Metal-Free Visible Light-Mediated Photocatalysis: Controlling Intramolecular [2 + 2] Photocycloaddition of Enones through Axial Chirality

Atropisomeric
enone-imides and enone-amides featuring N-CAryl bond rotation were evaluated for intramolecular
[2 + 2] photocycloaddition. Straight addition product was observed
over cross-addition product with good control over reactivity. The
atropselectivity was found to be dependent on the substituent on the
aryl ring. Substitution-dependent atropselectivity was rationalized
on the basis of a divergent mechanistic pathway.