阅读说明：本技术 一种利用碱土金属氢化物催化还原硝基化合物制备氨基化合物的方法 (Method for preparing amino compound by catalytic reduction of nitro compound by using alkaline earth metal hydride ) 是由 李恒 袁冰芯 李龙甲 于 2020-06-03 设计创作，主要内容包括：本发明涉及一种利用碱土金属氢化物催化还原硝基化合物制备氨基化合物的方法,属于有机合成技术领域。该方法以硝基化合物为反应底物,碱土金属氢化物为氢源,联硼酸酯为催化剂,将三者分别加入到有机溶剂中,搅拌加热进行反应,反应温度为50-150℃,反应时间为3-20 h；反应结束后对反应母液进行分离提纯得到氨基化合物。本发明合成步骤简单,反应条件温和,避免了高压氢气的使用,而且在反应过程中无过渡金属参与,不仅降低了反应成本且绿色环保,减少环境污染。(The invention relates to a method for preparing an amino compound by catalytic reduction of a nitro compound by using an alkaline earth metal hydride, belonging to the technical field of organic synthesis. The method comprises the steps of taking a nitro compound as a reaction substrate, taking an alkaline earth metal hydride as a hydrogen source and taking diborate as a catalyst, respectively adding the nitro compound, the alkaline earth metal hydride and the diborate into an organic solvent, stirring and heating to react at the temperature of 50-150 ℃ for 3-20 h; and after the reaction is finished, separating and purifying the reaction mother liquor to obtain the amino compound. The method has the advantages of simple synthesis steps, mild reaction conditions, avoidance of high-pressure hydrogen, no transition metal in the reaction process, reduction of reaction cost, environmental friendliness and reduction of environmental pollution.)

1. A method for preparing amino compound by catalytic reduction of nitro compound with alkaline earth metal hydride, the reaction formula is as follows, characterized in that: the method comprises the following steps:

step (1): respectively adding nitro compounds serving as reaction substrates, alkaline earth metal hydrides serving as hydrogen sources and diborate serving as catalysts into an organic solvent, and stirring and heating the mixture to perform reaction; the reaction temperature is 50-150 ℃, and the reaction time is 3-20 h;

step (2): and after the reaction is finished, carrying out post-treatment, separation and purification to obtain the amino compound.

2. The method for preparing an amino compound by catalytic reduction of a nitro compound with an alkaline earth metal hydride according to claim 1, wherein: and R is aryl or aromatic heterocyclic radical.

3. The method for preparing an amino compound by catalytic reduction of a nitro compound with an alkaline earth metal hydride according to claim 2, wherein: the nitro compound is 3-nitrotoluene, 4-nitrochlorobenzene or 2-nitropyridine.

4. The method for preparing an amino compound by catalytic reduction of a nitro compound with an alkaline earth metal hydride according to claim 2, wherein: the alkaline earth metal hydride is any one of sodium hydride, potassium hydride and calcium hydride.

5. The method for preparing an amino compound by catalytic reduction of a nitro compound with an alkaline earth metal hydride according to claim 2, wherein: the diborate is any one of diboronic acid pinacol ester, bis (2, 4-dimethyl-2, 4-pentanediol) borate, diboronic acid neopentyl glycol ester and bis pyrocatechol borate.

6. The method for preparing an amino compound by catalytic reduction of a nitro compound with an alkaline earth metal hydride according to claim 2, wherein: the organic solvent is any one of N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, dioxane, toluene, N-methylpyrrolidone and ethanol.

7. The method for preparing an amino compound by catalytic reduction of a nitro compound with an alkaline earth metal hydride according to claim 2, wherein: the molar ratio of the alkaline earth metal hydride to the nitro compound is 1-10.

8. The method for preparing an amino compound by catalytic reduction of a nitro compound with an alkaline earth metal hydride according to claim 2, wherein: the molar ratio of the diboronic ester to the nitro compound is 0.5-10.

9. The method for preparing an amino compound by catalytic reduction of a nitro compound with an alkaline earth metal hydride according to claim 2, wherein: the reaction temperature in the step (1) is 80-140 ℃, and the reaction time is 3-12 h.

10. The method for preparing an amino compound by catalytic reduction of a nitro compound with an alkaline earth metal hydride according to claim 2, wherein: the gas atmosphere required by the reaction in the step (1) is air or nitrogen.

Technical Field

The invention belongs to the technical field of amino compound synthesis, and particularly relates to a method for preparing an amino compound by catalytic reduction of a nitro compound by using an alkaline earth metal hydride.

Background

The amine compound is an important organic synthesis intermediate in chemical industry, and can be used for synthesizing antioxidants, dyes, active components, polymer modifiers, adhesives, light-resistant agents, photosensitive materials, food additives, medicines and the like. There are many methods for synthesizing amino compounds, such as catalytic amination of aryl halides, reduction of functional groups such as imines and nitriles, reduction of nitro compounds, and the like. Among them, the reduction of nitro compounds is the most common method for the synthesis of amino compounds on a laboratory and industrial scale. The industrial reduction of nitro compounds mainly depends on two methods of iron powder reduction and palladium-carbon hydrogenation reduction. The iron powder reduction method has mature process, less equipment investment, low catalyst price and simple and convenient operation, but a large amount of three wastes (waste residues, waste liquids and waste gases) can be generated in the process, so that the environmental pollution is great and the corrosion to equipment is serious; the catalytic hydrogenation reduction method has the advantages of complete reaction, less by-products and less environmental pollution, but usually needs high temperature and high pressure, and has higher requirements on production devices and process control. Therefore, in order to further improve the yield of the nitro reduction reaction, simplify the reaction operation process and the post-treatment process, improve the selectivity of the reaction and reduce the environmental pollution, domestic and foreign scholars have conducted a series of researches on the catalytic reduction reaction of the nitro compounds.

For example, Yukihiro Motoyama subject group of Kyushu university in Japan, 2008 develops a Pt-based nano catalyst, and the Pt-based nano catalyst is successfully applied to hydrogenation reduction reaction of nitro compounds, and the catalyst shows more excellent catalytic performance than the traditional palladium-carbon reducing agent. (Mikihiro Takasaki and Yukihiro Motoyama. org. Lett.,2008,10(8), 1601-one 1604)

Brindaban C.Ranu subject group in 2012 reports that iron metal nanoparticles are used as gold

Belongs to a method for generating an amino compound by reducing a nitro compound at room temperature by using water as a solvent. The reaction condition is mild, and the nitro compound can be selectively reduced, and functional groups such as carbonyl, C-C double bonds, C-C triple bonds and the like are reserved. (RajuDey, Nimalya Mukherjee, Sabir Ahammed and Brindaban C Ranu. chem. Commun.,2012,48, 7982-

In 2016, the issue group of Stephen p.thomas at the university of esteberg, uk reported a reduction method using iron amino bisphenolate as catalyst, triethoxysilane as hydrogen source, and acetonitrile as reaction solvent, which achieved separation yields of 80% or more for various aryl compounds. (Kailong Zhu, Michael P.Shaver and Stephen P.ThomasChem.Sci.,2016,7,3031-

In 2018, Suhaijia topic group of Beijing chemical university is polymer semiconductor g-C₃N₄The hydrazine hydrate is used as a catalyst and a reducing agent, and the reduction of the nitro compound into the amino compound is realized under the condition of illumination. The method has mild reaction conditions, and the catalyst has high catalytic activity and can be recycled. (Gang Xiao, Peifeng Li, Yilin Zao, Shengnan Xu, and Haijia Su. chem. Asian J.,2018,13,1950, 1955)

As can be seen from the above reports, the research and improvement of the reduction reaction of nitro compounds still requires the participation of transition metals such as iron, platinum, etc., and high-pressure hydrogen, silane, etc. are still used as hydrogen source. The problems that the cost is increased and the environmental pollution is serious by using a transition metal catalyst and the problems that high temperature and high pressure are often needed and the requirements on production devices and process control are high when hydrogen and other expensive hydrogen source reagents are used for reduction are still not solved. Therefore, there is an urgent need to develop a method for reducing nitro compounds, which is environmentally friendly, low in cost and simple in operation.

Disclosure of Invention

The invention aims to provide a method for preparing an amino compound by catalytic reduction of a nitro compound by using an alkaline earth metal hydride, which is used for solving the technical problems of serious environmental pollution, high production cost and higher requirements on production devices and process control in the conventional synthetic method for preparing the amino compound by reduction of the nitro compound.

The general reaction formula of the invention is as follows, and the preparation method of the invention comprises the following steps:

step (1): respectively adding nitro compounds serving as reaction substrates, alkaline earth metal hydrides serving as hydrogen sources and diborate serving as catalysts into an organic solvent, and stirring and heating the mixture to perform reaction; the reaction temperature is 50-150 ℃, and the reaction time is 3-20 h;

step (2): and after the reaction is finished, carrying out post-treatment, separation and purification to obtain the amino compound.

Preferably, R is aryl or aromatic heterocyclic radical.

Preferably, the nitro compound is 3-nitrotoluene, 4-nitrochlorobenzene or 2-nitropyridine.

Preferably, the alkaline earth metal hydride is any one of sodium hydride, potassium hydride, and calcium hydride.

Preferably, the diborate is any one of pinacol diborate, bis (2, 4-dimethyl-2, 4-pentanediol) borate, neopentyl glycol diborate and bis catechol borate.

Preferably, the organic solvent is any one of N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, dioxane, toluene, N-methylpyrrolidone and ethanol.

Preferably, the molar ratio of the alkaline earth metal hydride to the nitro compound is from 1 to 10.

Preferably, the mole ratio of the diboronate to nitro compound is from 0.5 to 10.

Preferably, the reaction temperature in the step (1) is 80-140 ℃, and the reaction time is 3-12 h.

Preferably, the gas atmosphere required for the reaction in step (1) is air or nitrogen.

The invention has the beneficial effects that: the method has the advantages of simple synthesis steps, mild reaction conditions, utilization of cheap and easily-obtained alkaline earth metal hydride as a hydrogen source, avoidance of use of transition metal and high-pressure hydrogen in the reaction process, reduction of reaction cost, accordance with the current theme of green chemical development, no excessive requirements on reaction equipment and ideal industrial application prospect.

Drawings

FIG. 1 is a drawing showing the preparation of 3-methylaniline of example 1¹H NMR spectrum;

FIG. 2 is a drawing showing the preparation of 3-methylaniline of example 1¹³C NMR spectrum;

FIG. 3 is a schematic representation of 4-chloroaniline prepared in example 2¹H NMR spectrum;

FIG. 4 is a schematic representation of 4-chloroaniline prepared in example 2¹³C NMR spectrum;

FIG. 5 is a schematic representation of the 2-aminopyridine prepared in example 3¹H NMR spectrum;

FIG. 6 is a drawing of the preparation of 2-aminopyridine example 3¹³C NMR spectrum.

Detailed Description

The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.

The invention provides a method for preparing an amino compound by catalytic reduction of a nitro compound by using an alkaline earth metal hydride, which has the following general formula:

step (1): respectively adding nitro compounds serving as reaction substrates, alkaline earth metal hydrides serving as hydrogen sources and diborate serving as catalysts into an organic solvent, and stirring and heating the mixture to perform reaction; the reaction temperature is 50-150 ℃, and the reaction time is 3-20 h;

step (2): and after the reaction is finished, carrying out post-treatment, separation and purification to obtain the amino compound.

And R is aryl or aromatic heterocyclic radical.

The nitro compound is 3-nitrotoluene, 4-nitrochlorobenzene or 2-nitropyridine.

The alkaline earth metal hydride is any one of sodium hydride, potassium hydride and calcium hydride.

The diborate is any one of diboronic acid pinacol ester, bis (2, 4-dimethyl-2, 4-pentanediol) borate, diboronic acid neopentyl glycol ester and bis pyrocatechol borate.

The organic solvent is any one of N, N-dimethylformamide, N-dimethylacetamide, dimethyl sulfoxide, dioxane, toluene, N-methylpyrrolidone and ethanol.

The molar ratio of the alkaline earth metal hydride to the nitro compound is 1-10.

The molar ratio of the diboronic ester to the nitro compound is 0.5-10.

The reaction temperature in the step (1) is 80-140 ℃, and the reaction time is 3-12 h.

The gas atmosphere required by the reaction in the step (1) is air or nitrogen.