. . . . . . . . "The (+), (-) and (???) forms of the compounds having the general formula I ##STR12## wherein R1 is hydrogen or a methoxy, ethoxy, propoxy, methylthio, ethylthio, propylthio, fluoro, chloro, bromo, methyl, ethyl, nitro or amino group, and R2 is a hydrogen or methyl group and R3 is the group ##STR13## and R4 and R5 are the same or different groups and each is a fluoro, bromo or chloro group." . .