Dimethyldioxirane oxidation of (E,E)-cinnamylideneacetophenones

The (E,E)-cinnamylideneacetophenones 1a-f were oxidised by isolated dimethyldioxirane (DMD, as acetone solution) at room temperature, giving diastereomeric mixtures of the alpha, beta:gamma,delta -diepoxides 3a-f when an excess of oxidant was used. alpha,beta -Monoepoxides, found as minor components of the reaction, could be detected in only two cases (2c,d) when one equivalent of DMD was used, Dimethyldioxirane oxidation of (E,E)-2 ' -hydroxycinnamylideneacetophenones (4a-d) led to the formation of diastereomeric mixtures of the alpha,beta:gamma,delta -diepoxides 6a-d as well as to the gamma,delta -monoepoxides 5a-d as minor products. The diepoxides 6a-d were transformed into the isolable coumaranone derivatives 7a-d during their chromatographic purification. All the compounds described have been fully characterised by NMR spectroscopy.