Epoxidation of (E,E)‐Cinnamylideneacetophenones with Hydrogen Peroxide and Iodosylbenzene with Salen‐MnIII as the Catalyst

Abstract

Abstract(E,E)‐Cinnamylideneacetophenones 3a–j were epoxidized under mild conditions with Jacobsen's catalyst 4 and hydrogen peroxide or iodosylbenzene as oxidants. γ,δ‐Monoepoxides and a diastereomeric mixture of α,β:γ,δ‐diepoxides were obtained in each case, and only the α,β‐monoepoxide of 4‐nitrocinnamylideneacetophenone (3d) was isolated. The presence of a methyl group in the vinylic moiety of substrates 3i,j allowed the formation of two γ,δ‐monoepoxide diastereomers. The epoxidation of (E,E)‐2′‐hydroxycinnamylideneacetophenones 3h,j led to the formation of the corresponding γ,δ‐monoepoxides as well as (E)‐2,3‐trans‐3‐hydroxy‐2‐styryl‐4‐chromanones, which originated from the in situ cyclisation of 2,3‐epoxy‐1‐(2‐hydroxyphenyl)‐5‐phenyl‐4‐penten‐1‐ones. The structures of all new compounds and the stereochemistry of the mono‐ and diepoxide diastereomers were established by NMR studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)