Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2000-03-15
2001-03-06
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
Reexamination Certificate
active
06198001
ABSTRACT:
TECHNICAL FIELD
The present invention relates to methods for preparing 4-nitrosoaniline and, more particularly, relates to a method of selectively preparing 4-nitrosoaniline wherein urea is reacted with nitrobenzene in a polar organic solvent in the presence of a base.
BACKGROUND ART
4-Nitrosoaniline is used in some applications, such as an intermediate for the preparation of dyestuffs or for the preparation of a hair dye, and as a light stabilizer. However, it had not been greatly studied in its applications, due to a difficulty in its preparation.
It is known to prepare 4-nitrosoaniline by synthesizing N-nitrosoaniline from aniline and sodium nitrite (NaNo
2
) and subsequent Fischer-Hepp rearrangement (Tetrahedron, 1975, 31, 1343-9, and U.S. Pat. No. 3,338,966). This method is disadvantageous because a denitrososation occurs during the Fischer-Hepp rearrangement, and waste containing nitroso (NO) compounds harmful to the environment can be generated in great quantities.
It is also known to prepare 4-nitrosoaniline by reaction of p-nitrosophenol and ammonia or ammonium chloride (J. Chem. Soc., 1955, 2049). This method is disadvantageous because the yield of 4-nitrosoaniline is too low.
Recently, it is found that 4-nitrodiphenylamine (4-NDPA), a precursor of 4-aminodiphenylamine which is utilized for the preparation for antiozonants for rubber, is produced by reacting aniline and nitrobenzene in the presence of a base via a nucleophilic aromatic substitution for hydrogen (NASH). Compared with other methods for preparing 4-NDPA, the NASH process provides dramatic reductions (90% or more) in generated chemical waste and wastewater, eliminates the use of an environmentally unfavorable chemical (chlorine), and improves process safety. In addition, this method is advantageous in that a process for separating 4-chloronitrobenzene from an isomer mixture is not required, and also the purity of a final product is extremely high.
Among reactions of using the NASH, it is well-known to prepare 4-NDPA and 4-nitrosodiphenylamine (4-NODPA) by a direct reaction of aniline with nitrobenzene in the presence of tetramethylammonium hydroxide (TMA(OH)). See, J. Am. Chem. Soc., 1992, 114(23), 9237-8; U.S. Pat. No. 5,117,063; U.S. Pat. No. 5,253,737; U.S. Pat. No. 5,331,099; U.S. Pat. No. 5,453,541; U.S. Pat. No. 5,552,531; and U.S. Pat. No. 5,633,407.
It is reported that the ratio of 4-NDPA and 4-NODPA produced in the reaction can be controlled by the molar ratio of aniline to nitrobenzene. For example, where a molar ratio of aniline to nitrobenzene is about 1, yield of 4-NODPA and 4-NDPA are shown to be 15 mole % and 80 mole %, respectively. On the other hand, where a molar ratio of aniline to nitrobenzene is about 50, 4-NODPA and 4-NDPA are obtained in yields of 86 mole % and 9 mole %. The selectivity to final products is known to be dependent on whether a hydride ion (H
−
) of an intermediate product formed from aniline and nitrobenzene is leaving via an intramolecular reaction or an intermolecular reaction.
It is also known to prepare 4-nitroaniline from nitrobenzene and benzamide in the NASH reaction. This is carried out by a two step reaction consisting of synthesizing N-(4-nitrophenyl)benzamide as a stable intermediate, and then adding water(or ammonia) to decompose the product into 4-nitroaniline and benzoic acid (or benzamide). See, J. Am. Chem. Soc., 1992, 114(23); J. Org. Chem., 1993, 58, 6883-6888; U.S. Pat. No. 5,436,371; U.S. Pat. No. 5,380,946; and PCT publication WO 93/24447. In the reaction, the yield of N-(4-nitrophenyl)benzamide is about 98% when moisture was completely removed, whereas the yield of N-(4-nitrophenyl)benzamide is only about 20% when prepared under an oxygen atmosphere without removal of moisture. From these results, it was shown that making a moisture-free reaction condition was particularly important. Moreover, this reaction was reported to produce 4-nitroaniline without referring to the production of 4-nitrosoaniline.
Meanwhile, 4-nitrosoaniline is subjected to a hydrogenation process to produce p-phenylenediamine (PPD). PPD is broadly used as a raw material for cosmetics and antioxidants, and additives to fuel, and also has a great utility in a dye application due to its property of being capable of being easily oxidized to form a colorant. Also, PPD has the greatest utility for manufacturing aramid as a functional fiber that has high chemical resistance, high thermal resistance and high strength, as well as for producing phenylene diisocyanate that is a raw material for polyurethane.
SUMMARY OF THE INVENTION
Diligent efforts have been made to find an improved method for preparing 4-nitrosoaniline, as compared with the prior methods' problem. Such as when a nitroso compound hazardous to the environment is produced as a byproduct after the reaction, a reaction is very difficult to produce, and also the yield of 4-nitrosoaniline is low. As a result, it is found that a direct reaction of urea with nitrobenzene in the presence of a base could produce 4-nitrosoaniline, and it is also found that, when using an alkali metal or an alkaline earth metal as the base and appropriately controlling the amount of urea and nitrobenzene used, 4-nitrosoaniline could be produced in a high yield and selectivity, whereby the present invention was achieved.
The present invention is advantageous in that 4-nitrosoaniline can be produced in high yield with little or no ortho compounds, such as 2-nitroaniline and 2-nitrosoaniline, and hydrogenated to PPD with high purity. Moreover, the present invention is useful in that a reaction is not influenced by moisture content to a great degree, and it is not necessary to make a reaction condition moisture-free. Additionally, the method has an advantage because a two step reaction, in which an intermediate is formed and then decomposed, is not performed, such that the reaction can be achieved in one reactor in a short period of time.
DETAILED DESCRIPTION OF THE INVENTION
The foregoing and other objects, features and advantages of the invention will be apparent to those skilled in the art to which the present invention relates from reading the following specification.
The present invention relates to a method of preparing 4-nitrosoaniline from urea and nitrobenzene in a polar organic solvent in the presence of a general base.
The present invention applies the NASH reaction to producing selectively 4-nitrosoaniline under mild conditions as compared with those of the prior method, by reacting urea with nitrobenzene in the presence of a cheap alkali metal base.
Urea, that can easily lose a proton in the presence of a base, is excellent in a reactivity with nitrobenzene, and is not substantially influenced by moisture content. Moreover, a product of urea and nitrobenzene is unstable, such that it is easily decomposed into 4-nitroaniline and 4-nitrosoaniline by moisture generated during a reaction. This allows the reaction time and the process time to be shortened.
In accordance with the present invention, an appropriate control of a molar ratio of nitrobenzene/urea can play a critical role in a selectivity to a final product. Where a molar ratio of nitrobenzene/urea is in excess of 1, main products are mainly 4-nitroaniline and 4,4′-dinitrodiphenylamine (hereinafter, called “DNDPA”). However, where a molar ratio of nitrobenzene/urea is less than 1, a main product is 4-nitrosoaniline.
A variety of polar organic solvents can be used in the practice of the present invention. Among these solvents, examples of the polar organic solvents, preferred in view of a miscibility with the base, include, but are not limited to, dimethylsulfoxide (hereinafter, called “DMSO”), N,N-dimethylformamide (hereinafter, called “DMF”), and N-methyl-2-pyrrolidinone (hereinafter, called “NMP”). A reaction in DMSO results in the highest reactivity and yield. The weight ratio of the solvent to urea used is in the range of about 50:1 to about 1:1, with the preferred ratio being in the range of about 30:1 to about 1:1.
Examples of the base used in accordance wit
Hwang Kum-Ui
Joo Young J.
Kim Jin-Eok
Won Jeong-Im
Barts Samuel
Harrison & Egbert
Korea Kumho Petrochemical Co. Ltd.
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