The present invention relates to benzoylurea derivatives having insectididal activity and, in particular, it relates to l-benzoyl-3-aryl-urea derivatives which are particularly active against eggs and larvae of insects noxious in the agrarian and civil field, as well as to the use of these derivatives and a process for their preparation.

Several 1-benzoyl-3-aryl-urea derivatives having insecticide activity are known.

Among them, Diflubenzuron (generic name for 1-(2,6-difluorobenzoyl)-3-(4-chlorophenyl)-urea) which is described in US-A-3 993 908 has been the first product to be marketed. However, Diflubenzuron is suspected of being a carcinogen [European Chem.News 6 (16), 29 (1978)], as it contains a 4-chloroaniline unit in its molecule.

An object of the present invention are 1-benzoyl-3-aryl-urea derivatives having the general formula:

wherein:

• _R is chlorine or fluorine;
• R₁ is hydrogen, chlorine or fluorine;
• R₂ and R_3' which are the same or different from each other, represent hydrogen, halogen or alkyl containing to 1 to 4 carbon atoms;
• R₄ and R₅, which are the same or different from each other, represent hydrogen, halogen, alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy or alkynyl;
• R₆ and R₇₁ which are the same or different from each other, represent hydrogen or alkyl containing 1 to 3 carbon atoms, optionally substituted by halogen;
• Y represents hydrogen or fluorine;
• n is an integer of from 1 to 4.

Among the aforesaid definitions the term halogen preferably refers to a fluorine, chlorine, or bromine atom. The compounds of formula (I) exhibit insecticide activity and may be used in the agrarian, forestal, civil and veterinary field for combatting insect infestations.

In the following description of the preparation of the compounds of formula (I) the symbols R, R₁, R₂, ^R₃, ^R₄, ^R₅, R₆, R₇₁ Y and n have the meanings indicated for formula (I), if not specified otherwise. The compounds of formula (I) are obtained by reacting a benzoyl-isocyanate having the formula:

with an aromatic amine having the formula:

The reaction does not require the presence of catalysts and is carried out in an inert solvent at a temperature ranging between 0°C and the boiling temperature of the mixture.

Suitable solvents are e.g. aromatic hydrocarbons, chlorinated hydrocarbons, ethers, ketones and acetonitrile.

The benzoyl-isocyanates-of formula (II) are known compounds, some of them being commercially available.

The amines of formula (III) may be prepared in a manner known per se, for instance by:

• a) reaction of a sodium or potassium salt of a suitable amino-phenol (IV) in a dipolar aprotic solvent with a compound of formula:

  wherein X is halogen such as
  
  

  Cl, Br, J or a tosyl or mesyl group, at a temperature of from 0 to 150°C, according to the following reaction scheme:

• b) reduction, according to known techniques, of a nitro- derivative of formula:

The nitroderivatives of formula (VI) may in turn be prepared, according to known methods, by reacting a suitable 4-halonitrobenzene (VII) with a sodium or potassium salt of an alcohol (VIII) in a solvent system consisting of . said alcohol (VIII) or in an aprotic apolar solvent, or carrying out the reaction according to the phase transfer technique in the presence of a suitable catalyst at temperatures ranging between 10 and 150°C, according to the following reaction scheme:

wherein X is halogen.

The alcohols of formula (VIII) are known and may be prepared according to the following reaction scheme:

wherein X is halogen and Me is a metal selected from Zn, Mg and Cu.

Organometallic compound (IX) may be prepared by reacting compound X(CF₂)_nX with Zn, Mg or Cu.

The nitroderivatives of formula (VI), in which at least one of radicals R₂, R₃, R₄ and R₅ is chlorine, may also be obtained by direct chlorination with Cl₂ of the corresponding non-chlorinated nitroderivatives at temperatures ranging between 25 and 150°C and in the presence of a catalyst such as e.g. FeCl₃ and SbCl₅.

For those skilled in the art, it is a matter of course that different alternative processes may be used for the synthesis of the intermediates and of the end products having formula (I).

An alternative process for the synthesis of the compounds of formula (I) comprises, for instance, reacting a benzamide of formula:

with an isocyanate of formula:

This reaction is carried out under conditions similar to those described hereinbefore for the reaction between the benzoyl-isocyanate of formula (II) and the amine of formula (III).

The preparation of the isocyanates of formula (XII) involves, however, the preparation of the amines of formula (III) and their reaction with phosgene. This aspect, together with the consideration that the benzoyl-isocyanates of formula (II) are commercially available,as the amides of formula (XI) are, generally renders the method mentioned hereinbefore, namely the reaction between the compounds of formulae (II) and (III) more preferable.

As mentioned above, the compounds of formula (I) exhibit high insecticide activity, particularly against larvae and eggs of insects. Among these,insects belonging to the orders Lepidoptera, Diptera and Coleoptera, are especially amenable of being combatted by means of the compounds of formula (I). These orders comprise many species which are important owing to their noxiousness in the agrarian, forestal, civil and veterinary fields.

Therefore, the compounds of formula (I) are suitable for many different utilities, for instance, for protecting agricultural cultivations against infestations of phyto- phagous insects, for protecting environments infested with mosquitoes and flies, for protecting breeding cattle against cattle parasites, etc. Furthermore, the compounds of formula (I) show a collateral acaricide activity.

For practical use, the compounds of formula (I) may be utilized either as such or, more conveniently, in the form of compositions containing, besides one or more of the compounds of formula (I) as active component, inert solid or liquid carriers and,optionally, other additives.

As with conventional formulations, the compositions according to the present invention may be in the form of wettable powders, emulsifiable concentrates, etc. The amount of active component in these compositions may vary within wide ranges (1-95% by weight), depending on the type of composition and on the intended use.

If required by particular situations or in order to enlarge the spectrum of activity, other active substances such as e.g. known insecticides or acaricides may be added to the compositions.

The amount of active substance (compound of formula I) to be distributed for the insecticide treatments depends on different factors such as, for instance, the type and degree of infestation, the environment infested (agrarian cultivation, basins, water-courses, organic substrates of different nature), the type of the composition employed, climatic and environmental factors, the applicator means used, etc. Generally, amounts of the active substance within the range of from 0.01 to 1 kg/ha are sufficient for a good disinfestation.

The following non-limiting examples are given in order to illustrate the invention.

In these examples, the following abbreviations are used in the NMR spectra (¹H-NMR):

• s = singlet
• m = multiplet or unresolved complex signal
• b = (broad) = broad signal
• ABq = quartet of AB type.

EXAMPLE 1

Preparation of N-(2-chloro-benzoyl)-N'-[3,5-dichloro-4--(2,2,3,3,4,4,5,5-octafluoropentyloxy) phenyl/ urea (compound No. 1)

1.0 g of 3,5-dichloro-4-(2,2,3,3,4,4,5,5-octafluoropentyloxy)aniline (prepared according to subsequent example 3), dissolved in 15 ml of anhydrous ether, was introduced into a 50 ml two-neck flask, equipped with a cooler, a dropping funnel and a magnetic stirrer.

Then, 0.7 g of 2-chlorobenzoylisocyanate, dissolved in 5 ml of anhydrous ether, were dripped at room temperature. The mixture was kept under stirring for 30 minutes, filtered under nitrogen and the precipitate was washed with ether and finally dried unter nitrogen. 0.78 g of benzoylurea were obtained, having a melting point of 173-175°C.

EXAMPLE 2

Starting from the anilines described in subsequent example 3 and using 2-chlorobenzoyl-isocyanate,the following compounds were prepared under conditions similar to those described in example 1:

• - compound No.2: N-(2-chlorobenzoyl)-N'-[4-(2,2,3,3,4,4, 5,5-octafluoropentyloxy)phenyl] urea

  m.p. = 140 -142°C.

• - compound No.3: N-(2-chlorobenzoyl)-N'-[3-chloro-4-(2,2, 3,3,4,4,5,5-octafluoropentyloxy)phenyl]urea

  m.p. = 155 -157°C.

Additionally, the following compounds were prepared using 2,6-difluorobenzoylisocyanate:

• - compound No. 4: N-(2,6-difluorobenzoyl)-N'[4-(2,2,3,3, 4,4,5,5-octafluoropentyloxy)phenyl]urea

  m.p. = 168 -170°C.

• - compound No.5: N-(2,6-difluorobenzoyl-N'-[3,5-dichloro-4-(2,2,3,3,4,4,5,5-octafluoropentyloxy)phenyl]urea

  m.p. = 155 -157°C.

EXAMPLE 3

Preparation of intermediate anilines 29.6 millimoles of SnCl₂·H₂O were introduced into a 50 ml two-neck flask, equipped with a reflux cooler, a dropping funnel and a stirrer, and dissolved in 10 ml of 37% HC1.

Then, 10 ml of a methanolic solution were dripped, containing 5.92 millimoles of 2,6-dichloro-4-nitrophenyl-2,2,3,3, 4,4,5,5-octafluoropentylether. The mixture was heated at 60°C for 30 minutes, thereafter cooled down, poured into a 10% solution of NaOH, extracted by means of ethylether and the ethereal extract was dried with Na₂SO₄ and finally concentrated. 2 g of 3,5-dichloro-4-(2,2,3,3,4,4,5,5-octafluoropentyloxy)aniline were obtained in a yield of 86%. ¹H-NMR: 6.5(s, 2H, arom.); 6.9-6.0-5.15 (tt, 1H, -CHF₂); 4.3 (t, 2H, -CH₂0); 3.5 (s, 2H, -NH₂).

By operating under conditions similar to the ones described hereinbefore and starting from 4-nitrophenyl-2,2, 3,3,4,4,5,5-octafluoropentylether, 4-(2,2,3,3,4,4,5,5-octafluoropentyloxy) aniline was obtained in a yield of 95%.

¹H-NMR: 6.7 (d, 4H, arom.); 6.8-6.1-5.2 (tt, 1H, -CHF₂); 4.35 (t, 2H, -CH₂O-); 3.5 (s, 2H, -NH₂).

Furthermore, starting from 2-chloro-4-nitrophenyl-2,2,3,3, 4,4,5,5,-octafluoropentyloxy) aniline was obtained in a yield of 83.6%.

¹_H-_NMR: 6.9-6.5 (m, 3H, arom.); 6.8-6.1-5.2 (tt, 1H, -CHF2) 4.4 (t, 2H, -OCH₂-); 3.5 (s, 2H,-NH₂).

EXAMPLE 8

Determination of the insecticide activity.

Test 1

Residual immediate activity against larvae of Spodoptera littoralis (Lepidoptera).

Tobacco leaves were treated by mechanical spraying with a water-actetone solution of the product to be tested, having an acetone content of 10% by volume and containing a surfactant. After complete evaporation of the solvents, the leaves were infested with second instar larvae of Lepidoptera. The infested leaves were kept in a suitably conditioned environment throughout the test.

For comparison, tobacco leaves were infested and kept after having been treated with a water-acetone solution containing 10% of acetone and the surfactant only (control treatment).

Ten days after the infestation and after having renewed at least once the treated substrate, a number of dead larvae as compared to the control treatment was determined.

Test 2

Activity against larvae of Aedes aegypti (Diptera). Plain water (297 ml) was mixed with an acetone solution (3 ml) of the product to be tested in a suitable concentration. 25 Diptera larvae, 4 days of age and suitably fed, were introduced into the obtained solution. For comparison, other larvae were introduced into a water-acetone solution (3 ml acetone, 297 ml plain water) without any active substance.

Every 2-3 days, the number of dead larvae and pupae and of the adults emerging normally from the cocoon, was noted until there occured no more emergence from the cocoon of the insects in the comparative solution.

The activity of the product under examination was expressed as the percent ratio of dead individuals, compared to the total number of treated individuals.

The insecticide activity in the above mentioned tests was expressed according to the following evaluation:

• 5 = complete activity (98-\00% mortality)
• 4 = high activity (80-97% mortality)
• 3 = fair activity (60-79% mortality)
• 2 = sufficient activity (40-59% mortality)
• 1 = poor activity (20-39% mortality)
• 0 = negligible or no activity (0-19% mortality).

The following Table 1 shows the insecticide activity of the tested compounds at the dosages indicated.

as described in US-A-3 993 908.

In the formulae given hereinabove and in the claims, the alkyl, haloalkyl, alkoxy and haloalkoxy groups are straight-chain or branched groups which preferably contain 1, 2, 3, 4, 5 or 6 carbon atoms and, more preferably, 1, 2, 3 or 4 carbon atoms.

The alkenyl, haloalkenyl, alkenyloxy, haloalkenyloxy and alkynyl groups are straight-chain or branched groups which preferably contain 2, 3, 4, 5 or 6 carbon atoms and, more preferably, 2, 3 or 4 carbon atoms.