Patent ID: 8124782

Claim:
A process for preparing the compound of the formula (I) which comprises, in a first step, reacting the compound of the formula (V) with 4-chloro-3-trifluoromethylphenyl isocyanate in a nonchlorinated organic solvent, inert toward isocyanates, by initially charging the compound of the formula (V) at a temperature of from 20° C. to 60° C. and admixing with 4-chloro-3-trifluoromethylphenyl isocyanate in such a way that the reaction temperature does not exceed 70° C. to give the compound of the formula (II) and, in a second step, admixing the compound of the formula (II) with p-toluenesulfonic acid in a polar solvent at a reaction temperature of from 40° C. up to the reflux temperature of the solvent used.