Study On Catalytic Functionalized Ester/Heterocyclic Aromatic Bromide Based On Lewis Acid

In the past decades,the research and application of new catalysts and catalytic systems have greatly promoted the development of chemistry.Some reactions previously unperformed or difficult to conduct can be carried out smoothly under mild conditions.Lewis acid is a common acid catalyst that is not only efficient but also can be stable in the air.The rapid development of organic synthesis catalyzed or promoted by Lewis acid has attracted much attention in the past few years.So far,Lewis acid catalysis has been widely used in the construction of C-C and C-N,the bromination of aromatics,the functionalization or hydrogenation of C-H,and the esterification of C-O,and it has become an effective mean to obtain important fine organic chemicals.However,it is still very important to find a simple,safe,effective and environmentally friendly synthetic route.The dissertation focuses on catalytic functionalized ester or heterocyclic aromatic bromide based on Lewis acid,and is composed of two parts:1.Synthesis of ester compounds by cracking C-O bond catalyzed by trifluoromethanesulfonic acidWe proposed a new route to prepare functionalized ester compounds by cracking C-O bond catalyzed by trifluoromethanesulfonic acid(HOTf)in the presence of 1-methyl-2-pyrrolidone(NMP).First,the C-O bond of aryl alkyl ether was cracked with the action of HOTf to generate benzyl positive ions in the presence of chlorobenzene solvent.Then,benzyl positive ions reacted with functional acid to generate functional ester.After the target product was successfully obtained on a template reaction,reaction parameters such as the catalyst,the reaction solvent and the amount of NMP were optimized to find a much better reaction condition for the preparation of functional ester compounds.After that,the scope of the substrate applied in this reaction was discussed and the preparation of functional ester on the gram scale was successfully carried out.The research of reaction mechanism suggested that the NMP played an important role in this transformation process.It was not only an inhibitor of the Fridel-Crafts alkylation reaction between benzyl-positive ion and chlorobenzene but also a promoter for the formation of functional esters by the nucleophilic attack of functional acids.These results can help chemists to work on developing new methods to restrain the Fridel-Crafts alkylation process and prepare other functional compounds in the presence of NMP.2.Synthesis of heterocyclic aryl bromides by cracking C-H bond promoted by oxygenWe proposed a new route to prepare heterocyclic aryl bromides by the oxidative halogenation using dimethyl sulfoxide(DMSO)as the solvent,Li Br as the halogenating agent,oxygen as the oxidant,and BF3.Et2 O as the catalyst.After the target product was successfully achieved on a template reaction,reaction parameters such as catalyst,reactive solvent and halogenating reagent were optimized to find a much better reaction condition for the preparation.The scope of the substrate used in this reaction was discussed under the optimal condition and the preparation of heterocyclic aryl bromides on the gram scale could be smoothly carried out.The synthetic route has the characteristics of simple and easily obtained raw materials,mild reaction condition,low cost,and good substrate adaptability.