Quinine-catalyzed asymmetric domino Michael-cyclization reaction for the synthesis of spirocyclic oxindoles bearing two spiro quaternary centers and three consecutive stereocenters
An efficient organocatalytic diastereo- and enantioselective method for the construction of spirocyclic oxindole derivatives bearing twospiroquaternarycenters and three consecutive stereocenters via a domino Michael/cyclization process has been developed. Using commercially available quinine as catalyst, the reactions of 3-isothiocyanato oxindoles with unsaturated pyrazolones and unsaturated isoxazolones