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.