SCHEDULED MAINTENANCE
Magnetically separable Fe3O4–SO3H nanoparticles as an efficient solid acid support for the facile synthesis of two types of spiroindole fused dihydropyridine derivatives under solvent free conditions†
Abstract
Magnetically separable Fe3O4–SO3H nanoparticles are found to act as an efficient solid supported acid catalyst for the facile synthesis of two types of spiroindole fused dihydropyridine derivatives such as spiro[indolo-3,10′-indeno[1,2-b]quinolin]-2,4,11′-triones and indenoquinoline-spirooxindoles under solvent-free conditions. Depending upon the nature of N-substitutions of the starting isatins (N–H or N–R/Ar) two different types of products are formed through three component one-pot condensation reactions. Operational simplicity, reduced reaction time, lower reaction temperature, elimination of solvents, high yields of the products, easy separation of Fe3O4–SO3H nanoparticles by means of an external magnetic bar and recyclability of Fe3O4–SO3H nanoparticles make the present method economical, green and sustainable.
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