Microwave-Assisted Synthesis of Azacoumarin Fluorophores and the Fluorescence Characterization

By screening of reaction conditions and evaluation of its fluorescent properties, an environmentally sensitive fluorescent group, 8-aza-7-hydroxy-4-methylcoumarin, was synthesized in 70% yield using MgBr₂ as a Lewis acid under microwave irradiation. It has a high fluorescent quantum yield, is adequately soluble in water, and produces fluorescent emission in protic solvents and at neutral pH. Therefore, it could be useful in biosensors that are required to emit in hydrophilic environments such as cells.