Reactions of 1,1,2,2-tetrafluoroethyl-N,N-dimethylamine with linear and cyclic 1,3-diketones

Ketones are known to be unreactive toward α-fluoroamines such as Ishikawa's Reagent or 1,1,2,2-tetrafluoroethyl-N,N-dimethylamine (TFEDMA). On the other hand, 1,3-diketones were found to undergo fluorination with TFEDMA. In the case of linear 1,3-diketones, the proposed mechanism involves the formation of β-fluoro-α,β-unsaturated ketones followed by the addition of HF to selectively give the product β,β-difluoroketone. Interestingly, when the 1,3-diketone is cyclic (i.e. 1,3-cyclohexadione) the outcome of the reaction is different and results in the formation of a product with a 2,2-difluoroacetyl group on the 2-carbon.

Graphical abstractTFEDMA reacts with linear 1,3-diketones to selectively form β,β-difluoroketone products. TFEDMA also reacts with cyclic 1,3-diketones, but instead of fluorination, it reacts to give a product of acylation at the 2-position. For the cyclic diketone system, Ishikawa's Reagent behaves in a similar manner to TFEDMA.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights• TFEDMA can react with linear 1,3-diketones to selectively form β,β-difluoroketone product. • TFEDMA reacts with cyclic 1,3-diketones to give acylation at the 2-position. • Possible mechanisms are proposed.