A method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenyl methane

Abstract

The application provides a method for synthesizing 4,4'-diamino-3,3'-dimethyl biphenyl methane, and belongs to the field of organic catalytic synthesis. The method is characterized in that o-toluidine and formaldehyde are used as raw materials, a catalyst and a reaction solvent are added, and 4,4'-diamino-3,3'-dimethyl biphenyl methane is catalytically synthesized. The synthesis route of the application has the advantages of simple reaction operation, mild conditions, avoidance of the use of hydrochloric acid, recyclability of the catalyst, high conversion rate and selectivity of the experiment, and convenience of post-treatment.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis, and particularly relates to a method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane. Background Art

[0002] 4,4'-Diamino-3,3'-dimethylbiphenylmethane (MDA) is an important chemical raw material with a wide range of industrial applications. The isocyanate produced from 4,4'-diaminodiphenylmethane can be used as a room-temperature curing agent with excellent adhesion. Due to its excellent corrosion resistance, heat resistance, and electrical insulation properties, it can be used as an insulation material for wire and cable and as a fire retardant for polyamide fibers.

[0003] Scanlan et al. reported in J. Am. Chem. Soc. 1935, May 887-892 that the reaction of o-toluidine, hydrochloric acid, and formaldehyde solution yielded 4,4'-diamino-3,3'-dimethylbiphenylmethane in a yield of approximately 63% after alkali neutralization and multiple recrystallizations. This method, however, exhibited high reaction temperatures, numerous byproducts, and complex post-processing, requiring multiple recrystallizations. This method resulted in low yields, high costs, and limited economic benefits, making it a poor choice for industrial applications.

[0004]

[0005] In patent CN1948267A, He Koubao et al. used o-toluidine as a raw material, reacted it with hydrochloric acid to form a salt, then condensed it with a condensing agent in the presence of a catalyst. After neutralization with an alkaline solution, the mixture was recrystallized from the solution to obtain 4,4'-diamino-3,3'-dimethylbiphenylmethane. Although this synthesis method achieved high purity and improved yield, it suffered from a long reaction time, the need for an alkali to neutralize the hydrochloric acid, and the generation of large amounts of saline wastewater, resulting in poor economic benefits.

[0006] Summary of the Invention

[0007] The present invention addresses the deficiencies in existing technologies for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane and provides a method for preparing 4,4'-diamino-3,3'-dimethylbiphenylmethane using a composite catalyst. The method comprises using o-toluidine and formaldehyde as raw materials, adding a catalyst and a reaction solvent, and heating the reaction to synthesize 4,4'-diamino-3,3'-dimethylbiphenylmethane. To address the above issues, the present invention provides the following technical solutions:

[0008] Take o-toluidine and formaldehyde as raw materials, add catalyst and reaction solvent, heat reaction, filter, recover catalyst, and concentrate the filtrate under reduced pressure to obtain crude product, which is then recrystallized to obtain 4,4'-diamino-3,3'-dimethylbiphenylmethane.

[0009] In the method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane, the molar ratio of formaldehyde to o-toluidine is 1:3-4, preferably 1:3.5.

[0010] In the method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane, the catalyst used is a nickel-copper-oxygen catalyst.

[0011] In the method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane, the mass ratio of formaldehyde to catalyst is 1:0.04-0.1, and the preferred mass ratio is 1:0.06.

[0012] In the method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane, the reaction solvent used is N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, and the preferred reaction solvent is N,N-dimethylformamide.

[0013] The method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane has a reaction temperature of 100-120°C, preferably 110°C.

[0014] The method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane has a reaction time of 1 to 3 hours, preferably 2.5 hours.

[0015] The beneficial effects of the present invention are:

[0016] (1) The raw materials of the present invention are cheap and readily available, the cost is low, the reaction conditions are mild and the operation is simple, the reaction steps are short, the catalyst can be recycled, and the economic benefit is high;

[0017] (2) The target product obtained has high conversion rate and selectivity, is easy to post-process, and is conducive to industrial production.

[0018] (3) It avoids the use of strong organic acids, reduces corrosion to equipment, and greatly reduces the discharge and treatment of wastewater, meeting the requirements of modern green industrial production. DETAILED DESCRIPTION

[0019] The formaldehyde used below is all 37% formaldehyde solution.

[0020] Synthesis of nickel-copper-oxide composite catalyst: 1 mmol Ni(NO3)2·6H2O and 2 mmol CuCl2·2H2O were dispersed in deionized water, stirred at room temperature for 30 minutes, and 10 ml of 2 mol / L sodium hydroxide solution was added dropwise to prepare a precursor solution; the obtained precursor solution was transferred to a reactor, heated at 150°C for 6 hours, and after the reaction was completed, it was naturally cooled to room temperature. The obtained components were washed and dried, and then transferred to a muffle furnace and annealed at 300°C for 5 hours to obtain a nickel-copper-oxide composite material.

[0021] Example 1

[0022] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 2.5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 93.5% and the purity is 99.2%.

[0023] Example 2

[0024] To a 100mL three-necked flask, add o-benzylamine (17.1g, 3eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 2.5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 91.9% and the purity is 98.7%.

[0025] Example 3

[0026] To a 100mL three-necked flask, add o-benzylamine (22.9g, 4eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 2.5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 93.2% and the purity is 98.4%.

[0027] Example 4

[0028] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.17g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 2.5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 92.7% and the purity is 98.7%.

[0029] Example 5

[0030] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.43g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 2.5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 93.2% and the purity is 99.1%.

[0031] Example 6

[0032] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 100°C for 2.5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 91.2% and the purity is 98.5%.

[0033] Example 7

[0034] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 120°C for 2.5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 91.9% and the purity is 98.7%.

[0035] Example 8

[0036] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 1 hour, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 91.1% and the purity is 98.9%.

[0037] Example 9

[0038] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 3 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 92.7% and the purity is 99.0%.

[0039] Comparative Example 1

[0040] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.26g of graphene-supported copper catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 2.5h, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 82.6% and the purity is 98.2%.

[0041] Comparative Example 2

[0042] To a 100mL three-necked flask, add o-benzylamine (20g, 2eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 2.5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 79.2% and the purity is 95.6%.

[0043] Comparative Example 3

[0044] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 80°C for 2.5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 85.9% and the purity is 92.5%.

[0045] Comparative Example 4

[0046] To a 100mL three-necked flask, add o-benzylamine (20g, 3.5eq), formaldehyde (4.33g, 1eq), 0.26g of a nickel-copper-oxide composite catalyst, and 30mL of N,N-dimethylformamide. Heat to 110°C for 5 hours, cool to room temperature, filter and recover the catalyst, and concentrate the filtrate under reduced pressure. The crude product is recrystallized from methanol to obtain a white solid. The yield is 82.8% and the purity is 92.6%.

[0047] Although the above describes the specific implementation methods of the present invention, it does not limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without creative work are still within the scope of protection of the present invention.

Claims

1. A method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane, characterized in that: Take o-toluidine and formaldehyde as raw materials, add catalyst and reaction solvent, heat reaction, filter and recover catalyst, concentrate the filtrate under reduced pressure to obtain crude product, and recrystallize to obtain 4,4'-diamino-3,3'-dimethylbiphenylmethane. The reaction formula is as follows: The catalyst is a nickel-copper-oxide catalyst. The synthesis method of the catalyst is as follows: 1 mmol of Ni(NO3)2·6H2O and 2 mmol of CuCl2·2H2O are dispersed in deionized water, stirred at room temperature for 30 minutes, and 10 mL of a 2 mol / L sodium hydroxide solution is added dropwise to prepare a precursor solution; the obtained precursor solution is transferred to a reactor, heated at 150°C for reaction for 6 hours, and after the reaction is completed, the mixture is naturally cooled to room temperature, and the obtained components are washed and dried, and then transferred to a muffle furnace for annealing at 300°C for 5 hours to obtain a nickel-copper-oxide composite material.

2. A method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane according to claim 1, characterized in that: The molar ratio of the formaldehyde to o-toluidine is 1:3-4.

3. A method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane according to claim 1, characterized in that: The mass ratio of the formaldehyde to the catalyst is 1:0.04-0.

1.

4. A method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane according to claim 1, characterized in that: The reaction solvent is N,N-dimethylformamide, N,N-dimethylacetamide, or N-methylpyrrolidone.

5. A method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane according to claim 1, characterized in that: The reaction temperature is 100-120°C.

6. A method for synthesizing 4,4'-diamino-3,3'-dimethylbiphenylmethane according to claim 1, characterized in that: The reaction time is 2 to 3 hours.

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