Method for producing aminothiazole derivative and production intermediate

A production method of a compound represented by formula (2):

• wherein ring A represents a benzene ring or a 6-membered aromatic heterocycle;
• R1 represents a hydrogen atom, a C1-6 alkyl group, a halogen atom, a nitro group, an amino group, a mono-C1-6 alkylamino group, or a di-C1-6 alkylamino group;
• and at least one of R2, R3, and R4 represents a methoxy group, and the rest each represents a hydrogen atom, a C1-6 alkyl group, a halogen atom, a nitro group, an amino group, a mono-C1-6 alkylamino group, or a di-C1-6 alkylamino group,
• the method comprising reacting a compound represented by formula (1):
• wherein ring A and R1, R2, R3, and R4 are the same as defined in formula (2), with a Lewis acid selected from BF3, TiCl4, and AlCl3 in an esteric, a ketonic or an amidic solvent selected from the group consisting of ethyl acetate, methyl acetate, butyl acetate, isobutyl acetate, acetone, 2-butanone, cyclohexanone, cyclopentanone, dimethylformamide, and dimethylacetamide, with the proviso that when the Lewis acid is BF3, an alkali metal bromide or an alkali metal iodide coexists.

A production method of a compound represented by formula (3):

• wherein ring A represents a benzene ring or a 6-membered aromatic heterocycle;
• R1 represents a hydrogen atom, a C1-6 alkyl group, a halogen atom, a nitro group, an amino group, a mono-C1-6 alkylamino group, or a di-C1-6 alkylamino group;
• at least one of R2, R3, and R4 represents a methoxy group, and the rest each represents a hydrogen atom, a C1-6 alkyl group, a halogen atom, a nitro group, an amino group, a mono-C1-6 alkylamino group, or a di-C1-6 alkylamino group;
• and R5 represents a hydrogen atom or a nitro group,
• the method comprising reacting a compound represented by formula (1):
• wherein ring A and R1, R2, R3, and R4 are the same as defined for formula (3), with a Lewis acid selected from the group consisting of BF3, TiCl4, and AlCl3 in an esteric, a ketonic or an amidic solvent selected from the group consisting of ethyl acetate, methyl acetate, butyl acetate, isobutyl acetate, acetone, 2-butanone, cyclohexanone, cyclopentanone, dimethylformamide, and dimethylacetamide, with the proviso that when the Lewis acid is BF3, an alkali metal bromide or an alkali metal iodide coexists, to provide a compound represented by formula (2):
• wherein ring A and R1, R2, R3, and R4 are the same as defined for formula (3), and
• then reacting the resultant compound with a phenol derivative selected from phenol and para-nitrophenol or a triphenyl phosphite derivative selected from triphenyl phosphite and tri-para-nitrophenyl phosphite.