Cyclodehydration and Baker-Venkataraman Rearrangement Methodologies for the Preparation of Fluorinated 4H-Chromones

Abstract

Trifluoromethylated and ring-fluorinated 4H-chromones have been prepared via cyclodehydration and via the baker-venkataraman rearrangement. The cyclodehydration of 4,4,4-trifluoro-1-(1-naphthol-2-yl)-1,3-butanedione was performed under a variety of base promoted and acid catalyzed processes enroute to 2-trifluoromethyl-β-naphthochromone. Using microwave irradiative, sonication and conventional processes, selected o-hydroxyaromatic ketones underwent single-pot, based promoted baker-venkataraman rearrangements with trifluoroacetic anhydride to give trifluoromethylated 4H-chromones in yields ranging from 50-82%. Microwave irradiation conditions allowed for yields ranging from 50-80%, which compare favorably to yields achieved via conventional methods (60-82%) as well as reducing reaction times by 55% compared to conventional refluxing conditions.