DE3025559A1 - 2-Carboxy:phenyl-5-phenyl:imino-1,3,4-thiazolidine derivs. - plant growth regulants prepd. by acid-catalysed cyclisation of 1-carboxy:phenyl-4-phenyl-thiazolidine derivs. - Google Patents

Abstract

New 2-(2-carboxy-phenyl)-5-phenylimino -1,3,4-thiadiazolidine derivs. are of formula (I) (where R1 is H or 1-4 substituents selected from Cl, lower alkyl and lower alkoxy, R2 is H, lower alkyl, lower alkoxyalkyl, lower alkenyl, lower haloalkyl, or an agriculturally acceptable cation; R3 is H, lower alkyl, lower alkenyl, lower alkynyl, lower haloalkyl or benzyl; and R4 is H or one or more substituents selected from F, Cl, Br, CF3, lower alkyl and lower alkoxy). Depending on the rate of application and the species to which the cpds. are applied, (I) are plant growth regulants. Effects that can be obtained include promotion of tillering in oats and certain other grasses, increasing of fruit-set, and eradication of Digitaria sanguinalis (crabgrass).

Description

Phenyliminothiadiazolines,

their manufacture and their use as growth regulators for Plants It has been found that many chemical compounds have a growth regulating effect on plants Have an effect. Often there was a change in plant shape, a curvature and Folding of leaves, an inhibition of growth, leaf fall, a stimulation of root growth in cuttings and other effects have been observed. It is common necessary to reduce the growth-regulating compounds in a relatively small amount Use amount to achieve very clear growth-regulating effects.

With higher amounts, selective vegetation destruction is usually obtained, those in some plant species is greater than others. Growth regulators were in fact used more as selective herbicides than for other purposes, because in many cases the growth-regulating properties achieved by these substances Effects found no other practical application. It became a class now, however of growth regulating compounds have found a number of useful Create effects that differ from plant species to plant species. For example Some of these compounds promote shoot formation (branching at the foot of the plant) in oats and certain other grasses and an increase in the Fruit set with simultaneous destruction of Digitaria sanguinalis (crab grass).

Briefly, this class of growth regulating compounds is characterized by the general structural formula I. wherein R1 is hydrogen or one to four substituents selected from C1, lower alkyl and lower alkoxy, nitro, R2 hydrogen, lower alkyl, lower alkoxyalkyl, lower alkenyl, lower haloalkyl, or an agriculturally acceptable cation, R3 hydrogen, lower alkyl, lower alkenyl , lower alkynyl, lower haloalkyl or benzyl, and R4 is hydrogen or at least one substituent selected from 3,4-trimethylene, F, C1, Br, CF3, nitro, lower alkyl and lower alkoxy with the further condition that at least one ortho position is unsubstituted.

The terms "lower alkyl", "lower alkoxy", etc., as used above were used, mean C1-C5-alkyl, etc.

The method of regulating plant growth including the destruction of unwanted vegetation consists in the effect on plants, either by applying an effective amount of a compound of the above named compound class either on the seed, the soil or directly on it the plants.

Synthesis of the growth regulators The new compounds according to the Invention can be made by procedures based on the following are based on the syntheses given for illustration. All temperatures are in degrees C.

The thiadiazoline compounds of the present invention are expedient produced by ring closure of a class of thiosemicarbazides obtained by means of Processes can be produced, which are based on the special procedures below illustrated.

1. Synthesis of methylhydroqenphthalate 300 ml of methanol are given up once to 148 g (1.00 mol) of phthalic anhydride and heat the suspension obtained under reflux conditions and stirring for 36 hours; solution occurs during heating a. The solvent is removed and the product is crystallized from a mixture of ethyl acetate and hexane to give 114.6 g of the title compound (Lit .: Beilstein, 9,797; F 82.5 ° C, 840 C).

2. Synthesis of methyl hydrogen phthalate chloride 110.0 g (0.611 moles) of methyl hydrogen phthalate and 77.4 g (0.650 mol) of thionyl chloride are mixed in 200 ml of chloroform, whereby keeps the temperature below 300. After stirring for two hours at room temperature the system is heated under reflux conditions for five hours. The solvent it is distilled off under reduced pressure; the crude product (120.9 g) is used without further purification (Lit .: Beilstein, 9, 797; no constants).

3. Synthesis of 1- (2-carbomethoxybenzovl) -2-methyl-4-phenyl-3-thiosemicarbazide A solution of 45.3 grams (0.25 moles) of 2-methyl-4-phenyl-3-thiosemicarbazide and 19.8 g (0.25 mol) of pyridine in 800 ml of 1,2-dimethoxyethane is stirred at room temperature and adds 49.8 g (0.25 mol) of methylphthaloyl chloride dropwise over a period of two hours in 100 ml of 1,2-dimethoxyethane added.

The reaction mixture obtained is stirred for 16 hours at room temperature. At the end of this time, the contents of the flask are poured into ice water. The educated Collect solids to give 73.3 g (85%); F 153.5 - 1540 C.

The general procedure for the preparation of the phenyliminothiadiazolines according to the invention consists in the acid-promoted ring closure dehydration reaction of a compound of the general formula II Among the acidic reagents, concentrated sulfuric acid, trifluoroacetic anhydride and thionyl chloride have been found to be effective, the results obtained appearing to depend strongly on the nature of the R2, R3 and R4 substituents.

So far as has been determined, the best includes general ring closure reaction the use of concentrated sulfuric acid in conjunction with chloroform as Diluents as described in the following preparation of 5- (2'-carboxyphenyl) -2- (3'-fluorophenylimino) -3-methyl-1,3,4-thiadiazol-4-yne is illustrated.

Into a 3 liter three neck flask equipped with a mechanical Stirrer, thermometer, reflux condenser and dropping funnel that is immersed in an ice bath, a solution of 84.3 g (0.243 mol) of 1- (2'-carboxybenzoyl) -4- (3'-fluorophenyl) -2-methyl-3-thiosemicarbazide is stirred (F 155 - 70 C) in 1750 ml of chloroform, while standing over a period of 30 minutes slowly adding 404 g of concentrated sulfuric acid, keeping the temperature below Holds 250 C. A clear two-phase solution is obtained after about half of it which has added sulfuric acid. The mixture is stirred for a further two hours at room temperature and carefully pour the contents into a mixture of 800 ml of concentrated ammonium hydroxide and 2 kg of ice. The two-phase system obtained is stirred for 15 minutes and separated. The organic phase is discarded and the aqueous phase is stirred and cooled to 200.degree and acidified to pH 3 with 370 ml of glacial acetic acid, a solid precipitate being formed receives. The slurry is stirred for 30 minutes at 100 ° C. and filtered. The filter cake you rinse with two 300 ml portions of cold water, then slurry it in 750 ml cold water, filtered and air-dried, 65 g (81% Yield) of a product with a melting point of 207-80 ° C. is obtained.

The following are two specific procedures that to illustrate a small-scale laboratory method: making 2-Phenylimino-3-methyl-5- (2'-carboxyphenyl) -1,3,4-thiadiazol-4-yne To 25 ml H 2 SO 4 5 g (0.015 mol) of 1- (2'-carboxybenzoyl) -2-methyl-4-phenyl-3-thiosemicarbazide are added added. After stirring for 30 minutes at room temperature, crushed ice is added. The acidic solution obtained is washed with ethyl acetate and then made up with concentrated NH40H to a pH of 8. The precipitate is collected and washed with it cold water and dry it to give X.0 g (F 223-2250C).

Production of 2-phenylimino-3-methyl-5- (2'-carbomethophenyl) -1,3, 4-thiadiazole-4-in Using the same conditions as described above obtained from 5.0 g of 1- (2'-carbomethoxybenzoyl) -2-methyl-4-phenyl-3-thiosemicarbazide 1.3 g of the desired product, F 96-980 C.

Compounds prepared using the procedures described above are listed in Table I below. As can be seen from formula I, the radicals R¹ and R4 can occupy any free position on the ring; this applies in particular to R4 in the compounds nos. 3804 and 4016 given below. TABLE I Compounds of the formula I Verb.

No. R¹ R² R³ R4 F ° C Remarks on Usability 2812 H H CH3 H 223-225 promotes shoot formation in oats 3107 H H CH3 3-F 208-209 promotes the Shoot formation in oats 3291 H CH3 CH3 H 96-98 increased fruit set 3356 H H CH3 4-F 195-200 3357 H CH3 CH3 4-F 60-61 promotes sprouting in oats 3373 H CH3 CH3 4-OCH3 oil 3498 Cl4 CH3 CH3 H 142-146 3499 Cl4 allyl CH3 H 90-93 3801 H H CH3 2-CH3 141-143 increased fruit set 3802 H H "2-F 201-202 promotes sprouting with oats TABLE I (continued) Verb.

No. R¹ R² R³ R4 F ° C Notes on Serviceability 3803 H CH3 CH3 2-F 119-121 increased fruit set and sprout formation in oats 3804 H CH3 CH3 2-F 119-121 increased fruit set and sprout formation in oats 3804 H CH3 "4-CF3 87-88 increased fruit set 3840 H CH3 "4-NO2 101-102 increased fruit set 3841 H CH3 "3-Cl oil increased fruit set 3842 H CH3" 4-CH3 73-75 increased fruit set 3902 H H "3-NO2 178-180 increased shoot formation in oats 3903 H H" 3-CF3-157-158 increased Fruit set 4-Cl 3904 H H "2-CH3-147-148 increased shoot formation in 3-Cl oats 3905 H H "2-Cl 194-195" "for oats 3906 3-NO2 H" H 194-195 3908 H H "2-CH3- 183-185 6-Cl 3961 H H "2,5-Di-164-165 increased fruit set methyl 3965 H C2H5 "H 83-85" "4016 H H" 4-COCH3 197-198 increased shoot formation in oats TABEL I (continued) Verb.

No. R¹ R² R³ R4 F ° C Remarks on Usability 4058 H allyl CH3 H Oil increased fruit set and sprout formation 4059 H H "4-N (C2H5) 2 175-177 increased Shoot formation 4104 H H "2,4-dichloro 168-170" "4114 H H" 3-CH3 160-162 increased Fruit set and shoot formation 4171 H H "3-Br 164-165 increased shoot formation 4175 H H "4-CF3 211-213" "4177 H CH3" 4- (CH2) 3CH3 oil increased fruit set and sprout formation 4266 H CH3 "3-CH3 semi-solid increased fruit set and sprout formation in oats 4271 H H "3,4-tri- 180-182 increased fruit set methylene use of growth regulators With highly active compounds, phytotoxic compounds often occur Effects when applied before emergence and after emergence. These effects can be demonstrated using the sample methods below.

Pre-emergence application Paper cups approximately 6.35 cm (2.5 in.) Deep are filled with earth, with aqueous spray mixtures in a proportion of 5.61 kg of active ingredient per ha - (5 lbs / acre) of the sprayed area, sprayed with six species sown with seeds and then covered with about 6.35 mm (1/4 in.) of soil. the Spray mixes are made by adding the correct amount of the growth regulator compound Dissolve in 15 ml of acetone, add 4 ml of a solvent / emulsifier mixture, which from 60% by weight of a commercially available polyoxyethylated vegetable oil emulsifier (96 % By weight active ingredient, Emulphor EL-719), 20% by weight xylene and 20% by weight deodorized Kerosene consists, and then the total volume by adding warm water Bring 60 ml. The plants are checked 21 days after sowing and treatment, and the plant damage is assessed according to the following scheme: Degree of effect: 0 = no effect 1 = minor effect, plants recovering 2 = moderate effect, Damage 26 to 75% 3 = serious effect, damage 76 to 99% of the foliage 4 = maximum effect (all plants die).

Post-emergence anDlication Several species of plants are in Potting soil within Polystyrene pods grown, and tomatoes are grown in 10.16 cm (4 in.) pots in the greenhouse. Aqueous spray formulations are produced and the grown plants are sprayed at a spray volume of 561.3 Ltr / ha (60 gallons / acre) and an application rate of 5.61 kg / ha (5 lbs / acre) sprayed. The spray mixtures are prepared in the aforementioned manner. For comparison purposes plants are also at 561.3 Ltr / ha with one containing no growth regulator Spray mix sprayed. The plant damage is in turn according to the aforementioned Scheme evaluated, and the following growth regulation effects in experiments Achieved both before and after emergence: Abbreviation in the effect tables Forming effect on F new growth epinasty E growth reduction G necrosis N no emergence K Chlorosis C In Table II below are the observations with regard to the herbicidal and growth regulator effects achieved before and after emergence listed, which when using the growth regulators according to the invention according to the above procedures.

TABLE II Effects of Compounds on Plant Species Verb. No. Effect before leakage Effect after leakage 0 to ¢ me t to, SO "m t> ri 85 ls. °.> L. ~ ~~~ 0 0 0 2812 X4 R3G3 F3G3 F3G3 G3F1 K4 F2G1 P3G2 F2 F2 P3G1 F3G2 3107 K4 F2G2 F3G3 F3G3 F3G3 F3G3 N2G2 NlGl NlGl N1G2 N3G3 F2G3 3291 F3G3 F2G2 F3G3 F3G3 F1 F1G1 F1G1 F3G2 Fl NlF1 F3G3 F2 3356 - - - - - - - - - - - - 3357 K4 K4 F3G3 F3G2 F3G2 F3G2 F2G1 F2G3 F1 F2G2 F3G2 F4 3373 F1 0 F2G1 F2G1 0 F1. FlGl F2G1 F1 N1F2 F2G3 F2G1 3498 0 0 0 0 0 0 0 F1 G1 0 F2G1 Fl 3499 X2G1 F1 F2 Fl 0 F1 0 N1 0 0 F2 F1 F2 3801 X4 K4 F3G3 F3G3 F3G3 F3G2 F2G3 F2G2 N1G2 N1G2 - F2 Fl F2 3802 F2G2 K4 F3G3 F3G3 F3G3 F3G3 N1G2 N1G2 GlFl F2G2 - NlFl 3803 F1 FlGl F3G3 F2G2 F2G1 F2G2 0 F1 F2 F2G1 F3G1 N2F1 F2 3804 F1 FlGl K4 F3G2 F2G1 F2G1 G2 N4 F1 G1 N1G2 F3 3840 0 0 F1 0 0 0 0 0 0 OF1 F2G1 F1 Fl 3841 F2G2 F2G1 F3G2 F3G2 F3G2 F2G1 C1G2 F3G2 F2G1 C2G2 F2G2 F3N1 3842 F3G2 F2G1 K4 F3G2 F3G2 F2G2 F1 F3G1 FlGl FlGl F2G1 F2 3902 FlGl F2G2 K4 F3G2 F3G3 F3G2 F1 F3G3 F2G1 F2G2 F3G3 F2G2 3903 0 F1 F1 0 0 F2 0 F2G1 0 F1 F3G1 F2 3904 F1 F2 F3G3 F3G2 F3G2 F2G2 Pl F3G3 F1 F2G2 F3G3 F3G1 3905 F1 F2 F3G2 FlGl F2G2 F2G2 F1 F3G2 Plal FlGl F3G3 F2G1 TABLE II (continued) Effects of Compounds on Plant Species Verb. No, effect before leakage effect after leakage s C; 0 U tO tt o tO tO 0 FS 0 3 'F' 0 . *. m tO.t * .U 3 to o O v o, ¢ s 0 au e X ox t * E ut U 3 LO 0 3906 0 0 F2 0 0 Pl 0 Pl 0 0 F2G1 Pl 3907 F1 F2G1 F3G3 F2G2 F3G2 F2G2 F2G2 F1 FlGl P3G2 N4 F2 3908 0 0 K2 0 G1 0 0 0 0 0 N2 0 3961 E'2G2 F3G2 K4 F3G3 F3G3 F3G2 F2G2 F3G3 FlGl F2 N4 F3G1 G1 3965 F2G2 F2G2 F3G3 F3G2 F2G1 F2G1 FlCl F3G2 F1 F2cl F3G3 F3 4016 F2G2 Flight1 F3G2 F3G3 F2G2 F1G1 G2F2 F3G2 F2G2 F2G1 Plal F3 4058 F3G3 F2G2 F3G3 F3G3 F3G2 F3G2 F2G1 F3G2 F2G2 F2G1 F3G2 F2 4059 0 F1 F2 0 0 F1 F2G1 F3G1 FlGl FlGl F2G1 F2 4104 FlGl G2F1 F3G1 F2G1 F3G1 F3G1 G2 FlGl F1 N4 N4 F2 4114 F3G3 F3G2 F3G3 F3G3 F3G3 K4 N2G1 F3G3 F2G2 N4 N4 F3G2 4171 F1 F3G3 F3G2 F2G1 F2G2 F2G1 F2G2 F3G1 F2 F2G1 F3G3 F3 4175 F3G3 F3G3 F3G3 F3G3 F3G3 F3G2 F2G2 F3G2 F2 F2G2 F3G2 F3G1 4177 F2G2 F2G2 F3G3 F2G1 FlGl FlGl F1 F2 F2 P2 P2 F2 4266 F3G3 F2G2 F3G3 F3G3 F2G2 F3G2 F2G2 F3G3 F2G2 F2G1 F3G3 F3G1 4271 F3G3 F3G3 F3G3 F3G2 F3G2 F3G2 FlGl F3G2 F2G1 FlGl F3G2 F3 The use of numerous growth regulator compounds can be demonstrated using the treatment of soybeans (Soja max), in which the number of seed pods is increased, and in the treatment of tomato plants (Lycopersicum esculentum), in which the fruit set is increased. In an exemplary experiment, Soja max (Evans variety) and Lycopersicum esculentum (Tiny Tim variety) are grown in 10.16 cm (4 in.) Pots (one plant per pot). The pots are filled with greenhouse soil (2 parts good top soil, 1 1/2 parts construction sand, 1 1/2 parts peat, fertilized with 2.97 kg (5 lbs.) 12-12-6 fertilizer and 2.97 kg / m3 (5 lbs./cu.yd.) Finely ground limestone) filled. Aqueous spray preparations are made and the plants placed in the pots are sprayed at a spray volume of 374.2 l / ha (40 gallons / acre) and application rates of 1120, 280 and 70 g / ha (16, 4 and 1 oz./acre ) sprayed. The spray mixtures are prepared by dissolving the correct amount of the growth regulator compound in 15 ml of acetone, adding 2 ml of a solvent / emulsifier mixture which consists of 60% by weight of a commercially available polyoxyethylated vegetable oil emulsifier (96% by weight of active ingredient, Emulphor EL- 719), 20 wt .-% xylene and 20 wt .-% deodorized kerosene, and then the total volume by adding a 0.156 wt .-% aqueous solution of a liquid nonionic dispersant (90 wt .-% active ingredient trimethylnonyl polyethylene glycol ether, tergitol TMN-10) brings to 80 ml. Two copies are sprayed for all application quantities. For comparison purposes, plants are also sprayed with water at 374.2 liters / ha (40 gallons / acre). The number of seed pods and fruits as a percentage of the arithmetic mean of the numbers of untreated plants is determined within about 3 weeks after the spray treatment. The results are shown in Table II. The severity of the growth regulator effect on the plants is rated on a scale ranging from 0 to 10; the rating numbers are also shown in Table III.

TABLE III Growth regulating effects against two plant species Soja max Lycopersicum esculentum Verbin- Applicka- number of pods (1), growth- fruit- Amount of growth manure% in comparison regulating number (1) regulating no. g / ha to the untreated effect (2)% compared effect (2) (oz / acre) to the plants untreated plants 2812 1120 (16) 174 a 5.5 400 b 7.5 280 (4) 143 2.0 255 4.5 70 (1) 109 0 182 1 3107 1120 (16) 138 a 6.5 136 c 6 280 (4) 112 2.0 245 4 70 (1) 93 1 218 1 3291 1120 (16) 143 3.5 136 c 5.5 280 (4) 115 1.0 27 1.5 70 (1) 110 0 109 0 3801 1120 (16) 140 7.5 700 4.5 280 (4) 129 5 900 2 70 (1) 136 4 200 0 3802 1120 (16) 105 7 1100 7 280 (4) 136 1.5 800 4.5 70 (1) 122 1 800 3.5 TABEL III (continued) 3803 1120 (16) 119 5 800 3.5 280 (4) 87 2 700 3 70 (1) 94 0.5 400 0.5 3804 1120 (16) 143 8 900 6.5 280 (4) 115 5.5 700 3 70 (1) 87 3.5 800 1 3840 1120 (16) 84 1.5 200 0 280 (4) 101 0.5 200 0 70 (1) 105 0 100 0 3841 1120 (16) 119 7.5 700 5 280 (4) 108 5.5 800 4 70 (1) 105 1.5 500 1 3842 1120 (16) 133 7.5 700 6 280 (4) 108 3.5 800 2 70 (1) 119 0.5 800 1.5 4104 1120 (16) 138 1.5 214 3.5 280 (4) 121 0 182 2 70 (1) 125 0 118 1 4266 1120 (16) 114 5.5 175 4.5 280 (4) 114 3 225 2 70 (1) 97 1.5 113 1 (1) control = 100 (2) greenhouse rating on the scale from 0 (no effect) to 10 (complete dissolution) a smaller pods b malformed Fruit c stimulated growth The information from the ones given here Tables enable the person skilled in the art to make a selection among the growth regulator compounds according to the invention to meet and get a certain picture of the application quantities to make of the desired effect. It can be seen, for example, that complete Killing of certain plant species with application amounts as high as 5.61 to 11.22 kg / ha 5 to 10 lbs./acre) are often done while having beneficial effects as opposed to live plants at application rates of 1.12 kg / ha (1 lb./acre) or less can be determined.

The growth regulator compounds are usually used in combination with inert carriers or diluents, such as in aqueous spray preparations, granules and dusts, applied in accordance with conventional practice. A watery one Spray preparation is usually made by adding a wettable powder or an emulsifiable concentrate of a growth regulator with a relatively large Amount of water mixed to form a dispersion.

Wettable powders provide intimate, finely divided mixtures of growth regulator compounds, inert solid supports and surfactants. The inert solid support is usually selected from the group of attapulgite clays, kaolin clays, the Montmorillonite clays, diatomaceous earths, finely divided silica and purified Silicates. Effective surface-active agents that act as wetting agents, penetrants and dispersibility are common in wettable powder formulations present in proportions from 0.5 to about 10 wt. To the ones commonly used for this purpose Surfactants include the sulfonated lignins, naphthalene sulfonates and condensed Naphthalene sulfonates, alkylbenzenesulfonates, alkyl sulfates and nonionic surfactants such as condensation products of ethylene oxide with alkyl phenols.

Emulsifiable concentrates of the growth regulator compounds include in each case a solution of the growth regulator compound in a liquid carrier, which is a mixture of a water-immiscible solvent and surface-active substances Agents such as emulsifiers. Useful solvents include aromatic ones Hydrocarbons such as xylenes, alkylnaphthalenes, petroleum distillates, terpene solvents, Ether alcohols and organic ester solvents. Suitable emulsifiers, dispersants and Wetting agents can be selected from the same classes of products as they are used for Formulation of wettable powders can be applied.

In general, the growth regulator formulations expediently contain 0.1 to 95% by weight of a compound of the formula (I) and 0.1 to 75% by weight of a carrier or surfactant. The direct application on plant seeds However, planting can in some cases be done by powdering it solid growth regulator mixed with the seed to make a practically uniform one To achieve a coating which is very thin and only 1 or 2% by weight (or less), based on the weight of the seed. Most often, however, it will be a non-phytotoxic Solvents such as methanol as a carrier to facilitate uniform distribution of the growth regulator applied to the surface of the seed.

When a compound is to be applied to the earth, as is the case with an application before emergence is the case, granular preparations are sometimes more practical than spray preparations. Typical granules include Growth regulator compound dispersed in an inert carrier, e.g. in coarsely ground clay or clay obtained by treating a rolling bed of the powdered material with a small amount of liquid in a granulating drum was converted into a granulate. In the usual process for the production of granules a solution of the active ingredient is sprayed onto the grains while they are in a suitable mixing device are moved, after which the grains under constant Moving with a stream of air dries.

Claims (1)

PATENT CLAIMS 1. A method for regulating plant growth, including the control of weeds, by the action of an effective amount of the active ingredient on the plants, either by applying the active ingredient to the seeds, the soil or directly to the plants, characterized in that as active substance employs a compound of the following general structural formula wherein R1 is hydrogen or one to four substituents selected from C1, lower alkyl and lower alkoxy, R² is hydrogen, lower alkyl, lower alkoxyalkyl, lower alkenyl, lower haloalkyl, or an agriculturally acceptable cation, R³ is hydrogen, lower alkyl, lower alkenyl, lower alkynyl , lower haloalkyl or benzyl, and R4 is hydrogen or at least one substituent selected from F, C1, Br, CF3, lower alkyl and lower alkoxy with the further condition that at least one ortho position is unsubstituted. 2. Process according to Claim 1, characterized that one uses as active ingredient such as is given in Table I of the present description. 3. Connection of the general structural formula wherein R1 is hydrogen or one to four substituents selected from C1, lower alkyl and lower alkoxy, R2 is hydrogen, lower alkyl, lower alkoxyalkyl, lower alkenyl, lower haloalkyl, or an agriculturally acceptable cation, R³ is hydrogen, lower alkyl, lower alkenyl, lower Alkynyl, lower haloalkyl or benzyl, and R4 is hydrogen or at least one substituent selected from F, C1, Br, CF3, lower alkyl and lower alkoxy with the further condition that at least one ortho position is unsubstituted. 4. A compound according to claim 3, characterized in that there is a of the compounds listed in Table I. of the present description are specified. 5. Process for the preparation of a compound according to claim 3, characterized in that a compound of the general formula in which the radicals R1, R2, R3 and R4 have the meaning given in claim 3, subjected to an acid-promoted ring closure dehydration reaction. 6. The method according to claim 5, characterized in that the Ring-closing dehydration reaction in the presence of sulfuric acid, trifluoroacetic anhydride or thionyl chloride as an acid promoter. 7. The method according to claim 5 and 6, characterized in that one the ring closure dehydration reaction in the presence of sulfuric acid as a promoter and in the presence of chloroform as a non-reacting diluent. 8. The method according to claim 5 to 7, characterized in that one carries out the ring closure dehydration reaction at room temperature. 9. Formulation for agricultural purposes, marked thereby1 that it contains 0.1 to 95% by weight of a compound according to claim 3 as active ingredient.