Study On The Constructions Of Nitrogen-Containing Heterocycles Via Para-tosylhydrazone Derivatives

Nitrogen-containing heterocyclic skeletons are widely found in various natural products,pharmaceutical molecules and functional materials.Hence,the significance of synthesizing these compounds is self-evident.Previously,noble metal catalysts like palladium or rhodium complexes have been regarded as one of the most effective methods to realize such transformations.However,due to the increasing scarcity of noble metals,how to achieve similar transformations with the assistance of cheap metals even under non-metal conditions is still a challenging subject.In this thesis,our study mainly focused on the multi-step tandem reactions between hydrazones and diselenides.With the promotion of iron salts,a series of nitrogen-containing heterocyclic molecules bearing C-Se bonds were successfully obtained.The whole work could be divided into two parts as follow:Firstly,a novel Iron(?)chloride-promoted annulation reaction for the generation of 4-selenopyrazole derivatives from ?,?-alkynic tosylhydrazones and diselenides was reported.This strategy featured easily-synthesized and commercially-available start materials and afforded corresponding products in moderate to excellent yields in most instances under rather mild reaction conditions.The protocol also showed high tolerances to various functional groups.Secondary,we developed an efficient Iron(?)chloride mediated annulation reaction for the synthesis of N-iminoisoquinoline ylide by using 2-alkynylbenzaldehydrazides and diselenides as starting materials,which possessed a phenylselenyl substituent at C4 could be produced via one-step building of C-Se bond and C-N bond.This reaction avoided using expensive transition metals and constructed the C-Se bond and C-N bond in one step.Aryl,heteroaryl or alkyl diselenyl ethers were all compatible with this system.Considering the importance of the 1,3-dipole and selenium ether structures in organic synthesis,the discovery of this N-Ylide containing C-Se bonds will be an efficient tool for the construction of more complicated nitrogen-containing heterocyclic compounds.