Asymmetric lithiation of an allyl carbamate induced by a complexing remotechiral substituent

The stereohomogeneous (delta-arenesulfonyloxazolidine)substituted allyl car bamate 7, after lithiation under several conditions, forms the lithium comp ound 8 with high diastereoselectivity (dr > 97: 3). 8 is trapped with a num ber of electrophiles to give the diastereo- and enantiomerically enriched a lpha- and gamma-substitution products. Evidence is contributed for: i) 8 is configurationally unstable and the relative configuration is thermodynamic ally controlled by chelation with the chiral auxiliary, ii) substitution in the alpha-position proceeds with inversion of the configuration.