Real-time Raman monitoring during coumarins synthesis via Pechmann condensation: A tool for controlling the preparation of pharmaceuticals

Raman spectra provide unique fingerprints for real-time analysis and monitoring chemical reactions and processes. The model reaction studied was the synthesis of coumarins, in particular, 7-hydroxy-4-methylcoumarin, via Pechmann condensation between resorcinol and ethyl acetoacetate in acid media and solvent-free conditions. The corresponding Hymecromone, 7-hydroxy-4-methylcoumarin or 7-hydroxy-4-methyl-2H-1-benzopyran-2-one, finds applications in synthesis of pharmaceuticals and insecticides. Raman spectroscopy was used to monitor the progress of this reaction and results were compared with off-line chromatographic analyses.