Enantioselective Aziridination of Enals

Significance

An organocatalytic enantioselective aziridination of α,β-unsaturated aldehydes 1 is described. The two-step reaction between α,β-unsaturated aldehydes 1 and acylated hydroxycarbamates 2 is efficiently catalyzed by chiral pyrrolidine derivative 4 to form 2-formylaziridines 3. In the course of the reaction the catalyst presumably activates the α,β-unsaturated aldehyde 1 via formation of a chiral iminium intermediate. Subsequent conjugate attack on the β-carbon by hydroxycarbamate 2 and a nucleophilic 3-exo-tet attack of the formed enamine on the electrophilc nitrogen leads to 2-formylaziridine 3. In addition, the authors have shown the one-step conversion of products 3 into the corresponding β-amino acid esters.