Polystyrene Resin Functionalized with a Piperazine: An Efficient and Reusable Catalyst for Multi-Component Synthesis of Polyfunctionalized 4H-Pyran Derivatives

摘要

Background: A novel one pot protocol has been developed to synthesize polyfunctionalized 4H-pyran derivatives directly from corresponding substituted aldehyde, malononitrile and β-keto ester using a recyclable polystyrene resin functionalized with a piperazine. The significant features of the present protocol are environmental acceptability, operational simplicity, shorter re-action time, high yields, and no chromatographic separation. The polymer catalyst was recovered and reused for four times without a noticeable decrease in the catalyst activity. Methods: All products were characterized using melting point, HRMS, ~1H and ~(13)C NMR techniques. Results: The various catalysts were compared with resin bound piperazine under optimized reaction conditions and it was found that resin bound piperazine gave better yield of desired product and it was a recyclable catalyst. Different reaction parameters such as solvent, temperature, time were studied to achieve optimal catalyst performance using resin bound piperazine as a catalytic system. Conclusion: We have demonstrated that resin bound piperazine is an excellent catalyst for the synthesis of 477-pyran derivatives. The product was isolated by simple filtration process. Also the catalyst was recovered, recycled and reused.