Diazo‐ and Transition‐Metal‐Free CH Insertion: A Direct Synthesis of β‐Lactams

Carbene intermediates are very useful species for a range of reactions including C?H insertions and cycloadditions. They are most commonly generated by metal‐catalyzed release of nitrogen gas from diazo precursors. Herein, we present a novel C?H insertion of simple β‐ketoamide substrates, through reaction with (diacetoxyiodo)benzene (DIB) in the presence of a base. This unprecedented transformation bypasses the use of either diazo precursors or metal catalysts and directly delivers β‐lactam products by an iodonium ylide, in a single step under mild conditions. Mechanistic studies support the intermediacy of a free singlet carbene of unique reactivity and selectivity.