Base-Promoted Oxidative C–H Functionalization of α‑Amino Carbonyl Compounds under Mild Metal-Free Conditions: Using Molecular Oxygen as the Oxidant

A base-mediated aerobic oxidation
of the C–H bond adjacent
to the N-atom of a secondary amine to form an imine intermediate under
mild metal-free basic conditions has been developed. Accordingly,
this new strategy has been successfully applied to the synthesis of
various di-, tri-, and tetra-substituted α-amino­cyclo­pentenones
through a tandem aerobic oxidative [4 + 1] carbocyclization reaction
of N-aryl α′-amino-α,β-unsaturated
ketones as C4 1,4-dielectrophiles with active methylenes,
including ethyl isocyanoacetate, nitroalkanes, and ethyl cyanoacetate,
as C1 components.