Nitro-Spirocyclization of Biaryl Ynones with tert -Butyl Nitrite: Access to NO 2 -Substituted Spiro[5,5]trienones.

A metal/peroxide-free involved simple cascade 6- exo -trig spirocyclization of tert -butyl nitrite with biaryl ynones has been finished, which resulted in various NO 2 -modified spiro[5,5]trienones with good regioselectivity/yields. A variety of scaled-up experiments, reduction/epoxidation operations, and mechanistic studies were performed to verify the merits and spirocyclization process of this radical system. Finally, the structure of the spirocycles was confirmed by single-crystal X-ray diffraction.