Oxidative Cyclization of Aryl Ynones with NaNO2 for the Divergent Synthesis of NO2‐Containing Spiro[5.5]trienones, Indenones and Thioflavones

Abstract A K 2 S 2 O 8 ‐promoted nitration/spirocyclization of biaryl ynones using inexpensive NaNO 2 as nitro source has been described. This cascade reaction is triggered by nitration of alkyne and followed by 6‐exo‐trig spirocyclization, dearomatization, forming the NO 2 ‐containing spiro[5.5]trienones in 63–85% yields. The present reaction also provides a practical method for the synthesis of nitrated indenones and thioflavones with 58–85% yields. magnified image