GB2233647A

GB2233647A - Optically resolved 2-(dibenzofuran-3-oxy)-propionic acid derivatives having a herbicidal action

Info

Publication number: GB2233647A
Application number: GB9015400A
Authority: GB
Inventors: Costin Rentzea; Hardo Siegel; Peter Plath; Bruno Wuerzer; Karl-Otto Westphalen
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1989-07-14
Filing date: 1990-07-13
Publication date: 1991-01-16
Also published as: FR2649707A1; GB9015400D0

Abstract

Optically active (R)-2-(dibenzofuran-3-oxy)-propionic acid derivatives of the formula I <IMAGE> [where Y is hydrogen, C1-C14-alkyl (which is optionally substituted by up to three halogen or alkoxy), or is alkenyl, alkynyl, or cycloalkyl (which is optionally substituted by methyl), or is radical of the formula -N=CR<1>R<2> (where R<1> & R<2> are alkyl); and X is fluoro, chloro, bromo, methyl, ethyl or triflouromethyl] have enhanced herbicidal activity and can be used for combating unwanted plant growth.

Description

2-(dibenzofuran-3-oxy)-propionic acid derivatives having a herbicidal action Racemic dibenzofuranoxyalkanoic acid derivatives, in particular those substituted in the 7-position, are known to be herbicides and are described in, for example, DE-A 27 32 924, DE-A 28 23 424 and US-A 41 99 346. It is stated that application rates of up to one kg per ha are necessary, depending on the target plant species.

Although the skilled worker recognizes that the compounds described by the formula are racemates and must be capable of being separated into optical isomers, there is no indication of the herbicidal action of the particular antipodes.

We have found that the optically active (R)-2-(dibenzofuran -3-oxy)-propionic acid derivatives defined below and their agriculturally tolerated salts have an unexpectedly strong herbicidal action and are selective with respect to crops. Their preparation, agents which contain these optically active esters as active ingredients, and their use as herbicides generally and especially for the selective control of weeds in crops such as cereal, corn, rice, sorghum and sugar cane are described.

The novel (R)-2-(dibenzofuran -3-oxy)-propionic acid derivatives are defined by the formula I

In this formula, Y is hydrogen or is Cl-Cl4-alkyl which is unsubstituted or substituted by up to three halogen atoms or C1-C4-alkoxy groups, or is C - 3 6 kynyl, or C - 6 on is C3-C6-alkenyl, C -C -al or C6-cyclo- alkyl which its unsubstituted or substituted by methyl, or is a radical of the formula -N=CR1R2, where R1 and R are each independently C1-C4-alkyl, and X is fluoro, chloro, bromo, methyl, ethyl or trifluoromethyl.

The (R) -2- (dibenzofuran-3-- oxy) -propionic acid derivatives of the formula I are particularly suitable for controlling broad-leaved weeds, eg. Abutilon theophrasti, Amaranthus retroflexus, Asclepias spp., Chenopodium album, Chrysanthemum segetum, Datura stramonium, Eupnorbia geniculata, Galium aparine, Ipomoea spp., Matricaria chamomilla, Nicandra physaloides, Polygonum persicaria, Sesbania exaltata, Sinapis arvensis, Solanum nigrum, Stellaria media, Viola tricolor, Mentha arvensis and Xanthium pensylvanicum, in a very wide range of agricultural monocotyledon crops.

The (R) -2- (dibenzofuran-3- oxy) -propionic acid derivatives of the formula .1 and their salts have an excellent herbicidal action when used by the preemergence and postemergence methods. The active ingredients have excellent selectivity, which extends to many large-scale crops, eg. cereals (barley, wheat and oats), corn, rice, sorghum and sugar cane. The fact that the herbicidal action of the. optically active derivative, at half the application rate, is stronger than t:he herbicidal action of the corresponding racemate is surprising.

The alkyl radicals Y in formula I may be straight-chain or branched and may be of 1 to 14 carbon atoms. Radicals of 1 to 8 carbon atoms are preferred, in particular methyl, isopentyl, n-octyl, isooctyl and 2ethyl-n-hexyl. Examples of halogen-substituted alkyl radicals are, in particular, chlorine-substituted alkyl radicals, such as 2-chloroethyl, 4-chloro-n-butyl or 2,2,2-trichloroethyl. Examples of alkoxy-substituted alkyl radicals are methoxymethyl, 2-methoxyethyl, 2ethoxyethyl and 2-n-butoxyethyl. Preferred alkenyl, alkynyl and cycloalkyl radicals are allyl, propargyl, cyclohexyl and 2-methylcyclohexyl. Particularly suitable members of the group -N=CR1R2 are the radicals -N=C(CH3)2 and -N=C (C2H5)2.

Preferred substituents X in formula I are chlorine and bromine.

The compounds of the formula I are obtained by reacting an appropriate dibenzofuran-3-ol of the general formula

with the appropriate S-enantiomer of a propionic ester of the formula III

where Z is chlorine, bromine, mesylate or tosylate, in the presence of an acid acceptor, eg. sodium hydroxide, potassium hydroxide, sodium carbonate or potassium carbonate, and, inter alia, in the presence of a diluent, such as water, methanol, ethanol, propanol, isopropanol, acetone, acetonitrile, dioxane or dimethylformamide or a mixture thereof, at a sufficiently high temperature below 1200C. If the optically active R-propionic acid derivative of the formula IV

is available, it is of course also possible to carry out the reaction with the corresponding alcohol YOH (V) under conventional esterification conditions.

In the reaction of a dibenzofuran-3-ol of the formula II with an ester of the formula- III, a Walden inversion takes place at the chiral carbon atom of the propionic ester. This results in each case in the formation of the R-enantiomer of the ester (I) or of the acid of the formula IV from the S-enantiomer of the propionic ester (III). The esterification of the acid (IV) with the alcohol (V) takes place with retention of the configuration.

Preparation Examples EXAMPLE 1 R-(+)-2-(7-Chlorodibenzofuran-3- .oxy)-propionic acid 60 g (0.75 mol) of 50% strength sodium hydroxide solution are added dropwise to 54.6 g (0.25 mol) of 7 chlorodibenzofuran-3-ol in 100 ml of ethanol. 54.6 g (0.4 mol) of ethyl S-(-)-chloropropionate are then added dropwise at 500C and under 70 mbar in the course of 30 min. A mixture of ethanol and water is distilled off.

After 150 ml of distillate have been obtained, 100 ml of water are added, stirring is carried out for 30 min at 100 C and under atmospheric pressure, the mixture is cooled to 20 C, 500 ml of water are added and the mixture is acidified with concentrated hydrochloric acid. The precipitate is filtered off under suction, washed with water and dried. 71 g (97.8% of theory) of R-(+)-2-(7 chlorodibenzofuran-3- oxy)-propionic acid are obtained as whitish gray crystals of melting point 178-1800C and (),acetone = +61.70.

EXAMPLE 2 n-Octyl R- (+) -2-(7-chlorodibenzofuran-3- oxy) -propionate A stirred mixture of 14.5 g (0.05 mol) of R-(+) 2- ( 7-chlorodibenzofuran-3- oxy) -propionic acid, 13 g (0.1 mol) of n-octanol, 75 ml of cyclohexane, 75 ml of toluene and 0.5 g of p-toluenesulfonic acid is refluxed until 0.9 g of water has separated off. The mixture is cooled to 200C, washed with water, dried over Na2SO4 and evaported down under reduced pressure. 19 g (94.48 of theory) of n-octyl R- (+) -2- ( 7-chlorodibenzofuran-3- oxy)-propionate are obtained as white crystals of melting point 36-37 C and [α ]D,acestone = 67.1 .

The compounds of the formula I which are listed in Table 1 are obtained in a similar manner, according to Preparation Examples 1 and 2. Because of their close structural relationships, they are expected to have an action similar to that of the compounds stated in the synthesis examples.

Table 1

Active X Y mp [ ]D,acetone Ingr. (0C] No.

3 F H 177-179 +70.90 4 Br H 155-158 +56.80 5 CH3 H +66.20 6 C2H5 H -62.10 7 CF3 H -58.30 8 Cl -CH3 87 +69.90 9 Cl -C2H5 59- 61 +72.80 10 Cl n-C3H7 41- 43 +77.80 11 Cl n-C4H9 38- 40 +79.90 12 Cl i-C4Hg 59- 62 +79.70 13 Cl s-C4Hg 59- 61 +75.10 14 Cl n-C5H1 1 26- 28 +750 15 Cl -CH2-CH2-CH(CH3)2 oil +72.30 16 Cl n-C6H13 oil +70.40 17 Cl cyclohexyl oil +76.90 18 Cl -CH3-CH(CH3)-CH2)5-CH3 oil +63.90 19 Cl -CH2-CH(C2HS)-(CH2)3-CH3 oil +68.40 20 Cl n-CgH19 oil +68.90 21 Cl n-C10H21 oil +68.40 22 Cl n-C14H29 43- 45 +49.9 23 Cl -CH2-CH2-O-CH2CH3 43- 45 +60.80 24 Cl -CH2-CH2-O-(CH2)3-CH3 oil +55.60 25 Cl -CH2-CH2-C 1 oil +66.20 26 Cl -(CH2)4-Cl oil +66.00 27 Cl -CH2-CC13 oil 28 Br -CH3 77- 79 +56.80 29 Br -C2H5 63- 65 +56.70 30 Br n-C3H7 62- 64 +56.80 31 Br i-C3H7 97- 99 +56.90 32 Br i-C4Hg 59- 61 +56.70 33 Br s-C4Hg 69- 72 +56.80 Table 1 (contd.) Active X Y mp (α]D,acetone Ingr. (0C) No.

34 Br -CH2-CH2-CH(CH3)2 oil +56.80 35 Br n-C6H13 oil +56.90 36 Br cyclohexyl 92- 94 +57.00 37 Br -CH2-CH(C2H5)-CH2)3CH3 oil +56.50 38 CF3 -CH3 39 CF3 -C2H5 40 CF3 s-C4H9 41 CF3 n-C6H13 42 CF3 -CH2-CH(C2H5)-(CH2)3CH3 43 CF3 -CH2-CH2-O-CH3 44 CH3 -CH3 45 CH3 -CH2-CH(C2H5)-(CH2)3CH3 46 C2H5 n-C4Hg 47 C2H5 s-C4-H9 48 C2H5 -CH2-CH(C2H5)-(CH2)3CH3 The (R)-2-(dibenzofuran-3-oxy)-propionic acid derivatives of the formula I, and herbicidal agents containing them, may be applied for instance in the form of directly sprayable solutions, powders, suspensions (including high-percentage aqueous, oily or other suspensions), dispersions, emulsions, oil dispersions, pastes, dusts, broadcasting agents, or granules by spraying, atomizing, dusting, broadcasting or watering.The forms of application depend entirely on the purpose for which the agents are being used, but they must ensure as fine a distribution of the active ingredients according to the invention as possible.

For the preparation of solutions, emulsions, pastes and oil dispersions to be sprayed direct, mineral oil fractions of medium to high boiling point, such as kerosene or diesel oil, further coal-tar oils, and oils of vegetable or animal origin, aliphatic, cyclic and aromatic hydrocarbons such as toluene, xylene, paraffin, tetrahydronaphthalene, alkylated naphthalenes and their derivatives, methanol, ethanol, propanol, butanol, cyclohexanol, cyclohexanone, chlorobenzene, isophorone, etc., and strongly polar solvents such as N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, water, etc. are suitable.

Aqueous formulations may be prepared from emulsion concentrates, pastes, oil dispersions, wettable powders or water-dispersible granules by adding water. To prepare emulsions, pastes and oil dispersions the ingredients as such or dissolved in an oil or solvent may be homogenized in water by means of wetting or dispersing agents, adherents or emulsifiers. Concentrates which are suitable for dilution with water may be prepared from active ingredient, wetting agent, adherent, emulsifying or dispersing agent and possibly solvent or oil.

Examples of surfactants are: alkali metal, alkaline earth metal and ammonium salts of aromatic sulfonic acids, e.g., ligninsulfonic acid, phenolsulfonic acid, naphthalenesulfonic acid and dibutylnaphthalenesulfonic acid, and of fatty acids, alkyl and alkylaryl sulfonates, and alkyl, lauryl ether and fatty alcohol sulfates, and salts of sulfated hexadecanols, heptadecanols, and octadecanols, salts of fatty alcohol glycol ethers, condensation products of sulfonated naphthalene and naphthalene derivatives with formaldehyde, condensation products of naphthalene or naphthalenesulfonic acids with phenol and formaldehyde, polyoxyethylene octylphenol ethers, ethoxylated isooctylphenol, ethoxylated octylphenol and ethoxylated nonylphenol, alkylphenol polyglycol ethers, tributylphenyl polyglycol ethers, alkylaryl polyether alcohols, isotridecyl alcohol, fatty alcohol ethylene oxide condensates, ethoxylated castor oil, polyoxyethylene alkyl ethers, ethoxylated polyoxypropylene, lauryl alcohol polyglycol ether acetal, sorbitol esters, lignin-sulfite waste liquors and methyl cellulose.

Powders, dusts and broadcasting agents may be prepared by mixing or grinding the active ingredients with a solid carrier.

Granules, e.g., coated, impregnated or homogeneous granules, may be prepared by bonding the active ingredients to solid carriers. Examples of solid carriers are mineral earths such as silicic acids, silica gels, silicates, talc, kaolin, attapulgus clay, limestone, lime, chalk, bole, loess, clay, dolomite, diatomaceous earth, calcium sulfate, magnesium sulfate, magnesium oxide, ground plastics, fertilizers such as ammonium sulfate, ammonium phosphate, ammonium nitrate, and ureas, and vegetable products such as grain meals, bark meal, wood meal, and nutshell meal, cellúlosic powders, etc.

The formulations contain from 0.1 to 95, and preferably 0.5 to 90, % by weight of active ingredient.

Examples of formulations are as follows: I. 20 parts by weight of compound no. 19 is dissolved in a mixture consisting of 80 parts by weight of xylene, 10 parts by weight of the adduct of 8 to 10 moles of ethylene oxide and 1 mole of oleic acid-N-monoethanolamide, 5 parts by weight of the calcium salt of dodecylbenzenesulfonic acid, and 5 parts by weight of the adduct of 40 moles of ethylene oxide and 1 mole of castor oil. By pouring the solution into 100,000 parts by weight of water and uniformly distributing it therein, an aqueous dispersion is obtained containing 0.02% by weight of the active ingredient.

II. 20 parts by weight of compound no. 19 is dissolved in a mixture consisting of 40 parts by weight of cyclohexanone, 30 parts by weight of isobutanol, 20 parts by weight of the adduct of 7 moles of ethylene oxide and 1 mole of isooctylphenol, and 10 parts by weight of the adduct of 40 moles of ethylene oxide and 1 mole of castor oil. By pouring the solution into 100,000 parts by weight of water and finely distributing it therein, an aqueous dispersion is obtained containing 0.02% by weight of the active ingredient.

III. 20 parts by weight of compound no. 8 is dissolved in a mixture consisting of 25 parts by weight of cyclohexanone, 65 parts by weight of a mineral oil fraction having a boiling point between 210 and 28O0C, and 10 parts by weight of the adduct of 40 moles of ethylene oxide and 1 mole of castor oil. By pouring the solution into 100,000 parts by weight of water and uniformly distributing it therein, an aqueous dispersion is obtained containing 0.02% by weight of the active ingredient.

IV. 20 parts by weight of compound no. 2 is well mixed with 3 parts by weight of the sodium salt of diisobutylnaphthalene-alpha-sulfonic acid, 17 parts by weight of the sodium salt of a lignin-sulfonic acid obtained from a sulfite waste liquor, and 60 parts by weight of powdered silica gel, and triturated in a hammer mill. By uniformly distributing the mixture in 20,000 parts by weight of water, a spray liquor is obtained containing 0.1% by weight of the active ingredient.

v. 3 parts by weight of compound no. 15 is intimately mixed with 97 parts by weight of particulate kaolin. A dust is obtained containing 3% by weight of the active ingredient.

VI. 30 parts by weight of compound no. 8 is intimately mixed with a mixture consisting of 92 parts by weight of powdered silica gel and 8 parts by weight of paraffin oil which has been sprayed onto the surface of this silica gel. A formulation of the active ingredient is obtained having good adherence.

VII. 20 parts by weight of compound no. 19 is intimately mixed with 2 parts of the calcium salt of dodecylbenzenesulfonic acid, 8 parts of a fatty alcohol polyglycol ether, 2 parts of the sodium salt of a phenolsulfonic acid-urea-formaldehyde condensate and 68 parts of a paraffinic mineral oil. A stable oily dispersion is obtained.

The active ingredients or the herbicidal agents containing them may be applied pre- or postemergence. If certain crop plants tolerate the active ingredients less well, application techniques may be used in which the herbicidal agents are sprayed from suitable equipment in such a manner that the leaves of sensitive crop plants are if possible not touched, and the agents reach the soil or the unwanted plants growing beneath the crop plants (post-directed, lay-by treatment).

The application rates depend on the objective to be achieved, the time of the year, the plants to be combated and their growth stage, and are from 0.001 to 3.0, preferably 0.01 to 1.0, kg of active ingredient per hectare.

To increase the spectrum of action and to achieve synergistic effects, the compounds I may be mixed with each other, or mixed and applied together with numerous representatives of other herbicidal or growth-regulating active ingredient groups. Examples of suitable components are diazines, 4H-3,1-benzoxazine derivatives, benzothiadiazinones, 2,6-dinitroanilines, N-phenylcarbamates, thiolcarbamates, halocarboxylic acids, triazines, amides, ureas, diphenyl ethers, triazinones, uracils, benzofuran derivatives, quinolinecarboxylic acids, (hetero)-aryloxyphenoxypropionic acid derivatives (salts, esters, amides), etc.

It my also be useful to apply the compounds I, either alone or in combination with other herbicides, in admixture with other crop protection agents, e.g., agents for combating pests or phytopathogenic fungi or bacteria. The compounds may also be mixed with solutions of mineral salts used to remedy nutritional or trace element deficiencies. Non-phytotoxic oils and oil concentrates may also be added.

In view of the numerous application methods possible, the compounds according to the invention, or agents containing them, may be used in a large number of crops for removing unwanted plants. Those which follow are given by way of example: Botanical name Common name Avena sativa oats Pennisetum glaucum pearl millet Saccharum officinarum sugar cane Secale cereale rye Sorghum bicolor (s. vulgare) sorghum Sorghum dochna sorgo Triticum aestivum wheat Triticum durum durum wheat Zea mays Indian corn, sweet corn, maize and lawns and fodder grasses.

use examples The herbicidal action of the (R)-2-(dibenzofuran-3-oxy)-propionic acid derivatives of the formula I on the growth of the test plants is illustrated in the following greenhouse experiments.

The vessels employed were plastic flowerpots having a volume of 300 cm3 and filled with a sandy loam containing about 3.k humus. The seeds of the test plants were sown separately, according to species.

For the postemergence treatment, either plants sown directly in the pots and grown there were used, or plants which were cultivated separately as seedlings and were transplanted to the vessels a few days before treatment.

Depending on growth form, the plants were grown to a height of 3 to 15 cm before being treated with the active ingredients, which were suspended or emulsified in water and sprayed through finely distributing nozzles. The application rate for postemergence treatment was 1.0 kg/ha.

The pots were set up in the greenhouse, species from warmer climates in warmer areas (20 to 350C) and species from moderate climates at 10 to 200C. The experiments were run for from 2 to 4 weeks. During this time the plants were tended and their reactions to the various treatments assessed.

The assessment scale was 0 to 100, 100 denoting nonemergence or complete destruction of at least the visible plant parts, and 0 denoting no damage or normal growth.

The plants used in the experiments were Galium aparine ("GALAP"), Nicandra physaloides ("NICPH"), Sinapis alba (11SINAL"), Solanum nigrum ("SOLNI"), Abutilon theophrasti ("ABUTH"), and Polygonum persicaria ("POLPE').

The racemates of the following dibenzofuranoxy derivatives were tested as comparative agents:

(A; DE-A 28 23 424)

(B; DE-A 28 23 424) (c; DE-A 28 23 424) The results are given in Tables 2 to 4.

Table 2 Ex. No. Appl. rate Test plants and damage (%) [kg/ha] GALAP NICPH SINAL 8 0.060 85 75 80 A 0.125 80 65 70 Table 3 Ex. No. Appl. rate Test plants and damage [%] (kg/hai GALAP NICPH 19 0.125 80 70 B 0.250 65 70 Table 4 Ex. No. kg a.i./ha Test plants and damage 1%) ABUTH GALAP POLPE 28 0.03 80 95 0.06 85 94 65 0.125 90 94 95 0.25 95 93 95 C 0.125 45 70 0.25 80 65 40 0.5 82 72 60 1.0 100 73 60

Claims

1. Optically active (R)-2-(dibenzofuran-3-oxy)-propionic acid derivatives of the formula I

where Y is hydrogen or C1-C14-alkyl which is unsubstituted or substituted by up to three halogen atoms or C1-C4-alk oxy groups, or is C3-C6-alkenyl, C3-C6-alkynyl, or C3-C6-cycloalkyl which is unsubstituted or substituted by methyl or is a radical of the formula -N=CR1R2, where R1 and R2 are each independently C1-C4-alkyl, and X is fluoro, chloro, bromo, methyl, ethyl or trifluoromethyl, and salts thereof.

2. An agriculturally tolerated salt of an optically active (R)-2-(dibenzofuran-3-oxy)-propionic acid derivative of the formula I as set forth in claim 1.

3. Optically active (R)-2-(dibenzofuran-3-oxy)-pro- pionic acid derivatives as claimed in claim 1 or 2 wherein Y is hydrogen, C1-C14-alkyl which is unsubstituted or substituted by chlorine or C1-C4-alkoxy, or is allyl, propargyl, cyclohexyl, methylcyclohexyl, -N-C(CH3)2 or -N=C(C2H5)2.

4. Optically active (R)-2-(dibenzofuran-3-oxy)-pro- pionic acid derivatives claimed in claim 1 and hereinbefore identified in Example 1 or 2 or as any of Active Ingredients Nos. 3-48.

5. Methyl (R)-(+)-2-(7-chlorodibenzofuran-3-oxy)propionate.

6. 2-Ethylhexyl (R)-(+)-2-(7-chlorodibenzofuran-3oxy)-propionate.

7. Methyl (R)-(+)-2-(7-bromodibenzofuran-3-oxy)- propionate.

8. A process for the manufacture of an(R)-2-(dibenzo furan-3-oxy)-propionic acid derivative as claimed in claim 1, wherein a dibenzofuran-3-ol of the formula II

where X has the meaning given in claim is reacted with an S-enantiomer of a propionic ester of the formula III

where Y has the meaning given in claim 1 and Z is chloro, bromo, mesylate or tosylate, in the presence of an acid acceptor and a diluent at a sufficiently high temperature below 1200C, or an optically active (R)-propionic acid derivative of the formula IV

where X has the meaning given in claim 1, is reacted with an alcohol YOH (V) where Y has the meaning given in claim 1, under esterification conditions.

9. A process as claimed in claim 8 carried out substantially as hereinbefore described or illustrated in the foregoing Example 1 or Example 2.

10. Optically active (R)-2-(dibenzofuran-3-oxy)prop ionic acid derivatives when manufactured by a process as claimed in claim 8 or 9.

11. Herbicidal agents comprising an (R)-2-(dibenzofuran-3-oxy)-propionic acid derivative as claimed in any of claims 1 to 7 or 10.

12. A herbicidal composition comprising an inert additive and an (R)-2-(dibenzofuran-3-oxy)-propionic acid derivative as claimed in any of claims 1 to 7 or 10.

13. A process for combating the growth of unwanted plants, wherein a herbicidally effective amount of an (R)-2-(dibenzofuran-3-oxy)-propionic acid derivative as claimed in any of claims 1 to 7 or 10 is allowed to act on the plants and/or their habitat.

14. A process as claimed in claim 13, wherein the growth of broad-leaved weeds in a monocotyledon crop is combated by application of the (R)-2-(dibenzofuran-3-oxy)propionic acid derivative to the crop area.