1,3-dipolar cycloaddition reactions of azomethine ylides on enantiomerically pure (E)-γ-alkoxy-α,β-unsaturated esters.

Enantiomerically pure (E)-γ-alkoxy-α,β-unsaturated esters were reacted with azomethine ylides obtained from glycine imines in the presence of LiBr and diazabicycloundecene (DBU), to afford tetrasubstituted pyrrolidines with complete regiocontrol and fair to excellent diastereoselectivity (only two diastereoisomers formed in up to 96: 4 diastereoisomeric ratio). The results are compared with those of other 1,3-dipolar cycloadditions, and the origin of stereocontrol is discussed.