In this study, we have presented a green and efficient protocol for the synthesis of diverse perimidine derivatives by employing deep eutectic solvents (DESs)-acting as reaction media and catalyst. Markedly, this method not only eliminates the need for hazardous solvents and expensive catalysts but also works under operationally mild and eco-friendly conditions while affording the anticipated products in good-to-excellent yields. Among the various tested eutectic mixtures, the combination of choline chloride (ChCl) with N, N'-dimethylurea (DMU) showed the best efficiency and reproducibility with aldehydic partners while reacting with 1,8-diaminonapthalene. On the other front, a melt of the DMU and L-(+)-tartaric acid afforded worthy results between ketones and 1,8-diaminonapthalene. Pleasingly, by using this DESs-mediated green methodology, we have assembled a variety of useful functionalized perimidines including four bioactive molecules (5b-e) and an anionic sensor (5a). Thus, the prepared perimidines were characterized by means of standard nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry. The melting points for all compounds besides the IR spectral data for the novel molecules have also been revealed. Additionally, the structures of two novel derivatives (9e-f) were unequivocally ascertained using single crystal X-ray diffraction analysis. Herewith, we have also reported the preliminary absorption (λmax at 234 nm) and emission properties of the synthesized compounds. Remarkably, this method was applied to a large-scale synthesis besides the catalytic efficiency was also checked thrice without much loss in the product yield-making this method attractive from the industrial perspective.
Khan et al. (Wed,) studied this question.