Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2002-02-05
2004-02-03
Rotman, Alan L. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S512000
Reexamination Certificate
active
06686501
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to processes for preparing 3,3-dimethylbutyric acid. More particularly, this invention relates to processes for preparing 3,3-dimethylbutyric acid by reacting trimethylpyruvic acid with hydrazine to obtain an intermediate, and treating the intermediate with hydrazine and base. This invention also relates to processes for preparing a ketazine of trimethylpyruvic acid.
BACKGROUND OF THE INVENTION
3,3-Dimethylbutyric acid (DMBA), also called 3,3-dimethylbutanoic acid or tert-butylacetic acid, may be used as an intermediate in the synthesis of other chemical compounds, such as pharmaceutical chemicals or agricultural chemicals. The ketazine prepared using trimethylpyruvic acid (TMPA), also called 3,3-dimethyl-2-oxobutyric acid, may also be used as an intermediate in the synthesis of other chemical compounds. Agricultural chemicals include insecticidally, fungicidally and/or herbicidally active compounds.
3,3-Dimethylbutyric acid may be prepared by reacting tert-butanol or tert-butyl chloride with vinylidene chloride in the presence of sulfuric acid and BF
3
.
Stelzer, U.S. Pat. No. 5,907,060, discloses a process for preparing 3,3-dimethylbutyric acid by reacting trimethylpyruvic acid with hydrazine hydrate to obtain a hydrazone, and subsequently treating the hydrazone with a base.
Unfortunately, BF
3
can be difficult to handle. Additionally, prior art processes for preparing 3,3-dimethylbutyric acid may result in 3,3-dimethylbutyric acid which is contaminated with other organic acids which must be removed by solvent extraction and recovery from the solvent. For example, commercially available TMPA typically contains about 10%, by weight, pivalic acid and from about 0 to about 5%, by weight, 2-hydroxy-3,3-dimethylbutyric acid, and thus in many prior art processes using TMPA the resulting DMBA contains comparable levels of pivalic acid and, 2-hydroxy-3,3-dimethylbutyric acid.
Thus there is a need for methods of preparing 3,3-dimethylbutyric acid wherein the level of other organic acids in the product is decreased. There is also a need for methods of preparing 3,3-dimethylbutyric acid which do not require the use of BF
3
.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to obviate problems of the prior art.
It is also an object of the present invention to provide methods of preparing 3,3-dimethylbutyric acid wherein the level of other organic acids in the product are decreased.
It is a further object of the present invention to provide methods of preparing 3,3-dimethylbutyric acid which do not require the use of BF
3
.
These and additional objects are provided by the processes of the invention. In one embodiment, the invention is directed to processes for preparing 3,3-dimethylbutyric acid comprising the steps of reacting trimethylpyruvic acid with a first portion of hydrazine to obtain a ketazine, and treating the ketazine with base and a second portion of hydrazine.
In another embodiment, the invention is directed to processes for preparing 3,3-dimethylbutyric acid comprising the steps of reacting trimethylpyruvic acid with hydrazine to obtain a ketazine, isolating the ketazine, and treating the ketazine with hydrazine and base.
In a further embodiment, the invention is directed to processes for preparing 3,3-dimethylbutyric acid comprising the steps of treating a composition comprising water and trimethylpyruvic acid with hydrazine to obtain an intermediate, wherein less than one mole of hydrazine is used per mole of trimethylpyruvic acid, and treating the intermediate with hydrazine and base.
In yet another embodiment, the invention is directed to processes a ketazine comprising the step of reacting trimethylpyruvic acid with hydrazine to obtain the ketazine.
The processes of the invention of the invention are advantageous in that the 3,3-dimethylbutyric acid may be prepared in the absence of BF
3
.
Processes in accordance with the invention may be used to prepare 3,3-dimethylbutyric acid without producing large amounts of other organic acids. Thus, processes in accordance with the present invention avoid the need for additional steps directed to removal of other organic acids.
Further, as the ketazine intermediate may be isolated and dried prior to treatment with hydrazine and base, processes in accordance with the present invention do not require large amounts of water be removed.
These and additional aspects, objects and advantages of the invention are more fully described in the following detailed description.
DETAILED DESCRIPTION
The present invention is directed to process from preparing 3,3-dimethylbutyric acid and the ketazine of trimethylpyruvic acid.
As used herein, “hydrazine ” is intended to refer to anhydrous hydrazine, hydrazine hydrate, hydrazine hydrochloride, hydrazine sulfate and hydrazine tartrate. Preferably the hydrazine is hydrazine hydrate.
In one embodiment of the invention, a ketazine is prepared by reacting trimethylpyruvic acid (TMPA) with hydrazine, while in another embodiment of the invention, 3,3-dimethylbutyric acid (DMBA) is prepared by reacting trimethylpyruvic acid with hydrazine to obtain a ketazine and subsequently treating the ketazine with base and hydrazine.
In one embodiment of the invention, 3,3-dimethylbutyric acid (DMBA) is prepared by reacting trimethylpyruvic acid with hydrazine to obtain a ketazine, isolating the ketazine, and subsequently treating the ketazine with base and hydrazine. Hydrazines such a hydrazine hydrate contain water, and TMPA may be in the form of an aqueous composition comprising water and a TMPA salt, thus the TMPA and hydrazine reaction mixture may include water. The isolation of the ketazine prior to treatment with base and additional hydrazine removes the organic impurities and a large amount of water that would otherwise have to be removed from the final DBMA product. Some water is typically present or formed during the treatment of the ketazine with the base and additional hydrazine to obtain the DMBA, but the amount of water to be removed from the final DBMA product is reduced by the step of isolating the ketazine prior to the treatment with base. Thus, in contrast with many prior art processes, processes in accordance with the present invention wherein the ketazine is isolated before treatment with base and hydrazine do not require the removal of large amounts of water from the final DBMA product.
While not being bound by theory, the process of preparing the DMBA is believed to occur as set forth below:
The TMPA may be free of water, or may be in the form of an aqueous composition comprising water and a TMPA salt. Suitable TMPA salts include alkali metal salts, such as TMPA sodium salt. In one embodiment the TMAP is in the form of an aqueous composition comprising from about 7% to about 8%, by weight, TMPA sodium salt.
“Free TMPA”, that is, TMPA which is not in the form of a salt, may be obtained by adding an acid, typically an inorganic acid, in order to convert the TMPA salt, such as TMPA sodium salt, to free TMPA. Suitable acids include HCl, H
2
SO
4
, and H
3
PO
4
. If free TMPA rather than TMPA salt is used in the process, no acid is required.
The process of preparing the ketazine of TMPA (TMPA ketazine) includes the step of treating TMPA with hydrazine, preferably hydrazine hydrate. Typically one mole of TMPA is reacted with less than one mole of hydrazine. In one embodiment of the invention the molar ratio of TMPA to hydrazine is from about 1:0.5 to about 1:1, preferably from about 1:0.5 to about 1:0.8, more preferably about 1:0.5 to about 1:07, even more preferably about 1:0.5. In other embodiments the molar ratio of TMPA to hydrazine is from about 1:0.6 to about 1:1, from about 1:0.8 to about 1:1, or from about 1:0.6 to about 1:0.7.
Generally the step of preparing the TMPA ketazine occurs at a pH of from about 0.1 to about 3. In embodiments of the invention the step of preparing the TMPA ketazine may occur at a pH of from about 0.1 to about 1, or from about 0.5 to about 3. The pH of the aqueous composition may be adjust
Bayer Corporation
Gil Joseph C.
Henderson Richard E.L.
Oh Taylor V
Rotman Alan L.
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