Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acid esters
Reexamination Certificate
2001-01-16
2003-05-27
Chang, Ceila (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acid esters
Reexamination Certificate
active
06570035
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for producing a pivaloylacetic acid ester which is useful as a synthetic intermediate of, for example, photographic photosensitive materials.
BACKGROUND OF THE INVENTION
There have been known a number of processes for producing aliphatic &bgr;-ketoesters. Among these processes, cross-Claisen condensation described in, for example, C. R. Hauser et al., Organic Reactions, 1, 266 (1942) is known as a process for producing a pivaloylacetic acid ester. Although this process has an advantage that the production can be carried out by using a relatively inexpensive pivalic acid ester and an acetic acid ester as the starting materials, it is required therein to use at least one equivalent of a relatively expensive strong base (for example, sodium hydride). Therefore, this process is not always advantageous from an economical viewpoint.
Also, a process for producing a pivaloylacetic acid ester by reacting pinacolone with a carbonic acid diester at a stoichiometric ratio in the presence of an excessive amount of a metal alcholate is described in, for example, WO9855438A1, JP-A-9-110793, JP-A-9-40612, JP-A-7-215915, JP-A-6-279363, JP-A-6-279362, JP-A-6-271504, German Patent No. 2945604, German Patent No. 2412784, JP-A-6-279362 and JP-A-6-279363 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”). Also, there is known a process for producing a pivaloylacetic acid diester by reacting pinacolone with an oxalic acid diester (JP-B-62-47170, JP-B-63-12464, German Patent No. 2945604, JP-A-8-27065, European Patent No. 693473; the term “JP-B” as used herein means an “examined Japanese patent publication”). However, these processes are not economically advantageous too, since it is required therein to use expensive solvents or relatively expensive pinacolone.
Furthermore, there are known a process for producing a pivaloylacetic acid ester by reacting pivaloyl chloride with an acetoacetic acid ester in the presence of magnesium hydroxide (JP-A-10-25269) and a process for producing a pivaloylacetic acid ester by reacting pivaloyl chloride with an acetoacetic acid ester in the presence of a magnesium alkoxide (East German Patent DD235636A1) However, these processes are not advantageous from both of the viewpoints of economy and operation, since the acetoacetic acid ester should be used in a large amount and, moreover, magnesium hydroxide should be used at least 50% by mol (being equivalent or more) based on the pivaloyl chloride. In addition, these processes suffer from an additional problem of the formation of much wastes.
Furthermore, there is known a process for producing a pivaloylacetic acid ester by reacting magnesium enolate of an acetoacetic acid ester with pivaloyl chloride in the presence of a tertiary amine and then deacetylating the resulting product (JP-A-4-264054, European Patent No. 481395A2). However, this process suffers from a problem that a magnesium compound is used in a stoichiometric amount or more and thus a large amount of magnesium waste is formed. In addition, it is stated in JP-A-10-25269 that no pivaloylacetic acid ester can be obtained by this process.
Pivaloylacetic acid esters are important starting compounds for producing photographic photosensitive materials in particular, yellow couplers to be used as photographic photosensitive materials. With the recent cost reduction in photographic photosensitive materials, it has been required to establish a process for economically producing pivaloylacetic acid esters. At the same time, pivaloylacetic acid esters to be used as the starting compounds for producing yellow couplers employed as photographic photosensitive materials should have high purity. However, pivaloylacetic acid esters produced by the conventional methods as described above by, for example, reacting an acetoacetic acid ester with an equimolar amount of magnesium methoxide and reacting the thus obtained magnesium enolate of the acetoacetic acid ester with pivaloyl chloride followed by alcoholysis or hydrolysis generally have only insufficient purity and, therefore, cannot be used in yellow couplers as photographic photosensitive materials.
M. W. Rathke et al. reported a process for synthesizing ethyl pivaloylacetoacetate, which is a precursor of ethyl pivaloylacetate, by reacting pivaloyl chloride with ethyl acetoacetate in the presence of anhydrous magnesium chloride in an equimolar amount to the pivaloyl chloride and twice by mole as much pyridine. However, this method of Rathke et al. is not economically advantageous, since expensive anhydrous magnesium chloride should be used in the equimolar amount to pivaloyl chloride. In this process, moreover, magnesium chloride employed in a large amount is not dissolved in a solvent, which makes stirring difficult and worsens the operating characteristics. In addition, a large amount of magnesium chloride remains as a waste after the completion of the reaction, which brings about a problem of environmental pollution and makes it necessary to carry out troublesome operations for treating the waste. In case where a pivaloylacetic acid ester is produced by preparing a pivaloylacetoacetic acid ester and then alcoholyzing the same in accordance with the method of Rathke et al., furthermore, the target pivaloylacetic acid ester cannot be always obtained at a high yield.
SUMMARY OF THE INVENTION
An object of the invention is to provide a process for producing a highly pure pivaloylacetic acid ester which is efficiently usable in, for example, a photographic photosensitive material at a low cost while achieving favorable operating characteristics.
Another object of the invention is to provide a process for producing a highly pure pivaloylacetic acid ester at a high yield and a high productivity.
To achieve the objects as described above, the inventors have conducted intensive studies. As a result, they have found out that in case of producing a pivaloylacetic acid ester by reacting pivaloyl chloride with an acetoacetic acid ester and then alcoholyzing or alkali-hydrolyzing the thus obtained pivaloylacetoacetic acid ester, a pivaloylacetic acid ester, which has a high purity and is little contaminated by by-products and, therefore, usable as a starting material for producing a yellow coupler employed as a photographic photosensitive material merely by distilling, can be obtained by reacting pivaloyl chloride with an acetoacetic acid ester in the presence of an aromatic nitrogen-containing basic compound such as a pyridine derivative and a small amount (0.5 mole equivalent or less based on the pivaloyl chloride) of a magnesium compound. The inventors have further found out that, since a magnesium compound is used only in a small amount (0.5 mole equivalent or less), the magnesium compound can be easily dispersed in a reaction medium and thus favorable operating characteristics (for example, in stirring) can be achieved; and that only a small amount of the magnesium compound is discharged as a waste after the completion of the reaction and thus can be easily treated, which is desirable from the viewpoint of preventing environmental pollution too. The inventors have furthermore found out that the production cost of the pivaloylacetic acid ester can be lowered in this process, since a relatively expensive magnesium compound (for example, anhydrous magnesium chloride) is employed only in a small amount therein. Moreover, the inventors have found out that in case where anhydrous magnesium chloride and/or anhydrous magnesium bromide (in particular, anhydrous magnesium chloride) is used as the magnesium compound in this process, a highly pure pivaloylacetic acid ester can be obtained at an extremely high yield. The invention has been completed based on these findings.
Accordingly, the invention provides a process for producing a pivaloylacetic acid ester which comprises reacting pivaloyl chloride represented by the following chemical formula (I):
with an acetoacetic acid ester represented by the following general formula (II):
wherei
Hagiwara Toshimitsu
Harada Shun'ichi
Ishiguro Kouji
Okeda Yoshiki
Tachikawa Akio
Chang Ceila
Oh Taylor V.
Takasago International Corporation
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