CH627729A5 - Process for the preparation of a new phenoxyacetic acid ester and plant growth regulating composition containing the said ester - Google Patents

Description

The present invention relates to a process for preparing a new ester useful in agriculture, to its application as a regulator of plant growth and to compositions containing it.

The licensee's research and experiences have enabled it to discover that propyl 3-t-butylphenoxyacetate, of the formula:

(CÏÏ3) 3C

has interesting properties for regulating plant growth when applied to actively growing or dormant plant tissues and can be used to favorably influence the growth of economically advantageous plants, for example by improving the quantity or the quality of the crop obtained, by allowing the cultivator to conveniently achieve better control of the growth processes or by facilitating the handling and in particular the mechanical handling of the crop, for example during harvesting. Depending on the application dose and the growth stage of the treated plant tissue, the supply of propyl 3-t-butylphenoxyacetate can stimulate, promote or inhibit plant growth.

For example, the application of the compound of formula I has the following effects.

A. It increases the yield of fruit trees, for example bearing apples, pears, cherries, plums, citrus fruits or palm kernels, (i) by improving the shape of the tree, by promoting the departure of buds anticipated on 1-year-old trees in the nursery by reduction of apical growth without removal of the apical bud and by induction of vigorous lateral branching above the point of application (usually up to the last 20 to 50 cm of the tree), with a wide angle between its lateral branches and the trunk and / or by production of secondary lateral branches in trees 2 to 3 years after planting in the orchard, by treatment during the annual period of vigorous growth, (ii) in the case of fruit trees, such as apple, pear, cherry and plum, by reducing the period of vegetative growth before producing an appreciable harvest after planting the nursery in the orchard, generally al from 2 years to 1 year, in the case of apple trees, by treating the trees as described in (i).

For these purposes, namely A (i) and A (ii), propyl 3-t-butylphenoxyacetate can be applied with advantage in the form of spray compositions and similar compositions containing 750 to 1500 ppm of this compound.

B. It improves the shape of ornamental plants both grown in containers, for example Cornus spp (dogwood), and ornamental trees in nurseries, for example Acer spp (sycamore), by promoting vigorous bush growth and, in the case of trees, the departure of the anticipated buds. To this end, propyl 3-t-butylphenoxyacetate can be applied with advantage in the form of spray compositions and similar compositions containing 750 to 4000 ppm of this compound.

C. It improves the quality of fruits, especially apples and grapes, by thinning at the full flowering stage, at that of young knotted fruits and intermediate stages, by treatment at these stages of growth. To this end, propyl 3-t-butylphenoxyacetate can be applied with advantage in the form of spray compositions and similar compositions containing 250 to 1500 ppm of this compound.

D. It improves the yield of crops, for example cotton, soybeans, faba beans, baby beans, peanuts, rapeseed and sunflowers, especially by treatment at the flowering stage, for example for a crop of cotton. To this end, propyl 3-t-butylphenoxyacetate can be applied with advantage in doses of 0.56 to 2.24 kg of this compound per hectare.

E. It chemically disbuds young plants, for example the tea plant, promoting lateral growth. To this end, propyl 3-t-butylphenoxyacetate can be applied with advantage in the form of spray compositions and similar compositions containing 750 to 3000 ppm of this compound.

F. It causes defoliation of trees in the nursery (i) by treatment at the end of the growing season, which facilitates transplantation and the fight against diseases, for example on ornamental trees and shrubs, for example for roses and Quercus rubra (red oak), as well as on fruit trees, for example apple trees, in addition to bushes or hedges, etc., (ii) by treatment before flowering, for example for jasmine, so as to increase the yield floral by bush.

For these various purposes, namely F (i) and F (ii), propyl 3-t-butylphenoxy-acetate can be applied with advantage in the form of spray compositions and similar compositions containing 1000 to 10000 ppm of this compound.

G. It increases the number and yield of potato tubers. To this end, propyl 3-t-butylphenoxyacetate

5

10

15

20

25

30

35

40

45

50

55

60

65

627729

4

can be applied with advantage in the form of spray compositions and similar compositions containing 1000 to 3000 ppm of this compound.

H. It improves the yield and reduces losses in the Brussels sprout crops by treatment when the sprouts are formed, by replacing manual removal of the apical part of the plant. To this end, propyl 3-t-butylphenoxyacetate can be applied with advantage in the form of spray compositions and similar compositions containing 4000 to 6000 ppm of this compound.

I. It suppresses unwanted lateral growth, for example lateral shoots, on tomato plants. To this end, propyl 3-t-butylphenoxyacetate can be applied with advantage in the form of spray compositions and similar compositions containing 3000 ppm of this compound.

J. It increases the yield of monocot crops (such as wheat, barley or rice), by increasing the number of tillers and / or by lowering the number of blind ears (for rice). To this end, propyl 3-t-butylphenoxyacetate can be applied with advantage in the form of spray compositions and similar compositions containing 200 to 2000 ppm of this compound.

The interesting plant growth regulating properties of propyl 3-t-butylphenoxyacetate applied to growing plant tissues have been illustrated, for example, in the representative experiments described below.

| o Experience 1:

At the beginning of summer, a liquid containing 850 ppm of propyl 3-t-butylphenoxyacetate is obtained until it is run off onto fruit trees 70 m high, obtained by dilution with water. a liquid composition described in Example 5. The effect

15 exerted on the growth of the lateral branches of the trees, the comparison being established with untreated controls, is assessed at the beginning of the following spring and the results, expressed by the averages recorded on 7 trees for each treatment, are given in Table I.

Tree

Variety

Number of side branches at least 5 cm long

Untreated witness

Treated tree

Pear tree

Comice

1.1

3.7

Apple tree

Bramley

1.3

6.2

Apple tree

Red miller

2.8

6.7

Apple tree

Spartan

1.0

3.3

This experiment demonstrates the increase in the number of bran 900 ppm of propyl 3-t-butylphenoxyacetate obtained by side ches following the application of 3-t-butylphenoxyacetate dilution with water of a liquid composition described in Example 5 of propyl on apple and pear trees. and the treatment is repeated in early summer 2 years later. The average number of bouquets of flowers per tree in the spring of the year following the second treatment is determined by establishing Experiment 2. 40 ja comparajson with trees which have undergone disbudding.

At the beginning of the summer, we spray until runoff on classics by hand. The results obtained are collected in apple trees in the Bramley variety nursery, a liquid containing table II.

Table II

Average number of bouquets of flowers per tree at the time of observation

Terminal and branch bouquets

Axillary bouquets

Hand disbudding

6.14

2.42

Chemical disbudding

32.43

7.29

This experiment demonstrates the increase in the number of lateral branches and the improvement in the shape of the tree, resulting in an increase in the number of bouquets of flowers as a result of the application of propyl 3-t-butylphenoxyacetate to apple trees. 2 and 3 years old, the comparison being made with untreated witnesses who underwent conventional manual budding.

the increase in cotton yield, per hectare, by comparison with untreated controls, at the time of harvest, the results obtained being collated in Table III.

(Table at the top of the next page)

Experiment 3: This experiment demonstrates the increase in yield in

A liquid composition described in Example 65 cotton is diluted with water following treatment with 3-t-butylphenoxyacetate.

5 and it is applied in doses of 0.56 kg, 1.12 kg and 2.24 kg of propyl.

Propyl 3-t-butylphenoxyacetate per hectare in a cultivation according to the process according to the invention, the cotton compound, 2 or 4 weeks after full flowering. We appreciate formula I obtained by reaction of a compound of general formula:

5

Table III

627729

Treatment

Time of treatment (number of weeks after full flowering)

2 weeks cotton (kg / ha)

4 weeks cotton (kg / ha)

0.56 kg / ha

999

1086

1.12 kg / ha

1156

1064

2.24 kg / ha

958

1014

Untreated witness

804

804

0CH2C0X

II

(ch3) 3c where X represents the hydroxyl radical, a halogen atom and preferably chlorine or an alkoxy radical of 1 to 6 carbon atoms other than a propoxy radical, with propanol. 30

The reaction of the compound of formula II where X represents a hydroxyl radical with propanol can be carried out in the presence of an acid catalyst, such as hydrogen chloride gas, sulfuric acid or p-toluenesulfonic acid, optionally in the presence of an inert organic solvent, for example toluene, or else in an excess of propanol constituting the solvent, in a substantially anhydrous medium, at an elevated temperature, for example from 80 to 120 ° C., and preferably at the temperature of reflux of the reaction mixture.

The reaction of a compound of formula II, where X represents a halogen atom, with propanol can be carried out, optionally in the presence of an acid-accepting agent, for example triethylamine or pyridine , optionally in the presence of an inert organic solvent, for example carbon tetrachloride, chloroform or toluene, at room temperature or at an elevated temperature, for example reaching 120 ° C., and preferably at 45 the reflux temperature of the reaction mixture.

The transesterification of a compound of formula II where X represents an alkoxy radical other than the propoxy radical with propanol can be carried out in the presence of an acid catalyst, for example hydrogen chloride gas, sulfuric acid or the p-toluene sulfonic acid, optionally in the presence of an inert organic solvent, or in an excess of propanol constituting the solvent, in a substantially anhydrous medium at an elevated temperature, for example from 60 to 120 ° C., and preferably at the reflux temperature of the reaction mixture. 55

According to another process, the compound of formula I can be prepared by reaction of a compound of general formula:

III

(CH3) jO

where M represents an alkali metal atom, for example sodium or potassium, with a compound of general formula:

YCH, COOR IV

where Y represents a halogen atom, for example chlorine, and R represents an alkyl radical of 1 to 6 carbon atoms, then, when the reagent of general formula IV is not a compound in the formula of which R represents the propyl radical, by transesterification as described above.

The reaction between the compounds of general formulas III and IV can be carried out in the presence of an anhydrous inert organic solvent, for example dimethylformamide or propanol, at a temperature of 0 to 100 ° C.

The compound of formula II where X represents the hydroxyl radical can be obtained by application or adaptation of known methods for the synthesis of phenoxyacetic acids.

The compounds of formula II where X represents a halogen atom can be obtained by application or adaptation of known methods for the synthesis of acid halides from carboxylic acids by means of the compound of formula II where X represents a hydroxyl radical.

The compounds of formula II where X represents a halogen atom can optionally be used in the unpurified state.

The compounds of formula II where X represents an alkoxy radical other than the propoxy radical can be obtained by application or adaptation of known methods for the synthesis of esters of carboxylic acids, for example the methods described above with regard to the preparation of the compound of formula I.

The compounds of formula III can be prepared from 3-t-butylphenol, which is a known compound, by application or adaptation of known methods for the synthesis of alkali metal salts of phenols.

The compounds of formula IV can be prepared by application or adaptation of the known methods for the synthesis of monohalogenoacetic acid esters.

By known methods is meant, for the purposes of the invention, methods which have already been applied or described in the specialized literature.

The subject of the invention is also a process for regulating the growth of plants, for example of the genus described above, according to which an effective amount of the compound of formula I is applied to tissues in active growth or in dormancy of the plant. To this end, it can be used alone or in the form of a composition which regulates plant growth, that is to say in combination with one or more compatible diluents or vehicles suitable for incorporating such compositions, for example as described below.

Suitable application techniques include the following:

1) on fruit trees aged 1 year in the nursery by directed spraying, in particular by spraying at very low volume, and in foam, and

627729

6

2) on growing plants, by spraying on foliage and stems.

Especially important processes are:

1) a process for promoting the departure of the anticipated buds on fruit trees aged 1 year in the nursery and in particular on apple and pear trees, by application of the compound of formula I, preferably in the form of a composition, for example to be sprayed which contains 0.075%, or 750 ppm, to 0.15%, or 1500 ppm by weight, of the compound of formula I, over the last 20 to 50 centimeters of the growing upper part until runoff in the case of sprays other than very low volume, for example at the rate of a maximum of 501 of liquid composition to be sprayed per hectare;

2) a process for producing secondary lateral branches on fruit trees 2 and 3 years old after planting in the orchard by application of the compound of formula I, preferably in the form of a composition, for example by spraying, containing 0.125 %, or 1250 ppm, at 0.15%, or 1500 ppm, by weight, of the compound of formula I, until runoff in the case of the compositions to be sprayed.

A subject of the invention is also liquid compositions suitable as regulators of plant growth which contain as active ingredient the compound of formula I in combination with one or more diluents or adjuvants compatible with the compound of formula I and suitable for incorporation of such compositions.

The liquid compositions in accordance with the invention can be presented in the form of solutions, suspensions and emulsions of the compound of formula I which preferably comprise wetting, dispersing or emulsifying agents. These emulsions, suspensions and solutions can be prepared using aqueous, organic-aqueous diluents, such as acetophenone, cyclohexanone, isophorone, toluene, xylene, dimethylformamide and mineral, animal and vegetable oils ( these diluents can be mixed together) which may contain wetting, dispersing or emulsifying agents of ionic or nonionic type, optionally in mixture, such as those described below. When desired, emulsions or solutions containing the compound of formula I can be used in the form of self-emulsifying or self-dissolving concentrates which contain the active ingredient in solution in emulsifying or wetting agents or in solvents containing emulsifying agents or wetting agents with the active ingredient, a simple addition of water to such concentrates giving ready-to-use compositions.

The wetting, dispersing and emulsifying agents which may be contained may be of the ionic or nonionic type and may be, for example, sulforicinoleates, quaternary ammonium derivatives or products based on condensation products of ethylene oxide with nonylphenol and / or octylphenol, or esters of anhydrosorbitol carboxylic acids which have been made soluble by etherification of free hydroxyl radicals by condensation with ethylene oxide, these agents can also be mixed together .

The compositions suitable for the production of foams containing the compound of formula I also come within the scope of the invention.

The compositions according to the invention may also contain auxiliary compounds and they may contain mixtures of the auxiliary compounds with compounds of formula I in the form of combined preparations or mixtures to be diluted. Examples of these auxiliary compounds are in particular insecticides, such as organophosphorus esters such as parathion or OO-diethyl and O-4-nitrophenyl phosphorothionate, mala-thion or phosphorothiolothionate of S- [1,2-di- (ethoxycarbonyl) ethyl] and OO-dimethyl, vamidothion or phosphorothiolate of 0.0-dimethyl and S- [2- (1-methylcarbamoylethylthio) ethyl], diazinon or phosphorothionate of 0.0-diethyl and O- [2-isopropyl-6-methylpyrimidine-4-yle], monocrotophos or cis-

0,0-dimethyl l-methyl-2- (N-methylcarbamoyl) vinylphosphate, 0,0-dimethyl and S- (N-methylcarbamoylmethyl) dimethoate or phosphorothiolothionate, S- (6-chloro phosalone or phosphorothiolothionate -2-oxobenzoxazoline-3-yl) methyl and OO-diethyl, bromophosethyl or phosphorothionate of 0- (4-bromo-2,5-dichlorophenyl and 0,0-diethyl, carbamates such as carbaryl or N- 1-naphthyl methylcarbamate, formetanate or N-methylcarbamate of 3-dimethylaminomethyleneiminophenyl, both natural and synthetic pyrethrins such as bioallethrin, chlorinated hydrocarbons such as DDT or 1,1,1-trichloro-

2.2-bis- (p-chlorophenyl) ethane and its mixtures with the o, p 'isomer, BHC or mixture of isomers of 1,2,3,4,5,6-hexachlorocyclohexane, toxaphene or camphechlor, which is a mixture of camphene isomers chlorinated at 67-69% chlorine, dichlorobenzenes, acaricides such as quinomethionate or S, 6-methyl-2,3-quinoxalinediyl cyclic dicofol, dicofol or 2,2,2- trichloro-1,1-bis (p-chlorophenyl) ethanol and tetradifon or 2,4,4 ', 5-tetra-chlorodiphenylsulfone, non-insecticidal compounds such as synergistic derivatives of methylenedioxyphenols such as piperonyl-butoxide or 5- [ 2- (2-butoxyethoxy) ethoxymethyl] -6 propyl-

1.3-benzodioxole, sesamex or 2- (3,4-methylenedioxyphenoxy) -3,6,9-trioxa-undecane, OO-dimethyl and O-phenyl phosphorothioate, fungicidal compounds such as copper sulfate , dinocap which is a mixture of 2,6-dinitro-4-octyl-phenyl crotonates and 2,4-dinitro-6-octylphenyl crotonates (the octyl radicals being isomeric radicals, namely 1-methylheptyl, 1 -ethyl-hexyl and 1-propylpentyle), chloroxylenol or 4-chloro-3,5-xylenol, thiophanatemetyl or 1,2-bis (3-methoxycarbonyl-2-thio-ureido) benzene, dichlorophene or bis (5 -chloro-2-hydroxyphenyl) methane and thiuram or tetramethylthiuram disulfide; preparations of Bacillus thuringiensis (toxins and organisms) and insect viruses.

Many of these auxiliary compounds are conventional and the only criterion which they must satisfy is to be compatible with the compound of formula I and the other constituents of the compositions.

The compositions in accordance with the invention generally contain 0.05 to 90% weight / volume of the compound of formula I and are applied in doses exerting the desired effect, as appreciated by the cultivator or any other specialized performer, depending on the nature of the plants to be treated.

Examples 1 to 4 below illustrate the preparation of the compound of formula I.

Example 1:

10.4 g of 3-t-butylphenoxyacetic acid are heated to reflux in 80 ml of propanol for 2 h while hydrogen chloride gas is bubbled through the solution. The excess propanol is removed by distillation, then the residue is dissolved in 75 ml of diethyl ether. The ethereal solution is washed successively with a saturated aqueous solution of sodium bicarbonate and with water, after which it is dried over sodium sulfate, filtered and evaporated to dryness. The oily residue is distilled to give 8.5 g of propyl 3-t-butylphenoxyacetate in the form of a colorless oil boiling at 179-180 ° C / 18 mm Hg.

Example 2:

920 g of 3-t-butylphenoxyacetic acid are heated at reflux for 2 h with 920 ml of thionyl chloride. The excess thionyl chloride is removed by evaporation. The last traces of thionyl chloride are eliminated by evaporation twice in the presence of 500 ml of toluene. The crude 3-t-butylphenoxyacetyl chloride is added slowly to 6.51 propanol at boiling under reflux and, at the end of the addition, the solution is heated to reflux for a further 2 h. The excess propanol is removed by vacuum distillation. The residue is distilled to obtain 1068 g of propyl 3-t-butylphenoxyacetate boiling at 170 ° C / 12 mm Hg and in the form of an almost colorless oil.

5

10

15

20

25

30

35

40

45

50

55

60

65

7

627,729

Example 3:

12.1 g of propyl chloroacetate in 10 ml of dry dimethylformamide are added to a stirred solution at 10-15 ° C. of sodium 3-t-butylphenate (prepared from 10 g of 3-t-butylphenol and 1.64 g of sodium hydride) in 50 ml of dry dimethylformamide. The mixture is stirred at room temperature for 2 h and evaporated to dryness. The residue is dissolved in a mixture of 100 ml of chloroform and 100 ml of water. The organic layer is separated, dried over magnesium sulfate, filtered, evaporated and distilled to give 10.3 g of propyl 3-t-butylphenoxyacetate boiling at 176-178 ° C / 20 mm Hg and in the form of a colorless oil.

Example 4:

27.9 g of methyl 3-t-butylphenoxy acetate boiling at 161-162 ° C / 20 mm Hg obtained as described in Example 2, but dissolved in 45 ml of propanol are dissolved in propanol . The solution is heated to reflux for 90 min, while a stream of gaseous hydrogen chloride is bubbled through it. The excess propanol is removed by evaporation and the residue is dissolved in 75 ml of diethyl ether. The ethereal solution is washed successively with a saturated aqueous sodium bicarbonate solution and with water, then dried over sodium sulfate, filtered and evaporated to dryness. The oily residue is distilled to obtain 23 g of propyl 3-t-butylphenoxyacetate boiling at 173-175 ° C / 15 mm Hg and in the form of a colorless oil.

The following examples illustrate compositions of the invention which include the compound of formula I.

Example 5:

A liquid composition is prepared in the form of a concentrate by mixing:

Constituents

% weight / volume

Propyl 3-t-Butylphenoxyacetate Duoteric MB1 Duoteric MB2

90 5 5

Example 6

A liquid composition is prepared in the form of a concentrate by mixing:

Constituents

% weight / volume

Propyl 3-t-Butylphenoxyacetate Arquad 2C-75 Ethofat 142/20

Aromasol H, up to 100% by volume

60 5 5

Example 7:

A liquid composition is prepared in the form of a concentrate by mixing:

Constituents% weight / volume

Propyl 3-t-Butylphenoxyacetate 20

Duoteric MB1 5

Duoteric MB2 5

Cyclohexanone -3 volumes Ì ,,. .

. > up to 100% by volume Xylene - 1 volume d

The compositions of the type illustrated by Examples 5 to 7 can be diluted with water to give emulsions containing 0.05 to 8.0% w / v of propyl 3-t-butylphenoxyacetate (1 to 4 kg in 50 20001) for spray application. For example,

a) the liquid composition of Example 5 can be diluted with water at the rate of 1 ml of composition per 11 of water, then sprayed until runoff over the last 20 to 30 centimeters of the growing ends of 1 year old fruit trees in the nursery, for example apple or pear trees; this treatment induces vigorous growth of lateral branches having a large favorable angle of separation between the lateral branches and the trunk of the tree;

b) the liquid composition of Example 6 can be diluted with water to a concentration of 10,000 ppm, or 6000 ppm of propyl 3-t-butylphenoxyacetate, and sprayed on Brussels sprout plants when the 5 or 6 first basic cabbages have a diameter of 1 cm; this treatment replaces manual removal of the apical part of the plant and thus increases the yield and reduces losses in Brussels sprout crops;

c) the liquid concentrate of Example 7 can be diluted with water to a concentration of 1250 ppm, ie 250 ppm of propyl 3-t-butylphenoxyacetate, and sprayed on apple trees at the growth stage young fruits; this treatment reduces the number of fruits and thus increases the size and quality of the final harvest.

Example 8:

Undiluted propyl 3-t-butylphenoxyacetate can be applied in a dose of 1 to 2 kg / ha using a very low volume sprayer. To improve spray coverage, a non-phytotoxic spray oil can be mixed at 1 to 51 / ha with propyl 3-t-butylphenoxyacetate before application.

Propyl 3-t-butylphenoxyacetate can be applied in a dose of 1 kg / ha on a cotton crop 2 weeks after full flowering to increase the cotton yield.

Example 9:

A liquid composition is prepared in the form of a concentrate by mixing:

Constituents

% weight / volume

Propyl 3-t-Butylphenoxyacetate Ethylan KEO

Dimethylformamide up to 100% by volume

10 10

This composition can be diluted with water to obtain a clear solution containing 0.05%, or 500 ppm, to 4%, or 40,000 ppm, weight / volume of propyl 3-t-butylphenoxyacetate for application. by spraying.

Such a spray liquid thus obtained and containing 40,000 ppm of composition, or 4,000 ppm of propyl 3-t-butylphenoxyacetate, can be sprayed on sunflower plants about 40 days after sowing. This treatment increases the seed yield and the average seed weight.

Example 10:

The compositions of the genre illustrated by Examples 5,6,7 and 9 can be added to an aqueous solution containing 1% of Perlankrol ESD-60 up to a concentration of 0.05 to 1% weight / volume in 3-t- propyl butylphenoxyacetate for foam application by means of special hydraulic foam-generating nozzles.

Different commercial products indicated above have the following constitution:

Ethylan KEO used as solubilizing agent is a condensation product of 10 mol of ethylene oxide on 1 mol of nonyl-phenol,

5

10

15

20

25

30

35

40

45

50

55

60

65

627729

8

Duoteric MB1 and Duoteric MB2, which are emulsifying agents, are mixtures of anionic / non-ionic emulsifying agents comprising calcium alkylarylsulfonates and condensation products of ethylene oxide on alkyl phenols,

Perlankrol ESD-60, used as a foaming agent, is the sodium salt of a synthetic primary alcohol ether sulfate,

Etofat 142/20, used as an emulsifier, is a condensation product of ethylene oxide on a fatty acid, Arquad 2C-75, used as an emulsifier, is a dicoprahdimethylammonium chloride (the alkyl radicals of this compound comes from coconut oil),

Aromasol H is a hydrocarbon oil 95% by volume of aromatic compounds and boiling from 168 to 200 ° C.

Claims (43)

627729 1. Process for the preparation of the new propyl 3-t-butylphenoxy-acetate ester, characterized in that a compound is reacted of the general formula: where X represents the hydroxyl radical, a halogen atom or an alkoxy radical of 1 to 6 carbon atoms other than the propoxy radical, with propanol. 2. Method according to claim 1, characterized in that X represents the hydroxyl radical and the reaction is carried out in the presence of an acid catalyst, optionally in the presence of an inert organic solvent or with a stoichiometric excess of propanol as solvent, in substantially anhydrous medium at an elevated temperature. 2 3 627729 3. Method according to claim 1, characterized in that X represents a halogen atom and the reaction is carried out optionally in the presence of an acid acceptor and optionally in the presence of an inert organic solvent at room temperature or at a high temperature. 4. Method according to claim 1, characterized in that X represents an alkoxy radical other than the propoxy radical, and the reaction is carried out in the presence of an acid catalyst, optionally in the presence of an inert organic solvent or with a stoichiometric excess propanol serving as solvent, in a substantially anhydrous medium, at an elevated temperature. 5 5. Liquid composition to be used as a regulator of plant growth, characterized in that it comprises, as active constituent of propyl 3-t-butylphenoxyacetate in combination with one or more diluents or liquid adjuvants compatible with this ester and suitable for incorporation into the composition. 6. Liquid composition according to claim 5, characterized in that it comprises at least one wetting, dispersing or emulsifying agent. 7. Liquid composition according to claim 6, characterized in that the wetting, dispersing or emulsifying agent is chosen from sulforicinoleates, quaternary ammonium derivatives, products based on condensation products of ethylene oxide on nonylphenol and / or octylphenol and esters of carboxylic acids of an anhydrosorbitol which have been made soluble by etherification of free hydroxyl radicals by condensation with ethylene oxide. 8. Liquid composition according to claims 5,6 or 7, characterized in that it further comprises one or more compatible auxiliary compounds chosen from insecticides, non-insecticidal compounds, fungicides, preparations of Bacillus thuringiensis and viruses d 'insects. 9. Liquid composition according to one of claims 5 to 8, characterized in that the diluent for propyl 3-t-butylphenoxyacetate is water. 10 10. Liquid composition according to one of claims 5 to 8, characterized in that the diluent for propyl 3-t-butylphenoxyacetate is an organic liquid or a mixture of water with one or more organic liquids, these organic liquids are lending to incorporation into compositions regulating plant growth. 11. Liquid composition according to one of claims 5 to 10, characterized in that it contains 0.05 to 90% weight / volume of propyl 3-t-butylphenoxyacetate. 12. Method for regulating the growth of plants, characterized in that an effective amount of propyl 3-t-butylphenoxy-acetate is applied to actively growing or dormant plant tissues. 13. The method of claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxy-acetate is applied to fruit trees in order to increase their fruit yield. 14. Method according to claim 13, characterized in that the fruit trees bear apples, pears, cherries, plums, citrus fruits or palm nuts. 15 15. The method of claim 13 or 14, characterized in that a liquid composition is applied to fruit trees which contains 750 to 1500 ppm of propyl 3-t-butylphenoxyacetate. 16. The method of claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to fruit trees aged 1 year in the nursery to promote the departure of the anticipated buds. 17. Process according to claim 16, characterized in that a liquid composition which contains 750 to 1500 ppm of propyl 3-t-butylphenoxyacetate is applied to fruit trees aged 1 year in the nursery over the last 20 to 50 centimeters of the growing summit of trees. 18. The method of claim 12, characterized inee that an effective amount of propyl 3-t-butylphenoxyacetate is applied to fruit trees 2 to 3 years old after transplanting in an orchard to promote the growth of secondary lateral branches. 19. Method according to claim 18, characterized in that a liquid composition is applied to fruit trees which contains 1250 to 1500 ppm of propyl 3-t-butylphenoxyacetate. 20 20. Method according to claim 18 or 19, characterized in that the trees are apple or pear trees. 21. The method of claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to ornamental plants to improve their shape by promoting vigorous bush growth and, in the case trees, the departure of the anticipated buds. 22. The method of claim 21, characterized in that a liquid composition is applied to the plant which contains 750 to 4000 ppm of propyl 3-t-butylphenoxyacetate. 23. The method of claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to plants bearing fruit in order to improve the quality of the fruit by thinning at full flowering stage, that of young knotted fruits and intermediate stages, when these growth stages exist. 24. Method according to claim 23, characterized in that a liquid composition is applied to plants bearing fruit, which contains 250 to 1500 ppm of propyl 3-t-butylphenoxyacetate. 25 25. The method of claim 23 or 24, characterized in that the plants bearing fruits are apple trees or vines. 26. The method of claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to a field culture to improve its yield. 27. The method of claim 26, characterized in that a liquid composition is applied to the field culture in a dose providing 0.56 to 2.24 kg / ha of propyl 3-t-butylphenoxyacetate. 28. The method of claim 26 or 27, characterized in that the field cultivation is a culture of cotton, soy, faba bean, baby bean, peanut, rapeseed or sunflower. 29. Process according to claim 27 or 28, characterized in that the propyl 3-t-butylphenoxyacetate is applied at the flowering stage of the culture. 30 30. The method of claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to a young plantation for the chemical disbudding of the plantation. 31. Process according to claim 30, characterized in that a liquid composition is applied to the young plantation which contains 750 to 3000 ppm of propyl 3-t-butylphenoxyacetate. 32. The method of claim 30 or 31, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to trees in the nursery to cause defoliation. 33. Process according to claim 30 or 31, characterized in that a liquid composition which contains 1000 to 10000 ppm of 3-t-butylphenoxyacetate is applied to trees in the nursery, at the end of the growing season or before flowering. propyl. 34. Method according to claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to potato plants to increase the number and the yield of potato tubers. 35. Process according to claim 34, characterized in that a liquid composition is applied to the seed potatoes which contains 1000 to 3000 ppm of propyl 3-t-butylphenoxyacetate. 35 36. The method of claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to a culture of Brussels sprouts to improve the yield of the culture and reduce losses. 37. Process according to claim 36, characterized in that a liquid composition which contains 4000 to 6000 ppm of propyl 3-t-butylphenoxyacetate is applied to Brussels sprouts, when the sprouts are forming. 38. The method of claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to tomato plants to suppress unwanted lateral growth. 39. Process according to claim 38, characterized in that a liquid composition is applied to the tomato plants which contains 3000 ppm of propyl 3-t-butylphenoxyacetate. 40. Method according to claim 12, characterized in that an effective amount of propyl 3-t-butylphenoxyacetate is applied to a monocotyledon culture to increase the yield of the culture by increasing the number of tillers and / or reducing the number blind ears. 40 45 50 55 60 65 41. Process according to claim 40, characterized in that a liquid composition is applied to the culture which contains 200 to 2000 ppm of propyl 3-t-butylphenoxyacetate. 42. Process according to claim 40 or 41, characterized in that the culture is a culture of wheat, barley or rice. 43. Process according to one of claims 12 to 42, characterized in that the liquid composition containing propyl 3-t-butyl-phenoxyacetate is applied to the plant or culture in the form of a spray.