A process is described for the preparation of N,N-diisopropyl-3-(2-hydroxy-5-methylphenyl)-3-phenyl-propaneamine comprising substitution of the sulfonyloxy group of the compound of the formula ##STR00001## in which the substituents R and R'' have the meanings stated in the description, in a solvent comprising an ionic liquid, to yield the tertiary amine of the formula ##STR00002## and the subsequent deprotection thereof.