An efficient procedure is described for the epoxidation of electron-deficient olefins, in particular Vitamin K-3 and analogues, with aqueous basic solutions of hydrogen peroxide in different ambient temperature ionic liquids (ILs) [bmim(+)][X-] {[bmim(+)] = 1-butyl-3-methylimidazolium; [X-] = [BF4-], [CF3SO3-], [PF6-] [N(CF3SO2)(2)(-)]}. Various factors affecting epoxide yield (in the range 80-99%), reaction rate and reproducibility have been examined. The almost quantitative extraction of the epoxides from the reaction media has been obtained with supercritical CO2. The ionic liquid was then recovered and reused in subsequent cycles. (C) Wiley-VCH Verlag GmbH & Co.KGaA, 69451 Weinheim, Germany, 2003.