Lewis Acid Catalyzed Donor-Acceptor Cyclopropanes[3+3] Annulation

Activated cyclopropanes are important building blocks in organic syntheses. In particular, Donor-acceptor (D-A) cyclopropanes, which are doubly activated by vicinally substituted electron-withdrawing and electron-donating groups, are very useful synthetic blocks. Since they cleave readily under mild conditions to form reactive 1,3-zwitterionic intermediates, D-A cyclopropanes can participate in many reactions. Cyclization reactions are simple and effective method to construct carbocyclic and heterocyclic compounds. Therefore, great attention has been paid to explore annulation D-A cyclopropanes in organic chemistry. Although tetrahydrothiapyran structure present in many drugs, which have significant biological activity, the synthesis of those structure is rarely reported. Combined with our research on the synthesis of heterocyclic compounds, this paper studies the [3+3] annulation of Lewis acid activated D-A cyclopropane to form tetrahydrothiapyran compounds. The mainly contents are as follows:Chapter 1: This chapter describes the recently advances in D-A cyclopropane participation [3+n] cycloaddition briefly.Chapter 2: This chapter first described the common synthesis methods of tetradrothiapyrans and the recent application of mercaptoacetaldehyde in organic chemistry. Next we reported in detail on the Sc(OTf)3 catalysed [3+3] annulation of mercaptoacetaldehyde and D-A cyclopropane.