Quinine-catalyzed asymmetric domino Michael-cyclization reaction for the synthesis of spirocyclic oxindoles bearing two spiro quaternary centers and three consecutive stereocenters.

摘要

An efficient organocatalytic diastereo- and enantioselective method for the construction of spirocyclic oxindole derivatives bearing two Spiro quaternary centers 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 proceeded smoothly under mild reaction conditions for giving two classes of spirocyclic oxindole compounds in high to excellent yields with moderate to good diastereoselectivities and enantioselectivities. A plausible dual activation working model was tentatively proposed to account for the stereochemistry of the domino Michael/cyclization process. (C) 2014 Published by Elsevier Ltd.