GB2125042A - Herbicidal cyclohexane-1,3- diones - Google Patents

Abstract

Substituted cyclohexane-1,3- diones having herbicidal activity against grassy weeds of the general formula: <IMAGE> R<1> is trans 3-chloroallyl or 4-chloro- benzyl, and R<5> is hydrogen, a cation, or <IMAGE> R<6> is alkyl of 1 to 6 carbon atoms, phenyl or naphthyl, are of particular advantage in that they have been found to possess excellent soil stability, especially in the case of the compound wherein R<1> is trans-3- chloroallyl.

Description

SPECIFICATION Herbicidal cyclohexane-1,3-diones This invention relates to novel derivatives of cyclohexane-1 ,3-dione having herbicidal properties which are useful as grassy herbicides in both pre- and post-emergent applications. In particular the compounds of the invention are characterised in having excellent soil stability.

The compounds of the invention are represented by the general formula:

wherein R is n-propyl; R' is trans 3-chloroallyl or 4-chlorobenzyl; one of R2 and R3 is hydrogen and the other is 2-ethylthiopropyl; R4 is hydrogen; and R5 is hydrogen, a cation, or

wherein R6 is alkyl of 1 to 6 carbon atoms, phenyl or naphthyl.

In terms of desirable phytotoxic properties, most preferably R1 is trans 3-chloroallyl. The salts, i.e.

the compounds in which R5 is a cation, are of interest since they have improved solubility and provide ease of formulation. The esters (R5 is COR6) are of interest because they hydrolyze in the field to the parent compound in which R5 is hydrogen.

Representative R5 groups are hydrogen, NH4+, Na+, K+, Ca++, acetyl, propionyl, butyryl, isobutyryl, isovaleryl, 3,3-dimethylbutyryl, benzoyl, 1-naphthoyl, and 2-naphthoyl. Preferably RS is hydrogen.

The compounds of the invention may be prepared according to the following scheme:

0 o o 9 B II v L + RCX(X=halo halt n( + HX (11 (II) (lea) tm) R\C/O lit AtCt3 0 OH (2) R2 Rk (ma)

The appropriate intermediates of formula IV may be made according to the following reaction sequence:

o o HUH + RlCl r NOR1 + HCl O O (i) (Va) (vet) 1. 1 Hydrazine H2NOR1 . HCt (5) 2. HCt (O Compounds of formula I wherein R5 is other than hydrogen may be prepared according to conventional procedures by treating the hydroxy compound (la) with an appropriate basic salt to yield compounds wherein R5 is Na+, NH4+, Ca++, etc. Similarly, the hydroxy compound (la) may be acylated by treatment with an appropriate acid halide to yield compounds wherein R5 is

Reaction (1) above may be performed at ambient temperature employing substantially equimolar amounts of the dione (II) and acid halide (Ila). Preferably the acid chloride (X=CI) is used. The reaction may be conducted in an organic solvent, such as, a halogenated hydrocarbon, ether or glycol. It is preferred that a base be present, such as an organic amine or alkali metal carbonate salt, in order to quench the hydrogen halide which is evolved.Preferred organic amines are pyridine and trialkylamines such as triethylamine. Pressure conditions are critical and atmospheric pressure may be conveniently employed.

Reaction (2) may be performed in an inert organic solvent, such as an halogenated hydrocarbon or ether. At least two moles of aluminium chloride per mole of ester Ill is used. Upon work-up, the crude product must be quenched with a proton-donor, preferably a mineral acid such as hydrochloric acid, to produce the trione Illa.

Reaction (3) is a conventional oxime-forming condensation. Since the hydrochloride salt is employed, it is first neutralized with a base, preferably an alkali metal alkoxide, before combining with the trione Illa or the free base from reaction 5 can be used directly. The reaction may be performed in an inert organic solvent, preferably a lower alcohol.

Reaction (4) is a conventional alkylation and may be performed in inert organic solvents such as dimethylsulphoxide, acetonitrile, ethers, glycol ethers or hydrocarbons. The reaction is performed in presence of a base, such as potassium carbonate, at ambient temperature.

Reaction (5) may be performed at elevated temperatures, preferably 30-1 000C. The phthalimide VI is preferably heated at atmospheric pressure with slight molar excess of hydrazine in an inert organic solvent, such as a lower alcohol, to reflux temperature. The crude mixture is then cooled and optionally quenched with a mineral acid, preferably hydrochloric acid, yielding the product salt (IV) or the free base can be used directly in reaction (3).

As an alternative to reactions (1) and (2) above, the trione Illa may be formed in one step by treating the dione II with the acid halide Ila in a halogenated hydrocarbon solvent, preferably carbon tetrachloride, in the presence of trifluoromethyl sulphonic acid. Typically, the reaction is performed at elevated temperature (30-1 000C) and is complete within 90 hours but yields a mixture of products.

Since the combined reaction time of reactions (1) and (2) is about 24 hours, and results in a purer product, the two-step sequence of reactions (1) and (2) is preferred to the one-step alternative.

The starting material of formula II can be prepared by known procedures or obvious modifications thereof (e.g. substitution of appropriate starting material). The compounds of formula II can be conveniently prepared by the following process schematically represented by the following overall reaction equations:

p2 0 U U 0 p)C=CHC1LH3 + cEo (A) CH3 + H2C (ffa) U U 0 0 Oi' CUH H R2 R3 R2 R3 {C) Jib wherein R4 is alkyl of 1 to 3 carbon atoms and R2 and R3 are as defined hereinabove.

These reactions are conventional type reactions and can be conducted in the usual manner. The first reaction step is typically conducted by contacting compound A with compound B and a base (e.g.

alkali metal alkoxides) under reactive conditions preferably in an inert solvent (e.g. an a[kanol such as ethanol). Typically, the reaction is conducted at from 60 to 1 100C using from 0.5 to 1.5 moles, preferably 0.9 to 1.1 moles, of compound A and of the base per mole of compound B.

In the second step the ester moiety of compound Ila is base hydrolyzed to the carboxylic acid, for example, by contacting metallic sodium in alkanol (e.g. ethanol) or alkali metal hydride at temperatures in the range of from 60 to 1 100C. By combining the reactants Steps (1 ) and (2) can be conducted together.

In the third step, compound C can be decarboxylated via treatment with a strong inorganic acid (e.g. hydrochloric acid, sulphuric acid). This step is typically conducted at temperatures in the range of 25 to 11 OOC and can be conveniently conducted in situ after completion of the base hydrolyzation, Step (2).

The compounds of formula Illa can also be prepared by reacting the compounds of formula II with the corresponding anhydride in the presence of an organic base, preferably in an excess of anhydride or inert organic solvent. Typically, this reaction is conducted at temperatures in the range of from 50 to 1 00C using from 5 to 0.5 moles of anhydride per mole of compound II.

The respective products of the above reactions can be isolated and purified by conventional techniques such as chromatography, distillation, crystallization, etc., when appropriate.

Definitions The terms "oxyaminoalkylidene" and "oxyiminoalkyl" refer to the radical having the formula --ON=RR- I wherein R is alkyl. For example, the terms "1 -allyloxyaminobutylidene" and "1-allyloxyiminobutyl" refer to the radical having the formula CH2=CH-CH20N=C(CH2)2CH3 I The compounds of formula I where R5 is hydrogen are generally referred to as cyclohexane-1,3diones rather than 3-hydroxycyclohex-2-en-1 -ones.

The following Examples illustrate the invention.

Example 1 Trans-2-[1 "(3-chloroallyloxyimino)butyl-5-(2-ethylthioprnpyl)cyclohexane-I ,3-dione (a) 86.6 g of crotonaldehyde were added dropwise to a mixture containing 64.0 g of ethanethiol and 2 ml of triethylamine in 500 ml of acetonitrile at room temperature (20--2 50C). The resulting mixture was stirred overnight (15 hours) at room temperature and then rotary evaporated to remove acetonitrile. The residue was dissolved in 300 ml of ethyl ether, washed twice with water, dried over magnesium sulphate and then concentrated by evaporation affording a yellow liquid concentrate of beta-ethylthiobutyraldehyde.

(b) A mixture containing 1 5.9 g of beta-ethylthiobutyraldehyde and 38.2 g of triphenylphosphoranylidene-2-propanone in 300 ml of methylene chloride was refluxed overnight and then evaporated affording a thick residue. The residue was mixed with hexane and filtered. The filtrate was evaporated under vacuum and the residue then distilled under vacuum affording 6-ethylthio-3hepten-2-one.

(c) 2.53 g of metallic sodium were added to 100 ml of ethanol at room temperature. To this was then added 17.6 g of diethyl malonate, with stirring, and then 17.2 g of 6-ethylthio-3-hepten-2-one were added. The resulting mixture was then refluxed for four hours and an aqueous sodium hydroxide solution, containing 9.5 g of sodium hydroxide in 75 ml of water, was then added and the mixture refluxed for another two hours. The mixture was cooled to 500C and then acidified by the addition of concentrated hydrochloric acid. The mixture was then warmed until decarboxylation was complete and then evaporated to a liquid residue. The residue was mixed with ethyl ether, washed with water, and evaporated to a brown liquid. The liquid was base, acid extracted affording 5-(2-ethylthiopropyl)cyclohexane-1,3-dione.

(d) 0.2 g of metallic sodium was dissolved in 1 ml of methanol and then added to 3.2 g of 5-(2 ethylthiopropyl)cyclohexane-1 ,3-dione. 20 ml of butyric anhydride were added and the mixture then refluxed for three hours. The mixture was then evaporated and the residue mixed with methylene chloride and then extracted with aqueous 5 wt % sodium hydroxide. The base extract was washed with methylene chloride, then acidified with concentrated hydrochloric acid and then extracted into methylene chloride. This was then evaporated affording 2-butyryl-5-(2-ethylthiopropyl)cyclohexane 13-dione.

(e) 0.38 g of sodium methoxide, 10 ml of methanol, and 1.0 g of 3-chloroallyloxyamine hydrochloride (H2N0CH2-CH=CHCl) were admixed together and then stirred for 10 minutes at room temperature. 2 g of 2-butyryl-5-(2-ethylthiopropyl)cyclohexane-1 ,3-dione were added and the resulting mixture stirred for about two days at room temperature. The mixture was then concentrated by evaporation and the concentrate mixed with 60 ml of diethyl ether and 40 ml of water. The ether layer was extracted with 40 ml of aqueous 2 wt. % sodium hydroxide solution, washed with 20 ml of water, dried over an hydros magnesium sulphate and evaporated affording a minor amount of the desired compound as the trans isomer.

The 2% sodium hydroxide solution extract was acidified to about pH 1 with aqueous 6N hydrochloric acid and then extracted with 100 ml of methylene chloride. The organic layer was washed with 40 ml of water, dried over magnesium sulphate and then evaporated affording the trans isomer of the desired compound as the residue. The major portion of the desired compound was recovered from the sodium hydroxide extract.

Example 2 This example iilustrates the preparation of the acyloxy compounds of the invention.

To a reaction mixture containing 3.0 g (0.01) mol of 2-[1 -(3'-chloroallyloxyamino)butylidene]-5 (2-ethylthiopropyl)cyclohexane-1 ,3-dione and 0.87 gm (0.11 mol) of pyridine in 20 ml of methylene chloride stirred at OOC were added 0.89 gm (0.11 mol) of acetyl chloride. The mixture was then stirred at room temperature for 2 hours. The mixture was then worked up by washing with water, drying with anhydrous magnesium sulphate, and filtered. The filtrate was evaporated under vacuum affording 3acetyloxy-2-[1 -(3'-chloroallyloxyamino)butylidene]-5-(2-ethylthiopropyl)cyclohex-2-en-1 -one.

Similarly, by following the same procedure, the corresponding 3-acetyloxy derivative of the other product listed in Table A hereinbelow was prepared.

Example 3 This example illustrates the preparation of the salts of the present invention.

To 3.0 gm (0.01 mol) of 2-[1-(3'-chloroallyloxyamino)butylidene]-5-(2-ethylthiopropyl)- cyclohexane-1 ,3-dione in 10 ml of acetone were added 0.4 gm (0.01 mol) of sodium hydroxide dissolved in 2 ml of water. The solvents were evaporated under vacuum affording the 3-hydroxy sodium salt of 2-[ 1 llyloxyamino)butylidene]-3-hydroxy-5-(2-ethylthiopropyi)cyclohex-2- en-i-one.

Similarly, by following the same procedure, the sodium salt of the other product listed in Table A hereinbelow was prepared.

Utility The compounds of the present invention are, in general, herbicidal in both pre- and postemergent applications. For pre-emergent control of undesirable vegetation, the herbicidal compounds will be applied in herbicidally effective amounts to the locus or growth medium of the vegetation, e.g., soil infested with seeds and/or seedlings of such vegetation. Such application will inhibit the growth of or kill the seeds, germinating seeds and seedlings. For post-emergent applications, the herbicidal compounds will be applied directly to the foliage and other plant parts. Generally, the herbicidal compounds of the invention are especially effective against grassy weeds and by proper dosage regulation can be safely applied for the control or prevention of grasses in broad leaf crops. The compounds of the invention are unique in that they exhibit excellent soil stability.This is particularly advantageous for pre-emergence application.

The compounds, when applied to growing plants above the ground in such an amount that the compounds will not kill beneficial plants, also show efficient plant growth regulating or retarding effects and may be advantageously employed, for example, to prevent or retard the growth of lateral buds in plants and to promote the thinning out of superfluous fruits in various fruit trees.

The compounds can be applied in any of a variety of compositions. In general, the compounds can be extended with a carrier material of the kind used and commonly referred to in the art such as inert solids, water and organic liquids.

The compounds will be included in such compositions in sufficient amount so that they can exert an herbicidal or growth-regulating effect. Usually from 0.5 to 95% by weight of the compounds are included in such formulations.

Solid compositions can be made with inert powders. The compositions thus can be homogeneous powders that can be used as such, diluted with inert solids to form dusts, or suspended in a suitable liquid medium for spray application. The powders usually comprise the active ingredient admixed with minor amounts of conditioning agent. Natural ciays, either absorptive, such as attapulgite, or relatively non-absorptive, such as china clays, diatomaceous earth, synthetic fine silica, calcium silicate and other inert solid carriers of the kind conventionally employed in powdered herbicidal compositions can be used. The active ingredient usually makes up from 0.590% of these powder compositions. The solids ordinarily should be very finely divided. For conversion of the powders to dusts, talc, pyrophyllite, and the like, are customarily used.

Liquid compositions including the active compounds described above can be prepared by admixing the compound with a suitable liquid diluent medium. Typical of the liquid media commonly employed are methanol, benzene, toluene, and the like. The active ingredient usually makes up 0.5 to 50% of these liquid compositions. Some of these compositions are designated to be used as such, and others to be extended with large quantities of water.

Compositions in the form of wettable powders or liquids can also include one or more surfaceactive agents, such as wetting, dispersing or emulsifying agents. The surface-active agents cause the compositions of wettable powders or liquids to disperse or emulsify easily in water to give aqueous sprays.

The surface-active agents employed can be of the anionic, cationic or nonionic type. They include, for example, sodium long-chain carboxylates, alkyl aryl sulphonates, sodium lauryl sulphate, polyethylene oxides, lignin sulphonates and other surface-active agents.

When used as a pre-emergent treatment, it is desirable to include a fertilizer, an insecticide, a fungicide or another herbicide.

The amount of active compound or composition administered will vary with the particular plant part or plant growth medium which is to be contacted, the general iocation of application-i.e., sheltered areas such as greenhouses; as compared to exposed areas such as fields-as well as the desired type of control. Generally for both pre- and post-emergent herbicidal control, the compounds of the invention are applied at rates of 0.2 to 60 kg/ha, and the preferred rate is in the range 0.5 to 40 kg/ha. For plant growth regulating or retarding activity, it is essential to apply the compounds at a concentration not so high as to kill the plants. Therefore, the application rates for plant growth regulating or retarding activity will generally be lower than the rate used for killing the plants.

Generally, such rates vary from 0.1 to 5 kg/ha, and preferably from 0.1 to 3 kg/ha.

Herbicidal tests on representative compounds of the invention were made using the following methods.

Pre-emergent herbicidal test An acetone solution of the test compound was prepared by mixing 500 mg of the compound, 1 58 mg of a nonionic surfactant and 20 ml of acetone. Twenty ml of this solution was added to 80 ml of water to give the test solution.

Seeds of the test vegetation were planted in a pot of soil and the test solution was sprayed uniformly onto the soil surface at a dose of 27.5 micrograms/cm2. The pot was watered and placed in a greenhouse. The pot was watered intermittently and observed for seedling emergence, health of emerging and seedlings, etc., for a 3-week period. At the end of this period, the herbicidal effectiveness of the compound was rated based on the physiological observations. A 0to1 00 scale was used, 0 representing no phytotoxicity, 1 00 representing complete kill. The results of these tests appear in Table In follow-up tests, the procedure above was repeated using diluted test solution which was sprayed onto the soil surface at various dosages. The results of these tests appear in Table II.

Post-emergent herbicidal test The test compound was formulated in the same manner as described above for the pre-emergent test. This formulation was uniformly sprayed on 2 similar pots of 24-day-old plants (approximately 1 5 to 25 plants per pot) at a dose of 27.5 micrograms/cm2. After the plants had dried, they were placed in a greenhouse and then watered intermittently at their bases, as needed. The plants were observed periodically for phytotoxic effects and physiological and morphological responses to the treatment.

After 3 weeks, the herbicidal effectiveness of the compound was rated based on these observations. A 0to1 00 scale was used, 0 representing no phytotoxicity and 100 representing complete kill. The results of these tests appear in Table I.

In follow-up tests, the procedure above was repeated using diluted test solution which was sprayed onto the soil surface at various dosages. The results of these tests appear in Table II.

Table A Compounds of the formula:

Analysis C H N No. R R1 mp OC Cain. Found Cain. Found Cain. Found 1 CH3CH2CH2- -CH2CH=CHCl oil 57.82 57.03 7.55 7.42 3.76 3.72 (trans) 2 CH3CH2CH2- - CH- CI oil 62.32 61.54 7.13 7.14 3.30 2.93 Table 1-Herbicidal activity Pre/post % control (27.5 gamma/cm2) No. L M P C W O 1 0/40 0/20 0/0 100/100 100/100 100/100 2 0/30 0/10 0/18 100/100 100/100 100/100 Table Il-Herbicidal activity Pre/post % control (rate in gamma/cm2) No. Rate Soybeans Rice L M P C W O 1 4.4 2/0 100/100 0/0 0/0 0/0 94/97 100/100 99/100 1.8 0/0 100/100 0/0 0/0 0/0 95/90 100/100 96/100 0.7 0/0 99/100 0/0 0/0 0/0 73/58 98/98 85/100 0.28 0/0 73/82 0/0 0/0 0/0 13/15 58/90 73/87 2 4.4 5/0 98/100 0/0 0/0 0/0 93/75 100/100 99/100 1.8 2/0 87/100 0/0 0/0 0/0 33/58 100/100 92/100 0.7 0/0 57/97 0/0 0/0 0/0 0/15 98/98 77/98 0.28 0/0 0/62 0/0 0/0 0/0 0/0 10/92 62/82 L=Lambsquarter (Chenopodium album) M=Mustard (Brassica arvensis) P=Pigweed 1Amaranthus retroflexus) C=Crabgrass (Digitaria sanguinalis) W=Watergrass (Echinochloa crusgalli) O=Wild oats (Avenua fatua)

Claims (14)

Claims

1. Compounds represented by the general formula:

wherein R' is trans 3-chloroallyl or 4-chlorobenzyl, and R5 is hydrogen, a cation, or

wherein R6 is alkyl of 1 to 6 carbon atoms, phenyl or naphthyl.

2. Compounds as claimed in Claim 1, wherein R5 is hydrogen.

3. Trans-2-[1 -(3-chloroallyloxyimino)butyl]-5-(2-ethylthiopropyl)cyclohexane-1 3-dione.

4. Compounds as claimed in Claim 1, wherein R5 is a cation.

5. Compounds as claimed in Claim 4, wherein R5 is NH4+, Na+, K+, or Ca++.

6. Compounds as claimed in Claim 1, wherein R5 is COR6 and R6 is acetyl, propionyl, butyryl, isobutyryl, isovaleryl, 3,3-dimethylbutyryl, benzoyl, 1 -naphtholy or 2-naphthoyl.

7. Trans-3-acetyloxy-2-[1 -(3'-chloroallyloxyamino)butylidene]-5-(2-ethylthiopropyl)cyclohex-2- en-1 -one.

8. The 3-hydroxy sodium salt of trans-2-[l -(3'-chlornallyloxyamino)bulidene]-3-hydrnxy-5-(2- ethylthiopropyl)cyclohex-2-en-1 -one.

9. A compound in accordance with Claim 1 , substantially as described in any one of the foregoing Examples.

10. A herbicidal composition comprising a biologically inert carrier and a herbicidally effective amount of a compound as claimed in Claim 1.

11. A composition as claimed in Claim 10, wherein said compound is the compound claimed in Claim 3.

12. A method of killing vegetation which comrpises appiying to said vegetation or its growth environment a herbicidally effective amount of a compound as claimed in Claim 1.

13. A method of killing crabgrass, watergrass or wild oats which comprises applying thereto or to its growth environment a herbicidally effective amount of a compound as claimed in Claim 1.

14. A method according to Claim 13, wherein said compound is the compound claimed in Claim 3.