THE PREPARATION OF 4,4'-DINITRODIPHENYLAMINE FROM UREA AND NITROBENZENE

Abstract: Disclosed herein is a method for preparing 4,4'-dinitrodiphenylamine, comprising reacting urea and nitrobenzene in a polar organic solvent in the presence of a base at a temperature of room temperature to 1000 DEG C. The method employs a relatively cheap urea and nitrobenzene as the raw materials, and also employs a relatively cheap base, thereby decreasing the manufacturing costs. Moreover, the method does not produce by-products, thus eliminating a need for a post-treating process. Additionally, the method is advantageous in that the production of 4,4'-dinitrophenylamine can be achieved in high yield and selectively even under non-intensive reaction conditions by appropriately controlling the amounts of urea and nitrobenzene.

Description: THE PREPARATION OF 4 , 4 ' -DINITRODIPHENYLAMINE FROM UREA AND NITROBENZENE Technical Field The present invention relates in general to a method of preparing 4 , ' -dinitrodiphenylamme by reacting urea and nitrobenzene in a polar organic solvent in the presence of an organic or inorganic base. More particularly, the present invention relates to a method of selectively preparing , ' -dinitrodiphenylamme by dissolving urea and nitrobenzene in a polar organic solvent, and then by allowing those urea and nitrobenzene to react together m the resulting solution while using an inorganic base, such as sodium hydroxide, or an organic base, such as tetramethylammonium hydroxide (hereinafter, called "TMA(OH) ") . Background Art As 4 , ' -dinitrodiphenylamme is easily reduced into 4 , 4 ' -diammodiphenylamine, it is mainly used as a raw material for an antioxidant for a dye or rubber. Japanese Patent Publication No. Heisei 10-168038 (1998) describes a method for synthesizing diammodiphenylamine synthesizing method involving a reduction of dinitrodiphenylamme. In the above mentioned patent publication, a diammodiphenylamine compound is described as being greatly effective for an intermediate of an antioxidant or antiaging agent. 4 , 4 ' -diammodiphenylamine or its derivatives, besides being used as an intermediate of an additive to rubber, are also used as an intermediate of dyes, agricultural chemicals or medical substances. An example of conventional methods for preparing 4 , ^ ' -dinitrodiphenylamme involves nitration and deacetylation of N-acetyldiphenylamme . Such a method, however, is problematic in that the nitration is non- umformly carried out. Furthermore, there is an inconvenience in that nitrodiphenylam e inevitably produced should be removed using a recrystalization from alcohol. With another method for preparing 4,4'- dimtrodiphenylamme, US Patent No. 4,990,673 (1991) discloses a method in which 4-chloroanιlme is reacted with alkali metal cyanate to produce 4,4'- dinitrodiphenylamme . However, a disadvantage with the latter method is that the reaction must be carried out at a temperature of 160 °C or above for an extended period of time of more than 15 hours. In addition, known is another method of preparing dinitrodiphenylamme derivative by a reaction of 4- nitroanilme with a nitrobenzene derivative (see, J. Am. Chem. Soc, 1976, (1), pp 138-143). Such a reference describes a method which 4-nιtroanιlme and nitrobenzene derivatives are allowed to react using potassium t-butoxide (t-BuOK) as a base, thereby producing 2 , 4 ' -dinitrodiphenylamme or 4 , 4 ' -dinitrodiphenylamme depending on the amount of tne base, or alternatively producing 5-chloro (bromo) -2, 4 ' -dinitrodiphenylamme using halogen as a substitute. The present invention relates to a method of selectively preparing , ' -dinitrodiphenylamme using a nucleophilic aromatic substitution for hydrogen (hereinafter, called "NASH") . The NASH reaction recently proposed is advantageous m that, since amme or amide is reacted directly with nitrobenzene or its derivative m the presence of a base, any hazardous material or any mtermediate, difficult to be removed, is not produced. A process is also known wherein aniline and nitrobenzene are directly reacted in the presence of a oase, such as "TMA(OH)", to prepare 4-nιtrodιphenylamme (hereinafter, called "4-NDPA") and 4-nιtrosodιphenylamme . See, J. Am. Che . Soc, 1992, 114(23), 9237-8; US Patent No. 5,117,063; US Patent No .5, 253, 737 ; US Patent No. 5,331,099; US Patent No .5, 453, 541 ; US Patent No. 5,552,531; and US Patent No 5,633,407. In addition, the use of the NASH reaction is described in US Patent No. 5,436,371, US Patent No. 5,117,063, and International Patent Publication No. WO 93/24447. These patents disclose a method of synthesizing N- (4-nιtrophenyl) benzamide using benzamide other than aniline. More concretely, there is described preparing 4- mtroaniline by synthesizing N- (4-nιtrophenyl ) benzamide using nitrobenzene in the amourt of about 1 mole based on benzamide and then by hydrolyzmg the resulting product with water or ammonia. However, there is no mention of the preparation of 4 , 4 ' -nitrodiphenylamine . This seems to be because N- ( 4-nιtrophenyl ) benzamide produced by a reaction of amide and nitrobenzene is a stable and separable compound, so that it is no longer reacted with nitrobenzene . Disclosure of the Invention The present invention employs the NASH reaction as mentioned above, and utilizes urea instead of aniline or benzamide. More particularly, the present invention is a method of selectively preparing , 4 ' -dinitrodiphenylamme by reacting urea with an excess of nitrobenzene. 4- Nitroaniline, which is an intermediate produced with the present invention, is increased m production at the Degmnmg of the reaction, and easily reacted with nitrobenzene to produce 4 , 4 ' -dinitrodiphenylamme . The method in accordance with the present invention is advantageous m that the reaction is relatively simple while allowing a selective production of only 4,4'- d itrodiphenylamme using a relatively cheap alkali base without producing other by-products. We have made diligent efforts to find an improved method for preparing 4 , 4 ' -dinitrodiphenylamme, which does not involve production of by-products and reguirement of any post-treating process. As a result, we have found that 4 , ' -dinitrodiphenylamme can be produced without production of by-products and requirement of any post- treating process while reducing the manufacturing costs when urea, which is relatively cheap, is directly reacted with nitrobenzene in a polar organic solvent using a relatively cheap base. It has also been found that the production of 4 , ' -dinitrodiphenylamme can be achieved in high yield and selectivity even under non- tensive reaction conditions by appropriately controlling the amounts of urea and nitrobenzene. Based on such facts, the present invention has been achieved. In accordance with the present invention, an inorganic or organic base may be used for the Dase existing in the polar organic solvent for the reaction of urea and nitrobenzene to achieve a selective production of 4, 4 ' -dinitrodiphenylamme. Preferably, an alkali metal or alkaline earth metal base, such as sodium hydroxide, may be used for the inorganic base. On the other hand, a base such as TMA(OH) may be preferably used for the organic base. In the reaction of urea and nitrobenzene accordance with the present invention, 4-nιtroanιlme is produced at the beginning of the reaction. Using an extended period of reaction time, however, such 4- nitroamlme is reacted with nitrobenzene, thereby producing , 4 ' -dinitrodiphenylamme . Consequently, only 4, ' -dinitrodiphenylamme can be obtained without any byproducts. 4-Nιtroanιlιne is produced m a fast rate at the beginning of the reaction while reacting with nitrobenzene as the reaction further proceeds, thereby producing only 4 , 4 ' -dinitrodiphenylamme . On the other hand, 4 , ' -dinitrodiphenylamme is slowly produced at the beginning of the reaction while being produced at an increased rate as the reaction of 4-nιtroanιlme and nitrobenzene proceeds. The reaction is conducted in such a fashion that it is completed at the point of time when 4-nιtroanιlme is completely consumed. Moreover, the reaction is carried out under an oxygen atmosphere to prevent azoxybenzene from being produced. Best Mode for Carrying Out 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 is directed to a method of selectively preparing , ' -dinitrodiphenylamme by reacting urea and nitrobenzene m a polar organic solvent in the presence of an organic or inorganic base. In the practice of the present invention, dimethylsulfoxide (hereinafter, called "DMSO"), which is a polar organic solvent, is preferably used m view of solubilities of urea and nitrobenzene. The molar ratio of nitrobenzene to urea used is in the range of about 1:1 to about 16:1, with the preferred ratio in view of yield being in the range of about 4 : 1 to about 8:1. The volume ratio of the solvent to urea and nitrobenzene used is in the range of 50:1 to 1:1, with the preferred ratio being in the range of 30:1 to 1:1. Examples of the base used in accordance with the present invention include, but are not limited to, organic and inorganic bases, such a c sodium hydroxide (NaOH) , potassium hydroxide (KOH) , potassium t-butoxide (t-BuOK) , sodium hydride (NaH) , and TMA(OH). The molar ratio of the base to urea used is in the range of about 1:1 to about 20:1. The higher the amount of the base used, the higher the yield. However, where the molar ratio of the base to urea is 12:1 or above, the yield is rather decreased. On the other hand, where the molar ratio of the base to urea is 4:1 or below, it shows a result that 4-nιtroanιlme remains even when the reaction is carried out at a temperature of 60 °C for 8 hours. The reaction temperature is m the range of room temperature to 100°C, with the preferred reaction temperature being in the range of 50 to 80 °C. Where the reaction temperature is low, such as less than 50 °C, the reaction rate is too slow. On the other hand, where the reaction temperature exceeds 80 °C, the yield is remarkably decreased due to the decomposition of urea. The lower the reaction temperature, the longer the time during which 4-nιtroanιlme produced at the beginning of the reaction is converted into 4 , 4 ' -dinitrodiphenylamme . Of course, the extended reaction time results in an increase m yield of a product. On the other hand, at the reaction temperature exceeding 80 °C, the yield of the product is high at the beginning of the reaction. However, the yield of the product increases no longer from the level at the beginning of the reaction due to a decomposition of urea. Accordingly, the reaction temperature is determined to be ranged from 50 °C to 80 °C m order to prevent a decomposition of urea while increasing the reaction rate, thereby obtaining an increased yield of the product. Moreover, we surprisingly found that, where the moisture content in the reaction system is 5% or less based on the weight of the entire reaction solution, it does not have a significant effect on a reactivity. Thus, no particular process to remove the moisture of the solvent is used. Where the reaction is carried out in a state where water is added to the solvent m an amount of 1%, a high yield is exhibited at the beginning of the reaction. In this case, however, the yield exhibited after the reaction of about 6 hours is not so high, as compared to that of the case where water is not added. In addition, an excess of azoxybenzene is produced under an atmosphere not containing oxygen whereas no azoxybenzene is produced under an atmosphere containing oxygen. Examples The following examples are for illustration purposes on y and m no way limit the scope of this invention. In the following examples, products were analyzed by the Nuclear Magnetic Resonance (NMR) spectrum and the Gas Chromatography-Mass Spectroscopy Detector to identify them. Also, the products were quantitatively analyzed according to the following condition by high performance liquid chromatography . Such a high performance liquid chromatography was carried out using a product manufactured by Hitachi Co. in Japan and consisting of an L-6200 intelligent pump and an L-4200 UV-VIS detector. In high performance liquid chromatography, all quantitative values were measured at a wavelength of 254 n , and developing speed was 1 ml/ramute. Furthermore, high performance liquid chromatography, a Cosmosil 5C18-AR ( 4.6 xl50 mm) packed column was used. An elution gradient of high performance liquid chromatography was as follows. Elution gradient Solvent A Solvent B Time (minute) % Distilled water Acetonitrile 65 35 25 100 33 65 35 For the quantitative analysis of each product, pyrene was used as an internal standard. An area ratio for a concentration of each material was calculated relative to an area of pyrene and standard-calibrated. A molar concentration of a product was calculated from the calibration curve. Example 1 Into a 100ml three-necked reactor equipped with a condenser and a thermometer were charged 1.2 g (20 mol.) of urea, 9.6 g (240 mol.) of sodium hydroxide, 0.1 g of pyrene, and 30 ml of DMSO solvent. Then, the resul t ing mixture was added with 8.2 ml (80 mol.) of nitrobenzene while stirring. Thereafter the resulting solution was stirred for 30 minutes while passing oxygen, so that it was subsequently allowed to conduct a reaction at a temperature of 60 °C. A progressed degree of the reaction was confirmed by HPLC. After the reaction, the product was cooled. Analysis of the product by HPLC showed that, where the reaction was carried out for 6 hours, 4,4'- dmitrodiphenylam e was obtained in a yield of 82 mol%, and where the reaction was carried out for 8 hours, 4,4'- dimtrodiphenylamme was obtained in a yield of 94 mol%. Example 2 Reactions were carried out under the same conditions as those in Example 1 except that the reaction temperature for each reaction was changed. Results are shown m Table 1 below. Table 1: Change m yield with change in reaction temperature Reaction Time ( hr ) Yield (mol temperature 4 -NA A DNDPA B ( ° C ) so 59 70 67 60 82 8.9 5^ 6.: 63 A) 4-NA : 4-nιtroanιlιne B) DNDPA: 4 , 4 ' -dinitrodiphenylamme Example 3 Reactions were carried out under the same conditions as those in Example 1 except that the kind of base and the amount of the base for each reaction were changed. Results are shown in Table 2 below. Table 2 : Change in yield with change in the kind of base Base Base amount Time (hr) Yield (mol%) (g(mol.) ) 4-NA A DNDPA B Sodium 9.6 (240) 94 hydroxide Potassium 17.9 (320) 52 hydroxide Potassium 4.5 (40) 37 t-butoxιαe c TMA(OH) 8.6 (47) 51 A) 4-NA : 4-nιtroanιlme B) DNDPA: 4 , 4 ' -dinitrodiphenylamme C) and D) : 0.6 g (10 mol.) of urea was used. Example 4 Reactions were carried out under the same conditions -li¬ as those in Example 1 except that the amount of the base for each reaction was changed. Results are shown in Table 3 below . Table 3: Change m yield with change in the amount of base Base amount Reaction time Yield {%) (g(mol.)) (hr) 4-NA A DNDPA B 3.2 (80) 8 14 55 6.4 (160) 8 5 67 9.6 (2401 8 - 94 12.8 (320) 8 - 92 A) 4-NA : 4-nιtroanιlme B) DNDPA: 4 , 4 ' -dinitrodiphenylamme Example 5 Reactions were carried out under the same conditions as those in Example 1 except that the amount of DMSO solvent for each reaction was changed. Results are shown in Table 4 below. Table 4 : Change in yield with change in the amount of solvent Amount of DMSO Reaction time Yield (%) (ml) (hr) 4-NA A DNDPA B 20 8 - 65 ■ i/- 9i 72 A 4-NA • 4-nιtroanιlme B DNDPA: 4 , 4 ' -dinitrodiphenylamme Example 6 Reactions were carried out under the same conditions as those in Example 1 except that the amount of nitrobenzene to the amount of urea for each reaction was changed. Results are shown in Table 5 below. Table 5: Change in yield with change in the amount of nitrobenzene Amount of Reaction time Yield (%) nitrobenzene (hr) 4-NA A DNDPA B (ml (mol . ) 4.1 (40) 8 7 67 8.2 (80) 8 - 94 16.4 (160) 8 - 75 A) 4-NA : 4-nιtroanιlme B) DNDPA: 4 , 4 ' -dinitrodiphenylamme Example 7 Reactions were carried out under the same conditions as those m Example 1 except that moisture content for each reaction were changed. Results are shown in Table 6 below. Table 6: Change m yield with change moisture content Drying agent ana Reaction time Yield (%) moisture content (hr 4-NA' ' DNDPA B None c 8 - 94 1% ater E 8 - 70 5% Water F 8 3 58 A) 4-NA : 4-nιtroanιlιne B) DNDPA: 4 , 4 ' -dinitrodiphenylamme C) . Commercially available solvent was used without further purification (no drying agent was used). D) : A drying agent was used to remove moisture in a reaction system. E) : Distilled water was added m the amount of 1% based on the volume of the solvent. F) : Distilled water was added m the amount of 5% based on the volume of the solvent. Example 8 Reactions were carried out under the same conditions as those in Example 1 except that an atmosphere for each reaction was changed. Results are shown in Table 8 below. Table 8: Change m yield with reaction atmosphere Reaction Reaction time Yield (%) atmosphere (hr) 4-NA A DNDPA 8 Oxygen 8 - 94 Nitrogen 8 2 50 Air 8 1 75 General 8 3 56 atmosphere A) 4-NA : 4-nιtroanιlme B) DNDPA: 4 , 4 ' -dinitrodiphenylamme Industrial Applicability As apparent from the above description, the method of the present invention for preparing 4,4'- dinitrodiphenylamme uses relatively cheap urea and nitrobenzene, as raw materials, while using a relatively cheap base, thereby decreasing the manufacturing costs. Moreover, the method of the present invention does not produce by-products, thus eliminating a need for a post- treating process. Additionally, the method of the present invention is advantageous that the production of 4,4'- dmitrodiphenylamme can be achieved m high yield and selectivity even under non-mtensive reaction conditions by appropriately controlling the amounts of urea and nitrobenzene. Although the preferred emoodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims: Claims 1. A method for preparing 4,4'- dinitrodiphenylamme, comprising reacting urea and nitrobenzene a polar organic solvent in the presence of a base at a temperature of room temperature to 100 °C. 2. The method of claim 1, wherein the molar ratio of the nitrobenzene to the urea is in the range of 2:1 to 10:1. 3. The method of claim 1, wherein the molar ratio of the base to the urea is m +"he range of 1:1 to 20:1. 4. The method of claim 1, wherein the volume ratio of the polar organic solvent to the reactants is in the range of 1:1 to 50:1. 5. The method of claim 1, wherein the base is selected from the group consisting of sodium hydroxide, sodium hydride, potassium hydroxide, potassium t-butoxide, and tetramethylammonium hydroxide. 6. The method of claim 1, wherein the polar organic solvent is dimethylsulfoxide (DMSO) . 7. The method of claim 1, wherein the reaction is carried out in a nitrogen, oxygen, or air atmosphere.

Inventors: HWANG KUM-UI, JOO YOUNG J, KIM JIN-EOK, WON JEONG-IM, HWANG, KUM-UI, JOO, YOUNG, J., KIM, JIN-EOK, WON, JEONG-IM
Applicants: KOREA KUMHO PETROCHEM CO LTD, KOREA KUMHO PETROCHEMICAL CO., LTD.
Application year: 2000
Main classification: C07C209
IPC codes: C07B61, C07C209, C07C211