Neutral/Ionic Phosphines And Their Application To Pd-catalyzed Alkoxycarbonylation

Transition metal catalyzed carbonylation with CO as the C1 resource is significantly important in organic synthesis, in which the palladium-catalyzed alkoxycarbonylation of aromatic halides and alkyne are the attractive approaches for the production of carboxylic esters. Hence, the development the highly efficient Pd-catalysts and the fulfillment of the recovery and recyclability of the homogeneous catalysts are always the hot topics in this area.In this thesis, a series of neutral and ionic biphosphines with different electronic and steric effects were synthesized and fully characterized in order to develop the corresponding palladium complexes, which were applied as the catalysts for the alkoxycarbonylation. It was found that, the electronic and steric effects of the biphosphines dramatically influenced the catalytic performance of the palladium catalysts. For alkoxycarbonylation of aryl iodides with alcohols, when the room temperature ionic liquid was used as a solvent, the dissolved bidentate phosphine ligand and the palladium catalyst could be recycled. In alkoxycarbonylation of phenylacetylene with methanol, the commercial bidentate phosphine ligand of dppf and its derivative (dppf-A) both exhibited the promoting effect on the catalytic performance of palladium-complex. However, dppf-A which was featured with a mono-phosphine after the stoichiometric quaternization of one-phosphine fragment in dppf corresponded to the high selectivity to the branched product, whereas dppf to the high selectivity to the linear product. In addition, the catalytic performance of the palladium catalysts was reasonably correlated to the structure and composition of the dppf-A for the studied alkoxycarbonylations.