HRP940867A2 - Certain 2-(2',3',4'-trisubstituted benzoyl)-1,3-cyclohexanediones - Google Patents

Description

The technical field to which the invention belongs

The invention is from the field of synthetic organic chemistry and relates to the synthesis of new organic compounds that have herbicidal activity.

Technical problem

The technical problem solved by the present invention is 2-(2',3',4'-trisubstituted benzoyl)-1,3-cyclohexanediones, their use as herbicides and herbicidal preparations containing the compounds.

Within the scope of this invention are novel compounds having the following structural formula:

[image]

in which:

X oxygen or sulfur, preferably oxygen;

R is chlorine or bromine;

R1 is hydrogen or C1-C4 alkyl, preferably methyl;

R2 is hydrogen or C1-C4 alkyl, preferably methyl;

R3 is hydrogen or C1-C4 alkyl, preferably methyl;

R4 is hydroxy, hydrogen or C1-C4 alkyl, preferably methyl; or

R 3 and R 4 are jointly carbonyl (=0) provided that R 1 , R 2 , R 5 and R 6

C1-C4 alkyl, preferably all methyl;

R5 is hydrogen or C1-C4 alkyl, preferably methyl, R6 is hydrogen or C1-C4, preferably methyl, C1-C4 alkylthio, preferably methylthio or C1-C4 alkylsulfonyl, preferably methylsulfonyl, provided that when R6 is C1-C4 alkylthio or C1-C4 alkylsulfonyl, then R3 and R4 are not shared carbonyl;

R 7 is methyl or ethyl; and

R 8 is (1) halogen, preferably chlorine or bromine; (2) nitro; or (3) RbSOn - where n is an integer of 0 or 2, preferably 2 and R5 is (a) C1-C3 alkyl, preferably methyl or ethyl.

The term "C1-C4 alkyl" includes methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl and t-butyl. The term "halogen" includes chlorine, bromine, iodine and fluorine. The term "C 1 -C 4 "Alkoxy" includes methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, isobutoxy and t-butoxy. The term "haloalkyl" includes eight alkyl groups with one or more hydrogens substituted with chlorine, bromine, iodine or fluorine.

Salts of the compounds described above (as described hereinbelow) are also subject of the present invention.

State of the art

European Patent Publication No. 0.135491 and No. 0,137,963, were issued March 27, 1985 and April 24, 1985 and relate to certain 2-(2-halogen-substituted-benzoyl)-1,3-cyclohexane-1,3-diones as herbicides. Compounds can have the following structural formula:

[image]

wherein R to R8 are essentially the same as already defined and R7 may be alkoxy. The compounds of the present invention have unexpectedly better herbicidal activity than the cited compounds of the prior art or provide unexpectedly reduced damage to crop plants.

Description of the solution to the technical problem with implementation examples

Due to tautomerism, compounds from this invention can have the following four structural formulas:

[image]

where X, R, R1, R2, R3, R4, R5, R6, R7, and R8 are as defined above.

The circled part of each of the four tautomers is relatively labile. These protons are acidic and can be separated by any base to give a salt that has an anion with the following four resonance forms.

[image]

where X, R, R1, R2, R3, R4, R5, R6, R7 and R8 are as defined above.

Examples of cations of these bases are inorganic cations such as alkali metals, eg, lithium, sodium and potassium or organic cations such as substituted ammonium, sulfonium or phosphonium where the substituent is an aliphatic or aromatic group.

The compounds of this invention and their salts are active herbicides of general type. That is, they are herbicidally effective against a wide range of plant species. The method for controlling undesirable vegetation of the present invention comprises the application of a herbicidally effective amount of the compounds described above to the surface on which control is desired.

The compounds of the present invention can be made by the following two-step general procedure.

The process is carried out through the production of an enol ester intermediate as shown by reaction (1). The final product is obtained by displacement of the enol ester as shown by reaction (2). The two reactions can be carried out as separate phases by isolating and regenerating the enol ester using conventional techniques before carrying out phase (2), or by adding a cyanide source to the reaction medium after the formation of the enol ester, or it can be carried out in one phase by including the cyanide source at the beginning of the reaction (1) .

[image]

where X and R to R8 are as defined and Y is halogen, preferably chlorine, C1-C4 alkyl-C(O)-O-, C1-C4 alkoxy-C(O)-O- or

[image]

where X, R, R7 and R8 in this part of the molecule are identical to those in the reactant shown above, and the moderate base is as defined, preferably tri-C1-C6 alkylamines pyridine, alkali metal carbonate or alkali metal phosphate.

Basically, in step (1) molar amounts of the dione and substituted benzoyl reactant are used, together with a molar amount or excess of base. The two reactants react in an organic solvent such as methylene chloride, toluene, ethyl acetate or dimethylformamide. The base or benzoyl reactant is preferably added to the reaction mixture with cooling. The mixture is stirred at 0°C-50°C until the reaction is essentially complete.

The reaction product is processed by conventional techniques.

[image]

* = Cyanide source Moderate base = as defined; where X and R through R8 are as defined. Generally, in step (2) a mole of the enol ester intermediate reacts with 1 to 4 moles of a base, preferably with about 2 moles of a moderate base and with from 0.01 mole to about 0.5 mole or more, preferably with 0.1 mole, of a cyanide source (e.g., potassium cyanide or acetone cyanohydrin). The mixture is stirred in the reaction vessel until the displacement is substantially complete at a temperature below 80°C, preferably at about 20°C to about 40°C, and the desired product is regenerated by conventional techniques. ;The term "cyanide source" refers to a substance or substances that, under the conditions for transfer, contain or generate hydrogen cyanide and/or cyanide anion. ;The procedure is carried out in the presence of a catalytic amount of a source of cyanide ion and/or hydrogen cyanide, together with a molar excess, in compared to the enol ester, some moderate bases. ;Preferred cyanide sources are such alkali metal cyanides as sodium-1 potassium cyanide; cyanohydrins of methylalkylketones having from 1-4 carbon atoms in the alkyl groups, such as cyanohydrins of acetone or methylisobutylketone; cyanohydrins of benzaldehyde or such C2-C5 aliphatic aldehydes as acetaldehyde, propionaldehyde, etc.; zinc cyanide; tri(lower alkyl)silyl cyanides, particularly trimethyl silylcyanide; and hydrogen cyanide itself. ;Hydrogen cyanide is considered the most suitable since it gives a relatively fast reaction and is not expensive. Among cyanohydrins, the preferred source of cyanide is acetone cyanohydrin. The cyanide source is used in an amount of up to about 50 mole percent based on enol ester. It can an amount as small as about 1 mole percent can be used to produce a reaction of acceptable rate at about 40°C with small amounts of material. Larger scale reactions give more reproducible results with slightly higher catalyst levels of about 2 mole percent. Generally, about 1-10 mole % of the cyanide source is preferred. ;The procedure is carried out with a molar excess, in relation to the enol ester, of some moderate base. By the term "moderate base" is meant a substance that acts as a base and yet its base strength or activity lies between the activity of strong bases, such as hydroxides (which could cause hydrolysis of enol esters) and the activity of weak bases such as bicarbonates (which they would not function efficiently). Moderate bases suitable for use in this embodiment include both organic bases, such as tertiary amines, and inorganic bases, such as alkali metal carbonates and phosphates. Suitable tertiary amines include such trialkylamines as triethylamine, such trialkanolamines as triethanolamine and pyridine. . Suitable inorganic bases include potassium carbonate and trisodium phosphate. The base is used in an amount of about 1 to about 4 moles per mole of enol ester, preferably about 2 moles per mole. When the source of cyanide is an alkali metal cyanide, specifically potassium cyanide, a phase transfer catalyst can be included in the reaction. Particularly preferred phase transfer catalysts are crown ethers. A number of different solvents can be useful in this process, depending on the nature of the acid chloride or acylated product. The preferred solvent for this reaction is 1,2-dichloroethane. Other solvents that may be used, depending on the reactants or products, include toluene, acetonitrile, methylene chloride, ethyl acetate, dimethylformamide, and methylisobutyl ketone (MIBK). Generally, depending on the nature of the reactants and the source of the cyanide, the transfer can be carried out at temperatures up to about 50°C. The substituted benzoyl chlorides described above can be made from appropriately substituted benzoic acids as taught in Reagents for Organic Synthesis, Vol. I, L.R Fieser and M. Fieser, pp. 767-769 (1967). ;[image] ;where X, R, R7 and R8 are as defined earlier. ;The 5-hydroxy-4,4,6,6-tetra-substituted 1,3-cyclohexanediones described above can be made according to reaction (d). ;[image] ;where R1, R2, R5 and R6 are as defined and R4 is hydrogen. In reaction (d), NaBH4 is added to a basic methanol solution of syncarpic acid under controlled conditions and the reaction is carried out at room temperature. The reaction solution is acidified and the product is reacted by conventional techniques. When R7 is C1-C4 alkyl, C2-C5 alkenyl, C2-C5 alkynyl or cyano, the dione can be made by reacting such a nucleophile as methyllithium with some 4,4,6,6-tetra-substituted 1,3,5- with cyclohexantrione as shown in reaction (e). ;[image] ;where R 1 , R 2 , R 4 , R 5 and R 6 are as defined and R 4 is C 1 -C 4 alkyl, C 2 -C 5 alkenyl, C 2 -C 5 alkynyl or cyano. In reaction (e), the lithium compound is added to a solution of syncarpic acid reactants under controlled conditions and reacted at room temperature. The reaction solution is then acidified and the product is regenerated by conventional techniques. ;Substituted 1,3-cyclohexanediones of the formula: ;[image] ;in which R1 to R5 are as defined and R6 is Ci-C4 alkylthio or Ci-C4 alkylsulfonyl can be made by various general procedures according to the teachings of Modern Synthetic Reactions , 2nd Edition, Chapter 9, H.O. House, W.A. Benjamin, Inc., Menlo Park, CA (1972). Intermediates based on trisubstituted benzoic acid chloride are made by the general process shown in Figure 1 on the next page, where R10 is C1-C2 alkyl, preferably methyl; formyl; cyano; carboxy or -CO2Ra where R3 is C1-C4 alkyl, preferably ethyl; most preferably R10 is -CO2C2H5; R 11 is -CH 2 CH 2 OCH 3 ; -CH2CH2OC2H5; -CH2CH2SCH3 or -CH2CH2SC2H5; R 12 is C 1 -C 4 alkyl, preferably methyl, ethyl or n-propyl; and R 15 is -CH 2 CH 2 OCH 3 or -CH 2 CH 2 OC 2 H 5 . Rx and Rz are C1-C4 alkyl. X of R11X represents halogen, preferably chlorine or iodine. ;[image] ;In Figure I, and especially in Reaction Phases (A) to (K), the following should be considered: ;In general, in Reaction Phase (A), a molar amount of 3-substituted phenol reacts with 2 moles of the brominating agent N- bromo-C1-C4-alkylamine, preferably N-bromo-tetra-butylamine in such a solvent as methylene chloride, at a temperature between -70°C to 250°C. After this reaction, free brominated phenol is formed by reacting with such a strong acid as HCL. N-bromo- C1-C4 alkylamine can be made by reacting 2 moles of C1-C4 -alkylamine and moles in some such solvent as methylene chloride at, low temperatures, so that 1 mol of N-bromo-C1-C4-alkylamine is obtained. The final reaction product is regenerated by conventional techniques. ;For reaction step (B), one mole of the dibromo-substituted-phenol reaction product from Step (A) is reacted with such a suitable alkylating agent as 2-chloroethylethylether, 2-chloroethyl-methylsulfide, 2-chloroethyl-ethylsulfide or C1- C4 -alkyl chloride together with a catalytic amount of potassium iodide and with a molar excess of a base such as potassium carbonate. Such alkyl iodides as methyl iodide or ethyl iodide can also be used. In these cases, no catalytic potassium iodide is required and little or no heating is required. The reaction is carried out at 50°C to 80°C for 4 hours with stirring. The reaction product is regenerated by conventional techniques. For Reaction Phase (C), the dibromo compound from Reaction Phase (B) is reacted with an equal amount of C1-C4 -alkyl mercaptan together with a molar excess of such a base as potassium carbonate in such a solvent as dimethylformamide. For reaction (H) a molar amount of 2-bromo-3-substituted-4-alkylthio-ester or cyano compound is hydrolyzed with a base such as sodium hydroxide in the corresponding 2-bromo-3-substituted-4-alkylthio- benzoic acid. Hydrolysis is performed in a solvent such as an 80 percent methanol-water mixture. The reaction can be carried out at 25-100°C with stirring. The desired product is regenerated using conventional techniques. ;For Reaction Phase (J), when “R10” is a cyano or ester group, a molar amount of the corresponding 2-bromo-3-substituted-4-mtro compound is hydrolyzed with a base such as sodium hydroxide to the corresponding 2-bromo- 3-substituted-4-mtro-benzoic acid. Hydrolysis is carried out in such a solvent as an 80 percent methanol-water mixture. The reaction can be carried out at 25-100°C with stirring. The desired product is regenerated using conventional techniques. When "R10" is formyl, methyl or ethyl, a molar amount of the corresponding 2-bromo-3-substituted-4-nitro compound is oxidized to the corresponding trisubstituted benzoic acid with an excess of such an oxidizing agent as potassium permanganate or sodium hypochlorite according to known procedures. ;For Reaction Phase (K) the trisubstituted benzoic acid alkyl ester is converted to trisubstituted benzoic acid using the hydrolysis phase discussed in Reaction Phase (H). ;The intermediate benzoic acids described herein can be readily converted into their corresponding acid chlorides and then into their acid cyanides, as appropriate, by the following two reactions, First, a mole of oxalyl chloride and a catalytic amount of dimeth formamide in some suitable solvent, such as methylene chloride, and at a temperature of 20 to 40°C for 1 to 4 hours, it is heated with 1 mole of intermediate benzoic acid. The corresponding benzoic acid cyanide can easily be made from benzoic acid chloride by reaction with cuprocyanide at 50° to 220°C for 1 to 2 hours. Intermediates based on trisubstituted benzoic acid chloride are useful for making the previously described herbicidal 2-(2',3',4'-trisubstituted-benzoyl)-1,3-cyclohexanediones. The following series of examples describes the synthesis of representative intermediate compounds of this invention. The structures of all compounds from the examples and tables were verified using nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and mass spectroscopy (MS). ;EXAMPLE 1 ;Ethyl 2,4-dibromo-3-hydroxybenzoate ;[image] ;Using a similar procedure to omm described (D.E. Pearson, R.D. Wysong and CV. Breder in J, Org. Chem. 32, 2358 (1967) , 59 grams (g) of t-butylamine (0.8 mol) in 400 milliliters (ml) of methylene chloride are added to a 1-liter, 3-necked flask equipped with a mechanical stirrer, a nitrogen inlet, and an addition funnel with a pressure equalization attachment. This mixture is cooled to -65°C with a dry ice/isopropanol mixture. 64 grams (0.4 mol/m/) of bromine, which is diluted in 50 ml of methylene chloride, is slowly added (for 1 hour) to the cooled solution. the mixture was stirred for 1 hour at approximately -60° C. Ethyl 3-hydroxybenzoate (0.2 moles, 33.2 grams) was added in one portion to the cooled reaction mixture. This mixture was allowed to warm to room temperature overnight. The white solid was filtered and washed with a minimal amount of methylene chloride and converted to free phenol (ethyl 2,4-dibromo 3-hydroxybenzoate) using 500 ml of met ylene chloride and 400 ml of 2 normal (N) hydrochloric acid. Gas chromatography showed that the product (49 g) was 92% pure. This material was a viscous oil. ;Additional examples were made by the same procedure as described in Example 1 and are listed in Table 1. ;[image] ;EXAMPLE 2 ;Ethyl 2,4-dibromo-3-(2-methoxyethoxy)-benzoate ;[image] ; The ethyl ester from Example 1 (32.4 g, 0.1 mol) was dissolved in 200 ml of dimethylformamide (DMF) and an excess of potassium carbonate (27.6 g, 0.2 mol) and 2-chloroethylmethylether (18.8 g, 0.2 mol) were added together with a catalytic amount of potassium -iodide (4.8 g, 0.03 mol). This reaction mixture was stirred vigorously and maintained at 70°C for 4 hours. Normal workup gave 31.8 g of ethyl 2,4-dibromo-3-(2-methoxyethoxy)-benzoate as an oil, 94% pure by gas chromatography. This ester will readily hydrolyze to its acid by the procedure described in Example 7. ;Additional compounds were made by the same procedure as described in Example 2 (except where an alkyl iodide was used; then the potassium iodide catalyst was omitted and either requires little or no heating) and are listed in Table 2. ;[image] ;EXAMPLE 3 ;Ethyl 2-bromo-3-(2-methoxyethoxy)-4-Ethylthiobenzoate ;[image] ;Ethyl 2,4-dibromo- 3-(2-Methoxyethoxy)-benzoate (15.3 g, 0.04 mol) was dissolved in 125 ml of DMF and potassium carbonate (13.8 g, 0.1 mol) and ethyl mercaptan (4 g, 0.064 mol) were added. This mixture is heated to 70°C, under nitrogen, with vigorous stirring, for 4 hours. Normal workup afforded 14.3 g of crude product (82% of desired product based on gas chromatography), ethyl 1-bromo-3-(2-methoxyethoxy)-4-ethylthiobenzoate as a viscous oil. This ester could be readily hydrolyzed to its free acid by the procedure described in Example 7. The crude ester was purified by chromatography on silica eluting with ether/pentane to give 11.2 g of product as an oil. ;The ester made above was hydrolyzed into the appropriate acid according to the procedure described in Example 8. ;Additional compounds were made by the same procedures as described in Example 3 and are listed in Table 3. ;[image] ;EXAMPLE 4 ;Ethyl 2- bromo-3-hydroxy-4-mtrobenzoate ; [image] ; 0.1 mol of 3-hydroxy-4-nitrobenzoic acid ethyl ester is monobrominated using the procedure described in Example 1, except that only one equivalent of bromine and two equivalents of t-butylamine are used . This reaction gave ethyl 2-bromo-3-hydroxy-4-nitrobenzoate in a yield of 70.1%. It had a melting point of 58-61°C. ;Ethyl ester of 3-hydroxy-4-nitrobenzoic acid was made as follows: ;15 ml of concentrated sulfuric acid was added to 100 g of 3-hydroxy-4-nitrobenzoic acid in 300 ml of ethanol. This solution is refluxed for 3 hours and then the Dean-Stark switch is connected and 100 ml of the ethanol-water mixture is distilled off. The reaction mixture is cooled and poured onto 500 grams of ice. The resulting solid is collected, dissolved in 500 ml of ether and the ether solution is washed three times with 1% aqueous sodium bicarbonate. The ether layer is dried and concentrated to give 103.8 g of pure ester. ;EXAMPLE 5 ;Ethyl 2-bromo-3-(2-methoxyethoxy)-4-nitrobenzoate ;[image] ;Using a similar procedure from example 2, 0.2 moles of ethyl 2-bromo-3-hydroxy-4-nitrobenzoate and an excess of potassium of carbonate (0.35 mol), together with a catalytic amount of potassium iodide (7.2 g, 0.045 mol) react with 350 ml of dimethylformamide. After heating at 70°C for 4 hours, normal work-up gave 0.187 moles of ethyl 2-bromo-3-(2-methoxyethoxy)-4-nitrobenzoate as a viscous oil. This ester can be readily hydrolyzed using the procedure of Example 8. ;Additional compounds were made by the same procedure as described in Example 5 and are listed in Table 4. ;[image] ;EXAMPLE 6 ;Ethyl 2-bromo-3-(2 -methoxyethoxy)-4-ethylthiobenzoate ;[image] ;Using a similar procedure to that of Example 3, 0.1 mol of ethyl 2-bromo-3-(2-methoxyethoxy)-4-nitrobenzoate and an excess of potassium carbonate (0.2 mol) and a slight excess ethyl mercaptan (0.125 mol) is reacted in 200 ml of dimethylformamide at 0°C, under nitrogen. The reaction was stirred overnight at room temperature. Normal processing gave the desired product in essentially quantitative yield. This compound was compared to the product of Example 3 and the compounds were identical in all chromatographic and spectroscopic comparisons. ;EXAMPLE 7 ;Ethyl 2-bromo-3-(2-methoxyethoxy)-4-ethylsulfoyl-benzoate ;[image] ;Ester, ethyl 2-bromo-3-(2-methoxyethoxy)-4-ethylthiobenzoate from Example 3 (12 g) dissolve in 100 ml of methylene chloride and slowly add pure solid m-chloroperoxy-benzoic acid (85% pure, 0.1 mol) over a period of 2 hours. The crude reaction mixture was stirred overnight. Excess peracid is destroyed with sodium bisulfite (100 ml, 5% solution). The organic layer is washed three times with base, dried, concentrated and chromatographed on silica gel (CH2Cl2/(C2H5)2O) so that 8.3 grams of pure ethyl 2-bromo-3-(2-methoxyethoxy)-4-ethylsulfonylbenzoate are obtained. as a viscous oil. ;Additional compounds were made by the same procedure as described in Example 7 and are listed in Table 5. ;[image] ;EXAMPLE 8 ;2-Bromo-3-(2-methoxyethoxy)-4-ethylsulfonylbenzoic acid ;[image] ; the extracts are acidified and extracted three times with methylene chloride. The methylene chloride was dried and concentrated to give 6.6 grams of 2-bromo-3-(2-methoxyethoxy)-4-ethylsulfoylbenzoic acid as a viscous oil. ;Additional compounds were made by the same procedure as described in Example 5 and are listed in Table 6. ;[image] ;Other intermediate compounds can be made using the general procedure shown in Figure II on the next page where R20 is C1- C2 alkyl, preferably methyl; formyl; cyano; carboxy; or –CO2Rc where Rc is C1-C4 alkyl, preferably ethyl; most preferably R 20 -CO 2 C 2 H 5 ; R 21 is –CH 2 CH 2 OCH 3 ; -CH2CH2OC2H5; -CH2CH2SCH3; or -CH2CH2SC2H5. R22 is C1-C4 alkyl, preferably methyl, ethyl or n-propyl and R25 is -CH2CH2OCH3 or -CH2CH2OC2H5. R 2 is C 1 -C 4 alkyl. ;[image] ;Having Figure II as a reference, and especially Reaction Phases (AA) to (GG), the following should be considered: ;In general, in Reaction Phase (AA), a molar amount of 3-substituted phenol reacts with 2 moles of chlorine and with catalytic with an amount of C1-C10 alkylamine, preferably tert-butylamine or diisopropylamine in a solvent such as methylene chloride, at a temperature between -70°C and 700°C. After this reaction, the free chlorinated phenol is isolated by normal procedures. ;For Reaction Phase (BB), one mole of dichloro-substituted phenolic reaction product from Phase (AA) is reacted with such a suitable alkylating agent as 2-chloroethylethylether, 2-chloroethylmethylether, 2-chloroethylmethylsulfide, 2-chloroethylethylsulfide or C1-C4 alkyl chloride together with a catalytic amount of potassium iodide and a molar excess of such a base as potassium carbonate. Such alkyl iodides as methyl iodide or ethyl iodide can also be used. In these cases, no catalytic potassium iodide is required and little or no heating is required. The reaction is carried out at 25°C to 80°C for 4 hours with stirring. The reaction product is regenerated by conventional techniques. ;For the Reaction Phase (CC), the dichloro compound from the Reaction Phase (BB) reacts with an equal molar amount of C1-C4 alkyl mercaptan together with a molar excess of a base such as potassium carbonate in a solvent such as dimethylformamide. The reaction takes place for several hours at a temperature between 50°C to 100°C with stirring under an inert atmosphere such as nitrogen. The desired reaction product is regenerated by conventional techniques. ;For the Reaction Phase (DD), the molar amount of the alkyl ester of 2-chloro-4-alkylthio-benzoic acid is oxidized with at least 3 moles of such an oxidizing agent as m-chloro-perbenzoic acid, in a suitable solvent such as methylene chloride, by mixing reactant solutions at 20°C to 100°C The desired intermediates are regenerated by conventional techniques. During this reaction phase, the 4-alkylthio substituent is oxidized to the corresponding alkylsulfone. For the Reaction Phase (EE) a molar amount of 2-chloro-3-substituted-4-alkylthio-ester or cyano compounds is hydrolyzed with a base such as sodium hydroxide to the corresponding 2-chloro-3-substituted-4-alkylthio- benzoic acid. Hydrolysis is carried out in a solvent such as an 80% methanol/water mixture. The reaction can be carried out at 25-100°C with stirring. The desired product is regenerated using conventional techniques. ;For the Reaction Phase (FF) the trisubstituted benzoic acid alkyl ester is converted to the trisubstituted benzoic acid by the hydrolysis phase discussed in the Reaction Phase (EE). ;Alternatively, the reaction product, tri-substituted benzoic acid from the Reaction Phase (FF) can be directly made from the reaction product of the Reaction Phase (CC) by combining the hydrolysis of 2-chloro-3-substituted-4-alkylthio ester or cyano compound into the corresponding benzoic acid and by oxidizing the 4-alkylthio substituent to the corresponding 4-alkylsulfone. The hydrolysis and oxidation phases can be performed together by reacting a mole of the ester or cyano compound with at least 5 moles of sodium or calcium hypochlorite in a suitable solvent such as a dioxane-water mixture, by heating the reactant solution from about 25°C to about 100°C, and after that by acidification with concentrated hydrochloric acid. Filtration of the obtained precipitate gives the desired product. ;For the Reaction Phase (GG) the dichloro compound from the Reaction Phase (BB) is converted to benzoic acid using the hydrolysis step discussed in the Reaction Phase (BB). ;The intermediate benzoic acids described here can be readily converted to their corresponding acid chlorides and then to their acid cyanides, if desired, by the following two reactions. First, a mole of oxalyl chloride and a catalytic amount of dimethylformamide in a suitable solvent, such as methylene chloride, at a temperature of 20 to 40°C, for 1 to 4 hours is heated with a mole of intermediate benzoic acid. The corresponding benzoic acid cyanide can easily be made from benzoic acid chloride by reaction with cuprocyanide at 50° to 220°C for 1 to 2 hours. The following series of examples describes the synthesis of representative intermediate compounds of this invention. The structures of all compounds from the examples and tables were verified by nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and mass spectroscopy (MS). ;EXAMPLE 9 ;Ethyl 2,4-dichloro-3-hydroxybenzoate ;[image] ;In a 3-necked, 1-liter flask equipped with a mechanical stirrer, a condenser, a thermometer and a diffusion tube, a solution of 106 grams ( 0.64 moles) of ethyl 3-hydroxybenzoate and 0.5 grams of diisopropylamine in 600 ml of dichloromethane at reflux. Chlorine (112 grams, 1.6 moles) is added to the diffusion tube over a period of 6 hours, then cooled to room temperature. After cooling, the solution is washed with 200 ml of 5% sodium bisulfite solution, then with 200 ml of water, dried (MgSO4) and reduced in vacuo. The yield was 151 g of oil. This mixture of chlorinated compounds (66% of the above product) can be recrystallized in an ether/pentane mixture by cooling to -20°C to give pure ethyl 2,4-dichloro-3-hydroxybenzoate. ;The structure of this compound and all examples was verified by nuclear magnetic resonance (NMR), infrared spectroscopy (IR) and mass spectroscopy (MS). ;Additional compounds were made by the same procedure as described in Example 9 and are listed in Table 7. ;[image] ;EXAMPLE 10 ;Ethyl 2,4-dichloro-3-(2-methoxyethoxy)-benzoate ;[image] ; A solution of 18 g (77 millimoles, mmol) of ethyl 2,4-dichloro-3-hydroxybenzoate, 22 g (3 equivalents)(eq) of 2-chloroethylmethylether, 22 g (2 eq) of potassium carbonate and about 0.5 g of sodium iodide in 100 ml of DMF is heated to 80°C for 1.5 hours. 400 ml of ether is added to the cooled solution. The organic phase is washed with 100 ml of water (2 times), with 100 ml of 100% NaOH and with 100 ml of 10% HCl. Dry (MgSO4) and evaporate under vacuum. The yield was 20 g (68 mmol). ;Additional compounds were made by the same procedure as described in Example 10 (except where an alkyl iodide is used; then the potassium iodide catalyst is omitted and little or no heating is required) and are listed in Table 8. ;[image] ;EXAMPLE 11 ;Ethyl 2-chloro-3-(2-methoxyethoxy)-4-ethylthiobenzoate ;[image] ;A solution of 10 g (34 mmol) of ethyl 2,4-dichloro-3-(2-methoxyethoxy)-benzoate, 10 g (4 eq) of ethanethiol and 10 g (2 eq) of potassium carbonate in 100 ml of DMF are heated (approximately 100°C) for 2 hours, then cooled overnight. Add 400 ml of diethyl ether and wash with 100 ml of water (twice), 100 ml of 10% HCl and 100 ml of 10% NaOH. ;Dried (MgSO4) and evaporated in vacuo, Yield .10 g (31 mmol) of oil. ;Additional compounds were made as described in Example 11 and are listed in Table 9. ;[image] ;EXAMPLE 12 ;Ethyl 2-chloro-3-(2-methoxyethoxy)-4-ethylsulfonyl-benzoate ;[image] ; The ester, ethyl 2-chloro-3-(2-methoxyethoxy)-4-ethylbenzoate from Example 3 (10 g) is dissolved in 100 ml of methylene chloride and cooled with an ice bath. Then 18 g of solid m-chloroperoxybenzoic acid (85% pure, 2.2 eq) were added in batches over a period of 2 hours. The crude reaction mixture was allowed to warm to room temperature. After 1 hour at room temperature, the excess peracid is destroyed with sodium bisulfite (100 ml of 5% solution). The organic layer was washed twice with 5% sodium hydroxide (100%) and separated in vacuo to give 11.3 g of pure ethyl 2-chloro-3-(2-methoxyethoxy)-4-ethylsulfonylbenzoate as a viscous oil. ;Additional compounds were made by the same procedure as described in Example 12 and are listed in Table 10. ;[image] ;[image] ;EXAMPLE 13 ;2-chloro-3-(2-methoxyethoxy)-4-ethylsulfoylbenzoic acid; [image] 16 ml (1.2 eq) of 10% sodium hydroxide was added dropwise to 11.3 g (0.03 mol) of ethyl 2-chloro-3-(2-methoxyethoxy)-4-ethylsulfoylbenzoate in 100 ml of 96% ethanol. After stirring at room temperature for 4 hours, 100 ml of diethyl ether is added and the organic phase is extracted with 50 ml of 5% NaOH. The aqueous phase is acidified with 10% HCl and extracted twice with 50 ml of chloroform. The organic phase is dried with MgSO4 and concentrated in vacuo to give 8.8 grams of 2-chloro-3-(2-methoxy-ethoxy)-4-ethylsulfoylbenzoic acid as a viscous oil. ;Additional compounds were made by the same procedure as described in Example 13 and are listed in Table 11. ;[image] ;EXAMPLE 14 ;2-chloro-3-(2-methoxyethoxy)-4-ethylthio-benzoic acid ;[image ] ; Three grams (8.2 mmol) of ethyl 2-chloro-3-(2-methoxyethoxy)-4-propanethiobenzoate were dissolved in 20 ml of 96% ethyl alcohol. To this is added 3.9 ml of 10% sodium hydroxide in water. After stirring for 4 hours at room temperature, 100 ml of diethyl ether was added to the solution. The solution is extracted twice with 50 ml of 5% sodium hydroxide solution. The combined base extracts were acidified with 10% hydrochloric acid and extracted twice with 50 ml portions of chloroform. The chloroform extracts were dried over magnesium sulfate and the chloroform was removed in vacuo to give the free acid (2.0 g, 72%) as a soft solid. ;Additional compounds were made by the same procedure as described in Example 14 and are listed in Table 12. ;[image] ;EXAMPLE 15 ;2,4-dichloro-3-(2-methoxyethoxy)benzoic acid ;[image] ;16 grams (41 mmol) of ethyl 2,4-dichloro-3-(2-methoxyethoxy)-benzoate are dissolved in 100 ml of 96% ethanol. To this is added, in batches, 18 ml (ca. 1.1 eq) of 10% sodium hydroxide. After stirring for 4 hours at room temperature, 250 ml of ether was added to the solution. The solution is extracted twice with 50 ml of 5% sodium hydroxide. The combined alkaline extracts are acidified with a 10% hydrochloric acid solution and extracted twice with 75 ml of chloroform. The chloroform extracts were dried (magnesium sulfate) and the chloroform was removed in vacuo to give the free acid (12.8 g, 79%) as a white solid. ;Additional compounds were made by the same procedure as described in Example 15 and are listed in Table 13. ;[image] ;The benzoic acids described above can be easily converted to their acid chlorides using oxalyl chloride and a catalytic amount of dimethylformamide. These acid chlorides can be reacted with the above-described 1,3-cyclohexanedione to form the above-described herbicidal 2,3,4-trisubstituted-benzoyl-1,3-cyclohexanediones according to the two-phase reaction described earlier. ;The following example describes the synthesis of representative 1,3-cyclohexanediones. EXAMPLE 16 4-Methylthiocyclohexane-1,3-dione 1-(Methylthio)-2-propanone/25 grams (g), 0.24 mol), ethyl acrylate (24 g, 0.24 mol) and benzyltrimethylammonium methoxide/2 ml of a 40 wt.% solution in methanol/ is dissolved in toluene (100 ml). A solution of sodium methoxide (77.8 g of 25 wt.% in methanol, 0.36 mol) is then added to the solution dropwise and at such a rate that the temperature is maintained below 35°C. After stirring for another 2 hours at room temperature, the reaction mixture is poured into 200 ml of ice water and extracted with 100 ml of ether. The aqueous phase is acidified with 2N hydrochloric acid and extracted with ether. The ether layer is dried over magnesium sulfate, filtered and concentrated in vacuo to obtain 23.1 g of oil. The oil was dissolved in benzene (100 ml) and the desired product was gently deposited from the solution in the form of waxy crystals (9.8 g). The following example describes the synthesis of a representative 2-(2', 3', 4'-trisubstituted)-1,3-cyclohexanedione. EXAMPLE 17 2-/2'-Bromo-3'-(2-methoxyethoxy)-4'-ethylsulfonyl)benzoyl/-1,3-cyclohexanedione ;[image] ;2-Bromo-3-(2-methoxyethoxy) -4-Ethylsulfonyl-benzoic acid (6.1 g, 0.018 mol) is diluted in 50 ml of methylene chloride and 2 drops of DMF are added, followed by slow addition of oxalyl chloride (3.81 g, 0.03 mol). When the addition is complete, the solution is refluxed for 1 hour, cooled and concentrated in vacuo. The crude acid chloride is diluted in 25 ml of methyl chloride and 2.24 g (0.02 mol) of 1,3-cyclohexanedione is added, followed by an excess of triethylamine (4.0 g). After stirring overnight, the organic layer was washed three times with dilute (1N) hydrochloric acid, dried and concentrated. The crude enol ester is dissolved in 25 ml of acetonitrile and ten drops of acetone-cyanohydrin and 4 ml of triethylamine are added and this reaction mixture is stirred at room temperature for 48 hours. The organic phases are washed three times with 1N hydrochloric acid and then extracted with base. The base extracts are combined and acidified and extracted three times with 50 ml of methylene chloride each. The methylene chloride extracts were dried, concentrated and chromatographed on silica gel using ether/methylene chloride/acetic acid to give 3.96 g of pure 2-(2'-bromo-3'-(2-methoxyethoxy)-4'-ethylsulfonylbenzoyl, 1,3 -cyclohexanedione. The following is a Table of certain selected compounds that can be made according to the procedure that was described. Each connection was given its own number and that number is used in the rest of the application. ;[image] ;Tests for Herbicide Evaluation ;As mentioned earlier, the compounds described herein, which are produced in the manner described above, are phytotoxic compounds that are useful and valuable for the control of various plant species. Selected compounds from the invention were tested as herbicides in the following way. ;Pre-emergence herbicidal activity test on several weeds. On the day before treatment, seeds of twelve different weed species are planted in loamy sandy soil in individual rows using one species per row the width of the vase. Weeds used green sedge (FT) (Setaria viridis), annual morning glory (ARG) (Lolium multiflorum), water grass (WG) (Echinochloa cmsgalli), wild reed (SCH) (Sorghum bicolor), wild oats (W0) (Avena fatua), broadleaf signal grass (BSO) (Brachiaria platyphylla), annual gorse (AMG) (Ipomoea lacunosa), sesbania hop (SESB) (Sesbania exaltata), velvet (VL) (Abutilon theophrasti), sickle pod (SP) ( Cassia obtusifolia), yellow nut (YNG) (Cyperus esculentus) and dicot (CB) (Xanthium sp.). Plant enough seeds to get about 20 to 40 seeds per row, after germination, depending on the size of the plants. ;Using an analytical balance, 37.5 mg of the compound to be tested is weighed onto a piece of glass paper for measurement. The paper and the compound are placed in a clean, wide-necked 60 ml bottle and dissolved in 45 ml of acetone or a similar solvent. 18 ml of this solution is transferred to a clean 60 ml wide-mouth bottle and diluted with 22 ml of a mixture of water and acetone (19:1) containing enough polyoxyethylene-sorbitan-monolaurate egator to achieve a final dilution of 0.5% (v/ c). The solution is then sprayed onto the seed bed on a lined spray table that is calibrated to deliver 748 1/ha. The application rate is 0.28 Kg/ha. After treatment, the vases are placed in a glass garden at a temperature of 21.1-26.7° C and irrigated by spraying. Two weeks after treatment, the degree of damage or control is determined by comparing it with untreated control plants of the same age. ;Record a damage estimate from 0 to 100% for each species as a percentage of control, where 0% means no damage and 100% represents complete control. ;The results of the test are shown in the following Table 15. ;[image] ;Test for herbicidal effect after emergence on several weeds. This test is performed identically to the test procedure in the pre-emergence herbicidal test, except that the seeds of the twelve weed species are planted 10-12 days before treatment. Also, irrigation of the treated vases is limited to the surface of the soil and not to the leaves of the plants being tested. ;The results of the post-emergence herbicidal activity test are listed in Table 16. ;[image] ;The line (-) indicates that no evaluation was performed. ;Empty space indicates that this type of weed was not in the test.;* Tested at 1.14 Kg/ha

The compounds of the present invention are useful as herbicides and can be applied in a variety of ways at early concentrations. In practice, the compounds defined here are formulated into herbicidal preparations by mixing, in herbicidally effective amounts, with carrier additives that are normally used to facilitate the dispersion of active ingredients in agricultural applications, while accepting the fact that the formulation and method of application of the toxicant can affect the activity of the material in given application.

Thus, these active herbicidal compounds can be formulated as relatively large particle size granules, as wettable powders, as emulsifying concentrates, as dusts, as solutions, or as several other well-known types of formulation, depending on the desired route of administration. Preferred formulations for pre-emergence herbicide applications are wettable powders, emulsifying concentrates and granules. These formulations can contain as little as 0.5% wt. up to as much as 95% wt. active ingredient. The herbicide effective amount depends on the nature of the seed or plants being controlled and the rate of application varies from about 0.05585 to about 11.17 Kg/ha, preferably from about 0.1117 to about 4.468 Kg/ha.

Wettable powders are in the form of finely divided particles that are easily dispersed in water or other dispersants. Wettable powder must be applied to the soil either as a dry powder or as a dispersion in water or another liquid.

Typical carriers for wettable powders include filler earth, kaolin clays, silica, and other easily wettable organic or inorganic diluents. Wettable powders are normally made to contain about 5% to about 95% by weight. active ingredient and usually also contain a small amount of wetting, dispersing or emulsifying agent to facilitate wetting and dispersing.

Emulsifying concentrates are homogeneous liquid preparations that can be dispersed in water or other dispersants, and may consist entirely of the active compound with a liquid or solid emulsifying agent, or may also contain some liquid carrier, such as xylene, heavy aromatic naphthalene, isophorone and other non-volatile organic solvents. For herbicidal application, these concentrates are dispersed in water or another liquid carrier and normally applied as a shower to the surface to be treated. The percentage by weight of the essential active ingredient may vary depending on the way the preparation is applied, but generally comprises about 0.5% to 95% by weight. of the active ingredient of the herbicidal preparation.

Granular formulations in which the toxicant is carried on relatively coarse particles are usually applied without dilution to the surface where vegetation suppression is desired. Typical carriers for granular formulations include sand, potting soil, betonite clays, vermiculite, perlite, and other organic and inorganic materials that absorb or can be coated with the toxicant. Granular formulations are normally made to contain about 5% to about 25% by weight. active ingredients and may include such surfactants as heavy aromatics, kerosene or other petroleum fractions, or vegetable oils; and/or adhesives such as dextrins, putty or synthetic resins.

Typical wetting, dispersing or emulsifying agents used in agricultural formulations include, for example, alkyl and alkylaryl sulfonates and sulfates and their sodium salts; polyhydroxyl alcohols; and other types of surfactants, many of which are commercially available. The surfactant, when used, normally comprises from 0.1% to 15% by weight. herbicide preparation.

Dusts, which are free-flowing mixtures of the active ingredient with such finely divided solids as talc, clays, flours, and other organic and inorganic solids that act as dispersants and carriers for the toxicant, are useful formulations for ground application.

Pastes, which are homogeneous suspensions of finely divided solid toxicants in a liquid carrier such as water or oil, are used for specific purposes. These formulations normally contain about 5%. up to about 95% wt. active ingredient, and may also contain small amounts of wetting, dispersing or emulsifying agents to facilitate dispersion. For application, pastes are normally diluted and applied as a shower to the surface to be affected.

Other useful formulations for herbicidal preparations include simple solutions of the active ingredient in some dispersant in which it is completely soluble at the desired concentration, such as acetone, alkylated naphthalenes, xylene, and other organic solvents. Preserized showers, typically aerosols, in which the active ingredient is dispersed in finely divided form as a result of evaporation of a low-boiling dispersant carrier solvent, such as Freons, may also be used.

Phytotoxic preparations from this invention are applied to plants in a conventional manner. Thus, dust and liquid preparations can be applied to the plant using powder dusters, brooms and hand sprayers and shower dusters. The preparation can also be applied from an airplane as a dust or shower because they are very effective in very low doses. To modify or control the growth or germinated seeds, as a typical example, dust and liquid preparations are applied to the soil by conventional methods and distributed in the soil to a depth of at least 1.27 cm below the soil surface. It is not necessary to mix phytotoxic preparations with pieces of soil, since these preparations can also be applied by simply spraying or pouring the surface of the soil. The phytotoxic preparations of this invention can also be applied by adding to the irrigation water supplied to the field to be treated. This application procedure allows the preparation to penetrate the soil when the water is adsorbed in it. Powder preparations, granular preparations or liquid formulations when applied to the soil surface can be distributed below the soil surface by such conventional means as digging, raking and mixing operations.

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When salts are used as an active ingredient in the herbicidal preparations of this invention, it is recommended to use salts that are agriculturally acceptable.

The phytotoxic preparations of this invention may also contain other additives, for example, fertilizers, other herbicides and other pesticides, which are used in addition to or in combination with any of the additives described above. Fertilizers used in combination with active ingredients include, for example, ammonium nitrate, carbamide and superphosphate.

The herbicidal compounds of this invention can be used in combination with other herbicidal compounds for a broader spectrum of undesirable vegetation control. Examples of other herbicidal compounds are as follows:

1. ANILIDS

Alachlor-2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide

Metolachlor-2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide

Propanyl-N-(3,4-dichlorophenyl)-propioamlide

2. TRIAZINES

Atrazine-2-chloro-4-(ethylamino)-6-(isotopylamino)-s-triazine Cyanazine-2-chloro-4-(1-cyano-1-methylethylamino)-6-ethylamino-s-triazine Metribuzin-4- amino-6-tert-butyl-3-(methylthio)-1,2,4-triazin-5/(4H)-one

3. THIOCARBAMATES

Molinate-S-ethyl-hexahydro-1H-azepine-1-carbothioate Butylate-S-ethyl-diisobutylthiocarbamate

4. UREA

Monuron-3-(p-chlorophenyl)-1,1"dimethylurea

Linuron-3-(3,4-dichlorophenyl)-1-methoxy-1-methylurea

5. TOLUIDINES

Trifluralm-alpha,alpha,alpha-trifluoro-2,6-dimethyl-N,N-dipropyl-p-toluidine

Pendimethalin-N-(1-ethylpropyl)-3,4-dimethyl-2,6-dimtrobenzenamine

6. HORMONES

2,4-D-(2,4-dichlorophenoxy)-acetic acid MCPA-(2-methyl-4-chlorophenoxy)-acetic acid

7. DIAZINES Bentazon-3-isopropyl-1H-2,3,1-benzothiadiazin-4(3H)-one,2,2-dioxide

Oxadiazon-2-tert-butyl-4-(2,4-dichloro-5-isopropoxyphenyl)-delta2-1,3,4-oxadiazolin-5-one

8. DIPHENYLETHERS

Acifluorophen-sodium-5-/2-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenzoate Fluazifop-butyl-(±)-butyl 2-/4/(5-(trifluoromethyl)-2-pyridinyl)-oxy/ phenoxy/propanoate Chloromethoxymethyl-2,4-dichlorophenyl-3-methoxy-4-triphenylether

9. IMIDAZOLINONES

Imazaquin-2-(4,5,-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl)-3-quinolm carboxylic acid

10. SULFONYLcarbamides

Bensulfuron methyl-methyl 2-(((((4,6-dimethoxypyrimidin-2-yl)-amino)-carbonyl)-amino)sulfonyl-1)methyl)benzoate

Chlorimuron ethyl-ethyl 2-(((((4-chloro-6-methylpyrimidin-2-yl)amino)carbonyl)amino)-sulfonyl)benzoate

11. DIFFERENT COMPOUNDS

Dimethasone-2-(2-chlorophenyl)methyl-4,4-dimethyl-3-isoxazolidmone

Norflurazon-4-chloro-5-(methylamino)-2-(alpha,alpha,alpha-trifluoro-m-tolyl)-3-(2H)-pyridazinone

Dalapone-2,2-dichloropropionic acid

Glyphosate-isopropylamine salt of N-(phosphonomethyl)glycine

Fenoxaprop-ethyl-(+)-ethyl-2,4-((6-chloro-2-benzoxazolyloxy)phenoxy)propanoate

Claims (24)

1. Compound of the structural formula [image] indicated by that X is oxygen or sulfur; R is chlorine or bromine R 1 is hydrogen or C 1 -C 4 alkyl; R 2 is hydrogen or C 1 -C 4 alkyl; R 3 is hydrogen or C 1 -C 4 alkyl; R4 is hydroxy, hydrogen or C1-C4 alkyl. R 3 and R 4 are jointly carbonyl (=0) provided that R 1 , R 2 , R 5 and R 6 are all C1-C4 alkyl; R5 is hydrogen or C1-C4 alkyl;, R 6 is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkylthio, or C 1 -C 4 alkylsulfonyl, provided that when R 6 is C 1 -C 4 alkylthio or C 1 -C 4 alkylsulfonyl, then R 3 and R 4 together are carbonyl R 7 is methyl or ethyl; and R 8 is (1) halogen, (2) nitro; or (3) RbSOn where n is an integer of 0 or 2; R 15 is (a) C 1 -C 3 alkyl; and their salts. 2. Compound according to claim 1, characterized in that R is chlorine or bromine; R 1 is hydrogen or methyl; R 2 is hydrogen or methyl, R 3 is hydrogen or methyl; R 4 is hydrogen or methyl or R 3 and R 4 together are carbonyl, provided that R 1 , R 2 , R 5 and R 6 are all methyl; R 5 is hydrogen or methyl; R 6 is hydrogen, methyl, methylthio or methylsulfonyl, provided that when R 6 is methylyl methylsulfonyl, then R 3 and R 4 are not shared by carbonyl; R 7 is methyl or ethyl; R8 is hydrogen chlorine, bromine, nitro or RbSO2 where R5 is C1-C3 alkyl, 3. Compound according to claim 2, characterized in that R is bromine, R1 is methyl, R2 is methyl, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is bromine and X is hydrogen. . 4. A compound according to claim 2, characterized in that R is bromine, R1 is hydrogen, R2 is hydrogen, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is n-C3H7SO2 and X is oxygen. . 5. The compound of claim 2, characterized in that R is chlorine, R1 is hydrogen, R2 is hydrogen, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is C2H5SO2 and X is oxygen. . and 6. The compound of claim 2, characterized in that R is chlorine, R1 is hydrogen, R2 is hydrogen, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is n-C3H7SO2 and X is oxygen 7. The compound of claim 2, characterized in that R is bromine, R1 is methyl, R2 is methyl, R3 and R4 together are carbonyl, R5 is methyl, R6 is methyl, R7 is methyl, R8 is bromine and X is sulfur. 8. The compound of claim 2, characterized in that R is bromine, R1 is hydrogen, R2 is hydrogen, R3 is methyl, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is C2H5SO2 and X is oxygen. . 9. Procedure for controlling undesirable vegetation, indicated by the fact that it includes application on the surface where it is desired to control the herbicidally effective amount of compounds having the structural formula: [image] in which: X is oxygen or sulfur; R is chlorine or bromine; R 1 is hydrogen or C 1 -C 4 alkyl; R 2 is hydrogen or C 1 -C 4 alkyl; R 3 is hydrogen or C 1 -C 4 alkyl; R 4 is hydroxy, hydrogen or C 1 -C 4 alkyl; or R 3 and R 4 together are carbonyl (=0) provided that R 1 , R 2 , R 5 and R 6 all C1-C4 alkyl R 5 is hydrogen or C 1 -C 4 alkyl; R 6 is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkylthio or C 1 -C 4 alkylsulfonyl, provided that when R 6 is C 1 -C 4 alkylthio or C 1 -C 4 alkylsulfonyl, then R 3 and R 4 are not together carbonyl R 7 is methyl or ethyl; and R 8 is (1) halogen; (2) nitro; or (3) RbSOn- where n is an integer 0 or 2; and R 15 is (a) C 1 -C 3 alkyl; and its salts. 10. The method of claim 9, characterized in that R is chlorine or bromine; R 1 is hydrogen or methyl; R 2 is hydrogen or methyl; R 3 is hydrogen or methyl; R 4 is hydrogen or methyl or R 3 and R 4 together are carbonyl provided R 1 , R 2 , R 5 and R 6 are all methyl; R 5 is hydrogen or methyl; R 6 is hydrogen, methyl, methylthio or methylsulfonyl provided that when R 6 is methyl or methylsulfonyl, then R 3 and R 4 together are not carbonyl; R 7 is methyl or ethyl; R8 is hydrogen, chlorine, bromine, nitro or RbSO2 where Rb is C1-C3 alkyl. 11. The method of claim 10, characterized in that R is bromine, R1 is methyl, R2 is methyl, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is bromine and X is oxygen. 12. The method of claim 10, characterized in that R is bromine, R1 is hydrogen, R2 is hydrogen, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is n-C2H7SO2 and X is oxygen. 13. The process of claim 10, characterized in that R is chlorine, R1 is hydrogen, R2 is hydrogen, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is C2H5SO2 and X is oxygen. . 14. The method according to claim 10, characterized in that R is chlorine, R1 is hydrogen, R2 is hydrogen, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is n-C3H7SO2 and X is oxygen. 15. The process of claim 10, characterized in that R is bromine, R1 is methyl, R2 is methyl, R3 and R4 are together carbonyl, R5 is methyl, R6 is methyl, R7 is methyl, R8 is bromine and X is sulfur. 16. The process of claim 10, characterized in that R is bromine, R1 is hydrogen, R2 is hydrogen, R3 is methyl, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is C2H5SO2 and X is oxygen. . 17. Herbicidal preparation, characterized by the fact that it includes a herbicidally effective amount of a compound having the structural formula: [image] in which: X oxygen or sulfur; R is chlorine or bromine; R 1 is hydrogen or C 1 -C 4 alkyl; R 2 is hydrogen or C 1 -C 4 alkyl; R 3 is hydrogen or C 1 -C 4 alkyl; R 4 is hydroxy, hydrogen or C 1 -C 4 alkyl; or R 3 and R 4 together are carbonyl (=O) provided that all R 1 , R 2 , R 5 and R6 is all alkyl; R 5 is hydrogen or C 1 -C 4 alkyl; R 6 is hydrogen, C 1 -C 4 alkyl, C 1 -C 4 alkylthio or C 1 -C 4 alkylsulfonyl, provided that when R 6 is C 1 -C 4 alkylthio or C 1 -C 4 alkylsulfonyl, then R 3 and R 4 together are not carbonyl; R 7 is methyl or ethyl; and R 8 is (1) halogen; (2) nitro; or (3) RbSOn- where n is an integer 0 or 2; and Rb is (a) C1-C3 alkyl; and its salt and an inert carrier for this substance. 18. The herbicidal preparation from claim 17, characterized in that R is chlorine or bromine; R 1 is hydrogen or methyl; R 2 is hydrogen or methyl; R 3 is hydrogen or methyl; R 4 is hydrogen or methyl or R 3 and R 4 together are carbonyl provided that R 1 , R 2 , R 5 and R 6 are all methyl; R 5 is hydrogen or methyl; R6 is hydrogen, methyl, methylthio or provided that when R6 is C1-C4 alkylthio or C1-C4 alkylsulfonyl, then R3 and R4 are not together carbonyl; R7 is methyl or ethyl: R8 is hydrogen, chlorine, bromine, nitro or RbSO2 where R5 is C1-C3 alkyl. 19. The herbicidal preparation according to claim 18, characterized in that R is bromine, R1 is methyl, R2 is methyl, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is bromine and X is oxygen. 20. The herbicidal preparation according to claim 18, characterized in that R is bromine, R1 is hydrogen, R2 is hydrogen, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is n-C3H7SO2 and X is oxygen. 21. The herbicidal preparation according to claim 18, characterized in that R is chlorine, R1 is hydrogen, R2 is hydrogen, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is C2H5SO2 and X is oxygen. 22. Herbicidal preparation according to claim 18, characterized in that R is chlorine, R1 is hydrogen, R2 is hydrogen, R3 is hydrogen, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is n-C3H5SO2 and X is oxygen. 23. The herbicidal preparation according to claim 18, characterized in that R is bromine, R1 is methyl, R2 is methyl, R3 and R4 together are carbonyl, R5 is methyl, R6 is methyl, R7 is methyl, R8 is bromine and X is sulfur. 24. The herbicidal preparation according to claim 18, characterized in that R is bromine, R1 is hydrogen, R2 is hydrogen, R3 is methyl, R4 is hydrogen, R5 is hydrogen, R6 is hydrogen, R7 is methyl, R8 is C2H5SO2 and X is oxygen.