Monitoring of Catalyst-Free Microwave-Assisted MCR-Type Synthesis of 2-Amino-3-cyano-4 H -chromene Derivatives Using Raman Spectrometry

In order to prepare an array of beta-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.

Automated summary

A series of polyfunctionalized 4H-chromenes were synthesized via a microwave-assisted and catalyst-free three-component reaction for the potential precursors of heterocyclic systems with pharmaceutical interest. Raman spectroscopy was used to monitor the microwave-heated reactions, allowing for fast and efficient optimization of process parameters. The study revealed some limitations of this monitoring tool in terms of reaction medium homogeneity. Additionally, the use of bio-sourced and sustainable solvents was investigated, with ethanol found to be the most suitable for this synthesis.