This review highlights the excited state characteristics of imines and processes that govern their photochemical and photophysical properties.

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.

Intermolecular [2+2]‐photocycloaddition of atropisomeric phenyl maleimide has been evaluated with substituted alkenes with complete control over regiochemistry. We were also successful in carrying out atropselective reactions with the removal of axial chirality leading to enantio‐enriched photoproducts. Based on detailed photophysical studies, a mechanistic rationale is proposed for the observed selectivity.

This account highlights the role of restricted bond rotations to influence excited state reactivity of organic molecules. It highlights photochemical reactivity of various organic molecules and the design strategies that could be exploited by chemists to utilize restricted bond rotations to uncover new excited state reactivity and achieve selectivity.