Highly efficient enantioselective synthesis of bispiro[benzofuran-oxindole-pyrrolidine]s through organocatalytic cycloaddition†
Abstract
A series of compounds featuring novel bispiro[benzofuran-oxindole-pyrrolidine] moieties have been achieved through a thiourea-catalyzed 1,3-dipolar cycloaddition reaction. The Michael/Mannich reaction of N-2,2,2-trifluoroethylisatin ketimines with aurones furnished the cycloadducts in excellent yields with excellent stereoselectivities.