5-Acetyl-2-thiopheneboronic acid is an organic boron compound, its chemical formula is C6H7BO3S, it is an organic synthesis intermediate with important application value, widely used in medicine Chemistry, material chemistry, life science and other fields. Among them, it plays an important role in the preparation of heterocyclic compounds, because this compound is widely used as a catalyst, reagent, protecting group, etc. in the synthesis of thiophene derivatives.
In the field of medicine, derivatives of 5-acetyl-2-thiophene boronic acid are widely used in the research and development of anticancer drugs. They enhance their efficacy by combining with nitrogen mustard and cyclophosphamide in anticancer drugs. and stability.
In the field of material chemistry, 5-acetyl-2-thiophene boronic acid is also widely used in the synthesis of organic semiconductors. As an efficient organic compound, it can effectively improve the conductivity and photoelectric properties of organic semiconductor materials, thereby realizing the preparation of high-performance organic electronic devices.
5-acetyl-2-thiophene boronic acid has broad application prospects and plays an important role in various fields. Therefore, its synthetic method is particularly important, and the specific synthetic methods are as follows:
1. The Knorr Synthesis: According to the Knorr synthesis method, first react 2-propenylthiourea and ethyl borate in ethanol, then add sodium acetate and heat in water vapor to obtain 5-acetylthiophene-2-boronic acid ethyl ester. Subsequently, ethyl 5-acetylthiophene-2-boronic acid was added into sodium hydroxide solution, and heated for 2 hours to remove the ester group to obtain 5-Acetyl-2-thiopheneboronic acid. The specific detailed steps are as follows:
(1.) The first step is to synthesize 2-amino-5-(acetyl)-2,3-dihydrothiophene (2-Acetylthiophene-3-carboxylic acid methyl ester).
Add methyl thioacetate to dimethylformamide (DMF), add a certain amount of ammonium sulfate catalyst, stir and heat for a certain period of time to generate 2-amino-5-(acetyl)-2,3-di Hydrothiophene. After the reaction is over, adjust the reaction solution to weak acidity, then add it into the perchloric acid mixture, and shake the reaction bottle back and forth. Finally, the water-insoluble part in the reaction solution was removed and dried to obtain the target product.
(2.) The second step is the acylation reaction of 2-amino-5-acetylthiophene.
Add potassium hydroxide (KOH) to the reaction solution and adjust the pH to 10-11. Subsequently, benzoyl chloride was added dropwise in the solution and heated for 30 minutes. After the reaction, the reaction solution was acidified with dilute hydrochloric acid, and a solid substance was precipitated.
(3.) The third step is the synthesis of 5-Acetyl-2-thiopheneboronic acid.
The reactants were repeatedly dissolved in water and graphite for dehydration, and then boron trihydroxide (BHA) was added for orthoboration to form pentasubstituted pyrrolidones.
In summary, The Knorr Synthesis method of 5-Acetyl-2-thiopheneboronic acid mainly includes three-step reactions: synthesis of 2-amino-5-(acetyl)-2,3-dihydrothiophene, 2-amino-5-acetyl Acylation reaction of thiophene and synthesis of 5-Acetyl-2-thiopheneboronic acid.
2. The Borylation Reaction: 5-bromo-2'-acetylthiophene and PinBCl (2-ethylphenyltrifluoroboron) were reacted in DMF in the presence of tributylphosphine and potassium sodium carbonate to obtain 5-Acetyl -2-thiophene boronic acid. The following are the detailed steps of The Borylation Reaction method of 5-Acetyl-2-thiopheneboronic acid:
(1.) Preparation materials: 5-Acetyl-2-thiopheneboronic acid, Palladium acetate, Triphenylphosphine, sodium carbonate, sodium hydroxide, methanol, acetone, distilled water, nitrogen cylinder, reaction kettle, hot water bath, separatory funnel, etc. .
(2.) Prepare the solution of reactants: Dissolve 5-Acetyl-2-thiopheneboronic acid and Triphenylphosphine in acetone respectively, and stir well.
(3.) Fill the reactor with nitrogen gas.
(4.) Add sodium carbonate to the reaction kettle, and then add methanol.
(5.) Add Palladium acetate and stir.
(6.) Add the mixed liquid of 5-Acetyl-2-thiopheneboronic acid and Triphenylphosphine, and stir.
(7.) Set the hot water bath to the proper temperature.
(8.) Use nitrogen gas to flush the gas inside the reactor until bubbles are observed, indicating that the reaction has started.
(9.) Add the reaction mixture into the reactor. Considering the overflow situation, it is recommended to only add 1/3 of the reactor.
(10.) Raise the temperature of the hot water bath to the proper temperature.
(11.) The reaction mixture was stirred.
(12.) Monitor the temperature and color change of the reaction mixture during the reaction.
(13.) After the reaction, use distilled water and sodium hydroxide to extract the reaction mixture, and then use a separatory funnel to separate the separated product from the bottom layer.
(14.) The isolated product is dried and purified.
(15.) Finally, use the method to confirm the structure and purity of the product.
In short, this is a relatively complicated chemical reaction, which requires scientists to have high chemical experiment techniques and safety knowledge in order to carry out the synthesis reaction smoothly.
3. The Suzuki Reaction: The Suzuki Reaction is a commonly used palladium-catalyzed coupling reaction that can be used to synthesize aromatic compounds. It is achieved by reacting boron-containing organic compounds (such as borates) with halogenated aromatic hydrocarbons under the catalysis of palladium ligands.
The following is the Suzuki reaction steps for 5-Acetyl-2-thiopheneboronic acid:
(1.) Preparation of reactants: Prepare 5-Acetyl-2-thiopheneboronic acid and halogenated aromatic hydrocarbons, such as benzene bromide.
(2.) Reaction conditions: The reaction is carried out in a mixed solvent of ethanol and water, and palladium ligand and potassium carbonate catalyst are added.
(3.) Reaction process: After 20-30 minutes, start to add halogenated aromatic hydrocarbons, and keep the reaction temperature at 80-100°C. After the reaction, the solution was cooled to room temperature.
(4.) Product isolation: filter the catalyst, wash the precipitate with water and ethanol to remove unreacted compounds.
(5.) Purification of the product: the product was purified on a persilicate silica gel column in a mixed solvent of chloroform/methanol.
4. The Oxidation of 5-Acetyl-2-thiophenol: 5-Acetyl-2-thiophenol is reacted with nitrous acid to obtain 5-nitro-2-acetylthiophene, then reduced with nitrous acid, and then protonated to obtain 5 -Acetyl-2-thiopheneboronic acid.
The specific steps are as follows:
(1.) First, dissolve 5-Acetyl-2-thiophenol in methanol and add NaOH solution, stir to mix.
(2.) Heat the solution to 90°C, and slowly add H2O2 dropwise.
(3.) After adding H2O2 dropwise, continue to heat the solution until the reaction is complete to form 5-Acetyl-2-thiopheneboronic acid.
(4.) The reaction mixture was cooled to room temperature, and 5-Acetyl-2-thiopheneboronic acid was extracted with ethyl acetate.
(5.) The organic layer was filtered and concentrated, and finally precipitated with ethanol.
The above are the detailed steps of The Oxidation of 5-Acetyl-2-thiophenol method of 5-Acetyl-2-thiopheneboronic acid.