Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2002-02-01
2003-02-18
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S441000, C564S124000, C564S129000, C560S070000
Reexamination Certificate
active
06521794
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method for the production of aromatic compounds and more particularly to a method for the production of aromatic compounds by using a halogen-containing aromatic cyano compound as a raw material, performing hydrolysis and decarboxylation on the raw material without inducing corrosion of the reaction vessel to obtain a corresponding aromatic compound aimed at with a high yield.
2. Description of Related Art
The tetrahalogenoanilines include important compounds which are used as intermediate raw materials for pharmaceutical preparations and agricultural pesticides. Methods for producing 2,3,5,6-tetrafluoroaniline are described in the official gazettes of JP-A-06-211,756 and JP-A-08-268,979, for example. The method described in the official gazette of JP-A-06-211,756 is claimed to obtain 2,3,5,6-tetrafluoroaniline by using a pentafluorobenzoic acid as a raw material and causing it to react with ammonia in an aqueous medium and consequently undergo amination and decarboxylation. It is described that the pentafluorobenzoic acid as the raw material can be obtained by hydrolyzing pentafluorobenzonitrile in an aqueous sulfuric acid solution and that though the aqueous reaction solution contains excess sulfuric acid and ammonium sulfate as a reaction product besides the pentafluorobenzoic acid, the obtained pentafluorobenzoic acid can be used directly in its unmodified form without being washed with water in the reaction for the production of 2,3,5,6-tetrafluoroaniline.
Then, the method disclosed in the official gazette of JP-A-08-268,979 is claimed to obtain 2,3,5,6-tetrafluoroaniline by using 4-amino-2,3,5,6-tetrafluorobenzonitrile as a raw material, adding it together with water to an aqueous sulfuric acid solution thereby enabling the 2,3,5,6-tetrafluoroaniline formed consequently by hydrolysis and decarboxylation to be distilled with water by azeotropic distillation and meanwhile causing the reaction of hydrolysis and decarboylation to proceed. Since the hydrofluoric acid which is formed by a secondary reaction corrodes reaction devices made of stainless steel or lined with glass, this method immediately distills the formed 2,3,5,6-tetrafluoroaniline azeotropically with water and feeds water to the reaction vessel for the purpose of keeping the concentration of sulfuric acid therein at a fixed level, with the result that the reaction a vessel is prevented from corrosion and the 2,3,5,6-tetrafluoroaline is obtained in a high yield.
Generally, when a given reaction involves use of sulfuric acid, for example, the reaction vessel for this reaction is made of glass or lined with glass because the vessel would be destined to incur corrosion if it was made of iron or steel. The method disclosed in the aforementioned official gazette of JP-A-08-268,979 is directed at preventing a reaction vessel from corrosion, when the method uses 4-amino-2,3,5,6-tetrafluorobenzonitrile in a low purity as a raw material, however, the vessel undergoes discernible corrosion. When the raw material is subjected to a treatment for removal of impurities in advance, the treatment would be capable of preventing the vessel from corrosion but suffer disadvantage in adding to the number of steps for the process.
In a working example cited in the official gazette of JP-A-08-268,979, the 2,3,5,6-tetrafluoroaniline is reported to be obtained in a yield of 82.5%. Thus, the desirability of further enhancing. the yield finds readily approval.
SUMMARY OF THE INVENTION
The present inventor, as a result of a detailed study on a path of synthesis of an aromatic amino compound obtained by the hydrolysis and decarboxylation of a halogen-containing aromatic cyano compounds and on a secondary product formed in the synthesis, has found that the occurrence of impurities can be repressed, the yield of the product can be enhanced, and the corrosion of a reaction vessel can be prevented by carrying out the reaction of hydrolysis and decarboxylation as divided into two discrete steps in using different conditions. As a result of further continuing a detailed study on the timing for effecting the distillation of the target product from the reaction system, he has discovered that the corrosion of the reaction vessel can be prevented and the target aromatic amino compound can be obtained in a high yield by performing the hydrolysis and decarboxylation in the presence of an aqueous medium thereby effecting formation of the aromatic amino compound and thereafter expelling the aromatic amino compound through azeotropic distillation with water. The present invention has been perfected based on the knowledge thus acquired. Specifically, this invention is aimed at providing the methods stated in the following items (1) to (3).
(1) In the production of an aromatic compound represented by the general formula (2) by hydrolyzing and decarboxylating an aromatic cyano compound represented by the general formula (1) in the presence of an acidic substance, a method for the production of the aromatic compound, characterized by performing the reactions of hydrolysis and decarboylation in multiple steps.
(wherein X is a halogen atom, Y is a cyano group, nitro group, or carboxyl group, Z is a nitrogen-containing group represented by —N(R
1
) (R
2
) (wherein R
1
and R
2
are identical or not identical substitutes superposed on a nitrogen atom and selected from among hydrogen atom and linear or branched alkyl groups of 1 to 4 carbon atoms), m is 0, 1, or 2, and n is 1, 2, 3, or 4, providing that the sum of m and n falls in the range of 1≦m+n≦4.)
(wherein the symbols have the same meanings as in the general formula (1).)
(2) A method for the production of an aromatic compound, characterized by forming an aromatic compound represented by the general formula (2) by hydrolyzing and decarboxylating an aromatic cyano compound represented by the general formula (1) in the presence of an aqueous medium and subsequently recovering the obtained aromatic compound from the reaction solution by azeotropic distillation with water.
(wherein X is a halogen atom, Y is a cyano group, nitro group, or carboxyl group, Z is a nitrogen-containing group represented by —N(R
1
) (R
2
) (wherein R
1
and R
2
are identical or not identical substitutes superposed on a nitrogen atom and selected from among hydrogen atom and linear or branched alkyl groups of 1 to 4 carbon atoms), m is 0, 1, or 2, and n is 1, 2, 3, or 4, providing that the sum of m and n falls in the range of 1≦m+n≦4.)
(wherein the symbols have the same meanings as in the general formula (1).)
(3) In the production of an aromatic compound represented by the general formula (2) by hydrolyzing and decarboxylating an aromatic cyano compound represented by the general formula (1) in the presence of an acidic substance, a method for the production of the aromatic compound, characterized by performing the hydrolysis and decarboxylation in multiple. steps and effecting the recovery of the formed aromatic compound from the reaction solution by azeotropic distillation with water.
(wherein X is a halogen atom, Y is a cyano group, nitro group, or carboxyl group, Z is a nitrogen-containing group represented by —N(R
1
) (R
2
) (wherein R
1
and R
2
are identical or not identical substitutes superposed on a nitrogen atom and selected from among hydrogen atom and linear or branched alkyl groups of 1 to 4 carbon atoms), m is 0, 1, or 2, and n is 1, 2, 3, or 4, providing that the sum of m and n falls in the-range of 1≦m+n≦4.)
(wherein the symbols have the same meanings as in the general formula (1).)
According to the method of this invention, by using a raw material such a halogen-containing aromatic compound as 4-amino-2,3,5,6-tetrahalogenobenzonitrile, it is made possible to produce such a corresponding aromatic compound as 2,3,5,6-tetrahalogenoaniline in a high yield. Even when the 4-amino-2,3,5,6-tetrahalogenobenzonitrile formed in low purity is hydrolyzed, decarboxylated, and azeotropically distilled particula
Barts Samuel
Mathews, Collins Shepherd & McKay, P.A.
Nippon Shokubai Co. , Ltd.
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