Process for preparing aromatic aldehyde compound

1. A process for preparing an aromatic aldehyde compound represented by the formula (2);

wherein R represents a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an alkyloxy group having 1 to 12 carbon atoms, a phenyloxy group, a naphthyloxy group, a benzyloxy group or a phenethyloxy group, each group of which may have a substituent(s); n is an integer of 0 to 5; and when n is 2 or more, Rs may form a ring by combining with each other,

which comprises reacting an aromatic methyl alcohol compound represented by the formula (1);

wherein R and n have the same meanings as defined above,

and a peroxide under a pH value of a reaction solution being pH 0.5 or higher and less than 9, in the presence of at least one metallic compound of a molybdenum compound, and at least one salt selected from a quaternary ammonium salt and an organic phosphonium salt, wherein the aromatic aldehyde compound of the formula (2) is at least one selected from the group consisting of the following formulae (4) to (7):

wherein R 1 and R 2 each represents a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, a phenyl group, a naphthyl group, a benzyl group or a phenethyl group, each group of which may have a substituent(s), and m is 1 or 2.

2. A process for preparing an aromatic aldehyde compound represented by the formula (2);

wherein R represents a halogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an alkyloxy group having 1 to 12 carbon atoms, a phenyloxy group, a naphthyloxy group, a benzyloxy group or a phenethyloxy group, each group of which may have a substituent(s); n is an integer of 0 to 5; and when n is 2 or more, Rs may form a ring by combining with each other,

which comprises reacting an aromatic methyl alcohol compound represented by the formula (1);

wherein R and n have the same meanings as defined above,

and a peroxide while maintaining a pH value of a reaction solution to a pH of 3 or higher and less than 8 in the presence of at least one metallic compound of a tungsten compound, and at least one salt selected from a quaternary ammonium salt and an organic phosphonium salt, wherein the aromatic aldehyde compound of the formula (2) is at least one selected from the group consisting of the following formulae (4) to (7):

wherein R 1 and R 2 each represents a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, an alkyl group having 1 to 12 carbon atoms, a phenyl group, a naphthyl group, a benzyl group or a phenethyl group, each group of which may have a substituent(s), and m is 1 or 2,

wherein the quaternary ammonium salt is at least one selected from the group consisting of tetrabutyl ammonium hydrogen sulfate, tetra-n-hexyl ammonium hydrogen sulfate, tetrabutyl ammonium chloride and tetrabutyl ammonium bromide, and

wherein the organic phosphonium salt is at least one selected from the group consisting of tetrabutylphosphonium chloride, tetrabutylphosphonium bromide, tetraphenylphosphonium chloride and tetraphenylphosphonium bromide.

3. The preparation process according to claim 1 , wherein the reaction is carried out by further adding at least one buffer selected from a phosphoric acid compound, a boric acid compound and a carbonic acid compound.

4. The preparation process according to claim 1 , wherein the metallic compound is a molybdenum compound, and the pH value of the reaction solution is a pH of 0.8 or higher and a pH of less than 9.

5. The preparation process according to claim 2 , wherein the metallic compound is a tungsten compound, and the pH value of the reaction solution is a pH of 4 to 7.5.

6. The preparation process according to claim 1 , wherein the peroxide is hydrogen peroxide.

7. The preparation process according to claim 1 , wherein the aromatic aldehyde compound is a compound represented by the formula (7) where m is 1.

8. The preparation process according to claim 6 , wherein an amount of the hydrogen peroxide to be used is 0.1 to 5 mol based on 1 mol of the aromatic methyl alcohol compound.

9. The preparation process according to claim 1 , wherein an amount of at least one of the metallic compound of the molybdenum compound is 0.0001 to 0.10 mol based on 1 mol of the aromatic methyl alcohol compound.

10. The preparation process according to claim 1 , wherein the molybdenum compound is at least one compound selected from an alkali molybdate compound, molybdenum dioxide, molybdenum trioxide, phosphomolybdic acid, an alkali phosphomolybdate compound, and molybdenum hexacarbonyl.

11. The preparation process according to claim 2 , wherein the tungsten compound is at least one compound selected from an alkali tungstate compound, tungsten trioxide, phosphotungstic acid, an alkali phosphotungstate compound, and tungsten hexacarbonyl.

12. The preparation process according to claim 3 , wherein the phosphoric acid compound is at least one compound selected from phosphoric acid (orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid), sodium phosphate, potassium phosphate, sodium monohydrogen phosphate, sodium dihydrogen phosphate, potassium monohydrogen phosphate, potassium dihydrogen phosphate, and ammonium phosphate.

13. The preparation process according to claim 1 , wherein the pH is adjusted by at least one compound selected from a hydroxide of an alkali metal, a hydroxide of an alkaline earth metal, a carbonate of an alkali metal, a carbonate of an alkaline earth metal, a phosphate of an alkali metal and a phosphate of an alkaline earth metal, phosphoric acid, hydrochloric acid and sulfuric acid.

14. The preparation process according to claim 1 , wherein the reaction is carried out without solvent.

15. The preparation process according to claim 1 , wherein the pH value of the reaction solution is a pH of 1 or higher and a pH of less than 9.

16. The preparation process according to claim 1 , wherein the aromatic aldehyde compound is piperonal and the molybdenum compound is sodium molbdate.

17. The preparation process according to claim 1 , wherein the aromatic aldehyde compound is piperonal and the molybdenum compound is molybdenum hexacarbonyl, molybdenum trioxide or molybdenum dioxide.

18. The preparation process according to claim 2 , wherein the aromatic aldehyde compound is piperonal and the tungsten compound is sodium tungstate.