Stereoselective Synthesis of β-Lactams by Oxidative Coupling of Dianions of Acyclic Tertiary Amides

Article abstract of DOI:10.1021/jo00032a047

Tertiary amides RCH2CON(R')CH2Z, where Z is an electron-withdrawing group, were converted into dianions by treatment with 2 equiv of n-butyllithium or tert-butyllithium, and the dianions were oxidized with N-iodoosuccinimide (NIS) or a Cu(II) carboxylate to form β-lactams stereoselectively.The stereochemistry of β-lactam formation depends on the oxidant; NIS is cis-selective, whereas Cu(II) is nonselective or slightly trans-selective.A high degree of asymmetric induction in the formation of β-lactams was achieved by using (R)-1-phenylethylamines a chiral auxiliary.This asymmetric ring closure was applied to the preparation of cis-β-lactam 31, an intermediate for the synthesis of the monobactam antibiotic carumonam.