Abstract: 4-Fluorocyclohexa-2, 5-dienone derivatives were obtained in high yield by reaction of para substituted phenols with 1-fluoro-4-chloromethyl-1, 4-diazoniabicyclo [2.2. 2] octane bis (tetrafluoro-borate)(1a, SelectfluorTM F-TEDA-BF4) or its 4-hydroxy analogue (1b, AccufluorTM NFTh) in acetonitrile. Estrogen steroids were readily converted to 10b-fluoro-1, 4-estradiene-3-one derivatives in high yields. Key words: fluorinated ketones, ...