Background and overview[1][2]
Aromatic ethers such as p-chlorophenylene ether are an important type of organic synthesis intermediates and are widely used in the synthesis of medicines, dyes, spices, pesticides, etc. The commonly used synthesis method is to directly etherize phenol with alkylation reagents such as dimethyl sulfate and halogenated hydrocarbons under alkaline conditions under reflux, which takes a long time. However, phase transfer catalysts, sodium hydride, and anion exchange are used. Resin and [N(C2H5)4]F, etc. can speed up the reaction speed and increase the yield. There are also reports of using F-catalysts such as KF-Al2O3 to catalyze reactions at room temperature. Aromatic ethers have been successfully synthesized using PEG- as a catalyst and heating under solvent-free conditions. Although all these improvement measures have had certain positive effects, the response time generally still takes 5 to 10 hours. Under normal pressure conditions, aromatic ethers are synthesized by using phenol and alkylating reagents in an alkaline solution through microwave radiation. The reaction can be completed in 10 to 20 minutes.
Structure
Preparation method[1]
The preparation of p-chlorophenethyl ether is as follows: add 0.1 mol of phenol and 50 mL of 10% NaOH solution (or 0.1 mol of potassium salt of phenol and 10 mL of DMF) into a 250 mL short-necked round-bottomed flask, and place the round-bottomed flask in cold water. In the bath, drop 0.053 mol of dimethyl sulfate (or 0.11 mol of ethyl bromide) within 15 minutes under stirring. After the dripping is completed, continue stirring for 10 minutes. Put it into a microwave reactor, install a condenser tube, and use 89 to 216W power radiates. After 10 to 20 minutes (followed by TLC), take it out and cool it, pour it into 50 mL of water, then separate the oil layer, extract the water layer with benzene (30 mL × 3), combine the oil layers, wash with 5% NaOH solution, and then wash with water until neutral. Dry with anhydrous Na2SO4, evaporate the solvent and then distill under reduced pressure to obtain the product p-chlorophenylene ether. The reaction does not require the use of polytetrafluoroethylene containers, and the reaction device does not need to be sealed, thus avoiding the dangers caused by high temperature and high pressure. This is an effective method for synthesizing aromatic ethers.
Main reference materials
[1]Synthesis of aromatic ethers under microwave irradiation
