Oxidative Cyclization Of ?,?-unsaturated Acylhydrazone And Trifluoromethylated Allenyl Hydrazide

Pyrazoles have unique physical and chemical properties and biological activities,which have been widely used in drugs and pesticides,and in other fields.The traditional method of preparing substituted pyrazoles is the condensation of hydrazines with 1,3-dicarbonyl compounds or [3 + 2] cycloaddition.In the past decade,the search for novel and efficient synthesis methods of pyrazole derivatives has been developed rapidly.In this thesis,the progress in the synthesis of pyrazoles in recent ten years was reviewed.On this basis,we have synthesized a variety of N-acylpyrazoles from ?,?-unsaturated acylhydrazones under mild conditions.And a "one pot" reaction of trifluoromethyl hemiacetal,hydrazide and 3-substituted propargyl bromide was explored promoted of tin powder to obtain trifluoromethylated allenyl hydrazides,and then the trifluoromethyl pyrazoles were synthesized by oxidation and cyclization of trifluoromethylated allenyl hydrazides.The thesis includes three chapters:Chapter one: Progress in Syntheses of Pyrazole DerivativesIn this chapter,the progress in the synthesis of pyrazoles in recent ten years was introduced.It was mainly reviewed the application of new reaction strategies,new reaction technologies(polar aprotic solvent,fluorinated solvent,microwave radiation,etc.)and new reagents in the construction of pyrazoles.Chapter two: Synthesizes N-acyl Pyrazoles Through Oxidative Cyclization of ?,?-unsaturated AcylhydrazoneIn this chapter,a series of potentially biologically active N-acylpyrazoles compounds were synthesized by the oxidative cyclization of ?,?-unsaturated acylhydrazones using iodobenzene acetate as a oxidant.The method has the characteristics of mild reaction conditions,short reaction time,easy operation and high reaction yield it provides a new method for synthesizing N-acylpyrazole compounds.At the same time,this method also expands the application range of acylhydrazones as a building block in organic synthesis.Chapter three: Study on the reaction of tin powder promoted by trifluoromethyl hemiacetal,hydrazides and 3-substituted propargyl bromidesThis chapter explores the synthesis of trifluoromethyl allenyl hydrazides by "one-pot" reaction of trifluoroacetaldehyde methyl hemiacetal,hydrazides,and 3-substituted propargyl bromides under reflux condition promoted by tin powder with high selectivity N'-(1,1,1-trifluoro-3-methylpent-3,4-dien-2-yl)substituted hydrazides were further cyclized to obtain trifluoromethylated pyrazoles.A new way is provided for the synthesis of trifluoromethylated pyrazoles.