Synthesis Of Chiral Phosphines And Application In Asymmetric Addition Reaction Of Chalcone

Chiral phosphines-borane adducts were synthesized from dichlorophenylphosphine using L-menthol as a chiral resolution reagent.The two configurations of phosphines-borane adducts exhibit different chemical shifts in the ¹H NMR spectrum,and can be separated by recrystallization.The single enantiomer is methylated with MeLi to afford single configuration of chiral methylated phosphines-borane adduct with retention of configuration,and its molecular geometry is characterized by X-ray crystal structure analysis.Chiral phosphines are transformed into the corresponding phosphine oxides with configuration retention using tert-butyl hydroperoxide?TBHP?as oxidant in certain conditions.In addition,the resultant chiral phosphine ligands were evaluated in the asymmetric addition of Et₂Zn and chalcone,affording the corresponding compound with 76%yield,but a low enantioselectivity of 9%ee.