CA1036616A - Herbicidal compounds - Google Patents

Abstract

Abstract of the Disclosure:

Compounds of the formula:

Ia wherein A is 4-chlorophenoxy or 2,4-dichlorophenoxy and R
is methyl, ethyl, n-propyl or n-butyl or when A is 4-chloro-phenoxy R additionally represents isopropyl, 2-methyl-n-propyl, n-hexyl, allyl, cyclohexyl, 2-methylcyclohexyl or cyclopentyl in form of their racemic mixtures, processes for preparing them and methods for controlling weeds with the said compounds.

Description

1~)3661~ ~ i The present application is a divisional of our copending Canadian Patent Application Serial No. 171,539 ~;
filed May 16, 1973.
The present invention relates to herbicidal compounds.
In German Offenlegungsschrift 1,668,896 option-ally substituted 4-phenoxy-phenoxy-alkane-carboxylic acids and derivatives thereof are disclosed and their action on ~-the lipide and cholesterin metabolism is described. Com-pounds of the aforesaid class are also the object of German Offenlegungsschrift 2,138,828.
It has surprisingly been found that a number of 4-phenoxy-phenoxy-~-propionic acid esters which are not expressly described in the above publications exhibit an excellent selective herbicidal effect against weed grasses in crop plants.
The present invention therefore provides the new compounds of the formula I

/~ ~0--jN--COOR Ia wherein A is 4-chlorophenoxy or 2,4-dichlorophenoxy and R is methyl, ethyl, n-propyl or n-butyl or when A is 4-chloro-phenoxy R additionally represents isopropyl, 2-methyl-n-propyl, n-hexyl, allyl, cyclohexyl, 2-methylcyclohexyl or cyclopentyl in form of their racemic mixtures.
The compounds of the invention are useful as selec-tive herbicides both in pre-emergence and in post-emergence application particularly against weed grasses, while broad '' i .
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leaved weeds are damaged to a small extent only. This special action on grasses contrasts with the action of chemically re-lated growth-promoting compounds of the phenoxy-alkane-carboxy-lic acid series (for example 2,4-dichlorophenoxy-acetic acid (2,4iD) and 2,4-dichlorophenoxy-propionic acid (2,4-DP), the principal effect of which is the destruction of broadwleaved weeds. Simu~t~leously, the novel compositions do no harm to ~icotyledonous (broad-leaved) crop plants.
~~ Surpri~ingly the composit~ons according to the invention do not damage crop grasses such as rice, barley, ~at, ar,d wheat; ~ -- ~Hence, the noYel compositions can be used to combat weed grasses in cereals, i.e. crop grasses, which has been very difficult so far. Moreover, weed grasses can be eff~ciently eontrolled in dicotyledonous crop plants, for example in sugar bee~leguminosae, celery, clover, lucerne, melon, cucumber, and tobacco.
Owing to this special action against weed grasses,above all foxtail grass, bent and the like, the novel compositions are superior to a number of kno~m herbicides such as alachlor, monolinuron9 linuron, pyrazon, phenmedipham, sodium trichloro-aeetate, and prynachlor, when applied in fields strongIy in-fested with weed grasses. ~oreover, the amounts necessary for a complete destruction of the weed grasses are much smaller than with the abvve kno~m herbicides. The amounts may vary ~Yithin ~5 wide limits~ for e~ample in the range of from 0.~ to 10 kg of active ingredient per hectare, preferably 0.2 to 5 kg per hectare.
- The compounds of formula I and the compositions containing 29 them have a low toxicity against warm-blooded animals.

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10366~6 The present invention therefore furthermore provides :~
a method for eradicating or controlling weed grasses in crop plants which comprises applying to the weeds or the habitat, -~
either before or after emergence of the weeds, an effective amount of one or more of the compounds of formula Ia as defined in claim 1.
The compounds of the invention are prepared by either - reacting a phenol of the formula:

A ~ O-H

wherein A is as defined in claim 1 with a compound of the formula:

CH
: 1 3 Hal CH COOR

wherein Hal is a halogen atom and R is as defined above; or reacting an acid chloride of the formula:

A ~ O - CH - COCl wherein A is as defined above with an alcohol of the formula:
ROH

wherein R is as defined above.

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:' , 1~)36616 - The herbi~id~l composltions used in the invention conta1n the acti~e ingre~ients of formula I generally in an amount of from

2 to 95 % by weight. They can be used in the form of wettable - powders, emulsifiable concentrates, sprayable solutions, dust~, or granules, in admixture with the usual formulation auxiliaries.
Wettable po~ders are preparations that can be uniformly dispersed in~water and contain, besides the active ingredient, a diluent or an inert substance, a wetting agent, for example polyoxethylated alkylphenols, polyoxethylated oleyl- or stearyl-O 10 amines, alkyl- or alkylphenyl sulfonates~and dispersing agents, for example the sodium saltsof lignin-sulfonic acid, 2,2'-dinaphthylmethane-6,6'-disul~onic acid, dibutyl-sulfonic acid or ~oleylmethyltaurine.
Emulsion concentrates are obtained by dlssolving the 1~ active ingredient in an organic solvent, ,or example butanol, - cyclohexanvn~, dimethyl~ormamide, xylene,or aromatic hydro-carbons hav7ng a higher boiling point. To obtain suspensions or emulsions in water having good proper-ties, wetting agent~
~ t'~ as specified above are also added.
; 20 Dusting powders are obtained by grinding the actlve ingredient with finely divided, solid substances, ~or example talc, natural clays such a~ kaolin, bentonite, pyrophillite, or diatomaceous earths.
Spraying solutions commercially available as aerosol sprays contain the active ingredient dissolved in an organic solvent, and in addition thereto a propellant, ~or example a mixture of fluorochlorohydrocarbons.
Granule~ can be produced by atomizing the active ingre~-29 ient on to an adsorptive, ~ranulated inert~material, or by ' ' ', ' ~ : ' : ~ ' " , .
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applying co~centrates of the ac~ive ingredient to the surface of a support, for example sand, kaolinite or a granula~ed inert material, with the aid of an adhesive, for example poly vinyl alcohol, the sodium salt of polyacrylic acid, or miner-al oils. Al~ernatively, suitable active ingredients may be made into granules, if desired ln admixture ~rith fertilizer~, in the manner commonly used for the manufacture of granulated fertilizers.
The commercial herbicidal preparations ~ontain varying concentrations of the active ingredients. In wettable powders - the concentration of active ingredient varies, for example, from about 10 to 95 ~, the remainder being the above formulation additives. Emulsion concentrates contain about 10 to 80 % of active ingredient r while dusting powders mostly contain 5 to 20 % of active ingredient and sprayable solutions about 2 to 20 %. In the case of granules, the content of active ingredient ` partially depends on whether the active ingredient is li~uid - or solid and on the type of granulation auxlliary or filler J ~3. u~ed. - .
For application- the commercial concentrates are optionally diluted in usual manner, the wettable powder or emulsifiable concentrate,for example with water. Dusts and granulated formulations as well as sprayable solutions are not diluted further ~itn an inert substance before their application. The amount applied varies with the external conditions, such as temperature, humidity and the like. In general, about 0.015 ; to 0.25 gramsand preferably about 0.03 to 0.12 gramSof active ~ ingredient per s~uare meter are used.
29 The herbicides acc-ording to the present invention may be - - combined ~ h other herbicldes and soil in~ec~icides.
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103~6~ ' ~ hen the active ingredients according to the invention are mixed with fertilizers, preparations are obtained which simultaneously have a fertilizing and a herbicidal effect.

. ~ , The following Examples illustrate the preparation of compounds of the invention:
Example 1 , :.:
4-(2',4~-Dichlorophenoxy)-~-phenoxy-propionic acid methyl ester `~
A solution of 64 g of 4-(2~,4~-chlorophenoxy)-phenol and 70 g of ~-bromopropionic acid ethyl ester in 100 ml of .: . .
butanone was refluxed for 10 hours together with 100 g of potas-sium carbonate. After separation from the inorganic salts by filtration, the filtrate was concentrated to dryness, the ester formed was taken up in methylene chloride, the solution was repeatedly extracted with water and the purified product was isolated by evaporating the organic solvent and purified by distillation under reduced pressure. 48 grams of 4-(2',4~-dichlorophenoxy)-o-phenoxy~propionic acid methyl ester boiling at 162-163 at 0.1 Torr were obtained.

Cl ~ Cl 0-CN-C00 C~3 Further compounds of the invention are prepared by proceeding as above or by a chemically equivalent process. Their properties are summarized in the following Table I.

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. E x a ~ ~ l e I - -- , -Seeds of some weed grasses and crop plants were so~.m Ln pots and a~'cr 3 weeks , in the 2- or 3-leaf-stage the plants ~ere spray~d with suspensions of the compounds of the in~enlion.
~ne results ob~ain~d 4 ~Jeeks after treatment are:..indicated in the fol1owing Table I,.
The results (and also the results of all following tables) ~ere e~alu~ed according to the following scheme in degree of damage in per cent:
. ' ,- ', .' ', ' nu~ber weeds -crop plants . . . . . ._._. _ _ .. .. _ .. _ '') 1 ' 100 ' o.
: 20 2 97~5 to' ~?OQ 0 ~o., 2,~
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- In this sche~e number 4 is still considered an acceptable 29 herbicidal effect in weeds and satisfactorly harmless . . on crop plants tcf. Bolle Nachrichtenbl~tt des Deutschen Pflan2ensc~-utzdienstes 16. 1964, pages 92 - 94).
~esults simi~ar to those with compound 6- of Table I ::~
~:ere obtained with compounds 2, 3, 4, 5, 7 and 12 ~ 2g The indicated results sho~r that with post emergence .
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applica~ion the compou~lds of the invention exhibited a good an~ in part ~xcellent effectin~ dosages against certain weed grasses without damaging dicotyledonous crop plants, such as, pea, sugar beetS sunflower, or soybean.
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C 10 In a greenhouse test the her~icidal effect and the tolerability by crop plants of compounds of the invention~.
were tested in pre-emergence and post-emergence application As comparative agent the kno~n herbicide a achlor was usedr The results indicated in TableIIIshow that in pre-emergence application compound 6 was superior to alachlor w~th the sa~e dosage of active ingredient. Cot-ton,soybean, and peanut were spared while cotton was damaged by alachlor.
-rn post-emergence application the compound o~ the inven-tion likewise exhibited a distinc' effect and did no harm to the crop plants, while alachlor was effective only in a higher dosage (0.62 kg/ha), but this effect was far from being satisfactory. Compounds Nrs. 2, 3, 4, 5, 7 and 8 had an analogo.u~- effect.
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E x a m l e III
4 Weeks old rice seedlings were planted in pots having a diameter of 15 cm into which seeds of Echinochloa crus-galli had previously been sown. One week after planting of the seedlings the pots were filled with water to a height of 1 cm abo~e soil surface. At that time the Echinochloa plants had already ger~inated.
Aqueous suspensions containing compounds of the invention as acti~e ingredient were added to the supernated water and 0 the mixture was cautiously stirred. 4 ~eeks a~ter treat~nt the following result was observed. (cf. Table IV).
Similar results were obtained with compounds Nrs. 2, 3, 4, 5, 8, 9, 12 and 13. The results demonstrate the~electivity of the claimed compounds in planted rice and thelr excellent effect on Echinochloa which is difficult ; to combat.
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Example IV 1~3661~
The weed grasses Avena fatua and Alopecurus myosuroides together with crop plants were sown in pots and after germination were sprayed with different dosages of compounds of the invention.
The results indicated in Table V show that compound No. 1 of the invention had an excellent effect on both Avena and Alopecurus~
with no or almost no damage to sugar beets and peas. The product oX Example I did only little damage to wheat and barley. The com-parative compound chlophenpropmethyl (~[4-chlorophenyl]-~-chloro-propionic acid methyl ester), which can be used for combating Avena fatua (wild oat) in various crops had an excellent effect on wild oat but was ineffective against Alopecurus (foxtail grass).
Compound Nos. 11 and 15 had an effect similar to that ofcompound 1 .;;
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Claims (19)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Compounds of the formula:

Ia wherein A is 4-chlorophenoxy or 2,4-dichlorophenoxy and R is methyl, ethyl, n-propyl or n-butyl or when A is 4-chlorophenoxy R additionally represents isopropyl, 2-methyl-n-propyl, n-hexyl, allyl, cyclohexyl, 2-methylcyclohexyl or cyclopentyl in the form of their racemates.

2. A process for the preparation of a compound of the formula Ia as defined in claim 1 which comprises either reacting a phenol of the formula:

wherein A is as defined in claim 1 with a compound of the formula:

wherein Hal is a halogen atom and R is as defined in claim 1; or (b) reacting an acid chloride of the formula:

wherein A is as defined above with an alcohol of the formula:
ROH
wherein R is as defined above.

3. A method for eradicating or controlling weed grasses in crop plants which comprises applying to the weeds or the habitat, either before or after emergence of the weeds, one or more of the compounds of formula Ia as defined in claim 1 in an amount sufficient to eradicate or control said weed grasses.

4. The compound according to claim 1 which is a racemic methyl 4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

5. The compound according to claim 1 which is a racemic ethyl 4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

6. The compound according to claim 1 which is racemic n-propyl 4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

7. The compound according to claim 1 which is racemic isopropyl 4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

8. The compound according to claim 1 which is racemic n-butyl 4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

9. The compound according to claim 1 which is racemic 2-methyl-n-propyl-4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

10. The compound according to claim 1 which is racemic n-hexyl 4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

11. The compound according to claim 1 which is racemic allyl 4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

12. The compound according to claim 1 which is racemic cyclohexyl-4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

13. The compound according to claim 1 which is racemic 2-methylcyclo-hexyl 4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

14. The compound according to claim 1 which is racemic cyclopentyl 4-[4-chlorophenoxy]-.alpha.-phenoxypropionate.

15. The compound according to claim 1 which is racemic ethyl 4-[2,4-dichlorophenoxy]-.alpha.-phenoxypropionate.

16. The compound according to claim 1 which is racemic methyl 4-[2,4-dichlorophenoxy]-.alpha.-phenoxypropionate.

17. The compound according to claim 1 which is racemic n-propyl 4-[2,4-dichlorophenoxy]-.alpha.-phenoxypropionate.

18. The compound according to claim 1 which is racemic n-butyl 4-[2,4-dichlorophenoxy]-.alpha.-phenoxypropionate.

19. A method for eradicating or controlling weed grasses in crop plants according to claim 3 which comprises applying to the weeds or their habitat, either before or after emergence of the weeds racemic methyl 4-[2,4-dichlorophenoxy]-.alpha.-phenoxypropionate in an amount sufficient to control or eradicate said weed grasses.