Abstract Alkynes and phenol diazonium salts undergo a Pd-catalyzed [2+ 2+ 1] cyclization reaction to spiro [4, 5] decatetraene-7-ones. This structure was confirmed for one example by X-ray single-crystal structure analysis. The reaction is believed to proceed through oxidative addition of the phenol diazonium cation to Pd 0, subsequent insertion of two alkynes, followed by irreversible spirocyclization.