Room-temperature imidazolium ionic liquids, [Rmim][X], proved to be environmentally benign recyclable solvents promoting the Michaelis–Arbuzov rearrangement, which can be performed even at room temperature in a short period of time. The best ionic liquid of choice depended on the starting phosphorus(III) ester, namely, for triethyl phosphite [bmim][NTf2] demonstrated better results while for ethyl diphenylphosphinite it was [hmim][Br].