HERBICIDAL QUINOXALINYL ETHERS

Abstract: Compounds of the formula where X is Cl, F or Br; and R is CH₃ or CH₂CH₃ exhibit potent selective herbicidal activity, especially against Echinochloa spp in paddy rice. The novel compounds may be made e.g. by condensing the appropriate 2-chloro-6-haloquinoxaline with an alkali metal salt of methoxy- or ethoxyethoxyethyl 2-(4-hydroxphenoxy) propanoate.

Description: Title HERBICIDAL QUINOXALINYL ETHERS Background of the Invention This invention relates to quinoxalinyl ethers which are useful as herbicides. These compounds are especially useful as selective weed control agents in various broadleaf crops and in paddy rice, providing excellent control of barnyardgrass (Echinochloa spp). DE-A-30 04 770 discloses quinoxaline and quinoline compounds of the formula EMI1.1 wherein A is CH or N; X is halogen; n is 0, 1 or 2; R is H or lower alkyl; R2 is OH, alkoxy, OM, NR3R4, lower alkenyloxy, benzyloxy, alkoxyalkoxy, phenoxy, cyclohexyloxy, haloalkoxy, alkynyloxy or cyanoalkoxy; M is an organic or inorganic cation; R3 is.H or lower alkyl; and is is H or lower alkyl. EP-A-23,785 discloses herbicidal quinoxaline compounds of the general formula: EMI2.1 where A, 8, D, E, J, U and V may be halogen, among others; R1 and R2 may be H or C1-C6 alkyl, among others; W may be COG and G may be C1-C10 alkoxy substituted with-C1-C6 alkoxy. Neither of these publications disclose the ethoxyethoxyethyl and methoxyethoxyethyl compounds disclosed and claimed herein. Our EP-A-42,750, unpublished at the priority date of the present Application, discloses a mixture of 2-ethoxyethoxyethyl 2-[ [4- (6-chloroquinoxalin-2-yloxy) (6-chloroquinoxa lin-2-yloxy) phenoxyipropanoate with the corresponding 7-chloro isomer. The mixture showed selective herbicidal activity. Summary of the Invention It has been found that the novel compounds of Formula (I) are useful as herbicides, especially for controlling weeds such as barnyardgrass EMI3.1 where X is C1, F or Br; and R is CH3 or CH2CH3. Specifically preferred for its. outstanding utility is the compound 2-ethoxyethoxyethyl-2-t4-.(6-chloro- quinoxalin-2-yloxy) phenoxy)propanoate. This invention therefore relates to compounds of Formula I, herbicidal compositions containing them and methods of using them to control weeds. It should be noted that the 6-haloquinoxaline derivatives of the present invention exhibit far superior herbicidal activity to the 6 or 7-haloquinoxaline isomer mixtures disclosed in our EP-A-42,750. For example, the activity of 2 ethOxyethOxyethyl-2-[4-6-chloroquinox'alin-2-ylOxaz)phenoxy] propanoate for pre-emergence control of weeds such as bluegrass,'dallisgrass, giant foxtail and wild oats is about twice that of the 6 or 7-chloro isomeric mixture. Moreover the compounds of formula (I) in general are surprisingly effective herbicides by comparison with some compounds of closely related structure. For example, the selective of these compounds to paddy rice at rates of application which give excellent control of Echinochloa spp. iS a valuable and unexpected feature. Detailed Description Synthesis The various compounds of Formula I can'be prepared by one of the following methods. Method A 'The compounds (I) can be prepared by combining, preferably in equimolar amounts, a 2-chloro-6-haloquinoxaline (II) and the alkali metal salt of'methoxy or ethoxyethoxyethyl 2-(4-hydroxyphenoxy)propanoate (III) as illustrated below: EMI4.1 where X = Cl, F or Br; and R = CH3 or C2H5. Suitable solvents for the reaction include methyl ethyl ketone, dimethylformamide, dimethylsulfoxide and -diglyme. -The reaction is-preferably carried out at temperatures between 25 and about 1300C. The 2-chlore-6-haloquinoxalines (II) used in this invention can be prepared by methods known in the art.' Glyoxylic acid or an alkyl ester of glyoxylic acid is combined with a halosubstituted o-phenylenediamine in ethanol, to yield a mixture of 6- and 7-halo 2-hydvoxyquinoxalines, as described in J.A.C.S. 71, 6, (1949). The mixture of the 2-hydroxyquinoxalines is treated with phosphorous oxychloride as described in ?. Chem. Soc.,. 519 (1948) or Bull. Soc. Chem. France, 356 (1963), to give the desired 2-chloro-6-haloquinoxaline and its 7-isomer. The reader is referred to the above cited references for further information. The two isomers can be separated at tis stage by methods known in the art such as chromatography or crystallization. The methoxy or ethoxyethoxyethyl 2-(4-hydroxyphenoxy)propionates (III) can be prepared by the alkylation of Hz4-benzyloxyphenol with the alkyl bromopropionate, followed by catalytic hydrogenation of the product in the presence of palladium over carbon to yield the desired product (III). Method B The esters (I) can also be synthesized by the reaction of the appropriate acid chloride (IV) with 2-(2-methoxyethoxy)ethanol or with 2-(2-ethoxyethoxy)ethanol in a suitable solvent such as tetrahydrofuran in the presence of an acid acceptor as ou.tlined below: EMI5.1 The requisite acid chlorides (IV) can be prepared via the acid from the corresponding methyl or ethyl 2-C4- (6-halo-2-quinoxalinyloxy)phenoxy]propanoates by methods that are known in the art. The methyl and ethyl 2-4-(6-halo-2-quinoxalin yloxy)phenoxy]propanoates can be prepared by the procedure described under Method A, using methyl cr ethyl 2-(4-hydroxyphenoxy)propanoate in lieu of (III). Method C The condensation of the alkali metal salt of a 6-halo-2-(4-hydroxyphenoxy)quinoxaline (V) with methoxy or ethoxyethoxyethyl 2-bromopropanoate (VI) in a. suitable solvent such as methyl ethyl ketone or DMF provides another synthetic procedure that may be used to prepare the compounds (I) disclosed herein. EMI6.1 The 6-halo-2-(4-hydroxyphenoxy)quinoxalines (V) are prepared by the multi-step synthesis outlined below: EMI6.2 2-chloro-6-haloquinoxaline is condensed with 4-benzyloxyphenol or 4-methoxyphenol in the presence of sodium methoxide or an alkali metal hydride to give (VII). Next the methyl or benzyl group is removed by methods known in the art, for example, those described in Belgian Patent 868,875 or Tetrahedron 24, 2289 (1968), to both. of which the reader is referred for further information, to yield the desired 6-halo-2 (4-hydroxyphenoxylquinoxalines. Esters of type (VI) are readily prepared by the addition of 2-bromopropionyl chloride to methoxy or ethoxyethoxyethanol in-the presence of an acid acceptor. The following examples illustrate the preparation of some of the compounds of the invention. Example 1 2-Methoxyethoxyethyl 2-E4-(6-chloro-2-quinoxalinyloxy)- phenoxy]propanoate In a nitrogen atmosphere, slowly add a solution of 5.7 g (0.02 mole) methoxyethoxyethyl 2-(4-hydroxy phenoxy)propanoate in 25 cc of dimethylformamide to 0.5 g (0.02 mole) sodium hydride in 25 cc of DMF. When the evolution of hydrogen ceases, stir at room temperature for 30 minutes, then add 4.0 g (0.02 mole) 2,5-dichloroquinoxaline. Heat at 1300for 6 hours and then cool to room temperature. Pour into about 200 cc of ice cold water, and extract the product into methylene chloride. Wash the CH2C12 extract with water, dry and concentrate under vacuum to yield the desired ester. Following the teachings of Example 1 and by substituting an appropriate 2-chloroquinoxaline and an appropriate alkyl 2-(4-hydroxyphenoxy)propanoate, the esters in Table I can be prepared. Table I EMI8.1 X R F CH3 Br CH3 C1 - C2H5 n024 = 1.5655 F C2H5 Br C2F5 Example 2 2-Ethoxyethoxyethyl 2-4-(6-chloro-2-quinoxalinyloxy) phenoxyJpropansate The'title compound was prepared by treatment of 2-[4-(6-chloro-2-quinoxalinyloxy]phenoxy]propanoic acid in chlorobutane with thionyl chloride and a catalytic amount of dimethylformamide. To a cold (5 C) solution of 3.15 g (.009 mol) 2-[4-(6-chloro-2-quin- oxalinyloxy)phenoxygpropionyl chloride in 50 cc tetrahydrofuran, was added a solution of 0.7 cc pyridine and 1'35 ce (0.009 mol) 2-(2-ethcxyethoxy)ethanol in 5 cc tetrahydrofuran. The reaction mixture was stirred overnight at room temperature. Insoluble material was removed by filtration. The filtrate was concentrated under vacuum, dissolved in methylene chloride, washed with 5% hydrochloric acid and 50% sodium bicarbonate solutions, dried over magnesium sulfate, and concentrated under vacuum to give 2.2 g of the product, nD24 = 1.5655. NMR (CDCl3)#: 1.2 (t, J = 7' Hz, 3H); 1.7 d, J = 7 Hz, 3H); 3.6 (m, 8H); 4.3 (m, 2H); 4.8 (q, J = 7 Hz, lH); 7.1 (m, 4H); 7.6 (m, 2H); 8.1 Cm, lH); 8.7 (s, 1H). The procedure outlined above can also be used to prepare the compounds in Table II. Table II EMI9.1 X R F CH3 Br CH3 C1 cH3 F C2H5 Br C2H5 Example 3 2-Methoxyethoxyethyl-2-[4-(6-fluoro-2-quinoxalinyloxy)- phenoxy ]propanoate In a nitrogen atmosphere, add a evolution of 5.1- Q (0.02 mole) 6-fluoro-2-(4-hydroxyphenoxy)quinoxaline in 30 cc dimethylformamide to 0.9 g (0.02 mole) 57 sodium hydride in 20 cc dimethylformamide at about 200C. When the evolution of hydrogen ceases, add 5.1 g (0.02 mole) methoxyethoxyethoxyethyl 2-bromopropanoate. Heat the reaction mixture at approximately 8O0C until the reaction is complete. Pour the reaction mixture into water and extract with methylene chloride. Combine the ethereal extracts and dry over magnesium sulfate. Removal of the methylene chloride gives the desired product. The compounds listed in Table III can be prepared by a similar fashion from the appropriate 2-(4hydroxyphenoxy)quinoxaline and the methoxy or ethoxyethoxyethyl 2-bromopropionate. Table III EMI10.1 X R C1 CH3 Br CH3 a Cl C2H5 n024 = 1.5655 F C2H5 Br C2K5 Formulations Useful formulations of the compounds of Formula I can be prepared in conventional ways. They include dusts, granules, pellets, wettable powders, emulsifiable concentrates and the like. Many of these may be applied directly. Sprayable formulations can be extended in suitable media and used at spray volumes of from a few liters to several hundred liters per hectare. High strength compositions are primarily used as intermediates for further formulation. The formulations, broadly, contain about 0.1% to 99% by weight of active ingredient(s) and at least one of (a) about 0.1% to 20% surfactant(s) and (b) about 1% to 99.9% solid or liquid diluent(s). More specifically, they will contain these ingredients in the following approximate proportions: Table II Weight Percent* - Active Ingredient Diluent(s) Surfactant(s) Wettable Powders 5-25 65-94 1-10 Emulsifiable 3-50 35-97 0-15 Concentrates Dusts 1-25 70-99 0-5 Granules and Pellets 0.1-20 75-99.9 0-15 High Strength 90-99 0-10 0-2' Compositions * Active ingredient plus at least one of a Surfactant or a Diluent equals-100 weight percent. Lower or higher levels of active ingredient can, of course, be present depending on the intended use and the physical properties of the compound. Higher ratios of surfactant'to active ingredient are sometimes desirable; and are achieved by incorporation into the formulation or by tank mixing. Typical solid diluents are described in Watkins, et al.-, "Handbook of,Insecticide Dust Diluents and Carriers", 2nd Ed., Dorland Books, Caldwell, New Jersey, but other solids, either mined or manu-fac- tured, may be used. The more absorptive diluents are preferred for wettable powders and the denser ones for dusts. Typical liquid diluents and solvents are described in Marsden, "Solvents Guide," 2nd Ed., Interscience, New York, 1950. Solubility under 0.1% is preferred for suspension concentrates; solution concentrates are preferably stable against phase separation at OOC. "McCutcheon's Detergents and Emulsifiers Annual", MC Publishing Corp., Ridgewood, New Jersey, as well as Sisely and Wood, "Encyclopedia of Surface Active Agents", Chemical Publishing Co., Inc., New York, 1964, list surfactants and recommended uses. All formulations can contain minor amounts of additives to reduce foaming, caking, corrosion, microbiological growth, etc. The 'methods af making such compositions are well known. Solutions are prepared by simply mixing the ingredients. Fine solid c.ompositions are made by blending and, usually, grinding as in a hammer or fluid energy mill. Suspensions are prepared by wet milling (see, for example, Littler, U.S. Patent 3,060,084). Granules and pellets may be made by spraying the active material upon preformed granular carriers or by agglomeration techniques. See J. E. Browning, "Agglomeration, Chemical Engineering, December 4, 1967, pp. 147ff. and "Perry's Chemical Engineer's Handbook", 5th Ed., McGraw-Hill, New York, 1973, pp. 8-57ff. For further information regarding the art of formulation, see for example: H. M. Loux, U.S. Patent 3,235,361, February 15, 1966, Col. 6, line 16 through Col. 7, line 19 and Examples 10 through 41; R. W. Luckenbaugh, U.S. Patent 3,309,192, March 14, 1967, Col. 5, line 43 through Col. 7, line 62 and Examples 8, 12, 15, 39, 41, 52, 53, 58, 132, 138-140, 162-164, 166; 167 and 169-182; H. Gysin and E. Knusli, U.S. Patent 2,891,855, June 23, 1959, Col. 3, line 66 through Col. 5, line 17 and Examples 1-4; G. C. Klingman, "Weed Control as a Science", John Wiley & Sons, Inc., New York, 1961, pp. 81-96; and J. D. Fryer and S. A. Evans, "Weed Control Handbook", 5th Ed., Blackwell Scientific Publications, Oxford, 1968, pp. 101-103. In the following examples, all parts are by weight unless otherwise indicated. Example 4 Wettable Powder 2-methoxyethoxyethyl 2-(4-C6-bromoquinoxalin-2-yl)- oxy).phenoxyzpropanoate 5 sodium alkylnaphthalenesulfonate 2% sodium ligninsulfonate 2% synthetic amorphous silica 3% kaolinite 88% The ingredients are blended, ball-milled, passed through 50 mesh screen, reblended, and packaged. Example 5 Wettable Powder 2-ethoxyethoxyethyl 2-[4-(6-chloroquinoxalin-2-yl- oxy ) phenoxy ]propandate 25% sodium alkylnaphthalenesulfonate 2% low viscosity methyl cellulose 2% diatomaceous earth 71% The active ingredient is dissolved in a suitable. solvent and sprayed on the blended mixture of surfactants and diluents in a rotary container. -After solvent evaporation, the blend-ed mixture is ball-milled and passed through a 50 mesh screen. The product is reblended before packaging. Example 6 Granule 5% Wettable Powder of Example 5 attapulgite granules 95% (U.S.S. 2040 mesh; 0.84-0.42 mm) A slurry of wettable powder containing b 25% solids is sprayed on the surface of attapulgite granules in a double-cone blender. The granules are dried and packaged. Example 7 Extru.ded Pellet 2-ethoxyethoxyethyl 2-[4-(6-chloroquinoxalin-2-yl- oxy)phenoxy]propanoate 10% anhydrous sodium sulfate 10t crude calcium ligninsulfonate 5% sodium alkylnaphthalenesulfonate 1 calcium/magnesium bentonite 74% The ingredients are blended, hammer-milled and then moistened with about 12t water. The mixture is extruded as cylinders about 3 mm diameter which are cut to produce pellets about 3 mm long. These may be used directly after drying, or the dried pellets may be crushed to pass a U.S.S. No. 20 sieve (0.84 mm openings). The granules held on a U.S.S. No. 40 sieve (0.42 mm openings) may be packaged for use and the fines 'recycled. Example 8 Wettable Powder 2-methoxye'thoxyethyl 2-t4-t6-fluoroquinoxalin-2-yl- oxy)phenoxy]propanoate 20% sodium' aikylnaphthalenesulfonate 4% sodium ligninsulfonate 4% low viscosity methyl cellulose 3% attapulgite "A" 69% The ingredients are thoroughly blended. After grinding in a hammer-mill to produce particles essentially all below 100 microns, the material is reblended and sifted.through a U.S.S. No. 50 sieve (0.3 mm opening) and packaged. Example 9 Low Strength Granule 2-ethoxyethoxyethyl 2-L4-C 6-fluoroquinoxalin-2-,yl oxy) phenoxy ]propanoate 1% N,N-'dimethylformamide 9% .attapulgite granules 90% (U.S.S. 20-40 sieve) The active ingredient is dissolved in the solvent 'and the solution is sprayed upon dedusted granules in a double cone blender. After spraying of the solution has been completed, the blender is allowed to run fdr a short period and then the granules are packaged. Example 10 Low Strength Granule 2-methoxyethoxyethyl 2-E4-(6-chloroquinoxalin-2-yl oxy)phenoxyzpropansate 0.1% attapulgite granules 99.9% (U.S.S. 20-40 mesh) The active ingredient is dissolved in a solvent and the solution is sprayed upon dedusted granules in a double-cone blender. After spraying of the solution has been completed, the material is warmed to evaporate the solvent. The material is allowed to cool and then packaged. Example 11 Granule 2-ethoxyethoxyethyl 2-[4-(6-chloroquinoxalin-2-yl oxy)phenoxyjpropanoate 20% wetting agent 1% crude ligninsufonate salt (containing 10% 5-20% of the natural sugars) attapulgite clay 69% The ingredients, are blended and milled to pass through a 100 mesh screen. This material is then added to a fluid bed granulator, the air flow is adjusted to gently fluidize the material, and a fine spray of waster is sprayed onto the fluidized material. The fluidization and spraying are continued until granules of the desired size range are made. The spraying is stopped, but fluidization is continued, optionally with heat, until the water content is reduced to the desired level, generally less than 1%. The material is then discharged, screened to the desired size range, generally 14-100 mesh (1410-149 microns), and packaged for use. Example 12 Hiqh Strength Concentrate 2-ethoxyethoxyethyl 2-[4-(6-chloroquinoxalin-2-yl oxy) phenoxy) propanoate 99% dodecylphenol polyethylene glycol ether 1.0% The ingredients are blended and bottled in a suitable container. The concentrate may be formulated further if necessary. Example 13 Dust 2-ethoxyethoxyethyl 2-[4-(6-bromoquinoxalin-2-yl- oxy)phenoxy]propanoate 10 ó synthetic silica 10% Pyrophyllite 80% The active ingredient is blended with synthetic silica and then passed through a hammer-mill to produce particles substantially all below 200 microns. The ground concentrate is' then blended with powdered pyrophyllite until homogeneous. Example 14 Emulsifiable Concentrate 2-ethoxyethoxyethyl 2-4-(6-chloroquinoxalin-2-yl- oxy)phenoxy]propansate 20% chlorobenzene 74% sorbitan monostearate and polyoxyethylene condensates thereof 6% The ingredients are combined and stirred to produce a solution which can be emulsified in water for application, Utility The compounds of the present invention are useful for broad-spectrum weed control and for controlling grass weeds in broadleaf crops, such as beans, flax, sugarbeet, cabbage, tomatoes, potatoes, carrots, cucurbits, endive, beets, etc: Suitable application rates will generally be found in the range from 0.005 to 20 hgha, preferably 0.02 to 10 kg/ha, 'the lower rates being selected for use in the presence of crop plants. The utility of these compounds is broadly similar to those of our EP-A-42,750, to which the reader is referred for further information. The compounds also have a particular and unexpected utility on rice. Rice is one of the world's most important crops and is the main food source for much of the world's population. In fact, on an acreage basis, rice ranks as the second largest crop in the entire world. It is very important that the yield of rice be maximized to feed a hungry world. Accordingly, it is important that weeds that compete with rice for available light, nutrients, etc., be controlled so as to produce rice in a high yield. Barnyardgrass (Echinochloa crusgalli), and closely related Echinochloa plants are extremely pre velant and harmful weeds in rice plantings around the world. Indeed, the well-known journal "Agrichemical Age" (May, 1977 issue, page 11) reported that a barn-' yardgrass infestation of only one plant per square foot 2 (10.76 plants per m ), -if allowed to compe-te all season with a good stand of rice, would reduce the rice yield b 25%. Yet, a normal infestation of barnyardgrass in a rice stand can be many times as dense. Therefore it is obvious that barnyardgrass can severely reduce the yield of rice,, and compounds that selectively control barnyardgrass in rice plantings are extremely valuable to mankind. The present invention teaches that certain novel compounds of Formula I have the important utility of selectively controlling barnyardgrass in rice plantings. To control the growth of weeds in paddy rice, compounds of Formula I are applied to the paddy at a rate of about 0.5 ,to 50 grams per hectare, preferably about 2 to 20 grams per hectare, the application rate depending on considerations such as the soil type, weed pressure, timing of application, and particular compound applied. ' The compounds can be applied in several ways; They can be applied directly to the water surface of the rice paddy either about- one to four days before transplanting rice into the paddy or about two to twenty days after transplanting rice into the paddy. Alternatively, they can be applied directly to the paddy soil before flooding and transplanting. For reasons of effectiveness and increased rice tolerance, the compounds are preferably applied between about three to twelve days after transplanting. The following example demonstrates the utility of the compounds of the present invention in comparison with a closely related compound within the scope of a prior disclosure (Compound A; disclosed generically in DE-A-3,004,770 and EP-A-23,785 but not prepared or characterised). Example 15 Test samples were formulated in a non-phytotoxic solvent and applied to the paddy water three days after transplanting of-rice. The paddy soil contained propagules of several weeds which were just beginning to sprout. The test was maintained in a greenhouse, and plant response ratings were taken six weeks after application. The plant response ratings are presented. in Table III and consist of a number and a letter. The number ranges from zero to ten and represents the extent'of the response, with zero indicating no response and ten indicating 100 < control. The letter describes the type of the. response, with "C" representing chlorosis/necrosis (chronic response) and "G2' representing growth retardation. Table III EMI21.1 Treat- Rate, Barnyard- Water ment g ai/ha Rice grass* Chestnut* A 1 0 0 0 4 0 5C 8 0 9C 0 B 1 0 9C 0 4 .1G,2C lOC 0 8 9C lOC 10C * Echinochloa sup. and Eleocharis sp., respectively. In reviewing the data presented in Table III it is evident that the compound of this invention, Compound B, is far more effective in controlling barnyardgrass than the art compound, Compound A.

Claims: Claims: 1. A compound of the formula: EMI22.1 where X is Cl, F or Br; and R is CH3 or CH2CH3; excluding mixtures of 2-etoxyethoxyethyl-2- [4- (6- chloroquinoxalin-2,-yloxy) phenoxy] propanoate with a substantial proportion of the corresponding 7-chloro isomer. 2. The compound of Claim 1, 2-ethoxyethoxy ethyl-2-[4-(6-chloroquinoxalin-2-yloxy)phenoxy]propanOate, excluding mixtures thereof with a substantial proportion of the corresponding 7-chloro isomer. 3. The compound-of Claim 1, 2-methoxyethoxyethyl 2-t4-(6-chloro-2-quinoxalinyloxy)phenoxy3propanOate. 4. The compound of Claim 1, 2-methoxyethoxyethyl 2-[4-(6-fluoro-2-auinox,alinloxy)phenoxy3propanOate. 5. A composition for the control pf undesirable vegetation comprising an effective amount of a herbicidal compound and at least one of (a) a surface active agent and (b) a solid or liquid.diluent, characterised in that said herbicidal compound comprises a compound of any of claims 1 to 4. 6. A method for the selective control of undesirÅable vegetation in the presence of crop plants by applying to the locus to be protected an effective amount of a herbicidal compound, characterised in that said herbicidal compound comprises a compound of any of claims 1 to 4. 7. The method of claim 6 wherein said crop plants are paddy rice. 8. The method of claim 7 wherein said compound is applied at a rate of f.rom 2 to 20 g/ha. 9. The method of claim 6, 7 or 8 wherein the compound of claim 2 is applied. 10. A process for the preparation of a compound of claim 1 which comprises: (a) contacting an alkali metal salt of a compound of formula EMI23.1 with a 2-chloro-6-haloquinoxaline of formula EMI23.2 wherein R and X are as defined in claim 1; or '(b) reacting an acid chloride of formula EMI23.3 wherein X is as defined in claim 1, with 2-(2-methoxyethoxy)ethanol or 2-(2-ethoxyethoxy)ethanol in the presence of an acid acceptor; or .(c) reacting a 6-halo-2-(4-hydroxyphenoxy)quinoxaline of fo,rmula EMI23.4 with a bromoester of formula EMI23.5 in the presence of an acid acceptor, wherein X and R are as defined in claim 1. Claims: 1. A process for the preparation of a compound of the formula EMI25.1 :where X is C1, F or Br; and R is CH3 or CH2CU3- excluding mixtures of 2-ethoxyethoxyethyl-2-[4-(6- chloroquinoxalin-2-vloxy)phenoxy]propanoate with a substantial proportion of the corresponding 7-chloro isomer, which comprises: (a) contacting an alkali metal salt of a compound of formula EMI25.2 with a 2-chloro-6-haloquinoxaline of formula EMI25.3 wh'erein R and Xare as defined above; or (b) reacting an acid chloride of formula EMI25.4 with 2'- (2-methoxyethoxy) ethanol or 2-(2-ethoxyethoxy) ethanol in the presence of an acid acceptor, wherein X is as defined above; or (c) reacting a 6-halo-2-(4-hydroxyphenoxy)quinoxaline of formula EMI26.1 with a bromoester of formula EMI26.2 in the presence of an acid acceptor,. wherein X and R are as defined above. 2. The process.of claim 1 wherein the product is 2-ethOxyethoxyethyl-2-[4-(6-chloroguinoxalin-2-ylOxy) phenoxy]propanoate, excluding mixtures thereof with a substantial proportion of the corresponding 7-chloro isomer. 3. The process of Claim lkerein the product is 2.methoxyethoxyethyl 2-[4-(6-chloro-2-quinoxalinyloxy) phenoxy] propanoate or 2-methoxyethoxyethyl 2-[4-(6-fluoro-2-quinoxalinyloxy) phenoxy]propanoate. 4. A method -for the selective control of undesirable vegetation in the presence of crop plants by applying to the locus to be protected an effective amount of a herbicidal compound, cha,racterised 'in' that said herbicidal compound comprises a compound of the formula (I) wherein X and R are as defined in claim 5. A method for the selective control of weeds in paddy rice which comprises applying to the paddy a herbicidally effective amount of a compound of the formula (I) wherein X and R are as defined in claim 1. 6. The method of claims 4 or 5 wherein said compound is ,2-ethoxyethoxyethyl 2-[4-(6-chloroquinoxalin-2- yloxyMphenoxy]propanoate, excluding mixtures thereof with a substantial proportion of the corresponding 7-chloro isomer.

Inventors: FAWZI, MAGED MOHAMED
Applicants: E.I. DU PONT DE NEMOURS AND COMPANY
Application year: 1982
Main classification: C07D241
IPC codes: A01N43, C07D241