An N-heterocyclic carbene/Lewis acid strategy for the stereoselective synthesis of spirooxindole lactones.

ABSTRACT

A cooperative catalysis approach for the enantioselective formal [3+2] addition of α,ß-unsaturated aldehydes to isatins has been developed. Homoenolate annulations of ß-aryl enals catalyzed by an N-heterocyclic carbene (NHC) require the addition of lithium chloride for high levels of enantioselectivity. This NHC-catalyzed annulation has been used for the total synthesis of maremycin B.