Synthesis Of Symmetrical Biaryls By Palladium-Catalyzed Coupling Reactions

The palladium-catalyzed Ullmann-type and one-pot borylation/Suzuki coupling reactions were studied in this thesis as follows:I. DAB-Cy as ligand for palladium-catalyzed Ullmann-type coupling reactionIn order to optimize the reaction conditions, the homocoupling of p-bromoanisole as substrate was examined. The results showed that DMF was the best solvent, the ratio of catalyst PdCl₂(CH₃CN)₂ with ligand DAB-Cy was 3:4.5, 0.5 equiv. of n-Bu₄NBr and hydroquinone as additives; Then the scope and limitation of this method were examined. The results indicated that the homocoupling reaction of aryl or heterocyclic bromides and iodide could be smoothly carried out to afford moderate to good yields. II. Triphenylphosphine adduct of cyclopalladated ferrocenylimine catalyzed one-pot borylation/Suzuki coupling reactionThe optimalized reaction conditions were found that aryl halide and 0.5 equiv. of bis(pinacolato)diboron were carried out in DMF at 100℃under N₂ with the loading of 1 mol % catalyst, 1 mol % PPh₃ and 5 equiv. K₃PO₄. Then the scope and limitation of this method were examined. The results indicated that the homocoupling reaction of aryl or heterocyclic bromides and iodide could be smoothly carried out to afford moderate to good yields. Even at a catalytic loading as low as 0.1 mol %, the product yield of iodide benzene was still as high as 94%.