1,6-Conjugate-Addition-Induced [2 + 1] Annulation of <i>para</i>-Quinone Methides and Pyrazolones: Synthesis of Bis-Spiro Compounds with Contiguous Quaternary Spiro-Centers

Abstract

A diastereoselective formal 1,6-conjugate-addition-mediated [2 + 1] annulation reaction using p-quinone methides and pyrazolones has been described. The corresponding bis-spiro[cyclohexadienone–cyclopropane–pyrazolone] compounds were obtained in very good yield under mild reaction conditions.