Visible-Light-Mediated Lewis Acid-Catalyzed Diradical Hydrogen Atom Transfer Reaction of Bicyclo[1.1.0]butanes

Nitrogen-containing heterocycles are essential to chemical and life sciences due to their diverse biological activities and functional versatility. However, in contrast to 3D bioisosteres of the benzene ring, analogous bioisosteres of nitrogen-containing heterocycles remain quite limited despite several recent developments, where pyridone, a "central bioisostere" for amide, phenyl, pyridine, pyridine N-oxides, and phenols, should be especially highlighted. Herein, we report an effective route for the divergent synthesis of 3-azabicyclo[3.1.1]heptan-2-ones as promising pyridone bioisosteres from bicycle-butanes (BCBs) via Ir/Lewis acid-catalyzed programmed hydrogen atom transfer of C(sp³)-H bonds and subsequent cyclization under visible light. Mechanistic evidence and DFT calculations suggest that the acid catalyst was crucial for the success via isomerizing BCBs and modulating the reactivity of the diradical intermediates to unlock a challenging carbon-to-carbon DHAT and subsequent cyclization that allows the functionalization of various C(sp³)-H bonds, accessing underexplored 3-azabicyclo[3.1.1]heptan-2-ones. Lastly, further transformations and applications in synthetic chemistry and bioactive molecules reveal their promising potential in organic synthesis, materials science, and pharmaceuticals.