Method for preparing pyrazolecarboxylic acid derivative, and intermediate thereof

1. A compound of the following formula (II),

wherein,

R 1 is selected from methyl or ethyl;

R 4 is selected from hydrogen or methyl;

n is 1-4;

X is F, Cl or CF 3 .

2. The compound according to claim 1 , wherein R 1 is methyl, R 4 is methyl, n is 1, and X is F.

3. A method for preparing the compound of formula (II), said method comprising the following steps of:

(1) in the presence of Lewis acid, reacting α-fluoride amine of formula (III) with ethylene derivative of formula (IV) to obtain vinamidinium salt of formula (V) (i.e. 1,5-diaza-pentadiene salt),

said α-fluoride amine of formula (III) is as follows:

wherein, X is defined as described previously, R 2 and R 3 are independently selected from C 1 -C 4 alkyl;

said ethylene derivative of formula (IV) is as follows:

wherein, R 4 is hydrogen or methyl, n is 1-4;

said 1,5-diaza-pentadiene salt of formula (V) is as follows:

wherein, n, R 2 , R 3 , and R 4 are defined as described previously, Y − is an anion, said anion is selected from [BF 4 ] − , [AlCl 3 F] − , [AlF 4 ] − , [ZnCl 2 F] − , [SbF 6 ] − , [SnCl 4 F] − , [BiCl 3 F] − , [GaCl 3 F] − and [SiCl 4 F] − , which are derived from the corresponding Lewis acids;

(2) reacting the 1,5-diaza-pentadiene salt of formula (V) with hydrazine to obtain the compound of formula (II).

4. A method for preparing compound of formula (I), said compound of formula (I) is as follows,

wherein, R 1 is methyl or ethyl;

X is F, Cl or CF 3 ;

said method comprising the following steps of:

(1) in the presence of Lewis acid, reacting α-fluoride amine of formula (III) with ethylene derivative of formula (IV) to obtain vinamidinium salt of formula (V) (i.e. 1,5-diaza-pentadiene salt),

said α-fluoride amine of formula (III) is as follows:

wherein, X is defined as described previously, and R 2 and R 3 are independently selected from C 1 -C 4 alkyl;

said ethylene derivative of formula (IV) is as follows:

wherein, R 4 is hydrogen or methyl, and n is 1-4;

said 1,5-diaza-pentadiene salt of formula (V) is as follows:

wherein, n, R 2 , R 3 , and R 4 are defined as described previously, and Y − is an anion, said anion is selected from [BF 4 ] − , [AlCl 3 F] − , [AlF 4 ] − , [ZnCl 2 F] − , [SbF 6 ] − , [SnCl 4 F] − , [BiC 13 F] − , [GaCl 3 F] − and [SiCl 4 F] − ;

(2) reacting the 1,5-diaza-pentadiene salt of formula (V) with hydrazine to obtain the compound of formula (II),

said compound of formula (II) is as follows:

wherein, X, n, R 1 , and R 4 are defined as described previously;

(3)hydrolyzing and oxidizing one of the compounds of formula (II) with n=1-4 to obtain the compound of formula (I).

5. The method according to claim 3 , wherein, the Lewis acid in step (1) is selected from the following compounds: BF 3 , AlCl 3 , AlF 3 , ZnCl 2 , PF 5 , SbF 5 , SnCl 4 , BiCl, GaCl 3 and SiCl 4 with the molar ratio of the Lewis acid and the α-fluoride amine is 1:1 to 10:1.

6. The method according to claim 3 , wherein the reaction temperatures in step (1) and step (2) are around −20° C. to 60° C.

7. The method according to claim 3 , wherein the reaction in step (2) is carried out in the presence of solvent, said solvent is selected from diethyl ether, acetonitrile, methylene chloride and tetrahydrofuran.

8. The method according to claim 3 , wherein, the hydrazine used in step (2) is methylhydrazine or ethylhydrazine.

9. The method according to claim 3 , wherein, the molar ratio of 1,5-diaza-pentadiene salt of formula (V) and hydrazine in step (2) is 1:10 to 10:1.

10. The method according to claim 3 , wherein the hydrolyzing reaction of compound of formula (II) in step (3) is carried out in the presence of solvent, said solvent is selected from mixture of methanol, ethanol, acetonitrile, or tetrahydrofuran, with water or using water alone as a solvent.

11. The method according to claim 3 , wherein the hydrolysis reaction of compound of formula (II) in step (3) is carried out in the presence of acid, said acid is hydrochloric acid, sulfuric acid, hydrobromic acid or phosphoric acid, the molar ratio of compound of formula (II) and acid is 1:2 to 1:10.

12. The method according to claim 3 , wherein the oxidizing agent used in step (3) is selected from hydrogen peroxide, sodium hypochlorite, potassium permanganate, sodium chlorate, potassium chlorate, the temperature of oxidation reaction is around 30° C. to 100° C.

13. The method according to claim 3 , wherein the hydrolysis reaction and the oxidation reaction in step (3) are continuously carried out, the molar ratio of compound of formula (II) and oxidizing agent is 1:2 to 1:10.

14. The method according to claim 5 , wherein the Lewis acid in step (1) is BF 3 , with the molar ratio of the Lewis acid and the α-fluoride amine is 1:1 to 5:1.

15. The method according to claim 5 , wherein the molar ratio of the Lewis acid and the α-fluoride amine in step (1) is 1:1 to 1.3:1.

16. The method according to claim 6 wherein the reaction temperatures in step (1) and step (2) are around −10° C. to 40° C.

17. The method according to claim 6 , wherein the reaction temperatures in step (1) and step (2) are around 0° C. to 30° C.

18. The method according to claim 9 , wherein the molar ratio of 1,5-diaza-pentadiene salt of formula (V) and hydrazine in step (2) is 1:5 to 5:1.

19. The method according to claim 9 , wherein the molar ratio of 1,5-diaza-pentadiene salt of formula (V) and hydrazine in step (2) is 1.3:1 to 1:1.3.

20. The method according to claim 12 , wherein the oxidizing agent used in step (3) is hydrogen peroxide or sodium hypochlorite, and the temperature of oxidation reaction is around 50° C. to 100° C.