Catalytic hydrogenation process for preparing pyrazoles

Patent metadata

Field	Value
Publication number	US-10975036-B2
Application number	US-201716074537-A
Country	US
Kind code	B2
Filing date	Jan 25, 2017
Priority date	Feb 2, 2016
Publication date	Apr 13, 2021
Grant date	Apr 13, 2021

Abstract

The present invention relates to a catalytic process for preparing pyrazoles of formula V comprising the step of cyclizing hydrazone substituted α,β-unsaturated carbonyl compounds by reacting them with hydrogen in a reaction mixture comprising as components (a) a hydrogenation catalyst, (b) an acid selected from Brønsted acids, ammonium salts of Brønsted acids, and Lewis acids, (c) a protic solvent, and optionally (d) an aprotic solvent.

First claim

The invention claimed is:

1. A process for preparing a pyrazole compound of formula V, or a salt, stereoisomer, tautomer or N-oxide thereof

comprising the step of cyclizing a hydrazone substituted α,β-unsaturated carbonyl compound of formula IV

by reacting it with hydrogen,
wherein the compound of formula IV is provided in a reaction mixture comprising as components:
(a) a hydrogenation catalyst;
(b) an acid selected from Brønsted acids, ammonium salts of Brønsted acids, and Lewis acids;
(c) a protic solvent; and optionally
(d) an aprotic solvent;

and wherein
R 1 is C(O)OR c , wherein R c is C 1 -C 4 -alkyl or benzyl;
R 2 is CH 3 , or fluoromethyl;
R 3 is H;
R 4 is selected from C 1 -C 4 -alkyl, which group is unsubstituted, or partially halogenated, and
R 5 is selected from C 1 -C 4 -alkyl.

2. The process of claim 1 , wherein R 2 is CH 3 ; and R 5 is CH 3 .

3. The process of claim 1 , wherein R 1 is C(O)OCH 2 CH 3 ; R 2 is CH 3 ; R 4 is CH(CH 3 ) 2 ; and R 5 is CH 3 .

4. The process of claim 1 , wherein the hydrogenation catalyst comprises palladium or platinum.

5. The process of claim 4 , wherein the hydrogenation catalyst is Pt/C.

6. The process of claim 1 , wherein the hydrogenation catalyst is present in the reaction mixture in an amount of at least 0.05 mol % based on the molar amount of the compound of formula IV.

7. The process of claim 1 , wherein the acid is selected from the group consisting of H 2 SO 4 , methylsulfonic acid, trifluoroacetic acid, trichloroacetic acid, H 3 PO 4 , and AlCl 3 .

8. The process of claim 1 , wherein the protic solvent is selected from the group consisting of C 1 -C 4 -alkanols, C 2 -C 4 -alkandiols, water, acetic acid, formic acid, and mixtures thereof.

9. The process of claim 1 , wherein the protic solvent is selected from the group consisting of methanol and ethanol, and mixtures thereof.

10. The process of claim 1 , wherein the aprotic solvent is selected from the group consisting of aromatic solvents, alkane solvents, ether solvents, ester solvents, and mixtures thereof.

11. The process according of claim 1 , wherein the compound of formula IV is present in the reaction mixture in an amount of at most 50 wt.-%, based on the total weight of the reaction mixture.

12. The process of claim 1 , wherein the reaction with hydrogen is performed at a temperature of from 0° C. to 40° C.

13. The process of claim 1 , wherein hydrogen is provided with a pressure of from 5 to 80 bar.

14. The process of claim 1 , wherein a solution of compound of formula IV, wherein the solvent is selected from the group consisting of C 1 -C 4 -alkanols, C 2 -C 4 -alkandiols, water, acetic acid, formic acid, and mixtures thereof, is dosed to the reaction mixture comprising components a), b), c), and optionally d) wherein component a) is Pt/C, b) is H 2 SO 4 , c) is MeOH, and d) is, if present, toluene, MTBE, or EtOAc.

15. The process of claim 1 , wherein the process further comprises the step of preparing the hydrazone substituted α,β-unsaturated carbonyl compound of formula IV

by reacting an α,β-unsaturated carbonyl compound of formula III

with a hydrazone compound of formula II

wherein
X is halogen, OH, C 1 -C 10 -alkoxy, C 3 -C 10 -cycloalkoxy, C 1 -C 10 -alkyl-S(O) 2 O—, C 1 -C 10 -haloalkyl-S(O) 2 O—, phenyl-S(O) 2 O—, tolyl-S(O) 2 O—, (C 1 -C 10 -alkyloxy) 2 P(O)O—, C 1 -C 10 -cycloalkylthio, C 1 -C 10 -alkyl-C(O)S—, NH 2 , C 1 -C 10 -alkylamino, C 1 -C 10 -dialkylamino, morpholino, N-methylpiperazino, or aza-C 3 -C 10 -cycloalkyl;
and R 1 , R 2 , R 3 , R 4 , and R 5 are defined as in claim 1 .

16. The process of claim 15 , wherein X is OCH 2 CH 3 .

17. The process of claim 15 , wherein the step of preparing the pyrazole compound of formula V and the step of preparing the compound of formula IV are performed in a one-pot procedure, wherein the compound of formula IV is subjected to the cyclization reaction without previous purification.

18. The process of claim 15 , wherein
(i) if the step of preparing the compound of formula IV is performed in a protic solvent or in a solvent mixture comprising a protic solvent and an aprotic solvent, the step of preparing the pyrazole compound of formula V is performed in the same solvent or solvent mixture as used in the step of preparing the compound of formula IV; or
(ii) if the step of preparing the compound of formula IV is performed in an aprotic solvent, the aprotic solvent is replaced by a protic solvent, or a protic solvent is added before the step of preparing the pyrazole compound of formula V.

19. A process for preparing a compound of formula VIII

comprising the steps of:
cyclizing a hydrazone substituted α,β-unsaturated carbonyl compound of formula IV

by reacting it with hydrogen to form a compound of formula V

wherein the compound of formula IV is provided in a reaction mixture comprising as components:
(a) a hydrogenation catalyst;
(b) an acid selected from Bronsted acids, ammonium salts of Bronsted acids, and Lewis acids;
(c) a protic solvent; and optionally
(d) an aprotic solvent;
wherein
R 1 is C(O)OR c or CN, wherein Rc is C 1 -C 4 -alkyl or benzyl;
R 2 is CH 3 , or fluoromethyl;
R 3 is H;
R 4 is selected from C 1 -C 4 -alkyl, which group is unsubstituted, or partially halogenated, and
R 5 is selected from C 1 -C 4 -alkyl; and
wherein the compound of formula V is a compound of formula Va or Vb

converting the compound of formula Va or Vb into a compound of formula Vc

wherein
R 2 is CH 3 , or fluoromethyl;
R 3 is H;
R 4 is selected from C 1 -C 4 -alkyl, which group is unsubstituted, or partially halogenated, and
R 5 is selected from C 1 -C 4 -alkyl;
converting the compound of formula Vc into a compound of formula VI

wherein X 1 is leaving group selected from halogen, N 3 , p-nitrophenoxy, and pentafluorophenoxy,
and wherein
R 2 is CH 3 , or fluoromethyl;
R 3 is H;
R 4 is selected from C 1 -C 4 -alkyl, which group is unsubstituted, or partially halogenated, and
R 5 is selected from C 1 -C 4 -alkyl;
and,
converting the

Assignees

• Basf Se

Inventors

• Klauber Eric George
• Rack Michael
• Soergel Sebastian
• Gockel Birgit
• Goetz Roland

Classifications

• C07C249/16

  of hydrazones · CPC title

• C07D403/12

  linked by a chain containing hetero atoms as chain links · CPC title

• B01J23/42

  Platinum · CPC title

• C07D401/12

  linked by a chain containing hetero atoms as chain links · CPC title

• B01J21/18

  Carbon · CPC title