STUDIES ON CYCLOBUTYL BOND-CLEAVAGE BY ADJACENT KETYL RADICAL GENERATED UNDER PET CONDITIONS

A variety of adjacent cyclobutyl ketones have been subjected to a new photoelectron transfer (PET) conditions, i.e., photolysis in a protic and polar solvent EtOH with triethylamine. The cleavage of cyclobutane ketyl radical is highly substrate specific. An interesting wavelength dependence (irradiation at 254 nm vs 300 nm) phenomenon has been unco vered. The nature of chemical transformation has been shown to be a fu nction of mode of generation of ketyl radicals. In continuation, the c leavage of even adjacent cyclopentane ring is postulated to account fo r our recently discovered novel isomerization of Diels-Alder endo-isom ers to exo-adducts under PET conditions, which is quite unprecedented.