Intermolecular [2+2] Photocycloaddition of β-Nitrostyrenes to Olefins upon Irradiation with Visible Light

Article abstract of DOI:10.1055/s-0036-1588524

The title compounds were found to undergo a [2+2] photocycloaddition with olefins at λ = 419 nm in CH ₂ Cl ₂ as the solvent. The resulting cyclobutanes were isolated in yields of 32-87% (11 examples) and showed a defined relative configuration at C1/C4 in the major diastereoisomer (nitro and aryl trans). The analysis of side products and triplet sensitization experiments support a mechanistic scenario in which a 1,4-diradical is formed as a key intermediate.