Abstract: Quinoxaline derivatives are a vital class of compounds, with 2,3-diphenylquinoxaline (DPQ) being particularly important for its applications in pharmacology and material science. However, traditional methods for its synthesis often rely on harsh conditions and environmentally harmful solvents, creating a need for greener alternatives. Addressing this challenge, we present a highly efficient, sustainable, and versatile one-pot method for synthesizing DPQ. This approach is centered on green chemistry principles, utilizing sodium hypochlorite (NaOCl·5H2O) as an inexpensive and eco-friendly oxidant.
The synthesis involves the oxidation of benzoin and its subsequent condensation with o-phenylenediamine within a benign ethanol/water solvent system. A key strength of this method is its remarkable adaptability; the reaction performs exceptionally well under several conditions, affording excellent yields of 96% with a photochemical reactor, 92% under standard reflux, and 83% in an electrochemical cell. The successful synthesis and high purity of the DPQ product were confirmed through comprehensive characterization, including 1H and 13C NMR spectroscopy.
To provide deeper mechanistic insight, the reaction was modeled using Density Functional Theory (DFT) calculations. These studies elucidated a favorable reaction pathway involving the formation of aminol and diaminol intermediates, identifying key energetic barriers for the proton transfer steps. By successfully integrating multiple green-by-design strategies with detailed computational validation, this research provides a robust and accessible blueprint for the clean production of valuable quinoxaline derivatives, championing the broader adoption of sustainable practices in modern organic synthesis.
