Enantioselective Decarboxylative Mannich Reactions of α,β-Unsaturated β′-Ketoacids and Isatin Imines: Application in the Synthesis of Spiro[indoline-3,2′-piperidine]-2,4′-diones

Organocatalytic, enantioselective decarboxylative Mannich reactions of α,β-unsaturated β′-ketoacids and isatin N-Boc imines, to give the corresponding 3-carbamoyl-2-oxindole derivatives, were developed. Subsequent N-deprotection and diastereoselective, intramolecular, aza-Michael reaction of the free amine provides previously unreported spiro[indoline-3,2′-piperidine]-2,4′-diones.