Four-membered Rings with One Oxygen and One Nitrogen Atom

α-Substituted α-Lithiated Oxiranes: Useful Reactive Intermediates

“…A highly stereoselective preparation of novel β,γ-epoxyhydroxylamines and 4-hydroxyalkyl-1,2-oxazetidines based on the addition of α-lithiated aryloxiranes to nitrones has been developed …”

Construction of aziridine, azetidine, indole and quinoline-like heterocycles via Pd-mediated C–H activation/annulation strategies

“…6). 20 The more commonly known and stable N-containing four-membered heterocycles azetidine and azetidinone are well studied and these useful cyclic amines and amides have been broadly utilized in synthetic and medicinal chemistry. 21 Similar to aziridine, azetidine also contains a strained ring system.…”

Synthesis of 1,2-oxazetidines with a free –NH group via photoredox catalysis

“…Oxazetidines are highly strained four-membered heterocycles having oxygen and nitrogen as part of the ring system. 1 The oxazetidines are also distinctive in the sense that they can function as a unique imine and formaldehyde precursor as well as electrophilic oxygen source owing to the polar nature of the N–O bond (Fig. 1).…”