In the presence of molecular sieve (MS) 4 Å in DMF, a catalyst-free aldol condensation of a variety of aromatic and aliphatic ketones with isatins under mild reaction conditions has been developed. This approach may provide access to a wide range of 3-substituted-3-hydroxyindolin-2-ones in good to excellent yields.
Bovine trypsin displays a promiscuous activity to catalyze aldol reactions between isatins and ketones for easy access to 3-hydroxyindolin-2-ones. Detailed optimizations on the reaction conditions afforded the products with good yields, this system, which was compatible with various isatins. However, gradually enlarging the structure of ketones led to a significant decrease in yields. Molecular simulations