. . . "C., in an inert organic solvent in the presence of a base ##STR4##IIa (Z=F)IIb (Z=H)In the formulae IIIa and IIIb, Nu is a conventional nucleophilic leaving group such as halogen, e.g. chlorine, bromine and iodine, or sulfonyloxy, e.g. methylsulfonyloxy, trifluoromethylsulfonyloxy, phenylsulfonyloxy and tolylsulfonyloxy." . .