Process for preparing ketoisophorone

Abstract: In the presence of (1) an oxidation catalyst comprising a crystalline complex of manganese with an N,N'-disalicylidenediamine (e.g., N,N'-disalicylidene C 2-8 alkylenediamines and N,N'-disalicylidene C 6-12 arylenediamines), or (2) an oxidation catalyst comprising the above complex and a basic nitrogen-containing compound, a substrate (e.g., β-isophorone or a derivative thereof) is oxidized with molecular oxygen to produce a corresponding oxide (e.g., ketoisophorone). Ketoisophorone can be obtained from β-isophorone with high conversion and high selectivity.

Description: FIELD OF THE INVENTION The present invention relates to a process for producing ketoisophorone from β-isophorone. BACKGROUND OF THE INVENTION Ketoisophorone (4-oxoisophorone), a useful intermediate for a starting material of medicines, perfumes, condiments, and for polymers, is produced from isophorone. For example, as a process for producing 4-oxoisophorone by oxidizing α-isophorone with oxygen, there have been proposed a method in which α-isophorone is oxidized with oxygen in the presence of a phosphomolybdic acid or a silicomolybdic acid [Japanese Patent Publication No. 30696/1980 (JP-B-55-30696)], a method in which α-isophorone is oxidized with oxygen in the coexistance of a phosphomolybdic acid or a silicomolybdic acid and an alkaline metal compound or an aromatic amine [Japanese Patent Application Laid-Open No.191645/1986 (JP-A-61-191645)], and a method in which α-isophorone is oxidized with oxygen in the presence of a vanadium catalyst [Japanese Patent Application Laid-Open No. 93947/1975 (JP-A-50-93947)]. Japanese Patent Application Laid-Open No. 81347/1974 (JP-A-49-81347) discloses a method for producing 4-oxoisophorone by oxidizing α-isophorone with an alkaline metal chromic acid salt or a dichromate or a chromium trioxide. In the Chem. Lett. (1983), (7), 1081, there is disclosed a method for producing 4-oxoisophorone by oxidizing α-isophorone using t-butylhydroperoxide in the presence of a palladium catalyst. However, in these methods, the selectivity of ketoisophorone is reduced, therefore separation of the formed by-product(s) or a metal catalyst and purification of the object compound are complicated. Moreover, these methods involve using a heavy metal compound requiring special treatment, such as chromium, or a peroxide needed to be handled with care, which results in a decrease in working efficiency. Moreover, as a method for producing ketoisophorone from β-isophorone, Japanese Patent Application Laid-Open No. 125316 (JP-A-51-125316) discloses a method for producing an ethylenically unsaturated dicarboxylic acid by oxidizing β-ethylenically unsaturated ketone with molecular oxygen or a molecular oxygen-containing gas in the presence of an inorganic base or an organic base and a cobalt or manganese chelate. In this method, however, the yield of ketoisophorone is low due to the use of a straight-chain secondary or tertiary amine such as triethylamine as the organic base. Japanese Patent Application Laid-Open No. 53553/1998 (JP-A-10-53553) discloses a method for producing ketoisophorone by oxidizing β-isophorone with molecular oxygen in the presence of bis(2-hydroxybenzylidene) ethylenediamine-manganese complex salt (i.e., manganese-salene), an organic base, a specific substance having a catalytic action (e.g., acetylacetone), and water. In the literature, there is recited as the manganese complex salt a complex in which 1 mole of bis(2-hydroxybenzylidene)-ethylenediamine is coordinated relative to 1 mole of manganese. However, even in the above method using the above manganese complex salt, the conversion and the selectivity of a substrate are not improved enough. Particularly, a higher concentration of β-isophorone in the reaction system causes a considerable decrease in the yield of ketoisophorone. For example, when the concentration of β-isophorone is 20% by weight or more, the conversion and/or the selectivity is decreased to a large extent. Therefore, relatively large amounts of a manganese complex salt and an organic base are required for an improved conversion. Further, a lower concentration of oxygen remarkably decreases the reaction rate. FR-A-2303785 discloses a method for producing ketoisophorone by oxidising β-isophorone with molecular oxygen in the presence of a manganese complex. This publication describes that the manganese complex may be prepared according to the method disclosed in Bailes et al., J. Am. Chem. Soc. 69, 1886 (1947). SUMMARY OF THE INVENTION The object of the present invention is to provide a process for producing ketoisophorone using an oxidation catalyst capable of producing ketoisophorone with maintaining high conversion and high selectivity even with a high β-isophorone concentration and a low oxygen concentration. The inventors of the present invention did intensive investigations to achieve the above object and found that, even in a reaction system with a high β-isophorone concentration and a low oxygen concentration, β-isophorone can be oxidized with high conversion and high selectivity by using a specific complex comprising manganese and an N,N'-disalicylidenediamine, and that the conversion and the selectivity are remarkably improved by further employing or incorporating a specific basic nitrogen-containing compound in combination with the above complex. The present invention was accomplished based on the above findings. The present invention provides a process for producing ketoisophorone, which comprises oxidizing β-isophorone with molecular oxygen in the presence of an oxidation catalyst comprising a crystalline complex of manganese with an N,N'-disalicylidene ethylenediamine, and a basic nitrogen-containing compound, wherein m+1 mole of said N,N'-disalicylidene ethylenediamine is coordinated to m mole of said manganese and m is an integer of not less than 1, and the infrared spectrum of said complex indicates an absorption peak for the hydroxyl group, said nitrogen-containing compound being an alicyclic or aromatic cyclic base selected from 1,4-diazabicyclo[2.2.2]octane (DABCO), 4-dimethylaminopyridine, 2-dimethylaminopyridine and 1,10-phenanthroline, said oxidation being carried out, in a ketone solvent, in a concentration of 20 to 50% by weight of β-isophorone in the reaction system and the water content of the reaction system is not more than 1% by weight. Preferred embodiments of the invention are set forth in the sub-claims. DETAILED DESCRIPTION OF THE INVENTION [Complex] The complex of the oxidation catalyst used in the present invention is a crystalline complex of manganese with an N,N'-disalicylidene ethylenediamine. The valence of manganese is usually in the range of divalent to tetravalent (particularly, divalent). The above N,N'-disalicylidenediamine has a structure in which a salicylidene group is bound to each nitrogen atom of the two amino groups of ethylene-diamine. The manganese complex used in the present invention comprising manganese and an N,N'-disalicylidenediamine ligand is represented by the following formula: wherein R 1 , R 2 , and R 3 each represents an ethylene group; R 4 to R 9 are the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group, a hydroxyl group, a hydroxymethyl group, or an alkoxy group; the rings Z are benzene rings; M stands for manganese; and n is 0 or an integer of not less than 1. As to the substituents R 4 and R 9 of the aromatic rings Z, examples of the halogen atom are bromine, chlorine, and fluorine, and examples of the alkyl group are C 1-6 alkyl groups such as methyl, ethyl, propyl, butyl, and t-butyl group. Examples of the alkoxy group are C 1-6 alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy groups. The substituents R 4 and R 9 are usually hydrogen atoms, C 1-4 alkyl groups, or hydroxymethyl groups. In the complex shown by the above formula, n is 0 or an integer of not less than 1 (e.g., 1 to 5, particularly 1 or 2). In the above complex, m+1 mole of the N,N'-disalicylidene ethylene diamine is coordinated to m mole of manganese (m is an integer of not less than 1), and thus the complex is structurally different from a conventional manganese complex in which 1 mole of the N,N'-disalicylidene ethylene diamine is coordinated to 1 mole of manganese. Moreover, in contrast to the conventional manganese complex being noncrystalline (amorphous), the complex used in the present invention is crystalline and shows a clear melting point in accordance with a thermal analysis by TC/TDA. The melting point of the complex is usually 190 to 240°C and particularly 200 to 220°C. Moreover, the complex used in the present invention can be distinguished from conventional manganese complexes by whether there is an absorption peak for the hydroxyl group in the infrared absorption spectrum or not. [Production process of complex] The above complex can be obtained by coordinating an excess amount of an N,N'-disalicylidene ethylenediamine with a manganese compound. As the manganese compound, there may be exemplified organic acid salts (e.g., acetates), halides (e.g., manganese chloride), and inorganic acid salts. The proportion of the N,N'-disalicylidene ethylene diamine relative to the manganese compound is 0.5 to 5, preferably 0.9 to 3, and particularly 1 to 2 (molar ratio). Even if the proportions are almost equimolar with each other, a complex in which a substantially excess mole of an N,N'-disalicylidene ethylene diamine is coordinated can be obtained by liberating or separating a manganese compound though deteriorated in yield. The reaction may be conducted in an inert solvent (e.g., an organic solvent such as an alcohol). Practically, the reaction is carried out in an atmosphere of an inert gas and can be effected usually with stirring at a temperature within the range of 70°C to a reflux temperature of a solvent. The complex can be obtained by recovering or collecting the reaction product and, if needed, purifying by a recrystallization technique, and drying. [Basic nitrogen-containing compound] The combination of the above complex and the basic nitrogen-containing compound gives an oxidation catalyst having a higher activity and remarkably improves the conversion of the substrate (β-isophorone) and the selectivity of the object oxide (ketoisophorone). The nitrogen-containing compound is an alicyclic or aromatic cyclic base selected from 1,4-diazabicyclo[2.2.2]octane (DABCO), 4-dimethylaminopyridine, 2-dimethylaminopyridine and 1,10-phenanthroline. The proportion of the basic nitrogen-containing compound relative to the above complex (the former/the latter) can suitably be selected from the range of 0.1/1 to 500/1 (molar ratio) and preferably 0.5/1 to 250/1 (e.g., 0.8/1 to 250/1). [Oxidation reaction] By oxidizing the substrate (β-isophorone) with molecular oxygen using the oxidation catalyst, the corresponding oxide (Ketoisophorone) can be produced in high yield even if the concentration of the substrate in a reaction system is high. Moreover, its high activity permits a remarkable decrease in the amount of the oxidation catalyst as compared to conventional manganese complexes, and therefore an oxide can be produced with high conversion and high selectivity even in the presence of an exceedingly minute amount of the oxidation catalyst. Further, since the oxide can be produced with high conversion and high selectivity even if the concentration of oxygen is low, air or the like can also be used as an oxygen source. [Amount of Catalyst] The amount of the oxidation catalyst to be used is, for example, 0.001 to 5 parts by weight, preferably 0.01 to 1 part by weight, and more preferably 0.05 to 0.5 part by weight, relative to 100 parts by weight of β-isophorone. The amount of each constituent of the oxidation catalytic system relative to 1 mole of β-isophorone is as follows. Complex: 1 x 10 -5 to 1 x 10 -2 mole (preferably, 1 x 10 -2 to 0.5 mole) Basic nitrogen-containing compound: 5 x 10 -2 to 1 mole (preferably, 1 x 10 -2 to 0.5 mole). [Substrate] The substrate used in the present invention is β-isophorone (3,5,5-trimethylhex-3-ene-1-one). The concentration of the substrate in the reaction system is 20 to 50% by weight. The oxidation can be effected with retaining or maintaining a selectivity of 90% or higher (e.g., a selectivity of 93 to 97%), and therefore, the oxidation process of the present invention has great advantages and is remarkably useful in view of industry. In the present invention, in addition to oxygen and oxygen-containing gases, a compound generating molecular oxygen is also employed as an oxygen source so far as capable of providing molecular oxygen. As the oxygen source, highly pure oxygen or a high oxygen content gas may be used, the oxygen gas diluted with an inert gas, e.g., nitrogen, helium, argon, or carbon dioxide is preferably supplied to the reaction system. Moreover, with the oxidation catalytic systems used in the present invention, the substrate can be oxidized effectively even with air instead of oxygen as the oxygen source. The use of air as the oxygen source is not only highly advantageous in view of economics but also reduces the danger of explosions encountered in industrialization. The oxygen concentration of the oxygen source is, for example, 5 to 100% by volume, preferably 5 to 50% by volume, and particularly 7 to 30% by volume. Even at such a low oxygen concentration as of 8 to 25% by volume, the oxidation effectively proceeds. When supplying molecular oxygen to a reaction vessel or container, the reaction may be carried out in a closed system with enough molecular oxygen previously supplied, or may be conducted in a continuous stream of molecular oxygen. In the case of a stream of molecular oxygen, the flow rate is, for example, 0.1 to 10L/min and preferably 0.5 to 5L/min per unit volume (1L) of the vessel. As the reaction solvent, ketones (particularly, dialkyl ketones) such as methyl ethyl ketone and dibutyl ketones (e.g., diisobutyl ketone, di-t-butyl ketone) are used. Dialkyl ketones are preferable, and dibutyl ketones are particularly preferred. The amount of the solvent to be used is not particularly restricted and may be selected from within the range of 5 to 70% by weight and preferably 15 to 60% by weight (e.g., 20 to 55% by weight). The proportion of the water content in the reaction system can be selected from within the range not adversely affecting on the reaction such as inactivation of the catalytic system, and is 1% by weight or less (0.001 to 1% by weight) and preferably 0.5% by weight or less (0.001 to 0.5% by weight). Despite acceleration of the reaction at the initial stage, the water content exceeding 1% by weight results in a subsequent cessation of the reaction or a decrease in selectivity. The water in the reaction system includes not only the water contained at the beginning or initial stage of the reaction but also the water produced by the reaction, In the present reaction system, there is usually present a finite amount of water. It is desirable that the water produced by the reaction is removed from the system. The amount of the produced water varies with the concentration of β-isophorone substrate, and the amount of the water to be removed is at least 30% by weight, preferably at least 50% by weight, and more preferably at least 80% by weight, relative to the total amount of the water produced. The reaction temperature can be selected from within the range of, e.g., 10 to 100°C (preferably 20 to 60°C) according to the reaction rate, selectivity, and the solvent to be used. The reaction can be conducted either at atmospheric pressure or under applied pressure [to about 150 atm (152 x 10 5 Pa)] and preferably at atmospheric pressure. The reaction time (or residence time) is not particularly restricted and can be selected from within the range of 10 seconds to 24 hours, depending upon the system of the reaction (e.g., a continuous system or a batch system). The reaction can be carried out in a conventional system such as a batch system, a semi-batch system, or a continuous system. In the continuous system, portions of the catalyst are continuously or intermittently removed from a reactor for regeneration, and the regenerated catalyst (i.e., a complex of manganese with an N,N'-disalicylidene ethylenediamine may be recycled to the reactor to be reused. In the batch system, the catalyst or the constituents of the catalyst may be separated and recovered from a reaction product after completion of the reaction, wholly or partially regenerated and may be reused repeatedly as a catalyst for the reaction. The oxide produced by the reaction (ketoisophorone) can easily be separated and purified with a conventional separation technique such as filtration, condensation, distillation, extraction, crystallization, recrystallization and column chromatography, or a combination thereof. Particularly, according to the present invention, the conversion of β-isophorone and the selectivity of ketoisophorone can be significantly improved, and the production of by-product(s) is remarkably inhibited. Therefore, even though the separation and purification step is required of ketoisophorone, ketoisophorone can be separated and purified with easiness and efficiency, and therefore need not be highly separation-purified. According to the present invention, the substrate can be oxidized with high conversion and high selectivity regardless of its concentration by using the crystalline manganese complex of manganese with the N,N'-disalicylidene ethylene diamine. Moreover, even if the amount of the catalyst is extremely minute, the substrate can be oxidized with high conversion and high selectivity. Further, even when the oxygen concentration of the molecular oxygen source is low as in the case of air, the oxidation catalyst used in the present invention proceeds efficiently an oxidative reaction. Therefore, when the catalyst used in the present invention is applied to the oxidation of β-isophorone, even if the concentration of β-isophorone is high and the oxygen concentration is low, ketoisophorone can be produced with retaining high conversion and selectivity. Particularly, even in the reaction system with a high β-isophorone concentration, it is possible to maintain high selectivity and produce ketoisophorone with an improved efficiency. EXAMPLES The following examples are intended to show the present invention in further detail. The substrate, manganese complex, nitrogen-containing compounds, and the solvent used in the Examples and Comparative Examples are as follows. 1. Substrate: β-isophorone (β-IP) 2. Manganese complex (b-1): crystalline manganese complex A reactor was fed with 169g (630 mmol) of the N,N'-disalicylideneethylenediamine (EDSA) and 5,000 ml of methanol, and the EDSA was dissolved at a reflux temperature under a nitrogen stream. According to the method recited in Inorg. Synth. 3 (1950) 196, N,N'-disalicylideneethylenediamine (EDSA) had been synthesized by refluxing 2 mol of salicylaldehyde and 1 mol of ethylenediamine in ethanol for 6 hours. A solution of 156 g (637 mmol) of manganese acetate · tetrahydrate Mn (OAc) 2 · 4H 2 O and 1,500 ml of methanol was added to the above-described solution of EDSA in methanol at 50°C in a nitrogen stream, and the mixture was reacted at a reflux temperature in a nitrogen stream for 8 hours. After the completion of the reaction, the mixture was allowed to stand overnight in an atmosphere of nitrogen to be cooled, and stored in a container (or vessel) in which a nitrogen gas is flowing. With a nitrogen gas flowing through the container, the mixture was filtered and dried in vacuo at 80°C for 6 hours to obtain 135.4 g of crystals (yield: 70%). Thermal analysis (TC/TDA) of the crystalline complex showed the melting point of 207.8°C. Elemental analysis Found C:65.5, H: 5.2, N: 9.5 Calculated C:65.2, H: 5.1, N: 9.5 (corresponding to the above formula in which n = 0) Calculated C:63.3, H: 4.9, N: 9.2 (corresponding to the above formula in which n = 0) (b-2): Noncrystalline manganese complex A manganese complex was obtained according to the method recited in the J. Am. Chem. Soc., 108 (1986) 2317. In other words, to a mixed solution of 2.15 g (8 mmol) of EDSA and 50 ml of methanol was added a solution of 0.90 g (16 mmol) of potassium hydroxide and 20 ml of methanol. Thereafter, to the resultant mixture was added a solution of 1.98 g (8.08 mmol) of manganese acetate · tetrahydrate Mn (OAc) 2 · 4H 2 O and 30 ml of methanol in a nitrogen stream, and the reaction mixture was refluxed at a reflux temperature for 5 hours. Thereafter, the reaction mixture was cooled to room temperatures taking 2 hours, and then filtered. The cake or residue was washed with 10 ml of methanol, and filtered, and dried in vacuo at 100°C for 8 hours to obtain a manganese complex. Thermal analysis (TC/TDA) of the manganese complex showed no clear endoergic peak and revealed the complex to be noncrystalline (amorphous). The melting point of the sole EDSA was 127.6°C. Elemental analysis Found C: 59.6, H: 4.3, N: 8.7 Calculated C: 59.8, H: 4.4, N: 8.7 3. Nitrogen-containing compound (c-1): 1,4-diazabicyclo[2.2.2]octane (DABCO) (c-2): 4-dimethylaminopyridine (c-3): 2-dimethylaminopyridine (c-4): 1,10-phenanthroline (c-5): triethylamine 4. Solvent: diisobutyl ketone Examples 1 to 7 and Comparative Examples 1 to 3 An 1L glass reactor equipped with a mechanical stirrer with turbine blades and a molecular oxygen gas inlet tube having a porous glass unit was fed with β-isophorone, a manganese complex, a nitrogen-containing compound, and the solvent in proportions shown in Table 1, and the reaction was carried out with an oxygen-containing gas (oxygen concentration, volume%) flowing at a constant flow rate. The conversions of β-isophorone and the selectivities of ketoisophorone from β-isophorone in Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 1 with the reaction conditions. As obvious from Tables 1 and 2, even if the concentration of β-isophorone is high and the oxygen concentration is low, the conversion and selectivity can be largely improved in the Examples as compared with the Comparative Examples. Further, even if the concentration of a manganese complex is small, ketoisophorone can be formed with high activities.

Claims: A process for producing ketoisophorone, which comprises oxidizing β-isophorone with molecular oxygen in the presence of an oxidation catalyst comprising a crystalline complex of manganese with an N,N'-disalicylidene ethylenediamine, and a basic nitrogen-containing compound, wherein m+1 mole of said N,N'-disalicylidene ethylenediamine is coordinated to m mole of said manganese and m is an integer of not less than 1, and the infrared spectrum of said complex indicates an absorption peak for the hydroxyl group, said nitrogen-containing compound being an alicyclic or aromatic cyclic base selected from 1,4-diazabicyclo[2.2.2]octane (DABCO), 4-dimethylaminopyridine, 2-dimethylaminopyridine and 1,10-phenanthroline, said oxidation being carried out, in a ketone solvent, in a concentration of 20 to 50% by weight of β-isophorone in the reaction system and the water content of the reaction system is not more than 1 % by weight. The process of claim 1, wherein the amount of the complex is 1x10 -5 to 1x10 -2 mole relative to 1 mole of β-isophorone. The process of claim 1, wherein the melting point of said complex is 200 to 220°C. The process of claim 1, wherein the proportion of said nitrogen-containing compound relative to said complex is 0.1/1 to 500/1 (molar ratio).

Inventors: SHIBATA HIKARU, TAKAHASHI IKUO, SHIBATA, HIKARU, TAKAHASHI, IKUO
Applicants: DAICEL CHEM, DAICEL CHEMICAL INDUSTRIES, LTD.
Application year: 1999
Main classification: B01J31
IPC codes: C07C49, C07B61, C07C45, B01J31