Three α-cyclopropylβ-dicarbonylcompounds have been used as probes for α-radicals as electrophilic reaction intermediates in a cerium-catalyzedα-hydroxylationreaction with molecularoxygen. Since the cyclopropyl group did not ring-open to products with a butenyl moiety, but was retained in the products, a localized unpaired electron at the α position can be excluded during the course of the reaction