On the reactions of trialkyl(trifluorovinyl)silanes with isocyanates and isothiocyanates − Expected and surprising results

Conditions for the addition of trialkyl(trifluorovinyl)silanes to the carbonyl- and thiocarbonyl function of commercially available isocyanates and isothiocyanates in the presence of tetramethylammonium fluoride (TMAF) to give corresponding amides of 2,3,3-trifluoroacrylic and 2,3,3-trifluorothioacrylic acids have been elaborated. The behaviour of the synthesized amides towards fluoride ions was studied. The syntheses of the amides of 2,3,3,3-tetrafluoropropionic and 2,3,3,3-tetrafluorothiopropionic acids and some unexpected cyclic products with the β-lactam structure are described. The molecular structures of the c-hexyl amide of 2,3,3,3-tetrafluoropropionic acid and two isomers of β-lactams deriving from the reaction of the tert-butyl amide of 2,3,3-trifluoroacrylic acid with a fluoride source have been elucidated by XRD measurements.

A convenient synthetic pathway to amides of 2,3,3-trifluoro(thio)acrylic acids has been opened starting from trialkyl(trifluorovinyl)-silanes in the presence of fluoride ions and the respective iso(thio)cyanates. The reactivity of these amides towards fluoride ions was studied affording access to amides of 2,3,3,3-tetrafluoro(thio)propionic acids and some unexpected cyclic products with the β-lactam motif.Figure optionsDownload as PowerPoint slideHighlights
► Amides of 2,3,3-trifluoroacrylic and 2,3,3-trifluorothioacrylic acids were prepared by a one-pot procedure.
► The behaviour of the synthesized amides towards fluoride ions was studied.
► Amides of 2,3,3,3-tetrafluoropropionic and 2,3,3,3-tetrafluorothiopropionic acids and cyclic products with the β-lactam structure have been synthesized.