Compounds of formula (I) wherein R3 represents C1-6alkyl substituted with cyano, said R3 being represented by C1-6alkyl-CN and said compounds being represented by formula (I-c), can be prepared by reacting an intermediate of formula (VII) wherein W3 represents a suitable leaving group, such as for example, halo, e.g. chloro, with a suitable cyanide salt, such as for example sodium cyanide or potas