A new synthetic procedure for the preparation of perfluoroalkanesulfonyl fluorides utilizing liquid-phase direct fluorination with elemental fluorine has been developed. Direct fluorination of a partially fluorinated ester, which has alkanesulfonyl fluoride in the end, was synthesized from non-fluorinated counterparts and perfluorinated acid fluoride according to the PERFECT process, gave the desired perfluorinated product in moderate yield as well as by-products arising from C-S bond cleavage. The results of the direct fluorination of some model substrates suggest that the C-S bond cleavage occurred due to radical formation at the alpha-position rather than the beta-position. (C) 2004 Elsevier B.V. All rights reserved.