A new asymmetric organocatalytic synthesis of spirocyclopropaneoxindoles has been developed. The method is based on the Michael addition of N-Boc-protected 3-chlorooxindole to unsaturated 1,4-dicarbonyl compounds, affording trans-substituted spirocyclopropaneoxindolederivatives in high diastereo- and enantioselectivity.
A new enantioselective cyclopropanation of 3‐alkenyl‐oxindoles with sulfoxonium ylides was realized by using a chiral N,N′‐dioxide/Mg(OTf)2 complex as the catalyst. Various chiral spiro‐cyclopropyl oxindoles containing two or three continuous chiral carbon centres were obtained in high yields (up to 99%) with good dr (up to 97:3 dr) and high ee values (up to 94% ee).