Facile synthesis of iron oxide NPs as magnetically recyclable catalysts for chemoselective synthesis of pyrazolo[3,4-b]pyridine-5-carbonitriles in aqueous medium under ultrasonic irradiation

Centre of Advanced Studies, Department of Chemistry, University of Rajasthan, Jaipur-302 004, Rajasthan, India E-mail : dranshudandia@yahoo.co.in Semiconductor and Polymer Science Laboratory, Department of Physics, University of Rajasthan, Jaipur-302 004, Rajasthan, India Manuscript received 25 January 2014, accepted 10 February 2014 A magnetically recoverable iron oxide nanocatalyst has been prepared at room temperature by a wet chemical technique. This catalyst was characterized by XRD, TEM and EDAX. The results show that the particles are mostly spherical in shape and have an average size of approximately 17 nm. These nanoparticles were exploited to study their catalytic activities towards the chemoselective synthesis of pyrazolo[3,4-b]pyridine derivatives. The method showed remarkable selectivity for pyrazolo[3,4-b]pyridines over dehydrogenated pyrazolopyridines, bis-pyrazolopyridines and pyrazolo[1,5-a]pyrimidine derivatives. The excellent conversions show that the catalyst has strong and sufficient acidic sites, which are responsible for its catalytic performance. After the reaction, the catalyst/product separation could be easily achieved with an external magnetic field, and more than 95% of the catalyst could usually be recovered. The catalyst was reused at least five times without any loss of its high catalytic activity