9,10-Dibromoanthracene is an important intermediate in organic synthesis, which is widely used in the preparation of fluorescent dyes and heterocyclic compounds. This article will introduce various synthetic routes of 9,10-dibromoanthracene, including petrochemical synthesis, direct bromination synthesis of aromatic compounds, copper-catalyzed synthesis and metal-catalyzed synthesis.
1. Petrochemical synthesis method:
In petrochemical industry, 9,10-dibromoanthracene is prepared from raw materials such as cyclohexane, chlorine gas and iron powder. Specific steps are as follows:
1. Chlorination reaction of cyclohexane and chlorine gas with iron powder as catalyst.
2. The generated 1-chlorocyclohexane reacts with tetrabutyllithium in the presence of iodide to generate 1-butylcyclohexane.
3. The product is chlorinated again with chlorine gas in the presence of iron powder to generate the product 2,3-dichloro-1-butylcyclohexane.
4. React the product with tetrabutyllithium in the presence of ethyl tungstate to generate 2-butylcyclopentane.
5. The chlorination reaction of 2-butylcyclopentane in the presence of chlorine gas produces the product 2-chloro-9,10-dibutylanthracene.
6. Finally, heat with cuprous iodide in chloroform to obtain 9,10-dibromoanthracene.
The method obtains a product with high purity and large output, but the use cost of raw materials is relatively high.
Second, the direct bromination synthesis method of aromatic compounds:
In the direct bromination synthesis method, 9,10-dibromoanthracene is prepared from aromatic compounds through direct bromination reaction. Specific steps are as follows:
1. Dissolve anthracene in a solvent.
2. Add N-bromosuccinimide (NBS) to the solution.
3. After light irradiation, 9-bromoanthracene is prepared by bromination reaction.
4. React the product with ethyl acetate and hydrochloric acid to generate acetic acid-9-bromoanthracene.
5. React 9-bromoanthracene acetate with pentasodium iodide in excess acetonitrile solution to generate the target product 9,10-dibromoanthracene.
This method is simple and easy to operate, and is suitable for laboratory scale with small output, but the purity of the obtained product is low.
Three, copper catalytic synthesis method:
This method is an efficient green synthesis method. Grassroots reaction has gradually become a feasible preparation method after years of research. It combines electrophilic reaction and reduction reaction through the action of a catalyst to achieve an efficient and low-cost reduction reaction.
. The copper-catalyzed synthesis of 9,10-dibromoanthracene requires 9,10-dibromoanthracene, CuI, cuprocyanine and N,N-dimethylformamide (DMF). Specific steps are as follows:
Step 1: Prepare the precursor of 9,10-dibromoanthracene:
Prepare a 1.7 mol/L methanol solution of 3-bromobenzaldehyde and irradiate it under white light for 2 hours to obtain 9,10-dibromoanthracene precursor 1. Precursor 1 was dissolved in potassium hydroxide and converted to 9,10-dibromoanthracene with sulfuric acid.
Step 2: Copper Catalyzed Reaction:
Add DMF to 100 mL of dry ethylene oxide and keep it at a constant temperature of about 120°C. Add pretreated 9,10-dibromoanthracene and CuI into ethylene oxide/DMF. Subsequently, cuprous cyanogen was added three times, and stirring and reaction were carried out for 20 minutes after each addition, and the total reaction time was 1 hour.
Step 3: Separation and Subsequent Processing:
After the reaction was completed, the reaction solution was transferred to a separating funnel, and then extracted twice with a mixture of ethanol and water. Repeat this process to separate the organic matter, and extract the product again in a dry organic solvent, and finally obtain the powdery 9,10-dibromoanthracene product.
The above are the steps for preparing 9,10-dibromoanthracene by the copper-catalyzed synthesis method, which is suitable for small-scale synthesis in the laboratory. The advantages of this method include low reaction temperature, readily available catalysts, and easy separation of products. However, it should be noted that DMF is a toxic solvent, and the operating conditions need to be strictly controlled to ensure the safety of the experiment.
4. Metal-catalyzed synthesis method:
In metal-catalyzed reactions, palladium-catalyzed synthesis is a commonly used method. Specific steps are as follows:
1 Pretreatment reactor and solvent:
Clean the autoclave, magnetic stirrer, sight ports, piping, and distillation apparatus. Add 4Å molecular sieve adsorbent to the desiccator, and pressurized air flows through it to make it dry. Prepare carbon tetrachloride (CCl4) and methanol, and add molecular sieve adsorbent to them respectively and stir evenly, let stand overnight to remove water. Filter the dried CCl4 and methanol with a filter to remove the molecular sieves and store in a desiccator until use.
2 Prepare the reactants:
9,10-Anthracenedicarbaldehyde (10 g, 0.04 mol) and sodium oxide (7.1 g, 0.18 mol) were added into 100 mL of methanol, and the reaction was stirred at 75 °C for 16 h. After the reaction was finished, the reactant was filtered, rinsed with water, and bubble-washed with acetonitrile on the suction filter, and dried in a vacuum desiccator.
3 Synthesis of 9,10-Dibromoanthracene:
Dissolve the prepared 9,10-Anthracenedicarbaldehyde in 400 mL of CCl4, add 15.0 g (0.06 mol) of stannous bromide and 7.8 g (0.04 mol) of cuprous bromide, and fully stir the reaction at room temperature under a nitrogen atmosphere 24 hours. After the reaction, acetonitrile and methanol were used to elute the synthesized products respectively. After filtering the material liquid and distilling it to concentrate with a distillation device, add sulfuric acid dihydrate to PH=1 to start crystallization. A large amount of hydrohalic acid will be released during the crystallization process, so the hydrohalic acid should be discharged in time. After the crystals were washed with ice water, the water was absorbed by vacuum pump adsorbent, and then dried to obtain white crystals of 9,10-Dibromoanthracene (14.2 g, yield 79%).
4 Conclusion:
It can be seen that although the metal-catalyzed synthesis of 9,10-Dibromoanthracene has cumbersome steps, it is an efficient and reliable method for the synthesis of 9,10-Dibromoanthracene, which is suitable for medium to large-scale production. In addition, the synthesis method does not require too many reactants, is also more environmentally friendly, and will have a wide range of applications.
In summary, various synthetic routes of 9,10-dibromoanthracene have their own characteristics and advantages, and the appropriate synthetic method should be selected according to the actual situation in the specific experimental process.