Synthesis Research Of Fluorinated Isoxazole Derivatives

The main work of this dissertation is focused on synthesis of multi-substituted fluorinated isoxazole derivatives, which includes two parts:the first part is to synthesize 4-polyfluoroalkyl isoxazole-5-acyl derivatives, which was promoted by NIS; The second part is to synthesis of 4 polyfluoroalkyl isoxazole-5-alkyl derivatives, which was promoted by protonic acid.first, in the first part of this dissertation, we have developed a new method for the synthesis of 4-polyfluoroalkyl isoxazole-5-acyl derivatives. This method makes use of a variety of cheap and readily available fluorinated alkyne-containing hydroxylamine as starting material, NIS as an oxidant to produce oxime intermediates and subsequent electrophilic cyclization reaction, which provide a one-pot method for synthesis of 4-polyfluoroalkyl-5-acyl isoxazole derivative. This novel synthetic method was featured with readily available starting materials, good yields and ease of operation under mild reactions condition and the ease of further transformation of the products.Based on the first part of this dissertation, we find that oxime intermediate could undergo electrophilic cyclization to afford 4-polyfluoroalkyl isoxazole-5-acyl derivatives by adding an appropriate amount of sodium thiosulfate to the reaction system timely to quench the iodide ions. Therefore, a new method for the synthesis of 4-polyfluoroalkyl isoxazole-5-acyl derivatives was developed in the second part of this dissertation.