Construction of Bridged Aza- and Oxa-[ n .2.1] Skeletons via an Intramolecular Formal [3+2] Cycloaddition of Aziridines and Epoxides with Electron-Deficient Alkenes.

An intramolecular formal [3+2] cycloaddition of activated aziridines and epoxides with electron-deficient alkene has been developed for the general and efficient construction of bridged aza- and oxa-[ n .2.1] ( n = 3 or 4) skeletons. This strategy can be efficiently promoted by lithium iodide. To demonstrate its potential, the intramolecular formal [3+2] cycloaddition was used to access the important intermediate of homoepiboxidine.