The present invention relates to a process for the preparation of compounds of formula I wherein R1 and R2 are each independently of the other hydrogen or C1-C5alkyl and R3 is CF3 or CF2H, by a) reaction of a compound of formula II wherein R1 and R2 are as defined for formula I, with at least one reducing agent to form a compound of formula III wherein R1 and R2 are as defined for formula I, and b) reaction of that compound with at least one reducing agent to form a compound of formula IV wherein R1 and R2 are as defined for formula I, and (c) reaction of that compound with a compound of formula V wherein Q is chlorine, fluorine, bromine, iodine, hydroxy or C1-C6alkoxy and R3 is as defined for formula I, to form the compound of formula I; and to novel intermediates for use in that process.