The Building Of New Type Salen Ligands And It’s Application In Asymmetric Reaction

In the past decades, biomimetic catalysts attracted many chemists’ attention for its efficiently catalytic activity and excellently enantioselectivity in catalytic asymmatric reaction. Salen ligands occupied a important position in biomimetic catalysts, because Salen ligands were able to stabilize many different metals in various oxidation states, controlling the performance of metals in a large variety of useful catalytic transformations.The design and synthesis of a novel multifunctional ligands is always one of the most important topics in organometallic-based asymmetric catalysis. In this thesis, We synthesised a new type of chiral salen ligand which featured aromatic π-walls with multistereogenic centers, and studied these ligands’application in transition metal-catalyzed asymmetric catalysis reactions.Firstly, we have developed and reported a facile and practical methodology to successfully synthesize a new family of chiral Schiff base ligands derived from chiral binaphthol (BINOL).We investigated the reaction activity of the catalytic complex with cobalt in the asymmetric Henry reaction of aromatic aldehydes and nitromethane.. and achieved high yields (up to 99%) and excellent enantioselectivities (up to 98% ee). And more interestingly, it was supposed that either salan-Cu(Ⅱ) or salen-Co(Ⅲ) complex catalyzed Henry reaction was an ideal model reaction for providing direct evidence of noncovalent interaction due to the distinguishable ortho-substituted aromatic aldehydes from meta- or para- substituted benzaldehydes in terms of enantioselectivities and yields.Then on the basis of predecessors’ work, we found that Salen-Mn complex wasn’t a successful catalyst in the asymmetric cyanosililysition reaction of aldehydes and TMSCN. In order to investigate the special role of the two benzylic groups of the Salen. we synthesized a series of Salen-Mn complexes. As a result, the multistereogenic salen-Mn(Ⅲ) complex bearing aromatic pocket and two benzylic groups as helping hands was found to be efficient in the catalytic asymmetric cyanosilylation, in which the salen-Mn catalyst mimicked partially the functions of biocatalysts by reasonable utilization of steric and electronic properties of catalytic center to interact with substrate, and achieved high yields (up to 94%) and good enantioselectivities (up to 90% ee).