A Study On Synthesis Of Isoxazolines With Catalytic Amount Of Hypervalent Iodine Intermediates

The topic of this dissertation is about the catalytic application of organic hypervalent iodine intermediates in synthesis of heterocyclic compound isoxazolines. A new and convenient method for preparation of isoxazolines has been developed by a catalytic cycloaddition of nitrile oxides generated in situ from aldoximes to alkenes in the presence of a catalytic amount of iodobenzene. In this protocol, iodobenzene was first oxidized into the hypervalent iodine intermediate by m-chloroperbenzoic acid, which then transformed aldoximes into nitrile oxides, following a1,3-dipolar cycloaddition of nitrile oxides to alkenes was happened to provide the isoxazolines in moderate to good yields. This new method has some advantages, such as high efficient, atom economic, convenient and environmental benign. Furthermore, the scope of hypervalent iodine reagents in organic synthesis could be extended. The thesis is divided into three chapters. The essential work is listed as follows:1. The recent progress of hypervalent iodine compounds have been reviewed, which mainly focus on the new preparation methods for the import and most useful hypervalent iodine compounds, and their utilizations in organic synthesis. 2. Utilizing a catalytic amount of hypervalent iodine reagent instead of stoichiometric hypervalent iodine reagent in my research, we have developed a new catalytic preparation of isoxazolines, which improved by a cycloaddition of nitrile oxides generated in situ from aldoximes to alkenes in the presence of a catalytic amount of iodobenzene in the solvent of TFE. This method has some advantages, such as mild reaction conditions and simple procedure, with which a series of corresponding isoxazolines have been prepared in moderate to good yields. In the research, the reaction conditions have been optimized and the mechanism of the reaction has been studied.3. On the base of successful formation of isoxazolines catalyzed by a catalytic amount of iodobenzene, a convenient one-pot, three-step procedure starting from benzaldehyde and styrene for synthesis of isoxazolines has been investigated, which has proved to be a green, environmental friendly and effective novel oxidation system. The influence of solvents on the reaction has been studied. Other reaction conditions are being optimized, the new method for "one-pot" synthesis of isoxazolines will be reported in near future.