Process for the regioselective preparation of 1-alkyl-3-haloalkylpyrazole-4-carboxylic acid derivatives

1. A process for preparing 1-alkyl-3-haloalkylpyrazole-4-carboxylic acid derivatives of the formula (I)

in which:

R 1 is selected from the group consisting of C 1-12 -alkyl, C 3-8 -cycloalkyl, C 2-12 -alkenyl, C 2-12 -alkynyl, C 6-8 -aryl, C 7-19 -arylalkyl and C 7 -19 -alkylaryl groups, each of which may be substituted by one or more groups selected from the group consisting of —R′, —X, —OR′, —SR′, —NR′ 2 , —SiR′ 3 , —COOR′, —(C═O)R′, —CN and —CONR 2 ′, where R′ is hydrogen or a C 1-12 -alkyl group;

R 2 is selected from C 1 -C 4 -alkyl groups which may be substituted by one, two or three halogen atoms selected from the group consisting of F, Cl and Br or by a CF 3 group;

Y is selected from the group consisting of (C═O)OR 3 , CN and (C═O)NR 4 R 5 , where R 3 , R 4 and R 5 independently of one another are selected from the group consisting of hydrogen, C 1-12 -alkyl, C 3-8 -cycloalkyl, C 2-12 -alkenyl, C 2-12 -alkynyl, C 6-8 -aryl, C 7-19 -arylalkyl and C 7-19 -alkylaryl groups, each of which may be substituted by one or more groups selected from the group consisting of —R′, —X, —OR′, —SR′, —NR′ 2 , —SiR′ 3 , —COOR′, —(C═O)R′, —CN and —CONR 2 ′, where R′ is hydrogen or a C 1-12 -alkyl group;

or where R 4 and R 5 together with the nitrogen atom to which they are attached may form a 5- or 6-membered ring;

comprising reacting a 2-acylated acrylic acid derivative of the formula (II),

in which:

Z 1 and Z 2 independently of one another are selected from the group consisting of O and S;

R 6 is selected from the group consisting of C 1-12 -alkyl, C 3-8 -cycloalkyl, C 2-12 -alkenyl, C 2-12 -alkynyl, C 6-8 -aryl, C 7-19 -arylalkyl and C 7-19 -alkylaryl groups, each of which may be substituted by one or more groups selected from the group consisting of —R′, —X, —OR′, —SR′, —NR′ 2 , —COOR′, —(C═O)R′, —CN and —CONR 2 ′, where R′ is hydrogen or a C 1-12 -alkyl group;

R 2 and Y have the meanings described above;

with an N-alkylhydrazine of the formula (III)

in which:

R 1 has the meaning described above;

in the presence of a compound of the formula (IV)

in which:

R 7 , R 8 independently of one another are selected from the group consisting of H, C 1-12 -alkyl, C 3-8 -cycloalkyl, C 6-18 -aryl, C 7-19 -arylalkyl or C 7-19 -alkylaryl radicals;

M is selected from the group consisting of O, S, Se, NH, and NR′, where R′ has the meanings defined above.

2. The process according to claim 1 , characterized in that the 2-acylated acrylic acid derivative of the formula (II) is selected from the group consisting of ethyl (2-ethoxymethylene)-4,4-difluoromethylacetoacetate, ethyl-(2-ethoxymethylene)-4,4,4-trifluoromethylacetoacetate, and ethyl-(2-ethoxymethylene)-4,4,4-trifluorometbylacetonitrile.

3. The process according to claim 1 , characterized in that the N-alkylhydrazine of the formula (III) is selected from the group consisting of monomethylhydrazine, monoethylhydrazine, and phenylhydrazine.

4. The process according to claim 1 , characterized in that the compound of the formula (IV) is selected from the group consisting of acetone, pinacolone, benzaldehyde, and benzophenone.

5. The process according to claim 1 , characterized in that the acrylic acid derivative of the formula (II) used is ethyl (2-ethoxymethylene)-4,4-difluoromethylacetoacetate, the hydrazine of the formula (III) used is methylhydrazine and the compound of the formula (IV) used is acetone.