| 2,4-dichloroquinolines are vital synthetic blocks in organic synthesis,at the same time,they have a wide range of applications in the fields of pharmaceutical research and luminescent materials,therefore,it’s significant to study the synthetic methods of2,4-dichloroquinolines.In the past few decades,the synthesis of 2,4-dichloroquinolines mainly based on the chlorination of quinoline-2,4-dione,triggered by dangerous and toxic phosphorus oxychloride and phosphorus pentachloride,although a series of new chlorination systems have been developed in recent years,these chlorination systems were the same as Apple reagent systems apparently and produced a large amount of triphenylphosphine oxide as by-product.In addition,electrochemical synthesis and other synthetic methods have been reported gradually,however,the problems of long reaction time,multiple steps,difficult preparation of substrates and low functional group compatibility have not been solved efficiently.In view of those condition,a onepot tandem cyclization/chlorination strategy are developed for the synthesis of 2,4-dichloroquinoline compounds from α-substituted acetanilide and triphenylphosphine oxide/triphosgene system,it should be noted that triphosgene not only serves as one carbon synthon,but also good source of chlorine.Mechanism studies show that α-substituted acetanilide is first chlorinated in acidic environment to give enamine esters,which are chloroformylated with((chlorocarbonyl)oxy)triphenylphosphine generated by triphenylphosphine oxide/triphosgene,and subsequently cyclizing into quinolin-4-ones,which is deoxygenated by dichlorotriphenylphosphine to get the target compound.The highlights of this thesis are utilizing simple substrates,relatively novel and manipulable chlorination system(triphenylphosphine oxide/triphosgene),moreover,this method is simple and efficient,giving high yields and extensive functional groups compatibility,triphenylphosphine oxide in the reaction can be recycled. |
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