Construction of Spirooxindole-Fused Spiropyrazolones Containing Contiguous Three Stereogenic centres via [3+2] Annulation utilizing Ferrocene Derived Bifunctional Phosphine-Catalyst

A ferrocene-derived bifunctional phosphine-catalyzed enantioselective [3+2] annulation of γ-substituted allenoates with pyrazoloneyldiene oxindoles is investigated for the construct of spiro-cyclopentene-linked oxindole and pyrazolone compounds, which bearing three consecutive stereocenters and two vicinal spiroquaternary chiral centers, in good chemical yields (up to 95 %) with excellent regio-, diastereo- (dr >19:1) and enantioselectivities (up to 98% ee).