Pd-catalyzed [2+2+1] coupling of alkynes and arenes: Phenol diazonium salts as mechanistic trapdoors

摘要

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.