Site-Selective and Chemoselective C–H Functionalization for the Synthesis of Spiroaminals via a Silver-Catalyzed Nitrene Transfer Reaction

Although
intense research over the last 2 decades revealed a diverse
proficiency of nitrene species in chemistry disciplines, control of
the selectivity in the reaction manifold has remained a challenge.
We report herein the development of site-selective and chemoselective
C–H functionalization involving nitrene species to synthesize
densely functionalized spiroaminals. A rhodium catalyst generally
used in nitrene chemistry gave amide C–N insertion products
and/or the corresponding ketones, whereas a silver catalyst with an
achiral bisoxazoline (BOX) ligand provided C–H insertion products.
Mechanistic analysis based on integrated experimental and computational
studies indicated that the nitrene transfer occurred through an asynchronous
concerted process involving triplet spin-correlated radical pairs,
affording the corresponding stereodefined spiromolecules.