Perfluoro-(2,2,6,6-tetramethyl-N-fluoropiperidine) (1) has been synthesized via direct fluorination (with F 2 -N 2 ) of caesium perfluoro-(2,2,6,6-tetramethylpiperidide) (10) in cold (-30 o C) acetonitrile, the piperidide (10) being produced via treatment of perfluoro-(2,6-dimethyl-1-azacyclohexene) (6) with an excess of (trifluoromethyl)trimethylsilane in the presence of caesium fluoride. Methylation of perfluoro-(2,6-dimethyl-1-azacyclohexene) (6) with methyl-lithium in diethyl ether, followed by the addition of aqueous sulphuric acid provided 3,3,4,4,5,5-hexafluoro-2(a),6(a)-dimethyl-2(e),6(e)-bis(trifluoromethyl)pipe ridine (13); fluorination (with F 2 -N 2 ) of 13 in trichlorofluoromethane containing anhydrous potassium fluoride provided 3,3,4,4,5,5-hexafluoro-2(a),6(a)-dimethyl-2(e),6(e)-bis(trifluoromethyl)-N-f luoropiperidine (14), the stereochemistry of which was established by X-ray crystallographic analysis. Site-specific electrophilic fluorination of the sodium enolate of ethyl 2-oxocyclopentanecarboxylate (15) proceeded more efficiently with the new NF reagents 1 and 14 than with their analogues perfluoro-N-fluoropiperidine and perfluoro-(2,6-dimethyl-N-fluoropiperidine), which contain α-fluorine substituents.