Reaction of Isatins with Active Methylene Compounds on Neutral Alumina: Formation of Knoevenagel Condensates and Other Interesting Products

Isatin and its N-methyl and 5-nitro derivatives underwent smooth reaction with a variety of acyclic and cyclic active methylene compounds on neutral alumina at rt to efficiently furnish Knoevenagel condensates in the majority of the cases and tandem Knoevenagel condensation-Michael addition products including spiro compounds in two cases.