Synthesis of Bis Coumarinyl Methanes Using Fe3O4@SiO2@KIT-6 as an Efficient and Reusable Catalyst

Coumarin constitutes one of the major classes of naturally occurring compounds. In the well-known family of coumarin derivatives, dimeric coumarins (also called biscoumarins) occupy an interesting position. Although some types of these compounds could be isolated from plants and interest in its chemistry because of its usefulness as biologically active agents. It also represents the core structure of several molecules of pharmaceutical importance. Coumarin has been reported to serve as anti-cancer, anti-microbial, anti-inflammatory, anticoagulant agents. These pharmacological properties of coumarin arised our interest in synthesizing some coumarin derivatives.

Methods: Aldehydes, 4-hydroxycoumarin, H2O and Fe3O4@SiO2@KIT-6 were stirred at room temperature. After completion the reaction, we extracted the product with CHCl3/H2O. After completion of the reaction, the Fe3O4@SiO2@KIT-6 magnetic nanoparticles were easily separated from the reaction medium by a magnet (1.4 T), and the reaction mixture filtered off. Then, 5 mL distilled water was added into the beaker and the obtained precipitate was filtered off. Finally, the crude products were recrystallized by ethanol to give pure products. The identity and purity of the products were confirmed by IR, 1H NMR, 13C NMR and elemental analysis.

Results: As part of our going interest for the development of efficient and environmentally friendly procedures for the synthesis of heterocyclic and pharmaceutical compounds, an efficient, facile and solvent free procedure was introduced for the synthesis of bis coumarinylmethane by the reaction of one equivalent of synthesized aldehyde and two equivalent of 4-hydroxycoumarin using Fe3O4@SiO2@KIT-6. Although, synthesis of bis coumarins using ionic liquids was reported, However, most of these reported methods suffer from environmental pollution, expensive reagents or catalysts, long reaction time, severe conditions, unsatisfactory yields and complicated operations. In order to make this reaction simple and green, herein, we used Fe3O4@SiO2@KIT-6 to synthesis of bis coumarinylmethanes by the one-pot reaction of 4-hydroxycoumarin and various benzaldehydes at room temperature.

Conclusion: In conclusion, we have investigated the Fe3O4@SiO2@KIT-6 as a mild and efficient catalyst for the synthesis of substituted bis coumarin compounds. The remarkable advantages offered by this method are: catalyst is inexpensive, non-toxic, easy handling and reusable, simple work-up procedure, short reaction time, high yields of product with better purity and green aspect by avoiding toxic catalyst and hazardous solvent. To the best of our knowledge this is the first report on synthesis of bis coumarin compounds using Fe3O4@SiO2@KIT-6.