Asymmetric Synthesis And Application Of Chiral Spirosilabiindanes

Transition metal involved asymmetric catalysis continues as a hot topic in the field of organic synthetic chemistry,in which one of main tasks is the design and development of highly efficient and novel chiral ligand scaffolds.For instance,chiral spirocycle-based ligands have been widely used in asymmetric catalysis in light of their constrained structure.Among those spirocyclic scaffolds,spirobiindane,one of the most representative chiral spirocyclic skeletons,has been seen as "previliged ligand skeleton" due to its generality and wide application in asymmetric catalysis.However,the synthesis and the modification of this carbon-centered spirocycles remain a big challenge.In this thesis,a class of silicon-centered spirocycle was designed and synthesized,and was further utilized for the development of novel chiral ligands.Employing 2.0 mol%of[Rh(1,5-hexdiene)Cl]2 as a catalyst and 4.0 mol%of(R,R)-Et-Duphos or(R)-QuinoxP as a ligand,spirosilabiindane derivatives were synthesized with high efficiency and stereoselectivity.The method features broad substrate scope,and is suitable for the synthesis of a variety of chiral spirosilabiindane derivatives in excellent yields(84-99%),along with high diastereoselectivities(dr=91:9->96:4)and enantioselectivities(ee=90-99%).This procedure could be scaled-up to>10 gram-scale with a lower catalyst loading(0.5 mol%)without the loss of catalytic efficiency and stereoselectivity.Using the aforementioned method,this thesis further studied the synthsis of optically pure 7,7'-dimethoxyspirosilabiindanes.Upon the demethylation under mild conditions,enantiomerically pure spirosilabiindane diols(SPSiOL)could be obtained in high yields.Starting from SPSiOLs,monodentated phosphoramidite ligands(SPSiPhos)could be prepared in one step.Later on,the potential of this new spirosilabiindane scaffold in asymmetric catalysis was preliminarily demonstrated by using developed monodentate phosphoramidite ligands(SPSiPhos)in a Rh-catalyzed hydrogenation and a Pd-catalyzed intramolecular carboamination reactions.