CS203175B2 - Method of preparing novel n-substituted bis-carbamoyl-sulphides - Google Patents

Description

(54) Method of preparation of new

N-substituted bis-carbamoylsulfides

The invention relates to a process for the preparation of novel N-substituted biscarbamoylsulfides which are useful for controlling insects, mites or nematodes.

The present invention provides a process for the preparation of compounds of formula (I):

Rl Rs O

II

R3-C = NOC-N-S-N-C-R1 (I),

Where n is 1 or 2,

R 1 is a fluorine atom or a group -O-N = C-R 2

AND

X — Re

X is sulfur, sulfinyl or sulfonyl, R 2, R 3, R 4, R 5, R 6 and R 6 are independently C 1 -C 8 alkyl.

The compounds of the invention are characterized in that they have significantly reduced mammalian toxicity and phytotoxicity as compared to known pesticidal active compounds with comparable spectrum of insecticidal, acaricidal and nematicidal activity.

Preferred for high pesticidal activity are those compounds of the invention wherein R 2, R 3, R 1, R 5, R 6 and R 2 substituents each contain 1 to 5 carbon atoms. Particularly preferred compounds are those wherein R 3, R 1, R 5 and R 6 are methyl. Other preferred compounds of the invention are those wherein R 1 is a fluorine atom in view of their further utility as intermediates for the preparation of pesticidally active compounds by reaction with oximes, hydroxylated aryl compounds or other active hydrogen containing compounds. For example, O- [N-methyl-N- (N'-methyl-N'-fluoroformylaminosulfenyl) carbamoyl] oxime-1-methylsulfinylacetaldehyde can be reacted with 2,2 dimethyl-2,3 dihydro-7- with hydroxybenzofuran in the presence of triethylamine as an acid acceptor to give N- [1-methylsulfinylacetaldehyde-O- (N'-methylcarbamoyl) oxime] -N- [2,2-dimethyl-2,3-dihydro-7- (N'-methylcarbamoyloxybenzofuran) sulfide corresponding to pesticidally active carbamate compounds.

The compounds of the invention can be prepared by the compound of formula II,

R 3 = O = NOH

I (Π)

R2-S (O) _n wherein R2, R3 and _n are as defined above, react with a compound of formula III,

O R4 Rs O

II

F - C - N - S - N - C - R 1 (III) wherein R 1, R 4 and R 5 are as defined above, then when a compound of formula I wherein R 1 is other than fluorine is prepared, the resulting product of formula Wherein R 1 is a fluorine atom and

R 2, R 3, R a and R 5 and n are as defined above, with a compound of formula IV,

HON — C — R7

I (IV)

X - Re wherein R e, R z and X are as defined above in the presence of at least one equivalent of an acid acceptor.

The reactions are carried out by mixing together an equivalent amount of the reactants in an inert solvent. Examples of inert solvents useful in the process of the invention are benzene, toluene, methylene chloride, xylene, dioxane, tetrahydrofuran and the like.

The reaction temperatures are not critical and can be varied over a wide range depending on the reactivity and the thermal stability of the reactants. Preferred reaction temperatures are from -30 ° to 100 ° C.

Reaction pressures are not critical. Preferably, the reaction is conveniently carried out at atmospheric or autogenous pressure.

These reactions are carried out in the presence of an acid acceptor. The molar ratio of acid acceptor is normally equivalent to the molar ratio of oxime present in the reaction mixture, although a slight excess of acid acceptor may optionally be used. The acid acceptor may be either an organic or inorganic base.

Examples of organic bases useful as acid acceptors are tertiary amines, alkali metal alkoxides and the like. Examples of inorganic bases useful as acid acceptors are sodium hydroxide, potassium hydroxide, and the like. Preferred acid acceptors are tertiary amines such as triethylamine, pyridine, trlmethylamine, 1,4-diazabicyclo - [2,2,2] octane and the like

These reactions can be carried out in a homogeneous (single-phase) system or using inorganic bases as acid acceptors in a heterogeneous phase system. In this case, phase transfer facilitators such as crown ethers, quaternary ammonium halides and the like are used. For example, when a solid inorganic base acid is used as an acceptor in an organic medium, crown ether transfer facilitators are used, or alternatively when these reactions are carried out in a two-phase system consisting of an aqueous solution of an inorganic base as one phase and an organic solvent containing dissolved other phases, quaternary ammonium halides may be used as phase transfer facilitators.

The oximes used as reagents in the preparation of the compounds of the invention can be prepared by a number of methods. For example, 1-methylthioacetaldoxime can be prepared by reacting acetaldehyde with hydroxylamine hydrochloride to form acetaldoxime, which is then treated with chlorine in hydrochloric acid as solvent to form 1-chloroacetaldoxime, which is then reacted with sodium methylmercaptide to produce the desired aldoxime. The 1-methylthioaldoxime is then readily converted to the 1-methylsulfinyl and 1-methylsulfonyl derivatives by peracid oxidation. The method described above, together with other methods for preparing oximes, is described in more detail in U.S. Patents 3,752,841, 3,726,908, 3,843,669 and in Belgian patents 813,206 and 815,513.

The bis- [N-alkyl-N-fluorocarbonylamino] sulfides used as reactants in the preparation of the compounds of the invention can be prepared by a number of methods. One preferred method consists in reacting hydrogen fluoride with an appropriately substituted alkyl isocyanate to form the corresponding alkylaminocarbonyl fluoride which is then reacted with sulfuryl chloride (SCiz) in the presence of at least two equivalents of the acid acceptor described above, preferably in an inert solvent to form bis- (N-alkyl N). -fluorocarbonylamino sulfide.

The following examples illustrate the invention in more detail.

Example 1

Preparation of N ', N' -bis- (N-methyl-N-fluorocarbonylamino) sulfide

To a polypropylene reactor containing 80 g (4.0 mol of hydrogen fluoride in 1800 ml of toluene cooled to -40 ° C) was added dropwise 228 g (4.0 mol) of methyl isocyanate dropwise over 20 minutes. 60 g (2 mol) of freshly distilled sulfuryl dichloride are added, followed by the slow addition of pyridine (346 g, 4.4 mol) at 20 to 0 ° C. After stirring at room temperature for 16 hours at room temperature, the reaction mixture is diluted with 500 ml of water and the toluene phase is then washed (3 X 500 ml of water), dried and distilled to give 244 g (66%) of product. mp 40-41 ° C.

Calcd. For C 4 H 6 F 2 N 2 O 2 S: C 26.09, H 3.28,

N, 15.21. Found: C, 26.19; H, 3.20; N, 14.79.

Example 2

Preparation of 1-methylsulfinyl- [N-methyl-N- (N'-methyl-N'-fluorocarbonylaminosulfenyl) carbamoyloxy] acetimidate

To a solution of 4.0 g (0.033 mol) of methylsulfinyl-N-hydroxyacetimidate and 6.07 g (0.033 mol) of Ν, Ν'-bis- (N-methyl-N-fluorocarbonylamino) sulfide in 100 ml of toluene was added dropwise 3.34 stirring. g (0.033 mol) of triethylamine dissolved in 50 ml of toluene. After stirring overnight, the solid is filtered (the desired material is contaminated with bis-carbamate). The filtrate was washed with water, dried and concentrated to give 0.5 g of product. The total weight of the material obtained from both portions is 1.55 g, m.p. 120-125 ° C (dec.

IR (KBr) 5.55 (CO), 5.78 (CO)

NMR (CDCl 3) δ 2.36 (s, 3H, CH 3, 2.85 (s), 3H,

CH 3 SO, 3.43 (s), 6H, CH 3 N.

Example 1 a d 3

Preparation of S-methyl-N- {N '- [N' - (1-methylsulfinylethyldiminoxycarbonyl) N '-methylaminosulfenyl] -N' -methylcarbamoyloxy} thioacetimidate

Mixture containing 2.42 g (0.02 mol) of methylsulfinyl-N-hydroxyacetimidate, 5.5 g (0.02 mol) of methyl [N-methyl-N- (N'-methyl-N'fluorocarbonylaminosulfenyl) carbamoyloxy of thioacetimidate and 2.02 g (0.02 mol) of triethylamine in 100 ml of toluene were heated at 50-60 ° C for 4 hours and then stirred at room temperature overnight. The solid was filtered and dissolved in methylene chloride. The organic solution was washed with water, dried and concentrated. Crystallization of the residual oil from a mixture of ethyl acetate and methylene chloride gave 3.8 g of a solid, mp 140-141 ° C.

Calcd for C 10 H 18 N 4 O 5 S 3: C 32.34, H 4.90,

N, 15.12.

Found: C 32.41, H 4.91, N 14.86.

Example 4

Preparation of S-methyl-N- {N '- [N' - (1-methylsulfonylethylidiniminooxycarbonyl) -N'-methylaminosulfenyl] -N '-methylcarbamoyloxy} thioacetimidate

To a suspension of 5.26 g (0.019 mol) of about 95% methyl [N-methyl-N- (N'-methyl-N'-fluorocarbonylaminosulfenyl) carbamoyloxy] thioacetimidate and 2.61 g (0.019 mol) methylsulfonyl-N Hydroxyacetimidate in 100 ml of toluene was added with stirring 1.92 g (0.019 mol) of triethylamine diluted in 50 ml of toluene. After stirring at room temperature for 3 hours, the solid was filtered off. Crystallization from chloroform / ethanol gave 5 g of product, m.p. 120-123 ° C.

Calcd for C 10 H 18 N 4 O 6 S 3: C 31.08, H 4.69,

N, 14.50.

Found: C 30.95, H 4.79, N 14.22.

Example 5

Preparation of 1-methyl-N- {N '- [N' - (1-methylsulfinylethylidiniminooxycarbonyl) -N'-methylaminosulfenyl] -N '-methylcarbamoyloxy) sulfinylacetimidate

To a solution of 8.0 g (0.07 mol) of methylsulfinyl-N hydroxyacetimidate and 6.45 g (0.035 mol) of Ν, Ν'-bis- (N-methyl-N-fluorocarbonylamino) sulphide in 100 ml of toluene is added dropwise 7, 08 g (0.07 mol) of triethylamine. After 15 minutes a white solid began to precipitate. After stirring at room temperature for 18 hours, the solid was filtered off and dissolved in methylene chloride. The organic solution was washed with water, dried and concentrated to a solid. Crystallization from methylene chloride and toluene yielded

5.4 g of white solid, mp 131-134 ° C.

Calcd for C 10 H 18 N 4 O 8 S 3: C 31.08, H 4.69,

N, 14.50. Found: C, 31.35; H, 4.54; N, 13.94.

Example 6

Preparation of 1-methylsulfonyl-N- {N '- [N' - (1-methylsulfonylethylidiniminooxycarbonyl) -N'-methylaminosulfenyl] -N '-methylcarbamoyloxy] acetimidate

To a solution of 5.0 g (0.0365 mol) of methylsulfonyl-N-hydroxyacetimidate and 6.72 g (0.0365 mol) of Ν, Ν'-bis- (N-methyl-N-fluorocarbonylamino) sulfide in 150 ml of toluene was added. 3.69 g (0.0365 mol) of triethylamine are added. After stirring for 16 hours, the solid was filtered off and crystallized to give 1.1 g of a white solid, mp 173-175 ° C (dec.). The filtrate is predominantly the monoadduct S of methyl- [N-methyl-N- (N'-methyl-N'-fluorocarbonylaminosulfenyl) carbamoyloxy] sulfonate of lacetimidate.

Calcd for C10H18N4O8S3: C, 28.70, H, 4.33,

N, 13.39. Found: C, 28.64; H, 4.31; N, 13.29.

Example 7

Preparation of 1-ethyl-N- {N '- [N' - (1-ethylsulfinylethylidiniminooxycarbonyl) -N'-methylaminosulfenyl) -N´-methylcarbamoyloxy} sulfinylacetimidate

To a solution of 1.45 g (0.004 mol) of S-ethyl-N- (N'- [N '- (1-ethylthioethylidiniminooxycarbonyl) -N'-methylaminosulfenyl] -N'-methylcarbamoyloxy] thioacetimidate in 25 mL of ethyl acetate cooled to 5 ° C 2.32 g of a 25% solution of peracetic acid in ethyl acetate is added, stirring is continued for 16 hours at room temperature, the reaction solution is concentrated and the residual oil is crystallized from a mixture of isopropyl ether and ethyl acetate. m.p. 108-110 ° C (dec.).

Calcd for C12H22N4O6S3: C 34.13, H 5.40,

N, 13.65. Found: C, 33.90; H, 5.26; N, 13.29.

The following compounds are examples of compounds which are within the scope of the invention and which can be prepared using the appropriate starting materials described above:

1-Isopropylsulfinyl- [N-methyl-N- (N'-methyl-N‘-fluorocarbonylaminosulfenyl) carbamoyloxy] acetimidate

1-Pentylsulfonyl- [N-methyl-N- (β-methyl · N--fluorocarbonylaminosulfenyl) carbamoyloxy] acetimidate

S-isopropyl-N- (N '- (N' - (1-methylsulfonylethylidiniminooxycarbonyl) -N'-methylaminosulfinyl] -N '-methylcarbamoyloxy) thioacetimidate,

S-isopropyl-N- {N '- [N' - (1-isopropylsulfinylethylidiniminooxycarbonyl) -N'-methylaminosulfenyl] -N '-methylcarbamoyloxy} thioacetimidate,

S-isopropyl-N- (N '- [N' - (1-isopropylsulfonylethylidiniminooxycarbonyl) -N '-methylaminosulfenyl] -N' -methylcarbamoyloxy} thioacetimidate,

1-Isopropylsulfonyl- [N-methyl-N- (N '-methyl-N' -fluorocarbonylaminosulfenyl) carbamoyloxy] acetimidate

1-butylsulfinyl- [N-methyl-N- (N'-methyl-N'-fluorocarbonylaminosulfenyl) carbamoyloxy] acetimidate.

Selected species of novel compounds have been tested for their pesticidal effect against mites and some insect species including aphids, caterpillars, beetles and flies.

A suspension of the test compounds is prepared by dissolving one gram of the compound in 50 ml of acetone in which 0.1 g (10% by weight of the compound) of alkylphenoxypolyethoxyethanol is dissolved as an emulsifying or dispersing agent. The resulting solution was combined in 150 mL of water to give 200 mL of a suspension containing the compound in finely divided form. The stock solution thus prepared contains 0.5 wt. test compounds. The test ppm concentration used in the tests described below is obtained by appropriately diluting the stock suspension in water. The procedure used to perform the tests is as follows:

Bean aphids, leaf spray test

Bean aphid adults and nymphs (Aphis fabae Scop.j) grown on stunted cress in pots at 18-21 degrees Celsius and 50-70 percent relative humidity were used as test insects. For testing, the number of aphids per pot was standardized to 100- 150 by removing parts containing excess aphids from the plants.

Test compounds were treated by diluting the stock suspensions with water to give a suspension containing 500 parts of test compound per million parts of the final formulation.

Plants in pots (one pot per test compound) infected with 100-150 aphids were placed on a rotating table and sprayed with 100-110 ml of the compound containing the test compound using a DeVilbiss gun at an air pressure of 31.38 MPa. As a control, 100 to 110 ml of an emulsifier solution in water and acetone, containing no test compound, was also used as a control and also sprayed infected plants.After spraying, the pot was placed on sheets of standard mimeographic paper to facilitate The test room temperature and humidity were maintained at 18-21 ° C and 50-70% humidity for 24 hours.The aphids that fell on paper and were unable to stand after conversion were counted dead. observations were not sch The percentages of mortality were calculated for different concentration levels.

Prodenia eridania, leaf spray test

Prodenia aridania (Cram) larvae, grown on Tendergreen beans at a temperature of 24 ° C + 3 ° C with a relative humidity of 50 + 5%, were used as insects for the tests.

Test compounds were treated by diluting the stock suspension with water to give a suspension containing 500 parts of test compound per million parts of final formulation. Standard height and age bean plants were placed on a rotating stage and sprayed with 100-110 ml of a composition containing test compounds using a DeVilbiss gun at an air pressure of 6.86 MPa.

This spraying lasted 25 seconds and was sufficient to wet the rotating plant. As a control, 100-110 mL of a 2020175 flow of emulsifier in water and acetone containing no test compound was used. Infected plants were also sprayed with this solution. After drying, the pair of sheets were separated and each sheet was placed in a 9 cm petri dish with moistened filter paper. Five randomly selected larvae are transferred to each dish and sealed. The sealed dishes are labeled and kept at temperature for three days

26.5 to 29.5 ° C. Although larvae can easily eat the entire leaf within 24 hours, no food is added. Larvae that do not move along the length of their body after stimulation by nudging are considered dead. Percent mortality is determined for various concentrations. Epilachna varivestis, leaf spray test

The fourth instar larvae of Epilachna varivestis (Must) were grown on Tengergreen beans at a temperature of 26 + 3 ° C and a relative humidity of 50 + 5% and then used for the tests.

Test compounds were adjusted by diluting the stock stock suspension with water to give a suspension containing 500 parts of test compound per million parts of final formulation. Tendergreen bean plants of standard height and age are placed on a rotating stage and sprayed with 100-110 ml of the test compound composition using a DeVilbiss gun at an air pressure of 6.86 MPa. This spraying lasted 25 seconds and was sufficient to wet the rotating plant. As a control, 100 to 110 ml of a solution of emulsifier in water and acetone containing no test compound was used. Infected plants were also sprayed with this solution. After drying, the pair of sheets were separated and each sheet was placed in a 9 cm petri dish with moistened filter paper. Five randomly selected larvae are transferred to each dish and sealed. The sealed dishes are labeled and kept at temperature for three days

26.5 + 3 ° C. Although larvae can easily eat the entire leaf within 24 hours to 48 hours, no food is added. Larvae which, even after stimulation, do not move about the length of their body are considered dead.

Fly bait test

Adult house flies (Musea domestica L) aged 4 to 6 days, grown according to the Chemical Specialties Manufacturing Association (Blue Book, McNair-Dorland Co., NY, 1954, pp. 243-244, 261) under controlled conditions at 26 + 3 ° C and 50 + 5% relative humidity are used as insects for testing. The flies are immobilized by carbon dioxide anesthesia and 25 immobilized flies, males and females are transferred to a cage consisting of a standard kitchen sieve of about 12.5 cm diameter, which is facing the surface covered with wrapping paper. The test compounds are adjusted by diluting the stock suspension with 10% w / w. sugar solution so as to obtain a suspension containing 500 parts of the test compound per million parts of the final composition. Ten milliliters of the test composition is added to a foam insert containing 6.4 cm ^{2 of} absorbent cotton. This bait is added to the center of the sieve paper pad before adding anesthesia to the immobilized flies. Flies in the germ are allowed to feed on the bait for twenty-four hours at a temperature of 26 + 3 ° C and a relative humidity of 50 + 5%. Flies that show no sign of movement are considered dead.

Mites, leaf spray test

Adults and spider mite nymphs (Tetranychus urticae Koch) grown on Tendergreen beans at 80 + 5% relative humidity are used as test organisms. Infected leaves from the basic culture were placed on primary leaves of two bean plants 15-20 cm tall, growing in pots of 6 cm in size. 150 to 200 mites are sufficient for the test, transferred from torn leaves to fresh plants within 24 hours. After 24 hours of transfer, the torn leaves are removed from the infected plants. Test compounds are adjusted by diluting the stock stock suspension with water to obtain a suspension with water containing 500 parts of test compounds per million parts of the final formulation. Plants in pots (one pot per compound) are placed on a turntable and sprayed with 100 to 110 ml of the composition containing the test compound using a DeVilbiss gun at 31.38 MPa air pressure. This spraying lasted 25 seconds and was sufficient to wet the rotating plant. As a control, 100 to 110 ml of a solution of emulsifier in water and acetone was used in which no test compound was contained. Infected plants were also sprayed with this control solution. Sprayed plants were maintained at a relative humidity of 80 + 5% for 6 days, and mortality was calculated. Microscopically observed forms capable of movement on leaves of test plants were observed. Any individual capable of moving after being nudged was considered alive.

The results of these tests are shown in Table I. In these tests, the pesticidal effect of the compounds on aphids, mites, Prodenia eridania, Epilachna varivestis and housefly was evaluated according to the following grades:

A = excellent control

B = partial check

C = no control

Toxicity to mammals

Some of these compounds have also been tested to determine oral toxicity in mammals. Rats were selected as animals for these tests. The results of these tests are expressed in mg of compounds per kg of animal required to achieve 50% mortality (LD50).

203178

Structure Biological data Aphids mites Prodenia Epilachna fly LDso / rat eridania varivestis

CHrC = NOC-N = 3 i s = o

ČJK

The results shown in Table I clearly show the broad spectrum and high pesticidal effect of the compounds of the invention, it being understood that the pests used are representative of the various pests that can be controlled by the compounds of the invention.

The compounds of the invention may be applied as insecticidal, acaricidal and nematicidal agents by known methods. Pesticidal compositions containing the compounds as active toxic substances typically comprise a carrier and / or diluent, either liquid or solid.

Suitable liquid diluents or carriers include water, distillate fractions of kerosene or other liquid carriers, with or without the use of surfactants. Liquid concentrates can be prepared by dissolving one of these compounds with a non-phytotoxic solvent such as acetone, xylene or nitrobenzene and dispersing the toxic agents in water with an acid or a suitable surfactant emulsifier and dispersant.

The choice of dispersing and emulsifying agents and the amount used will depend upon the type of formulation and the ability of the agent to facilitate dispersion of the toxic agent. In general, it is desirable to use the smallest amount of agent required to disperse the toxicant in the spray so that the rain does not re-emulsify the toxicant after application to the plant and does not wash it with the plants. Thus, nonionic, anionic, amphoteric or cationic dispersing and emulsifying agents can be used, for example, condensation products of alkylene oxides with phenol and organic acids, alkylarylsulfonates, complex ether alcohols, quaternary ammonium compounds and the like.

In the preparation of wettable powders or dusts or granular compositions, the active ingredient is dispersed in an appropriately dispersed solid carrier such as clay, talc, bentonite, diatomaceous earth, fuller's earth and the like. The above dispersing agents, as well as lignosulfates, may be added. .

The required amount of toxic substances may be applied per hectare together with 11 liters to 2200 liters of liquid carrier and / or diluent or 5.5 to 550 kg of inert carrier and / or diluent. The concentration in the liquid concentrate is typically from about 10 to 95 percent by weight and in the solid composition from about 0.5 to 90 percent by weight. Suitable sprays, dusts or granules for general use contain from about 0.27 to 16.5 kilograms of active toxicant per hectare.

The pesticidal compounds of the present invention protect plants or other materials to which pesticides are applied from insect, nematode and mite attack and have relatively high residual toxicity. The plants have been found to be sufficiently safe to be used in an amount sufficient to kill insects or repellents, causing no damage to the plants and resistant to rain wash, ultraviolet degradation, oxidation or hydrolysis in the presence of moisture or at least to such degradation , oxidation and hydrolysis, which reduce desirable pesticidal or toxicity characteristics or affect undesirable characteristics such as phytotoxicity. Toxic compounds are also chemically inert so that they are compatible with the other components of the spray and can be used in soil, seed, plant roots without damaging the seeds or roots. Mixtures of the active compound of the invention may also be used in combination with other biologically active compounds.

Claims (6)

Subject A process for the preparation of novel N-substituted bis-carbamoylsulfides of the general formula I, O R4 Rs O R3-C-NOC-N-S-N-C-R1 (I) R2 wherein n is 1 or 2, R 1 is a fluorine atom or a group -O-N = C-R 7 X — Re X is sulfur, sulfinyl or sulfonyl, R @ 2, R @ 3, R @ 1, R @ 5, R @ 6 and R @ 7 are unsaturated alkyl groups having from 1 to 8 carbon atoms; R3 = C = NOH I (Π) R 2 -S (O) _n wherein R 5, R 3 and _n are as defined above, react with a compound of formula III, O R4 Rs O F - C - N - S - N - C - R 1 (III) wherein R 1, R 6 and R 5 are as hereinbefore defined, and optionally, to prepare a compound of formula I wherein R 1 is other than an atom of fluorine, allowed to react, the resulting product of formula I, wherein R 1 is fluorine and R 2, R 3, R 4 and R 5a.11 are as defined above, with a compound of formula IV. HON = C - R 7 I (IV) X - R e wherein R 6, R 2 and X are as defined above, in the presence of at least one equivalent of an acid acceptor. 2. A process according to claim 1, wherein the starting materials are compounds of the formulas II, III or IV, wherein R2, R3, R4, R5, R6 and R7 are alkyl of 1 to 5 carbon atoms. 3. A process according to claim 1, wherein the starting materials are compounds of formula III wherein R4 and R5 are methyl. 4. A process according to claim 1 wherein the starting materials are compounds of formulas II or IV wherein R3 and R7 are methyl. 5. A process according to claim 1, wherein the starting material is a compound of formula III wherein R1 is fluorine. 6. A process according to claim 1, wherein the compound of formula (III) wherein R1 is a group is used as the starting material