Synthesis of azetidines by aza Paterno-Buchi reactions

The [2 + 2] photocycloaddition reaction between an imine and an alkene component, the aza Paterno-Buchi reaction, is one of the most efficient ways to synthesize functionalized azetidines. However, the application of the aza Paterno-Buchi reaction has been met with limited success due to the inherent challenges associated with this approach. This review covers the current scope and limitations of reported examples of aza Paterno-Buchi reactions in organic synthesis. An outlook is provided, which highlights recent improvements and the discovery of new reaction protocols that have overcome some long-standing challenges within this field of research.