Synthesis Of Chiral Ligands Based On Ugi’s Amine And α-Phenylethylamine And Their Applications In Asymmetric Catalysis

Asymmetric catalysis represents an effective method in the preparation of chiralcompounds. Significant progress has been made in many asymmetric catalysisreactions by using transition metal catalysts ligated by chiral ligands. Starting withreadily available Ugi’s amine or α-phenylethylamine, a new family of chiralferrocenyl P,S-ligands incorporating an a heterocyclic group at the α-ferrocenylmethylposition and a series of chiral1,4-amino alcohols ligands have been prepared. Thecatalytic performance of these chiral ligands in asymmetric catalysis was investigatedrespectively, giving excellent results in terms of conversions and enantioselectivities.Furthermore, some disciplines about structure-activity relationship of ligands are putforward, advancing further design and synthesis of novel effective chiral ligands.Chiral ferrocenyl ligand （Rc,SFc）-PPFA was obtained by treatment of Ugi’s aminewith n-BuLi and then orthophosphinated with chlorodiphenylphosphine. A new familyof chiral ferrocenyl P,S-ligands (S_c,S_Fc)-2a-f have been prepared via a Friedel-Craftsalkylation reaction of （Rc,SFc）-PPFA with a variety of2-indole thioethers. These newlydeveloped ferrocenyl P,S-ligands proved to be efficient in the Ag（I）-catalyzedasymmetric [3+2] cycloaddition of azomethine ylides, giving cycloadducts with highdiastereo-selectivities （endo） and enantioselectivities （up to99%ee）. Moreover, theresults disclosed that electronic properties and steric size of the substituents on thethio group significantly affected the enantioselectivity in asymmetric [3+2]cycloaddition reaction.A series of chiral1,4-amino alcohols ligands have been prepared from cheap andreadily available （S）-1-phenylethylamine through a one-step transformation with avariety of carbonyl compounds. The ability of these newly developed amino alcoholsligands was evaluated in the Ru（II）-catalyzed asymmetric transfer hydrogenation ofaromatic alkyl ketones, providing chiral secondary alcohols with good to excellentconversions （71-100%） and moderate to good enantioselectivities （67-95%ee）. Theresults also showed that the structures of these amino alcohols have a significantinfluence on the conversions and enantioselectivities. Less sterically around hydrooxygroup seems to be more favorable for achieving high enantioselectivity.