Tandem Annulation Reactions Based On Sulfur Ylides

Heterocyclic compounds account for more than 50% of the total known organic compounds.As important structural motifs,heterocyclic compounds play an important role in the fields of medicine,pesticides and functional materials.Therefore,how to synthesize heterocyclic compounds simply and efficiently is an important research field in organic synthesis.The thesis is mainly focused on highly reactivity of in situ generated sulfur ylide,two kinds of N-heterocycles were obtained with high efficiency:The catalyst-free [4+1]-annulation of ?-halo ketone oxime with trifluoroethyldiphenylsulfonium triflate is developed.This protocol provides a novel and efficient method for the synthesis of 5-(trifluoromethyl)isoxazolines in moderate to excellent yields.The transformation involves in situ generation of the reactive nitrosoalkenes under mild conditions,and trapping with in situ formed unstable trifluoroethylidenesulfur ylide.In addition,5-trifluoromethyl isoxazole was synthesized by [4+1]-annulation of ?,?-dihalooxime with trifluoroethyldiphenylsulfonium triflate One strategy is to construct two kinds of trifluoromethyl substituted five membered heterocycles by simply adjusting the substituents of substrates.The base-induced unprecedented tandem [4+2] and [1+2] annulation reaction of in situ formed aza-o-quinone methides generated in situ from o-aminobenzyl chloride and crotonate-derived sulfur ylides is developed.This protocol provides a novel and practical method for the synthesis of cyclopropane-fused tetrahydroquinolines with a quaternary carbon center in moderate to excellent yields.In this tandem reaction,three new bonds were formed in one pot,and the crotonate-derived sulfur ylide serves as a C3 synthon.This protocol features mild conditions,high efficiency,and wide substrate scopes.