Patent ID: 7365210

Claim:
A process for preparing chiral imidazolidin-2-ones of the general formula I in which R 1 is C 1 -C 8 -alkyl, cyclohexyl, phenyl, a C 1 -C 6 -alkyl-, halo-, nitro-, C 1 -C 6 -alkoxy-, C 1 -C 6 -alkylmercapto- or CF 3 -substituted phenyl radical, naphthyl or a C 1 -C 6 -alkyl-, halo-, nitro-, C 1 -C 6 -alkoxy- or CF 3 -substituted naphthyl radical, R 2 is C 1 -C 8 -alkyl, C 2 -C 8 -alkenyl, cyclohexyl, phenyl or a phenyl-C 1 -C 6 -alkyl radical which may be substituted by a nitro, C 1 -C 6 -alkoxy, methylenedioxy or CF 3 radical, and R 3 is C 1 -C 12 -alkyl, C 2 -C 8 -alkenyl, cyclohexyl, phenyl or a C 1 -C 6 -alkyl-, halo-, nitro-, C 1 -C 6 -alkoxy-, methylenedioxy-, dialkylamino- or CF 3 -substituted phenyl radical, by reacting a compound of the formula II or the salt thereof in which R 1 , R 2 and R 3 have the abovementioned meaning, with urea in the presence of an ammonium salt, wherein the reaction is carried out in the presence of a polar organic solvent and the reaction takes place in solution at temperatures of from 170 to 190° C., and wherein the reaction is carried out in the presence of proton donors, wherein an acid with a pKa of ≦3 is used as proton donor.