KR800000712B1 - Process for the preparation of aniline derivatives - Google Patents

Abstract

Anilines(I, R1 = C1-4 alkoxl, halogen; R2 = C1-3 alkyl, H, halogen; R5 = H, C1-3 alkyl, halogen; R6 = H, Me; X, = -CH2 or IV; R3 = -COOR' or V; R', R" R''' are H, Me, Et; R4 = C1-6 alkyl, C2-5 alkenyl, C3-6 cycloalkyl), useful as fungicides and plant growth regulators, were prepd. by acylation of II and III(X" = OH, halogen, O-COR4. Thus, 100 g 2,3-dimethyl-6-ethylaniline, 223 g 2-bromopropoonic methylester and 84 g sodium bicarbonate were reacted at 140≰C for 7 hr, and obtained 17 g ester and 10.4 g crotonyl chloride were refluxed for 1 hr in DMF and toluene to give I.

Description

Method for preparing aniline derivative

The present invention relates to a process for the preparation of the aniline derivatives of the following formula (I) useful as plant growth regulators and fungicides.

In the above structural formula, R ₁ is alkyl having 1 to 4 carbon atoms, alkoxy having 1 to 4 carbon atoms, or halogen,

R ₂ is hydrogen, alkyl of 1 to 3 carbon atoms, alkoxy of 1 to 4 carbon atoms, or halogen,

R ₅ is hydrogen, alkyl of 1 to 3 carbon atoms, or halogen,

R ₆ is hydrogen or methyl,

(It does not exceed eight even if the carbon number of substituents R <_1> , R <_2> , R <_5> and R <_6> in a phenyl ring is added together.)

Where R ′, R ″ and R ″ ′ independently represent hydrogen, methyl, or ethyl:

R ₄ is alkyl having 1 to 5 carbon atoms (unsubstituted or substituted by cyano (-CN) or rodano (-SCN)), alkenyl having 2 to 5 carbon atoms, or cycloalkyl having 3 to 7 carbon atoms.

The present invention relates to a method of preparing the compound, a composition containing the compound as an active ingredient, and a method of using the active ingredient as a fungicide and a plant growth regulator.

In the definition of the structural formula, the alkyl moiety of the alkyl group and the alkoxy group may be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, secondary- or tert-butyl and pentyl or hexyl isomer according to the number of carbons indicated. Alkenyl radicals include vinyl, allyl, metallyl, butenyl, methylbutenyl and their isomers, and cycloalkyl radicals include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl. Halogens include fluorine, chlorine, bromine or iodine.

Federal Revenue No. 2,212,268 describes that N-haloacylated anilino alkancarboxyl esters are effective as selective herbicides. However, only a few of the 2,6-dialkylanilino acetic acid and esters thereof N-halo acylated are known as herbicides and no reference has been made to describe their effectiveness as fungicides, in particular plant fungicides.

The compound of formula (I) according to the present invention has a very wide range of bactericidal action for the protection of crops, and the crops to be protected include cereals, corn, rice, vegetables, beets, legumes, peanuts, fruit trees, Ornamental trees, especially grapes, hops, cucumber plants (cucumbers, zucchini, melons) and eggplants (potatoes, tobacco, tomatoes, etc.), bananas, cocoa, rubber trees, and the like.

By treating the prepared compound of formula (I) to a target plant or any part of the plant (fruit, flower, leaf, branch, tuber, root), it is possible to kill the bacteria or to protect the plant parts from the bacteria. Examples of the plant pathogens to be treated as the active compounds according to the present invention include asymptomatic fungi (Pertussis fungi); Basidiomycetes, all pathogens; Incomplete bacteria (blight fungi); In particular, there are fungal steels belonging to the coarse steel, such as phytophthora, peronospora, pseudofernospora, phytium or plasmamopara. In addition, the compound of formula (I) had a penetrating action. The compounds according to the invention can also be used as seed-dressing agents to avoid seed (fruit, tubers, seeds) and branches of plants from fungi and pathogens from the soil. have.

그룹이며 R₄, R₅, R₆및 R′는 상기 정의된 바와 같은 구조식(I)의 화합물이며 이 화합물들은 이하에서 Ia그룹으로 표시한다.Preferred fungicides of the compounds of formula (I) are those in which R ₁ is methyl, R ₂ is in the ortho-position relative to the amino group and methyl, ethyl or chlorine and the XR ₃ group

And R ₄ , R ₅ , R ₆ and R ′ are compounds of formula (I) as defined above and these compounds are hereinafter referred to as the group Ia.

Among the compounds of group (Ia), R 'is methyl, R ₄ is cycloalkyl, alkenyl or alkyl having 2 to 4 carbon atoms, and R ₅ and R ₆ are as described above. It is the same and the compound which does not exceed four in total by the carbon number of R <_1> , R <_2> , R <_5> and R <_6> in a phenyl ring.

Other important compounds of formula (I) are those wherein R ₂ is hydrogen, alkyl of 1 to 3 carbon atoms or halogen, R ₅ and R ₆ are hydrogen and R ₁ , R ₃ , R ₄ , X, R ′, R ″ And R ″ ′ are compounds as described in formula (I).

As the seed powder or the soil treatment agent, a compound of the structural formula (I) or Ia group in which R ₄ is a cyano methyl or rodanomethyl group is preferable.

Plant growth regulators include that R ₁ is methyl or ethyl, R ₂ is in the or-position to the amino group, methyl, ethyl or iso- and -XR ₃ is -CH ₂ -CON (R ″) (R ″ ′). R ₄ , R ₅ , R ₆ , R ″ and R ″ ′ are preferably compounds of formula (I) as described above.

Plant growth control refers to delaying the growth of natural plants, in particular to appropriately reducing the size of the plant (especially its height). This growth decrease is observed in monocotyledonous and dicotyledonous plants, especially in grass, cereals, soybeans or ornamentals.

According to the invention the compound of formula (I) is prepared as follows. That is, the compound of formula (II) is prepared by reacting with the compound of formula (III).

Wherein R ₁ , R ₂ , R ₃ , R ₅ , R ₆ and X are as described above and X ′ is hydroxy, halogen or —OCOR ₄ .

According to another preparation method according to the present invention, the compound of formula (I) is converted to the corresponding alkali salt by reacting the acyl anilide of formula (IV) with butyllithium or sodium hydride and In the presence of an alkali metal carbonate (e.g. sodium carbonate or potassium carbonate) as the proton acceptor or the acylanilide of formula (IV), preferably under the catalytic amount of alkali metal iodide (e.g. potassium iodide) Prepared by reacting with a compound.

R ₁ to R ₆ and X represented by the above formulas (II), (III), (IV) and (V) are all as defined in formula (I), Hal is a halogen atom, preferably chlorine Bromine, or a radical that can be easily released.

The reaction according to the invention can be carried out in the presence or absence of a solvent or diluent that is inert to the reactants. Suitable solvents or diluents include aliphatic or aromatic hydrocarbons such as benzene, toluene, xylene, petroleum ethers; Halogenated hydrocarbons such as chlorobenzene, methylene chloride, ethylene chloride, chloroform; Ethers and ethers such as dialkyl ethers, dioxane, tetrahydrofuran; Nitriles such as acetonitrile; N, N-dialkylamides (eg dimethylformamide); Acetic anhydride, dimethylsulfoxide, ketones (eg methylethylketone) and mixtures of these solvents. The reaction temperature is 0 ° to 180 ° C, preferably 20 ° to 120 ° C. It is advantageous to use acid acceptors or condensing agents in the reaction according to the invention, examples of which include tertiary amines such as trialkylamines (e.g. triethylamine), pyridine and pyridine bases, or inorganic base examples; Oxides and hydroxides, hydrogen carbonate, carbonates of alkali metals and alkaline earth metals and sodium azate. In the above production method, an excess amount of the aniline derivative of formula (II) may also be used as the acid acceptor.

The reaction for preparing the compound of formula (I) from the compound of formula (II) can be carried out without an acid acceptor, in which case it is advantageous to pass through nitrogen to remove the hydrogen halide generated during the reaction, and in some cases dimethyl It is very advantageous to use formamide as a reaction catalyst.

The compound of formula (II) used as starting material in the present invention is [J. Org. Dhem. 30, 4101 (1965): Tetrahedron 1967, 487: Tetrahedron 1967 493, can be prepared by reference to the process for preparing aniline-alkanoic acid esters described in the literature.

인 구조식(I)의 화합물은 부재 탄소원자(*)를 가지고 있는 통상적인 방법에 따라서 광학적인 대장체로 분할할 수 있으며 이중에서 에난티오머 D-형태의 것이 살균작용이 더 우수하다.X

Phosphorus compounds of formula (I) can be divided into optical colons according to a conventional method having an absent carbon atom (*), of which the enantiomer D-form is better sterilizing.

Therefore, the compound of the formula (I) prepared according to the present invention is preferable to the one of D-configuration. These D-arrays have a left linearity in methanol or acetone.

Pure optical D-col is obtained by first preparing a racemic compound of formula (VI) and reacting it in a known manner with a nitrogen containing and optically active base to obtain the corresponding salt.

R ₁ , R ₂ , R ₅ and R ₆ in the above formula are as defined in formula (I). Pure D-forms fractionate crystallize the salts and then liberate the acid of formula (VI) with high optical D-lysate and, if necessary, form salts, crystallize and release the α-anilino-propionic acid of formula (VI). It is obtained stepwise by repeating (some times possible). If necessary, such a pure D-form is reacted with methanol or ethanol in the presence of hydrochloric acid or sulfuric acid by a known method, for example, to obtain an optical D-array of an ester included in the formula (II), Or by reacting with an amine of the corresponding structural formula HN (R ″) (R ″ ′), preferably via an acid halide, to produce an amide of the optical D- configuration that falls within the range of formula (II). Α-phenylethylamine is suitable as the optically active organic base.

It is also possible to prepare enantiomeric D-forms of the formula (VII) without fractional crystallization, which diazotizes the amino group in natural L-aniline in the presence of hydrochloric or bromic acid, thereby yielding N ₂ . When necessary, while replacing the halogen accompanying the separation (preserving the L-array) and esterifying it with methanol or ethanol if necessary, the conversion of the ester to the D-array of formula (VII) is almost complete. Obtained by reaction with aniline of VIII). Am. Chem. Soc. 76, 6065].

In a similar manner it is also possible to prepare amides in which R ₃ is (R ″) (R ″ ′).

축에서 아트로프 이성화를 볼수 있는데, 그 경우에서의 페닐링은 최소한 2,6-위치에 치환되어 있으며, 동시에 이축에 비대칭적으로 치환되어 있다. 이 현상은 질소원자에 부수적으로 도입되어진 -X-R₃과 -채-R₄기들의 입체장애에 의하여 발생된다.Regardless of the optical isomerization mentioned, phenyl-

Atromatic isomerization can be seen in the axis, in which case the phenyl ring is substituted at least in the 2,6-position and at the same time asymmetrically in the biaxial axis. This phenomenon is caused by steric hindrance of the -XR ₃ and -Che-R ₄ groups introduced incidentally to the nitrogen atom.

Regardless of the optical isomerization, cis / trans-isomerization occurs due to the heavy bond when R ₄ is alkenyl.

When not synthesized for the purpose of separating the optical isomers separately, the product is produced as two optical isomers, two atropes isomers, two cis / trans-isomers or a mixture of these possible isomers. However, fundamentally, the enantiomer D-form has an excellent effect in terms of bactericidal action (compared to D, L- or L-form), and is not significantly affected by atropisomerization or sisu / trans-isomerization. .

The following examples are intended to illustrate the present invention in more detail, thereby limiting the scope of the present invention. Unless otherwise indicated, the active substance of formula (I) always means its racemate.

Example 1

N- (1'-methoxycarbonyl-ethyl) -N-crotonyl-2,3-dimethyl-6-ethylaniline

A) A mixture of 100 g of 2,3-dimethyl-6-ethylaniline, 223 g of 2-bromopropionic acid methyl ester, and 84 g of sodium hydrogen carbonate was stirred at 140 ° C. for 7 hours, then cooled and diluted with 300 ml of water. Then extracted with diethyl ether. The extract is washed with a small amount of water, dehydrated over sodium sulfate, filtered and the ether is evaporated. The excess product is distilled off in high vacuum after excess 2-bromo propionic acid methyl ester is distilled off.

Boiling Point: 88-90 ° C./0.04 Torr

B) A mixture of 17 g of ester, 10.4 g of crotonyl chloride, 2 ml of dimethylformamide and 150 ml of anhydrous toluene obtained according to the above step (a) is refluxed for 1 hour. The solvent is evaporated off and the crude product is distilled off in vacuo. Boiling Point: 128 to 129 ° C / 0.03 Torr. The D-form of the cis / trans isomers (compounds 141a and 141b) is of the pure D-form of α- (2,3-dimethyl-6-ethylanilino) -propionic acid methyl ester with croronic acid or a reactive derivative thereof. It is obtained by a misfire reaction.

Other intermediates (including compounds of the following structural formula (IIa) (R ₁ = 2 position)) may be prepared in a similar manner as in Example 1 (A).

Example 2

N- (1'-methoxycarbonyl-ethyl) -N-cyclopropylcarbonyl-2,6-dimethylaninine

A solution of 51.8 g of α- (2,6-dimethylanilino) -propionic acid methyl ester in 200 ml of mousse toluene was treated with a solution of 31.3 g of cyclopropanecarboxylic acid chloride dissolved in 50 ml of anhydrous toluene while stirring at room temperature. After 2 ml of dimethyl formamide is added the reaction mixture is refluxed for 2 hours and the solvent and excess cyclopropanecarboxylic acid chloride are distilled off under reduced pressure. Residual oil is dissolved in a small amount of petroleum ether to crystallize. Recrystallization from toluene / petroleum ether yields compound 1 having a melting point of 84 to 87 ° C.

Example 3

N- (1'-methoxycarbonyl-ethyl) -N-vinylcarbonyl-2,6-dimethylaniline

A solution in which 80.6 g of acrylic acid chloride was dissolved in 150 ml of anhydrous toluene was stirred well at 20 ° C., while 70.4 g of pyridine and 166 g of α- (2,6-dimethyl alinino) -propionic acid methyl ester were dissolved in 160 ml of anhydrous toluene. Drop on After stirring the reaction mixture for 20 hours, the precipitated pyridine hydrochloride is filtered.

The solvent is evaporated off in vacuo and the residual oil distilled in vacuo. (Compound 2):

Boiling point 130 ° to 135 ° C./0.1 Torr.

Compounds of the following structural formula (Ib) (R ₁ = 2-position) are prepared in the same manner as in the present example or the foregoing process.

The following structural formula (Id) (R ₁ = 2-position) is prepared by the method of Example 1-3 above, or one of the above-mentioned methods.

In addition, the compound of the following structural formula (Id) (R ₁ = 2-position) is prepared by the method of Examples 1-3 or one of the aforementioned methods.

The compounds of formula (I) can be used with other suitable insecticides or plant growth regulators to broaden their range of action. Only compounds of formula (I) may be used or in combination with suitable carriers and / or other additives. Suitable carriers and additives are solid and liquid substances used in conventional pesticide compositions, for example natural or regenerated inorganic substances, solvents, dispersants, wetting agents, thickeners, adhesives, binders or fertilizers. The same thing can be mentioned. The amount of active ingredient in the composition usually used is 0.1 to 90%.

The compound of formula (I) is used in the form of the following (wherein the weight percent in parentheses indicates the effective amount of the active ingredient).

Solid form: powder and brown ash (up to 10%); Granulation; Coating, Immersion, and Homogeneous Blends (1 to 80%)

Liquid form: a) Water-dispersible active ingredient Concentrate: Hydrating and paste (usually 25 to 90% for packaging, 0.01 to 15% for solution): Emulsifying concentrate and concentrated solution (10 to 50%: for solution , 0.01-15%)

B) Solution (0.1% concentrated 20%)

The active ingredient of formula (I) may be formulated as follows.

Powder: It consists of the following components.

a) 50% and b) 2% powder:

a) 5 parts active ingredient

95 parts talc

b) 2 parts of active ingredient

1 part dispersive silicic acid

97 parts talc

The active ingredient is mixed with the carrier and ground in a form suitable for use as a powder.

Granulation: It consists of the following ingredients.

5% granularity:

5 active ingredients

0.25 parts epichlorohydrin

0.25 parts cetyl polyglycol ether

3.50 parts of polyethylene glycol

91 parts kaolin (particle size 0.3 to 0.8 mm)

The active ingredient is mixed with epichlorohydrin and the mixture is dissolved in 6 parts of acetone, followed by addition of polyethylene glycol and cetyl polyglycol ether. The resulting solution is sprayed on kaolin and the acetone is evaporated in vacuo.

These fine particles are beneficial for use in removing soil bacteria.

Hydrating agent: It consists of the following components.

a) 70% b) 40% c) and d) 25% and e) 10%

Hydration:

a) 70 parts of active ingredient

5 parts sodium dibutyl naphthylsulfonate

3 parts naphthalenesulfonic acid / phenolsulfonic acid / formaldehyde condensate (3: 2: 1)

10 kaolins

12 Champagne Chokes

b) 40 parts of active ingredient

5 parts sodium lignin sulfonate

1 part sodium dibutylnaphthalene sulfonic acid

54 copies of silicic acid

c) 25 parts of active ingredient

4.5 tablespoons lignin sulfonate

1.9 parts champagne choke / hydroxyethyl cellulose mixture (1: 1)

1.5 parts sodium dibutylnaphthalenesulfonate

19.5 parts silicic acid

19.5 Champagne Chokes

28.1 kaolin

d) 25 parts of validity

2.5 parts isooctylphenoxy-polyethylene-ethanol

1.7 parts champagne choke / hydroxyethyl cellulose mixture (1: 1)

8.3 parts sodium aluminum silicate

Kiselgur, part 16.3

46 kaolins

e) 10 parts of active ingredient

Mixture of sodium salts of 3 parts saturated fatty alcohol sulfonate

5 parts naphthalenesulfonic acid / formaldehyde condensate

Part 2 kaolin

The active ingredients are sufficiently mixed with suitable additives and comminuted with a suitable grinder to obtain a wetting and suspending powder with excellent wetting power. This watering agent is diluted with water to obtain a suspending agent with the desired concentration, which is particularly suitable for use on leaves.

Emulsifying concentrate: It consists of the following components.

25% Emulsion Concentrate:

25 active ingredients

2.5 parts oxidized vegetable oil

10 parts alkylarylsulfonate / fatty alcohol polyglycol ether mixture

5 parts dimethyl formamide

57.5 parts xylene

The concentrate is diluted with water to obtain an emulsifier with the desired concentration suitable for use on the leaves.

Example 4

Effects of Tomato (Solanum Lycopersicum) on Phytophthora infestans

Ia) Residual Prevention

Tomato crops of the "Roter Gnom" variety grown for 3 weeks are sprayed with a hydrous solution containing 0.05% of the active compound, and then infected with the strain of the yeast in the late blight and dried. They are stored daily in high humidity and 18-20 ° C. rooms (artificially moist fog removed). After this period, the efficacy of the test substance is measured by the number and size of the normal spots on the leaves.

Ib) therapeutic action

A “rotorgnome” tomato crop grown for about three weeks is sprayed and infected with the yeast suspension of the late blight bacteria and cultured in a room saturated with moisture of 18 to 20 ° C. Humidity control is stopped after 24 hours. After the plant is dried, it is sprayed with a liquid containing the active substance formulated as a wetting agent to a concentration of 0.05%. After the spray coating has dried, the crop is again stored in a damp room for 4 days. The efficacy of the test substance is measured by the number and size of the normal spots on the leaves during this period.

(II) preventive-invasive action

The active material (0.05% concentration: volume to soil) is used in the form of a hydrous powder on the soil surface in a container where the “rotorgnome” tomato crop is grown for three weeks. After 3 days, the intestinal suspension of the late blight bacteria is sprayed and infected on the lower part of the leaves of the crop. The efficacy of the test substance is determined by the size and number of spots on the leaves preserved for 5 days in the crop where the crop is kept in a humid saturated room at 18 to 20 ° C.

In the above tests (Ia), (Ib) and (II), it can be seen that the compounds of formula (I) have excellent bactericidal effects on the leaves. The bacterial infection rate when using compounds of the group Ia in which R ′ is methyl was determined to be 2% or less.

Compound 1, 2, 7, 12, 22, 37, 39, 49, 66, 81, 144, 148, 101, 102, 103, 119, 127, 130, 131, 132, 138, 139, 139, 140, 141 , 142, etc. were found to completely inhibit the infection of the germ (about 0 to 5%).

Example 5

Action against vine fungal disease (Plasmopora viticola) (Bert. Et Curt.) (Berl. Et de Toni)

a) residue-prevention

Vine branches of the “Chasselas” variety are grown in greenhouses. At the end of the tenth leaf, a solution of the active compound prepared in hydrated form is sprayed at three weeks of the vine. After the coating layer has dried, the lower part of the leaf of the plant is wound with the spore suspension of the Bacillus bacterium and then stored in a damp room for 8 days. After this period, symptoms of disease appear in the control crop. The efficacy of the test substance is determined by measuring the size and number of infection sites present in the treated crop.

b) therapeutic action

Vine branches of the “Chasellas” cultivar are grown in greenhouses, and when they reach the 10th leaf, the lower parts of the plant leaves are infected with the spore suspension of the Bacillus fungi, and then stored in a damp room for 24 hours before being hydrated. Spray the active substance solution prepared with After 7 days in these damp rooms, large tissues show signs of disease. The efficacy of the test substance is measured as the number and size of infected sites.

In the test examples of (a) and (b) above, the compounds of formula (I) showed a very good bactericidal effect. Compounds of the group Ia in which R ′ is methyl all reduced the infection rate of the germ to 20 or less without exception. Compounds 1, 27, 10, 12, 13, 22, 27, 39, 40, 48, 49, 66, 81, 82, 150, 127, 128, 130, 131, 1362, 136, 142, 143 and others It showed little infection rate (0-5%).

Example 6

Erysiphe Graminis in Barley (Hordeum vulgare)

Residue-protection

Barley crops up to 8 cm tall are sprayed with a solution formulated with a hydrating agent (0.05% active material). After 48 hours, the sprayed crops are infected with the conidia of the powdered powder. Infected barley crops are left in a greenhouse at 22 ° C. and infection rates are measured 10 days later.

Compounds 33, 34, 50, 56, 57, 58, 69, 73, 74 and the like in the above test showed the infection rate of the bacteria at 20% or less.

Example 7

Actions on Pythium debaryanum in Beet Vulgaris

a) action after soil treatment

The germs grown in sterile oat grains are added to a mixture of soil and sand. The soil contaminated with bacteria is filled in pots and sown the beet seeds. Immediately after sowing, the test compound formulated as a hydrating agent is poured into the soil in the form of an aqueous suspension (active compound ratio of 0.002 per volume of soil). The pot is left for 2 to 3 weeks in a greenhouse at 20 to 24 ° C. Allow the soil to spray gently and evenly so that it is evenly moist. The germination rate of beets, the healthy and the diseased are measured by number of test compounds.

b) post-treatment of seed meal

The bacteria grown in oat grains are added to a mixture of soil and sand and filled in pots. Beet seed is treated as a test powder (0.1% active substance per seed weight) as a powder for seed treatment and sown in bacterially contaminated soil.

The pots are left for 2-3 weeks in a greenhouse at 20-24 ° C. Just spray water on the soil in the pot to keep the moisture even. The efficacy of the test compound is measured as the germination rate of beets and the number of healthy and diseased.

In both test examples (a) and (b), the germination rate of the beet after treatment with one of the compounds of formula (I) according to the present invention was 85% and all were healthy. In control bacteria, germination rate was less than 20%, and some were sick.

Example 8

Grass growth inhibition

Structural formula (I) of the present invention after two days of cutting the grass once in spring in 3 m ² of the outdoor grass field consisting of Lolium perenne, Poa pratensis and Festuca rubra Spray an aqueous solution of the active substance. The amount of active ingredient used is proportioned to 5 kg per hectare. Leave untreated zone as control.

The average growth rate (height) in the treated and untreated groups is measured 6 days after use. Turf zones treated with active material grew uniformly and were healthy.

It was found that compounds of formula (I), particularly compounds of formula (I) in which -XR ₃ represents CH ₂ -CO-N (R ") (R"'), inhibited the growth rate to be nearly complete.

Claims (1)

A process for preparing a compound of formula (I), characterized by reacting a compound of formula (II) with a compound of formula (III).

In the above structural formula R ₁ is alkyl having 1 to 4 carbons, alkoxy having 1 to 4 carbons, or halogen R ₂ is hydrogen, alkyl of 1 to 3 carbon atoms, alkoxy of 1 to 4 carbon atoms, or halogen R ₅ is hydrogen, alkyl of 1 to 3 carbon atoms, or halogen R ₆ is hydrogen or methyl (the total number of carbon atoms of the substituents R ₁ , R ₂ , R ₅ and R _{6 in} the phenyl ring should not exceed eight);

Where R ′, R ″ and R ″ ′ independently represent hydrogen, methyl, or ethyl: R ₄ is alkyl having 1 to 6 carbon atoms (unsubstituted or substituted with cyano or rodano), alkenyl having 2 to 5 carbon atoms, or cycloalkyl having 3 to 7 carbon atoms; X ′ is OH, halogen, or O—CO—R ₄ .