Processes for the preparation of pesticide compounds
View Patent ↗This application relates to efficient and economical synthetic chemical processes for the preparation of pesticidal thioethers. Further, the present application relates to certain novel compounds useful in the preparation of pesticidal thioethers. Specifically, this application relates to a process for the preparation of 3-chloro-1H-pyrazol-4-amine and salts thereof. More particularly, this application relates to a process for the preparation of 3-chloro-1H-pyrazol-4-amine and salts thereof by halogenating and reducing 4-nitropyrazole.
1. A process for the preparation of 3-chloro-1H-pyrazol-4-amine hydrochloride (1a)
comprising halogenating and reducing 4-nitropyrazole
with
(a) about 17% to about 40% hydrochloric acid,
(b) hydrogen gas at pressures of about 100 kPa to about 800 kPa, and
(c) a transition metal catalyst selected from the group consisting of palladium on alumina (Pd/Al 2 O 3 ), palladium on carbon (Pd/C), platinum on carbon (Pt/C), and mixtures thereof,
at temperatures of about 20° C. to about 60° C., optionally in the presence of an alcoholic solvent at a v/v ratio of alcoholic solvent to hydrochloric acid of about 1:99 to about 3:4.
2. The process according to claim 1 , wherein the transition metal catalyst is palladium on alumina.
3. The process according to claim 1 , wherein the transition metal catalyst is palladium on carbon.
4. The process according to claim 1 , comprising about 36% to about 38% hydrochloric acid.
5. The process according to claim 1 , wherein the temperature is about 20° C. to about 40° C.
6. The process according to claim 1 , wherein the v/v ratio of alcoholic solvent to hydrochloric acid is about 1:9 to about 3:4.
7. The process according to claim 1 , wherein the transition metal catalyst is platinum on carbon.
8. The process according to claim 7 , wherein the hydrochloric acid is about 17% to about 22% v/v.
9. The process according to claim 8 , wherein the v/v ratio of alcoholic solvent to hydrochloric acid is about 1:9 to about 3:4.
10. The process according to claim 9 , wherein the v/v ratio of alcoholic solvent to hydrochloric acid is about 1:9.
11. The process according to claim 7 , wherein the hydrochloric acid is about 17% to about 27% v/v.
12. The process according to claim 11 , wherein the v/v ratio of alcoholic solvent to hydrochloric acid is about 1:9 to about 3:4.
13. The process according to claim 12 , wherein the v/v ratio of alcoholic solvent to hydrochloric acid is about 1:9.
14. A process according to claim 1 , further comprising free-basing 3-chloro-1H-pyrazol-4-amine hydrochloride (1a)
with a base to yield 3-chloro-1H-pyrazol-4-amine (1)
15. A process according to claim 1 , wherein the palladium on alumina has a metal to solid support weight percentage of about 1 weight percent to about 10 weight percent.
16. A process according to claim 1 , wherein the platinum on carbon has a metal to solid support weight percentage of about 1 weight percent to about 10 weight percent.
17. The process according to claim 1 , wherein the alcoholic solvent is ethanol.
18. The process according to claim 1 , wherein the alcoholic solvent is isopropanol.
19. The process according to claim 1 , wherein the process is performed in a glass-lined reactor.