Synthesis and Reactivity of Fluorinated Cyclic Ketones: Initial Findings

Abstract Using cyclic ketone scaffolds, several novel trifluoroacetylated 1,3-diketones and selectively -fluorinated αketones have been prepared in yields ranging from 20-77% using the Claisen condensation and electrophilic fluorinationby the Selectfluor ® reagent, respectively. We report tendencies in the difluorinated and trifluoroacetylated products to form hydrates as well as an unusual range of substrate reactivity toward the Selectfluor ® reagent. In general, initial spectroscopic studies suggest that cyclic 2-trifluoroacetylated-1,3-diketones undergo rapid hydration resulting in an equilibrium mixture favoring the diketo hydrate over the keto-enol hydrate. Fluorination of ketone species by Selectfluor ® was found to be governed by a combination of steric and electronic effects. Plausible mechanisms for both mono- and difluorination, involving a keto-enol or enolic tautomer, are proposed. Keywords 2-trifluoroacetyl-1,3-diketone, Selectfluor ® , tautomerism, 19 F NMR 1. Introduction