Construction of pyrazolo[5,1-a]isoindol-8(3aH)-one derivatives via phosphine-catalyzed cyclization of electron-deficient alkynes and N-amino substituted phthalimide

A novel method for the synthesis of diversely functionalized pyrazolo[5,1-a]isoindol-8(3aH)-ones is developed via phosphine-catalyzed tandem Michael addition/intramolecular Morita–Baylis–Hillman reaction of electron-deficient alkynes and N-amino substituted phthalimide. This cyclization is operationally simple under metal-free reaction conditions.