JPH0550501B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to a method for producing aminobenzoic acids from nitrobenzoic acids by catalytic reduction. ``Prior Art'' Demand for aminobenzoic acids has been increasing in recent years as raw materials for pharmaceuticals, agricultural chemicals, cosmetics, and resin production, and as curing agents for resins. A common method for producing aminobenzoic acids is to catalytically reduce nitrobenzoic acids in the presence of hydrogen and a Raney-nickel catalyst in an alcoholic solvent such as methanol. A method of catalytic reduction using dimethylformamide as a solvent is also known, but since these solvents are freely miscible with the water produced in the catalytic reduction reaction, a large amount of thermal energy is required to recover these solvents after the reaction is completed. The necessary distillation operations must be carried out. Furthermore, when catalytic reduction is carried out using a normal Raney-nickel catalyst, side reactions other than the desired reaction preferably occur. The generated amino group reacts with alcohol as a solvent to generate an N-alkylamino compound, or a transesterification reaction occurs to generate impurities. On the other hand, in the case of catalytic reduction using a hydrocarbon compound that is practically insoluble in water as a solvent, the aminobenzoates produced are difficult to dissolve in the hydrocarbon solvent, so it is not only easy to separate the target product, but also to remove the solvent. Regarding post-treatment, there is an advantage that water generated by liquid-liquid separation can be easily removed. However, the method of carrying out a catalytic hydrogenation reaction in a hydrocarbon solvent that is virtually insoluble in water using a Raney-nickel catalyst has a very slow reaction rate and is therefore not an industrially advantageous method. Further, even if the reaction is carried out by adding a quaternary ammonium salt, an emulsifier, etc. to the above-mentioned hydrocarbon solvent, there are many disadvantages such as coloring of the reaction liquid, separation property of the reaction waste liquid, foaming, and quality. Note that if a noble metal catalyst is used instead of the Raney-nickel catalyst, the reaction rate will be improved, but since the noble metal itself is expensive, this method cannot be said to be industrially advantageous. "Problems to be Solved by the Invention" Industrial production of nitrobenzoic acids using a hydrocarbon solvent that is virtually insoluble in water, which is easily separated from water produced by catalytic reduction, and an inexpensively available Raney-nickel catalyst. It has been desired to develop a method for catalytic reduction under favorable conditions. "Means for Solving the Problems" As a result of our earnest efforts to solve the above-mentioned problems, the present inventors added sulfur or sulfur compounds during the reduction reaction of nitrobenzoic acids, or added sulfur or sulfur compounds to the Raney-nickel catalyst. Surprisingly, by poisoning, it is possible to not only increase the reaction rate to a level that is industrially satisfactory, but also to produce the desired aminobenzoic acids with high purity and high yield. The present invention was completed by discovering that the following can be obtained. That is, the present invention has the formula (In formula (1), X is a hydrogen atom, a chlorine atom, a bromine atom, a hydroxyl group, a methoxy group, or a _C1-5 alkyl group, and R is an amino group, a _C1-8 alkoxy group, a _C3-6
alkoxyalkoxy group, NHC ₂ H ₄ N(CH ₃ ) ₂
group, NHC ₂ H ₄ N (C ₂ H ₅ ) ₂ groups, OC ₂ H ₄ N (CH ₂ ) ₂ groups,
2 OC ₂ H ₄ N (C _{2 H 5} ) or represents a group. ) in a hydrocarbon solvent that is virtually insoluble in water, which may coexist with water, in the presence of sulfur or a sulfur compound and a Raney nickel catalyst, or using a Raney nickel poisoned with a sulfur compound. By hydrogenating the formula (In formula (2), X has the same meaning as above, _R ' is an amino group, a _C1-8 alkoxy group, a _C3-6 alkoxyalkoxy group, _NHC2H4N ( _CH3 ) ₂ group,
NHC ₂ H ₄ N (C ₂ H ₅ ) ₂ groups, OC ₂ H ₄ N (CH ₃ ) ₂ groups,
2 OC ₂ H ₄ N (C _{2 H 5} ) or represents a group. ) to produce aminobenzoic acids represented by Examples of sulfur or its compounds that are added to the reaction solution or used to poison the Raney-nickel catalyst in the present invention include the following. ●Free sulfur ●Acid sulfites: sodium acid sulfite, potassium acid sulfite ●Soda sulfides: sodium disulfide, sodium pentasulfide,
Other polysulfides ● Thiosulfates: Sodium thiosulfate, potassium thiosulfate ● Thiocyanates: Sodium thiocyanate, potassium thiocyanate ● Pyrosulfates: Sodium pyrosulfate, potassium pyrosulfate ● Alkyl sulfides: Methyl sulfide, Ethyl sulfide ●Mercaptans: Methyl mercaptan, ethyl mercaptan, thiophenol Other sulfur trioxide, carbon disulfide, hydrogen sulfide,
Thiourea, dimethyl sulfoxide, sulfolane,
Inorganic and organic sulfur compounds such as mercaptobenzothiazole and benzothiazole can also be used. The amount of the sulfur or sulfur compound added to the reaction solution is 0.1 per 1000 parts of Raney nickel metal.
The amount used is preferably 1 to 500 parts, more preferably 1 to 500 parts. In the present invention, the Raney-Nikkol catalyst can also be poisoned using sulfur or a sulfur compound, and the poisoned catalyst can be obtained, for example, as follows. The Raney nickel catalyst used is generally a nickel-aluminum alloy, and some contain several percent of other metals, such as iron and chromium. Raney nickel catalysts may be used as is. This developed aqueous paste of Raney nickel is suspended in pure water, and while stirring,
0.1 to 1000 parts per 1000 parts by weight of nickel metal,
More preferably, sulfur or a sulfur compound is added in a range of 1 to 200 parts by weight, and 1 to 200 parts by weight are added at any temperature of 0 to 90°C.
Treat for 120 minutes to obtain a poisoned aqueous paste of Raney nickel catalyst. Poisoning treatment methods include adding sulfur or sulfur compounds as they are or their aqueous solutions or water/slurry liquids to an aqueous suspension of Raney nickel catalyst under stirring, or adding Raney nickel to an aqueous solution or water/slurry of sulfur or sulfur compounds. Methods such as adding an aqueous paste of the catalyst under stirring are used. If conditions such as the amount of water used during the poisoning treatment, the method of adding sulfur or sulfur compounds, the treatment temperature, and the treatment time are kept constant, there will be no noticeable difference in the poisoning effect, so the poisoning effect can be reproduced. The quality is high. The amount of Raney nickel catalyst used can be selected arbitrarily, but usually nitrobenzoic acids
The range is preferably 1 to 50 parts by weight, more preferably 0.1 to 100 parts by weight of nickel metal per 100 parts by weight. Examples of the nitrobenzoic acids of formula (1) to which the method of the present invention is applied include o, m, p-nitrobenzoic acid methyl ester, o, m, p-nitrobenzoic acid ethyl ester, o, m, p- Nitrobenzoic acid
m-propyl ester, o,m,p-nitrobenzoic acid-m-butyl ester, o,m,p-nitrobenzoic acid amyl ester, 3-methyl-4-nitrobenzoic acid ethyl ester, 3-chloro-4- Nitrobenzoic acid iso-propyl ester, 2-methoxy-3-nitrobenzoic acid methyl ester, 2-
Hydroxy-4-nitrobenzoic acid amyl ester, 3-nitrobenzoic acid benzyl ester, 4-
Nitrobenzoic acid β-diethylaminoethyl ester, 4-nitrobenzoic acid β-butoxyethyl ester, bis-(4-nitrobenzoxy)-1,
Examples include 3-propane, 3-nitrobenzamide, 4-nitro-N-(β-diethylaminoethyl)-benzamide, and the like. In the present invention, nitrobenzoic acids can be charged into the reaction system all at once or sequentially. Here, "sequentially" means that the nitrobenzoic acids are continuously or intermittently introduced into the reaction system while the reaction is in progress, either as is or dissolved in a solvent. Examples of hydrocarbon solvents that are virtually insoluble in water used in the present invention include saturated aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons that may be substituted with alkyl groups or halogen groups. can give. Specific examples include n-pentane, n-hexane, isohexane, cyclohexane, methylcyclohexane, benzene, toluene, ethylbenzene, xylene, isopropylbenzene, chlorobenzene, o-dichlorobenzene, and the like. The amount of these solvents to be used is about 1/3 to 10 times the amount of nitrobenzoic acids, which is convenient in terms of removing reaction heat and separating the catalyst. Even if a small amount of water is mixed in the reaction solvent, there is no problem in carrying out the method of the present invention. The reaction in the method of the present invention is carried out at any temperature between room temperature and 200°C, preferably between 40 and 150°C. The reaction pressure may be any pressure between normal pressure and 100 kg/cm ² gauge, preferably 1 to 20 kg/cm ² gauge. The progress of the reaction can be checked by the amount of hydrogen absorbed. After the reaction is completed, the catalyst is removed by sedimentation or filtration, water is removed by liquid separation, and the crystals are taken out by cooling, or if necessary, a portion of the solvent is distilled off to obtain crystals. The liquid can be used as a solvent for the next reaction as it is without performing any distillation operation or the like. For those that do not crystallize at room temperature, the desired product can be obtained by distilling off the solvent and performing a distillation operation, if necessary. "Effects of the Invention" The method of the present invention allows easy separation of liquids after reaction.
High-purity nitrobenzoic acids can be obtained from nitrobenzoic acids in good yield using a hydrocarbon solvent that is virtually insoluble in water and an inexpensively available Laraney Nickel catalyst. "Example" The present invention will be described in further detail with reference to Examples below. Example 1 100 g of Raney nickel catalyst and 500 c.c. of water were placed in a 1000 c.c. beaker containing a stirring bar, and the mixture was stirred at room temperature.
5.8 g of acidic sodium sulfite was added and stirred for 60 minutes.
Thereafter, the vessel was tilted and the supernatant water was discarded to obtain a poisoned Raney nickel catalyst. 3.0 g of this poisoned Raney nickel catalyst, 100 g of p-nitrobenzoic acid ethyl ester, and 150 c.c. of toluene were placed in a 500 cc. Pressure 10Kg/cm ² gauge, reaction temperature reached 100℃
Hydrogen is continuously supplied during the reaction in which hydrogen reduction is carried out at 1000 rpm. Hydrogen absorption completely stopped 48 minutes after the start of the reaction. Subsequently, the mixture was cooled and allowed to stand, and the catalyst was separated to obtain a toluene-water reaction liquid. The reaction solution was transferred to a separatory funnel, and after separating the water, the toluene phase was cooled to 0° C. and the precipitated crystals were filtered to obtain 80.1 g (purity 100.0%) of p-nitrobenzoic acid ethyl ester. Example 2 The procedure of Example 1 was followed except that 5.8 g of sodium acid sulfite was replaced with 2.2 g of sodium thiosulfate. In a reaction time of 63 minutes, 80.2 g (purity 100.0%) of p-aminobenzoic acid ethyl ester was obtained. Example 3 The procedure of Example 1 was followed except that 80 g of p-nitrobenzoic acid methyl ester was used instead of 100 g of p-nitrobenzoic acid ethyl ester. p-aminobenzoic acid methyl ester in a reaction time of 85 minutes
64.0g (purity 100.0%) was obtained. Example 4 p-nitrobenzoic acid-iso-amyl ester instead of 100 g p-nitrobenzoic acid ethyl ester
The reaction was carried out according to the procedure of Example 1 using 100 g. Reaction time: 44 minutes. Toluene is distilled off from the toluene phase obtained by separating water, and p-aminobenzoic acid-
83.8 g of iso-amyl ester (purity 99.9%) was obtained. Example 5 A reaction was carried out according to the procedure of Example 1 using 150 c.c. of n-pentane instead of 150 c.c. of toluene. Reaction time 71 minutes. N-pentane was distilled off from the n-pentane phase obtained by separating water to obtain 82.1 g (purity 99.9%) of p-aminobenzoic acid ethyl ester. Examples 6 to 18 Reactions were carried out in the same manner as in Example 1 using Raney nickel poisoned with sulfur or various sulfur compounds.

[Table] Comparative example 1 Poisoned Raney nickel catalyst 30 used in Example 1
Non-poisoned Raney nickel catalyst 3.0 instead of g
A reaction was carried out in the same manner as in Example 1 using g. Even after 8 hours, hydrogen was still absorbed. At that time, analysis of the reaction solution by gas chromatography revealed that p-aminobenzoic ethyl ester was 91.5%.
The content was 7.3% p-nitrobenzoic acid ethyl ester and 1.2% others. Comparative Example 2 Example 1 except that 80 g of p-nitrobenzoic acid methyl ester was used instead of 100 g of p-nitrobenzoic acid ethyl ester, and 3.0 g of unpoisoned Raney nickel was used instead of 3.0 g of poisoned Raney nickel catalyst. I followed the instructions. Hydrogen was absorbed even though it took 8 hours. Analysis of the reaction solution by gas chromatography at that time revealed that it contained 71.6% p-aminobenzoic acid methyl ester, 27.3% p-nitrobenzoic acid methyl ester, and 1.1% others.

Claims (1)

[Claims] 1 Formula (1) (In formula ₍ 1 ₎ ,
_C3-6 alkoxyalkoxy group _{, NHC2H4N}
(CH ₃ ) ₂ groups, NHC ₂ H ₄ N (C ₂ H ₅ ) ₂ groups, OC ₂ H ₄ N
(CH ₃ ) ₂ groups, OC ₂ H ₄ N (C ₂ H ₅ ) ₂ groups, or represents a group. ) in a hydrocarbon solvent that is practically insoluble in water, where water may coexist, in the presence of sulfur or a sulfur compound and a Raney nickel catalyst, or by using Raney nickel poisoned with sulfur or a sulfur compound. A formula characterized by catalytic hydrogenation (In formula (2), X has the same meaning as above, _R ' is an amino group, a _C1-8 alkoxy group, a _C3-6 alkoxyalkoxy group, _NHC2H4N ( _CH3 ) ₂ group,
NHC ₂ H ₄ N (C ₂ H ₅ ) ₂ groups, OC ₂ H ₄ N (CH ₃ ) ₂ groups,
2 OC ₂ H ₄ N (C _{2 H 5} ) or represents a group. ) Process for producing aminobenzoic acids represented by