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

A K2S2O8-promoted nitration/spirocyclization of biaryl ynones using inexpensive NaNO2 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 NO2-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.

Automated summary

A K2S2O8-promoted nitration/spirocyclization reaction of biaryl ynones using inexpensive NaNO2 as the nitro source has been reported. This cascade reaction involves the nitration of alkynes followed by 6-exo-trig spirocyclization and dearomatization, resulting in the formation of NO2-containing spiro[5.5]trienones in yields of 63-85%. Furthermore, the reaction provides a practical method for the synthesis of nitrated indenones and thioflavones with yields of 58-85%.