Recoverable Palladium-Catalyzed Carbon-Carbon Bond Forming Reactions under Thermomorphic Mode: Stille and Suzuki-Miyaura Reactions.

The reaction of [PdCl(CHCN)] and bis-4,4'-(RCHOCH)-2,2'-bpy (), where R = -CF (), -CF (), -CF () and -CF (), respectively, in the presence of dichloromethane (CHCl) resulted in the synthesis of Pd complex, [PdCl[4,4'-bis-(RCHOCH)-2,2'-bpy] (). The Pd-catalyzed Stille arylations of vinyl tributyltin with aryl halides were selected to demonstrate the feasibility of recycling usage with as the catalyst using NMP (N-methyl-2-pyrrolidone) as the solvent at 120-150 °C. Additionally, recycling and electronic effect studies of were also carried out for Suzuki-Miyaura reaction of phenylboronic acid derivatives, 4-X-CH-B(OH), (X = H or Ph) with aryl halide, 4-Y-CH-Z, (Y = CN, H or OCH; Z = I or Br) in dimethylformamide (DMF) at 135-150 °C. At the end of each cycle, the product mixtures were cooled to lower temperature (e.g., -10 °C), and then catalysts were recovered by decantation with Pd leaching less than 1%. The products were quantified by gas chromatography/mass spectrometry (GC/MS) analysis or by the isolated yield. The complex -catalyzed Stille reaction of aryl iodides with vinyl tributyltin have good recycling results for a total of 8 times, with a high yield within short period of time (1-3 h). Similarly, -catalyzed Suzuki-Miyaura reactions also have good recycling results. The electronic effect studies from substituents in both Stille and Suzuki-Miyaura coupling reactions showed that electron withdrawing groups speed up the reaction rate. To our knowledge, this is the first example of recoverable fluorous long-chained Pd-catalyzed Stille reactions under the thermomorphic mode.