Synthesis of various cyclic azomethine imines, nitrones and the investigation of their 1,3-dipolar addition reactions

1,3-Dipolar cycloaddition reactions can be regarded as one of the versatile method for the synthesis of five membered heterocycles. Pyrazolidinone and isoxazolidine containing heterocycles have been comprehensively studied for a long time since they are found in the structure of naturally occuring products and bioactive compounds. Also, it is known that isoxazoles constitute a useful heterocyclic ring system in preparing new biologically active molecules. In order to reach these heterocycles, in this PhD dissertation, various dipolarophiles have been utilized in the cycloaddition reaction of both azomethine imines and nitrones. The outcomes of present study were divided into four parts; In the first part, N,N-cyclic azomethine imines were prepared according to the literature method and characterized. Then, they were subjected to undergo cycloaddition reaction with benzothiophene 1,1-dioxide to give benzothiophenedioxide fused pyrazolidinones. Secondly, we investigated 1,3-dipolar cycloaddition of both phenylsulfonylacrylonitriles and (E)-3-(2-hydroxyphenyl)-2-(phenylsulfonyl)acrylonitrile with N,N-cyclic azomethine imines. These attempted 1,3-DC reactions unexpectedly gave same cycloaddition products regioselectively. In the third part, we aimed to synthesize aldehydes bearing isoxazole unit to furnish the precursors of new N,N-cyclic azomethine imines. Then, N,N-azomethine imines were synthesized by the use of newly prepared aldehydes and characterized. Followed their cycloaddition reaction were investigated under microwave irradiation by using some electron poor or rich dipolarophiles, namely, dimethylacetylenedicarboxylate, phenylvinyl sulfone and N-vinylimidazole. Lastly, new nitrones were prepared by utilizing isoxazole containing aldehydes and characterized, followed by their 1,3-dipolar cycloaddition reactions were carried out with phenyl vinyl sulfone and N-vinylimidazole to yield both isoxazole and isoxazolidine containing cycloaddition products.