Study On The Metalfree Cascade Synthesis Of Nitrogen-containing Heterocyclic Compounds

Among the five member heterocyclics,imidazoles and thiadiazolidines are two kinds of important nitrogen-containing compounds,which are usually acted as the important scaffold of heterocycles in organic syntheses.Recently,their derivatives have gained considerable attention by many scientific researchers due to their extensive biological activities.Compared with some traditional methods,cascade reaction has some unique merits on the synthesis of heterocyclic compounds and has become one of the research frontiers in organic synthesis.This thesis studied on the non-metal involved cascade reaction in the synthesis of nitrogen-containing heterocyclic compounds and the research results are summerized as follows:1.A series of 2-imino/aminoimidazole derivatives were synthesized via using the carbodiimides and N-substituted or unsubstituted propargyl-amines as starting materiels,DMSO as the solvent in the presence of NaOH.The whole reaction process was via nucleophilic addition and a subsequent NaOH mediated intramolecular alkyne hydroamination from propargylamines and carbodiimides.This transition metalfree cascade process has some advantages such as mild reaction condition,easy of operation,higher yields and atom-economy.2.An I₂-induced desulfurization strategy has been developed for the synthesis of bis?alkyl/arylimino?-1,2,4-thiadiazolidine derivatives and the plausible formation mechanism has been proposed.The reaction was carried out in moderate yield with 1.1eq.I₂ and 2eq.triethylamine in EtOAc under room temperature with 1 hour.In this condition,we obtained five 2,4-dialkyl-3,5-dialkylimino-1,2,4-thiadiazolidines.When the bases were not added and EtOH was used as solvent,four2,4-diaryl-3,5-diarylimino-1,2,4-thiadiazolidines were synthesized.This method has the advantages such as readily available cheap raw materials,easy of operation and superior to step economy.