Synthesis of chiral spiro-cyclopentene/cyclopentadiene-oxindoles through an asymmetric [3 + 2] cycloaddition of isatin-derived MBH carbonates and β,γ-unsaturated α-keto esters

Abstract

A highly stereoselective [3 + 2] cycloaddition for constructing the chiral spiro-cyclopentene/cyclopentadiene-oxindole skeletons is developed. Under the mild reaction conditions, the straightforward cyclization of isatin-derived MBH carbonates and β,γ-unsaturated α-keto esters involving a chiral tertiary amine catalyst provides the corresponding spirooxindole derivatives with an extraordinary level of diastereo- and enantioselectivities. Further synthetic utility of this protocol is demonstrated by the gram-scale experiment and functional transformation of the synthetic compound into other structurally diverse spirooxindole.