Photochemistry of cyclopentenones : Beyond (2+2) photocycloaddition reactions

摘要: The aim of this project was to explore the scope and limitations a tandem photochemical process, consisting [2+2] cycloaddition between cyclopentenones alkenes followed by Norrish I/γ-hydrogen transfer reaction if initial bicyclic adduct is formed. Using standard synthetic procedures, small library cyclopentenone substrates prepared. development new methods access substituted cyclopentenones, using organocatalyzed aldolisation conditions, considered; however, these efforts were unfruitful.The studies showed that selection could react together furnish cyclobutene aldehydes with average good yields. conditions optimized for formation specific compound type, some as regards substrate diversity determined. In cases, control regioselectivity Norrish-I process problematic.In course study, it discovered themselves photochemically, via an intramolecular Paterno–Buchi reaction, form hitherto unknown tricyclic oxetanes. This constitutes one-pot triple sequence starting cyclopenenones alkenes. Conditions transformation several examples core structure studied in detail, both solution solid state, revealing had been highly diastereoselective examples. Some limitations, arising from steric hindrance and/or use electron rich alkenes, constituted limitation process.