Synthesis of silica nanoparticles via thermal decomposition of rice hulls and their catalytic applications in the preparations of isocoumarins

Silica nanoparticles were prepared by thermal decomposition of rice hulls. The results from XRD showed that the sample was silica NPs. The morphology and grain size of the silica NPs was investigated by SEM. As part of our ongoing program to develop efficient and robust methods for the preparation of heterocyclic compounds, we report here a simple, one-pot, three-component reaction between isocyanides, dibenzylamine and 2-formylbenzoic acid in the presence of silica NPs at ambient temperature after 5 h, leading to isocoumarin derivatives. Silica NPs were found to catalyze synthesis of isocoumarin derivatives from formylbenzoic acid, isocyanides and dibenzylamine in solvent-free conditions in high yields. We also have used silica gel powder instead of silica NPs in this reaction, but increasing of reaction times and decreasing of isocoumarin yields were observed. The use of just 0.3 g of silica NPs for 1 mmole of reactants is sufficient to push the reaction forward. Higher amounts of silica NPs (0.4 g) did not improve the result to a great extent.