Catalytic Enantioselective Desymmetrization of meso-N-Acylaziridines with TMSCN

A catalytic enantioselective desymmetrization of meso-N-p-nitrobenzoylaziridines with TMSCN was developed using a chiral gadolinium catalyst generated from Gd(OiPr)3 and d-glucose-derived ligand 1. In this reaction, the addition of a catalytic amount of trifluoroacetic acid (TFA) improved enantioselectivity. High enantioselectivity was obtained from a range of meso-aziridines at 0-60 degrees C. The product could be easily transformed into beta-amino acids. Thus, the developed catalytic enantioselective desymmetrization reaction allowed for efficient catalytic synthesis of chiral cyclic beta-amino acids. The incorporation of TFA into the catalyst complex was observed using ESI-MS. Generation of this new complex might be the origin of the improved enantioselectivity.