Preparation method of 1,2-dialkylphenylhydrazine and preparation method of dialkylbenzidine

Abstract

The present invention relates to a method for preparing 1,2 - di - alkylphenylhydrazine and a method for preparing di - alkylbenzidine diamine. In the method for preparing 1,2 - di - alkylphenylhydrazine, the reaction formula is: In the above formula, R is an alkyl group with 1 - 5 carbon atoms, and LG is H or a leaving group. The method includes the following steps: mixing compound 1, a Pt / C catalyst, and a basic reaction medium in a closed container; the reaction proceeds through three stages: in the first stage, the hydrogen partial pressure in the closed container is 0.3 - 0.5 MPa, the temperature is 60°C - 65°C, and it is maintained for 3 - 8 h; the second stage includes any one of the following conditions: i) the hydrogen partial pressure in the closed container is 0.3 - 0.5 MPa, the temperature is 110°C - 120°C, and it is maintained for 2 - 4 h; ii) the hydrogen partial pressure in the closed container is 1.6 - 1.8 MPa, the temperature is 60°C - 65°C, and it is maintained for 2 - 4 h; in the third stage, the hydrogen partial pressure in the closed container is 1.6 - 1.8 MPa, the temperature is 110°C - 120°C, and it is maintained for 1 - 3 h. The present invention can prepare 1,2 - di - alkylphenylhydrazine in high yield without the need to additionally add a cocatalyst and a surfactant.

Description

Technical Field

[0001] The invention relates to the field of organic synthesis, and in particular to a method for preparing 1,2-m-dialkylphenylhydrazine and a method for preparing dialkylbenzenediamine. Background Art

[0002] 3,3'-Dimethyldiphenylhydrazine is an important fine chemical raw material, which is widely used in synthetic dyes, paints, inks and other industries. 3,3'-Dimethyldiphenylhydrazine can also be further reacted to produce dimethylbenzene diamine compounds, which are important intermediates for a variety of polymer materials.

[0003] In the prior art, the reaction of preparing benzidine from nitrobenzene substrates such as nitrobenzene and m-nitrotrifluorotoluene, which have no substituent or have electron-withdrawing groups on the benzene ring, under a catalytic hydrogenation system can usually achieve a yield of more than 90%. However, when the nitrobenzene substrates have electron-donating groups on the benzene ring, such as o-nitrotoluene and o-methoxytoluene, the article Selective Catalytic Hydrogenation of Nitrobenzene to Hydrazobenzene (Ind. Eng. Chem. Res. 1988, 27, 21-24) points out that this may be because as the electron cloud density on the aromatic ring increases, the nitrogen atom and the catalyst are more firmly bound, making the reaction difficult to proceed.

[0004] There are also great differences in the reactivity of nitrobenzene substrates with electron-donating groups on the benzene ring. For example, CN110590596B clearly points out in paragraph

[0007] of its specification that "the effect of applying the catalytic hydrogenation system to m-nitrotoluene is not ideal, far inferior to o-nitrotoluene and m-nitrotrifluorotoluene". According to the records of the patent, the yield of m-nitrotoluene under the conditions of catalytic hydrogenation containing a co-catalyst is less than 80%. Summary of the invention

[0005] The present invention is made to solve the above problems, and aims to provide a method for preparing 1,2-dialkylphenylhydrazine and dialkylbenzenediamine without the need for a co-catalyst and a phase transfer catalyst.

[0006] The first aspect of the present invention provides a method for preparing 1,2-dialkylphenylhydrazine, and the reaction formula is as follows:

[0007]

[0008] In the above formula, R is a C1-C5 alkyl group, LG is H or a leaving group,

[0009] The preparation method comprises the following steps:

[0010] Compound 1, Pt / C catalyst and an alkaline reaction medium are mixed in a closed container; the reaction proceeds in three stages:

[0011] In the first stage, the hydrogen partial pressure in the closed container is 0.3 - 0.5 MPa, the temperature is 60°C - 65°C, and it is maintained for 3 - 8 h;

[0012] The second stage includes any one of the following conditions:

[0013] i) The hydrogen partial pressure in the closed container is 0.3 - 0.5 MPa, the temperature is 110°C - 120°C, and it is maintained for 2 - 4 h;

[0014] ii) The hydrogen partial pressure in the closed container is 1.6 - 1.8 MPa, the temperature is 60°C - 65°C, and it is maintained for 2 - 4 h;

[0015] In the third stage, the hydrogen partial pressure in the closed container is 1.6 - 1.8 MPa, the temperature is 110°C - 120°C, and it is maintained for 1 - 3 h.

[0016] The second aspect of the present invention provides a method for preparing dialkylbiphenyldiamine, comprising the following steps:

[0017] Step 1, prepare 1,2 - m - dialkylphenylhydrazine according to the preparation method described in the first aspect of the present invention to obtain 1,2 - m - dialkylphenylhydrazine;

[0018] Step 2, mix the 1,2 - m - dialkylphenylhydrazine with an alcoholic solution of an acid, react, and centrifuge to obtain a salt of dialkylbiphenyldiamine;

[0019] Step 3, disperse the salt of dialkylbiphenyldiamine in a solvent, add a basic reagent, and perform recrystallization to obtain dialkylbiphenyldiamine.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] According to the preparation method of 1,2 - m - dialkylphenylhydrazine involved in the present invention, since Pt / C is selected as the catalyst and the reaction proceeds in three stages, with specific pressurization and reaction temperatures selected for each stage. Therefore, the present invention can obtain 1,2 - m - dialkylphenylhydrazine in high yield without the need to additionally add a cocatalyst and a surfactant. Description of the Drawings

[0022] Figure 1 is the HPLC spectrum of 1,2 - m - dialkylphenylhydrazine prepared in Example 1 of the present invention;

[0023] Figure 21H NMR spectrum of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine prepared in Example 4 of the present invention;

[0024] Figure 3 HPLC spectrum of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine prepared in Example 4 of the present invention;

[0025] Figure 4 Sample diagrams of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine prepared in Examples 4 and 5 of the present invention ( Figure 4 a, 4b are samples prepared in Example 4, Figure 4 c, 4d are samples prepared in Example 5). Detailed Description of the Invention

[0026] Hereinafter, the embodiments of the preparation method of 1,2-dialkylphenylhydrazine and the preparation method of dialkylbiphenyldiamine specifically disclosed will be described in detail.

[0027] Term Definition

[0028] Unless otherwise specified, the following words, phrases and symbols used in this specification generally have the meanings described below.

[0029] Generally, the nomenclature used herein (e.g., IUPAC nomenclature) and the laboratory procedures described below (including those for cell culture, organic chemistry, analytical chemistry, and pharmacology, etc.) are those well-known and commonly used in the art. Unless otherwise defined, all scientific and technical terms used herein in connection with the present disclosure described herein have the same meaning as commonly understood by those skilled in the art. Additionally, in the claims and / or the specification, when the term "a" or "an" is used in conjunction with the term "comprising" or a noun, its meaning may be "one", but is also consistent with the meanings of "one or more", "at least one", and "one or more than one". Similarly, the term "another" or "other" may mean at least a second or more.

[0030] It should be understood that whenever an aspect is described herein using the terms "comprising" or "including", other similar aspects described by "consisting of" and / or "consisting essentially of" are also provided.

[0031] In this text, the term "alkyl", used alone or in combination, can be straight-chain or branched-chain, and the number of carbon atoms can be, for example, C1-C5, C1-C4, C1-C3, or C1-C2, etc. By way of example, alkyl includes, but is not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, etc.

[0032] Preparation Method of 1,2-Dialkylphenylhydrazine

[0033] The present invention provides a method for preparing 1,2-m-dialkylphenylhydrazine, and the reaction formula is as follows:

[0034]

[0035] In the above formula, R is an alkyl group of C1-C5, and LG is H or a leaving group.

[0036] The preparation method includes the following steps:

[0037] Mix compound 1, a Pt / C catalyst, and a basic reaction medium in a closed container; the reaction proceeds in three stages:

[0038] In the first stage, the hydrogen partial pressure in the closed container is 0.3-0.5 MPa, the temperature is 60°C-65°C, and it is maintained for 3-8 h;

[0039] The second stage includes any one of the following conditions:

[0040] i) The hydrogen partial pressure in the closed container is 0.3-0.5 MPa, the temperature is 110°C-120°C, and it is maintained for 2-4 h;

[0041] ii) The hydrogen partial pressure in the closed container is 1.6-1.8 MPa, the temperature is 60°C-65°C, and it is maintained for 2-4 h;

[0042] In the third stage, the hydrogen partial pressure in the closed container is 1.6-1.8 MPa, the temperature is 110°C-120°C, and it is maintained for 1-3 h.

[0043] In the method for preparing 1,2-m-dialkylphenylhydrazine provided by the present invention, the mass ratio of the Pt / C catalyst to compound 1 is (0.2%-3.0%):1. In some embodiments, the mass ratio of the Pt / C catalyst to compound 1 can also be (0.2%-0.5%):1, (0.5%-0.8%):1, (0.2%-0.8%):1, (0.8%-1.5%):1, (1.5%-2.5%):1, or (2.5%-3.0%):1, etc.

[0044] Further optionally, in the Pt / C catalyst, the content of Pt is 5%-20%. In some embodiments, the content of Pt is 5%-10%, 10%-15% or 15%-20%, etc.

[0045] In the method for preparing 1,2-m-dialkylphenylhydrazine provided by the present invention, the basic reaction medium is a mixture composed of a hydroxide and an alcohol compound.

[0046] Further optionally, the alcohol compound is selected from one or both of methanol and ethanol.

[0047] Further optionally, the hydroxide is selected from one or both of sodium hydroxide and potassium hydroxide.

[0048] Further optionally, the mass ratio of the hydroxide to the alcohol compound is 1:(2-5). In some embodiments, the mass ratio of the hydroxide to the alcohol compound can also be 1:(2-4) or 1:(4-5), etc.

[0049] In the method for preparing 1,2-m-dialkylphenylhydrazine provided by the present invention, the mass ratio of the compound 1 to the basic reaction medium is (1-2):1.

[0050] In the method for preparing 1,2-m-dialkylphenylhydrazine provided by the present invention, R is selected from alkyl groups of C1-C4 or alkyl groups of C1-C3, etc. Optionally, R is selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl or sec-butyl. Further optionally, R is selected from methyl or ethyl.

[0051] In the method for preparing 1,2-m-dialkylphenylhydrazine provided by the present invention, LG is H.

[0052] In the method for preparing 1,2-m-dialkylphenylhydrazine provided by the present invention, LG is a leaving group, where the leaving group can be, for example, p-toluenesulfonyl group, methanesulfonyl group, trifluoromethanesulfonyl group, etc.

[0053] In the method for preparing 1,2-m-dialkylphenylhydrazine provided by the present invention, in the first stage, the hydrogen partial pressure in the closed container can be, for example, 0.3-0.5 MPa, 0.3-0.4 MPa or 0.4-0.5 MPa, etc. The temperature can be, for example, 60°C-65°C, 60°C-62°C or 62°C-65°C, etc. The holding time is 3-6 h or 6-8 h, etc.

[0054] In the preparation method of 1,2 - m - dialkylphenylhydrazine provided by the present invention, in i) of the second stage, the hydrogen partial pressure in the closed container can be, for example, 0.3 - 0.5 MPa, 0.3 - 0.4 MPa, or 0.4 - 0.5 MPa, etc. The temperature can be, for example, 110°C - 120°C, 110°C - 115°C, or 115°C - 120°C, etc. The holding time can be, for example, 2 - 4 h, 2 - 3 h, or 3 - 4 h, etc.

[0055] In ii) of the second stage, the hydrogen partial pressure in the closed container can be, for example, 1.6 - 1.8 MPa, 1.6 - 1.7 MPa, or 1.7 - 1.8 MPa, etc. The temperature can be, for example, 60°C - 65°C, 60°C - 62°C, or 62°C - 65°C, etc. The holding time can be, for example, 2 - 4 h, 2 - 3 h, or 3 - 4 h, etc.

[0056] In the preparation method of 1,2 - m - dialkylphenylhydrazine provided by the present invention, in the third stage, the hydrogen partial pressure in the closed container can be, for example, 1.6 - 1.8 MPa, 1.6 - 1.7 MPa, or 1.7 - 1.8 MPa, etc. The temperature can be, for example, 110°C - 120°C, 110°C - 115°C, or 115°C - 120°C, etc. The holding time is 1 - 3 h, 1 - 2 h, or 2 - 3 h, etc.

[0057] Preparation Method of Dialkylbenzidine

[0058] The present invention also provides a preparation method of dialkylbenzidine diamine, comprising the following steps:

[0059] Step 1, prepare 1,2 - m - dialkylphenylhydrazine according to the preparation method described in the first aspect of the present invention to obtain 1,2 - m - dialkylphenylhydrazine;

[0060] Step 2, mix the 1,2 - m - dialkylphenylhydrazine with an alcoholic solution of an acid, react, and centrifuge to obtain a salt of dialkylbenzidine diamine;

[0061] Step 3, disperse the salt of dialkylbenzidine diamine in a solvent, add a basic reagent, and perform recrystallization to obtain dialkylbenzidine diamine.

[0062] In the preparation method of dialkylbenzidine diamine provided by the present invention, in step 2, the alcoholic solution of the acid is any one of a methanol solution of sulfuric acid, an ethanol solution of sulfuric acid, a methanol solution of hydrochloric acid, or an ethanol solution of hydrochloric acid.

[0063] In step 2 of the present invention, the mass ratio of compound 1 to the alcoholic solution of the acid is 1:(1.5 - 3). In specific examples, the mass ratio of m - nitrotoluene to the alcoholic solution of the acid is 1:(1.5 - 3). Compound 1 is Among them, the selections of R and LG are the same as those defined in the preparation method of 1,2 - m - dialkylphenylhydrazine described in the first aspect of the present invention.

[0064] In step 3 of the present invention, the solvent is a mixed solvent of toluene and water.

[0065] In step 3 of the present invention, the basic reagent is an aqueous sodium hydroxide solution.

[0066] In the preparation method of dialkylbenzidine provided by the present invention, the present invention also includes using an alcohol compound to slurry the salt of dialkylbenzidine to obtain a refined salt of dialkylbenzidine; and then further reacting the refined salt of dialkylbenzidine to obtain dialkylbenzidine.

[0067] Specifically, it includes the following steps:

[0068] Step 1, prepare 1,2 - m - dialkylphenylhydrazine according to the preparation method described in the first aspect of the present invention to obtain 1,2 - m - dialkylphenylhydrazine;

[0069] Step 2, mix the 1,2 - m - dialkylphenylhydrazine with an alcoholic solution of an acid, react, and centrifuge to obtain the salt of dialkylbenzidine;

[0070] Step 3, use an alcohol compound to slurry the salt of dialkylbenzidine to obtain a refined salt of dialkylbenzidine;

[0071] Step 4, disperse the refined salt of dialkylbenzidine in a solvent, add a basic reagent, and perform recrystallization to obtain dialkylbenzidine.

[0072] Among them, the mass ratio of the 1,2 - m - dialkylphenylhydrazine to the alcoholic solution of the acid in step 2 and the selection of the alcoholic solution of the acid are the same as before.

[0073] In step 3, the alcohol compound is selected from methanol and / or ethanol. By thermally slurrying the salt of dialkylbenzidine with an alcohol compound, the purity of the final product can be further improved and the appearance of the final product can be improved. Among them, the temperature of the thermal slurry can be, for example, 55 - 60 °C.

[0074] In step 4, the solvent is a mixed solvent of toluene and water. The basic reagent is an aqueous sodium hydroxide solution.

[0075] The technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments of the present invention. It is necessary to point out here that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Some non - essential improvements and adjustments made by those skilled in the art based on the above content of the present invention still fall within the protection scope of the present invention.

[0076] In the following examples, the Pt content in the Pt / C catalyst is 10%;

[0077] In the following examples, the Pd content in the Pd / C catalyst is 10%;

[0078] In the following examples, the concentrated sulfuric acid is commercially available 98% concentrated sulfuric acid.

[0079] Unless otherwise specified, all raw materials in the following examples are commercially available products.

[0080] In the following examples of the present invention, the calculation method of the yield: Yield = (mass of the actual product / mass of the theoretical product) * 100%.

[0081] <Example 1>

[0082] Preparation method of 1,2-dialkylphenylhydrazine

[0083] This example provides a preparation method of compound 2a, and the reaction formula is as follows:

[0084]

[0085] It includes the following steps:

[0086] Add 40 g of compound 1a, 6 g of sodium hydroxide, 0.2 g of Pt / C catalyst, and 24 g of methanol into the hydrogenation kettle. After replacing the hydrogen in the hydrogenation kettle, the reaction proceeds in three stages:

[0087] In the first stage, introduce hydrogen to make the hydrogen partial pressure in the hydrogenation kettle 0.4 MPa, control the temperature in the hydrogenation kettle at 60 - 65 °C, and react for 6 h;

[0088] In the second stage, maintain the hydrogen partial pressure in the hydrogenation kettle at 0.4 MPa, control the temperature at 115 - 120 °C, and react for 3 h;

[0089] In the third stage, adjust the hydrogen partial pressure in the reaction kettle to 1.7 MPa, maintain the temperature at 115 - 120 °C, and continue to react for 2 h;

[0090] After the reaction is completed, filter, wash the reaction solution with water, and concentrate under reduced pressure to obtain 31.2 g of 1,2-dialkylphenylhydrazine (i.e., compound 2a), with a yield of 100.8%, a purity of 90.7%. The product can be used to prepare 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine without further purification. Among them, the yield is calculated based on compound 1a. In this example, the amount of substance of the theoretical product is 0.146 mol. The yield of compound 2a = [31.2 / (0.146 * 212)] * 100% = 100.8%. The yield calculation method for other examples refers to Example 1.

[0091] Figure 1 The HPLC spectrum of 1,2-m-dialkylphenylhydrazine prepared in this example.

[0092] <Example 2>

[0093] Screening of catalysts

[0094] In this example, the catalysts were screened on the basis of Example 1. Except for the conditions listed in Table 1, the other conditions were the same as those in Example 1.

[0095] The screening results are shown in Table 1.

[0096] Table 1 Screening of catalysts

[0097] Serial Number Catalyst Dosage Yield / Purity 1 Pd / C 0.2g 80.6％ / 91.3％ 2 Pt / C 0.15g 97.2％ / 93.1％ 3 Pt / C 0.28g 96.4％ / 88.7％ 4 Pt / C 0.5g 95.3％ / 85.8％ 5 Pt / C 1.0g 94.6％ / 85.8％ 6 Pd / C 0.5g 74.4％ / 89.1％

[0098] As can be seen from Table 1, in this example, the effect of using Pt / C catalyst to catalyze the reaction is better than that of Pd / C catalyst. When Pt / C is used as the catalyst and the amount of catalyst is greater than 0.28 g, the yield and purity of the product will instead decrease with the increase of the amount of catalyst. This may be because a higher amount of catalyst will cause part of the starting material m-nitrotoluene to be directly reduced to m-methylaniline at the early stage of the reaction, rather than staying in the intermediate stage, resulting in a decrease in the yield of the final product.

[0099] <Example 3>

[0100] Screening of catalytic conditions

[0101] In this example, the catalytic conditions were screened on the basis of Example 1. Except for the conditions listed in Table 2, the other conditions were the same as those in Example 1.

[0102] The screening results are shown in Table 2.

[0103] Table 2 Screening of catalytic conditions

[0104]

[0105]

[0106] As can be seen from Table 2, when the segmented heating and pressurization process is not adopted, the yield is low, and the highest does not exceed 65%, making it difficult to be applied industrially. When the two-stage heating and pressurization process is adopted, both the yield and purity can be improved to a certain extent, and most of them can reach more than 85%. When the three-stage heating and pressurization process is adopted, the yield can be further increased to more than 90%.

[0107] <Example 4>

[0108] Production Method of 2,2'-Dimethyl-[1,1'-biphenyl]-4,4'-diamine

[0109] This example provides a continuous production method of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine, which includes the following steps:

[0110] Step 1: Add 400 g of Compound 1a to a hydrogenation kettle 60 g of sodium hydroxide, 2 g of Pt / C catalyst, and 240 g of methanol. After replacing the hydrogen in the hydrogenation kettle, the reaction proceeds in three stages:

[0111] The first stage: Introduce hydrogen to make the hydrogen partial pressure in the hydrogenation kettle 0.4 MPa, control the temperature in the hydrogenation kettle at 60 - 65 °C, and react for 6 h;

[0112] The second stage: Maintain the hydrogen partial pressure in the hydrogenation kettle at 0.4 MPa, control the temperature at 115 - 120 °C, and react for 3 h;

[0113] The third stage: Adjust the hydrogen partial pressure in the reaction kettle to 1.7 MPa, maintain the temperature at 115 - 120 °C, and continue to react for 2 h;

[0114] After the reaction is completed, filter, wash the filtrate with water, and take the organic phase;

[0115] Step 2: Add 640 g of methanol to the reaction kettle, control the temperature at 10 - 20 °C, dropwise add 160 g of concentrated sulfuric acid, then add the organic phase obtained in Step 1, control the temperature at 55 - 60 °C, stir and react for 0.5 h, cool down to 15 - 20 °C, and centrifuge to obtain the sulfate of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine;

[0116] Step 3: Add the sulfate of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine obtained in Step 2 to 780 g of methanol, heat up to 55 - 60 °C, stir for 2 h, cool down to 15 - 20 °C, stand for 2 h, and centrifuge to obtain the refined sulfate of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine;

[0117] Step 4: Add 780 g of toluene, 380 g of water, and the refined sulfate of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine prepared in Step 3 to the reaction kettle. Control the temperature at 50 - 55 °C, dropwise add 30 wt% aqueous sodium hydroxide solution until the pH value of the aqueous phase is 10 - 11, stand, separate the liquid, take the organic phase, wash with water, cool down to 20 - 25 °C, precipitate crystals, and vacuum dry for 5 h to obtain 265.5 g of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine, which is in the form of white powder, with a yield of 85.4% (calculated based on m-nitrotoluene) and a purity of 99.8%.

[0118] Figure 2 1H NMR spectrum of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine prepared in this example;

[0119] Figure 3 HPLC spectrum of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine prepared in this example;

[0120] Figure 4 The samples of a and b are 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine prepared in this example.

[0121] <Example 5>

[0122] Production method of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine

[0123] This example provides a continuous production method of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine. The production method provided in this example is basically the same as that in Example 4, and the only difference is that it does not include Step 3. In this example, the sulfate of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine obtained in Step 2 is directly used in Step 4 to obtain 253.7 g of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine, which is in the form of a light yellow powder, with a yield of 81.6% (based on m-nitrotoluene) and a purity of 93.2%.

[0124] Figure 4 The samples of c and d are 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine prepared in this example.

[0125] <Example 6>

[0126] Production method of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine

[0127] This example provides a continuous production method of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine. The production method provided in this example is basically the same as that in Example 4, and the only difference is that Step 3 is different. In this example, the operation of Step 3 is as follows:

[0128] The sulfate of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine obtained in Step 2 was added to 780 g of tert-butyl methyl ether, the temperature was raised to 55 - 60 °C, stirred for 2 h, cooled to 15 - 20 °C, allowed to stand for 2 h, and centrifuged to obtain the refined sulfate of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine.

[0129] In this example, 239.4 g of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine was obtained, which was in the form of a pale yellow powder, with a yield of 77.0% (based on m-nitrotoluene) and a purity of 95.5%.

[0130] Functions and effects of the examples

[0131] According to the preparation method of 3,3'-dimethyl diphenylhydrazine involved in the above examples, since Pt / C was selected as the catalyst and the reaction passed through three stages, with specific pressure and reaction temperature selected for each stage. Therefore, the above examples can obtain 3,3'-dimethyl diphenylhydrazine in high yield without the need to additionally add a cocatalyst and a surfactant.

[0132] Furthermore, the yield of the present invention after three stages is significantly better than that after only the first two stages or the first stage. And among the two choices in the second stage (such as Example 1 and No. 8 in Table 2), based on the different selections of temperature and pressure in the second stage, the yield of Example 1 is better than that of No. 8 in Table 2.

[0133] According to the production method of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine involved in Examples 4-5, since the preparation method of 3,3'-dimethyl diphenylhydrazine provided in Example 1 was used, it can be used without further purification of 3,3'-dimethyl diphenylhydrazine, which speeds up the production rhythm and saves production costs.

[0134] Furthermore, according to the production method of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine involved in Examples 4-5, since Example 4 also includes the step of hot pulping the crude sulfate of 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-diamine with methanol, the purity of the final product can be further improved and the appearance of the final product can be improved.

[0135] The applicant declares that the present invention uses the above examples to illustrate the preparation method of 1,2-dialkyl phenylhydrazine and the preparation method of dialkyl biphenyl diamine of the present invention, but the present invention is not limited to the above examples, that is, it does not mean that the present invention must rely on the above examples to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent substitution of each raw material of the products of the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

[0136] The above embodiments are preferred examples of the present invention and are not intended to limit the protection scope of the present invention. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0137] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

Claims

1. A method for preparing 1,2 - m - dialkylphenylhydrazine, characterized in that, The reaction formula is as follows: In the above formula, R is an alkyl group with 1-5 carbon atoms, LG is H, The preparation method includes the following steps: Mix compound 1, Pt / C catalyst and a basic reaction medium in a closed container; The reaction proceeds in three stages: In the first stage, the hydrogen partial pressure in the closed container is 0.3-0.5 MPa, the temperature is 60°C-65°C, and it is maintained for 3-8 h; The second stage includes any one of the following conditions: i) The hydrogen partial pressure in the closed container is 0.3-0.5 MPa, the temperature is 110°C-120°C, and it is maintained for 2-4 h; ii) The hydrogen partial pressure in the closed container is 1.6-1.8 MPa, the temperature is 60°C-65°C, and it is maintained for 2-4 h; In the third stage, the hydrogen partial pressure in the closed container is 1.6-1.8 MPa, the temperature is 110°C-120°C, and it is maintained for 1-3 h; The mass ratio of the Pt / C catalyst to compound 1 is (0.2%-3.0%):

1.

2. The preparation method of 1,2-m-dialkylphenylhydrazine according to claim 1, characterized in that: The basic reaction medium is a mixture composed of a hydroxide and an alcohol compound.

3. The preparation method of 1,2-m-dialkylphenylhydrazine according to claim 2, characterized in that: The alcohol compound is selected from one or both of methanol and ethanol.

4. The preparation method of 1,2-m-dialkylphenylhydrazine according to claim 2, characterized in that: The hydroxide is selected from one or both of sodium hydroxide and potassium hydroxide.

5. The preparation method of 1,2-m-dialkylphenylhydrazine according to claim 2, characterized in that: The mass ratio of the hydroxide to the alcohol compound is 1:(2-5).

6. The preparation method of 1,2-m-dialkylphenylhydrazine according to claim 1, characterized in that: The mass ratio of compound 1 to the basic reaction medium is (1-2):

1.

7. A method for preparing dialkylbiphenyldiamine, characterized in that, It includes the following steps: Step 1, prepare 1,2-m-dialkylphenylhydrazine according to the preparation method described in any one of claims 1-6 to obtain 1,2-m-dialkylphenylhydrazine; Step 2, mix the 1,2-m-dialkylphenylhydrazine with an alcoholic solution of an acid, react, and centrifuge to obtain a salt of dialkylbiphenyldiamine; Step 3, disperse the salt of dialkylbiphenyldiamine in a solvent, add a basic reagent, and perform recrystallization to obtain dialkylbiphenyldiamine.

8. The preparation method of the dialkylbiphenyl diamine according to claim 7, characterized in that, It includes the following steps: Step 1, prepare 1,2-m-dialkylphenylhydrazine according to the preparation method described in any one of claims 1-6 to obtain 1,2-m-dialkylphenylhydrazine; Step 2, mix the 1,2-m-dialkylphenylhydrazine with an alcoholic solution of an acid, react, and centrifuge to obtain a salt of dialkylbiphenyldiamine; Step 3, slurry the salt of dialkylbiphenyldiamine with an alcohol compound to obtain a refined salt of dialkylbiphenyldiamine; Step 4, disperse the refined salt of dialkylbiphenyldiamine in a solvent, add a basic reagent, and perform recrystallization to obtain dialkylbiphenyldiamine.

9. The preparation method of dialkylbiphenyldiamine according to claim 7, characterized in that: Among them, The alcoholic solution of the acid in Step 2 is any one of a methanol solution of sulfuric acid, an ethanol solution of sulfuric acid, a methanol solution of hydrochloric acid, or an ethanol solution of hydrochloric acid; And / or, the solvent in Step 3 is a mixed solvent of toluene and water; And / or, the basic reagent in Step 3 is an aqueous sodium hydroxide solution.

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