Study On The Selective Carbon-Carbon Bond Cleavage And Transformation Of Aziridines Derivates Catalyzed By Lewis Acid

Aziridines, an important intermediate for organic synthesis and structural units for physiological active compounds, have been widely used in the synthesis of natural products and drug molecules. Aziridines have a high reactivity due to its highly strained ring. In general, the most reaction of aziridines reported carbon-nitrogen bond breaking those transform through carbon-carbon bond breaking are rarely reported result from the relatively lower energy barrier of C-N breaking than that of C-C breaking. The carbon-carbon bond breaking of aziridines was to be achieved only under thermal and photochemistry conditions in the past. Thus, it is a significance progress if C-C bond cleavage can be achieved under mild conditions. Based on our recent success in epoxide chemistry, we studied on the chemistry ofN-Ts aziridines.Part I:Study on the [3+2] cycloaddition reactions with electron-rich alkenewe have successfully demonstrated an efficient formal [3+2] cycloaddition of electron-rich alkene and azomethine ylide obtained from Y(OTf)3catalyzed C-C bond cleavage ofN-tosyl aziridine under room temperature, providing highly substituted pyrrolidines in good yields. This cycloaddition reaction is believed to proceed via a stepwise reaction pathway by the configuration of the product and we obtain moderate enantioselective through preliminary screening.Part II:Study on the [3+2] cycloaddition reactions with electron-rich alkynesWe have successfully demonstrated the reaction of alkynes and reactive N-tosylazomethine ylides by Lewis acid catalyzed C-C bond cleavage under room temperature, providing highly substituted3-pyrrolines as a single regioisomer. We found that this reaction have a very good chemoselectivity for different functional groups while the further conversion of the products. It is worth mentioning that this cycloaddition reaction was first reported.Part III:Study on the asymmetric catalysis of cycloaddition reactionWe found that the moderate enantioselective can be achieved after screening the chiral ligand though the preliminary results of the cycloaddition reaction. These results are not satisfied, but which encourage us for forth studies in this field.