Green synthesis of spiro[indoline-3,90-xanthene]trione derivatives using sulfonic acid functionalized SBA-15 as a new nanoporous acid catalyst

A simple and efficient method for the synthesis of spiro[indoline-3,90-xanthene]trione derivativeshas been achieved through the condensation reaction of isatins and two moles of dimedone or1,3-cyclohexanedione, under solvent-free conditions, in the presence of sba-15-prso3h as an efficientheterogeneous nano solid acid catalyst. the features of this procedure are short reaction times, good yields,solvent-free reaction conditions, and simple workup. the absence of solvent allows avoiding the use oftoxic organic solvents, which makes this reaction safe and environmentally friendly. furthermore, the useof sba-15-prso3h with a pore size of 6 nm has the advantage of being a nano-reactor in whose nanoporesthe reaction proceeds easily.