Diverse products accessible via [2+2] photocycloadditions of 3-aminocyclopentenones

Intra- and intermolecular [2 + 2] photocycloadditions on 3-aminocyclopentenones are described. Fragmentation of the resultant aminocyclobutanes by retro-Mannich reactions leads to the formation of diketones, ketoimines or conjugated enaminones, the latter of which can undergo further reactions to afford gamma-aminotropones and Diels-Alder adducts.