Green Synthesis of Xanthenes: Utilizing Sulfonated Fructose as an Efficient and Eco-friendly Catalyst

The synthesis of xanthenes has garnered significant attention due to their extensive biological and therapeutic properties, including antibacterial, antiviral, and anti-inflammatory effects. Xanthenes are indispensable in organic synthesis and are also valued for their spectral properties as dyes in laser industries and fluorescent materials for detecting biological molecules. Despite various methods reported for xanthene synthesis, challenges such as low efficiency, lengthy reaction times, high catalyst requirements, and the use of hazardous organic solvents necessitate the development of more sustainable and efficient alternatives.

This study introduces sulfonated fructose as a novel, green catalyst for the condensation reactions of benzaldehyde, 2-naphthol, and dimedone to synthesize tetrahydrobenzo[a]xanthene-11-ones, and aldehyde and 2-naphthol to synthesize 14H-dibenzo[a,j]xanthenes. The sulfonation of fructose enhances its catalytic activity by increasing its acidity, stability, and selectivity, thus providing significant advantages over pure fructose. These include: 1. Higher Catalytic Activity: Enhanced acidity of sulfonated fructose reduces reaction times and increases yields. 2. Greater Stability: Increased stability of the catalyst leads to less degradation and a longer lifespan. 3. Compatibility with Green Chemistry: The use of less toxic and hazardous catalysts aligns with green chemistry principles, reducing environmental pollution. 4. Reduced Need for Toxic Solvents: Reactions can proceed under milder conditions using environmentally friendly solvents like water and ethanol. 5. Improved Selectivity: Sulfonic groups enhance the selectivity of reactions, resulting in fewer by-products and higher purity.

This innovative approach not only improves the efficiency and sustainability of xanthene synthesis but also demonstrates the economic and environmental benefits of using sulfonated fructose. The method offers straightforward operation, reduced costs, shorter reaction times, and easier purification, making it a valuable contribution to the field of green and sustainable chemistry.