N-Protected 1,2-Oxazetidines as a Source of Electrophilic Oxygen: Straightforward Access to Benzomorpholines and Related Heterocycles by Using a Reactive Tether
A hitherto unknown reactivity of a strained four‐membered heterocycle, 1,2‐oxazetidine, is reported. When reacted with organometallic compounds, this reagent provides electrophilicoxygen with a nitrogen‐terminated two‐carbon‐atom tether. The synthetic versatility of the products obtained was demonstrated in various transformations, leading to efficient synthesis of six‐, seven‐, and eight‐membered