ESTERS OF 2-BROMO-4-METHYLIMIDAZOLE-5-CARBOXYLIC ACID

Abstract: A compound having the structural formula wherein R is alkyl, cycloalkyl, cycloalkylalkyl, alkenyl, benzyl or substituted benzyl.

Description: ESTERS OF 2-BROtIO-4-t.1ETHYLIllIDAZOLE-5-CARBOXYLIC ACID This invention relates to imidazole esters of use as herbicides. Compounds having the structural formula: EMI1.1 wherein R is hydrogen, alkyl or substituted alkyl and Y is hydrogen, alkyl, substituted alkyl, halogen, cyano or nitro are described in U.S. Patent No. 3,501,286 as being herbicides. A compound of the formula: EMI1.2 is taught by Pyman and Timmis, J. Chem. Soc., pp. 494498 (1923). However, no utility for this compound is taught other than its use as an intermediate in the preparation of pharmaceuticals. Description of the Invention This invention relates to esters of 2-bromo-4methylimidazole-5-carboxylic acid as herbicides. The novel compounds of this invention have the following structural formula: EMI1.3 wherein R is methyl or C3-C10 alkyl, preferably C3-C6 alkyl, more preferably C3-C5 alkyl, most preferably isopropyl, isobutyl, isopentyl, or sec-pentyl; C3-C8 cycloalkyl, preferably C4-C6 cycloalkyl, more preferably cyclopentyl or cyclohexyl; C3-Cg cycloalkylalkyl wherein the alkyl has 2 to 8 carbon atoms, preferably cyclopropylmethyl or cyclopentylmethyl; C2 C10 alkenyl, preferably allyl or 2-methyl-3-butenyl-1; C5-Cg cycloalkenyl; benzyl or mono- or di-substituted benzyl wherein the substituents are C1-C4 alkyl, halogen, nitro or C1-C4 haloalkyl. More preferably R is C3-C6 alkyl. The compound where R is ethyl is known, however, its use as an herhicide is novel. In the above description of the compounds of this invention alkyl includes both straight and branched configurations; for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl, the amyls, the hexyls, the heptyls, the nonyls and the decyls. The compounds of this invention are active herbicides of a general type. That is, they are berbicidally effective against a wide range of plant specides. The method of controlling undesirable vegetation of the present invention ccmprises applying an herbicidaily effective amount of the above-described compounds to the area where control is desired. The compounds of the present invention can be prepared by the following general method. EMI2.1 wherein R is as defined. and TEC is a transesterification caLalyst such as Ti(O-alkyl)4, preferably Ti(isobutoxy)4. The compounds of this invention can have the following two structural forouiae because of tautomerism, that is, the proton on the imidazole nitrogen can reside on either nitrogen and is reasonably labile. Strucual formula I is the tautomer Which is believed to predominate in the solid state since the infrared spectra show longer-wave-length car- bonyl bands compared to ordinary esters. This fact suggests hydrogen bonding is possible only in the tautomer I. EMI3.1 Both tautomers I and II are believed to be in mobile equilibriun in solutions or in the liquid state. The e proton on tautomers I and II is acidic and can be removed by any base to give a salt having an anion of the following two resonsance forms: EMI3.2 Examples of cat ions of these bases can be an inorganic cation such as Na+, Kt, Ca++, Na4+ or it can be an organic cation such as hydro carbyl-sstituted ammonium, sul foniun, or phosphonium. These salts are stable compounds and can be isolated. They are also herbicidally active. The imidazoles of the invention are also basic. The unprotonated nitrogen atan of tautaner Ia or IIa can be protonated by an acid, preferably an inorganic acid. Illustrative inorganic acids are hydrochloric and hydrobranic, sulfuric, phosphoric and acetic. These salts are also herbicidal. The salts can be conventionally prepared by reacting at least a mole amount of a lexis acid or a Lewis base with the ester. Preferably, the reaction is run in a solvent for the ester with heating, if necessary. The prepared salt is recovered fran the reaction mixture by conventional techniques. In general, the salts are not as herbicidally active as the parent compound. Generally, at least one mole of the alcohol is used for the reaction with the ethyl ester to prepare the imidazoles. Preferably, a slight mole excess of the alcohol is used. The reaction mixture is refluxed until completin of the reaction. The reaction product is recovered by removing the volatile materials. Atmospheric, subatmospheric Cr superstmospheric pressures can be used, depending on the boiling point of the solvent used. Ethanol is conventiently stripped at elevated temper- atures and reduced pressure. The reaction product is worked up by conventional techniques. The following example teaches the synthesis of a representative compound of this invention. E2 E I Isopropyl ester of 2-Bromo-4-methyl-5-imidazolecarboxylic acid EMI4.1 6.4 grams (g), 0.027 mole of the ethyl ester of 2-bromo-4- methyl-5-imidazole carboxylic acid, 70 cubic centimeters (cc) isopropenol, and 6 drops tetraisobutyl titanate were refluxed under a nitrogen atoms where for ten days. The reaction mixture was stripped to 90 C and 1 mm kg causing crystallization. The crystals were filtered and recrystal1izad frail isopropaol to yield 3.4 g of the desired product, a white crystalline solid, m.p. 193.5-194.5. The structure 5 confirmed by nuclear magnetic resonance and infrared spectroscopy. SAMPLE II EMI5.1 To 4.0 g (0.017 mole) of the ethyl ester of 2-tromo-4-methyl-5- imidazolecarboxyl ic acid is added dropwise 4.0 g (0.4 mole) of hexamethyl eneimine. The e mixture was stirred at 230C for 2 hours, then stripped to 40 C and 2 mm Hg, causing crystallization of the desired product, a white crystalline solid, m.p. 94-94.5 C. The structure was confirmed by IR and ÚHNMR analyses. The e following is a table of certain selected compounds that are preparable according to the procedure described herein. Compound numbers are assigned to each compound and are used throughout the remainder of the application. TABLE I EMI6.1 r25 Number R or m.p. C 1 ethyl light yellow solid 2 i-propyl 193.5-194.5 3 n-butyl glassy solid 4 sec-butyl 140-141 5 i-butyl 111.5-112.5 6 n-hexyl semi-solid 7 n-octyl 1.5136 8 n-decyl 1.4999 9 3-methylbutyl glassy solid 10 cyclohexyl 51-53.5 11 cyclopentyl 173-174.5 12 n-propyl 108.5-110.5 13 1-methylbutyl 119-120 14 1-ethylpropyl 178-180 15 n-pentyl 93-94.5 16 1,3-dimethylbutyl 146-146.5 17 methyl 145.5-147 18 tkutyl golden oil 19 cyclopropylmethyl yellow oil 20 2,2-dimethylpropyl dark oil 21 1-methyl-3-propenyl golden oil 22 cyclopentylmethyl golden oil 23 sodium salt of Compound No. 19 24 hexamethylene imine salot of Compound No. 2 117-119 25 tetra-n-butyl amonium salt of Compound No. 2 semi-solid 26 sodium salt of Compound No. 2 dec. 255 27 hexamethylene imine salt of Compound No. 1 94-94.5 Herbicidal Screening Tests As previously mentioned, the herein described campounds produced in the above-described manner are phytotoxic compounds which are useful and valuable in controlling various plant species. Selected compounds of this invention were tested as herbicides in the following manner. Pre-emergence herbicide test. On the day preceding treatment, seeds of eight different weed species are planted in loamy sand soil in individual rows using one species per row across the width of a flat. The seeds used are green foxtail (FT) (Setaria viridis), watergrass (wig) (Echinochloa crusgalli), wild oat (WO) (Avena fatua), annual morningglory (AMG) (Ipomoea lacunosa), velvetleaf (VL) (Abutilon theophrasti), Indian mustard (MD) (Brassica juncea), curly dock (CD) (Rumex crispus), and yellow nutsedge (YNG) (Cyperus esculentus). Ample seeds are planted to give about 20 to 40 seedlings per row, after emergence, depending upon the size of the plants. Using an analytical balance, 600 milligrams (mg) of the compound to be tested are weighed out on a piece of glassine weighing paper. The paper and compound are placed in a 60 milliliter (ml) wide-mouth clear bottle and dissolved in 45 ml of acetone or substituted solvent. Eighteen ml of this solution are transferred to a 60 ml wide-msuth clear bottle and diluted with 22 ml of a water and acetone mixture (19:1) containing enough polyoxyethylene sorbitan mcnolaurate emulsifier to give a final solution of 0.5% (v/v). The solution is then sprayed on a seeded flat on a linear spray table calibrated to deliver 80 gallons per acre (748 L/ha). The application rate is 4 lb/acre (4.48 Eg/ha). After treatment, the flats are placed in the greenhouse at a temperature of 70 to 80 F and watered by sprinkling. Two weeks after treatment, the degree of injury or control is determined by caparison with untreated check plants of the same age. The injury rating from 0 to 100% is recorded for each species as percent control with 0% representing no injury and 100% representing ocoplete control. The results of the tests are shown in the following Table II. TABLE II Pre-Emergence Herbicidal Activity Application Rate - 4.48 kg/ha No. FT WG WO AMG VL MD CD YNG 1 10 20 20 20 30 60 20 0 2 100 100 100 100 100 100 100 20 3 0 20 0 35 0 20 90 0 4 100 100 50 90 100 100 90 0 5 20 20 20 10 10 10 100 0 6 0 0 0 0 0 0 0 0 7 80 40 20 0 0 0 0 0 8 0 0 0 0 0 0 0 0 9 0 0 0 0 0 0 0 0 10 0 0 0 0 0 0 0 0 11 0 20 0 40 70 60 60 0 12 10 30 10 20 10 30 60 0 13 100 80 80 80 100 100 100 0 14 100 100 90 90 100 100 100 0 15 0 0 0 0 0 0 0 0 16 0 0 0 0 0 0 0 0 17 0 0 0 0 0 0 0 0 18 100 90 45 100 100 100 80 0 19 20 20 0 60 60 60 80 0 20 0 0 0 30 100 100 0 0 21 80 80 40 60 90 90 60 0 22 0 0 0 0 0 0 0 0 23 0 0 0 80 80 80 0 0 24 90 70 20 60 85 60 80 0 25 40 60 10 20 30 40 60 0 26 80 65 10 40 80 85 85 0 27 20 40 20 50 10 90 90 0 Post-Etlnsnce Herbicide Test: This test is conducted in an identical manner to the testing procedure for the pre-emergence herbicide test, except the seeds of the eight different weed species are planted 10-12 days before treatment. Also, watering of the treated flats is coil- fined to the soil surface and not to the foliage of the sprouted plants. The results of the post-emergence herbicide test are reported in Table III. TABLE III Post-Emergence Herbicidal Activity Application Rate - 4.48 kg/ha wd. No. FT WG WO AMG VL MD CD YNG 1 85 85 85 100 100 100 100 0 2 100 100 100 100 100 100 100 40 3 100 100 100 95 100 100 100 0 4 100 100 100 100 100 100 100 10 5 100 60 60 80 100 100 100 0 6 60 20 20 80 80 90 80 0 7 80 40 20 0 0 80 0 0 8 0 0 0 10 90 90 30 0 9 30 20 10 30 40 40 50 0 10 100 60 90 40 100 100 100 0 11 100 60 80 85 90 95 100 0 12 40 20 10 60 80 90 80 0 13 100 80 90 100 100 100 100 30 14 100 100 100 80 100 100 100 10 15 90 60 60 60 80 60 90 0 16 80 80 60 40 80 80 90 10 17 0 0 0 40 50 60 20 0 18 100 100 100 90 100 100 100 0 19 0 0 0 100 100 100 25 0 20 100 60 30 85 100 100 0 0 21 60 60 60 80 100 100 60 0 22 25 30 30 0. - 20 0 0 23 100 80 80 85 100 100 0 0 24 100 60 60 80 100 100 100 0 25 20 0 0 80 90 95 90 0 26 100 60 85 85 90 95 100 0 27 0 0 40 100 100 98 100 5 - = Not tested. The compound of the present invention are useful as herbicides, and can be applied in a variety of ways at various concentrations. In practice, the compounds herein defined are formulated into herbicidal compositions, by admixture, in herbicidally effective amounts, with the adjuvants and carriers nrrmally employed for facilitating the dispersion of active ingredients for agricultural applications, reconizing the fact that the formulation and mode of application of a toxicant may affect the activity of the materials in a given application. Thus, these active herbicidal nçds may be formulated as granules of relatively large particle size, as wettable powders, as emulsifiable concentrates, as powdery dusts, as solutions or as any of several other known types of formulations, depending upon the desired mode of application. Preferred formulationS for pre-emergence herbicidal applications are wettable powders, alsifiable concentrates and granules. These formulations may contain as little as about 0.5% to as much as about 95% or mare by weight of active ingredient. A herbicidally effective amount depends upon the nature of the seeds or plants to be controlled and the rate of application varies fran about 0.05 to approximately 25 pourds per acre, preferably fran about 0.1 to about 10 pounds per acre. Table powders are in the form of finely divided particles which disperse readily in water or other dispersants. The wettable powder is ultimately applied to the soil either as a dry dust ar as a dispersion in water or other liquid. Typical carriers for wettable powders include fuller's earth, kaolin clays, silicas and other readily wet organic or inorganic diluents. Table pokers normally are prepared to contain about 5% to about 95% of the active ingredient and usually also contain a small amount of wetting, dispersing, or emulsifying agent to facilitate wetting and dispersion. Enisifiable concentrates are homogeneous liquid capositions which are dispersible in water or other dispersant, ard may consist entirely of the active xvpound with a liquid or solid emulsifying agent, or may also contain a liquid carrier, such as xylene, heavy aromatic naph- tha, isophorone and other non-volatile organic solvents. Bor herbicidal application, these concentrates are dispersed in water or other liquid carrier and normally applied as a spray to the area to be treated. The percentage by weight of the essential active ingredient may vary according to the manner in which the composition is to be applied, but in general comprises about 0.5% to 95% of active ingredient by weight of the herbicidal composition. Granular formulations therein the toxicant is carried on relatively coarse particles, are usually applied without dilution to the area in which suppression of vegetation is desired. Typical carriers for granular formulations include sand, fuller's earth, bentonite clays, vermiculite, perlite and other organic or inorganic materials which absorb or zilch may be coated with the toxicant. Granular formulations normally are prepared to contain about 5% to about 25% of active ingredients which may include surface-active agents such as wetting agents, dispersing agents or emulsifiers; oil such as heavy aranatic naphthas, kerosene or other petro letiti fractions, or vegetable oils; and/or stickers such as dextrins, glue or synthetic resins. Typical wetting, dispersing or emulsifying agents used in agricultural formulations include, for example, the alkyl and allylaryl sulfonates and sulfates and their sodium salts; polyhydroxy alcohols; and other types of surface-active agents, many of which are available in aannerce. The surface-active agent, when used, normally conprises fran 0.1% to 15% by weight of the herbicidal composition. Dusts, iich are free-flowing admixtures of the active ingredient with finely divided solids such as talc, clays, flours and other organic and inorganic solids which act as dispersants and carriers for the tox icant, are useful formulations for soil- incorporating application. Pastes, which are hanogeneous suspensions of a finely divided solid toxicant in a liquid carrier such as water or oil, are employed for specific purposes. These formulations normally contain about 5% to about 95% of active ingredient by weight, and may also contain small amounts of a wetting, dispersing or emulsifying agent to facilitate dispersion. For application, the pastes are normally diluted and applied as a spray to the area to be affected. Other useful formulations for herbicidal applications include single solutions of the active ingredient in a dispersant in which it is completely soluble at the desired concentration, such as acetone, alkyl ated naahthalenes, xylene and other organic solvents. Pressurized sprays, typically aerosols, wherein the active ingredient is dispersed in finelydivided form as a result of vaporization of a low boiling dispersant solvent carrier, such as the Peons, may also be used. The phytotoxic compositions of this invention are applied to the plants in the conventional manner. Thus, the dust and liquid compositions can be applied to the plant by the use of powder-dusters, boan and hand sprayers and spray dusters. The compositions can also be applied from airplanes as a dust or a spray because they are effective in very low dosages. In order to modify or control growth of germinating seeds or emerging seedlings, as a typical exawle, the dust and liquid compositions are applied to the soil according to conventional methods and are distributed in the soil to a depth of at least 1/2 inch below the soil surface, It is not necessary that the phytotoxic compositions be admixed with the soil particles since these compositions can also be applied merely by spraying or sprinkling the surface of the soil. The phytotoxic composi- tions of this iveention can also be applied by addition to irrigation water sullied to the field to be treated. This method of application permits the penetration of the compositions into the soil as the aster is absorbed therein. Dust ositions, granular compositions or liquid formulations applied to the surface of the soil can be distributed below the surface of the soil by conventional means such as discing, dragging or mixing operations. The phytotoxic compositions of this invention can also contain other additaments, for exaue, fertilizers and other herbicides, pesticides and the like, used as adjwant or in combination with any of the above-described adjuvants. Other phytotoxic compounds useful in combination with the above-described expounds include, for example, 2,4-dichlorophenoxyacetic acids, 2,4,5-trichlorophenoxyacetic acid, 2-methyl-4-chlorophenoxyacetic acid and the salts, esters and amides thereof, triazine derivatives, sudi as 2,4-bis(3-methoxypropylamino)-6-methylthio-s-tria- zine, 2-chloro-4-ethylamino-6-isopropylamino-s-triazine, and 2-ethylamino-4-isopropyl-amino-6-methyl-mercapto-s-triazine, urea derivatives, such as 3-(3,5-dichlorophenyl)-l,l-dimethylurea and 3-(p-chloro- phenyl)-l,l-dimethylurea; and acetamides such as N,N-diallyl-&alpha;-chloro- acetamide, and the like; benzoic acids such as 3-amino-2, 5-dichlorobenzoic acid; thiocarbamates such as S-propyl N,N-dipropylthiocarbamate, S-ethyl N,N-dipropylthiocarbamate, S-ethyl cyclohexylethylthiocarbamate, S-ethyl hexahydro-1Hazepine-1-carbothioate and the like; anilines such as 4-(methylsulfonyl)-2,6-dihydro-N,N-substituted aniline, 4-trifluoromethyl2,6-dinitrio-N,N-di-n-propyl aniline, 4-trifluoromethyl-2,6-dinitro-Nethyl-N-butyl aniline, 2-[4-(2,4-dichlorophenoxy)phenoxy]propanoic acid, 2-[1-(ethoxyimino)butyl]5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexene-1one, (#)-butyl-2[4-[(5-trifluoromethyl)-2-pyridinyl)oxy]phenoxy]propanate, sodium 5- [2-chloro-4-(trifluoromethyl)phenoxy] -2-nitrobenzoate, 3-isu- propyl-1H-2,1,3-benzothiadiazine-4(3H)-one-2,2-dioxide, and 4-amino-6tert-butyl-3-(methylthio)-as-triazin-5(4H)-one or (4-amino-6-(1,1-dimethylethyl)-3(methylthio)-1,2,4-triazin-5(4H)-one). Fertilizers useful in combination with the active ingredients include, for example, ammonium nitrate, urea and superEhoephate. Other useful additaments include materials in which plant organists take root and grow such as compost, manure, humus, sand, and the like.

Claims: CLAIMS: 1. A compound having the structural formula EMI14.1 wherein R is methyl or C3-C10 alkyl; C3-C8 cycloalkyl; C3-C8 cycloalkylalkyl wherein the alkyl has 2 to 8 carbon atoms; allyl or 2-methyl-3- butenyl-1; C5-C8 cycloalkyl; benzyl or mono- or di-substituted benzyl wherein the substituent is C1-C4 alkyl, halogen, nitro or C1-C4 haloalkyl; and salts thereof. 2. A compound of the fontilla EMI14.2 wherein R is methyl or C3---C5 alkyl or C4-C6 cycloalkyl and salts thereof. 3. The compound of Claim 2 wherein R is C3-C5 alkyl. 4. The compound of Claim 3 wherein R is isopracyl, n--butyl, t-butyl, isobutyl, 1-methylbutyl or methyl propyl. 5. The compound of Claim 3 wherein R is isopropyl. 6. The compound of Claim 2 wherein R is isobutyl. 7. The copound of Claim 2 wherein R is n-butyl. 8. The ç of Claim 2 wherein R is t-butyl. 9. The compound of Claim 2 wherein R is 1-methylbutyl. 10. The compound of Claim 2 wherein R is 1-ethylpropyl. 11. The method of controlling undesirable vegetation comprising applying to the area where control is desired an herbicidally effective amount of a compound having the structural formula EMI15.1 wherein R is C1-C10 alkyl; C3-Cg cycloalkyl; C3-C8 cycloalkylalkyl wherein the alkyl has 2 to 8 carbon atans; allyl or 2-methyl-3-butenyl-1; C5-C8 cycloalkyl; benzyl or mono- or di-substituted benzyl wherein the substituent is C1-c4 alkyl, halogen, nitro or C1-C4 haloalkyl; and salts thereof. 12. The method of Claim 11 wherein R is C3-C5 alkyl or C4-Cs cycloalkyl and salts thereof. 13. The method of Claim 12 wherein R is C36 alkyl. 14. The method of Claim 13 wherein R is isopropyl, n-butyl, t-butyl, iso-butyl, 1-methylbutyl or methylpropyl. 15. The method of Claim 13 wherein R is isopropyl. 16. The method of Claim 13 wherein R is isobutyl. 17. The method of Claim 13 wherein R is n-butyl. 18. The method of Claim 13 wherein R is t-butyl. 19. The method of Claim 13 wherein R is 1-methylbutyl. 20. The method of Claim 13 wherein R is 1-ethyipropyl. 21. A herbicidal composition comprising a herbicidally active amount of a compound as defined in any of claims 1 to 20. 1. A method of controlling undesirable vegetation comprising applying to the area where control is desired an herbicidally effective amount of a compound having the structural formula: EMI16.1 wherein R is C1- C10 alkyl; C3-C8 cycloalkyl; C -C cycloalkylalkyl wherein the alkyl has 2 to 8 carbon atoms; allyl or 2-methyl-3-butenyl-l; C5-C8 cycloalkyl; benzyl or mono- or di-substituted benzyl wherein the substituent is Cl-C4 alkyl, halogen, nitro or C1-C4 haloalkyl; and salts thereof. 2. A method as claimed in claim 1 characterized in that those compounds which are used are those in which R is C3-C6 alkyl. 3. A method as claimed in claim 1 characterized in that those compounds which are used are those in which R is C3-C5 alkyl or C4-C5 cycloalkyl and salts thereof. 4. A method as claimed in claim 2 characterized in that R is isopropyl, n-butyl, t-butyl, iso-butyl, l-methylbutyl or methylpropyl. 5. A method as claimed in claim 2 characterized in that R is isopropyl. 6. A method as claimed in claim 2 characterised in that R is isobutyl. 7. A method as claimed in claim 2 characterized in that R is n-butyl. 8. A method as claimed in claim 2 characterised in that R is t-butyl. 9. A method as claimed in claim 2 characterized in that R is l-methylbutyl. 10. A method as claimed in claim 2 characterized in that R is l-ethylpropyl. 11. A method as claimed in claim 1 characterized in that the compounds used have the formula: EMI17.1 wherein R is methyl or C3-Cl0 alkyl; C3-C8 cycloalkyl; C3-C8 cycloalkylalkyl wherein the alkyl has 2 to 8 carbon atoms; allyl or 2-methyl-3-butenyl-l; C5-C8 cycloalkyl; benzyl or mono- or di-substituted benzyl wherein the substituent is Cl-C4 alkyl, halogen, nitro or Cl-C4 haloalkyl; and salts thereof. 12. A herbicidal composition comprising a herbicidally active amount of a compound as defined in any of claims 1 to 11 together with an adjuvant. 13. A process for the preparation of compounds as defined in any of claims 1 to 11 characterized in that one reacts a compound of the formula: EMI17.2 with a compound of the formula: ROH in which R has the meaning defined in any of claims 1 to 11 in the presence of a transesterification catalyst, if desired with subsequent conversion to a salt thereof. 14. A process for the preparation of salts of the compounds as defined in any of claims l to 10 characterized in that a Lewis acid or a Lewis base is reacted with the ester. 15. A process as claimed in claim 13 or claim 14 in which the compound of formula ROH is one in which R has the meaning given in claim 11.

Inventors: BAYER, ARTHUR CRAIG
Applicants: STAUFFER CHEMICAL COMPANY
Application year: 1984
Main classification: C07D233
IPC codes: A01N43, C07D233