Tandem Annulation Reactions Based On Sulfur Ylides And Halohydrazone

Nitrogen-containing heterocycles are widely considered to be an important part of natural products and drug molecules,materials with various properties,and agrochemicals with significant activity,and are one of a popular direction in modern organic synthetic chemistry.This thesis carried out related research work based on the azadiene generated in situ by the hydrazone and the tandem cyclization reaction involving 1,3-dipole nitrile imine,and successfully realized two types of nitrogen-containing heterocycles with high efficiency:The base-induced an inverse-electron-demand aza-Diels-Alder reaction between azadiene generated in situ from ?-halohydrazone and formaldehyde imine generated in situ from 1,3,5-triazine is developed.This protocol provides an efficient method for the synthesis of 1,2,4-triazine derivatives.This method has the advantages of wide substrate application range,mild reaction conditions,high regioselectivity,good reaction tolerance and operation substitution.The base-induced unprecedented tandem annulation reaction of in situ formed nitrile imine generated in situ from 1,3-dipoles nitrile imine and sulfonium salt is described.This protocol provides a novel and practical method for the synthesis of pyrazoline derivatives with a quaternary carbon center in good to excellent yields.Through the study of the reaction mechanism,it is found that the reaction is a reaction between two molecules of sulfonium salt and one molecule of halohydrazone.A molecule of sulphur ylide first undergoes a [3+2] tandem cyclization reaction with1,3-dipoles,and then undergoes a nucleophilic ring opening process with another molecular sulphur ylide.