Microwave-Accelerated Facile Synthesis of pyrano[2,3-d]pyrimidine Derivatives via one-pot Strategy Executed by Agro-Waste Extract as a Greener Solvent Media

background: A variety of methods have been reported for the synthesis of pyrano[2,3- d]pyrimidines in the literature with some limitations, and generally used expensive catalysts, harmful solvent and prolonged reaction time. This paper describes an efficient and rapid multicomponent synthesis of pyrano[2,3-d]pyrimidine through condensation of aromatic aldehyde, malononitrile and barbituric acid catalysed by agro-waste solvent catalyst under microwave irradiation. The present method provides several added advantages such as being environmentally friendly, simple work-up, inexpensive, and shorter reaction time affording excellent yields. The synthesized compounds were confirmed by various spectroscopic analyses such as FT-IR, 1H- &13C-NMR and mass spectrometry. Objective: Develop an eco-friendly method for the synthesis of pyrano[2,3-d]pyrimidine derivatives. Methods: We have selected Water Extract of Lemon Fruit Shell ash extract solvent as a greener homogenous organo catalysts, and reaction is accelerated by microwave irradiation for the inexpensive synthesis of pyrano[2,3-d]pyrimidine derivatives. Results: The pyrano[2,3-d]pyrimidine derivatives are prepared using an agro-waste-based catalyst, which avoids the use of the external base, additives and solvent in multi-component reactions. Further, the rate of the reaction is accelerated by custom-made microwave irradiation. The use of microwave irradiation showed many advantages over conventional methods such as reaction required less time, more yield and fewer by-products. Further, the custom-made microwave oven has the advantage of no spillage of any organic reagent or solvent to the microwave oven walls, because the reaction vessel is connected to a reflux condenser and direct exposure is avoided. Conclusion: In conclusion, we have developed a simple, efficient, agro-waste-based catalytic approach for the synthesis pyrano[2,3-d]pyrimidine derivatives employing WELFSA as an efficient agro-waste-based catalyst under microwave conditions. The method is found to added advantages of less hazardous, eco-friendly, metal-free, chemical-free, short reaction time, simple workup and isolated product in good to excellent yields.