Synthesis of 2,3-Dihydro-4(1 H )-pyrimidinones through Copper-Catalyzed Skeletal Rearrangement of Spirocyclic Aminimides

Aminimides are known to act as nitrene equivalents through N–N bond cleavage in Curtius-type rearrangements, but their use in other nitrene-type transformations is largely unexplored. Herein, we report a copper-catalyzed, atom-economical synthesis of 2,3-dihydro-4(1H)-pyrimidinones from alkynyl hydrazides. Control experiments suggest that the transformation proceeds via cyclization to form spirocyclic aminimides, followed by N–N bond cleavage and intramolecular C–H insertion.