Nano TiO2/SiO2: An efficient and reusable catalyst for the synthesis of oxindole derivatives

Nano tio2 supported on sio2 (nano tio2/sio2) as a solid lewis acid,was found to be an effective and reusable catalyst for the condensation reaction of indoles with isatins to afford the corresponding bis(indolyl)oxindoles at 50 °c under solvent-free conditions. the efficacy of the catalyst was also examined in the reaction of pyrrole and 3-methylindole with isatin. the catalyst has been recovered and its reusability confirmed in 5 runs. a plausible mechanism of condensation has also been suggested. © 2014 king saud university. production and hosting by elsevier b.v.