Nitrative Spirocyclization Mediated by TEMPO: Synthesis of Nitrated Spirocycles from N-Arylpropiolamides, tert-Butyl Nitrite and Water

A new method for the nitrative spirocyclization of alkynes is described. This method involves the oxidative difunctionalization of alkynes initiated by a radical attack pathway using t-BuONO (tert-butyl nitrite) combined with water as the nitro source and TEMPO [(2,2,6,6-tetramethyl-piperidin-1-yl) oxyl] as the initiator, and it represents a new example of oxidative alkyne difunctionalization via the formation of C-N/C-C bonds for the assembly of nitroalkene unit-containing spirocycles.