Process for preparing pyridazin-3-on derivatives

This application is the national phase under 35 U.S.C. § 371 of PCT, International Application Ser. No. PCT/JP99/06842 which has an International filing date of Dec. 7, 1999, which designated the United States of America and was published in English.

The present invention relates to a process for preparing pyridazin-3-on derivatives.

WO97/7104 discloses that pyridazin-3-on derivatives have good herbicidal activities, and WO98/17632 discloses that carboxylic acids derivatives and their salts are useful intermediates for the preparation of pyridazin-3-on derivatives, and a process for preparing pyridazin-3-on derivatives from such intermediates. For example, WO98/17632 discloses a process of reacting a lower carboxylic acid and a base with such an intermediate.

However, the disclosed process does not always produce a desired product at an industrially satisfactory yield and purity.

One object of the. present invention is to provide a process for preparing pyridazin-3-on derivatives from carboxylic acid derivatives or their salts advantageously in an industrial scale.

This and other objects are accomplished by a method for preparing a pyridazin-3-on derivative of the formula (1):

wherein R 2 is a hydrogen atom or a C 1 -C 3 alkyl group, R 3 is a hydrogen atom or a C 1 -C 3 alkyl group, and Q is a phenyl group which may optionally be substituted, comprising the step of ring closing a carboxylic acid derivative of the formula (2):

wherein R 2 , R 3 and Q are the same as defined above, or its salt in the presence of a nitrogen-containing aromatic compound and a boron compound.

The carboxylic acid of the formula (2) or its salt, which is a raw material used; in the process of the present invention, will be explained.

In the carboxylic acid of the formula (2) or its salt, examples of a substituent which may optionally present on the phenyl group Q include halogen atoms, and a group of the formula: —ZR 1 in which Z is an oxygen atom or a sulfur atom, and R 1 is a hydrogen atom, a C 1 -C 6 alkyl group, a C 1 -C 6 haloalkyl group, a C 3 -C 8 cycloalkyl group, a benzyl group, a C 3 -C 6 alkenyl group, a C 3 -C 6 haloalkenyl group, a C 3 -C 6 alkynyl group, a C 3 -C 6 haloalkynyl group, a cyano-C 1 -C 6 alkyl group, a C 2 -C 8 (alkoxyalkyl) group, a C 2 -C, (alkoxythioalkyl) group, a carboxy-C 1 -C 6 alkyl group, (C 1 -C 8 alkoxy) carbonyl-C 1 -C 6 alkyl group, [(C 1 -C 4 alkoxy)-C 1 -C 4 alkoxy]carbonyl-C 1 -C 6 alkyl group, a (C 3 -C 8 cycloalkoxy)carbonyl-C 1 -C 6 alkyl group or a [(C 1 -C 6 alkoxy)carbonyl-C 1 -C 6 alkyl]oxycarbonyl-C 1 -C 6 alkyl group, wherein the positions and number of the substituents are arbitrary.

Preferably, the group Q is an optionally substituted phenyl group of the formula (3):

wherein X is a hydrogen atom or a halogen atom, Y is a halogen atom, and W is a hydrogen atom or a group of the formula: —ZR 1 in which Z and R 1 are the same as defined above.

Examples of the halogen atom for X and Y include a fluorine atom, a chlorine atom, a bromine atom, etc.

Examples of the C 1 -C 6 alkyl group for R 1 include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert.-butyl group, an amyl group, an isoamyl group, a tert.-amyl group, etc.

Examples of the C 1 -C 6 haloalkyl group include a 2-chloroethyl group, a 2-bromoethyl group, a 2,2,2-trifluoroethyl group, etc.

Examples of the C 3 -C 8 cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc.

Examples of the C 3 -C 6 alkenyl group include an allyl group, a 1-methyl-2-propenyl group, a 3-butenyl group, a 2-butenyl group, a 3-methyl-2-butenyl group, a 2-methyl-3-butenyl group, etc.

Examples of the C 3 -C 6 haloalkenyl group include a 2-chloro-2-propenyl group, a 3,3-dichloro-2-propenyl group, etc.

Examples of the C 3 -C 6 alkynyl group include a propargyl group, a 1-methyl-2-propynyl group, a 2-butynyl group, a 1,1-dimethyl-2-propynyl group, etc.

Examples of the C 3 -C 6 haloalkynyl group include 3-bromopropargyl group, etc.

Examples of the cyano-C 1 -C 6 alkyl group include a cyanomethyl group, etc.

Examples of the C 2 -C 8 alkoxyalkyl group include a methoxymethyl group, a methoxyethyl group, an ethoxymethyl group, an ethoxyethyl group, etc.

Examples of the C 2 -C 8 alkylthioalkyl group include a methylthiomethyl group, a methylthioethyl group, etc.

Examples of the carboxy-C 1 -C 6 alkyl group include a carboxymethyl group, a 1-carboxyethyl group, a 2-carboxyethyl group, etc.

Examples of the (C 1 -C 8 alkoxy)carbonyl-C 1 -C 6 alkyl group include a methoxycarbonylmethyl group, an ethoxycarbonylmethyl group, a propoxycarbonylmethyl group, an isopropoxycarbonylmethyl group, a butoxycarbony.methyl group, an isobutoxycarbonylmethyl group, a tert.-butoxycarbonylmethyl group, an amyloxycarbonylmethyl group, an isoamyloxycarbonylmethyl group, a tert.-amyloxy-carbonylmethyl group, a 1-methoxycarbonylethyl group, a 1-ethoxycarbonylethyl group, a 1-propoxycarbonylethyl group, a 1-isopropoxycarbonylethyl group, a 1-butoxycarbonylethyl group, a 1-isobutoxycarbonylethyl group, a 1-tert.-butoxycarbonylethyl group, a 1-amyloxycarbonylethyl group, a 1-isoamyloxycarbony-ethyl group, a 1-tert.-amyloxycarbonylethyl group, etc.

Examples of the [(C 1 -C 4 alkoxy)-C 1 -C 4 alkoxy]carbonyl-C 1 -C 6 alkyl group include a methoxymethoxycarbonylmethyl group, a methoxyethoxycarbonylmethyl group, a 1-methoxyethoxycarbonylethyl group, etc.

Examples of the (C 3 -C 8 cycloalkoxy)carbonyl-C 1 -C 6 alkyl group include a cyclobutyloxycarbonylmethyl group, a cyclopentyloxycarbonylmethyl group, a cyclohexyloxycarbonyl-methyl group, a 1-cyclobutyloxycarbonylethyl group, a 1-cyclopentyloxycarbonylethyl group, a 1-cyclohexyloxy-carbonylethyl group, etc.

Examples of the [(C 1 -C 6 alkoxy)carbonyl-C 1 -C 6 alkyl]oxy-carbonyl-C 1 -C 6 alkyl group include a (methoxycarbonyl)methoxycarbonylmethyl group, an (ethoxycarbonyl)methoxycarbonylmethyl group, etc.

Examples of the C 1 -C 3 alkyl group for R 2 and R 3 include a methyl group, an ethyl group, a propyl group, etc.

The salts of the carboxylic acid derivative of the formula (2) may be the salts of the above exemplified carboxylic acids and organic bases. Examples of such organic bases include nitrogen-containing aromatic compounds (e.g. pyridine, 4-dimethylaminopyridine, 2-picoline, 3-picoline, 4-picoline, 5-ethyl-2-methylpyridine, etc.), dialkylaniline derivatives (e.g. N,N-dimethylaniline, N,N-diethylaniline, etc.), tertiary amines (e.g. triethylamine, diisopropylethylamine, tri-n-propylamine, tri-n-butylamine, etc.), and the like.

Hereinafter, the specific carboxylic acid derivatives of the formula (2) as the raw materials are exemplified:

However, the raw materials that can be used in the present invention are not limited thereto.

Examples of the a boron compound to be used in the process of the present invention are as follows:

wherein R 4 , R 1 and R 6 are the same and different and represent a hydroxyl group, a C 1 -C 6 alkyl group, a C 1 -C 6 alkoxy group, a phenyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom, a C 1 -C 4 alkyl group, a C 1 -C 3 haloalkyl group, a C 1 -C 3 alkoxy group, a nitro group, an amino group, a carboxyl group, a C 1 -C 3 amide group, a formyl group, a C 1 -C 3 alkylthio group, a dihydroxylboryl group, or a phenyl group which may optionally be substituted with a dihydroxyboryl group), a naphthyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom, a C 1 -C 4 alkyl group or a C 1 -C 3 haloalkyl group), a thienyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom or a C 1 -C 4 alkyl group), a furyl group which may optionally be substituted with at least one substituent (e.g. a halogen atom or a C 1 -C 4 alkyl group), a benzofuranyl group the benzene group of which may optionally be substituted with at least one substituent (e.g. a halogen atom, a C 1 -C 4 alkyl group or a C 1 -C 3 haloalkyl group), or R 4 and R 5 together form a ring;

a polymeric boric acid of the formula (5):

wherein R 4 and R 5 are the same as defined above, or R 4 and R 5 together form a ring, and n is an integer of at least 1; or a boroxine derivative of the formula (6):

wherein R 4 is the same as defined above; or mixtures thereof.

Examples of the C 1 -C 6 alkoxy group for R 4 , R 5 and R 6 in the formulae (4), (5) and (6) include a methoxy group, an ethoxy group, an isopropoxy group, a n-butoxy group, a tert.-butyl group, etc.

Examples of the C 1 -C 6 alkyl group include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a sec.-butyl group, a tert.-butyl group, a n-pentyl group, a cyclopentyl group, a n-hexyl group, a cyclohexyl group, etc.

Examples of the phenyl group which may optionally be substituted include a phenyl group, a 2-fluorophenyl group, a 3-fluorophenyl group, a 4-fluorophenyl group, a 2-chlorophenyl group, a 3-chlorophenyl group, a 4-chlorophenyl group, a 2-bromophenyl group, a 3-bromophenyl group, a 4-bromophenyl group, a 2,3-difluorophenyl group, a 3,4-difluorophenyl group, a 2,4-difluorophenyl group, a 2,5-difluorophenyl group, a 2,6-difluorophenyl group, a 3,5-difluorophenyl group, 2,3-dichlorophenyl group, a 3,4-dichlorophenyl group, a 2,4-dichlorophenyl group,;a 2,5-dichlorophenyl group, a 2,6-dichlorophenyl group, a 3,5-dichlorophenyl group, a 2,3-dibromophenyl group, a 3,4-dibromophenyl group, a 2,4-dibromophenyl group, a 2,5-dibromophenyl group, a 2,6-dibromophenyl group, a 3,5-dibromophenyl group, a 2-chloro-3-fluorophenyl group, a 3-chloro-2-fluorophenyl group, a 2-chloro-4-fluorophenyl group, a 4-chloro -2-fluorophenyl group, a 2-chloro-5-fluorophenyl group, a 5-chloro-2-fluorophenyl group, a 2-chloro-6-fluorophenyl group, a 3-chloro-4-fluorophenyl group, a 4-chloro-3-fluorophenyl group, a 3-chloro-5-fluorophenyl group, a 2-bromo-3-fluorophenyl group, a 3-bromo-2-fluorophenyl group, a 2-bromo-4-fluorophenyl group, a 4-bromo-2-fluorophenyl group, a 2-bromo-5-fluorophenyl group, a 5-bromo-2-fluorophenyl group, a 2-bromo-6-fluorophenyl group, a 3-bromo-4-fluorophenyl group, a 4-bromo-3-fluorophenyl group, a 3-bromo-5-fluorophenyl group, a 2-bromo-3-chlorophenyl group, a 3-bromo-2-chlorophenyl group, a 2-bromo-4-chlorophenyl group, a 4-bromo-2-chlorophenyl group, a 2-bromo-5-chlorophenyl group, a 5-bromo-2-chlorophenyl group, a 2-bromo-6-chlorophenyl group, a 3-bromo-4-chlorophenyl group, a 4-bromo-3-chlorophenyl group, a 3-bromo-5-chlorophenyl group, a 2,3,4-trifluorophenyl group, a 3,4,5-trifluorophenyl group, a 2,3,4-trichlorophenyl group, a 3,4,5-trichlorophenyl group, a 2,3,4-tribromophenyl group, a 3,4,5-tribromophenyl group, a 2-tolyl group, a 3-tolyl group, a 4-tolyl group, a 2-ethylphenyl group, a 3-ethylphenyl group, a 4-ethylphenyl group, a 2,3-xylyl group, a 3,4-xylyl group, a 2,4-xylyl group, a 2,5-xylyl group, a 2,6-xylyl group, a 3,5-xylyl group, a mesityl group, a 2-trifluoromethylphenyl group, a 3-trifluoromethylphenyl group, a 4-trifluoromethylphenyl group, a 3,5-bis (trifluoromethyl)phenyl group, a 2-anisyl group, a 3-anisyl group, a 4-anisyl group, a 2-nitrophenyl group, a 3-nitrophenyl group, a 4-nitrophenyl group, a 2-aminophenyl group, a 3-aminophenyl group, a 4-aminophenyl group, a 2-carboxyphenyl group, a 3-carboxyphenyl group, a 4-carboxyphenyl group, a 2-acetamidophenyl group, a 3-acetamidophenyl group, a 4-acetamidophenyl group, a 2-formylphenyl group, a 3-formylphenyl group, a 4-formylphenyl group, a 2-methylthiophenyl group, a 3-methylthiophenyl group, a 4-methylthiophenyl group, a 2-(dihydroxyboryl)phenyl group, a 3-(dihydroxyboryl)phenyl group, a 4-(dihydroxyboryl)phenyl group, a 2-biphenyl group, a 3-biphenyl group, a 4-biphenyl group, a 4-[4′-(dihydroxyboryl)phenyl]phenyl group, etc.

Examples of the naphthyl group which may optionally be substituted include a 1-naphthyl group, 2-naphthyl group, a 3-fluoro-1-naphthyl group, a 4-fluoro-1-naphthyl group, a 5-fluoro-1-naphthyl group, a 6-fluoro-1-naphthyl group, a 3-fluoro-2-naphthyl group, a 4-fluoro-2-naphthyl group, a 5-fluoro-2-naphthyl group, a 6-fluoro-2-naphthyl group, a 3-chloro-1-naphthyl group, a 4-chloro-1-naphthyl group, a 5-chloro-1-naphthyl group, a 6-chloro-1-naphthyl group, a 3-chloro-2-naphthyl group, a 4-chloro-2-naphthyl group, a 5-chloro-2-naphthyl group, a 6-chloro-2-naphthyl group, a 3-bromo-1-naphthyl group, a 4-bromo-1-naphthyl group, a 5-bromo-1-naphthyl group, a 6-bromo-1-naphthyl group, a 3-bromo-2-naphthyl group, a 4-bromo-2-naphthyl group, a 5-bromo-2-naphthyl group, a 6-bromo-2-naphthyl group, a 3-methyl-o-naphthyl group, a 4-methyl-1-naphthyl group, a 5-methyl-1-naphthyl group, a 6-methyl-1-naphthyl group, a 3-methyl-2-naphthyl group, a 4-methyl-2-naphthyl group, a 5-methyl-2-naphthyl group, a 4-methyl-2-naphthyl group, a 5-methyl-2-naphthyl group, a 6-methyl-2-naphthyl group, a 3-trifluoromethyl-1-naphthyl group, a 4-trifluoromethyl-1-naphthyl group, a 5-trifluoromethyl-1-naphthyl group, a 6-trifluoromethyl-1-naphthyl group, a 3-trifluoromethyl-2-naphthyl group, a 4-trifluoromethyl-2-naphthyl group, a 5-trifluoromethyl-2-naphthyl group, a 6-trifluoromethyl-2-naphthyl group, etc.

Examples of the thienyl group which may optionally be substituted include a 2-thienyl group, a 3-thienyl group, a 3-fluoro-2-thienyl group, a 4-fluoro-2-thienyl group, a 5-fluoro-2-thienyl group, a 2-fluoro-3-thienyl group, a 4-fluoro-3-thienyl group, a 5-fluoro-3-thienyl group, a 3-chloro-2-thienyl group, a 4-chloro-2-thienyl group, a 5-chloro-2-thienyl group, a 2-chloro-3-thienyl group, a 4-chloro-3-thienyl group, a 5-chloro-3-thienyl group, a 3-bromo-2-thienyl group, a 4-bromo-2-thienyl group, a 5-bromo-2-thienyl group, a 2-bromo-3-thienyl group, a 4-bromo-3-thienyl group, a 5-bromo-3-thienyl group, a 3-methyl-2-thienyl group, a 4-methyl-2-thienyl group, a 5-methyl-2-thienyl group, a 2-methyl-3-thienyl group, a 4-methyl-3-thienyl group, a 5-methyl-3-thienyl group, etc.

Examples of the furyl group which may optionally be substituted include a-2-furyl group, a 3-furyl group, a 3-fluoro-2-furyl group, a 4-fluoro-2-furyl group, a 5-fluoro-2-furyl group, a 2-fluoro-3-furyl group, a 4-fluoro-3-furyl group, a 5-fluoro-3-furyl group, a 3-chloro-2-furyl group, a 4-chloro-2-furyl group,-a 5-chloro-2-furyl group, a 2-chloro-3-furyl group, a 4-chloro-3-furyl group, a 5-chloro-3-furyl group, a 3-bromo-2-furyl group, a 4-bromo-2-furyl group, a 5-bromo-2-furyl group, a 2-bromo-3-furyl group, a 4-bromo-3-furyl group, a 5-bromo-3-furyl group, a 3-methyl-2-furyl group, a 4-methyl-2-furyl group, a 5-methyl-2-furyl group, a 2-methyl-3-furyl group, a 4-methyl-3-furyl group, a 2-methyl-3-furyl group, etc.

Examples of the benzofuranyl group which may optionally be substituted include a 2-benzofuranyl group, a 3-benzofuranyl group, a 4-fluoro-2-benzofuranyl group, a 5-fluoro-2-benzofuranyl group, a 6-fluoro-2-benzofuranyl group, a 7-fluoro-2-benzofuranyl group, a 4-fluoro-3-benzofuranyl group, a 5-fluoro-3-benzofuranyl group, a 6-fluoro-3-benzofuranyl group, a 7-fluoro-3-benzofuranyl group, a 4-chloro-2-benzofuranyl group, a 5-chloro-2-benzofuranyl group, a 6-chloro-2-benzofuranyl group, a 7-chloro-2-benzofuranyl group, a 4-chloro-3-benzofuranyl group, a 5-chloro-3-benzofuranyl group, a 6-chloro-3-benzofuranyl group, a 7-chloro-3-benzofuranyl group, a 4-bromo-2-benzofuranyl group, a 5-bromo-2-benzofuranyl group, a 6-bromo-2-benzofuranyl group, a 7-bromo-2-benzofuranyl group, a 4-bromo-3-benzofuranyl group, a 5-bromo-3-benzofuranyl group, a 6-bromo-3-benzofuranyl group, a 7-bromo-3-benzofuranyl group, a 4-methyl-2-benzofuranyl group, a 5-methyl-2-benzofuranyl group, a 6-methyl-2-benzofuranyl group, a 7-methyl-2-benzofuranyl group, a 4-methyl-3-benzofuranyl group, a 5-methyl-3-benzofuranyl group, a 6-methyl-3-benzofuranyl group, a 7-methyl-3-benzofuranyl group, a 4-trifluoromethyl-2-benzofuranyl group, a 5-trifluoromethyl-2-benzofuranyl group, a 6-trifluoromethyl-2-benzofuranyl group, a 7-trifluoromethyl-2-benzofuranyl group, a 4-trifluoromethyl-3-benzofuranyl group, a 5-trifluoromethyl-3-benzofuranyl group, a 6-trifluoromethyl-3-benzofuranyl group, a 7-trifluoromethyl-3-benzofuranyl group, etc.

Examples of the combined group of R 4 and R 5 which form a ring include a C 4 -C 5 alkylene group which may be substituted with at least one methyl group such as a 1,4-tetramethylene group, or a 1,5-pentamethylene group, and a C 2 -C 4 alkylenedioxy group !which may be substituted with at least one methyl group such as a 1,2-ethylenedioxy group, a 1,2-(1,1,2,2-tetramethyl)ethylene-dioxy group or a 1,3-tetramethylenedioxy group, and a 1,2-phenylenedioxy group, etc.

Examples of the borane compound of the formula (4) include boric acid derivatives (e.g. methylboric acid, ethylboric acid, isopropylboric acid, n-butylboric acid, n-pentylboric acid, cyclopentylboric acid, n-hexylboric acid, cyclohexylboric acid, phenylboric acid, 2-flutiorophenylboric acid, 3-fluorophenylboric acid, 4-fluorophenylboric acid, 2-chlorophenylboric acid, 3-chlorophenylboric acid, 4-chlorophenylboric acid, 2-bromo-phenylboric acid, 3-bromophenylboric acid, 4-bromophenylboric acid, 3,5-difluorophenylboric acid, 2,3-dichlorophenylboric acid, 3,4-dichlorophenylboric acid, 2,4-dichlorophenylboric acid, 3, 5-dichlorophenylboric acid, 3, 5-dibromophenylboric acid, 3-chloro-4-fluorophenylboric acid, 3,4,5-trifluorophenylboric acid, 3,4,5-trichlorophenylboric acid, 3,4,5-tribromophenyl-boric acid, 2,3,4,5,6-pentafluorophenylboric acid, 2-tolylboric acid, 3-tolylboric acid, 4-tolylboric acid, 4-ethylphenylboric acid, 3,4-xylylboric acid, mesitylboric acid, 2-trifluoromethylphenylboric acid, 3-trifluoromethylphenylboric acid, 4-trifluoromethylphenylboric acid, 3,5-bis(trifluoromethyl)phenylboric acid, 2-anisylboric acid, 3-anisylboric acid, 4-anisylboric acid, 3-nitrophenylboric acid, 4-nitrophenylboric acid, 3-aminophenylboric acid, 2-carboxyphenylboric acid, 4-carboxyphenylboric acid, 3-acetamidophenylboric acid, 2-formylphenylboric acid, 3-formylphenylboric acid, 4-formylphenylboric acid, 2-methylthiophenylboric acid, 4-methylthiophenylboric acid, 4-biphenylboric acid, 1,2-phenylenediboric acid, 1,3-phenylenediboric acid, 1,4-phenylenediboric acid, 4,4′-biphenyleneboric acid, 1-naphthylboric acid, 2-naphthylboric acid, 2-thienylboric acid, 3-thienylboric acid, 5-chloro-2-thienylboric acid, 2-furylboric acid, 3-furylboric acid, 2-benzofuranylboric acid, 3-benzofuranylboric acid, etc.);

borinic acid derivatives (e.g. dimethylborinic acid, diethylborinic acid, diphenylborinic acid, bis(3,4,5-trifluorophenyl)borinic acid, bis(2,3,4,5,6-pentafluorophenyl) borinic acid, bis (4-methylphenyl)borinic acid, bis[3,5-bis(trifluoromethyl)-phenyl]borinic acid, etc.);

trimethylborane, triethylborane, triphenylborane, tris(3,4,5-trifluorophenyl)borane, tris(2,3,4,5,6-pentafluorophenyl)borane, tris(4-methylphenyl)borane, tris[3,5-bis(trifluorqmethyl)phenyl]borane, tris(3-nitrophenyl)borane, dimethoxyphenylborane, 2-phenyl-1,3,2-dioxabororane, 2-phenyl-4,4,5,5-tetramethyl-1,3,2-dioxabororane, dimethdxy-(4-methylphenyl)borane, 2-(4-methyl)phenyl-1,3,2-dioxabororane, 2-(4-methyl)phenyl-4,4,5,5-tetramethyl-1,3,2-dioxabororane, dimethoxy-(3,4,5-trifluorophenyl)borane, 2-(3,4,5-trifluoro)phenyl-1,3,2-dioxabororane, 2-(3,4,5-trifluoro)phenyl-4,4,5,5-tetramethyl-1,3,2-dioxabororane, dimethoxy-(2,3,4,5,6-pentafluorophenyl)borane, 2-(2,3,4,5,6-pentafluoro)phenyl-1,3,2-dioxabororane, 2-(2,3,4,5,6-pentafluoro)phenyl-4,4,5,5-tetramethyl-1,3,2-dioxabororane, dimethoxy-(3,5-bistrifluoro-methyl)phenylborane, 2-(3,5-bistrifluoromethyl)phenyl-1,3,2-dioxabororane, 2-(3,5-bistrifluoromethyl)phenyl-4,4,5,5-tetramethyl-1,3,2-dioxabororane, dimethoxy-(3-nitrophenyl)-borane, 2-(3-nitro)phenyl-1,3,2-dioxabororane, 2-(3-nitro)phenyl-4,4,5,5-tetramethyl-1,3,2-dioxabororane, etc.

In a polymeric boric acid of the formula (5), n is an integer of 1 or more, and preferably from 1 to 5.

Examples of the polymeric boric acid of the formula (5) include boric acid derivatives or borinic acid derivative, and their anhydrides among the above borane compounds of the formula (4).

Examples of thelboroxine derivative of the formula (6) include trimethylboroxine, triethylboroxine, triphenylboroxine, tris(3,4,5-trifluorophneyl)boroxine, tris(2,3,4,5,6-pentafluorophenyl)boroxine, tris(4-methylphenyl)boroxine, tris[3,5-bis(trifluoromethyl)phenyl]boroxine, tris(3-nitrophenyl)boroxine, etc.

Preferred examples of the borane compound (4), the polymeric boric acid (5) or the boroxine derivative (6) include methylboric acid, n-butylboric acid, phenylboric acid, 3-fluorophenylboric acid, 4-fluorophenylboric acid, 4-chlorophenylboric acid, 4-bromophenylboric acid, 3,5-dichlorophenylboric acid, 3-chloro-4-fluorophenylboric acid, 4-tolylboric acid, 3-trifluoromethylphenylboric acid, 4-trifluoromethylphenylboric acid, 3,5-bis(trifluoromethyl)phenylboric acid, 3-anisylboric acid, 3-nitrophenylboric acid; 4-carboxyphenylboric acid, 3-acetamidophenylboric acid, 3-formylphenylboric acid, 4-formylphenylboric acid, 4-methylthiophenylboric acid, 2-naphthylboric acid, 1,4-phenylenediboric acid, diphenylborinic acid, bis(4-methylphenyl)borinic acid, and their polymeric derivatives (anhydrides); triphenylborane, tris(4-methylphenyl)borane, triphenylboroxine, tris(4-methylphenyl)boroxine, and the like. Particularly preferred compounds are phenylboric acid, 4-tolylboric acid and their anhydrides; triphenylboroxine and tris(4-methyl)phenylboroxine.

Among the borane compounds of the formula (4), borinic acid derivatives in which one of R 4 , R 5 and R 6 is a hydroxyl group, or boric acid derivatives in which two of R 4 , R 5 and R 6 are hydroxyl groups may also form polymeric derivatives (anhydrides) represented by the formula (5) or (6). In the present invention, monomeric compounds, polymeric compounds and their mixtures can be used.

Now, a nitrogen-containing aromatic compound used in the process of the present invention is explained.

A nitrogen-containing aromatic compound used in the process of the present invention is usually pyridine, quinoline or isoquinoline, which may optionally be substituted with at least one substituent is selected from a halogen atom (e.g. a fluorine atom, a chlorine atom, a bromine atom and an iodine atom), a C 1 -C 3 alkyl group (e.g. a methyl group, an ethyl group, a propyl group, an isopropyl group, etc.) and a di-(C 1 -C 3 alkyl)amino group.

Specific examples of such a nitrogen-containing aromatic compound include pyridine, quinoline, isoquinoline, 4-dimethylaminopyridine, 2-picoline, 3-picoline, 4-picoline, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, 3,4-lutidine, 3,5-lutidine, 3-chloropyridine, 2-ethyl-3-methylpyridine, 5-ethyl-2-methylpyridine, etc.

Preferred nitrogen-containing aromatic compounds are pyridines which may be substituted with at least one alkyl group, in particular, at least one C 1 -C 3 alkyl group, for example, 2-picoline, 2,3-lutidine, 2,4-lutidine, 2,5-lutidine, 2,6-lutidine, 2-ethyl-3-methylpyridine, 5-ethyl-2-methylpyridine,etc. Among them, pyridines having a substituent at the 2-position, for example, 5-ethyl-2-methylpyridine are particularly preferred.

The combination of a boron compound and a nitrogen-containing aromatic compound can be the combination of the above exemplified compounds. In particular, the combination of phenylboric acid and 5-ethyl-2-methylpyridine, the combination of 4-tolylboric acid and 5-ethyl-2-methylpyridine, the combination of triphenylboroxine and 5-ethyl-2-methylpyridine, and the combination of tris(4-methylphenyl)boroxine and 5-ethyl-2-methylpyridine are preferred from the viewpoint of overall properties.

The process of the present invention is usually carried out in a solvent. A reaction temperature is usually in the range between about 50° C. and about 250° C., preferably in the range between about 100° C. and about 200° C. A reaction time is usually from split second to about 48 hours, preferably from 1 to 24 hours.

Examples of a solvent which may be used in the process of the present invention:include aliphatic hydrocarbons (e.g. heptane, octane, ligroin, etc.), aromatic hydrocarbons (e.g. benzene, toluene, ethylbenzene, xylene, mesitylene, etc.), halogeneated hydrocarbons (e.g. 1,2-dichloroethane, chlorobenzene, dichlorobenzene, trichlorobenzene, etc.), ethers (e.g. 1,4-dioxane, ethylene glycol dimethyl ether, methyl tert.-butyl ether, etc.), ketones (e.g. methyl isobutyl ketone, cyclohexanone, etc.), acid amides (e.g. N,N-dimethylformamide, etc.), alcohols (e.g. propanol, butanol, amyl alcohol, ethylene glycol, diethylene glycol, etc.), and their mixtures.

The amount of a nitrogen-containing compound is usually from 0.01 to a solvent amount, preferably from 0.1 to 20 moles, per 1 mole of a carboxylic acid derivative of the formula (2).

The amount of a boron compound is usually from 0.0001 to 5 moles, preferably from 0.001 to 3 moles, in terms of a boron atom, per 1 mole of a carboxylic acid derivative of the formula (2).

The carboxylic acid of the formula (2) is a known compound from WO98/17632, or can be prepared by the method described in this WO publication.

The carboxylic acid of the formula (2) or its salt has geometric isomers due to the presence of a double bond, optical isomers due to the presence of an asymmetric carbon atom and diastereomers. Any one of such isomers or a mixture thereof may be used in the process of the present invention.

In the process of the present invention, the raw material, a solvent and the like can be charged at once, although it is possible to charge a carboxylic acid derivative of the formula (2), a nitrogen-containing compound and the like by several portions to carry out the reaction.

After the completion of the reaction, the reaction mixture is post-treated, for example, the reaction mixture as such is concentrated, or it is washed with an aqueous solution of an inorganic acid such as hydrochloric acid, sulfuric acid, etc. and the organic layer is dried and concentrated. If necessary, the concentrated product may be purified by recrystallization or with column chromatography to recover a pyridazin-3-on of the formula (1).

In the process of the present invention, the reaction may be carried out with azeotropic dehydration and/or in the presence of a dehydrator. Examples of such a dehydrator include zeolites such as molecular sieves, silica gel, magnesium sulfate, sodium sulfate, calcium sulfate, copper sulfate, etc. Preferably zeolites such as molecular sieves, in particular, Molecular Sieve 3A, are used.

When a solid dehydrator is used, it is removed by filtration from a reaction mixture, and then the reaction mixture is subjected to the above post-treatment to recover a pyridazin-3-one of the formula (1).

Preferred but unlimiting examples of pyridazin-3-on derivatives of the formula (1) are as follows:

According to the present invention, pyridazin-3-on derivatives having good herbicidal activities can be obtained at a high yield and high purity.

The present invention will be illustrated by the following examples, which do not limit the scope of the invention in any way.