Asymmetric Rh(II)/Pd(0) Relay Catalysis: Synthesis of α‑Quaternary Chiral β‑Lactams through Enantioselective C–H Insertion/Diastereoselective Allylation of Diazoamides

A straightforward
route toward construction of α-quaternary
chiral β-lactam moiety via Rh­(II)/Pd(0)-catalyzed stereoselective
relay catalytic reaction is reported. This asymmetric dual relay catalysis
involves Rh­(II)-catalyzed enantioselective intramoluecular C–H
insertions of α-diazoamides, and sequential Pd(0)-catalyzed
diastereoselective intermolecular allylic alkylation. Under mild reaction
conditions, a broad range of α-quaternary allylated chiral β-lactams
have been synthesized in high yields (up to 99%) with excellent stereoselectivities
[up to diastereomeric ratio (dr) >99:1, up to 98% enantiomeric
excess
(ee)].