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Monitoring of catalyst-free microwave-assisted MCR-type synthesis of 2-amino-3-cyano-4H-chromene derivatives using Raman spectrometry

In order to prepare an array of -cyanoenamine derivatives as potential precursors of heterocyclic systems with pharmaceutical interest, the synthesis of fifteen polyfunctionalized 4H-chromenes was realized via a microwave-assisted and catalyst-free three-component reaction. Microwave-heated reactions were monitored by Raman spectroscopy, enabling a fast and efficient setting of the process parameters. This study confirms that this monitoring tool may have some limitations linked to homogeneity of reaction medium. This work also investigates the use of some bio-sourced and sustainable solvents currently studied in many works. Ethanol remains the most suitable for this synthesis.