Reactivity Of Four-Membered AZA-Heterocycles Based On Carbodiimide

Four-membered aza-heterocycles are a class of important small hetero-cyclic compounds, which have many applications in pharmaceutical, biological and organic chemistry. Due to the ring strain, reactions of four-membered aza-heterocycles could proceed easily to give nitrogen-containing molecules which fulfill further synthetic transformation. Therefore, the study of the synthetic methodologies of four-membered aza-heterocycles has important theoretical significance and application value.Recently, we have disclosed that Cul catalyzed three-component reaction of terminal alkynes, sulfonyl azides, carbodiimides for the facile synthesis of the2,4-diiminoazetidine derivatives. According to these, the chapter one will introduce the summary of synthetic transformations of four-membered aza-heterocycles.Based on the previous research, the ring-opening of2,4-diiminoazetidines via the C-N bond cleavage reactions under acid/base conditions is elaborated in chapter2, and two different kinds of amide amidine compounds were synthesized. In chapter3:Promoted n-BuLi, spJ C-H bond cleavage of2,4-diimino azetidine was realized. Due to the high strain force of2,4-diimino azetidine, the C-N bond of the four-membered ring was then cleavaged. Followed by1,5-hydride transfer, the resulting intermediate undergoes rapidly6π electrocyclic ring-closing to afford the desired2,3-dihydropyridimines.The ring-opening and ring-expansion reactions of2,4-diiminoazetidines show the advantages such as simple experimental procedure, step economy, which provides a novel base for the further studies of the relevant reactions.