Abstract 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−]=[BF 4−],[CF 3 SO 3−],[PF 6−],[N (CF 3 SO 2) 2−]}. Various factors affecting epoxide yield (in the range 80− 99%), reaction rate and reproducibility have ...