MXPA00011832A - Preparation of quinonediimines from phenylenediamines using oxygen and a metal or metal salt catalyst - Google Patents

Abstract

A phenylenediamine compound can be converted, with high selectivity, into its corresponding quinonediimine by reacting the phenylenediamine with oxygen and a metal catalyst or a salt thereof.

Description

PREPARATION OF QUINONA-DIIMIN FROM PHENYLENDIAMINE USING OXYGEN AND A METALLIC CATALYST OR METAL SALT CATALYST This application claims priority at the filing date of the provisional application E.U.A. No. 60 / 087,754, filed on June 2, 1998.

FIELD OF THE INVENTION This invention relates to a process for preparing quinone diimines from their corresponding phenylenediamines using oxygen and a metal catalyst or a salt of a metal catalyst.

BACKGROUND OF THE INVENTION 15 The class of cyclic enones is well known in organic chemistry. The best known examples of cyclic enones are quinones such as, for example, benzoquinones, naphthoquinones, anthraquinones, phenoanthraquinones and the like. 1,4-Benzoquinone is commonly known as quinone. Quinones are usually brightly colored compounds and have versatile applications in chemical synthesis, biological uses, such as redox materials, as well as in industry. There are several review articles on the chemistry and applications of quinones, including, for example, Kirk- Othmer Encyclopedia of Chemical Technology, 3rd ed., Vol. 19, pages 572-605, John Wiley & Sons, New York, 1982. The synthesis of quinones is well documented. See for example J. Cason, Synthesis of Benzoquinones by Oxidation, in Organic Synthesis, Vol. IV, page 305, John Wiley & Sons, New York (1948). In general, the quinones are prepared by oxidizing the appropriately disubstituted aromatic hydrocarbon derivatives, the substituents being hydroxyl or amino groups in the ortho or para positions. For example, 1,4-benzoquinone can be made from the oxidation of hydroquinone, p-aminophenol or p-phenylenediamine, or from quinic acid. The reagents used for oxidation are generally dichromate / sulfuric acid, ferric chloride, oxide < of silver (II) or ceric ammoniac nitrate. In these cases, the oxidation of the aromatic amino compound is accompanied by hydrolysis to the corresponding quinone. Some procedures can take hours for the reaction to complete. Therefore, some prior art methods use a catalytic agent to achieve an acceptable reaction although other procedures proceed without catalysts. The process according to the present invention utilizes a metal catalyst or a metal salt catalyst for oxidation, which provides a conversion and high reaction rates for preparing the quinone diimine. A prior art process, which utilizes a catalyst in the preparation of a quinone diimine compound, is described by Desmurs, et al., In the U.S. patent. No. 5,189,218. The procedure - ^ &&&^^^^^^^^^^^ ¿K¿ &^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ from Desmurs, et al., which converts N- (4-hydroxyphenyl) aniline to N-phenylbenzoquinone-imine, uses a compound of manganese, copper, cobalt and / or nickel as a catalyst in an oxidation-type reaction. Although Desmurs, et al., Identify the conversion of N-phenylbenzoquinone-imine to an N-phenyl-N'-cycloalkyl-2,5-cyclohexadiene-1,4-diimine, Desmurs, et al., Fail to recognize the use of an oxidation catalyst for the conversion, and they do not mention anything about a metal catalyst for oxidation, such as that used in the present invention. This is made evident by the suggestion of Desmurs, et al., In column 5, lines 14-22, to use a catalyst for hydrogenation. Other processes using oxidizing agents to convert the phenylenediamines to their corresponding quinone diimines are also known. For example, EP 708,081 (EJernhardt et al) which describes the conversion of phenylenediamines to phenylenedimines by oxidation of the diamine in an alcoholic alkaline solution gives a general description of such processes in its Background section of the invention. The process of EP '081 has several disadvantages including long reaction times and low yields. The additional oxidation conversion processes are described by Wheeler in the U.S.A. 5, 118,807, by GB 1, 267,635 and by Hass et al, in EP 708,080. However, to date the use of oxygen together with a metal catalyst or salt of a metal catalyst in the conversion of phenylenediamine compounds to obtain highly selective yields of quinone diimine compounds has not been suggested. As such, the present invention is based on the problem of providing a simple and inexpensive procedure for preparing quinone diimines with high yields and with a high purity.

BRIEF DESCRIPTION OF THE INVENTION It has been discovered that phenylenediamine compounds can be converted with extremely high selectivity, the quinone diimine by reacting the corresponding diamine with a metal catalyst, or a salt thereof, in the presence of oxygen. Conditions are revealed in which almost quantitative yields have been obtained. In contrast to the prior art, an advantage of the present invention is that the conversion of phenylenediamine to the corresponding quinone diimine is almost quantitative. Therefore, very little waste material remains after completing the reaction. An additional advantage is that a catalyst metal or salt of the metallic catalytic agent, as described herein, provides an extremely high conversion, high selectivity and reactions are completed more quickly compared to processes of the prior art . - * ^^^ £ ^ = ws ^^^^^^? Fe ^^^^ The additional advantages of the present invention will become apparent to those skilled in the art after reading and understanding the following detailed description of the preferred embodiments. .

DETAILED DESCRIPTION OF THE INVENTION The object of the present invention is to provide an effective method for converting phenylenediamines to their corresponding quinone diimines. In accordance with the object of the invention, a phenylenediamine (ortho or para) is reacted according to the formula Ia or Ib: Formula Formula Ib wherein Ri and R2 are independently selected from hydrogen, hydroxyl, alkyl, alkoxy, aryloxy, alkenyl, cycloalkyl, aryl, aralkyl, alkaryl, alkylamino, arylamino, heterocycle, acyl, formyl, aroyl, cyano, halogen , thiol, alkylthio, arylthio, amino, nitro, sulfonate, alkylsulfonyl, arylsulfonyl, aminosulfonyl, hydroxycarbonyl, alkyloxycarbonyl and ^^^^^ i ^^^ fe ^ j ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^ Í ^^^^^^^^^^^^^^^^^^^^^ gj ^^^ j ^ ¿^ ariloxicarbonüo, wherein the alkyl portion in the groups Ri and R2 can be linear or branched and each of the groups R1 and R2 can also be replaced; wherein also R3, R4, Rs and Rβ are the same or different and are selected from hydrogen, hydroxyl, alkyl, alkoxy, aryloxy, alkenyl, cycloalkyl, aryl, aralkyl, alkaryl, alkylamino, arylamino, heterocycle, acyl, aroyl , cyano, halogen, thio !, alkylthio, arylthio, amino, nitro, sulfonate, alkylsulfonyl, arylsulfonyl, aminosulfonyl, hydroxycarbonyl, alkyloxycarbonyl and aryloxycarbonyl, wherein the alkyl portions in the groups R3, R4, Rs and Rs can be linear or branched and each of the 10 groups R3, R4, R5 and Re can also be further substituted where appropriate; with oxygen in the presence of a metallic catalyst or salt of! same. The reaction produces a corresponding quinone diamine according to the formula lia or llb: Formula lia Formula llb on in which! Ri, R2, R3, R4, Rs and Rβ are the same as in the compound according to the formula la or Ib. The reaction is represented as follows: REACTION SCHEME 1 More particularly, the variables Ri and R2 are selected from hydrogen, hydroxyl, C1-C50 alkyl, C1-C50 alkoxy, C6-C40 aryloxy, C2-C50 alkenyl, C3-C20 cycloalkyl, C6 aryl -C40, aralkyl C7-C50, C7-C50 alkaryl, C1-C20 alkylamino and dialkylamino, C6-40 arylamino and diarylamino, C3-C30 heterocyclic containing one or more N, O, S, or P, acyl atoms of C2-C50, formyl, C7-C40 aroyl, cyano, halogen such as F, Br, I, or Cl, thiol, C1-C50 alkylthio, C6-C40 arylthio, amino, nitro, sulfonate having the formula SO3X in which X is selected from sodium, C1-C50 or aryl of C6-C40, alkylsulfonyl, arylsulfonyl, aminosulfonyl, hydroxycarbonyl, alkyloxycarbonyl C1-C50 and aryloxycarbonyl of C6-C40, wherein the alkyl portion in the Ri groups may be linear or branched and each of the Ri groups may be further substituted with appropriate groups; where also R3, R ^ R5 and Re are identical or different and are selected from hydrogen, hydroxyl, C1-C50 alkyl, C1-C50 alkoxy, C6-C40 aryloxy, C2-C50 alkenyl, C3-C20 cycloalkyl, C6-aryl C40, aralkyl of C7-C50, alkaryl of C7- C50, alkylamino and dialkylamino of C1-C20, arylamino and diarylamino of C6- AaaátaiBfeateafe-. x--? iMtXZ * xáx rhz JL C40, C3-C30 heterocyclics containing one or more N, O, S, or P atoms, C2-C50 acyl, formyl, aroyl, cyano, halogen such as F, Br , I, or Cl, thiol, C1-C50 thioalkyl, C6-C40 thioaryl, amino, nitro, sulfonate having the formula SO3X in which X is selected from sodium, C1-C50 alkyl or C6-C40 aryl , alkylsulfonyl, arylsulfonyl, aminosulfonyl, hydroxycarbonyl, C 1 -C 50 alkyloxycarbonyl and C 6 -C 40 aryloxycarbonyl, in which the alkyl portions in the groups R 3, R 4, R 5 and R 2 can be linear or branched and each of the groups R 3, R4, R5 and Re may also be substituted where appropriate. Preferred groups for R1 and R2 are C1-C20 alkyl, C6-C20 aryl, C7-C20 alkaryl, C3-C10 cycloalkyl, C2-C20 alkenyl, C3-C20 heterocyclic, C2-C20 acyl and Aroyl of C7-C20. Examples of radicals satisfactory for R ?, R2, R3, R4, R5 and Re are linear or branched alkyls such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, 1, 3- dimethylbutyl, 1,4-dimethylpentyl, isopropyl, sec-butyl, 1-ethyl-3-methylpentyl, 1-methylheptyl, and the like; aryls such as phenyl, naphthyl, anthracyl, tolyl, ethylphenyl and the like; cycloalkyls such as cyclobutyl, cyclopentyl, cyclohexyl, cyclooctyl and the like. Other examples include hydrogen, allyl and isobutenyl; 1, 3,5-s / m-triazinyl, 2-benzothiazolyl, 2-benzimidazolyl, 2-benzoxazolyl, 2-pyridyl, 2-pyrimidinyl, 2,5-thiadiazolyl, 2-pyrazinyl, adipyl, glutaryl, succinyl, malonyl, acetyl, acrylyl, methacrylyl, caproyl, 3-mercaptopropionyl, benzoyl, phthaloyl, terephthaloyl, aminocarbonyl, ethoxycarbonyl, formyl and the like. These are only exemplary radicals and are in no way intended to limit the scope of the invention. In the reaction, in accordance with the present invention, metal catalysts are typically transition metals of groups IB, IIB, VB, VIB, VIIB, and VIII of the periodic table. The metals can be found in their ionic state or in the form of a metal salt. The catalysts can be used alone or in mixtures. Typically, metals include V, Nb, Ta, Cr, Mo, W, Mn, Te, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd , Hg, and its salts. Supported catalysts such as Pd / C, Pt / C, Ni / Al, Ru / C, Rh / C and the like are also included. Some examples of catalysts that are preferred, but not limited to, include Pt / C, Pd / C, Rh / C, Ru / C, nickel (II) oxide, cobalt-on-carbon phthalocyanine, and silver. The catalysts used in the present invention are typically present in amounts ranging from about 0.1% by weight to about 20.0% by weight, based on the weight of the phenylenediamine starting material. The catalysts of the present invention cause the conversion reaction in the process according to the present invention. It is possible to use solid catalysts in the reaction according to the present invention since there is an ease in the recovery of the solid catalysts, by filtration, and the solid catalysts can be reused in the process. There are also utilities with respect to the environment, and it is less likely that there is contamination in the catalyst ^^ & kj ^^ & $ S and ^. ^^^^ tó¡- ^ fc¡ * j - * A ^ ^^ in the final quinondiimine isolate. Additionally, the catalysts give high conversion and excellent selectivity. The reaction, according to the present invention, is carried out either in a homogeneous system or in a system of solvent of two faces. The water-soluble organic solvents are used for the homogeneous reaction while the water-insoluble hydrocarbon organic solvents produce the two-phase system. The two-phase system also includes water. The two-phase oxidation system provides ease of separation of the organic components (quinondiimine and solvent) from the spent organic layer. Organic aprotic solvents useful in the method of the present invention include, but are not limited to, ketones such as cyclohexanone, 4-methyl-1-2-pentanone (methyl isobutyl ketone), 5-methyl-1-2-hexanone, methyl ethyl ketone; aliphatic and aromatic hydrocarbons such as hexanes, heptanes, toluene, xylenes, nitriles such as acetonitrile, halogenated solvents such as chloroform, dichloromethane, carbon tetrachloride, water-soluble solvents such as dimethyl sulfoxide, N-rnethyl-2-pyrrolidone, sulfolane, dimethylformamide; esters such as ethyl acetate, ethers such as 1,4-dioxane, alcohols such as methanol, and mixtures thereof. As with the catalysts, the solvents, when recovered from the product, can be recycled and used in the reaction. When water is present in the reaction, it is typically present in amounts up to 75% by weight, based on the weight of the total reaction mixture. Water can be present as the only solvent j ^^^^^^^^^^^^^^^^^ J ^^^^^^^^^^^^^^^^^^^^^^^^^ j ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Sg ^^^^^^ ^^^ or it may be combined with other organic solvents soluble or insoluble in water. When using a water soluble salt or a metal catalyst in the reaction according to the present invention, it is desirable to use a two phase solvent system. The use of the two-phase solvent system with the water-soluble metal catalysts allows for easy separation of the catalysts from the desired final product, since the final product is present in the organic phase, while the catalyst is present in the aqueous phase . Again, the catalyst and the aqueous solvent can be recycled and returned to the reaction. The initial concentration of phenylenediamine can vary in amounts from about 1% to 100% w / v. Preferably, the initial concentration of phenylenediamine ranges from about 25% to about 60% w / v. The present reaction can be carried out at temperatures from about 0 ° C to about 150 ° C, preferably from about 25 ° C to about 70 ° C. A phase transfer catalyst can be used to accelerate the rate of reaction with the metal catalysts mentioned in the preceding paragraphs. With water-immiscible solvents it is useful to use a phase transfer catalyst to accelerate the rate of the reaction in the process of the present invention. Phase transfer catalysts useful in the present invention include, but are not limited to, quaternary ammonium salts, such as tetramethylammonium hydroxide, tetraalkylammonium halides, tetra-N-butylammonium bromide, tetra-N-butylammonium chloride, benzyltriethylammonium; phosphonium salts such as bis [tris (dimethylamino) phosphine] iminium chloride; crown ethers and polyethylene glycols. The phase transfer catalyst can be added directly to the reaction mixture or it can be dissolved in one of the reagents such as phenylenediamine. The phase transfer catalyst can also be dissolved in a solvent used in the process or in water before addition to the reaction mass. Another means by which the reaction rate may increase is increasing the rate of agitation or mixing in the reaction. By increasing agitation or mixing, the speed of the reaction can be adjusted effectively to continue at a faster pace when necessary. Other means for increasing the reaction rate include increasing the reaction temperature, increasing the pressure at which the reaction is carried out and increasing the amount of catalysts used. Additionally, the addition of basic pH adjusting agents, such as triethylamine, can increase the reaction rate and also provide an increased selection capacity for the desired quinondiimine end product.

Additionally, latfection can use a combination of more than one starting material phenylenediamine to produce a product containing a mixture of quinondiimines. Also, the reaction can be stopped before reaching term thereby producing a product comprising a mixture of phenylenediamine and quinonediimine. By adjusting the amount of the catalyst, adjusting the amount of pH adjusting agents and / or adjusting the amount of oxygen present in the reaction, for example, very specific mixtures of phenylenediamine and quinondiimine can be obtained. Depending on the particular use of the product, such mixtures can provide better results than a product with higher amounts of quinondiimine. The present invention can be illustrated more clearly with the following examples.

EXAMPLE 1 A mixture of N-1, 3-dimethylbutyl-N'-phen? Lp-phenylenediamine - (Santoflex® 6PPD, 5 g, 0.019 mol), methanol (200 ml), triethylamine (2 ml), water (2 ml) and catalysts were charged to an autoclave. The reaction mixture was stirred and the autoclave was purged with oxygen and then oxygen was charged at 20-25 ° C, 2.10 Kg / cm 2 gauge. The reaction mixture was heated to 50 ° C and maintained at 50 ° C until the reaction was complete. While the reaction continued, the oxygen pressure decreased. When the pressure decreased to about 1.40 Kg / cm2 gauge, a greater amount of oxygen was charged to the reactor to bring the pressure back to 2.10 Kg / cm2 gauge. The reaction time was counted from the moment the oxygen was initially charged to the autoclave. When a very low or no oxygen uptake was detected, the mixture was filtered to remove the catalyst. The reaction times and the composition of the product of the resulting mixtures are tabulated in the following table. In most cases conversions superior to the desired quinondiimine product of N-1, 3-dimethylbutyl-N'-phenyl-p-phenylenediamine (6QDI) were obtained. In some reactions, the reaction was not completed, and therefore, the mixture indicated the presence of the unreacted starting material Santoflex® 6PPD. To the simple continuation, the reaction could complete these reactions. When the catalyst is heterogeneous, the reaction mixture can be filtered to separate the product from the catalyst. The concentration of the filtered reaction mixture can lead to the desired product, 6QDI in very high yields. In the examples listed in the following table, the reaction mixture was analyzed when there was no increased oxygen consumption or very low oxygen uptake, indicated in that way the term of the reaction. However, this method to determine if the reaction has ended or not, was not always reliable. Therefore, in some reactions, unreacted starting material was present. At the same time, when the reactions were completely completed, the actual reaction time could be less than the one listed in Table 1. The analyzes indicated the disappearance of Santoflex® 6PPD and the formation of the corresponding quinon-diimine at a high level. selectivity. The results of the percentage analysis of the area by CLAR are summarized in Table 1 below. The catalysts used for the execution numbers from 1 to 4 had approximately 50% water. In this way, on a dry weight basis, the weight of the catalyst would be about half the amount. For example, 0.5 g would be 0.25 g, etc. Various isolation techniques already known in the art can be used to isolate the product in accordance with the present invention, such isolation techniques include, but are not limited to filtration and concentration. The catalysts and solvents recovered from the reaction can be recycled and reused in subsequent reactions.

TABLE 1 A comparison of the following three examples indicates the advantage of adding agents for pH adjustment, such as triethylamine, in the rate of reaction and the selectivity of the desired product 6QDI. In the following examples the weight of the catalyst used is wet weight, which was about 50% water. So the dry weight of the catalyst used would be half the amount. For example, in case of a catalyst weight of 0.500 g, the dry weight of the catalyst would be 0.25 g, etc. These examples were performed under identical conditions and the same starting materials were used in all reactions to avoid variation from one batch to another and for a better comparison. The reactions were not taken to full completion and therefore the CLAR analysis indicated the _j- - d t .-: - fc fc¿ presence of the unreacted starting material Santoflex® 6PPD. With the simple additional continuity of the reaction these reactions can be completed.

EXAMPLE 2 This example teaches the effect of triethylamine to increase the speed of the reaction and for a better selectivity for the desired quinone diimine product. In accordance with the procedure established in the example 1, a mixture of N-1, 3-dimethylbutyl-N'-phenyl-p-phenylenediamine (Santoflex® 6PPD, 10.0 g, 0.038 mol), methanol (200 ml), triethylamine (2 ml), and catalyst, Pt / C at 3% (0.500 g), was loaded in an autoclave. The progress of the reaction was verified by taking samples in periods and analyzing CLAR for the 6QDI product and for the starting material Santoflex® 6PPD. The following table 2 summarizes the results. jgg ^ g ^ mjj ^ m & yj ^^^^^^^^^^^^^^^^^^^^^^^^ j ^ L ^^ ij TABLE 2 The addition of triethylamine is useful, since the selectivity for the desired product 6QDI is very high and the reaction rate is exceptionally high as well.

EXAMPLE 3 This example teaches the effect of the addition of triethylamine and water to increase the reaction rate and a better selectivity for the desired product quinonadiimine. According to the procedure set forth in example 1, a mixture of N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (Santoflex® 6PPD, 10.0 g, 0.038 mol), methanol (200 ml), triethylamine ( 2 ml), water (2 ml) and 3% Pt / C catalyst (0.500 g) was charged to an autoclave. The progress of the reaction was verified by taking samples for a period and analyzing by CLAR for the 6QDI product and for the Santoflex® 6PPD starting material. The following table 3 summarizes the results.

TABLE 3 The addition of triethylamine and water is useful, since the selectivity for the desired product 6QDI is very high and the reaction rate is exceptionally high as well. This example also indicates that the water in the reaction has no adverse effect on the reaction. l? ff fMtl ?? xM? ab »«, > A I I I EXAMPLE 4 The reaction will continue in the absence of a pH adjusting agent, as shown in the following example. In this manner, a product consisting of a mixture of phenylenediamine and quinonadiimine can be produced, or the reaction can be allowed to be completed if desired. According to the procedure set forth in example 1, a mixture of N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (Santoflex® 6PPD, 10.0 g, 0.038 mol), methanol (200 ml) and sodium 3% Pt / C (0.500 g) was charged to an autoclave. The progress of the reaction was verified by taking samples over a period and analyzing by CLAR for the 6QDI product and for the Santoflex® 6PPD starting material. The following table 4 summarizes the results.

TABLE 4 , m »» 3C8_ Áit i. i i In this experiment, the analysis by CLAR indicated the formation of a few new peaks other than the starting material Santoflex® 6PPD and the quinonadiimine compounds (6QDI) of the product. The formation of unwanted by-products, in turn, reduced the selectivity of the formation of desired product 6QDI. Even without the presence of triethylamine, the reaction continued, albeit at a slower rate than with triethylamine. The comparison of the following two examples further illustrates the advantages of adding pH adjusting agents, such as triethylamine, in the reaction rate and the selectivity of the desired product 6QDI. In the following examples, the weight of the catalyst used is wet weight, which has approximately 50% water. Therefore, the dry weight of the catalyst used would be half the amount. For example, in the case that the weight of the catalyst is 1,550 g, the dry weight of the catalyst would be 0.775 g and so on.

EXAMPLE 5 In accordance with the procedure set forth in example 1, a mixture of N-1, 3-dimethylbutyl-N'-phenyl-p-phenylenediamine (Santoflex® 6PPD, 5.0 g, 0. 019 moles), methanol (200 ml), triethylamine (2 ml), water (2 ml) and catalyst 3% Pt / C (1550 g) was charged to an autoclave. The progress of the reaction was verified by taking samples for a period and analyzing by means of CLAR for the 6QDI product and for the Santoflex® 6PPD starting material. The first sample taken after 0.5 hours was analyzed by HPLC area percentage and found to contain 99.3% of 6QDI. When the second sample, after 1 hour of reaction, was analyzed by percentage 5 of CLAR area, it was found to contain 99.4% of 6QDI. This was a clear indication that the reaction was over. The reaction mixture was filtered to remove the catalyst and the filtrate was concentrated to remove volatile materials. The resulting dark reddish colored liquid was identified as the corresponding N-I. S-dimethylbutyl-N'-phenyl-quinonadiimine (6QDI) and was isolated in almost quantitative yields.

EXAMPLE 6 In accordance with the procedure set forth in example 1, and under the same conditions of example 5, except for the addition of triethylamine and water, this experiment was carried out. A mixture of N-1, 3-dimethylbutyl-N'-phenyl-p-phenylenediamine (Santoflex® 6PPD, 5.0 g, 0.019 mmol), methanol (200 ml) and 3% Pt / C catalyst (1550 g) were added. He charged an autoclave. The progress of the reaction was verified by taking samples during a period and analyzing by CLAR for the product 6QDI and for the starting material Santoflex® 6PPD. The following table 5 summarizes the results of the CLAR area percentage analysis. These results clearly indicate that the reaction without triethylamine and water is slower than the reaction with triethylamine and water present, as demonstrated in example 5, in which the reaction was carried out in 30 minutes.

TABLE 5 It can be seen that an increased amount of catalyst in the process of Example 6 produces an increased reaction rate compared to Example 4. The quinonadiimines prepared by the process of the present invention show multiple activities in vulcanized elastomers. These activities include long-term antioxidant activity, together with antiozonant capacity. In fact, the antioxidant capacity of these antidegradants persists even after the vulcanized material has been extracted with solvents. In addition, quinonadiimines provide these benefits without the negative carbonization effect generally associated with the paraphenylenediamine antidegradants common in the industry. The summary of the activities of These rubber compounds can be found in the literature (Cain, M. E. et al., Rubber Industry 216-226, 1975). The invention has been described with reference to preferred embodiments. Obviously, modifications and alterations will occur to 5 others when reading and understanding the above detailed description. It is intended that the invention be construed as including all such modifications and alterations as long as they fall within the scope of the appended claims or equivalents thereof.

Claims (12)

NOVELTY OF THE INVENTION CLAIMS

1. A process for preparing a quinonadiimine by reacting a corresponding phenylenediamine with oxygen in the presence of a metal catalyst or a salt thereof.

2. The process according to claim 1, further characterized in that the metal catalyst is a supported metal catalyst, a transition metal catalyst, a salt of a transition metal catalyst or mixtures thereof.

3. The process according to claim 1 or 2, further characterized in that the metal catalyst is present in an amount of about 0.1 wt% to about 20.0 wt% in weight, based on the weight of the phenylene-phylline starting material. . A. The process according to any of claims 1 to 3, further characterized in that the phenylenediamine is an ortho- or para-phenylenediamine of the following formula Ia or Ib: Formula Formula Ib wherein Ri, R2, R3, R

4, R5 and Re are independently selected from phenyl, tolyl, naphthyl, 1,2-dimethylbutyl, 1,4-dimethylpentyl, isopropyl, sec-butyl, cyclohexyl, 1-ethyl-3 -methylpentyl, 1-methylheptyl and hydrogen, and R3-Rd are hydrogen.

5. The process according to any of claims 1 to 4, further characterized in that it consists in the addition of a basic pH adjusting agent to the reaction.

6. The process according to claim 5, further characterized in that the basic pH adjusting agent is triethylamine.

7. The process according to any of claims 1-6, further characterized in that the reaction also includes water.

8. The process according to any of claims 1 to 7, further characterized in that the reaction is carried out in the presence of a solvent.

9. The process according to claim 8, further characterized in that the reaction is carried out in a homogeneous solvent system and the solvent is selected from water-soluble organic solvents.

10. The process according to claim 9, further characterized in that the organic solvent soluble in water is an alcohol.

11. The process according to claim 8, further characterized in that the reaction is carried out in a two-phase solvent system, which consists of an organic solvent insoluble in water and water.

12. The method according to claim 11, further characterized in that it consists of the addition of a phase transfer catalyst to the reaction to increase the reaction rate.