Lithiated bisoxazolines, enantioselective

Addition of an allylic zinc reagent to cyclic aldimines has been reported129. Lithiated bisoxazoline 61 and allylzinc reagent form the reactive species, which adds to a cyclic aldimine enantioselectively with up to 97.5% (equation 29)129. 

The enantioselective variant employs a bisoxazoline ligand (39) which coordinates the lithium in a similar fashion to other known asymmetric lithiation protocols (Eq. 13) [18],... 

More recently, bisoxazolines were studied as ligands in [2,3]-Wittig rearrangements (up to 89% ee) [46] these ligands were also effective in a catalytic maimer [47]. Bisoxazoline 30 provides remarkably high enantioselectivity in the benzyhc lithiation-electrophile trapping reactions of benzyl methyl ether, iso-chroman and phthalan (up to 97% ee) (e.g.,Scheme 15) [48]. 

A number of bases can be utilized in the [2,3]-Wittig reaction. These include t-butyllithium, which in conjunction with a chiral bisoxazoline system 17, has been used to effect an enantioselective [2,3]-Wittig rearrangement of allyl ether 14 via an asymmetric lithiation. ... 

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