HFIP-Assisted Denitrogenative Radical Fragmentation Pathway of Areneazo-2-(2-nitro)propanes: Cross-Coupling of Aryl Radicals with Alkynes and Coupling Reagents

The HFIP-assisted denitrogenative radical fragmentation
of areneazo-2-(2-nitro)propanes,
a safer alternative to diazonium salts, generated dinitrogen, nitrogen
monoxide, acetone, and aryl radicals. These in situ generated aryl radicals participated in [4 + 2] benzannulations
to form phenanthrenes and in diverse cross-coupling reactions, including
Sandmeyer-type C–Br/C–Bpin/C–S/C–Se/C–P
and C–C bond formations. TEMPO-trapping experiments confirmed
their transient nature, enabling versatile approaches to radical-mediated
C–C and C–X bond construction under mild and practical
conditions.