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Claims for Patent: 7,553,863

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Claims for Patent: 7,553,863

Title:Ultrapure 4-methylpyrazole
Abstract:Disclosed is an ultrapure 4-methylpyrazole containing less than 0.1% pyrazole and containing less than 10 ppm each of hydrazine and nitrobenzaldehyde. The ultrapure 4-methylpyrazole is prepared by a novel process so that less than 0.01% of ethylvinyl ether is present.
Inventor(s): Reardan; Dayton T. (Shorewood, MN), Combe; Michel D. (Fox Point, WI)
Assignee: Paladin Labs (Barbados) Inc. (Barbados, BB)
Application Number:11/279,708
Patent Claims: 1. A solution containing 4-methyl pyrazole containing less than 0.1% pyrazole.

2. The solution of claim 1 containing less than 10 ppm each of hydrazine and nitrobenzaldehyde.

3. The solution of claim 2, wherein the nitrobenzaldehyde is p-nitrobenzaldehyde.

4. A process of making 4-methylpyrazole containing less than 0.1% pyrazole comprising the steps: (a) reacting propionaldehyde with triethyl orthoformate to produce 1,1-diethoxypropane; (b) reacting the 1,1-diethoxypropane of step (a) with an amine and an acid at a temperature of about 140-160.degree. C. to produce 1-ethoxy-1-propene; (c) washing the 1-ethoxy-1-propene with water and drying it without distillation; (d) reacting the dried 1-ethoxy-1-propene of step (c) with triethyl orthoformate in the presence of a catalytic amount of boron trifluoride-diethyl etherate to produce 1,1,3,3-tetraethoxy-2-methylpropane; and (e) reacting the 1,1,3,3-tetraethoxy-2-methylpropane of step (d) with hydrazine or a hydrazonium salt to produce 4-methylpyrazole containing less than 0.1% pyrazole.

5. A process of making 4-methylpyrazole containing less than 0.1% pyrazole and less than 10 ppm each of hydrazine and nitrobenzaldehyde comprising the steps: (a) reacting propionaldehyde with triethyl orthoformate to produce 1,1-diethoxypropane; (b) reacting the 1,1-diethoxypropane of step (a) with an amine and an acid at a temperature of about 140-160.degree. C. to produce 1-ethoxy-1-propene; (c) washing the 1-ethoxy-1-propene with water and drying it without distillation; (d) reacting the dried 1-ethoxy-1-propene of step (c) with triethyl orthoformate in the presence of a catalytic amount of boron trifluoride-diethyl etherate to produce 1,1,3,3-tetraethoxy-2-methylpropane; and (e) reacting the 1,1,3,3-tetraethoxy-2-methylpropane of step (d) with hydrazine or a hydrazonium salt to produce 4-methylpyrazole containing less than 0.1% pyrazole and less than 10 ppm each of hydrazine and nitrobenzaldehyde.

6. The process of claim 4 or 5 wherein the molar ratio of acid to amine is about 1:0.4-0.6.

7. The process of claim 6 wherein the reaction temperature is about 160.degree. C.

8. The process of claim 4 or 5 wherein the 1-ethoxy-1-propene of step (b) is dried over a drying agent in step (c).

9. The process of claim 8 wherein the drying agent is magnesium sulfate.

10. The process of claim 4 or 5 wherein the dried 1-ethoxy-1-propene of step (c) contains less than 0.01% ethylvinyl ether.

11. The process of claim 10 wherein less than 0.01% ethylvinyl ether is present in the dried 1-ethoxy-1-propene of step (c) as a result of the molar ratio of acid to amine, the reaction temperature, and the washing and drying of the product without distillation.

12. The process of claim 4 or 5 wherein in step (e) a slight molar excess of 1,1,3,3-tetraethoxy-2-methylpropane is used relative to the hydrazine or hydrazonium salt.

13. The process of claim 12 wherein the molar excess is about 0.1% to about 0.5%.

14. The process of any one of claims 4, 5 or 12 wherein a hydrazonium salt is used in step (e).

15. The process of claim 14 wherein the hydrazonium salt is hydrazine hydrosulfate.

16. A composition consisting essentially of 4-methyl pyrazole containing less than 0.1% pyrazole.
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