Synthesis of pyran-annulated heterocyclic system under catalyst-solvent-free conditions using solar energy as renewable energy source

The Knoevenagel-Michael cyclocondensation of aldehydes, malononitrile, and resorcinol through a three-condensation domino reaction can be utilized to generate 2-amino-4H-chromene scaffolds. This research establishes solar energy as an innovative sustainable energy source for the production of 2-amino-4H-chromene scaffolds under catalyst-solvent-free circumstances, with outstanding yields, time savings, and efficient use of resources. The range of yields is quite consistent (83–98%, with an average of 92.85%), and the range of reaction times is very rapid (2–5 min, with an average of 3 min). Additionally, it is worth noting that this method can accommodate a wide range of functional groups that donate or withdraw electrons, while still maintaining a rapid reaction rate and high yields. According to the findings, this technique is a productive one-step process under extremely effective and simple reaction conditions. This study establishes a fresh purpose for solar energy as a renewable energy source for the production of 2-amino-4H-chromene scaffolds under conditions without catalyst or solvent, with cost savings, simple experimental setup, a wide range of applicable substances, affordable, environmentally-friendly clean-up procedures without the need for tedious separation methods, and reduced organic waste for each chemical transformation, thus fulfilling certain aspects of sustainable and eco-friendly chemistry. This cyclization can be accomplished on a gram-scale using concentrated solar radiation with freely available, secure, and clean energy, demonstrating the practicality of the reaction for commercial purposes.