Realizing the Photoene Reaction with Alkenes under Visible Light Irradiation and Bypassing the Favored [2 + 2]-Photocycloaddition

The textbook photoreaction between two alkenes is the [2 + 2]-photocycloaddition resulting in functionalized cyclobutanes. Herein, we disclose an unusual reactivity of alkenes that favor photoene reaction over the [2 + 2]-photocycloaddition.