Efficient, recoverable, copper-free Sonogashira reaction under FBS and thermomorphic mode

The solubility property of high fluorine content ligands allows us to report in this article the accomplishment under the fluorous biphasic system (FBS) the Pd-catalyzed Sonogashira reactions using novel recyclable Pd catalysts with fluorous-ponytails in the structure of 2,2′-bpy ligands that are only soluble in perfluorinated solvents at room temperature. Alternatively, without using any fluorous solvent but under the thermomorphic mode, the same Pd catalysts proceed with the Cu-free Sonogashira reactions homogeneously in DMF at 135 ± 5 °C, whereas the product mixtures after reaction remain in solution and the Pd catalysts precipitate from DMF at low temperature.

Being soluble in polar organic solvents at >120 °C but insoluble at room temperature, 2b–c were demonstrated to be recoverable in Pd-catalyzed Sonogashira reactions under FBS and thermomorphic mode.Figure optionsDownload as PowerPoint slide