Molecular sieve mediated sequential Knoevenagel condensation/decarboxylative Michael addition reaction: efficient and mild conditions for the synthesis of 3,3-disubstituted oxindoles with an all carbon quaternary center

A one-pot, molecular sieve mediated sequential Knoevenagel condensation/decarboxylative Michael addition reaction has been developed. We discovered that the molecular sieves not only promoted the Knoevenagel condensation of isatins and malononitrile to generate isatylidene malononitriles, but also promoted the later decarboxylative Michael addition reactions of β-ketoacids and malonic acid half thioesters (MAHTs) with isatylidene malononitriles. This protocol provides a mild and efficient method for the preparation of 3,3-disubstituted oxindoles with an all carbon quaternary center in high yields.