CS199209B2 - Herbicide and method of producing the active constituent - Google Patents

Abstract

The herbicide contains a herbicidally effective amount of a compound of the formula <IMAGE> and an inert diluent. In the herbicidal procedure, a plant is brought into contact with a herbicidally effective amount of a compound of the formula I. The active substances of the formula I are prepared by heating a mixture of a sterically hindered phenylazomethine and a compound of the formula: <IMAGE> in vacuo until the evolution of the sterically hindered aniline comes to an end.

Description

is selected from the group consisting of halogen, lower alkyl, lower alkoxy and lower alkylthio. As used herein, the term "lower" refers to straight or branched chain alkyl radicals having up to four carbon atoms. In the compounds of formula I, alkyl radicals having no more than two carbon atoms are preferred, and a preferred halogen atom is a chlorine atom.

According to the invention, the N, N'-methylene-bis- (O, O-diaryl-N-phosphonomethyliglycinonitriles) of the formula I can be produced either in parallel with the preparation of O, O-diaryl-N-phosphonomethylglycinonitriles mentioned in US 4,067,719 or of these O, O-diaryl-N-phosphonomethyl glycinonitriles as starting materials.

In the above process, wherein the bis derivative of the formula I is formed in parallel to the O, O-diaryl-N-phosphonomethylglycinonitrile, a mixture of a substantially phosphorous ester of the formula II is prepared

O

II (RO) 2 —P — H (II) wherein R is phenyl or methyl, and R may further contain up to two substituents from 99209 in. . wherein R is as defined above, with 1,3,5-tricyanomethylhexahydro-1,3,5-triazine. (also called the N-methylene glycinonitrile trimer) of formula III

CH _Z CN

The mixture is heated to a temperature sufficient to initiate and maintain the reaction between the phosphorous acid ester and the triazine to a mixture of the desired products.

Although it is not necessary to use solvents in the process of the invention, it is sometimes used. . convenient 'for more comfortable. , and to facilitate the reaction. The use of a solvent is also advantageous in that it allows the reaction to be carried out at a controlled temperature. As the solvent, one can be used in which the triazine is soluble and which does not react with any reactant; a suitable inert solvent is, for example, acetonitrile, ethyl acetate, tetrahydrofuran and the like.

The reaction temperature may range from about 25 ° C to about 110 ° C. You can work i. at higher reaction temperatures, but this does not result in a proportional improvement as the reaction is substantially complete by the time the temperature reaches about 85 ° C.

As can be seen from the above formulas II and III, a moral ratio is necessary to achieve optimal results. phosphorous ester to triazine equal to 3: 1. Higher or lower molar ratios may also be used, but these ratios. The components are uneconomical, because at higher molar ratios it is necessary to remove them from the product. excess ester. phosphorous acid. and at lower molar ratios of ester to triazine, undesirable by-products can be formed.

The reaction is usually carried out for economic reasons. at atmospheric pressure. - It is possible to work at higher or lower reaction pressure, but it is not achieved. no improvement.

The reaction mixture is heated for as long as. until all the phosphorous acid ester and all triazine are consumed. progress. the reaction is monitored by spectral analysis using a nuclear magnetic resonance spectrum (NMR). If 'when. by analyzing the presence of impurities in the form of an unreacted excess of starting materials or solvent, the reaction mixture is concentrated by distilling off the volatiles under reduced pressure. The desired product is then isolated and purified by either crystallization or chromatography. In the following procedures, care must be taken not to hydrolyse the ester moiety of the molecule.

In a second process for preparing bis-derivatives of the general formula I. is used . as starting materials, 0,0-diaryl-N-phosphonomethylglycinonium. trils prepared by the 'methods described'. U.S. Pat. No. 4,067,719. The starting material is mixed sterically. with hindered phenylazomethyne and the mixture is heated under reduced pressure. It is believed that as an intermediate formation. no azo-adduct, at. whose heating cleaves the hindered aniline. When the aniline cleavage is complete, the reaction mixture is worked up. to the desired methylene bis-derivative of the general formula (I), the sterically hindered reaction can advantageously be used for the reaction of the invention. azomethines whose phenyl residue is substituted at both ortho positions.

Suitable substituents at the ortho positions are lower alkyl groups, with the exception of two tertiary butyl groups. groups in positions. . 2 a. 6, and further can be used in one ortho position of a halogen atom or a lower alkoxy group. in the second ortho position of any of the aforementioned lower alkyl. Other positions of the phenyl ring may also be. substituted. Suitable sterically hindered phenyl groups include, for example, 2-methyl-1-6-ethyl; .......... .....

2,6-diethyl ·,

2-methyl-6-tert-butyl-, 2-chloro-6-tert-butyl-, 2-bromo-6-tert-butyl-, 2-methoxy-6-tert-butylphenyl and the like.

It has been found that generally when azomethines are used for this reaction, they are not. sterically hindered as described above, such azomethine is trimerized to hexahydrozitriazine. Default. glycinonitriles prepared. according to the aforementioned U.S. Pat. No. 4,067,719 often contain impurities. of phenolic character which may interfere with the preparation of the desired methylenebisderiyates of formula I. It is therefore preferable to first prepare the salt of the starting material. glycinonitrile with a strong acid which is separated from the solvent used and is thus separated from the. mentioned. impurities. The salt is isolated and the necessary glycinonitrile is released therefrom. neutralization. Neutralization is necessary. carry out. carefully to avoid hydrolysis of the aryl ester groups.

The reaction of glycinonitrile with azomethine starts already at. at room temperature as shown by NMR spectral analysis and. it can be carried out up to about 125 ° C; . however, the preferred reaction temperature is in the range of 6-80 ° C. The reaction proceeds well under atmospheric pressure, but the sterically hindered aniline formed during the reaction may react with the desired product to form an 'undesired adduct. It is therefore advantageous to remove the sterically hindered aniline from the reaction mixture, and this is most effectively accomplished by carrying out the reaction under reduced pressure and distilling off. the resulting .... substituted aniline.

The molar ratio of glycinonitrile to azomethine is preferably about 2: 1. Higher or lower molar ratios may also be used, but these reactant ratios are disadvantageous as they result in reduced yields of the desired product due to the formation of mixtures with unreacted starting materials and the intermediate azo-adduct.

The reaction may optionally be base catalysed; however, the reaction proceeds well to the desired product without this catalysis.

The process according to the invention is illustrated in more detail by the following non-limiting examples. All "parts" mean, unless otherwise stated, "parts by weight".

Example 1

Acetonitrile solution (10 mL) of di (3,4-dimethylphenyl) phosphite (8.7 g, 0.03 mol) was added to an acetonitrile solution (50 mL) of 1,3,5-tricyanomethylhexahydro-1,3,5-triazine (2.04) g (0.01 mol) and the mixture is heated at 55 DEG C. for 90 hours The precipitated solid is filtered off and the solvent is distilled off from the filtrate to give a burgundy red oil which contains, according to NMR spectral analysis, a mixture of the desired product. The crude oil (8.0 g) was chromatographed on a silica gel column (450 g) using a mixture of cyclohexane (50%) and ethyl acetate (50%) to elute the substances, collecting 60 ml fractions. O, O-di (3,4-dimethylphenyl) -N-phosphonomethylglycinonitrile Fraction 20-25 from the chromatographic column, after evaporation of the solvents, gives 1.62 g of an oily product on _D ²² = 1.5387 which, after recrystallization from a mixture of carbon tetrachloride and isooctane gives N, N'-methylenebis- [O, O-di (3,4-dimethylphenyl) -Nphosphonomethylglycinonitrile] as a colorless crystalline solid, mp 79-80 ° C.

Example 2

An acetonitrile solution (100 mL) of di (m-tolyl) phosphite (10.7 g, 0.04 mol) and 1,3,5-tricyanomethylhexahydro-1,3,5-triazine (2.72 g, 0.0133 mol) was added. The mixture was heated to 50 ° C for 3 days and the reaction mixture turned burgundy red to give 12.4 g of a red oil (92.4%) after distilling off the solvent, and the crude oil (9.0 g) was chromatographed on a silica gel column. by using a mixture of cyclohexane (60%) with ethyl acetate (40%) to elute the substances, collecting 60 ml fractions, pure O-di (m-tolyl) -N-phosphonomethylglycinonitrile is contained in fractions 45-63. 28-40 of the above chromatography, the solvents are distilled off under reduced pressure to give N, N'-methylenebis- [O, O-di (m-tolyl) -N-phosphonomethylglycinonitrile] as a solid, m.p. 113-114. Noc: 2 ° C.

Elementary analysis:

calculated:

% C, 62.50;% H, 5.69;% N, 9.32.

% H, 5.72;% N, 8.23.

Example 3

A mixture of di- (p-methylthiophenyl) phosphite (30.4 g, 0.082 mol) and 1,3,5-tricyanomethylhexahydro-1,3,5-triazine (5.6 g, 0.0275 mol) was heated to 80 ° C. The dark red-brown oil obtained was cooled to room temperature and dissolved in carbon tetrachloride (200 ml). Silica gel (30 g) was added to the solution, the mixture was stirred and filtered, and silica gel (20 g) was added again to the filtrate and after stirring the mixture was filtered. Half of the obtained solution was adsorbed onto silica gel (12.5 g), the product impregnated silica gel was applied to a silica gel column (450 grams) and the mixture was chromatographed using a mixture of cyclohexane (60%) and ethyl acetate (40%) to elute; 60 ml fractions were collected. Fractions 28-39 were combined and the solvents were distilled off; 1.2 g of N, N'-methylenebis [O, O-di (p-methylthiophenyl) -N-fosfonomethylglycinonitrilu] as an oil N _D ²² = 1.6151.

Example 1 a d 4

To the acetonitrile solution (300 mL) of 1,3,5-tricyanomethylhexahydro-1,3,5-triazine (68 grams, 0.333 mol) was added diphenylphosphite (234 g, 1.0 mol) and the mixture was heated at 75 for 3 hours. -82 ° C. After cooling, the solvent was distilled off from the solution under reduced pressure to give a dark colored oily product containing mainly the corresponding glycinonitrile.

A sample of the crude oily product (101 grams) was adsorbed onto silica gel (the material was dissolved in chloroform, silica gel was added and the solvent was evaporated), the resulting material was applied to a silica gel column (1.1 kilograms) and eluted with chloroform; 1 liter fractions were collected. Fractions 13-14 are combined, the solvent is distilled off and the residue is recrystallized from a mixture of dichloromethane and cyclohexane; 51 g of O, O-diphenyl-N-phosphonomethylglycinonitrile are obtained.

Fractions 11-12 were combined, the solvent was distilled off and the solid precipitated from the oily residue was filtered off. Mother liquors from fractions. 11-12 were re-chromatographed on a silica gel column (760 g), eluting with cyclohexane (60%) / ethyl acetate (40%); 100 ml fractions were collected. Fractions 40-49 are combined, the solvent is distilled off and the residue is recrystallized from cold carbon tetrachloride; N, N‘-methylenebis- (O, O-diphenyl-N199209) was obtained

(phosphonomethylglycinonitrile), m.p. 98-99 ° C. .

Elementary analysis:

calculated:

% H, 4.90;% N, 9.09.

found:

H, 4.79; N, 8.97.

Example 5

For distillation apparatus with ball descending. a mixture of O, O-diphenyl-N-η 5 -5- (4-trifluoromethyl-phenylazomethine) (78.05 g, 0.258 mol) with 2,6-diethylphenylazomethine (21.5 g) was added via a condenser. 10 g of sodium methoxide are added and the mixture is heated at 65-75 ° C under reduced pressure (0.02-0.07 torr) for about 1 hour. The vacuum was removed, tetrachloromethane (500 ml) was added to the residue, the oily product which crystallized was dissolved with heating, the solution was filtered and the filtrate was discarded. The precipitated crystalline product is filtered off and washed with cold carbon tetrachloride, the mother liquors are concentrated and the second crop of crystalline product is filtered off.

72.5 g of N, N‘-methylenebis- (O, O-diphenyl-N-phospho00106, 17, 170100011), m.p. 100-100.5 ° C.

Example 1 a d 6

O, O-Di (p-methoxyphenyl) -N-phosphonomethylglycinonitrile (7.4 g, 0.02 mol) was mixed with 2,6-diethylphenylazomethine (1.63 g, 0.01 mol); a slight exothermic reaction occurs. After about half an hour, the mixture is transferred to. distillation apparatus with descending ball condenser and heated to 60-70 ° C under reduced pressure (0.1 torr) for asi about 1/2 hour; 2,6-diethylaniline distilled off. The crude product in the distillation flask is cooled, dissolved with stirring in hot carbon tetrachloride, the solution is filtered and the precipitated oily product is washed twice with decantation with ether. The oily product is dissolved in chloroform and the solution is concentrated. N, N-methylenebis- [O, O-di (p-methoxyphenyl) -N-phosphonomethylglycinonitrile] precipitated in the form of red-brown colored prism crystals, m.p. -90-92 ° C.

Elementary analysis:

calculated:

57.07. % C, H 5.20, N 7.61;

found:

% H, 5.22;% N, 7.63.

Example 7

O, O-Di- (4-chloro-3-methylphenyl) -Nfphosphonomethylglycinonitrile (2.8 g, 0.007 mol) was mixed with 2,6-diethylphenylazomethine (0.57 g, 0.0035 mol) ); will occur. weak exothermic - reaction. . The mixture was transferred to a descending ball condenser and heated to 75-80 ° C under reduced pressure (0.1 torr) for about 1/2 hour; distills off - 2,6-diethylaniline. The crude reaction product remaining in the distillation flask is cooled and recrystallized from a mixture of carbon tetrachloride with methylcyclohexane and ether. There was obtained N, N N-methylenebis- [O, O-di (4-chloro-3-methylphenyl) -N-phosphonomethylglycinonitrile] as a colorless crystalline solid, m.p. 89.5-90.5 ° C.

Elementary analysis:

calculated:

51.87% c, - 4.23% H, 6.91% - N, found:

% C, 51.77;% H, 4.25;

Example 8

The post-emergence herbicidal activity of the various compounds - prepared by the process of the invention - was determined as follows. The active ingredients were applied in the form of spraying on plants of various species 14-14 days old. Spraying, a solution of the active substance in water or an organic solvent / water mixture containing a surfactant - (35 parts of butylammonium salt of dodecylbenzenesulfonic acid and 65 parts of tall oil condensed with ethylene oxide in a ratio of - 11 moles ethylene oxide to 1 mole tali oil) has been applied to plants grown in different groups on 'dishes', in several doses of active substance (expressed in kg per hectare). The treated plants were placed in a greenhouse and the effect of the spray was detected and recorded in approximately 2 weeks or approximately - 4 weeks. The values found are shown in Tables I and II.

In Tables I and II, the following scale of post-emergence herbicidal activity is used:

Reaction Plant Index

0—24% damage 0

25—49% damage 1

50—74% damage 2

75–99% damage 3 death of all plants 4 plant species that were not present at the time of treatment x

In the tables below, the symbol - WAT number of weeks after treatment - plants and the individual plant species treated are indicated with the following written code:

A — Canadian thistle B - beet

C - cloudless

D - broom

E - white goosefoot

F - Maceboard Mitt

G - sedge

H - reptiles

I - Halle sorghum

J - roof brome

K - hedgehog corns L - soybean

M - sugar beet

N - wheat

O - rice

P - sorghum

Q - buckwheat empty

R - Hemp

S - millet

T - bloody dew

cm x cm cm cm rH rH CO

h cm h xhxooxxxcmxxx

MOO H

CM rH CM O

H100mMMCN ^ CNK

HN OCOXO 'ONN rl N «rf CM

O O Q rH

CM O O O χ

rfi ti Рч

T3 fi fi o

P4 ti>

Q 44

Сч

CQ

jS «5 60

CM

C XCM

X CM 'x

XHCMXCO cnco

Kf

XCMXXXOOXXXXX

X Xi

X 00

Ji co cn

X X cn rH rH hH

Η X X -H O · C O rl X H X rl X X O XX X X

X CM X

(ХСХСМХГМХСХ1МХГМХГМХ'СМ (М ((М

CM cn. x co C

Table II

Mergers- Weeks Dose Plant species nina WAT kg / ha LMBOP number. BQDR

MM □

НННтННММНМОМгННгНт-I т-ЧтНгНгНО ^^ ОООт-НгНгНОО

ΝΟΟΗΗΗω ^ Μ ^ ΗΟΊ ^ ΗΜΗ

HHHHOMVIOHQMMtHOO

MMHHOMMOOOMMHHO -

cn

The superior properties of the compounds of the present invention are apparent from a comparison of the herbicidal activity of the compounds of the present invention with that of the 0,0-diethyl-N-phosphonomethylglycinonitrile described in U.S. Patent No. 3,923,877. It was used for testing. 11 plant species listed in Table I. When the reference compound was applied at 4.48 kg / ha, the index was 0 for all plant species. When the dose was increased to - 11.2 kg / ha, the index was equal to 1 for beet and moth, while for the other 9 plant species it was still 0.

From the test results given in Tables. and II, it follows that the post-emergence herbicidal activity of the compounds of formula (I) prepared by the process of the invention is generally of a general nature. However, some selective efficacy has been found in some specific cases. In this respect, it should be noted that every individual plant species. selected for the above testing is a typical representative of the entire known class of plant species.

Herbicidal mixtures according to. of the present invention, including the concentrate to be diluted before application to the plants, usually contain 5 to 95 parts by weight of at least one active ingredient and 5 to 95 parts by weight of the adjuvant in liquid or solid form, e.g. about 0.25-25 parts by weight of the dispersing agent. and about 4.5-94.5 parts by weight of an inert liquid filler, for example water; all parts by weight are parts by weight of the total mass of the herbicidal mixture. If desired, 0.1-2.0 parts by weight of the inert filler may be replaced by a corrosion inhibitor or antifoam agent, or both. The herbicidal mixtures according to the invention are prepared by mixing the active ingredient with an adjuvant, such as a diluent, filler, carrier or conditioning agent. and obtained. the compositions are formulated as finely divided powders, pellets, solutions, dispersions or emulsions.

For example, inert finely divided solids may be used as adjuvants for the active ingredient. liquids of organic origin, water, wetting agent, dispersing agent, emulsifying agent or any suitable combination thereof. In terms of economy and availability, the most preferred diluent is water.

The herbicidal mixtures according to the invention, in particular liquid mixtures. and wettable dusts, preferably contain, as conditioning agent, one or more surfactants in an amount sufficient to render the composition well dispersible in water or oil. The addition of a surfactant to the herbicidal mixture strongly potentiates its effectiveness. -. By "surfactant" is meant wetting agents, dispersing agents, suspending agents or emulsifying agents are added to the herbicidal mixture. As said reagents, the same result can be used - of the annionic, cationic or nonionic type.

Preferred wetting agents include alkylbenzene- and alkylnaphthalenesulfonates, sulfated fatty alcohols, amines or acid amides, long carbon chain esters of sodium isothionate, sodium sulfosuccinate esters, sulfated- or sulfonated fatty acid esters, petroleum sulfonates hydrocarbons, sulfonated vegetable oils, polyoxyethylenderivatives - phenol and alkylphenols (especially isooctylphenol and nonylphenol) - and polyoxyethylene derivatives of monoesters of higher fatty acids with anhydrohexitols (for example - sorbate). As dispersants, methylcelluloses, polyvinyl alcohol, sodium salts of lignin sulphonates, polymeric-alkylnaphthalenesulphonates, sodium salts of naphthalenesulphonate, polymethylenebisnaphthalenesulphonate and sodium salts of N-methyltaurines acylated with a long-chain nitrogen-carbonated acid are preferably used.

The water-dispersible powdered herbicidal compositions may contain one or more active ingredients, an inert solid filler and one or more wetting and dispersing agents. As inert solid fillers, mineral fillers such as natural clays, diatomaceous earth and synthetic minerals derived from silica and the like can usually be used. Examples of such fillers include kaolinity, attapulgite clay and synthetic magnesium silicate. The water-dispersible herbicidal dusts of the present invention typically contain - about 5-95% by weight of the active ingredient, about 0.25-25 parts by weight of the wetting agent, about 0.25-25 parts by weight of the dispersing agent, and about 4.5 —94.5 parts by weight of inert solid filler; all - said - parts are parts by weight of the total mass - herbicidal mixture. If desired, about 0.1-2.0 parts by weight of the solid inert filler may be replaced by a corrosion inhibitor or antifoam agent, or both. ^;

Aqueous herbicidal suspensions - can be prepared by mixing with each other - and by spreading an aqueous suspension of a water-insoluble active ingredient in the presence of a dispersant until a concentrated suspension of very finely divided particles is obtained. The concentrated aqueous suspension obtained is characterized by containing extremely small particles, so that after dilution and after spraying a very uniform coating is obtained on the plants. Said concentrated aqueous herbicidal suspensions usually contain about 5-95 parts by weight of the active ingredient, about 0.25-25 parts by weight of dispersing agent and about 4.5-94.5 parts by weight of water.

Emulsifiable oily herbicidal preparations are usually solutions of the active ingredient in a water-immiscible or partially water-miscible solvent. to which it is added. surfactant. Hydrocarbons and water-immiscible ethers, esters or ketones can be used as suitable solvents for the active compounds according to the invention. Emulsifiable oily herbicidal mixtures typically contain about 5-95 parts of active ingredient, about 1-50 parts of surfactant, and about 4-94 parts of solvent; all parts are parts by weight of the total mass of the emulsifiable oil composition.

The herbicidal mixtures according to the invention may also contain other additives, for example fertilizers, phytotoxic substances, plant growth regulators, pesticides and the like which can be used. as adjuvants or in combination with any of the above adjuvants; however, for maximum effect, it is preferable to use the herbicidal compositions of the invention alone and to apply phytotoxic agents, fertilizers, and the like sequentially. For example, the field may be sprayed with a herbicidal mixture. according to the invention either before the application of the machine. fertilizers, other phytotoxic agents and the like, or after application. Herbicidal mixtures. according to the invention, it is also possible to admix to other formulations, for example fertilizers, other phytotoxic agents and the like, and to apply the mixture. in a single operation. Chemical compounds suitable for combination with the active compounds according to the invention, either simultaneously or sequentially, are, for example, triazines, ureas. carbamates, acetamides, acetanilides, uracils, acetic acids, phenols, thiocarbamates, triazoles, benzoic acids, nitriles and the like.

Machinery fertilizers suitable for combination with the active compounds according to the invention are, for example, ammonium nitrate, urea, potash and superphosphate. .

The herbicidal mixtures according to the invention are used in such a way that:. An effective amount of the glycinonitrile of formula I is applied to the plants or parts thereof by any conventional means. The application of liquid and powdered solid herbicidal mixtures to plants or to the soil can be carried out by conventional methods, for example by means of sprayers, hand and frame machine sprayers and dusters. Due to the efficacy of the herbicidal compositions according to the invention at low doses, they can also be applied in the form of dusts. or spraying from aircraft.

In practice, it is essential and critical to apply to. plants an effective amount of compounds. according to the invention. The precise amount of active ingredient used depends on the desired reaction of the plant and also on other factors such as the type of plant being treated, the degree of the plant being treated. the development and amount of rainfall, as well as the specific type of compound used. formulas. I. When the herbicidal mixture is applied to the leaves of plants, to influence their vegetative growth, the use of a herbicidal mixture is used. active ingredient in a dosage of about 'from about 0.25 to about'. 25.0 'or more. kilograms. per hectare. An effective amount required for a phytotoxic or herbicidal effect is an amount required for total or selective. and is referred to as a 'phytotoxic or' herbicidal amount. It will be understood that one skilled in the art can readily determine from the data set forth in the specification, including examples, the approximate application rate of the herbicidal compositions described.

Although the invention has been described with respect to its specific modifications, these 'details' should not be construed as limiting its scope.

Claims (5)

OBJECT OF THE INVENTION Herbicidal composition, characterized in that it contains from 5 to 95 parts by weight of N, N‘-methylenebis- (O, O-diaryl-N-phosphonomethylglycinonitrile) of the formula I as active ingredient, NC-CH, L (0 in which R represents a phenyl group which may be further substituted by up to two substituents selected from the group consisting of halogen, alkyl, alkoxy and alkylthio, all of from 1 to 4 carbon atoms. 2. A herbicidal composition as claimed in claim 1, characterized in that it contains from 5 to 95 parts by weight of the active compound of the formula (I) in which R represents a xylyl, tolyl, phenyl or methylthiophenyl group. 3. A process for the preparation of N, N &apos; -methylenebis- (O, O-dimethyl-N-phosphonomethylglycinonitriles) of the general formula I, in which R is as defined above. The compound of claim 1, wherein the sterically hindered phenylazomethine of the formula: ## STR2 ## wherein: X is C1 -C4 alkyl and Y represents a C1-C4 alkyl group, a halogen atom or a C1-C4 alkoxy group, with the proviso that the substituents X and Y must not both simultaneously denote a tertiary butyl group with a compound of the general formula O II (RO) 2 -P-CH 2 -NH-CH 2-CN wherein R is as defined above, and the mixture is heated under reduced pressure until cleavage of the sterically hindered aniline is complete. 4. A process according to claim 3, wherein a catalytic amount of a base is added to the reaction mixture. 5. A process according to claim 3, wherein the phenylazomethine of the general formula X and Y is ethyl.