IE913706A1 - Triazolopyridazine derivatives - Google Patents

Abstract

Herbicides of formula (I) in which X denotes a halogen, a group R<1>, alkoxy or a hydrogen atom; Y and Z independently denote hydrogen, a halogen, an R<1>, -OR<1>, -SR<1>, -NR<2>R<3> or cyano group; Ar denotes an optionally substituted phenyl group or a penta- or hexagonal heterocyclic ring containing one or more heteroatoms chosen from O, S and N, which is optionally substituted, R<1> is a straight-chain or branched alkyl group; R<2> and R<3> independently denote a hydrogen atom or a straight-chain or branched alkyl group; R<4> denotes an optionally substituted phenyl group; R<5> denotes a penta- or hexagonal heterocyclic ring containing one or more heteroatoms O, S or N; m has the value of zero, 1 or 2; and their agriculturally acceptable salts. The invention also relates to the herbicidal compositions containing the product of formula (I). Application: methods of combating weeds by means of the compounds of formula (I) or of compositions containing them.

Description

The present invention relates to novel herbicidal compounds of the l,2,4-triazolo[4,3-b] pyridazine family, and also to their methods of preparation, to compositions containing them and to their use in combating weeds.

The ptesent invention seeks to provide compounds which are useful both as pre-emergence (or pre-germination) and post-emergence (or postgermination) herbicides.

The present invention further seeks to provide compounds which are useful both against weeds of the monocotyledonous type and those of the dicotyledonous type.

The present invention further seeks to provide compounds which are useful as pre- and/or post-emergence herbicides which are selective for monocotyledonous crops (in particular wheat, maize and rice) and for dicotyledonous crops (in particular colza, soybean and sunflower).

In the present account, the term lower describing a radical is understood as meaning that this radical may have no more than 4 carbon atoms.

The present invention provides l,2,4-triazolo-[4,3-bj pyridazines of formula (I): wherein X represents a halogen atom or R1 or an alkoxy group, or a hydrogen atom; Y and Z independently represent:IE 913706 hydrogen, halogen, Rl, -ORl, -SRl, -NR2R2 or cyano; Ar represents: a phenyl group optionally substituted by one or more groups which may be the same or different selected from Rl, -S(O)mRl, -ORl, a cycloalkyl group containing from 3 to 6 carbon atoms, -OR4, -OR5, -S(O)mR4, -NR2R4, -NR4CORl, -OCOR5, -S(O)raR5, -NR2R5, -NR5COR2, or a halogen atom; or a 5 or 6 membered heterocycle containing one or more heteroatoms selected from oxygen, sulphur and nitrogen in the ring, which is optionally substituted by one or more groups which may be the same or different selected from Rl, -S(O)mRl, -ORl, a cycloalkyl group containing from 3 to 6 carbon atoms, -OR4, -OR5, -S(O)mR4, -NR2R4, -NR4-CORl, -OCOR5, -S(O)mR5, -NR2R5, -NR5COR2, or a halogen atom; Rl represents a straight- or branched- chain alkyl group containing from 1 to 6 carbon atoms optionally substituted by one or more halogen atoms; R2 and R2 independently represent the hydrogen atom or a straight- or branched- chain alkyl group containing up to 4 carbon atoms optionally substituted by one or more halogen atoms; R4 represents a phenyl group optionally substituted by one or more groups selected from Rl, -S(O)mRl, -ORl, -NR2R2, a cycloalkyl group containing from 3 to 6 carbon atoms, or a halogen atom; R5 represents a 5 or 6 membered heterocycle containing one or more heteroatoms in the ring selected from oxygen, sulphur and nitrogen; m represents zero, 1 or 2; provided that ( for compounds of formula (I) only ): when X represents chlorine and Y and Z each represent hydrogen, Ar represents a group other than unsubstituted pbenyl, 3- or 4- chloro-, methyl- or methoxy-phenyl, 3-methoxy-4-methylphenyl. 2,3,4-trimethoxyphenyl or 3,4-dichlorophenyl; and when X represents hydrogen, methyl or methoxy and Y and Z represent hydrogen, Ar represents a group other than unsubstituted phenyl; and agriculturally acceptable salts thereof which possess valuable herbicidal properties.

By the term agriculturally acceptable salts is meant salts the cations or anions of which are known and accepted in the art for the formation of salts for agricultural or horticultural uses. Preferably the salts are water-soluble. Suitable acid addition salts of the compounds of general formula (I), which may incorporate an amino radical, include salts with inorganic acids, for example hydrochlorides, sulphates, phosphates and nitrates and salts with organic acids, for example acetic acid.

It is to be understood that where reference is made in the present specification to the compounds of general formula (I), such reference is intended to include also the salts with agriculturally acceptable acids of compounds of general formula (I) where appropriate.

The present invention further provides a class of compounds of formula (I) wherein: * X, Y and Z represent a halogen atom or an alkyl or haloalkyl or 20 alkoxy group, or a hydrogen atom, * Ar represents a phenyl group, optionally mono- or polysubstituted (preferably monosubstituted) by a lower alkyl or a lower alkoxy or a lower alkylthio or a phenyl group or a halogen atom, preferably chlorine or fluorine, or a heterocycle Het, * Het represents a 5 or 6-membered heterocycle containing a heteroatom such as sulphur, nitrogen or oxygen, this heterocycle being optionally mono- or polysubstituted (preferably monosubstituted) by a lower alkyl or a lower alkoxy or a lower alkylthio group or a halogen atom, preferably chlorine fluorine.

Among the compounds according to the invention, compounds having one or the other of the following characteristics are preferred: only one of the three radicals X, Y or Z represents a radical other 5 than a hydrogen atom, when X, Y or Z are halogen atoms, they represent chlorine atoms, when X, Y or Z are a hydrocarbon radical, this radical has 1 to 4 carbon atoms, most preferably 1 carbon atom.

Compounds in which Ar is monosubstituted and Het represents a thienyl radical are preferred.

Also preferred are compounds wherein Z represents Rl or a halogen atom.

Also preferred are compounds wherein Z is the hydrogen atom or a chlorine atom or a methyl group.

Also preferred are compounds wherein X is the hydrogen atom and Y is a methyl group.

The following compounds may be mentioned as specific compounds which may be prepared according to the invention (see atom numbering system at the end of the description): 1) 3-phenyl-s-triazolo-[4,3-b] pyridazine, 2) 8-methyl-3-phenyl-s-triazolo-[4,3-b] pyridazine, 3) 7-methyl-3-phenyl-s-triazolo-[4,3-b] pyridazine, 4a) 8-methyl-3-(3’-methyl-thien-2’-yl)-s-triazolo-[4,3-b] pyridazine, 4b) 7-methyl-3-(3’-methyl-thien-2’-yl)-s-triazolo[[4,3-b] pyridazine, 5a) 8-methyl-3-(thien-3’-yl)-s-triazolo-[4,3-b] pyridazine, 5b) 7-methyl-3-(thien-3’-yl)-s-triazolo-[4,3-b3 pyridazine, 6a) 8-methyl-3-(2’-fluorophenyl)-s-triazolo-[4,3-b] pyridazine, 6b) 7-methyl-3-(2’-fluorophenyl)-s-triazolo-[4,3-b] pyridazine, 7a) 8-methyl-3-(2’,4’-dimethylphenyl)-s-triazolo-[4,3-b] pyridazine, 7b) 7-methyl-3-(2’,4’-dimethyIphenyl)-s-triazolo-[4,3-b] pyridazine, 8) 8-methyl-3-(thien-2’-yl)-s-triazolo-[4,3-b] pyridazine, 9) 7-methyl-3-(thien-2’-yl)-s-triazolo-[4,3-b] pyridazine, ) 7,8-dimethyl 3-phenyl-s-triazolo-[4,3-b] pyridazine; 11) 8-methyl 3-(2’-methylphenyl)-s-triazolo-[4,3-b] pyridazine, . * 12) 8-methyl 3-(4’-methylphenyI)-s-triazolo-[4,3-b] pyridazine, 13) 8-methyl 3-(3’-methylphenyl)-s-triazolo-[4,3-b] pyridazine, 14) 8-methyl 3-(r-methylpyrrol-2’-yl)-s-triazolo-[4,3-b] pyridazine, ) 8-methyl 3-(4’-isopropoxyphenyl)-s-triazolo-[4,3-b] pyridazine, 16a) 8-methyl 3-(4’-isopropylphenyl)-s-triazolo-[4,3-b] pyridazine, 16b) 7-methyl 3-(4’-isopropylphenyl)-s-triazolo-[4,3-b] pyridazine, 17) 8-methyl 3-(4’-phenoxyphenyl)-s-triazolo-[4,3-b] pyridazine, 18) 8-methyl 3-(4’-ethylphenyl)-s-triazolo-[4,3-b] pyridazine, 19) 8-methyl 3-(4’-cyclohexylphenyl)-s-triazolo-[4,3-b] pyridazine, 20a) 8-methyl 3-(2’-bromophenyl)-s-triazolo-[4,3-b] pyridazine, 20b) 7-methyl 3-(2’-bromophenyl)-s-triazolo-[4,3-b] pyridazine, 21) 8-methyl 3-(2’-methylthiothien-3’-yl)-s- triazolo-[4,3-b] pyridazine, 22a) 8-methyl 3-(3’-phenoxyphenyl)-s-triazoIo-[4,3-b] pyridazine, 22b) 7-methyl 3-(3’-phenoxyphenyl)-s-triazolo-[4,3-b] pyridazine, 23) 8-methyl 3-[4’-(n-butoxy)phenyl]-s-triazolo-[4,3-b] pyridazine, 24) 7-methyl 3-[3’-(4''-chlorophenoxy)phenyl]-s-triazolo-[4,3-b] pyridazine, 25a) 8-methyl 3-(3’-fluoro-2’-methylphenyl)-s-triazolo-[4,3-b] pyridazine, 25b) 7-methyl 3-(3’-fIuoro-2’-methylphenyl)-s-triazolo-[4,3-b] pyridazine, 26) 7-methyl 3-(3’-trifluoromethanephenyl)-s-triazolo-[4,3-b] pyridazine, and 27) 7-methyl 3-(4’-bromophenyl)-s-triazolo-[4,3-b] pyridazine.

Compounds of general formula (I) in which X represents a halogen atom, preferably chlorine, are particularly useful as intermediates in the preparation of other compounds of general formula (I) as hereinbefore defined.

The compounds according to the invention may be prepared using various processes.

According to a feature of the present invention, compounds of formula (I), may be prepared using a compound of the arylidene-2-(pyridaz-3’yl)hydrazine type, of formula (II) as depicted at the end of the description, in which the various substituents have the meanings previously given, which is reacted with an oxidising agent according to a cyclising oxidation reaction. Metal cations derived from metals having several oxidation levels and being at a high oxidation level, such as for example lead tetraacetate or ferric chloride may be mentioned as oxidising agent; atmospheric oxygen may also be used as oxidising agent. The reaction is advantageously carried out in organic solvent liquid medium, the solvent being preferably chosen so as to dissolve the reagents and final products as much as possible. Suitable solvents are hydrocarbons, halogenated hydrocarbons, acids, alcohols; solvents of the nitrated aromatic hydrocarbon type may also be used especially in the case where the oxidising agent is atmospheric oxygen. The molar ratio of the amount of oxidising agent used relative to the compound of formula (Π) is generally between 1 and 5.

According to a first variant, the oxidation reaction for the compound of formula (II) may also be carried out by addition of a halogen (in an amount preferably close to the stoichiometric proportion), such as bromine, followed by a dehalogenation reaction. These oxidation reactions (according to the general mode or according to the variant, are generally carried out between 10 and 210°C (preferably between 10 and 50°C for the variant).

The cyclising oxidation is achieved by following up the halogenation oxidation with a dehalogenation reaction which is generally carried out in the presence of an alkaline agent, for example in the presence of a carboxylic alkali metal salt such as sodium acetate in acetic acid medium. The molar ratio of the amount of alkaline agent used relative to the halogenated compound of formula (Π) is generally between 1 and 5.

According to a second variant, the oxidation reaction for the compound of formula (II) may also be carried out by addition of an N-halogenoN-metallosulphonamidate of formula (IV): RSO2N' X M+ in which R represents an alkyl group, or preferably a phenyl group optionally monosubstituted in the para position with an alkyl group (for example a p-tolyl . * group), X represents a halogen atom (preferably chlorine or bromine) and M represents an alkali metal atom (preferably sodium). A preferred example of Nhalogeno-N-metallosulphonamidate is chloramine T of formula (IVa): H3C'/O/ S°2N' C1 Na+ (IVa) x-7 The use of an N-halogeno-N-metallosulphonamidate of the preceding formula as cyclising oxidation agent for the 2-(pyridaz-3’-yl)hydrazine arylidenes of general formula (II) is novel and thus constitutes a novel process for preparing the compounds of formula (I).

This cyclising oxidation reaction is generally carried out between and 150°C (preferably between 20 and 50°C) and is advantageously carried out in organic solvent liquid medium, preferably in alcohols.

The molar ratio of the amount of oxidising agent used relative to the compound of formula (Π) is preferably close to the stoichiometric proportion.

According to a further feature of the present invention, a second method for preparing the compounds of formula (I) comprises the dehydration of a compound of the 3-(aroylhydrazino)pyridazine type of formula (III) as depicted at the end of the description, in which the various susbtituents have the same meaning as in formula (I) (cyclising dehydration).

The cyclising dehydration reaction of the compound of formula (ΙΠ) is normally carried out by heating between 100 and 250°C, with removal of the water formed as the reaction progresses. The water formed may be removed by simple distillation or by azeotropic distillation if the heating is carried out in the presence of an aromatic solvent capable of dissolving the compound of formula (III) and of forming an azeotrope with water. Aromatic hydrocarbons, halogenated or not, as well as phenols for example xylene, phenol and 1,2,4trichlorobenzene, may be mentioned as azeotropic solvent suitable for this mode of dehydration.

But the procedure may also be carried out in other inert organic solvents such as for example dioxane.

According to a further feature of the present invention, a third process for preparing the products of formula (I) comprises the reaction of a compound of the hydrazine type of formula (V) as depicted at the end of the description with a compound of formula (VI): UpC( = W j)-Ar according to the reaction: (V) + (VI) -► (I) + UjH + W1H2 the various radicals in these formulae (V) and (VI) having the same meanings as in the formula (I) and, in addition: Wi represents an oxygen atom or an NH group, when W] represents an oxygen atom, then Uj represents a hydroxyl group [in that case, (VI) is an acid] or an alkoxy group [in that case, (VI) is an ester] or an aroyloxy group [in that case, (VI) is an acid anhydride], or a halogen atom [in that case, (VI) is an acid halide] preferably chlorine, when Wj represents an NH group, then U; represents an alkoxy or an alkylthio or an arylalkylthio group.

The preceding reaction is carried out at a temperature generally between 20 and 200°C, preferably between 50 and 180°C during a time of 1 to 24 hours. The reagents (V) and (VI) are used in molar proportions between 0.8 and 1.2 respectively, preferably equal to or close to 1. The reaction may be carried out in the presence or in the absence of solvent. Solvents leading to the formation of azeotropic mixtures may be used as solvent, as indicated hereafter in some cases. Solvents of the alcoholic type may also be used when the compound of formula (VI) is an imidate, or an aromatic solvent such as a hydrocarbon, halogenated or not, or pyridine when the compound of formula (VI) is a thioimidatd or an acid halide.

The light products of the reaction (UjH and W1H2) are advantageously removed as the reaction progresses, generally by distillation when it is water or alcohols (in that case, Uj represents a hydroxy or an alkoxy group), or by degassing or by trapping by means of a tertiary base such as triethylamine when Uj is a halogen atom, or by trapping the molecule of ammonia when W| is an NH group and U1 is an alkoxy group (in that case, the product of formula (VI) is an imidate).

The aforementioned distillation of light products may be an azeotropic distillation in the presence of halogenated or non-halogenated aromatic solvents such as pyridine or chlorobenzene compounds, in particular 1,2,4-trichlorobenzene.

The aforementioned trapping of ammonia is advantageously carried out in the presence of acids (preferably carboxylic) or their derivatives such as acid anhydrides or acid halides. These acids or their derivatives are used in molar amounts generally between 1 and 30 times the amount of product of formula (VI) used. These proportions are of the same order of magnitude (mutatis mutandis) when a base is used when Uj is a halogen atom.

According to a further feature of the present invention, a fourth process for the preparation of compounds of formula (I) in which X is a hydrogen atom comprises the hydrogenolysis of compounds of formula (I) in which X is a halogen atom (preferably chlorine) to convert the halogen atom to a hydrogen atom.

This hydrogenolysis reaction is advantageously carried out in organic solvent liquid medium, the solvent being preferably chosen so as to dissolve the reagents and final products as much as possible.

Suitable solvents are alcohols and dioxane. This hydrogenolysis 5 reaction is generally carried out between 10 and 100°C (preferably between 20 and 30°C) in the presence of an acid-trapping agent, such as triethylamine or ammonium hydroxide or collidine, and a catalyst (preferably palladium on carbon) according to a process similar to those described by R.N. CASTLE in The Chemistry of Heterocyclic Compounds, Pyridazines, edited in 1973 by Interscience/Wiley, Volume 28, pages 245-248.

According to a further feature of the present invention compounds of formula (I) in which Z represents chlorine or bromine and X and Y represent hydrogen or Rl may be prepared by the reaction of a compound of formula (IX): wherein X and Y represent hydrogen or Rl, with a halogenating agent to convert the hydroxy group to a chlorine or bromine atom. Generally phosphorus oxychloride or phosphorus oxybromide are used. The reaction may optionally be carried out in the presence of an inert solvent such as toluene or chloroform at temperatures from room temperature to the reflux temperature of the mixture.

According to a further feature of the present invention compounds of formula (I) in which Z represents fluorine and X and Y represent hydrogen or Rl may be prepared by the reaction of a compound of formula (I) in which Z represents chlorine or bromine and X and Y represent hydrogen or Rl, with a salt of formula M-F in which M represents an alkali- or alkaline earth metal.

Generally M is sodium, potassium or caesium. The reaction is generally carried out in a solvent such as sulfolane at a temperature from 50 to 200°C.

According to a further feature of the present invention compounds of formula (I) in which Z represents -OR^, -SRI, -NR^r3 Or cyano may be prepared from compounds of formula (I) in which Z represents a halogen atom by nucleophilic displacement of the halogen atom by the appropriate nucleophilic reagent,-such as M-SR^, M-OR^, H-NR2r3 or M-CN wherein M represents an alkali metal cation. The reaction is generally performed in a solvent such as dimethylformamide, dimethyl sulphoxide, an alcohol or an aqueous alcohol, at temperatures from 25 to 150°C.

According to a further feature of the present invention compounds of formula (I) in which Z represent -OR^ may be prepared by the reaction of a compound of formula (IX) with an alkylating agent such as RI2SO4 or R^-L, wherein L represents a halogen atom or an alkyl- or aryl-sulphonate, to convert the hydroxy group to a group -ORk The reaction is generally performed in an inert solvent such as tetrahydrofuran, an alcohol or an aqueous alcohol at a temperature from room temperature to 100°C. Preferably a base is present such as sodium hydroxide or triethylamine. When R1 represents a haloalkyl group, L is a halogen atom, preferably chlorine.

Salts of the compounds of formula (I) may be prepared by known methods, for example by treatment of a compound of formula (I) with the appropriate acid.

The invention also relates to novel products which are useful in particular as intermediates in the preparation of the compounds of formula (I), characterised in that they are of one of the formulae (II), (ΠΙ), (V) and (VIII) hereinafter depicted, in which the symbols X, Y, Z and Ar have the meanings indicated for the formula (I), with the proviso that: i) for compounds of formula (Π): when X represents 1-methyl-l-ethylpropyl and Y and Z each hydrogen, Ar is not 4-n-butoxyphenyl, 2,4-, 2,5- or 3,5-dimethylphenyl, 3-bromophenyl, 2,4- or 3,5-dichlorophenyl, 2-, or 4-chlorophenyl, or 2,4dimethoxyphenyl, when X, Y and Z each represent methyl, Ar is not unsubstituted phenyl, when X and Z each represent methyl and Y represents hydrogen, Ar is not phenyl unsubstitnted or substituted only by chlorine, when X represents chlorine and Y and Z each represent hydrogen, Ar is not phenyl unsubstituted or substituted only by chlorine or methoxy; ii) for compounds of formula (V), when Y and Z each represent methyl, X is not chlorine; and iii) for compounds of formula (VIII), when T represents chlorine, and Y and Z each represent methyl, X is not hydrogen or chlorine, when Y and Z each represent hydrogen, X is not methyl, butyl, trichloromethyl or halogen, when T and Y each represent chlorine, X and Z represent groups other than chlorine.

In what follows, but also in what precedes, the reactions carried out at a high temperature in a solvent, subject to specific indications to the contrary, are advantageously carried out at the boiling temperature of the solvent considered.

The preparation of arylidene-2-(pyridaz-3’-yl)hydrazines of formula (Π) is easily carried out by reacting 3-hydrazmopyridazines of formula (V) with aldehydes of formula Ar-CHO in which the symbols X, Y, Z and Ar have the meanings indicated for the formula (I). The reaction is generally carried out at a temperature between 50 and 150°C, preferably in a solvent. A lower alcohol such as methanol or ethanol is advantageously used as solvent. The reaction is enhanced by the presence of catalytic amounts of an inorganic or organic acid, for example hydrochloric, sulphuric, acetic, trichloroacetic, perchloric or p-toluenesulphonic acids. Such a reaction is described in Quarterly Review, Chemical Society, Volume 23, pages 37-56, 1969 in the article by J. BUCKINGHAM and also in Houben-Weyl, Methoden der organischen Chemie, 4th Edition, 1967, Volume X-2, pages 410-487.

The preparation of 3-(aroylhydrazino)pyridazines of formula (III) is easily carried out by reacting 3-hydrazinopyridazines of formula (V) with the compounds of formula (VII): Ar-CO-U2 in which the symbols X, Y, Z and Ar have the meanings indicated for the formula (I), and U2 has one of the meanings previously indicated for Up The reaction proceeds according to the scheme: (V) + (VII) -► (HI) + U2H The reaction is generally carried out by mixing the reagents at a temperature between 0 and 180°C in the presence or in the absence of solvent. A polar solvent is advantageously used as solvent.

As solvents which may be more particularly used, there may be mentioned alcohols, when Ar-CO-U2 is not an acid halide; ethers or chlorinated or non-chlorinated aliphatic hydrocarbons such as methylene chloride and chloroform; solvents with acid-trapping properties such as pyridine may also be used when Ar-CO-U2 represents an acid halide.

The proportion of the two reagents [that of formula (V) and that of formula (VII)] may vary within wide limits around the stoichiometric proportion. When Ar-CO-U2 is an acid (U2 is an OH group) an excess of the latter derivative is used relative to the compound of formula (V), for example 2 to 8 25 moles per mole of (V). When Ar-CO-U2 is an ester (U2 is an alkoxy group), an amount, close to the stoichiometric proportion, of this latter derivative is used relative to the compound of formula (V), for example 0.8 to 1.1 moles per mole of (V). When Ar-CO-U2 is an acid halide (U2 is a halogen atom), an excess of the compound of formula (V) is used relative to the compound of formula (VII), for example 1 to 5 moles per mole of Ar-CO-U2.

Processes which make it possible to obtain the compounds of formula (III) according to the preceding description are described in the manual by PATAI, The Chemistry of Carboxylic Acids and Esters, Volume 5, Chapter 9, pages 425-428, edited in 1969 by Interscience/Wiley in the article by . A SATCHELL and also in Houben-Weyl, Methoden der organischen Chemie, 1952, Volume VIII, Chapter 5, pages 676-680.

The preparation of 3-(aroylhydrazino)pyridazines of formula (III) may also be easily carried out by reacting a pyridazine derivative of formula (VIII) with an arylhydrazide of formula Ar-CO-NH-NH2 in which the symbols X, Y, Z and Ar have the meanings already indicated for the formulae (I) and (III) and T is a halogen atom, preferably chlorine or bromine. The reaction proceeds according to the scheme: (VIII) + ArCONHNH2 -► (HI) + HT This reaction is advantageously carried out at a temperature between 50 and 150°C in solvents such as alcohols or aromatic solvents, for example pyridine or hydrocarbons such as toluene. The proportion of reagents is advantageously close to the stoichiometric proportion, for example between a molar ratio ranging from 0.8 to 1.2. The reaction may be enhanced by the presence of an amount, also close to the stoichiometric proportion, of a basic agent such as an alcoholate or an alkali metal bicarbonate.

The arylhydrazides of formula Ar-CO-NH-NH2 may be obtained by reacting a hydrazine hydrate with an acid or one of its derivatives such as esters, halides or anhydrides. The reaction is advantageously carried out at a temperature between 0 and 150°C, preferably in the presence of a solvent such as a lower alcohol, the molar proportion of hydrazine hydrate relative to the other reagent generally being between 1.01 and 1.5.

Processes which make it possible to obtain the arylhydrazides according to the preceding description are described in the manual by PATAI, The Chemistry of Amides, Volume 11, Chapter 10, pages 515-600, edited in 1970 by Interscience/Wiley in an article by PAULSEN and STOYE, and also in Organic Reactions, the CURTIUS reaction, 1962, Volume III, Chapter 9, pages 366-369 edited by Wiley.

The S-Iiydrazinopyridazmes of formula (V) may in particular be prepared by a process similar to those described by R.N. CASTLE in The Chemistry of Heterocyclic Compounds, Pyridazines, edited in 1973 by Interscience/Wiley, Volume 28, pages 254-256.

The 3-halogenopyridazines of formula (VIII) may for their part be prepared by a process similar to those described by R.N. CASTLE, in the same manual, pages 221-242.

Compounds of formula (IX) may be prepared by the reaction of compound of formula (X): ,N H2N (X) Ar with a compound of formula (XI) or (ΧΠ): co2r7 X· X or8 X OR8 Y C°2r7 X^O (XI) (ΧΠ) in which X represents hydrogen or Rl and R^ and R8 represent an alkyl group. The reaction is generally performed at a temperature from 100 to 200°C, optionally in the presence of a solvent such as acetic acid. This reaction is described in the literature (J.Am. Chem. Soc. £1, 6289 (1959).

Compounds of formula (V) in which X represents hydrogen may be prepared from the corresponding compound of formula (V) in which X represents halogen by reaction with hydrazine hydrate in the presence of palladium on charcoal catalyst. The reaction generally performed in the presence of a solvent such as methanol at a temperature from 25°C to the reflux temperature of th6 mixture.

Compounds of formula (V) in which Z represents -ORl and X and Y represent hydrogen may be prepared by the reaction of a compound of formula (XIII): with hydrazine hydrate. The reaction is optionally performed in the presence of 15 a solvent e.g. ethanol, at a temperature from 25 to 100°C.

Compounds of formula (ΧΠΙ) may be prepared by the reaction of a compound of formula (XIV): Cl Cl (XIV) with a compound of formula RlO-Na in the presence of an inert solvent at a temperature from 25 to 150°C.

Compounds of formula (IX) may be prepared by the reaction compounds of formula (XV): OH (XV) with a compound of formula (VI) as hereinbefore defined. The reaction is performed as hereinbefore described for the preparation of a compound of formula (I) from compounds of formula (V) and (VI).

Compounds of formula (XV) may be prepared by the reaction of a compound of formula (XVI): with hydrazine hydrate. The reaction is optionally performed in the presence of a solvent such as ethanol at a temperature from 25°C to the reflux temperature of the mixture.

The following examples, given without implying any limitation, illustrate the invention and show how it may be implemented.

Examples 1 to 9 illustrate the preparation of herbicidal compounds according to the invention. Examples 1-1 to 1-13 illustrate the preparation of intermediate compounds of the preceding products.

* Example 1: 6-Chloro-3-phenyl-s-triazolo-[4,3-b] pyridazine (0.75 g, 0.0033 mole) (prepared as in Example 1-1), 10 % palladium on carbon (0.085 g) and 28 % ammonium hydroxide (3 ml) in methanol (60 ml) are stirred for 4 hours at room temperature under a hydrogen atmosphere of 3 bars. After filtering, the residue is chromatographed (eluent heptane/ethyl acetate 50/50). 3-PhenyI-sIE 913706 triazolo-[4,3-b] pyridazine (0.35 g, 0.0018 mole) is obtained; m.p. = 145°C (yield 55 %).

* Example 2: Example 1 is repeated replacing 6-chloro-3-phenyl-s-triazolo-[4,35 b] pyridazine (0.75 g) by 6-chloro-8-methyl-3-phenyl-s-triazolo-[4,3-b] pyridazine (1 g, 0.0041 mole) (prepared as in Example 1-2), the procedure being carried out under a hydrogen atmosphere of 3.15 bars for 6 hours. 8-Methyl-3-phenyl-striazolo-[4,3-b] pyridazine (0.59 g, 0.0028 mole) is obtained; m.p. = 51°C (yield 70 %).

* Example 3: Example 1 is repeated replacing 6-chloro-3-phenyl-s-triazolo-[4,3b] pyridazine (0.75 g) by 6-chloro-7-methyl-3-phenyl-s-triazolo-[4,3-b] pyridazine (0.7 g, 0.0029 mole) (prepared as in Example 1-2), the procedure being carried out under a hydrogen atmosphere of 2.5 bars for 3 hours 30 minutes. 7-Methyl-315 phenyl-s-triazolo-(4,3-b] pyridazine (0.47 g, 0.0022 mole) is obtained; m.p. = 180°C (yield 76 %).

* Example 4: Compounds 4a, 4b, 10,11,12,13,14, 16a, 16b, 17, 18, 20a, 20b, 21, 22a, 22b, 24, 25a, 25b, 27.

Chloramine T (2.12 g, 0.0075 mole) is rapidly added at room temperature to an ethanolic solution (50 ml) of a mixture of 3-methyl-2thiophenecarboxaldehyde-(4’/5’-methylpyridaz-3’-yl)hydrazones (1.75 g, 0.0075 mole, prepared as in Example 1-3). The reaction mixture is stirred for 10 minutes. After evaporating the solvent, the residue is chromatographed (eluent heptane/ethyl acetate 20/80). 8-Methyl-3-(3’-methylthien-2’-yl)-s-triazolo-[4,3-b] pyridazine (4a) (0.49 g, 0.0021 mole), m.p. = 170°C and 7-methyl-3-(3’methylthien-2’-yl)-s-triazolo-(4,3-b] pyridazine (4b) (0.75 g, 0.0033 mole), m.p. = 191°C, are obtained (yield 71 %).

By proceeding in a similar manner the following compounds of general formula (I) were prepared from the appropriately substituted starting materials: Compound No. Z Y X Ar m.p. 10 Me Me H Phenyl 170°C 11 Me H H 2-Methylphenyl 133°C 12 Me H H 4-Methylphenyl 170°C 13 Me H H 3-Methylphenyl 117°C 14 Me H H l-MethyIpyrrol-2-yI 182°C 16a Me H H 4-Isopropylphenyl 105°C 16b H Me H 4-Isopropylphenyl 121°C 17 Me H H 4-Phenoxyphenyl 156°C 18 Me H H 4-Ethylphenyl 115°C 20a Me H H 2-Bromophenyl 188°C 20b H Me H 2-Bromophenyl 196°C 21 Me H H 2-Methylthiothien-3-yl 135°C 22a Me H H 3-Phenoxyphenyl 102°C 22b H Me H 3-Phenoxyphenyl 133°C 24 H Me H 3-(4’-Chlorophenoxy)phenyl 165°C 25a Me H H 3-Fluoro-2-methylphenyl 195°C 25b H Me H 3-Fluoro-2-methylphenyl 201°C 27 H Me H 4-Bromophenyl 238°C * Example 5: Example 4 is repeated replacing 3-methyl-2- thiophenecarboxaldehyde-(4’/5’-methylpyridaz-3’-yl)hydrazones (1.75 g) by a mixture of 3-thiophenecarboxaldehyde-(4’/5’-methylpyridaz-3’-yl)hydrazones (2.2 g, 0.01 mole) (prepared as in Example 1-4). Chloramine T (2.82 g, 0.01 mole) is used in this case. After chromatography (eluent ethyl acetate), 8-methyl-3-(thienIE 913706 3’-yl)-s-triazolo-[4,3-b] pyridazine (5a) (0.65 g, 0.003 mole), m.p. = 156°C and 7methyl-3-(thien-3’-yl)-s-triazolo-[4,3-b] pyridazine (5b) (0.78 g, 0.0036 mole), m.p. = 151°C, are obtained (yield 66 %).

* Example 6: Compounds 6a, 6b, 15, 19, 23, 26.

A mixture of 3-hydrazino-4/5-methylpyridazines (1.25 g, 0.01 mole) (prepared as in Example 1-5), and 2-fluorobenzoyl chloride (1.59 g, 0.01 mole) in toluene (50 ml) is heated for 2 hours in a round-bottomed flask mounted with a condenser and equipped with a Dean Stark separator. After evaporating the solvent and chromatographing the residue (eluent ethyl acetate), 8-methyl-3-(2’fluorophenyl)-s-triazolo-[4,3-b] pyridazine (6a) (0.26 g, 0.0011 mole), m.p. = 126°C and 7-methyl-3-(2’-fluorophenyl)-5-triazolo-[4,3-b] pyridazine (6b) (0.10 g, 0.00043 mole), m.p. = 182°C are obtained (yield 15 %).

By replacing toluene with 1,4-dioxane and without the use of a Dean Stark separator the following compounds of general formula (I) were prepared from the appropriately substituted starting materials: Compound No. Z Y X At m.p. 15 Me H H 4-Isoproxyphenyl 155°C 19 Me H H 4-Cyclohexylphe nyl 226°C 23 Me H H 4-(nButoxy)phenyl 144°C 26 H Me H 3-TrifluoromethyIphenyl 147°C * Example 7: Example 4 is repeated replacing 3-methyl-2thiophenecarboxaldehyde-(4’/5’-niethylpyridaz-3’-yl)hydrazones (1.75 g) by a mixture of 2,4-dimethylbenzaldehyde-(475’-methylpyridaz-3’-yl)hydrazones (2.10g, 0.0088 mole) (prepared as in Example 1-6). Chloramine T (2.45 g, 0.0087 mole) is used in this case. After chromatography (eluent heptane/ethyl acetate 20/80), 8-methyl-3-(2’,4’-dimethylphenyl)-s-triazolo-[4,3-b] pyridazine (7a) (0.51 g, 0.0021 mole), m.p. = 156°C and 7-methyl-3-(2’,4’-dimethylphenyl)-s-triazolo5 [4,3-b] pyridazine (7b) (0.95 g, 0.004 mole), m.p. = 144°C, are obtained (yield 71 A %).

* Example 8: Example 4 is repeated replacing 3-methyl-2thiophenecarboxaldehyde-(4’/5’-methylpyridaz-3’-yl)hydrazones (1.75 g) by 210 thiophenecarboxaldehyde-(4’-methylpyridaz-3’-yl)hydrazone (1.4 g, 0.0064 mole) (prepared as in Example 1-7). Chloramine T (1.80 g, 0.0064 mole) is used in this case. After chromatography (eluent ethyl acetate), 8-methyl-3-(thien-2’-yl)-striazolo-[4,3-b] pyridazine (0.28 g, 0.0013 mole), m.p. = 173°C is obtained (yield 20 %).

* Example 9: Example 4 is repeated replacing 3-methyl-2thiophenecarboxaldehyde-(4’/5’-methylpyridaz-3’-yl)hydrazones (1.75 g) by 2thiophenecarboxaldehyde-(5’-methylpyridaz-3’-yl)hydrazone (1.70 g, 0.0078 mole) (prepared as in Example 1-7). Chloramine T (2.20 g, 0.0078 mole) is used in this case. After chromatography (eluent ethyl acetate) 7-methyl-3-(thien-2’-yl)s-triazolo-[4,3-b] pyridazine (1.10 g, 0.0051 mole), m.p. = 198°C is obtained (yield 65 %).

* Example 1-1: Example 6 is repeated replacing: - 3-hydrazino-4/5-methylpyridazines (1.25 g) by 3-chloro-6hydrazinopyridazine (5.0 g, 0.035 mole) (prepared as in Example 1-8), and - 2-fluorobenzoyl chloride (1.59 g) by benzoyl chloride (5.5 g, 0.039 mole). After chromatography (eluent heptane/ethyl acetate 30/70), 6-chloro-3phenyl-s-triazolo-[4,3-b] pyridazine (5.7 g, 0.025 mole), m.p. = 95°C, is obtained (yield 71 %).

* Example 1-2: Example 6 is repeated replacing: - 3-hydrazino-4/5-methylpyridazines (1.25 g) by a mixture of 35 chloro-6-hydrazino-4/5-methylpyridazines (0.75 g, 0.0047 mole) (prepared as in Example 1-9), and - 2-flu0robenzoyl chloride (1.59 g) by benzoyl chloride (0.66 g, 0.0047 mole).

After chromatography (eluent ethyl acetate), 6-chloro-8-methyl-310 phenyl-s-triazolo-[4,3-b] pyridazine (0.64 g, 0.0026 mole), m.p. = 184°C and 6chloro-7-methyl-3-phenyl-s-triazolo-[4,3-b] pyridazine (0.07 g, 0.0003 mole), m.p. = 170°C are obtained (yield 61 %).

* Example 1-3: A mixture of 2-formyl-3-methylthiophene (1.27 g, 0.01 mole) and 3 15 hydrazino-4/5-methylpyridazmes (1.25 g, 0.01 mole) (prepared as in Example I5) in ethanol (20 ml) containing a few drops of concentrated hydrochloric acid is heated at boiling temperature for 2 hours. The reaction mixture is then concentrated and washed with diiospropyl ether. The mixture of 3-methyl-2thiophenecarboxaidehyde-(4’/5’-methylpyridaz-3’-yl)hydrazones (2.07 g, 0.009 mole) obtained is used in the crude state without further purification (yield 89%).

By proceeding in a similar manner the following compounds were prepared from the appropriately substituted starting materials. z Y X Ar Me Me H Phenyl Me/H H/Me H 2-Methylphenyi Me/H H/Me H 4-Methylphenyl Me/H H/Me H 3-Methylphenyl Me/H H/Me H l-MethyIpyrrol-2-yl Me/H H/Me H 4-Isopropylphenyl Me/H H/Me H 4-Phenoxyphenyl Me/H H/Me H 4-Ethyl phenyl Me/H H/Me H 2-Bromophenyl Me/H H/Me H 3-Phenoxyphenyl Me/H H/Me H 3-(4’-Chlorophenoxy)phenyl Me/H H/Me H 3-Fluoro-2-methylphenyl Me/H H/Me H 4-Bromophenyl By replacing 2-formylthiophene by 3-formyl-2-methylthio thiophene ethylene acetal, the above reaction conditions are applied.

After 4 hours under reflux the reaction mixture is cooled whereupon a solid precipitates. After filtration and chromatography of the solid 5 (eluent 60:80 petrol/ether/acetonitrile/ethylacetate), 2-methylthio-3-thiophene(5’-methylpyridaz-3’-yl) hydrazone is obtained, m.p. 198°C. After concentration of the filtrate and chromatography (eluent 60:80 petrol/ether/acetonitrile/ethylacetate) 2-methylthio-3-thiophene-(4’methylpyridaz-3’-yl)hydrazone, m.p. 168°C is obtained (Yield 60%).

* Example 1-4: Example 1-3 is repeated replacing 2-formyl-3-methylthiophene by 3-formylthiophene (1.35 g, 0.0121 mole). The mixture of 3-hydrazino-4/5methylpyridazines (1.50 g, 0.0121 mole) is used in this case. A mixture of 3thiopbenecarboxaldehyde-(4’/5’-methylpyridaz-3’-yl)hydrazones (2.44 g, 0.0112 mole) is obtained and used without further purification (yield 93 %).

* Example 1-5; A mixture of 3-chloro-6-hydrazino-4/5-methylpyridazines (9.65 g, 0.061 mole) (prepared as in Example 1-9), 10 % palladium on carbon (1.8 g) and 98 % hydrazine hydrate (40 ml) in methanol (300 ml) are heated at the reflux temperature of the solvent for 1 hour 30 minutes. The hot mixture is filtered on Hyflo-supercel and concentrated. A mixture of 3-hydrazino-4/5methylpyridazines (4.8 g, 0.039 mole) is obtained which is crystallised in toluene and used without further purification (yield 64 %). 3-Hydrazino-4,5-dimethylpyridazine was similarly prepared from 3chloro-6-hydrazino-4,5-dimethylpyridazine.

* Example 1-6: Example 1-3 is repeated replacing: - 2-formyl-3-methylthiophene (1.27 g) by 2,4-dimethylbenzaldehyde (1.62 g, 0.0121 mole), and - 3-hydrazino-4/5-methylpyridazines (1.25 g) by the same mixture (1.5 g, 0.0121 mole).

A mixture of 2,4-dimethylbenzaldehyde-(4’/5’-methylpyridaz-3’yl)hydrazones (2.35 g, 0.0098 mole) obtained is used in the crude state without further purification (yield 81 %).

* Example 1-7: Example 1-3 is repeated replacing: - 2-formyl-3-methylthiophene (1.27 g) by 2-formylthiophene (1.9 g, 0.017 mole), and - 3-hydrazino-4/5-methylpyridazines (1.25 g) by the same mixture (2.1 g, 0.017 mole).

After 1 hour at the reflux temperature of the solvent and then cooling, 2-thiophenecarboxaldehyde-(5’-methylpyridaz-3’-yl)hydrazone (1.8 g, 0.0082 mole) is obtained by filtration. Evaporation of the filtrate makes it possible to isolate, after washing with diisopropyl ether, 225 thiophenecarboxaldehyde-(4’-methylpyridaz-3’-yl)hydrazone (1.4 g, 0.0064 mole). These 2 intermediates are used in the crude state without further purification (yield 86 %).

* Example 1-8: 3-Chloro-6-hydrazinopyridazine is prepared according to a . A procedure described in the literature: Carlo FARINA, Riccardo MONGUZZI and Marino PINZA, Organic Preparations and Procedures Int., 21 (1), 125-128 (1989).

* Example 1-9: 3-Chloro-6-hydrazino-4/5-methylpyridazines are obtained according to: Soeren LINHOLTER and Regitze ROSENOERN, Acta Chem. Scand., 16, 2389-2394 (1962).

*Example I-10 3-Chloro-6-hydrazino-4,5-dimethyl pyridazine is obtained according to: M. JAPELJ, B. STANOVNIK and M. TISLER, Monatsch Chem., JLOO, 671, (1969).

*Example 1-11 Benzoyl chlorides used to prepare compounds 19 and 23 were prepared by heating the appropriately substituted benzoic acids at reflux with thionyl chloride for 3 hours. The excess thionyl chloride was removed by evaporation and the benzoyl chlorides were used directly without further purification.

♦Example 1-12 A mixture of 3-formyl thiophene (50.5g, 0.45 mole), ethylene glycol (25.2ml, 0.45 mole) in toluene containing a catalytic amount of p-toluene sulphonic acid was heated under reflux for 3 hours 30 minutes. After evaporating the solvent the resulting oil is distilled and 3-formyl thiophene ethylene acetal, b.p. 72-74°C/l mm Hg is obtained (yield 55%).

♦Example 1-13 n-Butyl lithium (2.5m in hexane, 36ml) is added under inert 5 atmosphere to a stirred, cooled solution of 3-formyl thiophene ethylene acetal (13.0g, 0.083.2 mole) in ether whilst maintaining the temperature below -70°C. The mixture is stirred at -70°C for 1 hour and then allowed to warm to room temperature for a further 30 minutes.

The mixture is recooled to approximately -78°C and a solution of methyl disulphide (9.0ml, 0.1 mole) in ether is added over 5 minutes. The mixture is stirred at -78°C for 40 minutes, then allowed to warm to room temperature for 16 hours.

The mixture is poured into ice/water and extracted with methylene chloride. The combined organic layers are dried (anydrous sodium sulphate), filtered and evaporated to give a clear yellow oil. After distillation 3-formyl-2methylthiothiophene ethylene acetal b.p. 130-132°C/l-4 mm Hg is obtained (Yield 77%).

According to a feature of the present invention, there is provided a method for controlling the growth of weeds (i.e. undesired vegetation) at a locus which comprises applying to the locus a herbicidally effective amount of at least one triazolopyridazine derivative of general formula (I) or an agriculturally acceptable salt thereof. For this purpose, the triazolopyridazine derivatives are normally used in the form of herbicidal compositions (i.e. in association with compatible diluents or carriers and/or surface active agents suitable for use in herbicidal compositions), for example as hereinafter described.

The present invention also relates to a process for weed control (in particular in zones of dicotyledonous or monocotyledonous crops) which comprises applying to the zone which has to be weeded, and/or to the plants which have to be destroyed, an effective amount of a compound according to the invention, in particular a compound of formula (I), it being possible for the plants themselves (or weeds) which have to be destroyed or whose growth is to be prevented to be of the monocotyledonous or dicotyledonous type.

The products and compositions according to the invention are easily applied to the vegetation and in particular to the weeds to be eliminated when the latter have a green foliage (post-emergence application).

The compounds of general formula (I) show herbicidal activity against dicotyledonous (i.e. broad-leafed) and monocotyledonous (e.g. grass) weeds by pre- and/or post-emergence application.

By the term pre-emergence application is meant application to the soil in which the weed seeds or seedlings are present before emergence of the weeds above the surface of the soil. By the term post-emergence application is meant application to the aerial or exposed portions of the weeds which have emerged above the surface of the soil. For example, the compounds of general formula (I) may be used to control the growth of: broad-leafed weeds, for example, Abutilon theophrasti, Amaranthus retroflexus, Bidens pilosa, Chenopodium album, Chrysanthemum segetum, Galium aparine, Ipomoea spp. e.g. Ipomoea purpurea, Polygonum convolvulus, Sesbania exaltata, Sinapis arvensis, Sinapsis alba, Solanum nigrum, Stelloria media and Xanthium strumarium, and grass weeds, for example Alopecurus myosuroides, Avena fatua, Digitaria sanguinalis, Echinochloa crus-galli, Eleusine indica and Setaria spp, e.g Setaria faberii or Setaria viridis, and sedges, for example, Cyperus esculentus.

The amounts of compounds of general formula (I) applied vary with the nature of the weeds, the compositions used, the time of application, the climatic and edaphic conditions and (when used to control the growth of weeds in cropgrowing areas) the nature of the crops. When applied to a crop-growing area, the rate of application should be sufficient to control the growth of weeds without causing substantial permanent damage to the crop. In general, taking these factors into account, application rates between 0.01kg and 20kg of active material per hectare give good results, preferably between 0.5kg and 8.0kg of active material per hectare, most preferably between 0.4 and 4 kg/ha. However, it is to be understood that higher or lower application rates may be used, depending upon the particular problem of weed control encountered.

The compounds of general formula (I) may be used to control selectively the growth of weeds, for example to control the growth of those species hereinbefore mentioned, by pre- or post-emergence application in a directional or non-directional fashion, e.g. by directional or non-directional spraying, to a locus of weed infestation which is an area used, or to be used, for growing crops, for example cereals, e.g. wheat, barley, oats, maize and rice, soya beans, field and dwarf beans, peas, lucerne, cotton, peanuts, flax, onions, carrots, cabbage, oilseed rape, sunflower, sugar beet, and permanent or sown grassland before or after planting of the crop or before or after emergence of the crop. For the selective control of weeds at a locus of weed infestation which is an area used, or to be used, for growing of crops, e.g. the crops hereinbefore mentioned, application rates between 0.01kg and 8.0kg, and preferably between 0.01kg and 4.0kg, of active material per hectare are particularly suitable.

The compounds of general formula (I) may also be used to control the growth of weeds, especially those indicated above, by pre- or post-emergence application in established orchards and other tree-growing areas, for example forests, woods and parks, and plantations, e.g. sugar cane, oil palm and rubber plantations. For this purpose they may be applied in a directional or non25 directional fashion (e.g. by directional or non-directional spraying) to the weeds or to the soil in which they are expected to appear, before or after planting of the trees or plantations at application rates between 0.25kg and 10.0kg.

The compounds of general formula (I) may also be used to control the growth of weeds, especially those indicated above, at loci which are not cropIE 913706 growing areas but in which the control of weeds is nevertheless desirable.

Examples of such non-crop-growing areas include airfields, industrial sites, railways, roadside verges, the verges of rivers, irrigation and other waterways, scrublands and fallow or uncultivated land, in particular where it is desired to control the growth of weeds in order to reduce fire risks. When used for such purposes in which a total herbicidal effect is frequently desired, the active compounds are normally applied at dosage rates higher than those used in crop-growing areas as hereinbefore described. The precise dosage will depend upon the nature of the vegetation treated and the effect sought.

Pre- or post-emergence application, and preferably pre-emergence application, in a directional or non-directional fashion (e.g. by directional or nondirectional spraying) at application rates between 1.0kg and 20.0kg, and preferably between 5.0 and 10.0kg, of active material per hectare are particularly suitable for this purpose.

When used to control the growth of weeds by pre-emergence application, the compounds of general formula (I) may be incorporated into the soil in which the weeds are expected to emerge. It will be appreciated that when the compounds of general formula (I) are used to control the growth of weeds by post-emergence application, i.e. by application to the aerial or exposed portions of emerged weeds, the compounds of general formula (I) will also normally come into contact with the soil and may also then exercise a pre-emergence control on later-germinating weeds in the soil.

Representative compounds of general formula (I) have been used in herbicidal applications or use according to the following procedures.

The examples below, given without implying any limitation, illustrate the use of the products according to the invention and their application to weed control.

The following abbreviations are used in these examples: Abbreviations English name of weed Latin name AVE wild oat Avena fatua ECH barnyard grass Echinochloa crus-galli DIG finger grass Digitaria sanguinalis SIN mustard Sinapis alba ALO black grass Alopecurus myosuroides ABU abutilon Abutilon theophrasti SOL black nightshade Solanum nigrum STE chickweed Stellaria media SES sesbania Sesbania exaltata CHY com marigold Chrysanthemum segetum Abbreviations English name Latin name of crops TRZ wheat Triticum aestivum ZEA maize Zea mays ORY rice Oryza sativa GLX soybean Glycine maximum HEL sunflower Helianthus annuus BRS colza Brassica napus Example Ul: Pre-emergence herbicide treatment of plant species.

A number of seeds, determined as a function of the plant species 5 and seed size, are sown in 7 x 7 x 8 cm pots filled with light agricultural soil.

The pots are treated by spraying with herbicidal mixture in an amount corresponding to an applied volume dose of 5001/ha and containing the active material in the desired concentration.

The treatment with the mixture is therefore carried out on the 10 seeds not covered with soil (the term mixture is used in general to designate the water-diluted compositions as applied on the plants).

The mixture used for the treatment is a solution or suspension of the active material in an acetone/water mixture in proportions of 50/50, in the presence of 0.05 % by weight of Cemulsol NP 10 (a surface-active agent consisting of a polycondensate of ethylene oxide with an alkylphenol, in particular of a polycondensate of ethylene oxide with nonylphenol) and 0.04 % by weight of Tween 20 (surface-active agent consisting of an oleate ester of a polycondensate of ethylene oxide with a sorbitol derivative).

In the case of a suspension, the latter is obtained by mixing and grinding the ingredients in a microniser so as to obtain a mean particle size lower than 40 microns.

After treatment, the seeds are covered with a layer of soil about 3 mm thick.

The pots are then placed in tanks intended to receive the water for watering, under subirrigation, and maintained for 24 days at room temperature under 60 % relative humidity.

The compounds used to treat the plants were tested on the following weed species: AVE, ECH, ALO, DIG, SIN, ABU, SOL, STE and CHY, and on the following crop species: ORY, BRS, GLX, HEL and ZEA.

After 24 days, visual assessment of crop damage was made, with the results expressed as the percentage reduction in growth or damage to the crops or weed in comparison with the plants in the control pots.

Example U2: Post-emergence herbicide treatment of plant species.

A number of seeds, determined as a function of plant species and seed size, are sown in 7 x 7 x 8 cm pots filled with light agricultural soil. The seeds are then covered with a layer of soil about 3 mm thick and the seed is allowed to germinate until it gives rise to a small plant at the appropriate stage. The treatment stage for the grasses is the second leaf in formation stage. The treatment stage for the dicotyledons is the spreading cotyledons, first real leaf in development stage.

The pots are then treated by spraying with herbicidal mixture in an amount corresponding to an applied volume dose of 5001/ha and containing the active material in the desired concentration. The mixture used for the treatment is prepared as in Example Ul. After treatment, the seeds are covered with a layer of soil about 3mm thick.

The pots are then placed in tanks intended to receive the water for watering, under subirrigation, and maintained for 24 days at room temperature under 60 % relative humidity. Assessment of phytotoxicity was carried out as in Example Ul.The compounds used to treat the plants were tested on the following weed species: AVE, ECH, ALO, DIG, SIN, ABU, SOL, STE and CHY, and on the following crop species: ORY, TRZ and ZEA.

Example U3: Pre-emergence herbicide treatment of plant species.

Appropriate quantities of the compounds used to treat the plants were dissolved in acetone to give solutions equivalent to application rates of up to 4000g test compound per hectare (g/ha). These solutions were applied from a standard laboratory herbicide sprayer delivering the equivalent of 290 litres of spray fluid per hectare.The seeds were sown in 70 mm square, 75 mm deep plastic pots in non-sterile soil. The quantities of seed per pot were as follows:Weed species . A 1) Broad-leafed weeds Abutilon theophrasti Amaranthus retroflexus Galium aparine Ipomoea purpurea Sinapis arvensis Xanthium strumarium 2) Grass weeds Alopecurus myosuroides Avena fatua Echinochloa crus-galli Setaria viridis 3) Sedges Cyperus esculentus Approx number of seeds/pot 2. . 3.

.Crop 1) Broad-leafed Cotton Soya 2) Grass Maize Rice Wheat 3. 6.

The compounds of the invention were applied to the soil surface, containing the seeds. A single pot of each crop and each weed was allocated to each treatment, with unsprayed controls and controls sprayed with acetone alone.

After treatment the pots were placed on capillary matting kept in a glass 5 house, and watered overhead . Visual assessment of crop damage was made 2024 days after spraying. The results were expressed as the percentage reduction in growth or damage to the crop or weeds, in comparison with the plants in the control pots.

Example U4: Pre-emergence herbicide treatment of plant species The weeds and crops were sown directly into John Innes potting compost in 75 mm deep, 70 mm square pots except for Amaranthus which was pricked out at the seedling stage and transferred to the pots one week before spraying. The plants were then grown in the greenhouse until ready for spraying with the compounds used to treat the plants. The number of plants per pot were as follows :1) Broad leafed weeds Weed species Number of plants per pot Growth sta Abutilon theophrasti 3 1-2 leaves Amaranthus retroflexus 4 1-2 leaves Galium aparine 3 1st whorl Ipomoea purpurea 3 1-2 leaves 25 Sinapis arvensis 4 2 leaves Xanthium strumarium 1 2-3 leaves. 2) Grass weeds Weed species Number of plants per pot Growth stage Alopecurus myosuroides 8-12 1-2 leaves Avena fatua 12-18 1-2 leaves 5 Echinochloa crus-galli 4 2-3 leaves Setaria viridis 15-25 1-2 leaves. 3) Sedges Weed SDecies Number of plants per pot Growth stage 10 Cyperus esculentus 3 3 leaves. 1) Broad leafed Crops Number of plants per pot Growth staee 15 Cotton 2 1 leaf Soya 2 2 leaves. 2) .Grass Crops Number of plants per pot Growth stage 20 Maize 2 2-3 leaves Rice 4 2-3 leaves Wheat 5 2-3 leaves.

The mixture used for the treatment is prepared as in Example Ul. and the assessment of phytotoxicity was carried out as in Example Ul. A single pot of each crop and weed species was allocated to each treatment, with unsprayed controls and controls sprayed with acetone alone.

After treatment the pots were placed on capillary matting in a glass house, and watered overhead once after 24 hours and then by controlled sub-irrigation. Visual assessment of crop damage and weed control was made -24 days after spraying. The results were expressed as the percentage reduction in growth or damage to the crop or weeds, in comparison with the plants in the control pots.

Representative compounds of the invention, when used at 4kg/ha or less, have shown an excellent level of herbicidal activity together with crop .« tolerance on the weeds used in the foregoing experiments.

When applied at 4 kg/ha according the method described in Example Ul, compounds 1, 2, 3, 4a, 5a, 6a, 7a, 8, 10, 11, 12, 13 and 14 gave at least 90% reduction in the growth of one or more weed species.

When applied at 4 kg/ha according the method described in Example U2, compounds 1,2,3,4a, 5a, 6a, 7a, 8,10, 11, 12, 13 and 14 gave at least 90% reduction in the growth of one or more weed species.

When applied at 2 kg/ha according the method described in Example U3, compounds 15,16a, 16b, 17,18,19,20a 21,22a 23,24,25b and 27 and gave at least 90% reduction in the growth of one or more weed species with selectivity in at least one , crop species.

When applied at 2 kg/ha according the method described in Example U4, compounds 18, 19,20a, 20b, 22b, 24, 25a, 26, and gave at least 90% reduction in the growth of one or more weed species with selectivity in at least one crop species.

For their practical use, the compounds of general formula (I) are rarely used alone. Most often, these compounds are part of compositions. These compositions, which may be used as herbicidal agents, contain as active material a compound of general formula (I) as previously described or an agriculturally acceptable salt thereof, mixed with at least one agriculturally acceptable solid or liquid carrier and, optionally, at least one surface-active agent, also agriculturally acceptable. Surface-active agent in the present account is understood as meaning an agent known in the English language by the name surfactant, which mainly covers surface-active, wetting or dispersing agents.

These compositions are also part of the invention. They may also contain ail sorts of other ingredients such as for example protective colloids, adhesives, thickeners, thixotropic agents, penetrating agents, stabilisers, sequestrants and the like. More generally, the compounds used in the invention may be combined with all the solid or liquid additives corresponding to the usual methods of formulation preparation.

Generally, the compositions according to the invention usually contain about 0.05 to 95 % (by weight) of a composition according to the invention, one or more solid or liquid carriers and, optionally, one or more surface-active agents.

The term carrier in the present account designates an organic or inorganic material, natural or synthetic, with which the compound is combined in order to facilitate its application to the plant, to seeds or to the soil. This carrier is therefore generally inert and should be agriculturally acceptable, in particular on the treated plant.

The carrier may be of any common type. In particular, it may be solid (clays, natural or synthetic silicates, silica, resins, waxes, solid manures and the like) or liquid (water, alcohols, in particular butanol and the like).

The surface-active agent or surfactant may also be of any common type. It may be an emulsifying, dispersing or wetting agent of the ionic or nonionic type or a mixture of such surface-active agents. There may be mentioned for example polyacrylic acid salts, lignosulphonic acid salts, phenolsulphonic or naphthalenesulphonic acids, polycondensates of ethylene oxide with fatty alcohols or with fatty acids or with fatty amines, substituted phenols (in particular alkylphenols or arylphenols), salts of sulphosuccinic acid esters, taurine derivatives (in particular alkyltaurates), phosphoric esters of polycondensates of ethylene oxide with alcohols or phenols, fatty acid and polyol esters, derivatives of the preceding compounds with sulphate, sulphonate and phosphate groups.

The presence of at least one surface-active agent is generally essential when the inert compound and/or carrier are not soluble in water and the vehicle of application is water.

Thus, the compositions for agricultural use according to the invention may contain the active materials according to the invention within very . » wide limits ranging from 0.05 % to 95 % (by weight). Their surface-active agent content is advantageously between 0.1 % and 50 % by weight.

In the case of the compositions adapted for storage and transportation, they advantageously contain 0.5 to 95 % (by weight) of active substance, the compositions as applied to the plants being in general substantially more dilute than the compositions adapted for storage and for transportation which are more concentrated.

The compositions according to the invention are themselves in fairly diverse solid or liquid forms.

As forms of solid compositions, there may be mentioned dusting powders (with a compound content which may be as high as 100 %), wettable powders, and granules, in particular those obtained by extrusion, compaction and impregnation of a granulated carrier or by granulation of a powder (the compound content in these granules being between 0.5 and 80 % for these latter cases).

The wettable powders (or spraying powder) are usuallly prepared so as to contain 20 to 95 % of active material, and they usually contain, in addition to the solid carrier, 0 to 30 % of a wetting agent, 3 to 20 % of a dispersing agent and, when necessary, 0 to 10 % of one or more stabilisers and/or other additives such as penetrating agents, adhesives or anticaking agents, colorants and the like.

To obtain the spraying powders or wettable powders, the active materials are intimately mixed in suitable mixers with the additional substances and ground in mills or other suitable grinders. Spraying powders are thereby obtained whose wettability and suspensibility are advantageous; they may be suspended in water in any desired concentration and these suspensions may be used very advantageously in particular for application to plant leaves.

Pastes may be prepared in place of wettable powders. The conditions and details of preparation and use of these pastes are similar to those . * for wettable powders or spraying powders.

By way of example, here are various compositions of wettable powders (or spraying powders): Example F 1: * active material (compound No. 1) 50 % * ethylene oxide/fatty alcohol condensate (wetting agent) 2.5 % * ethylene oxide/phenylethylphenol condensate (dispersing agent) 5 % * chalk (inert carrier) 42.5 % Example F 2; * active material (compound No. 1) 10 % * 8 to 10 ethylene oxides/C13 oxo synthetic alcohol of the branched type (wetting agent) 0.75 % * neutral calcium lignosulphonate (dispersing agent) 12 % * calcium carbonate (inert carrier) q.s. 100 % Example F 3: this wettable powder contains the same ingredients as in the preceding example in the proportions below: * active material 75 % * wetting agent 1.50 % * dispersing agent 8 % calcium carbonate (inert filler) q.s 100 % Example F 4: * active material (compound No. 1) 90 % * ethylene oxide/fatty alcohol condensate (wetting agent) 4 % * ethylene oxide/phenylethylphenol condensate (dispersing agent) 6 % Example F 5: * active material (compound No. 1) 50 % * mixture of anionic and nonionic surface-active agents (wetting agent) 2.5 % * sodium lignosulphonate dispersing agent) 5 % * kaolinic clay (inert carrier) 42.5 % The compounds according to the invention may be formulated in the form of dispersible granules in water which are also included within the scope of this invention.

These dispersible granules, of apparent density generally between about 0.3 and 0.6, have a particle size generally between about 0.15 and 2 mm and preferably between 0.3 and 1.5 mm.

The active material content of these granules is generally between about 1 % and 90 %, and preferably between 25 % and 90 %.

The rest of the granule is essentially composed of a solid filler and, optionally, surface-active adjuvants which confer to the granule properties of dispersibility in water. These granules may be essentially of two distinct types depending on whether the filler selected is soluble in water or not. When the filler is water-soluble, it may be inorganic or, preferably, organic. Excellent results have been obtained with urea. In the case of an insoluble filler, the latter is preferably inorganic, such as for example kaolin or bentonite. In this case, it is advantageously accompanied by surface-active agents (in an amount of 2 to 20 % by weight of the granule) more than half of which for example consist of at least one dispersing agent essentially anionic, such as an alkali metal or alkaline earth metal polynaphthalenesulphonate or an alkali metal or alkaline earth metal lignosulphonate, the rest consisting of nonionic or anionic wetting agents such as an alkali metal or alkaline earth metal alkylnaphthalenesulphonate.

Moreover, although not essential, other adjuvants such as 10 antifoaming agents may be added.

The granule according to the invention may be prepared by mixing the necessary ingredients and then granulating according to several methods known in themselves (comfit-box, fluid bed, atomiser, extrusion and the like).

The process is generally completed by crushing followed by sieving to the chosen particle size within the limits mentioned above.

Preferably, the granule is obtained by extrusion, the procedures in the examples below being followed.

Example F 6: Dispersible granules The active material (compound No. 1) (90 % by weight) and pearl 20 urea (10 %) are mixed in a mixer. The mixture is then ground in a toothed roll crusher. A powder is obtained which is moistened with water (about 8 % by weight). The moist powder is extruded in a perforated roll extruder. A granule is obtained which is dried and then crushed and sieved so as to retain only the granules of size between 0.15 and 2 mm respectively.

Example F 7: Dispersible granules The following constituents are mixed in a mixer: * active material (compound No. 1) 75 % * wetting agent (sodium alkylnaphthalenesulphonate) 2 % * dispersing agent (sodium polynaphthalenesulphonate) 8 % * water-insoluble inert filler (kaolin) 15 % This mixture is granulated in a fluid bed in the presence of water and then dried, crushed and sieved so as to obtain granules of size between 0.15 and 0.80 mm.

These granules may be used alone, in solution or dispersed in water so as to obtain the desired dose. They may also be used to prepare combinations with other active materials, in particular herbicides, the latter being in the form of wettable powders or granules or aqueous suspensions.

The compounds of formula (I) may also be used in the form of dusting powders; a composition comprising the active material (50 g) and talc (950 g) may also be used; a composition comprising the active material (20 g), finely divided silica (10 g) and talc (970 g) may also be used; these constituents are mixed and ground and the mixture is applied by dusting.

As forms of liquid compositions or forms intended to constitute liquid compositions during application, there may be mentioned solutions, in particular water-soluble concentrates, emulsifiable concentrates, emulsions, concentrated suspensions, aerosols; wettable powders (or dusting powder) and pastes are solid compositions but which are intended to constitute liquid compositions during application.

The emulsifiable or soluble concentrates most often comprise 10 to 80 % of active material, the emulsions or solutions ready for application contain, for their part, 0.001 to 20 % of active material.

In addition to the solvent, the emulsifiable concentrates may contain, when necessary, 2 to 20 % of suitable additives such as the stabilisers, the surface-active agents, the penetrating agents, the corrosion inhibitors, the colorants or the adhesives previously mentioned.

Emulsions of any desired concentration, which are particularly suitable for application to crops, may be obtained from these concentrates by dilution with water.

By way of example, here are the compositions of some emulsifiable concentrates: Example F 8: * active material 400 g/l * alkali metal dodecylbenzenesulfonate 24 g/l ’ ethylene oxide/nonylphenol condensate containing 10 molecules of ethylene oxide 16 g/l * cyclohexanone 200 g/l * aromatic solvent q.s. 1 litre According to another emulsifiable concentrate formula, there are used: Example F 9: * active material 250 g * epoxidised vegetable oil 25 g * mixture of alkyiarylsulphonate and polyglycol ether and fatty alcohols 100 g * dimethylformamide 50 g * xylene 575 g The concentrated suspensions which may also be applied by spraying, are prepared so as to obtain a stable fluid product which does not form deposits and they usually contain 10 to 75 % of active material, 0.5 to 15 % of surface-active agents, 0.1 to 10 % of thixotropic agents, 0 to 10 % of suitable additives, such as antifoams, corrosion inhibitors, stabilisers, penetrating agents and adhesives and, as carrier, water or an organic liquid in which the active material is sparingly soluble or insoluble: some organic solid materials or inorganic salts may be dissolved in the carrier in order to help prevent sedimentation or as antifreezes for water.

By way of example, here is a composition of concentrated suspension: Example F 10: * compound No. 1 500 g * ethylene oxide/tristyrylphenol phosphate polycondensate 50 g 10 * ethylene oxide/alkylphenol polycondensate 50 g * sodium polycarboxylate 20 g » ethylene glycol 50 g « organopolysiloxanic oil (antifoam) 1 g 15 * polysaccharide 1.5 g « water 327.5 g The aqueous dispersions and emulsions, for example compositions obtained by diluting with water a wettable powder or an emulsifiable concentrate according to the invention, are included within the general scope of the present invention. The emulsions may be of the water-in-oil or oil-in-water type and they may have a thick consistency such as that of a mayonnaise.

Formula (Π) Formula (VIII) Formula (ΙΠ) Formula (V)

Claims (16)

1. CLAIMS l,2,4-triazolo-[4,3-b] pyridazine derivatives of formula (I): Z wherein X represents a halogen atom or RI or an alkoxy group, or a hydrogen atom; 10 Y and Z independently represent:hydrogen, halogen, R 1 , -ORI, -SR 1 , -NR 2 R 5 or cyano; Ar represents: a phenyl group optionally substituted by one or more groups which may be the same or different selected from Rl, -S(O) m R\ -OR 1 , a cycloalkyl group 15 containing from 3 to 6 carbon atoms, -OR 4 , -OR 5 , -S(O) m R 4 , -NR 2 R 4 , -NR 4 COR 1 , -OCOR 5 , -S(O) m R 5 , -NR^rS, -NR 5 COR 2 , or a halogen atom; or a 5 or 6 membered heterocycle containing one or more heteroatoms selected from oxygen, sulphur and nitrogen in the ring, which is optionally substituted by one or more groups which may be the same or different selected 20 from R 1 , -SiOJmR 1 , -OR 1 , a cycloalkyl group containing from 3 to 6 carbon atoms, -OR 4 , -OR 5 , -S(O)mR 4 , -NR 2 R 4 , -NR^OR 1 , -OCOR 5 , -S(O)mR 5 , -NR 2 R 5 , -NR 5 COR 2 , or a halogen atom; R 1 represents a straight- or branched- chain alkyl group containing from 1 to 6 carbon atoms optionally substituted by one or more halogen atoms; 25 R 2 and R^ independently represent the hydrogen atom or a straight- or branched- chain alkyl group containing up to 4 carbon atoms optionally substituted by one or more halogen atoms; represents a phenyl group optionally substituted by one or more groups selected from R 1 , -S(O) m R\ -OR 1 , -NR 2 R3, a cycloalkyl group containing from 3 to 6 carbon atoms, or a halogen atom; 5 R^ represents a 5 or 6 membered heterocycle containing one or more heteroatoms in the ring selected from oxygen, sulphur and nitrogen; m represents zero, 1 or 2; provided that when X represents chlorine and Y and Z each represent hydrogen, Ar represents a group other than unsubstituted phenyl, 3- or 4- chloro-, methyl10 or methoxy-phenyl, 3-methoxy-4-methylphenyl. 2,3,4-trimethoxyphenyl or 3,4-dichlorophenyl; and when X represents hydrogen, methyl or methoxy and Y and Z represent hydrogen, Ar represents a group other than unsubstituted phenyl; and agriculturally acceptable salts thereof.

2. ) A compound according to claim 1 wherein: * X, Y and Z represent a hydrogen or a halogen atom or an alkyl or haloalkyl or alkoxy group, * Ar represents a phenyl group, optionally mono- or 20 polysubstituted by a lower alkyl or a lower alkoxy or a lower alkylthio or a phenyl group or a halogen atom, preferably chlorine or fluorine, or a heterocycle Het, * Het represents a 5 or 6-membered heterocycle containing a heteroatom such as sulphur, nitrogen or oxygen, this heterocycle being optionally mono- or polysubstituted by a lower alkyl or a lower alkoxy or a lower alkylthio 25 group or a halogen atom, preferably chlorine or fluorine.

3. ) A compound according to claim 1 or 2, wherein Ar is monosubstituted and Het represents a thienyl radical.

4. ) A compound according to any one of claims 1 to 3, wherein: only one of the three radicals X, Y or Z represents a radical other than a hydrogen atom, when X, Y or Z are halogen atoms, they represent chlorine atoms, when,X, Y or Z are a hydrocarbon radical, at least partially, this radical preferably has 1 to 4 carbon atoms.

5. ) A compound according to any one of claims 1 to 4, wherein Z represents R 1 or a halogen atom.

6. ) A compound according to any one of claims 1 to 4, wherein Z is the hydrogen atom or a chlorine atom or a methyl group.

7. ) A compound according to claim 6, wherein X is the hydrogen atom and Y is a methyl group.

8. ) A herbicidal composition which comprises as active ingredient a herbicidally effective amount of a triazolopyridazine derivative of formula (I) according to any one of claims 1 to 7 or an agriculturally acceptable salt thereof, in association with an agriculturally acceptable diluent or carrier and/or surface active agent.

9. ) A process for weed control at a locus which comprises applying to the locus a herbicidally effective amount of a triazolopyridazine derivative of formula (I) according to any one of claims 1 to 7 or an agriculturally acceptable salt thereof.

10. ) A process for preparing a triazolopyridazine derivative of formula (I) according to claim 1 or 2 which comprises the oxidation of an arylidene-2-(pyridaz-3’*yl)hydrazine type compound of formula (II): Z Formula (Π) by an oxidising agent, according to a cyclising oxidation reaction, and optionally converting the compound thus obtained into an agriculturally acceptable salt thereof.

11. ) A process according to claim 9, wherein the oxidising agent is chosen from metal cations derived from metals having several oxidation levels and being at a high oxidation level, or atmospheric oxygen.

12. ) A process for preparing a triazolopyridazine derivative of formula (I) according to claim 1 or 2 which comprises the dehydration of a compound of the 3-(aroylhydrazino)pyridazine type of formula (III): Formula (III) in which the various substituents are as defined in claim lor 2, (cyclising dehydration), and optionally converting the compound thus obtained into an agriculturally acceptable salt thereof. 1¾) A process for preparing a triazolopyridazine derivative of formula (I) according to claim 1 or 2 which comprises the reaction of a compound of the hydrazine type of formula (V): Z Formula (V) with a compound of formula (VI): Ui-C(=Wi)-Ar according to the reaction: (V) + (VI) -► (I) + U X H + W 1 H 2 the various radicals in these formulae (V) and (VI) being as defined in claim 1 or 2; and Wj represents an oxygen atom or an NH group, when Wi represents the oxygen atom, then Uj represents a hydroxyl or an alkoxy or an aroyloxy group, or a halogen atom, 5 when W| represents an NH group, then Uj represents an alkoxy or . an alkylthio or an arylalkylthio group, and'optionally converting the compound thus obtained into an agriculturally acceptable salt thereof.

13. 14) A process for preparing a triazolopyridazine derivative of 10 formula (I) according to claim 1 or 2 in which X is a hydrogen atom, wherein a compound of formula (I) according to claim 1 in which X is a halogen atom, is hydrogenolysed.

14. 15) A process for the preparing a triazolopyridazine derivative of formula (I) according to claim 1 or 2 in which Z represents a chlorine or 15 bromine and X and Y represent hydrogen or Rlwhich comprises the reaction of a compound of formula (IX): 20 wherein X and Y represent hydrogen or Rl, with a halogenating agent to convert the hydroxy group to a chlorine or bromine atom, and optionally converting the compound thus obtained into an agriculturally acceptable salt thereof.

15. 16) A process for preparing a triazolopyridazine derivative of formula (I) according to claim 1 or 2 in which Z represents fluorine and X and Y 25 represent hydrogen or R 1 , which comprises the reaction of a compound of formula (I) in which Z represents chlorine or bromine and X and Y represent hydrogen or R.1, with a salt of formula M-F in which M represents an alkali- or alkaline earth metal.

16. 17) A process for preparing arylidene-2-(pyridaz-3’yl)hydrazines of formula (II) as defined in claim 10, which comprises the reaction of a 3-hydrazinopyridazine of formula (V) as defined in claim 12 with an aldehyde of formula Ar-CHO in which the symbols X, Y, Z and Ar have the meanings indicated in claim 1 or 2. W A process for preparing 3-(aroylhydrazino)pyridazines of formula (III) as defined in claim 11, which comprises the reaction of a 3hydrazinopyridazine of formula (V) defined in claim 11 with compounds of formula (VII): Ar-CO-U2 in which the symbols X, Y, Z and Ar have the meanings indicated in claim 1 or 2, and U2 has one of the meanings indicated for Ui as defined in claim 12, according to the scheme: (V) + (VII) -► (HI) + U 2 H 13Ί A process for preparing 3-(aroylhydrazino)pyridazines of formula (III) as defined in claim 11 which comprises the reaction of a pyridazine derivative of formula (VIII): Formula (VIII) with an arylhydrazide of formula Ar-CO-NH-NH 2 , in which the symbols X, Y, Z 20 and Ar are as defined in claim 1 or 2 and T is a halogen atom. jLCj Compounds which may be used as intermediates for the preparation of the compounds according to claim 1 or 2 and which are of one of the formulae (Π), (ΠΙ), (V) and (VIH): Formula (III) Formula (V) in which the various symbols have the meanings given in claim 1,2 or 19, with the proviso that: 5 i) for compounds of formula (II): when X represents 1-methyl-l-ethylpropyl and Y and Z each represent hydrogen, Ar is not 4-n-butoxyphenyl, 2,4-, 2,5- or 3,5-dimethylphenyl, 3-bromophenyl, 2,4- or 3,5-dichlorophenyl, 2-, or 4-chlorophenyl, or 2,4dimethoxyphenyl, 10 when X, Y and Z each represent methyl, Ar is not unsubstituted phenyl, when X and Z each represent methyl and Y represents hydrogen, Ar is not phenyl unsubstituted or substituted only by chlorine, when X represents chlorine and Y and Z each represent hydrogen, Ar is not phenyl unsubstituted or substituted only by chlorine or methoxy; 15 ii) for compounds of formula (V), when Y and Z each represent methyl. is not chlorine; and iii) for compounds of formula (VIII), when T represents chlorine, and Y and Z each represent methyl, X is not hydrogen or chlorine, 20 when Y and Z each represent hydrogen, X is not methyl, butyl, trichloromethyl or halogen, when T and Y each represent chlorine, X and Z represent groups other than chlorine. 21 ) substantially as A compound as claimed in claim 1, hereinbefore described and exemplified. 22) 8, substantially A herbicidal composition according to claim as hereinbefore described and exemplified. 23) A process according to claim 9 for weed control, substantially as hereinbefore described. 24) claimed in claim and exemplified. A process for preparing a compound as 1, substantially as hereinbefore described 25) A compound as claimed in claim 1, whenever prepared by a process claimed in any one of claims 10-16 or 24. 26) A compound according to claim 20, substantially as hereinbefore described and exemplified.