New chiral amine ligands for enantioselective synthesis of certain (S)- and (R)-monobactams

Two new tridentate chiral amine ligands I and II mediated the condensation reaction of lithium ester enolate III with benzaldehyde p-​anisidineimine IV providing selectively the required (S)​- or (R)​-​monobactam V.  It is also noticed that the coexistence of III and chiral lithium amides that formed -​in situ- from I,​II is an important factor for the enhancement of the reactivity and enantioselectivity of III.