Synthesis of Chiral Aziridines from Imines and Diazoacetamides

Significance

Reported is the synthesis of trans-aziridines 3 and 4 via the addition of carbenes generated from secondary diazoacetamides 2 to imines 1. The same group has previously shown that carbenes derived from diazoesters add to imines 1 to give the cis-aziridines exclusively (see Review). The current work reports the use of the same catalyst yet demonstrates a complete switch to the trans-aziridine product simply by changing the carbene precursor. The reaction exhibits broad scope with high yields and excellent asymmetric induction observed for a wide range of substrates of varying electronic and steric demands. A key feature of this method is that both aryl and alkyl imines may be used. Conversion of the carboxamide into the ester (Boc₂O, DMAP; then NaOEt, EtOH, 96% yield) was shown in one case.