of the numbers of untreated plants was observed within approximately three weeks after spray treatment and the results are tabulated below. The severity of growth regulatory effect on the plants was estimated on a scale of 0 to 10 and is also recorded in the following table: 
     
                       TABLE II                                                    
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GROWTH REGULATING EFFECTS ON TWO SPECIES                                  
        Soja Max         Lycopersicum esculentum                          
              Pod              Fruit                                      
              Count.sup.1                                                 
                        Severity                                          
                               Count.sup.1                                
                                       Severity                           
              Percent in                                                  
                        of     Percent in                                 
                                       of                                 
              Compar-   Growth Compar- Growth                             
              ison to   Regu-  ison to Regu-                              
Comp&#39;d.                                                                   
       Rate   Untreated lating Untreated                                  
                                       lating                             
No.    oz/A   Plants    Effect.sup.2                                      
                               Plants  Effect.sup.2                       
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44082  16     23.sup.3  1.5    64      0                                  
       4      77.sup.4  1      86      0                                  
       1      100.sup.5 1      150     0                                  
44139  16     150       0.5    107     0                                  
       4      100       0      129     0                                  
       1      91        0      107     0                                  
43712  16     64.sup.3  1      0       1                                  
       4      96.sup.3  0      109     0                                  
       1      114       0      150     0                                  
44237  16     41.sup.3  1      0       1                                  
       4      118.sup.3 0      27      0                                  
       1      118       0      136     0                                  
44238  16     68.sup.3  0.5    0       1                                  
       4      145.sup.3 0      177     0                                  
       1      105       0      123     0                                  
44239  16     23.sup.3  1.5    0       1                                  
       4      96.sup.3  0.5    0       0                                  
       1      132       0      14      0                                  
44240  16     27.sup.3  1      0       0.5                                
       4      82.sup.3  0      95      0                                  
       1      96        0      123     0                                  
44282  16     55.sup.3  0.5    14      0.5                                
       4      100.sup.3 0      95      0                                  
       1      141       0      136     0                                  
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 .sup.1 Check = 100                                                       
 .sup.2 Greenhouse rating on scale of 0, no effect; 10, total kill.       
 .sup.3 Axillary growth; aborting pods.                                   
 .sup.4 Pods without beans.                                               
 .sup.5 More buds.                                                        
 
    
     The information presented in tabular form herein will enable a worker in the art to make a selection from among the growth regulator compounds of the invention and to make some judgment with regard to application rates, depending upon the effect which is desired. It may be seen, for example, that total kills of some species of vegetation may occur at application rates as high as 5 to 10 lb. per acre, whereas beneficial effects may be observed on living plants at application rates of 1 lb. per acre or less. 
     The growth regulator compounds are usually formulated as 0.1 to 95 weight percent active ingredient in combination with a surface active agent and one or more inert carriers or diluents, as in emulsifiable formulations, granules and dust formulations, in accordance with established practice in the art. An aqueous spray is usually prepared by mixing a wettable powder or emulsifiable concentrate formulation of a growth regulator with a relatively large amount of water to form a dispersion. 
     Wettable powders comprise intimate, finely divided mixtures of growth regulator compounds, inert solid carriers and surface active agents. The inert solid carrier is usually chosen from among the attapulgite clays, the kaolin clays, the montmorillonite clays, the diatomaceous earths, finely divided silica and purified silicates. Effective surfactants, which have wetting, penetrating and dispersing ability are usually present in a wettable powder formulation in proportions of from 0.5 to about 10 percent by weight. Among the surface active agents commonly used for this purpose are the sulfonated lignins, naphthalenesulfonates and condensed naphthalenesulfonates, alkylbenzenesulfonates, alkyl sulfates and nonionic surfactants such as products of condensation of ethylene oxide with alkylphenols. 
     Emulsifiable concentrates of the growth regulator compounds comprise in each instance, a solution of growth regulator compound in a liquid carrier which is a mixture of water-immiscible solvent and surfactants, including emulsifiers. Useful solvents include aromatic hydrocarbon solvents such as the xylenes, alkylnaphthalenes, petroleum distillates, terpene solvents, ether-alcohols and organic ester solvents. Suitable emulsifiers, dispersing and wetting agents may be selected from the same classes of products which are employed in formulating wettable powders. 
     In general, the growth regulators are seldom applied without the presence of a carrier or surfactant. However, direct application to plant seeds prior to planting may be accomplished in some instances by mixing powdered solid growth regulator with seed to obtain a substantially uniform coating which is very thin and comprises only one or two percent by weight or less, based on the weight of the seed. In most instances, however, a nonphytotoxic solvent, such as methanol is employed as a carrier to facilitate the uniform distribution of growth regulator on the surface of the seed. 
     When a compound is to be applied to the soil, as for a pre-emergence application, granular formulations are sometimes more convenient than sprays. A typical granular formation comprises the growth regulator compound dispersed on an inert carrier such as coarsely ground clay, or clay which has been converted to granules by treatment of a rolling bed of the powdered material with a small amount of liquid in a granulating drum. In the usual process for preparing granular formulations, a solution of the active compound is sprayed on the granules while they are being agitated in a suitable mixing apparatus, after which the granules are dried with a current of air during continued agitation.