Dioxirane Epoxidation of α,β‐Unsaturated Ketones

The synthesis of epoxides 3a – r is achieved in excellent yields by reaction of the α,β‐unsaturated ketones 1a – c , 4,4′‐disubstituted ( E )‐chalcones 1d – o , and 2′‐hydroxy‐4‐substituted ( E )‐chalcones 1p – r with isolated dimethyldioxirane ( 2a ) (as acetone solution) and/or in situ generated ethyl(methyl)dioxirane ( 2b ). This method constitutes a useful alternative to the Weitz‐Scheffer epoxidation (alkaline H 2 O 2 ) of such electronpoor substrates.