Overview of Photochemical Reactions for the Synthesis of Aza and Oxa-Spirocyclic Compounds Under Visible Light Irradiation.

Photochemical reactions play a significant role in organic transformation, the synthesis of natural products, and the development of advanced materials. This elegant approach has been widely explored for the construction of biologically active architectures that are often difficult to access through conventional thermal methods. Spirocyclic compounds represent an important class of compounds found in various approved drug candidates. This review summarizes the myriad photochemical reactions, particularly the visible-light-driven synthesis of aza, oxa, and aza-oxa spirocyclic compounds, reported during the periods 2015-2025. Most of the reactions discussed in this review are one-pot synthetic approaches to access the desired spirocyclic product with excellent yield and regioselectivity. Overall, this review highlights the significance of photochemical methods as powerful tools for the sustainable construction of natural and synthetic spirocyclic scaffolds.