C-10-Fluorinated derivatives of dihydroartemisinin: difluoromethylene ketones

Difluoroenoxysilanes, prepared from aromatic and heterocyclic ketones, reacted with dihydroartemisinin acetate in the presence of Lewis acid to provide in good to moderate yields the 10-substituted difluoromethylene ketones. The introduction of the difluoromethylketone moiety was accompanied by the epimerisation of C-9. Best results were obtained using SnCl4 as Lewis acid.