Synthesis of Azetidines via Visible Light-Mediated Intermolecular [2+2] Photocycloaddition

Intermolecular [2+2] photocycloadditions represent a powerful method for the synthesis of highly strained, four-membered rings. While this approach is commonly employed for the synthesis of oxetanes and cyclobutanes, the synthesis of azetidines via intermolecular aza Paternò-Büchi reactions remains highly underdeveloped. Herein we report a visible light-mediated intermolecular aza Paternò-Büchi reaction that utilizes glyoxylate oximes as reactive intermediates activated via triplet energy transfer. This approach is characterized by its operational simplicity, mild conditions and broad scope, and allows for the synthesis of highly functionalized azetidines from readily available precursors.