An easy and efficient protocol for the condensation reaction of isatin and <i>N</i>-substituted isatins with 1,2-diaminobenzene using low cost reusable clay catalyst
Abstract A green procedure was developed for the condensation of isatin and N-substituted isatins with 1,2-diaminobenzene by using reusable bentonite clay in EtOH/H2O solvent system, under microwave irradiation. This eco-friendly synthesis is characterized by high yields and short reaction times. The catalyst is easily recycled.
Refluxing dimethyl acetylenedicarboxylate (DMAD) or 1,2-dibenzoylacetylene with isatin-3-thiosemicarbazone or isatin-3-thiocarbohydrazone in methanol produced 3-substituted oxindoles in good yields. Reaction of equimolecular amounts of 5,6-diamino- urasil-solfate, trans-(1R,2R)-diaminocyclohexane, and 3,4-diamino-1,2,4-triazol-5-methyl hydrochlorid with isatin in ethanol (85%) afforded tetracyclic ring systems and ring-opened products in mild reaction conditions.