Mechanistic studies of the formation of cyclopropane-bearing systems through photoconversion of tropolone Diels–Alder adducts

Irradiation of alkyltropolone Diels–Alder adducts bearing β,γ-unsaturated ketone chromophores leads to fused polycyclic systems containing cyclopropane moieties in good yields. A detailed mechanistic study, which included the use of deuterium labeling in combination with HRMS and NMR experiments, revealed that the process is highly stereoselective, proceeds through the formation of allyl radical and ketene intermediates, and involves participation of the solvent.