Visible-Light-Driven Intermolecular [2+2] Cycloadditions between Coumarin-3-Carboxylates and Acrylamide Analogs

This paper reports a room temperature visible-light-driven protocol for the intermolecular [2+2] cycloadditions between coumarin-3-carboxylates and acrylamides analogs by an energy-transfer process. Using an iridium complex FIrPic as a photosensitizer and a 3W blue LED as a light source, an array of cyclobutabenzocypyranones were prepared in moderate to excellent yields.