Construction of spirooxindole-fused spiropyrazolones containing contiguous three stereogenic centres via [3 + 2] annulation utilizing a ferrocene derived bifunctional phosphine catalyst

Abstract

A ferrocene-derived bifunctional phosphine-catalyzed enantioselective [3 + 2] annulation of γ-substituted allenoates with pyrazoloneyldiene oxindoles is investigated for the construction of spiro-cyclopentene-linked oxindole and pyrazolone compounds, which bear 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).