A direct and efficient strategy for the oxidative spirocyclization of biaryl ynones has been developed, where nonsubstituted groups were on the para-position of the dearomatized aryl rings. This cascade reaction uses the stable and readily available AgSCF₃ as a trifluoromethylthio radical precursor and the reaction occurs smoothly in the presence of K₂S₂O₈ and TBHP via a 6-exo-trig radical cyclization, providing a variety of SCF₃-containing spiro[5,5]trienones in good yields.