Method of producing benzamide derivatives

A process for preparing a selectively monoacylated phenylenediamine derivative which comprises the steps of converting, into a benzoylimidazole derivative, a benzoic acid derivative represented by the formula (1)

• wherein R1 and R2 are each independently a hydrogen atom, or a substituent selected from the group consisting of a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an acyl group having 1 to 4 carbon atoms, an acylamino group having 1 to 4 carbon atoms, an alkylthio group having 1 to 4 carbon atoms, a perfluoroalkyl group having 1 to 4 carbon atoms, a perfluoroalkyloxy group having 1 to 4 carbon atoms and an alkoxycarbonyl group having 1 to 4 carbon atoms, which substituent is located at an optional position on the benzene ring;
• and R3 is a hydrogen atom or a substituent which is located at the other optional position than R1 and R2 and is represented by the formula (2)
• A—X—Q—(CH2)n— (2)
• wherein A is a phenyl group or a heterocyclic ring which may be substituted by 1 to 4 groups selected from the group consisting of a halogen atom, a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an acyl group having 1 to 4 carbon atoms, an acylamino group having 1 to 4 carbon atoms, an alkylthio group having 1 to 4 carbon atoms, a perfluoroalkyl group having 1 to 4 carbon atoms, a perfluoroalkyloxy group having 1 to 4 carbon atoms or an alkoxycarbonyl group having 1 to 4 carbon atoms, a phenyl group and a heterocyclic ring;
• X is a direct bond or one of structures represented by the formulae (3-1) to (3-7):
• wherein e is an integer of 1 to 4;
• m is an integer of 0 to 4;
• R4 is an alkyl group having 1 to 4 carbon atoms which may be substituted or an acyl group represented by the formula (4)
• wherein
• R6 an alkyl group having 1 to 4 carbon atoms, a perfluoroalkyl group having 1 to 4 carbon atoms, a phenyl group or a heterocyclic ring which may be substituted;
• R5 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may be substituted;
• Q is a substituent represented by one of the formulae (5-1) to (5-9)
• wherein R7 is an alkyl group having 1 to 4 carbon atoms which may be substituted, or an acyl group represented by the formula (6)
• wherein
• R6 is as defined above;
• R8 and R9 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms which may be substituted;
• and n is an integer of 0 to 4,
• and then reacting the benzoylimidazole derivative with a phenylenediamine derivative represented by the formula (7)
• wherein R10 is a hydrogen atom, or a halogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an acyl group having 1 to 4 carbon atoms, an acylamino group having 1 to 4 carbon atoms, an alkylthio group having 1 to 4 carbon atoms, a perfluoroalkyl group having 1 to 4 carbon atoms, a perfluoroalkyloxy group having 1 to 4 carbon atoms or an alkoxycarbonyl group having 1 to 4 carbon atoms which can substitute at an optional position on a benzene ring, and one of the amino groups can substitute at a remaining optional position on the benzene ring.