Synthesis Of Chiral Phosphorous Ligands And Their Applications In Asymmetric Synthesis

Three chiral phosphorus ligands were prepared using anisole as the startingat material.Their applications in the asymmetric hydroformylation and asymmetric conjug ed addition of diethylzinc to enones were investigated. In asymmetric conjugated reaction the influence of the reaction solvent, the ratio of metal to ligand on the reaction was studied in detail. All the three ligands were found to show good catalytic activity and regioselectivity, but the enantioselectivity of catalysts was rather low. Based on an examination of the structure of the ligands, the lack of a chiral environment around the diphenylphosphine group was suggested to be the major factor resulted in low enantioselectivity of catalyst. If a chiral element was introduced to the diphenylphosphine part, some improvements in the enantioselectivity would be expected. We are developing more efficient ligands along this way. In addition, ioding was found to be an efficient catalyst for the imino Diels-Alder reaction of N-arylimine and enol ethers and the reaction provided tertrahydroqinolines in good yields. One pot synthesis of tetrahydroqinolines from aldehyde, aniline and enol ethers was also achieved using iodine as the catalyst. The chemical yield of the"one pot"reaction was comparable with that obtained using preformed N-arylimine. The new method had the advantages such as facile experimental procedure, low price of iodine, good yield and ease of work-up.