Asymmetric Construction of 3,3-Disubstituted Oxindoles Bearing Vicinal Quaternary–Tertiary Carbon Stereocenters Catalyzed by a Chiral-at-Rhodium Complex

A highly
diastereo- and enantioselective synthesis of 3,3-disubstituted
oxindoles bearing vicinal quaternary–tertiary carbon centers
is enabled by a chiral-at-rhodium Lewis acid catalyst starting from
isatin N-protected ketimines and 2-acyl imidazoles.
The excellent results with 93–99% yields, diastereoselectivities
of 43:1 to >200:1, and high enantioselectivities of 98.4 to >99%
confirm
the potential of bis-cyclometalated rhodium catalysts for the development
of effective asymmetric transformations.