JPS61186388A - Reduction of armatic nitro compound - Google Patents

Abstract

PURPOSE:A combination of a copper catalyst with a specific amount of an iron group metal is used to effect the reduction of an aromatic nitro compound with a metal borohydride to improve the conversion and selectivity and produce the corresponding amino compound in high yield. CONSTITUTION:An aromatic nitro compound, preferably nitrophthalide is reduced with a metal borohydride such as NaBH4, NaBH3CN, NaBH2S2 in the coexistence of a copper catalyst and 300-6,000ppm of an iron-group metal, preferably iron, nickel or cobalt to give the corresponding amino compound.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for reducing aromatic nitro compounds), and more specifically, reducing aromatic nitro compounds with metal boron hydrides to produce the corresponding amino compounds. This invention relates to improvements in manufacturing methods.

[Conventional technology]

It is generally known to reduce aromatic nitro compounds with metal boron hydrides to produce the corresponding amine compounds. It is also known to use, for example, a copper catalyst as the reduction catalyst in this case. However, when reducing aromatic nitro compounds with metal boron hydrides in the presence of a copper catalyst, the conversion rate of the raw nitro compound and the selectivity of the target amine compound may be insufficient depending on the target nitro compound. It wasn't something. In particular, this tendency is remarkable when reducing nitro phthalide compounds. As a result of various studies on methods for obtaining the desired amino compound in high yield by improving the conversion rate and selectivity during reduction with metal boron hydrides in the presence of They discovered this and completed the present invention.

That is, the gist of the present invention is to provide a method for producing a corresponding amino compound by reducing an aromatic nitro compound with a metal boron hydride in the presence of a copper catalyst.
A method for reducing an aromatic nitro compound characterized by the presence of iron scrap metal of 3θ0N400θppm.

[Structure of the invention]

The present invention will be explained in detail below.

(Aromatic nitro compound) Aromatic nitro compounds targeted by the present invention usually include mononitro compounds, and specific examples thereof include:
nitrobenzene, nitrotoluene, nitrophthalide,
Nitroquinoline, nitroxylene, nitronaphthalene,
Examples include nitrocresol and nitrobenzoic acid.

In the present invention, when a nitrophthalide compound is used, 1
It is preferable because the effect is remarkable. Further, the nitrophthalide compound may be a derivative thereof, and for example, a nitrophthalide derivative represented by the following general formula can also be used.

(In the above formula, R represents a hydrogen atom, an alkyl group, or an alkoxy group, and n represents an integer of θ to 3) (Reducing agent) In the present invention, metal boron hydride is used as a reducing agent. , a specific example of this is, for example, NaBH
,,LiBH,,NaBHlON,NaBHlS,
, MaBH(OOHs)! , NaB! ! ,(OB),K
Examples include BB, , 0a(BH,), and the like. The amount of this reducing agent used is usually, for aromatic nitro compounds,
/, 1 to 3 times the mole, preferably to! If the amount used is less than atb, the nitro group cannot be reduced sufficiently, and conversely, if it is too much, the effect will not change, so it is not economical. This reducing agent is usually used in a state dissolved in an aqueous or alcoholic solution of caustic alkali.

(Catalyst) Although a copper catalyst is used in the present invention, this copper catalyst can be used as a metal or a compound thereof. Examples of the compound include inorganic acid salts such as hydrochloride and sulfate, organic acid salts such as acetate, complexes such as phosphine complex, pyridyl complex, and cetylacetone complex. Examples include hydroxides and oxides. The most preferred of these catalysts are metal or inorganic acid salts. The amount of these catalysts used is usually θ, / ~ 4 as metal relative to the aromatic nitro compound.
If the amount of toilet waste (tO%, preferably 1 to 10 mol) is too small, the reduction reaction will not proceed well.
Moreover, even if there are many, the effect will be less than that, so it is not economical.

In the present invention, it is essential to use an iron group metal together with the copper catalyst described in □ above. That is, the addition of this iron group metal further increases the catalytic activity of the copper catalyst9, making it possible to obtain the desired amino compound in high yield.

Iron group metals typically include iron, nickel, or cobalt, with nickel being particularly preferred. These metal components are usually used as metals or compounds, but
Examples of the compound include those similar to the above-mentioned copper compounds, and the sulfur cfR salt form is usually desirable.

The amount of iron group metal used is 3θ as a metal compared to steel.
θ~6000ppm, preferably! 00～! 000
ppm, and if the amount of this supplement is too small, the desired effect will not be obtained, and on the other hand, if it is too large, the selectivity will decrease and the desired amino compound cannot be obtained in high yield. .

(Reaction Solvent) The reduction reaction of the present invention is usually carried out in a solvent or an aqueous solution thereof, and examples of this solvent include aliphatic alcohols such as methanol, ethanol, and propyl; diglyme, tetrahydrofuran, etc. ether;
Examples include dimethylformamide, dimethyl sulfoxide, and aqueous solutions thereof, and among them, aliphatic alcohols are most preferred. The amount of these solvents used is typically λ~! for aromatic nitro compounds. O times the weight, preferably 3~
−〇 times the weight.

(Reaction Conditions) Since the reduction reaction of the present invention proceeds well under normal pressure, there is no need to carry out the reaction under increased pressure which requires a pressure-resistant reactor, and it is usually industrially desirable to carry out the reaction under normal pressure. Depending on the circumstances, it may be carried out under pressure. In addition, the reaction temperature is usually θ°C to 100°C, preferably j°C to to°C; if this temperature is too low, the reaction rate is slow and the desired amino compound cannot be obtained efficiently. On the other hand, if it is too high, more by-products will be produced, which is not preferable. The reaction time is usually 10 minutes to 10 minutes.

(Operating Procedures) As a method for carrying out the present invention, for example, an aromatic nitro compound as a raw material, an organic solvent, and a catalyst are charged into a reactor, and while being kept at a predetermined temperature while stirring, an organic solvent is added as needed. This can be done by dropping the reduced solution diluted with water. Since the reaction of the present invention is an exothermic reaction, it is desirable to adjust the temperature of the reducing agent dropwise in accordance with the heat removal from the reaction system so that the temperature within the system is maintained within a certain range.

〔Effect of the invention〕

According to the present invention, the conversion rate of raw materials and the selectivity of the target amino compound when reducing aromatic nitro compounds, especially heptanonitrophthalides, with metal boron hydrides using a copper catalyst are increased. The desired amino compound can be obtained in high yield.

〔Example〕

Next, the present invention will be explained in more detail with reference to the embodiments of the present invention, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 7 ~ Da and Comparison f[l/-,,2 Into a -00-glass reactor equipped with a stirrer and a temperature controller, mononitrophthalides represented by the following structural formula were added.
mmol), nickel sulfate and copper sulfate in the proportions shown in Table 1. Prepare rI 77 (3.1 mmol) and methanol♂ornt, 3! 3. Sodium borohydride was added to this under stirring while maintaining the temperature at 3.5°C. rI (100mm
A solution prepared by dissolving /Pi caustic soda methanol solution Jjtnt was added dropwise over a period of 1 hour, and stirring was further continued at the same temperature for 7 hours to carry out the reaction.

In the method described above, the product in the reaction mixture was analyzed to determine the conversion rate and the selectivity of the corresponding amino compound, and the results shown in Table 1 were obtained.

Chapter/Table

Claims (3)

[Claims] (1) In a method for producing a corresponding amino compound by reducing an aromatic nitro compound with a metal boron hydride in the presence of a copper catalyst, the amount of
1. A method for reducing an aromatic nitro compound, characterized by the presence of m iron group metals. (2) The method according to claim 1, wherein the iron group metal is iron, nickel, or cobalt. (3) The method according to claim 1, wherein the aromatic nitro compound is a nitrophthalide compound.