Main applications of o-bromoaniline_Kain Industrial Additives

Background and overview^[1]

O-bromoaniline is a white needle-like crystal. Molecular weight 172.03. Melting point 32℃. Boiling point 229℃. Relative density 1.578 (20/4℃). The refractive index is 1.6113. Soluble in alcohol and ether, insoluble in water. Used as intermediates in organic synthesis. Using o-nitroaniline as raw material, it is obtained through diazotization, bromination and reduction. O-bromoaniline can be used as a pharmaceutical synthesis intermediate. At present, the industrial production method of o-bromoaniline is still relatively traditional. This traditional production method has problems such as low yield, low purity and serious pollution. The production process is relatively complex and difficult to meet human needs.

Apply^[2-5]

O-bromoaniline can be used as raw materials for dyes, such as azo dyes, quinoline dyes, etc., as well as pharmaceutical and organic synthesis intermediates. Examples of its application are as follows:

1) Preparation of 8-bromo-4-carboxyquinoline, the method includes the following steps: (1) o-bromoaniline and butenone are reacted under the catalysis of ferric chloride to obtain 8-bromo-4-methyl Quinoline; (2) oxidize 8-bromo-4-methylquinoline with selenium dioxide in an organic solvent to obtain 8-bromoquinoline-4-carbaldehyde; (3) oxidize 8-bromoquinoline-4-carbaldehyde with hydrogen peroxide in an acidic medium -Bromoquinoline-4-carbaldehyde gives 8-bromo-4-carboxyquinoline. This method uses more economical o-bromoaniline as raw material, has simple synthesis steps, high synthesis yield and high selectivity.

2) Preparation of 1-bromocarbazole, which belongs to the field of organic chemical synthesis. The preparation method of 1-bromocarbazole provided by the invention is specifically: using o-bromoaniline and o-bromoiodobenzene as raw materials, carrying out Ullmann coupling reaction to obtain the intermediate di-(2-bromophenyl)amine ; The intermediate di-(2-bromophenyl)amine undergoes a ring-closing reaction under the action of a palladium catalyst to obtain 1-bromocarbazole. The method of the invention has simple reaction operation, can recycle the solvent and apply it, has low raw material cost and high yield, and is conducive to the realization of industrial production. In addition, the 1-bromocarbazole prepared by the method of the present invention has high purity and can be used in the fields of OLED optoelectronics, medicine, dyes, pesticides and other fields. It is an important carbazole intermediate and has broad application prospects.

3) Preparation of 5-methyl-7-amino-5H,7H-dibenzo[b,d]azepan-6-one. This method uses o-bromoaniline and phenylboronic acid as raw materials. The wood coupling reaction yields 2-aminobiphenyl. After protecting the amino group with ethyl chloroformate, potassium tert-butoxide is used as an acid binding agent to perform an N-methylation reaction with methyl iodide, followed by amino deprotection and chloroacetylation. Finally, the target product is obtained through intramolecular Friedel-Crafts cyclization and alkylation reaction. The invention has the advantages of simple process, high overall yield and low production cost, and is suitable for industrial large-scale production.

4) Prepare o-dibromobenzene, add hydrobromic acid, cuprous oxide, and o-bromoaniline to a reactor equipped with a stirrer, condenser, and thermometer in sequence, heat to above 80°C, and maintain 80-100°C During the process, an aqueous solution of sodium nitrite is added dropwise from the liquid surface. After the dripping is completed, the product is distilled by steam and the oil layer is separated. It is washed once with water and alkali. After washing once with water, the product is distilled under reduced pressure. The preparation method of o-dibromobenzene provided by the invention uses a one-step method to carry out diazotization and decomposition reactions, which greatly reduces energy consumption and refrigeration equipment investment, and the product yield is stable, and will not be affected by the refrigeration problems of the two-step method. It causes yield fluctuations, and the continuous production capacity is greatly improved. The quality of the product is consistent with the two-step method, the yield is slightly higher, the preparation process is simple and easy, the product quality is good, and the process requirements are low. It is a method suitable for industrial production.

Preparation^[6]

A production process for the synthesis of o-bromoaniline, which is characterized by: including the following process steps,

(1) Diazotization

a. Select a diazotization reactor, then add 90-110kg of o-nitroaniline, 450-550L of water and 150-170L of concentrated hydrochloric acid, and turn on the stirring device to start stirring.

b. Pour steam into the reaction kettle in step a to heat it until the bath is full, then turn on the frozen brine to cool the material liquid to ≤5°C.

c. Add 130-135kg 23.7% sodium nitrite aqueous solution to the cooled material liquid in step b, control the temperature in the kettle to ≤10°C, and then continue to stir the diazo reaction liquid after 10-20 minutes of reaction. .

(2) Bromination

a. Select a monobromination reaction kettle, then add 165-170kg of copper sulfate and 110-130kg of water, turn on the stirring device to start stirring and add steam to heat until completely dissolved.

b. Add 115-120kg of potassium bromide and 40-45kg of powdery anhydrous sodium sulfite to the reaction solution after the complete reaction in step a, and continue stirring until white copper bromide precipitates in the kettle.

c. Pump the material liquid from step b into a centrifuge and centrifuge to obtain crystals.

d. Then select a hydrobromic acid reactor with 70-90L, turn on the stirring device and start stirring, add the diazo reaction solution prepared in step (1), and continue stirring for 2.5-3.5 hours.

e. Pour in the reactants in step d for heating and start steam distillation. Then collect the oil and water phases together into a crystallization kettle for crystallization. Then use frozen brine to cool the temperature to ≤20°C to precipitate crystals.

f. Put the crystal in step e into a centrifuge and centrifuge to obtain o-nitrobromobenzene.

(3) Restore

a. Add the o-nitrobromobenzene prepared in step (2) into the reduction kettle, then add 100L of water, start stirring, and then add 100kg of iron powder.

b. Heat the temperature in the kettle in step a to the reflux temperature, add 100kg of hydrobromic acid dropwise, and reflux again for 3.0 hours to start cooling with cold water.

c. Add sodium hydroxide to the cooled reaction liquid in step b to neutralize until the pH value is 7-8.

d. After passing steam into the neutralized material liquid in step c for distillation, the distillate is cooled and centrifuged to obtain the product, which is the finished product of o-bromoaniline.

Main reference materials

[1] Concise Dictionary of Fine Chemicals

[2] CN201310385816.6 A synthesis method of 8-bromo-4-carboxyquinoline

[3] CN201710374924.1 Preparation method of 1-bromocarbazole

[4] Preparation method of CN201310354172.45-methyl-7-amino-5H, 7H-dibenzo[b,d]azepan-6-one

[5] CN201410058576.3 A one-step method for synthesizing o-dibromobenzene through diazotization at high temperature [6] CN201410256608.0 A production process for the synthesis of o-bromoaniline