In recent years, the significance of spirocyclic motifs in drug discovery has increased,
owing to their unique ability to engage biological targets. We present the first example
of PIFA-mediated dearomative spirocyclization of phenol-tethered pyrazoles, highlighting
intramolecular trapping by the pyrazole moiety. This method efficiently affords a
variety of spirocyclohexadienone-pyrazolo[3,4-b]piperidinones with yields of up to 82%. Mechanistic studies reveal that the dearomatization
process involves a cationic intermediate.
Key words
phenols - dearomatization - spirocyclohexadienone - PIFA - pyrazole
