Facile Synthesis of Azetidine Nitrones and Diastereoselective Conversion into Densely Substituted Azetidines.

An electrocyclization route to azetidine nitrones from N-alkenylnitrones was discovered that provides facile access to these unsaturated strained heterocycles. Reactivity studies showed that these compounds undergo a variety of reduction, cycloaddition, and nucleophilic addition reactions to form highly substituted azetidines with excellent diastereoselectivity. Taken together, these transformations provide a fundamentally different approach to azetidine synthesis than traditional cyclization by nucleophilic displacement and provide novel access to a variety of underexplored strained heterocyclic compounds.